rjSfO^^
L
TECHNICAL METHODS OF
CHEMICAL ANALYSIS
U'^xi
TECHNICAL METHODS
OF
Chemical Analysis
Edited by GEORGE LUNGE, Ph.D., Dr.Ing.
EMERITUS PROFESSOR OF TECHNICAL CHEMISTRY, FEDERAL POLYTECHNIC SCHOOL, ZURICH
IN COLLABORATION WITH
E. ADAM.
P. AULICH.
F. BARXSTEIN.
E. BERL.
O. BOTTCHER.
A. BUJARD.
C. COUN'CLER.
K. DIETERICH.
K. DCMMLER.
A. EBERTZ.
A. EIBXER.
C. V. ECKEXBRECHER.
F. FISCHER.
P. FRANK.
H. FREUDENBBKQ.
E. GILDEMEISTER.
R. GXEHM.
O. GUTTMANN.
E. HASELHOFF.
W. HERZBERG.
D. HOLDE.
H. KOHLER.
W. KLAPPROTH.
P. KREILIXG.
K. B. LEHMAXN,
J. LEWKOWITSCH.
C. J. LIXTXER.
E. O. V. LIPPMAXX.
E. MARCKWALD.
J. MESSXER.
J. PASSLER.
O. PFEIFFER.
O. PUFAHL.
O. SCHLUTTIG.
C. SCHOGH.
G. SCHULE.
L. TIETJEX3.
K. WINDISCH.
L. W. WIXKLER.
ENGLISH TRANSLATION
FROM THE LATEST GERMAN EDITION, ADAPTED TO ENGLISH
CONDITIONS OF MANUFACTURE
EDITED BY
CHARLES ALEXANDER KEANE, D.Sc, Ph.D.
PRINCIPAL AND HEAD OF THE CHEMISTRY DEPARTMENT
THE SIR JOHN CASS TECHNICAL INSTITUTE, LONDON
IX COLLABORATION WITH
W. BACOX.
T. L. BAILEY.
C. O. BAXXISTER.
E. J. BEVAX.
W. BURTOX.
J. C. CAIX.
W. A. GASPARI.
E. G. CLAYTON.
H. G. COLMAX.
J. T. COXROY.
C. F. CROSS.
W. A. DAVIS.
L. EYXOX.
G. J. FOWLER.
A. G. GREEX.
O. GUTTMAXX.
A. D. HALL.
J. HUBXER.
G. CECIL JOXES.
W. J. LAMBERT.
J. LEWKOWITSCH.
A. R. LIXG.
C. A. MITCHELL.
G. W. MOXIER-WILLIAMS.
F. B. POWER.
H. R. PROCTER.
H. J. L. RAWLINS.
A. RULE.
W. F. REID.
P. SCHIDROWITZ.
A. SMETHAM.
W. THOMASOX.
VOLUME lll.-PART I.
3 ^J^ b
GURNEY AND JACKSON ^
33 PATERNOSTER ROW, LONDON
1914
I
TP
6/
■
r
PREFACE
The sections comprised in this third and concluding volume of the
English edition are included in the third and fourth volumes of
the last German edition, published in 1910-11.
The sections on "Brewing Materials and Beer" and on " Vinegar"
have been entirely re-written for the English edition, as the processes
of manufacture and associated methods of analysis that obtain in
this country are so entirely different from those of Germany ; and the
sections on " Spirits " and on " Brandy and Liqueurs " of the German
edition have been combined into one section under the title of
"Alcohol, Potable Spirits, and Liqueurs," and have been fully revised,
so as to provide a connected account of the analytical methods required
by the English conditions of manufacture and of legislative control.
All the remaining sections have been submitted to English experts
for revision. The contents of the volume have thus been brought
thoroughly up to date by the addition of all relevant matter of
importance since the issue of the last German edition.
Also, the order of the sections in the German edition has been
altered, with the object of securing a somewhat better sequence of the
subject matter.
With the exception of those cases in which empirical factors are
employed in technical work, all the numerical data are calculated from
the table of atomic weights for 1914, issued b}' the International Com-
mittee, with 0=16 as the basis. As in Volumes I. and II., the
numerical data for gases, and for the weights of substances to be
taken for analysis so as to correspond to definite volumes of gases,
viii PREFACE
are calculated from the real litre weights according to the most reliable
determinations, not from the calculated values. Also, all temperatures
arc given in Centigrade degrees, except where otherwise stated.
The Editor desires to record his thanks to Mr J. S. S. Brame,
Lecturer on Fuel, The Sir John Cass Technical Institute, for very
kindly reading the proofs of the sections on "Mineral Oils" and
" Lubricating Oils," the MSS. of which had been revised by the late
Dr Lewkowitsch ; to the Director of Navy Contracts, for a copy of the
Admiralty specification governing the supplies of manufactured rubber;
and to Mr L. Archbutt, for permission to reproduce the illustration of his
vaporimeter. Also to Messrs Baird & Tatlock, Messrs A. D. Cillard
(Paris), Messrs Constable & Co., and Messrs C. Griffin & Co., for the
loan of and permission to reproduce blocks ; and to Messrs Macmillan
& Co., for permission to reproduce a block from their publication,
India-rubber Laboratory Practice^ by W. A. Caspari.
CHARLES A. KEANE.
London,////;/ 1914.
LIST OF CONTRIBUTORS TO THE GERMAN
EDITION, AND OF REVISERS AND
AUTHORS OF THE ENGLISH TRANS-
LATION IN VOL. III.
Mineral Oils.
By Prof. D. Holde, Lichterfelde.
Revised by the late J. Lewkowitsch, Ph.D., M.A.
Lubricants.
By Prof. D, HOLDE, Lichterfelde.
Revised by the late J. Lewkowitsch, Ph.D., M.A.
Oils, Pats, and "Waxes.
By the late J. Lewkowitsch, Ph.D., M.A.
Revised by The Author.
Special Methods of Analysis Employed in the Oil and Pat Industries.
By the late J. Lewkowitsch, Ph.D., M.A.
Revised by The Author.
Resins, Balsams, and Qum-Resins.
By K. Dieterich, Ph.D., Dresden.
Revised by the late J. Lewkowitsch, Ph.D., M.A.
Drugs and Galenical Preparations.
By K. Dieterich, Ph.D., Dresden.
i?tfz//V<f^^/ F. B. Power., Ph.D., LL.D.
Essential Oils.
By E. Gildemeister, Ph.D., Leipzig.
Revised by F. B. POWER, Ph.D., LL.D.
Tartaric Acid.
By W. Klapproth, Dr.Ing., Nieder-Ingelheim.
Revised by W. A. Davis, B.Sc.
Citric Acid.
By W. Klapproth, Dr.Ing., Nieder-Ingelheim.
Revised by W. A. Davis, B.Sc.
Organic Preparations.
By J. Messner, Ph.D., Darmstadt.
Revised by Charles A. Keane, D.Sc, Ph.D.
X LIST OF CONTRIBUTORS
India-rubber and Rubber Goods.
By F. Frank, Ph.D., and E. Marckwald, Ph.D., Berlin.
Revised by W. .X. Caspari, Ph.D., H.Sc.
Vegetable Tanning Materials.
By the late Prof. C. Councler, Munden.
Revised by Prof. H. R. Procter, M.Sc.
Leather.
By J. Paessler, Ph.D., Freiberg.
Revised by Prof. H. R. PROCTER, M.Sc.
Ink.
By O. SCHLUTTIG, Dresden.
Revised by C. \. Mitchell, B.A.
Sugar.
By Prof. E. O. VON Lippmann, Halle.
Revised by P^KT'AXi-R. R. Ling and Lewis Eynon.
Starch and Dextrin.
By Prof. C. voN ECKENBRECHER, Berlin.
Revised by hKlWMK R. LiNG.
Alcohol, Potable Spirits, and Liqueurs.
By A. EiiERTZ, Ph.D., Hohenheim, and G. SCHULE, Ph.D., Strassburg.
Revised by G. W. Monier-Williams, M.A., Ph.D.
Vinegar.
Re-written by G. Cecil Jones, A.C.G.I.
Corresponding section in German Edition by G. Schule, Ph.D., Strassburg.
Wine.
By Prof. K. WiNDISCH, Hohenheim.
Revised by P. SCHIDROWITZ, Ph.D.
Brew^ing Materials and Beer.
Re-writttn by ARTHUR R. LiNG and G. CECIL JONES, A.C.G.L
Corresponding section in German Edition by Prof. C. J. LiNTNER, Munich.
Pai>er.
By Prof. W. Herzberg, Lichterfelde.
Revised by C. F. CROSS, B.Sc, E. J. Bevan, and W. Bacon, B.Sc
Textile Fibres.
By Prof. R. Gnehm, Zurich.
Revised by J. HiJBNER, M.Sc. (Tech.)
Inorganic Colours.
By Prof. A. ElBNER, Munich.
Revised by H. J. L. Rawlins and A. Rule, D.Sc, Ph.D.
LIST OF ABBREVIATED TITLES OF JOURNALS
Journals.
quee a I'lndustrie, k
a la Biologie
Acetylene
American Chemical Journal
American Journal of Science
Analyst .....
Annalen der Chemie .
Annalen der Physik .
Annales de Chimie analytique appl
TAgriculture, k la Pharmacie et
Annales de Chimie et de Physik
Annales des Falsifications .
Archiv der Pharmacie
Atti della Reale Accademia dei Lincei
Berg und Huttenmannische Zeitung .
Berichte der deutschen chemischen Gesellschaft
Biedermann's Zentralblatt fiir Agricultur Chemie
Bollettino chimico farmaceutico .
Brewer's Journal
British and Colonial Druggist .
Bulletin de rAssociation Belgique des Chimistes
Bulletin de I'Association chiraique de Sucre et de Distillerie
Bulletin de la Societe chimique de Belgique
Bulletin de la Societe chimique de Paris .
Bulletin de la Societe Industrielle du Nord de la France
Bulletin de la Societe Industrielle de Mulhouse
Chemical News
Chemical Trade Journal
Chemiker Zeitung
Chemiker Zeitung Repertorium . . . ,
Chemische Industrie ......
Chemische Revue iiber die Fett- und Harz-Industrie
Chemisches Zentralblatt ......
Chemist and Druggist ......
Comptes rendus hebdomadaires des seances de I'Academie
des sciences .....
Der Gerber
Deutsche Gerber Zeitung ....
Die landwirthschaftlichen Versuchs-Stationen
Dingler's polytechnisches Journal
Electrician ......
Electrochemical and Metallurgical Industry
Electrotechnische Zeitschrift
Engineer
Abbreviations.
Acetylene
Amer. Chem. J.
Amer. J. Sci.
Analyst
Annalen
Ann. Physik
Ann. Chim. anal.
Ann. Chim. Phys.
Ann. Falsific.
Arch. Pharra.
Atti R. Accad. Lincei
Berg u. Hiitten. Zeit.
Ber.
Biedermann's Zentr.
Boll. chim. farm.
Brewer's J.
Brit, and Col. Drug.
Bull. Assoc. Belg. des Chim.
Bull. Assoc. Chim. Sucr.
Bull. Soc. Chim. Belg.
Bull. Soc. Chim.
Bull. Soc. Ind. Nord
Bull. Soc. Ind. Mulhouse
Chem. News
Chem. Trade J.
Chem. Zeit.
Chem. Zeit. Rep.
Chem. Ind.
Chem. Rev. Fett-Ind.
Chem. Zentr.
Chem. and Drug.
Comptes rend.
Gerber
Gerber Zeit.
Landw. Versuchs-Stat.
Dingl. polyt. J.
Electrician
Electrochem. Ind.
Electrotech. Zeitsch.
Engineer
Xll
LIST OF ABBREVIATED TITLES OF JOURNALS
Journals.
1". I ■ £J . • • • • • •
Ei: - and Mining Journal
Farben-Zciiung
Farber-Zeitung
P"ischer's Jahresbericht
Gazzetta Chimica Italiana
Gummi-Zeiiung ......
I ndia-ruilicr Journal .....
Industrie Blatt
Intern.iiional Sugar Journrd ....
Jahresbericht der chemischen Technologic
Jahresbericht der Pharmazie ....
Jahresbericht fur Chemie
Journal of Analytical and Applied Chemistry .
Journal de Pharmacie et de Chimie .
Journal fiir Gasbeleuchtung und Wasserversorgung
Journal fiir praktische Chemie ....
Journal of Agricultural Science ....
Journal of Gas Lighting
Journal of Industrial and Engineering Chemistry
Journal of Physical Chemistry ....
Journal of the American Chemical Society
Journal of the Chemical Society
Journal of the Chemical Society, Abstracts
Journal of the Chemical, Metallurgical, and Mining
Society of South Africa
Journal of the Franklin Institute ....
Journal of the Institute of Brewing ....
Journal of the Institution of Mechanical Engineers .
Journal of the Institute of Metals ....
Journal of the Iron and Steel Institute
Journal of the Physical and Chemical Society of Russia
Journal of the Ro3'al Society of Arts ....
Journal of the Society of Chemical Industry
Journal of the Society of Dyers and Colourists .
Koninklijke Akademie van Wetenschappen te Amsterdam
Proceedings (English Edition) .
Leather Trades Review
Le Stazioni sperimentali agrarie Italiana
Mittheilungen aus dem kiJniglichen Materialpriifungsamt
zu Gross-Lichterfelde West
.Mittheilungen aus der Zentralstelle fiir wissenschaftlich
technische Untersuchungen ....
Mittheilungen dcs lechnischen Gewerbemuseums in Wien
Monatshefte fiir Chemie der kaiserlichen Akademie der
Wisscnschaften, Wien
Monatsschrift fiir Textil-Industrie
Monitcur Scicniifique
Oesterrcichische Chemiker Zeitung
Oesterreichisch-Unpar Zeitschrift fiir
Landwirthschaft .
Paper and Pulp ....
Papier-Zeitung ....
Petroleum Review
Zuckerindustrie und
AnBREVIATIONS.
Engineering
Eng. and .Min. J.
Farben-Zeit.
Farber-Zeit.
Fischer's Jahresber.
Gazz, Chim. Ital.
Gummi-Zeit.
India-rubber J,
Ind. Bl.
Int. Sugar J.
Jahresber, d. chem. Techn.
Jahresber. d. Pharm.
Jahresber. f. Chem.
J. Anal, and Applied Chem.
J. Pharm. Chim.
J. Gasbeleucht.
J. prakt. Chem.
J. Agric. Sci.
J. Gas Lighting
J. Ind. Eng. Chem.
J. Phys. Chem.
J. Amer. Chem. Soc.
J. Chem. Soc.
J. Chem. Soc. Abstr.
J. Chem. Met. Soc, S. .Africa
J. Franklin Inst.
J. Inst. Brewing
J. Inst. Mech. Eng.
J. Inst. Metals
J. Iron and Steel Inst.
J. Russ. Phys. Chem. Soc
J. Soc. Arts
J. Soc. Chem. Ind.
j. Soc. Dyers and Col.
Proc K. Akad. Wetensch. Am-
sterdam
Leather Tr. Rev.
Staz. speriment. agr. Ital.
Mitt. k. .Materialpriif.
Mitt. Zentralst. Wiss.-tech.
Unters.
Mitt, techn. Gew. .Museums
Monatsh.
Monatsschrift f. Te.\t.-Ind.
Monit. Scient,
Oesterr. Chem. Zeiu
Oesterr.-Ungar Zeitschr.
Paper and Pulp
Papier-Zeil.
Petrol. Rev.
LIST OF ABBREVIATED TITLES OF JOURNALS
XII 1
Journals.
Pharmaceutical Journal
Pharmaceutical Review
Pharmazeutisch Weekblad
Pharmazeutische Zeitung .
Pharmazeutische Zentralhalle
Pharmazeutisches Zentralblatt
Philosophical Magazine and Journal of Science
Philosophical Transactions of the Royal Society .
Proceedings of the American Academy
Proceedings of the American Electrochemical Society
Proceedingsof the American Institute of Mining Engineers
and also Bulletin
Proceedings of the Faraday Society ....
Proceedings of the Institution of Civil Engineers
Proceedings of the Institution of Mining and Metallurgy
Proceedings of the Royal Society
Revue Generale des Matiferes Colorantes
Revue internationale des Falsifications
Receuil des travaux chlmiques des Pays-Bas at de 1
Belgique .
Scientific American .
Stahl und Eisen
Tonindustrie Zeitung
Transactions of the Institute of Mining and Metallurgy
United States Consular Reports
West Indian Bulletin . . .
Wochenschrift fiir Brauerei
Zeitschrift der analytischen Chemie .
Zeitschrift der anorganischen Chemie
Zeitschrift des Vereins der deutschen Zucker-Industrie
Zeitschrift des Vereins deutscher Ingenieure , ,
Zeitschrift fiir angewandte Chemie ....
Zeitschrift fiir chemische Apparatenkunde
Zeitschrift fiir das gesammte Brauwesen .
Zeitschrift fiir das landwirtschaftliche Versuchswesen in
Osterreich ......
Zeitschrift fiir Elektrochemie .
Zeitschrift fiir Farben Industrie .
Zeitschrift fiir Farben- und Textil-Chemie
Zeitschrift fiir offentliche Chemie
Zeitschrift fiir physikalische Chemie ....
Zeitschrift fiir Spiritusindustrie .....
Zeitschrift fiir Untersuchung der Nahrungs- und Genuss
mittel ........
Zeitschrift fiir Zuckerindustrie in Bohmen . . .
Abbreviations.
Pharm. J.
Pharm. Rev.
Pharm. Weekblad
Pharm. Zeit.
Pharm. Zentralh.
Pharm. Zentr.
Phil. Mag,
Phil. Trans.
Proc. Amer. Acad.
Proc. Amer. Electrochem. Soc.
Proc. Amer. Inst. Min. Eng. ;
Bull. Amer. Inst. Min. Eng.
Proc. Faraday Soc.
Proc. Inst. Civ. Eng.
Proc. Inst. Min. and Met.
Roy. Soc. Proc
Rev. Gen. Mat. Col.
Rev. intern. Falsif.
Rec. trav. chim.
Scient. Amer.
Stahl u. Eisen
Tonindustrie Zeit.
Trans. Inst. Min. and Met.
U.S. Cons. Reps.
West Ind. Bull.
Woch. f. Brau.
Z. anal. Chem.
Z. anorg. Chem.
Z. Ver. deut. Zuckerind.
Z. Verein. deutsch. Ingen.
Z. angew. Chem.
Z. fiir chem. Apparatenkunde
Z. ges. Brauw.
Zeitschr. f. landw. Versuchswesen,
Osterr.
Z. Elektrochem.
Z. Farb. Ind.
Z. Farb.- u. Text.-Chem.
Z. offentl. Chem.
Z. physik. Chem.
Z. Spiritusind.
Z. Unters. Nahr. u. Genussm,
Z. Zuckerind. Bohm.
CONTENTS
Preface ...........
List of Contributors to the German Edition, and of Revisers and
Authors of the English Translation ......
Abbreviated Titles of Journals .......
PAOE
vii
IX
xi
PART I
Mineral Oils.
A. Crude Petroleum . . . . .
I. Chemical Composition . . ' .
II. Specific Gravity and Coefficient of
Expansion . . . . .
in. Determination of Contained Water
IV. Determination of Mechanical Im-
purities
V. Yield of Naphtha, Burning Oil,
Lubricating Oil, etc.
VI. Flashing Point
VII. Determination of Asphalt .
VIII. Paraffin Wax .
IX. Specific Heat
X. Latent Heat of Evaporation o
Petroleum Fractions
B. Naphtha
I. Specific Gravity ...
II. Evaporation Test ...
III. Fractional Distillation .
IV. Flashing Point
V. Risk of Explosion .
VI. Heat of Combustion of Naphth;
(Petrol) ....
VII. Aromatic Hydrocarbons
VIII. Oil of Turpentine
IX. Degree of Purification .
X. Solubility in Absolute Alcohol
XI. Petroleum Spirit (Naphtha or
"Normal Benzine") .
XII. Petroleum Spirit for Varnishes
and Oil of Turpentine Substitutes
XV
PAGE
I
2
6
8
9
II
13
U
i6
17
17
17
i8
19
20
20
21
21
21
21
22
C. Burning Oil
I. Colour —
1. Wilson's colorimeter
2. Stammer's colorimeter
II. Specific Gravity
III. Viscosity
IV. Solidifying Point .
V. Flashing Point
The Abel petroleum test apparatus .
The Abel-Pensky petroleum test
apparatus . . . . .
Other apparatus for testing the flash-
ing point
VI. Ignition or "Fire Test"
VII. Fractional Distillation .
VIII. Degree of Purification
1. Sulphur conipounds
2. The acid test . . . .
3. Determination of acidity
4. Salts of naphthenic and sulphonic
acids . . . . .
5. Inorganic residue (ash)
6. The " breaking " of petroleum
IX. Unsaturated Hydrocarbons .
X. Burning Quality ....
XI. Illuminating Power
XII. Solubility in Absolute Alcohol
XIII. Determination of the Origin of a
Petroleum .....
D. Gas Oils from Crude Petroleum .
E. Transformer Oils ....
F. Liquid Fuel for Internal Combustion
Engines
PAOB
23
24
25
27
28
28
28
29
33
35
36
36
36
36
39
39
39
40
40
40
40
41
42
42
43
43
44
XVI
CONTENTS
PAOK
G.fuilOih(^M^isut,Astatki'). -45
H. Dust-Laying Oils . . ■ 46
I. Paraffin Wax 46
K . T:ir and Pitch Rfsuiues (Petroleum Tar,
Asphalt, and Pitch) . . . -47
L. By-products of the Petroleum Industry . 50
By-products of the refining operations . 50
1. AciJ tar 5°
2. Pitch 50
3. Waste acid 5°
M. Products of the Shale and Lignite In-
dustries . . ■ . . •5''
Experimental distillation test . • 5'
I. Shale Oil 52
II. Lignite or Brown Coal Tar . 53
III. Montan Wax . . . .54
N. Osokerite and Ceresin . . . -55
O. Ichthyol 56
P, Peat Tar 57
Literature 57
Lubricants.
The Substances used as lubricants . 58
A. Mineral Oils 60
Physical Tests 60
I. Appearance . . . . .60
(rt) Colour 60
{U) Consistency . . . .61
(f) Mechanical impurities . . 61
II. Specific Gravity . . . .61
{a) Determination of the specific
gravity by means of the hy-
drometer . . . .61
(/') Determination of the specific
gravity by pyknometers . 62
III. Expansibility . . . .63
IV. Viscosity 65
Redwood's viscometer . . .66
Sayboll's viscometer . . .68
Engler's viscometer . . .68
Viscosity of mixtures of oils . . 69
Absolute viscosity . . . .69
V. Behaviour of Oils at Low
Temperatures . . . .70
Quantitative comparison of fluidi-
ties. The freezing point or cold
test 72
VI. Volatility and Inflammability . 74
(;) Evaporation or volatility test . 74
1. .\rchbutt's vaporimeter . , 74
2. Schreil)cr's apparatus . . 76
PACK
A. Mineral Oils. — Physical Tests — Contd.
VI. Volatility and Inflammability —
Continued.
ij!) The flashing point
The " open " test
The Pensky-Martens apparatus
Gray's apparatus
(() The ignition point
VII. Optical Tests .
Optical activity
Refractiviiy .
Chemical Tests
VIII. Acidity and Free Alkali .
IX. Rosin in Lubricating Oils .
X. Liability to " Gum " or " Resinifi
cation " of Lubricants
XI. Formolite Reaction (Xastjukoff'
Ten)
XII. Behaviour towards Metals
XIII. Moisture
XIV. Mineral Ash .
XV. Presence of Soap
XVI. Admixtures of Fatty Oils
XVII. Rosin Oils and Tar Oils
XVIH. India-rubber
XIX. Deblooming Agents and Per
fumes ....
XX. Water-soluble Substances
XXI. Suspended Matter .
XXII. Asphalt and Paraffin in Solu
tion .....
XXIII. Changes Lubricating Oils
undergo in Use . . . .96
Recovered oils . . . -96
Condenser water . . . -97
B. Fatty Oils 97
C. Mixtures 0/ Mineral and Fatty Oils . 97
D. Vaseline . . . . . -97
E. Solid Lubricants 98
I. Appearance, etc. . . . -99
II. Liquefying and Dropping Points 99
III. Qualitative Examination . . 100
IV. Quantitative Determinations . 100
('/) Free acid . . . . ico
(_h) Soap 100
(() Neutral fats (glycerides) and
unsaponiliable matter . .101
(</) Water 10 1
(<■) Glycerol loi
(^/') Nitronaphthalene and Nitro-
benzene ..... lOI
(jf) Free lime .... loi
(//) Impurities and adulterants . loi
CONTENTS
xvii
F". Water-soluble Lubricants
The solidifying point
The emulsif) ing properties or
bility in water
Analytical examination
{a) Volatile matter
(3) Free organic acid .
(c) Neutral fatty matter
(jf) Soap
Literature ....
solu
PAGE
102
102
102
I02
I02
I03
103
103
104
Oils, Fats, and Waxes.
Classification of oils, fats, and waxes . 105
The examination of oils, fats, and waxes . 106
A. Physical Methods .... 106
I. Determination of the Specific
Gravity ..... 107
II. Determination of the Melting
Point and the Solidifying Point. 108
III. Determination of the Refractive
Index ..... 107
The butyro-refractometer . .110
IV. Determination of the Viscosity . 113
V. Determination of the Solubility . 113
VI. Optical Rotation . . -US
B. Chemical Methods . . . . 1 14
I. Quantitative methods . . .114
(a) Characteristics . . .114
1. Determination of the saponi-
fication value . . .114
2. Determination of the iodine
value . . . . .116
3. Determination of the Reichert
(Reichert-Meissl or Reich-
ert-Wollny) value . .119
Determination of the acetyl-value . 120
(3) Variables . . . .122
1. Determination of the acid
value ..... 122
2. Determination of the content
of glycerol . . . .123
3. Determination of the unsa-
ponifiable matter . . 124
II. Qualitative Methods . . .125
1. Oxygen absorption . . . 126
2. Bromide test .... 127
3. Colour reactions . . . 129
C. Examination of the Fatty Acids . 130
1. Determination of the neutralisa-
tion value and the mean
molecular weight . . -131
2. Determination of lactones (An-
hydrides) .... 132
The examination of oils, fats, and
waxes — Continued.
C. Examination of the Fatty Acids —
Continued.
3. Determination of insoluble fatty
acids . . . . .132
4. Determination of soluble fatty
acids . . . . -133
5. Separation of saturated from
unsaturated fatty acids . .134
6. Examination of the saturated
fatty acids . . . .136
Arachidic acid . . . .136
Stearic acid . . . .136
7. Determination of oleic, linolic,
linolenic and clupanodonic
acids 137
8. Determination of oxidised fatty
acids 139
D. Examination of Unsaponifiable
Matter I39
1. The examination of unsaponifiable
substances which are naturally
present I39
(a) In oils and fats . • .139
((5) In waxes .... 141
2. The detection and determination
of admixed unsaponifiable sub-
stances • . . . • 142
Literature 145
Data for the identification of vegetable
oils 146
Data for the identification of animal oils . 148
Data for the identification of vegetable
and animal fats . . . .150
Data for the identification of waxes . .152
Special Methods of Analysis employed
in the Oil and Fat Industries.
A. Oil Seed, Oil Cakes, Crude Fats, etc. .154
B. Edible Oils and Fats . . . .155
1. Butter 155
2. Margarine 159
3. Lard, artificial lard, lard substitutes . 159
4. Chocolate fats, cocoa-butter sub-
stitutes . . . . • 159
C. Wool Oils 160
D. Lithographic Varnishes, Polymerised
Linseed Oils . . . . . 161
E. ^'Boiled" Linseed Oil, Linseed Oil
Varnish, Varnish Oils . . .162
1. Linseed oil 162
2. Siccatives 163
b
XVlll
CONTENTS
PAGE
F. Ltnsud Oil Patnts and I'arntshfs . 1 66
G. Oxuhsed Oils 169
1. Oxidised oils obtained from semi-
drying vegetable oils, marine animal
oils, and liquid waxes . . . 169
2. Oxidised oils obtained from drying
oils 169
H. Vulcanise J Oils, In Jia-rubber Substitutes 170
J. Sulphonattd Oils, Turkey Red Oils . 1 70
K. Tlie Candle Industry . . . .173
1. Stearine candles . . '73
(<j) Testing of the raw material . 174
(/') Testing of intermediate and
5nished products . . .176
2. Paraffin candles . . . '179
3. Spermaceti candles .... 1S3
4. Wax candles, beeswax c;indles. . 183
5. Ceresin 187
L. Soap 188
Soda soaps 18S
Potash soaps (soft soap) . . .189
Raw materials ..... 190
{ii) Determination of the fatty
matter and total alkali . . 191
{b") Determination of combined alkali,
free caustic alkali, and alkaline
salts. Free fatty acids . .193
(f) Determination of water . -194
{d) Examination of fatty matter
("soap stock ") . . . . 194
1. Rosin acids .... 195
2. Neutral fat . . . .196
3. Unsaponifiable matter . . 196
{e) Substances insoluble in alcohol . 197
1. Water-soluble substances . .197
2. Substances insoluble in water . 197
3. Organic matter . . -197
(/) Other substances which occur in
soaps ..... 198
1. Glycerol 198
2. Sugar (saccharose) . . . 198
3. Carbolic acid . . . -199
Metallic soaps . . . . .199
M. Glycerin ...... 200
I. Crude glycerin .... 200
(rt) Crude saponification glycerin . 2CO
(/') Crude distillation glycerin . . 201
(c) Crude soap-lye glycerin ; crude
soap glycerin .... 202
a. Distillation glycerin ; dynamite
glycerin ..... 202
3. Chemically pure glycerin . . 206
Literature 209
PAOB
Resins, Balsams, and Gum Resins.
A. Methods of .\n.ilysis . . . .211
(a) The acid value . . . .212
1. By direct titration . . .212
2. By indirect titration . . .212
3. By estimating the acid value of
the volatile acids . . •213
(/') The saponification value . .213
1. Determination in the hot solution. 213
2. Determination in the cold solution 214
(<:) The ester value . . . .214
(./) Lois at 100° (moisture). . .214
(j) Ash 214
(/) The proportion soluble in alcohol. 215
Cc) The proportion insoluble in alcohol 215
(/•) Specific gravity at 15° . . . 215
(;) Determination of thecinnamein and
resin esters in Peru balsam . -Sis
{k") The acetyl, carbonyl, and methyl
values 3i6
(/) Examination of the resin acids . 216
0") Qualitative reactions . . .216
B. Characteristic Values and Standards
of Quality
I. Balsams
Copaiba
II. Resins
Amber
Benzoin
Colophony
Copal (Zanzibar)
Dammar .
Guaiacum
Mastic (Levant)
Pine resin
Sandarac .
Storax
Turpentine
in. Gum Resits
Ammoniacum .
^ Galbanum
Myrrh
Olibanum
Literature
217
217
217
218
?i8
218
218
219
219
219
220
220
220
221
221
221
221
222
222
222
222
Drugs and Galenical Preparations.
Drugs ...... 224
Gambir
Pegu catechu
Ergot
Isinglass .
Opium
Vegetable drugs
224
225
225
226
230
232
CONTENTS
xix
PAGE
PAOE
A. Drugs. — Vegetable Drugs — Cojitd.
B. Galenical Preparations
. 252
I. Barks
232
Papers
• 253
Cascara sagrada .
232
Test papers .
. 253
Cascaiilla ....
232
Mustard paper and mustard lint . 253
Cinchona ....
233
Plasters .
. 254
Cinnamon and cassia
235
Liquid or fluid extracts
• 255
Condurango ....
235
Liquid extract of kola
. 255
Frangula ....
235
Thick extracts and dry extracts . 256
Tinctures .
• 257
II. Bulbs
236
Ointments
. 257
Squill
236
Mercurial ointment
. 257
III. Flowers ....
. 236
Literature
. 258
Chamomile flowers
236
Red poppy petals ....
237
Essential Oils
,
Rose petals ....
237
Determination of the physical constants . 260
IV. Fruits ....
237
Specific gravity .
. 260
Buckthorn berries .
237
Optical rotatory power
. 260
Capsicum, Spanish pepper, cayenne
Solubility .
. 260
pepper ....
237
Congealing point
. 260
Elder berries
238
Fractional distillation .
. 261
Fennel
238
Chemical methods of examination . . 262
Juniper berries
238
Determination of esters by sa
ponification 262
Parsley fruit .
238
Determination of free alcohols by acety-
Poppy capsules
239
lation .
. 263
V. Herbs
. 239
Aldehyde determination by
the bisul-
Carduus benedictus
239
phite method
. 264
Linaria .....
239
Determination of aldehydes and ketones
Marjoram ....
239
with neutral sulphite
. 265
Milfoil or yarrow .
239
Determination of phenols
. 266
VI. Leaves ....
239
Detection of alcohol
. 266
Belladonna ....
240
Detection of fatty oil .
. 267
Coca
241
Detection of mineral oil
. 267
Digitalis ....
242
Detection of turpentine oil
. 268
Menyanthes ....
Senna
244
244
Constants and properties of some essential
oils of commercial and industrial im-
Strammonium
244
portance .
. 208
Uva ursi ....
244
Anise oil
Bay oil
. 268
. 269
VII. Rhizomes
245
Bergamot oil
. 269
Galangal ....
245
Bitter almond oil
. 269
Ginger .....
245
Caraway oil
. 270
Hydrastis ....
245
Cassia oil
. 271
Male fern ....
246
Cinnamon oil
. 271
Rhubarb ....
246
Citronella oil
. 271
VIII. Roots ....
247
Clove oil
. 271
Belladonna ....
247
Eucalyptus oil
. 273
Gentian ....
248
Fennel oil .
. 274
Ipecacuanha ....
248
Geranium oil
. 274
Liquorice ....
249
Lavender oil
. 274
Rhatany ....
249
Lemon oil .
• 274
Senega
250
Lemon-grass oil
• 274
Valerian ....
250
Linaloe oil .
• 275
IX. Seeds ....
250
Mustard oil .
. 275
Kola seeds, kola nuts .
250
Nutmeg oil .
. 276
Black mustard seed
252
Orange oil .
. 276
XX
CONTENTS
Constants and properties
of some essential
oils of commercial and industrial im-
po rtan ce — Continued.
Orange flower oil
. . 276
Palmarosa oil
. 276
Patchouli oil
. 276
Peppermint oil
. 276
Rose oil
• 277
Rosemary oil
• 277
Sandalwood oil .
• »77
Sassafras oil
• 277
Spike oil
. 278
Star-anise oil
. 278
Thyme oil .
. 278
Turpentine oil
. 278
Literature
. 280
Tartaric Acid.
I. Raw Materials .
. 282
I. Estimation of acid potassium ta
rtrate 283
2. Estimation of the total tartaric
acid . 284
The "Goldenberg Method, 189
8" . 285
The "Goldenberg Method, 190
7" . 287
3. Other estimations .
. 289
II. Control of Working Conditions
. 290
Calcium tartrate .
. 291
Tartaric acid liquors
. 291
Old liquors ....
. 291
Waste products. Lees residue
and
gypsum
. 291
Washings or "runnings "
. 291
Free sulphuric acid in liquors
. 291
Harmful impurities (" Impurity Rr
itio") 292
III. Finished Products .
. 292
Tartaric acid
. 292
Rocheile salt
• 295
Tartar emetic
• 295
Neutral potassium tartrate, borax t
artar,
iron tartrate .
• 295
Literature
.
• 295
Citric Acid.
I. Raw materials . . • . . 296
Calcium citrate ..... 297
Lime juice, lemon juice, and factory
citric acid liquors .... 298
II. Control of Working Conditions. . 299
III. Final Products .... 300
Literature .....
Organic Preparations.
Acetaldehyde ....
Aceianilide ....
Acetic acid ....
300
301
303
304
f AGK
Acetone
308
Acetyl salicylic acid (aspirin) .
310
Amyl acetate
311
Amyl nitrite .....
312
Apomorphine hydrochloride
313
-Atropine ......
315
Atropine sulphate ....
315
Benzaldehyde .....
316
Benzoic acid
319
Bromoform .....
• 321
Caffeine
322
Caffeine-sodium salicylate
322
CafiFeine-sodium benzoate
323
Camphor
323
Carbon bisulphide ....
325
Carbon tetrachloride
326
Casein •
327
Catechol (pyrocatechin) . . . .
329
Chloral hydrate . . . . .
330
Chloroform .....
332
Cinnamic acid
336
Citric acid
337
Cocaine hydrochloride
338
Coumarin .....
340
Dextrose
341
Diethyl barbituric acid (veronal)
• 343
Veronal-sodium ....
344
Ethyl acetate
344
Ethyl alcohol
345
Ethyl bromide
347
Ethyl butyraie ....
348
Ethyl ether
350
Formaldehyde .....
351
Formic acid
352
Gallic acid
353
Gelatin ......
355
Guaiacol ......
356
Guaiacol carbonate ....
356
Hexamethylenetetramine .
357
Hydroquinone (quinol) .
358
Iodoform
359
Lactic acid .....
360
Methyl alcohol (wood spirit) .
362
Morphine
365
Morphine hydrochloride .
365
Codeine (methyl morphine) .
367
Dionine (ethyl morphine hydrochloride
) 367
a-Naphthol
368
/3-Naphthol
369
Oxalic acid
370
Paraldehyde
371
Phenacetine
372
Phenyidimethylpyrazolone (antipyrine)
• 374
Phenylhydrazine ....
374
Phthalic acid
376
Phthalic anhydride
376
CONTENTS
XXI
Pyrogallol 377
Quinine ....... 378
Quinine sulphate ..... 378
Quinine hydrochloride .... 380
Resorcinol ...... 382
Saccharin ...... 383
Salicylic acid ...... 385
Salol 387
Santonine ...... 388
Strychnine 388
Strychnine nitrate ..... 389
Sulphanilic acid ..... 389
Sulphonal ...... 390
Tannin (tannic acid) .... 391
Theobromine ...... 392
Theobromine-sodium salicylate . . 393
Thymol ....... 394
Vanillin 395
Literature ...... 397
India-rubber and Rubber Goods.
A. Crude and Vulcanised Rubber . . 398
The examination of crude rubber . . 399
I. Determination of Resin, Moisture,
and Ash ..... 400
II. The Direct Determination of
Rubber 401
(a) The Tetrabromide method . 402
(<5) Nitrosite methods . . . 403
I. Alexander's method . . 403
II. Harries' method . . . 404
(c) Schneider's method. . . 405
{(T) Fendler's method . . . 406
((?) Spence's method . . . 406
III. The Determination of Protein
in Crude Rubber . . . 407
Vulcanised and manufactured rubber . 407
B. Accessory Materials of the Rubber
Industry ...... 409
Substitutes ...... 410
White substitute .... 410
Brown substitute . . . .411
Other organic accessories . . . 413
Bitumen 413
Pitch 413
Solvent naphtha . . . .414
Shale spirit ..... 414
Petroleum naphtha .... 414
Reclaimed rubber .... 414
Organic colouring matters . -415
Fabrics 415
Inorganic accessories .... 415
Sulphur . . . . . .415
Sulphur chloride . . . .415
Antimony sulphide . . . .416
PAOK
B. Accessory Materials of the Rubber
Industry — Continued.
Inorganic accessories — Continued.
Vermilion ....
Covering power
C. The Analysis of Rubber Goods
Special methods of analysis
I. Preparation of the sample .
Desiccation
Incineration
Total sulphur .
Chlorine ....
Sulphur combined with metals
Carbonic acid .
The direct isolation of filling
materials
Extraction with volatile solvent
Determination of substitutes
Resins insoluble in acetone
Pitch and bitumen .
The direct determination of
antimony and mercury sul-
phides . . . . .
The direct determination of
rubber ..
General scheme of analysis
Interpretation and statement of analy^
tical results ...
The examination of cable insulation:
and specifications for the same
Miscellaneous notes on the analysis
of rubber and of rubber goods
Coefficient of vulcanisation
Analysis of proofed fabrics
Rubber solutions .
Specific gravity
Microscopic examination
2.
3.
4-
5-
6.
7.
8.
9-
ID.
II.
12.
13-
14.
D. Empirical Tests applied to R
'bbei
I. Chemical tests .... 441
1. Dilute acids .... 441
2. Alkalis 442
3. Alcoholic alkali .... 442
4. Saline solutions .... 442
5. Chlorine 442
6. Fatty and mineral oils . . . 442
7. Resistance to oxidation . . 442
II. Physical and mechanical tests . 443
8. Dry heat test .... 443
9. Superheated steam . . . 443
10. Action of light .... 443
11. Permeability . . . .443
12. Resistance to pressure . . . 444
13. Percussion test .... 444
14. Insulation and breakdown voltage 444
15. Resiliency 444
439
439
439
440
440
441
Goods 441
417
417
417
418
418
418
419
419
422
422
423
423
42s
425
426
426
427
428
429
435
437
xxu
CONTENTS
PAOB
D. Empirical Tests applied to Rubber Goods —
Continued.
II. Physical and mechanical tests — Contd.
1 6. Abrasion ..... 444
17. Tensile test 444
18. Bending stress .... 447
19. Washers for bottle-stoppers . . 447
Gutta-percha and Balata .... 447
((7) Gutta-percha ..... 447
{b) Balata 45 1
Liter.-iture 451
Vegetable Tanning Materials.
Preliminary Notes on the Estimation of
Tannin ...... 452
A. Non-gravimetric Methods of Tannin
Analysis 453
I. The Loewenthal - von Schroeder
Method 453
II. Procter and Hirst's Modification of
the Loewenthal Method . . 458
III. Appendix 463
1. Estimation of moisture . . 463
2. Estimation of sugary matters . 463
B. The most recent Standard Gravimetric
Method of Tannin Analysis, according
10 the Regulations framed at the
Conferences of the International As-
sociation of Leather Trades Chemists 464
I. Resolutions of Previous Conferences
still in force ..... 464
1. Sampling the bulk . . . 464
2. Preparation of the sample for
analysis ..... 465
3. Preparation of the infusion . . 466
Solution of extracts . . . 467
Extraction of solid tanning
materials .... 468
II. Most recent Resolutions of the
International Conferences at Brus-
sels (1908) and Paris (1910) . . 469
General directions .... 469
Detailed official method of analysis
adopted by the International
Association of Leather Trades
Chemists which is obligatory on
all members 470
Literature ...... 474
Leather.
I. Accessories to the Processes prior to '
Tanning ...... 475
Water 475
Depilatories 476
Deliming, swelling, and bating materials 477
PAGE
II. Vegetable Tanning Materials and
Tannin Infusions .... 478
III. Mineral Tanning Materials . . 480
IV. Other Tanning Materials and
Accessories for Leather Dressing . 481
Preserved ^g'g yolk .... 481
Admixture of other oils . . . 482
Tallow ...... 483
Fish tallow . . . . .484
Fish oils ...... 484
Neat's-foot and bone oil . . . 488
Moeilon and Dcgras. . . . 488
Vaseline oils and mineral oils . . 493
Soaps ...... 493
V. Control of Working Conditions . . 493
The estimation of nitrogen . . . 493
Tan liquors ...... 495
Acidity ...... 496
Estimation of volatile and non-volatile
acids ...... 497
Spent tanning materials . . . 497
VI. The Examination of Leather . . 498
Sampling ...... 498
(rt) Vegetable tanned leather . . 498
Estimation of moisture . . . 498
Estimation of mineral matter (ash) . 499
Estimation of the fat ... 499
Estimation of the loss on washing
(Auswaschverlust) and of the •
content of extractable tans and
non-tans . . . . -499
Estimation of hide substance and
combined tannin . . . 500
Estimation of sugar . . . • . 502
Estimation of sulphuric acid and of
lime 503
Estimation of the specific gravity . 506
Nature of the tannage . . . £o6
Tannin penetration test (acetic acid
test) 506
Test of strength .... 506
Water-absorption test . . . 507
(J)) Chamois leather .... 507
{c") Chrome leather .... 507
Estimation of moisture . . . 507
Estimation of mineral matter . . 507
hstimation'of chromic oxide . . 508
Estimation of alumina . . . 508
Estimation of sulphuric acid and of
alkalis 508
Estimation of chlorides . . . 509
Estimation of fat and free sulphur . 509
Estimation of hide substance . . 509
Literature 510
CONTENTS
XXlll
Ink.
A. General Survey
B. Description of Different Classes of
Inks. .....
I. Black Writing Inks .
Normal inks ....
German official classification of
writing inks .
New Prussian regulations
The composition of English inks
Qualitative examination of writing
inks
Schluttig's "stripe" method.
Differential reactions
Practical tests of writing inks .
1. Determination of the darkening
Capacity
Acidity ....
Proportion of iron
2. The stability of the ink
3. The fluidity and penetrating
capacity of the ink and sticki-
ness of the writing .
4. Identification of different inks
5"
512
512
512
512
516
516
518
518
519
520
520
522
523
523
524
525
PAOS
B. Description of Different Classes of
Inks — Cojitinued.
I. Black Writing Inks — Continued.
Differentiation of inks in writing
II. Copying Inks
III. Coloured Writing Inks .
Tests for coloured inks
I. Blue and blue-black inks .
II. Green and green-black inks
III. Red and red-black inks .
IV. Violet and brown inks
V. Black inks
IV. Drawing Inks
Indian inks ....
Sepia .....
Waterproof inks
V. Printing Inks ....
VI. Ticket and Stencilling Inks .
VII. Marking Inks
VIII. Typing Inks
IX. Inks for Writing on Metals, Glass
etc
X. Sympathetic Inks .
Literature
525
£27
527
528
528
529
530
530
531
532
532
533
534
534
534
535
536
536
537
538
PART I I
Sugar.
Prefatory Note
I. The Sugar Beet .
A. Estimation of Sucrose
Alcoholic extraction .
Digestion methods .
539
539
542
544
547
((?) The warm alcoholic digestion
method 547
(J)) The warm aqueous digestion
method ..... 548
(t) The cold aqueous digestion
method 549
B. Estimation of Fibre or Juice and of
Dry Substance .... 552
C. Estimation of Invert Sugar . . 554
(3) Gravimetric estimation of small
quintiiies of invert sugar
(0.5-1.0 per cent.) in presence
of sucrose .... 555
((5) Gravimetric estimation of
larger quantities of invert
sugar in presence of sucrose . 558
(c) The gravimetric inversion
method 561
PAOB
I. The Sugar Beet — Continued.
C. Estimation of Invert Sugar — Contd.
(r/) The volumetric estimation of
invert sugar .... '63
The estimation of invert sugar
in beetroot .... 566
D. Beetroot Seeds .... 567
II. Beetroot Juice ^ Thin Juice^ and the Pro-
ducts occurring in the Working up of
Juice 568
1. Beetroot juice, thin juice . . . 568
A. Determination of Specific Gravity 569
B. Estimation of Sucrose . . . 578
(1) Gravimetric method . . 578
(2) Volumetric method . . 579
C. Estimation of Water and Non-
Sugar ; Purity Quotient . . 587
D. Estimation of Ash . . . 589
E. Estimation of Invert Sugar . . 590
F. Estimation of Alkalinity, Acidity,
and Coagulability . . . 591
G. Estimation of Colour . . . 592
2. Waste-water, wash water, etc. . . 592
3. Extracted slices and pressed slices ;
dry slices and sugar slices . . 594
4. Press mud, defecation mud . . 595
XXIV
CONTENTS
PAGE
I IF. Thick Juices, Syrups . . . . 596
A. Determination of Specific Gravity . 596
B. Estimation of Sucrose . . . 597
C. Estimation of Water and of Non-
sugar Constituents . . . 600
D. Estimation of Ash .... 606
E. Estimation of Invert Sugar . . 606
F. Estimation of Raffinose . . . 607
G. Estimation of Colour . . . 610
H. Estimation of Alkalinity . . .610
IV. .\fassecuites 610
A. Estimation of Dry Substance and of
Specific Gravity .... 610
B. Estimation of Sucrose . . .612
C. Estimation of Raffinose . . .612
D. Estimation of Invert Sugar . . 612
E. Estimation of Water . . . 6l2
F. Estimation of Ash . . . .612
G. Estimation of Alkalinity . . .612
H. Estimation of Colour . . .612
I. Estimation of the Content of Crystals 613
V. Sugar (^Raw Sugar, Refined Sugar,
After-products') 613
A. Estimation of Sucrose . . . 613
B. Estimation of Water and Non-sugar 614
C. Estimation of Ash .... 614
D. Estimation of Invert Sugar . . 614
E. Estimation of Raffinose . . .615
F. Estimation of Colour . . .615
G. Estimation of Alkalinity . . . 615
H. Examination for Sulphurous Acid . 616
I. Estimation of the Content of Crystals 616
K. Calculation of Yield (Rendement) 616
VI. Molasses, Runnings, Mother Syrups .617
A. Determination of the Specific Gravity 617
B. Estimation of Sucrose . . . 619
C. Estimation of Water and Non-sugar
Substances 623
D. Estimation of Ash .... 623
E. Estimation of Invert Sugar . . 623
F. Estimation of Raffinose . . . 624
G. Estimation of Colour . .624
H. Estimation of Alkalinity . . 624
VII. Products obtained in working up
Molasses ...... 624
A. Calcium Sucrate and VVaste Liquors 624
1. Calcium sucrate .... 624
(a) Determination of specific gravity 624
(//) Estimation of sucrose . . 625
(c) Estimation of lime . . . 625
(d) Estimation of purity . . 625
2. Waste Liquors .... 626
(a) Determination of specific gravity 626
{/>) Estimation of sucrose . . 626
PXOB
VII. Products obtained tn working up
Molasses. — A. Calcium Sucrate and
Waste Liquors — Continued.
2. Waste Liquors — Continued.
(c) Estimation of potash . . 626
(</) Estimation of nitrogen . . 627
B. Strontianite and Products of the
Strontia Process .... 627
1. Strontianite ..... 627
(ij) Estimation of moisture . . 627
(J>) Estimation of the portion in-
soluble in acid . . . 627
(c) Estimation of oxide of iron and
alumina ..... 627
(ji) Separation and estimation of
strontium and calcium car-
bonates . . . . .627
2. Ignited ore and residue . . 628
3. White salt, brown salt, centrifuged
salt and sucrate . . . 629
4. Charred vinasse .... 630
(a) Estimation of moisture . . 630
(/^) Estimation of the portion in-
soluble in water . . . 630
(c) Estimation of total alkali salts 630
(_d) Estimation of potassium chlor-
ide. . . • . . 631
(^) Estimation of potassium sul-
phate . . . . .631
(/) Estimation of potassium phos-
phate 631
{jg") Estimation of potassium car-
bonate 631
(//) Estimation of sodium carbonate 632
C. Osmose Water .... 632
D. Molasses Fodders .... 634
1. Estimation of moisture. . . 634
2. Estimation of sucrose . . . 634
3. Estimation of fat . . . . 635
4. Estimation of nitrogen . . .635
VI n. Accessories 636
A. Animal Charcoal .... 636
1. Estimation of moisture . . . 636
2. Estimation of carbon, sand, and
clay ...... 636
3.' Estimation of calcium carbonate . 636
4. Estimation of calcium sulphate . 638
5. Estimation of calcium sulphide . 639
6. Estimation of organic matter . 639
7. The mechanical analysis of char-
coal 639
8. Estimation of sucrose in spent
animal charcoal . . . 639
9. Estimation of phosphoric acid in
animal charcoal lye . . . 640
CONTENTS
XXV
PAGE
VIII. Accessories — Continued.
B. Strontianite and Strontium-contain-
ing Manufacturing Products . . 640
C. Limestone 640
D. Defecation Lime (Burnt Lime) . 640
E. Water 641
F. Sodium Carbonate, Sodium Hydrox-
ide, Hydrochloric Acid, Sulphuric
Acid 642
G. Saturation Gas, Flue Gases . .642
H. Fuel 644
IX. Products of the Cane Sugar Industry . 644
I. The Sugar Cane .... 645
Sampling 645
Estimation of sucrose . . . 645
Estimation of the dry substance . 647
Estimation of the expressed cane
(bagasse, megasse) . . . 647
II. Factory Products .... 648
Estimation of sucrose . . . 648
Quotient of purity .... 650
Estimation of the apparent purity of
crude juice . . '. , 652
Estimation of the reducing sugar . 652
Literature 657
Starch and Dextrin.
I. Starch 659
A. The Examination of Raw Materials 659
1. Estimation of starch by washing
out the raw material . . . 659
2. Estimation of starch by chemical
analysis ..... 659
Estimation of sugar in potatoes . 660
Estimation of the total solids of
potatoes . . . .661
The pentosans .... 661
3. Polarimetric estimation of starch . 667
4. Estimation of starch in potatoes
by the specific gravity methods . 669
B. The Examination of Different
Starches ..... 670
1. Potato starch . . . .671
2. Rye, wheat, and barley starch . 671
3. Oat starch .... 672
4. Rice starch .... 672
5. Maize starch .... 672
Estimation of the content of water in
starch 674
Estimation of acid in starch . . 678
Determination of the adhesiveness of
starch ..... 679
Examination of starch flour for
impurities and adulterations . 679
PAOE
I. Starch — Continued.
C. The Examination of the Waste
Products ..... 680
D. The Examination of the Auxiliary
Raw Materials used in the Manu-
facture of Starch . . . .681
II. Dextrin 682
A. The Examination of the Raw
Materials 682
B. The Examination of Auxiliary
Raw Materials . . . .682
C. Control of Working Conditions . 682
D. Analysis of Dextrin . . . 683
1. Estimation of the percentage of
pure dextrin .... 683
2. Estimation of water . . . 684
3. The acidity of dextrin . . . 684
4. The content of ash . . . 684
5. The content of sand . . . 684
6. Estimation of constituents soluble
and ^insoluble in cold and hot
water 684
7. Estimation of the soluble starch . 685
8. Estimation of the sugar . . 685
9. Determination of the keeping
quality and consistency of the
concentrated solution . . . 686
10. Determination of the viscosity . 686
11. Chlorine 686
12. Unchanged starch . . . 687
13. Scorched glutin .... 687
Literature 687
Alcohol, Potable Spirits, and Liqueurs.
I. The Examination of Water . . . 688
II. The Examination of Raw Materials . 688
A. Amylaceous Materials . . . 688
1. The polarimetric estimation of
starch in cereals . . . . 689
2. The estimation of starch by hy-
drolysis with diastase . . 690
3. The estimation of starch by fer-
mentation 692
B. Molasses 692
1. The estimation of fermentable
sugars 692
2. The fermentative capacity . . 693
C. Other Raw Materials . . .695
Wort extract and spirit yield of mash-
ing materials .... 695
XXVI
CONTENTS
PAGB
II. The Examination of Raw Materials —
Continued.
D. The Examination of Barley and
Malt 696
1. Barley 696
2. Malt 697
1. The determination of the dias-
tatic power of malt (Lintner
value) 697
2. The determination of the lique-
fying capacity of malt . . 698
3. The estimation of acidity . . 699
4. The estimation of moisture . 699
5. The cold water extract . . 700
III. The Examination of the Wort . . 700
1. The iodine test .... 700
2. The estimation of the total solids in
solution ..... 701
3. The estimation of "apparent mal-
tose and dextrin " . . . . 702
4. The acidity 704
IV. The Examination of the Fermented
Wort (Wash) 704
1. The presence of diastase . . . 704
2. Microscopic examination . . . 705
3. The degree of fermentation, " At-
tenuation " . . . . . 705
4. The estimation of maltose and
dextrin ...... 706
5. The acidity 707
6. Estimation of alcohol . . . 707
7. The total nitrogen and the soluble
nitrogen 708
8. The examination of fermented
molasses washes .... 708
V. Alcoholometry 709
VI. Denatured Alcohol . . . .713
A. The Examination of Wood Naphtha 715
I. Bromine decolorisation . . 715
:. The methyl orange alkalinity test 715
3. The estimation of methyl alcohol. 716
4. The estimation of acetone . . 716
5. The estimation of esters . . 717
B. The Estimation of Methyl Alcohol
in Ethyl Alcohol .... 717
C. The Estimation of Ethyl Alcohol in
Fusel Oil ....
VII. Potable Spirits and Liqueurs
A. Alcoholic Strength .
B. Secondary Constituents .
1. Total acidity
2. Volatile acidity .
3. Total solids and ash
PACK
720
720
720
722
723
723
723
VII. Potable Spirits and Liqueurs — Contd,
Examination of the distillate
724
4. Acidity of the distillate
7 -'4
5. Esters
724
6. Furfural ....
725
7. Aldehydes ....
725
8. Higher alcohols . . . ,
726
The Allen-Marquardi method
726
The Ruse-Herzfeld method .
728
The sulphuric acid (colorimetric^
method ....
733
Beckmann's nitrite method .
734
Potable spirits ....
735
I. Whisky ....
735
2. Brandy ....
735
3. Rum ....
735
4. Gin
736
5. Kirschwasser .
736
Liqueurs, bitters, and cordials .
737
I. The estimation of sugar ir
liqueurs ....
739
2. Colouring matters .
740
Literature .....
• 740
Vinegar.
Introduction ......
A. The Analysis of the Raw Materials
of the Vinegar Industry .
1. Malt
2. Barley, rice, rice grits, maize grits
3. Flaked maize ....
4. Glucose
5. Raw sugars, invert sugar, molasses
6. Acetic acid ....
7. Caramel .....
8. Sulphuric acid
B. The Analysis of V^ineg;ir .
1. The specific gravity .
2. Total acid ....
3. Alcohol
4. Heavy metals ....
5. Arsenic
6. Cyanogen compounds
C. The Further Examination of \'inegar 748
749
750
750
750
751
751
751
751
752
753
752
1. OeVermination of free mineral acid
2. Fixed organic acids
3. Total solids
4. Ash ....
5. Total phosphoric acid
6. Nitrogen ....
7. Potassium hydrogen tartrate
8. Foreign pungent materials
9. Polarisation
10. Preservatives .
11. Foreign colouring matters
741
744
744
744
745
745
745
745
747
747
747
747
747
747
748
748
748
CONTENTS
XXVll
C. The Further Examination of Vinegar —
Continued.
12. Aldehyde, glycerol, dextrin, fixed
and volatile acid . . . -753
Detection of misdescription . • . 753
Literature 754
Wine.
Prefatory note
The Analytical Examination of Wine .
A. The Drawing, Labelling, Storage
and Dispatch of Samples of Wine
for Chemical Analysis, and General
Remarks (German Regulations) .
B. Official Methods of Analysis
(German Regulations) .
I. Determination of the specific
gravity .....
Estimation of the alcohol .
Estimation of the extract (content
of extractives) ....
Estimation of mineral constriuents
Estimation of the sulphuric acid in
red wines .....
Estimation of the free acids (total
acids) .....
Estimation of the volatile acids .
Estimation of the non-volatile
acids ......
Estimation of the glycerol .
Estimation of the sugar
11. The rotatory power (polarisation)
12. Detection of impure glucose by
polarisation . . . .
Detection of foreign colouring
matter in red wines .
Estimation of the total tartaric
acid, free tartaric acid, tartar,
and tartaric acid combined with
alkaline earth metals .
Estimation of sulphuric acid in
white wines . . . .
16. Estimation of sulphurous acid
17. Estimation of saccharin
18. Detection of salicylic acid .
19. Detection of gum arable and
dextrin . • . . .
Estimation of tannin .
Estimation of chlorine
Estimation of phosphoric acid
Detection of nitric acid
24, 25. Detection of barium and of
strontium
26. Estimation of copper .
2.
3-
4-
5-
7-
9-
10.
13-
14.
15-
20.
21.
22.
23.
755
756
756
758
758
758
759
764
765
765
765
766
766
767
771
772
774
776
779
779
780
782
782
783
784
784
784
785
785
PAOE
L The Analytical Examination of Wine —
Continued,
C. Other Methods of Analysis . . 786
27. Detection of foreign colouring
matter in white wines. . . 786
28. Estimation of succinic acid . . 786
29. Estimation of lactic acid . . 787
30. Estimation of malic acid . . 790
31. Detection and estimation of citric
acid 791
32. Estimation of the volatile esters
of wine 792
33. Detection and estimation of
aldehydes 793
34. Estimation of dextrose and Isevu-
lose in musts and in sweet wines 793
35. Detection and estimation of
mannitol ..... 794
36. Detection of liquorice juice . 794
37. Detection of dulcine . . . 794
38. Detection of abrastol (asaprol) . 795
39. Estimation of nitrogen . . 796
40. Detection and estimation of boric
acid 796
41. Detection and estimation of
fluorine compounds . . . 797
42. Detection of hydrogen sulphide . 799
43. Estimation of lime, magnesia,
alkali-metals, silicic acid, iron,
alumina, manganese, heavy
metals, and arsenic . . . 799
44. Detection of oxalic acid . . 799
n. The Judging of Wines from the
Results of the Chemical Examination 800
The recognition of sugared
wines
800
"Marc "wines.
801
Yeast wines
801
Raisin wines (basis wines)
801
The addition of fruit must
and fruit-
wine to grape-wine
802
Boric acid in wine
802
Soluble fluorine compounds
in wine .
802
Salicylic acid in wine
803
Glycerol in wine
803
Sodium salts in wine
803
Volatile acids in wine
804
The judging of sweet wines .
804
Literature ....
805
Brewing Materials and Beer.
The Brewing Process
806
L Brewing Materials
808
■ A. Water ....
808
B. Malt ....
809
I. Extract
809
2. Tint ....
811
XXVIU
CONTENTS
I. Brewing MaUrials — Continued.
B. Mall— r(7w//n«/(/.
3. Moisture
4. Diastaiic power
5. Cold water extract
6. ^fodification
7. "Saccharification" time
8. Nitrogen
9. Soluble uncoagulable albuminoids 815
10. Physical examination
Growth of acrospire
Results of analysis .
Brown and Crystal malts
1. Extract
2. Tint
Black barle3's and malts
1. F.xtract
2. Tint
C. Caramel .
1. Extract
2. Tint
3. Ash ...
4. Iron ...
5. Deportment with beer
D. Flaked maize and rice
1. Extract
2. Moisture
3. Oil . . .
E. Grits and raw grain
F. Barley .
1. Moisture
2. Nitrogen
3. Starch .
4. Weight of skins .
The physical examination
5. Germination test .
G. Raw Cane Sugar .
H. Invert Sugar .
1. Albuminoids
2. Ash
3. Brewers' extract and water
4. Sucrose, dextrose, and Ixvulose
5. Unfermentable carbohydrates
I. Glucose and other Starch Sugars
K. Hops
PAOE
811
811
814
815
815
815
of barley
816
816
817
817
817
818
818
818
818
818
818
818
818
818
818
819
819
819
819
819
820
, 821
821
. 821
. 821
, 821
.821
822
. 823
. 823
. 823
. 824
. 824
. 827
. 827
. 828
1. Estimation of hard and soft resins 828
2. Direct estimation of antiseptic
power of hops .... 829
3. Estimation of moisture . . 830
4. Detection of " sulphuring" . . 830
Detection of free sulphur . . 830
Estimation of free sulphur . . 831
5. Physical examination of hops . 831
Interpretation of results of the
chemical analysis of hops . . 832
II. Beer .
1. Original gravity
2. Alcohol
3. Extract .
4. Forcing test .
PACE
. 832
. 832
. 835
. 835
. 835
Estimation of arsenic in brewing
materials and beer .... 836
Literature 837
Paper.
The determination of mineral contents . 838
The microscopic examination of the fibrous
constituents of paper .... 840
Preparation of the paper for examination 840
Mechanical wood
. 842
Wood cellulose .
. 842
Jute ....
. . 842
Straw cellulose .
. 842
Esparto cellulose
. 843
Linen
. 843
Hemp
. 843
Cotton
. 843
The degree of lignification of
wood cel-
lulose
. 844
Klemra's method of examination . . 845
The differentiation of sulphite and soda
wood cellulose .
. 846
The macroscopic determination
of mechani-
cal wood .
. 846
Determination of the hardness
of size in
paper
. . . 847
The examination of size .
. 847
Animal size (gelatin)
. 847
Rosin size
• 849
Casein size
. . . 851
Starch
. . . 852
Viscose
. 852
Wax, paraffin, stearine, fat, oil . .853
The determination of the rate of filtration
and separating capacity
of filtering
paper
. . . 853
Rate of filtration .
. . . 853
Separating capacity
. . . 854
The absorbency of papers
. • . 855
• The strip test .
. . • 855
The zone test .
. 856
Imperviousness to air .
. 856
The detection of free chlorine
and of free
acid ....
. . . 857
Impurities in papers injurious
to metals . 858
Loss of colour in paper
. 859
Other physical properties of p
aper of im-
portance in paper testing
• 859
Opacity
. 860
Bulk ....
. 860
CONTENTS
XXIX
Other physical properties of paper of im-
portance in paper testing — Continued.
Surface ...... 86i
Tenacity . . . . . .861
Elasticity 861
Breaking weight and bursting strain . 862
Literature 863
Textile Fibres.
I. The more important Reagents and
Operations employed in the Testing
of Textile Fibres .... 864
1. Iodine solution and sulphuric acid
mixture ..... 864
2. Zinc chloride iodine solution . 865
3. Reagents used for the identification
of lignified fibres . . . 865
4. Ammoniacal cupric oxide . . 866
5. Ammoniacal nickel solution . . 866
6. The separation of fibre bundles into
ultimate fibres .... 866
7. The preparation of thin cross-
sections . , . . _ . 867
II. The Chemical Examination of Textile
Fibres 867
1. Characteristic colorations with
dyestuffs 867
2. Action of solutions of different salts 868
3. Action of alkaline solutions . . 868
4. Action of acids, etc. . . . 869
A. Methods of Distinguishing Animal
and Vegetable Fibres . . .870
1. Molisch's method .... 870
2. The behaviour of fibres towards an
8 per cent, solution of sodium or
potassium hydroxide . . . 870
3. The rosaniline reaction . . . 870
4. Behaviour towards boiling nitric
acid . . . . . .871
5. Action of a " nitrating mixture " . 871
6. Behaviour of the fibres during
burning 871
7. Manca's oleic acid and sulphuric
acid test 871
B. Methods of Distinguishing Different
Fibres from each other . . . 872
1. Wool and silk . . • . 872
2. Cotton and linen .... 872
3. Flax and hemp .... 873
4. Jute from linen and hemp . . 873
5. Cotton, and kapok . . . 875
C. Quantitative Estimation of Indi-
vidual Fibres in Fibre Mixtures . 875
1. Cotton and wool .... 875
2. Silk, wool, and cotton . . . 877
PAGE
II. The Chemical Examination of Textile
Fi bres — Couiunced.
D. The Examination of Weighted Silk. 878
Qualitative examination . . . 878
Quantitative examination . . . 880
1. Estimation of water . . . 880
2. Weighting materials soluble in
water 880
3. Petroleum spirit or ether extract 880
4. Action of hydrochloric acid . 881
5. Action of alkalis . . . 881
6. Estimation of ash . . . 881
7. Colouring matters . . . 881
Quantitative estimation of the weight-
ing materials in dyed silk . . 882
Quantitative estimation of the weight-
ing materials in black silk . . 884
Stripping methods .... 885
(rt) Hydrofluoric acid method . 885
((J) Hydrochloric acid method . 887
(0 Oxalic acid method . . .887
(d) Sulphuretted hydrogen alkaline
sulphide method . . . 888
(e) Estimation of the boiling-off of
silk 889
E. Analysis of Shoddy, etc. . . . 889
Quantitative analysis . . . 890
Qualitative examination . . . 890
F. TheDegreeof Bleaching of Cellulose 891
G. Tests for Oxycellulose and Hydro-
cellulose ..... 891
III. The Microscopic Examination of
Textile Fibres .... 892
IV. Mercerised Cotton and Artificial Silk 894
Mercerised cotton ..... 894
Artificial silk ..... 897
Chardonnet, Lehner, Besangon,
Meteor or Frankfurt silk . . 898
Glanzstoff (Pauly silk) . . . 899
Viscose silk ..... 900
Acetate silk ..... 900
Vandura silk (gelatin silk) . . 900
Clement's method of examination . 901
Clement's method for the differentiation
of natural and artificial silk . . 902
Finishing Materials .... 903
Substances used in finishing . . . 903
The chemical examination of finishing
materials 903
Literature 909
Inorganic Colours.
I. Naturally occurring White Auxiliary
Colours —
Adulterants and substrata . . .910
Calcium carbonate . . . .911
XXX
CONTENTS
PAGE
I. Naturally occurring White Auxiliary
C o 1 our s — Continued.
Adulterants and substrata — Continued.
Quicklime . . . .911
Gypsum . . . . . .912
Barytes 913
White clays 915
II. White Pigments . . . .915
White lead 915
White lead substitutes . . . 921
Zinc white ..... 922
Lithopone 924
III. Grey Pigments . . . .933
Slate grey 933
Zinc sulphide grey .... 933
Zinc grey 933
IV. Yellow Pigments . . . .933
The yellow ochres .... 933
Siennas 935
The examination of mineral colours for
arsenic ...... 935
Artificial ochres .... 936
Realgar ...... 936
Orpiment ...... 936
Naples yellow ..... 936
Cassel yellow 938
Tungsten yellow .... 938
Litharge and massicot . . . 938
Uranium yellow .... 939
Cadmium yellow .... 939
Cadmium orange .... 939
Cobalt yellow (aureolin) . . . 943
Nickel yellow 945
The yellow chromium pigments -945
Chrome yellow .... 945
Chrome orange 946
Chrome red ..... 946
Valuation of the yellow and red
chromium colours and of the raw
materials used in their preparation 947
(a) Examination of potassium chro-
mate ...... 947
(/') Examination of chrome yellow . 947
{c) Examination of chrome orange
and chrome red .... 950
Zinc yellow 951
Barium yellow ..... 952
Strontium yellow .... 952
V. Red Pigments ..... 953
{a) Naturally occurring red pigments . 953
Red ochres and other red mineral
colours 953
(J)') Artificial products .... 953
English red ..... 954
Red lead (minium) .... 957
V. Red Pigments — Continued,
(h) Artificial products — Continued.
Brilliant scarlet
Vermilion (cinnabar)
Antimony vermilion .
Cadmium red .
Chrome red
VI. Blue Pigments .
Prussian blues .
Blue copper colours .
Blue cobalt colours .
Smalts ....
Cobalt blue .
Cceruleum
Ultramarine ....
I. The Analysis of Raw Materials
1. Clay.
2. Silica
3. Sulphur .
4. Sodium carbonate
5. Sodium sulphate
6. Rosin and pitch
II. Control of Working Conditions
Supervision of the burning process
and working up of the raw
product 985
III. The Examination of the Finished
Ultramarine .... 988
1. Colouring power . . . 988
2. Fineness ..... 988
3. Examination for free sulphur . 989
4. Examination for alum resistance 989
5. Examination for use in calico
printing ..... 989
6. Examination for use as a lacquer 990
IV. Analysis of Ultramarine . . 990
1. Preparation of the raw ultra-
marine for analysis . . . 990
2. Estimation of silica, clay residue,
and total sulphur . . . 991
3. Estimation of alumina and
sodium oxide . . . .991
4. Examination for additions in-
soluble in acid . . . 992
' r Properties of technical importance
in painting .... 993
Behaviour of ultramarines in mix-
tures 993
Fastness to zinc white . . . 993
VII. Violet Pigments .... 994
Cobalt violet 994
Manganese violet .... 994
Mineral violet .... 994
Violet and red ultramarine . . 995
961
962
965
965
967
96S
968
975
976
977
977
979
979
981
981
983
983
984
985
985
985
CONTENTS
XXXI
PAOE
VIII. Green Pigments .... 995
(a) Natural products . . . 995
Green earths (seladonite) . . 995
((5) Artificial green pigments . . 999
Cobalt green (Rinmann's green) . 999
iVIanganese green . . . 1000
The green chromium pigments . 1000
Chrome oxide green . . . looo
Guignet's green .... looi
Chromium phosphate greens . 1003
Arnaudon's green . . . 1003
Schnitzer's green . . . 1004
Mathieu Plessy's green . . IC04
Ultramarine green . . . 1004
(c") Green mixture - pigments of
chrome yellow and Paris blue 1004
Chrome green .... 1004
Zinc greens 1005
((/) The green copper pigments . 1006
X. Imitation native malachite
greens ..... 1006
Mountain green . . . 1006
Lime green . . . - . 1006
Bremen green .... 1006
Brunswick green • . . ico6
Erlau green .... 1007
BoUey's green .... 1007
Gentele's green . . . 1007
Eisner's green .... 1007
PAGE
VIII. Green Pigments — Continued.
{d') The green copper pigments — Contd.
2. Verdigris
Casselmann's green .
Saxon verdigris
3. Arsenic greens
Scheele's green
Emerald or Schweinfurth green
Neuwied green
IX.
Brown Pigments
(minera!
(a) Natural products .
Umber, umber brown
brown) ....
(Jj) Artificial products
Berlin brown ....
Florentine brown
X. Blaclc Pigments
Graphite
Appendix
I. Bronze pigments .
Tungsten bronze
II. Lakes from artificial dyes
Lake precipitants for acid dyes
Lake precipitants for basic dyes
Lake bases ('substrata) .
Examination of the dyes .
Examination of the substratum
Literature .....
1007
1007
1007
1008
IC08
1008
lOIO
lOII
lOII
lOII
I0I2
IOI2
I0I2
I0I2
I0I2
IOI3
IOI3
IOI4
IOI4
IOI4
IOI5
IOI5
IOI5
IOI6
IOI7
Appendix 1019
Index of Subjects 1083
Index of Names 1114
MINERAL OILS
By Prof. D. HOLDE, Ph.D., Divisional Director of the Royal Testing Laboratory,
Gross-Lichterfelde, Berlin, English translation revised by the late J. Lewko-
WITSCH, M.A., Ph.D.i
CRUDE PETROLEUM, NAPHTHA, BURNING OILS,
PARAFFIN WAX, ASPHALT, SHALE OIL,
AND LIGNITE TAR.
^.— CRUDE PETROLEUM.
Crude Petroleum is usually dark brown or black in colour, but occasion-
ally lighter-coloured varieties (pale yellow to reddish-brown) are met
with. According to the filtration hypothesis of D. Day, the lighter
colour of certain crude oils is to be attributed to the percolation of the
oil through subterranean layers of argillaceous shale, which absorb the
colouring matter. If the crude oil is allowed to percolate upwards
through a column of fuller's earth in a tube, fractionation takes place
to a certain extent, paraffin hydrocarbons accumulating in the lighter
fraction at the upper end, and heavy, unsaturated hydrocarbons at the
lower end of the tube. According to Hofer's view, however, the filtra-
tion hypothesis is not substantiated by geological observations.
Two chief types of crude oil must be differentiated : — (i) Crude oils
rich in naphthenes, with a paraffin-wax content of less than i per cent,
containing, as a rule, very small quantities of low-boiling fractions
(benzine and burning oils), and rich in high-boiling lubricating oils
which do not solidify readily ; (2) crude oils containing less naphthenes,
with a paraffin-wax content of 3-8 per cent., and yielding considerable
quantities of benzine, burning oil, and light, mobile lubricating oils.
Bustenari oil, however, notwithstanding its very low paraffin-wax
content, yields considerable quantities (25 per cent.) of benzine.
^ The Editor is indebted to Mr J. S. S. Brame, Lecturer on Fuel, The Sir John Cass
Technical Institute, for very kindly reading the proofs of this section, the MSS. of which had
been revised by the late Dr Lewkowitsch. — C. A. K.
Ill A
5 MINERAL OILS
American, Galician (Boryslaw and Tustanowice), and Roumanian
crude oil (from Campina) form the chief source of good paraffin wax
(for candles), burning oil, and petroleum benzine.
Most of the lubricating oils prepared from American, Galician, and
Roumanian crude oils have a higher solidifying point (about o ) than
Russian oils. A few Galician oils, e.g. that of Grosno, and a large
proportion of the Roumanian oils, namely, the oils of Bustenari, Moreni,
and Tintca, making up 70 per cent, of the Roumanian production, also
yield lubricating oils useful for lubricating engines, railway carriages,
etc., on account of their low solidifying point, suitable viscosity, and
high flashing point. For cylinder oils the highly viscous, salve-like
American products have proved the most suitable. The crude
petroleums from Java, Borneo, and Sumatra are noted for the
considerable amounts of low-boiling hydrocarbons useful as motor oil.
The crude German oils are mostly deep brown or black and somewhat
viscous ; those occurring in Alsatia arc suitable for the preparation of
benzine, burning oil, easily solidifying lubricating oils, "cleaning oils,"
gas oils, and asphalt ; recently, also, paraffin wax has been extracted
from them. The Hanoverian oils, especially the heavy oils from
Wietze, yield lubricating oils, but no paraffin wax, and but very little
benzine ; they contain, however, notable amounts of asphaltic substances.
In addition to the products enumerated above there are obtained, from
crude petroleums, transformer oils, and the still residues sold as Fuel
oil (Masut), Goudron, Asphalt, coke for electrodes, etc.
The world's production of crude petroleum in 191 2 was 46 million
tons, as compared with a production of 1050 million tons of coal. It is,
however, to be remembered that the calorific value of crude petroleum
is 1 1,000-1 1,100 Cal. per kilogram as against 7000-7500 Cal. for coal, and
only 4500-5000 Cal. for air-dried lignite. The distribution of the
world's production in 191 2, expressed as a percentage of the total, was
as follows: — United States 6325, Russia 19-37, Mexico 471, Galicia
2-43, Roumania 370, East Indies 3-09, India 2-03, Germany 0-28.
L CHEMICAL COMPOSITION.
Crude petroleum consists chiefly of hydrocarbons of various boiling
points, which do not belong to the lower boiling aromatic series
(difference from coal-tar hydrocarbons). The oils arc not dissolved
by sulphuric acid, whereas the heavier oils are partially converted into
soluble sulphonic acids. Aromatic hydrocarbons (benzene and the
higher homologucs) occur in small quantities in certain petroleums.
The chemical nature of the viscous lubricating oils of petroleum is still
unknown. Benzine, burning oil, gas oil, and paraffin wax consist, in
the case of Pennsylvanian petroleum, mainly of hydrocarbons of the
CRUDE PETROLEUM 3
methane series, C^^H.,^^^^. In the case of Russian petroleum 80 per
cent, consists of naphthenes, i.e. alicyclic polymethylenes, such as: —
pentamethylene, CH., . CH.^ . CH., . CH., . CH., ;
I " "^ ^ "I
hexamethylene, CH., . CH., . CH., . CH., . CH., . CH., ;
I I
methyl hexamethylene ; etc. The high-boiling fractions of the Russian
oils consist essentially of polynaphthenes (perhaps hydrodiphenyls).
The naphthenes resemble the paraffin rather than the benzene hydro-
carbons in their chemical behaviour ; they are not acted upon by
permanganate, or by concentrated sulphuric acid, but yield sub-
stitution products on treatment with chlorine and bromine, and even,
though with greater difficulty, with dilute nitric acid ; concentrated
nitric acid converts hexanaphthene into adipic acid, pentamethylene into
glutaric acid. Zelinsky has succeeded in preparing synthetically high-
boiling naphthenes — viz., cycloeikosan, C^qH^q, and cyclotessaracontane,
Qo^so (melting point 1 18°), starting from the methyl ester of sebacic
acid. As these experiments demonstrate the great tendency of the
naphthenes to polymerise, Charitschkoff doubts whether the high-boiling
viscous fractions of Russian petroleum consist of naphthenes, as is
generally assumed. In the German, Galician, and Roumanian
petroleums, the relative proportions of methane hydrocarbons and
naphthenes vary according to the special localities in which the oils
are found. In Galician and Roumanian oils notable quantities of
unsaturated hydrocarbons occur, and in the latter aromatic hydro-
carbons also. In some crude oils (especially those from Texas)
secondary products occur in small quantities, such as pyridine bases,
probably resulting from the decomposition of marine animals, according
to the Hofer-Engler theory of the origin of petroleum, sulphur com-
pounds such as mercaptans and organic sulphides (especially in Ohio
oils), and oxygenated and sulphurised asphalt. The hydrocarbons of
Texas oil belong chiefly to the series C^^H^,^,^, containing a double
polymethylene ring, whilst in Ohio oil members of the series C^H2„^2'
C^Hg,^, and C^Jr[^^^_^ are found. In Californian petroleums up to 15 per
cent, of nitrogen compounds, containing 2 per cent, of nitrogen, are
found, as also benzene, toluene, xylene, naphthalene, phenanthrene
and anthracene. In the crude oil from the Santa Barbara County even
members of the C^Ho„ « series were found ; this oil is remarkable for
its high viscosity and specific gravity. The heavy Wietze oil is rich
in asphalt. Engler and Jezioranski ^ showed that the fractions of
Galician, Russian (Bibi-Eybat), and Pechelbronn oils boiling above
1 Ber., 1895, 28, 2501.
4 MINERAL OILS
2CXd' dissolve almost completely in concentrated sulphuric acid, and
contain on an average 87 per cent, of carbon (as against S57 per cent,
in the olefines) ; hence they would appear to contain considerable
quantities of more unsaturated hydrocarbons. In the case of Pennsyl-
vanian petroleum, only 35 per cent, of the fractions boiling over
200' dissolve in concentrated sulphuric acid.
In the following Table the results obtained by the above authors are
collated : —
Table i.
Crude oil from
C per cent.
11 per cent.
0 per cent.
Galinii ....
Baku
Alsalia ....
Pennsylvania
86-18
86-21
85-38
86-10
13-82
13-49
12-68
13-90
0'-30
1-94
The fractions boiling below 200^ contain principally saturated
compounds of the methane and naphthene series. The elementary
composition of crude oils from various sources varies within the follow-
ing limits: — Carbon, 79-5-887; hydrogen, 9-6- 14- 8 ; oxygen, oi-6-9;
nitrogen, o-02-i-i ; and sulphur, 0-OI-2-2 per cent.
The following methods serve for the recognition and separation of
the several groups of the constituents of petroleum : —
1. Acidic constituents (naphthenic acids, phenols) are extracted by
dilute sodium hydro.xide.
2. Nitrogen compounds (homologues of pyridine, etc.) are extracted
by dilute mineral acid.
3. Unsaturated aliphatic hydrocarbons are extracted by sulphuric
acid.
4. Aromatic hydrocarbons are detected by nitration,
5. Unsaturated cyclic hydrocarbons are separated b}' the Nastjukoff
test (p. 8G).
II. SPECIFIC GRAVITY AND COEFFICIENT OF EXPANSION.
The specific gravity of crude petroleum varies from o 730-0-970 ; thus
Pennsylvanian oil has a gravity of o-8i6;Baku oil, 0-882; Ohio oil,
0887; East Galician oil, 0-870; heavy Wietze oil, 0-955. ^'^ one case
Engler found a sp. gr, of almost i^o.
A low specific gravity indicates a high proportion of benzine and
burning oil ; a high specific gravity, on the other hand, indicates a notable
proportion of high-boiling fractions and of asphalt. The specific gravity,
although giving very little indication as to the source of a petroleum,
may serve as a useful guide in the classification of oils of known origin,
and has a considerable commercial importance for purposes of com-
CRUDE PETROLEUM 5
parison and identification, inasmuch as the specific gravity forms the
simplest means of controlh'ng deliveries of oil.
The determination of the coefficient of expansion of crude oils is of
importance for the correction of the specific gravity determined at
various temperatures to the normal temperature (15° or 20^), as also for
the calculation of the expansion of the oil in the storage vessels and
stills.
The coefficient of expansion (a) of Pennsylvanian oil is 0-000840,
that of Russian oil 0-000817 (of Wietzeoil 0-000647) ; hence it decreases
as the specific gravity rises. The values for a series of oils are given in
the subjoined Table.
Table 2.
Source.
Sp. gr.
ax 1,000,000.
Canada .....
Alsatia
11 .....
West Galicia ....
Wallachia
0-828
0-829
0-861
0-885
0-901
843
843
858
775
748
Zaloziecki and Klarfeld found an exceptionally high coefficient of
expansion (about o-ooi) in the case of Galician crude oil from Boryslaw
and Tustanowice.
The determination of the specific gravity and coefficient of expansion
of crude oils is carried out as described in the section on " Lubricants "
(this Vol., pp. 61 and 6t,).
III. DETERMINATION OF CONTAINED WATER.
1, A method much used in oil refineries, but not universally
applicable, is to place a measured quantity of crude oil, say 200 c.c,
in a 500 or looo c.c. stoppered cylinder, best constricted at the bottom
and graduated. Two to four times the volume of petroleum spirit or of
benzene are added, and the whole warmed and shaken. After settling,
the water content is read off; but as emulsions are readily formed and
the reading is thus rendered indistinct, it is usual to take only 70 per
cent, of the volume read off as water. The method of shaking with
petroleum spirit is not applicable to oils which are rich in asphalt, as
the latter is precipitated by petroleum spirit to some extent ; in this
case benzene must be used, which, however, readily leads to the
formation of emulsions.
2. A method which is universally applicable for the determination
of water consists in the distillation of the oil with xylene. According to
Hofmann and J. Marcusson 100 g. of the crude oil (or 50 g. if the water
content is high) are mixed with 100 c.c. of xylene, which has been
6 MINERAL OILS
previously saturated with water by shaking, and distilled in a 600 c.c.
flask containing fragments of pumice, until 80-90 c.c. have passed
over. The distillate is collected in a graduated cylinder which is
constricted at the bottom. After rinsing out the condenser tube with
xylene, and detaching any drops of water adhering to the sides of the
cylinder, the quantity of water can be read off.
M. Wielezynski ^ uses a centrifuge to separate the water, the centri-
fuge being heated by a steam-jacket in the case of thick oils.
Mechanical impurities are, however, separated together with the water,
and the separation is not always satisfactory. Other methods of a
chemical character have been proposed, such as the alteration in the
titrc of X/io hydrochloric acid on shaking with the oil, due to the
dilution by the water present;- the measurement of the acet)-lene
evolved when calcium carbide is allowed to react with the oil, and of
the hydrogen evolved when sodium is brought into contact with an
ethereal solution of the oil."^ None of these proposals can be
recommended.
IV. DETERMINATION OF MECHANICAL IMPURITIES.
Qualitative Exaniiiiation. — Mechanical impurities are detected by
shaking 2 c.c. of oil with 40 c.c. of benzene, and allowing to settle for
several hours.
Quantitative Determination. — From 5-10 g. of the well-mixed oil are
weighed out and dissolved in 100-200 c.c. of benzene. After standing
for some time, any water which has separated out is drawn off, and the
solution is filtered through a filter paper previously dried at 105°.
After washing with benzene and drying at 105°, the filter paper and
impurities are weighed.
Any suspended particles of pitch and asphaltic substances are not
determined by this method, as they are dissolved by benzene; the
determination of these is described on p. 9. Any mineral salts
introduced by the bore-holes mud, or by chemicals added in the
refining process, are determined by washing the residue on the filter
with water, evaporating the solution, and weighing the residue.
Russian specifications direct to dilute a weighed quantity of the oil
with petroleum spirit and to filter through a filter paper. The residue
is incinerated and weighed.
V. YIELD OF NAPHTHA, BURNING OIL, LUBRICATING OIL, ETC.
Laboratory methods should be adapted to the requirements of the
works concerned, the nature of the raw materials, the methods of
distillation in use, and so forth. I'rom one and the same crude oil very
1 Petroleum, 1906, 2, 285 ; r/. also Rosenthal, Chem. Zeit., 1909, 33, 1259.
2 Neltel, C/ierrt. ZeU., 1904. 28, 867. ' Graefe, Petroleum, 1906, I, 815,
YIELD OF NAPHTHA
b^
3^
different yields of the various fractions are obtained, depending on the
method of distillation, the height of the fractionating column, and other
factors. The general procedure in the laboratory consists in distilling
from I to I kg. of crude oil in glass or metal retorts. The distillate is
condensed at first with water and then atmospherically, and is measured
in definite ranges of boiling points up to 150° (c/. p. 17). The heavy
fractions boiling above 3CXD° are best dis-
tilled with superheated steam, in a vacuum
of 300-400 mm. The characters of the
distilled fractions are determined after
purification by shaking with 1-8 per cent.
of concentrated sulphuric acid.^
When mineral oils, after refining with
acid, are washed with alkali and with
water, persistent emulsions frequently
make their appearance. Heavy oils must
be kept hot and shaken violently to effect
separation. As this is not easily done
in a separating funnel, the. washing and
separating apparatus shown in Fig. i is
recommended. The glass vessel a, having
two stopcocks d and d' for emptying, is
fitted with a glass or aluminium steam-
coil d, and a glass tube c through which
air is blown. The lower stopcock d' is
useful for separating small quantities of
oil which may have passed through d.
Should the apparatus be used for refining
with acid, a third tap may be placed at the shoulder of the vessel, in
order to separate the oil from resinous matter. The top of the vessel
may be closed by a suitably bored lid to prevent splashing. Finally,
the washed oil is dried by blowing the heated oil with air.
Since the various forms of laboratory distillation apparatus give
quite discordant results with one and the same crude oil, specially
constructed apparatus is employed for the fractional distillation of
naphtha, kerosene, etc., for purposes of commercial control, and in
Germany especially for Customs purposes.^ These are made of specific
dimensions, and give reliable comparative results under the same
conditions of experiment.
Oils which contain water are carefully dehydrated before testing by
shaking with calcium chloride at the ordinary temperature.
In place of the intermittent distillation by Engler's method,^ which
1 Cf. Holde, MineralSle, p. l6 ^/ seq. "- Cf. Singer, Chem. Rev., 1896, p. 93.
* Cf. Boverton Redwood, Petroleum and iis Products, vol. ii., p. 204.
LJ
Fio. 1
a'
8
MINERAL OILS
X —
S3 A
U-fi,f^->''
occupies a considerable time and does not always give concordant
results, the improved continuous distillation method of Holde and
Ubbelohde is to be recommended. The apparatus employed (Figs.
2, 3, 4) consists of the original Engler's flask (Fig. 2), which is heated
in a sheet-iron oven by a Bunsen burner fitted
with a tap. The condenser is 60 cm. long. The
distillate is collected in six test tubes divided
in 0-2 c.c. and rotatable in a stand. They are
cooled in water at the ordinary temperature.
To carry out the test, 100 c.c. of oil are
filled into the distillation flask. This quantity
holds good, however, only for petroleum and
crude oils which yield a sufficient quantity of
low-boiling constituents in a given time, so
that the expansion of the heavy oils does not
p,Q^ 2, cause any difficulty. For high-boiling oils, e.^.,
"astatki" and lubricating oils which would
readily boil over in a 100 c.c. flask, the flask must have a capacity of
at least 140 c.c, or the quantity of oil must be reduced to 80 or 90 c.c.
The temperature at which the first drops of distillate
fall into the receiver is taken as the boiling point.
The rate of boiling is fixed at 2 drops a second ;
this is best controlled by means of a seconds'
pendulum.
In some factories, such as those working Gali-
cian oil, the boiling point limits of the petroleum
fraction are i50°-275°. All fractions except the last
are collected and measured without waiting for the
several fractions to drain off.
The fractional distillation test prescribed by the
New York Produce Exchange may be carried out
with a small still and condenser, or with any other
simple form of distilling apparatus. The fractions
taken off the condenser must each form one-tenth
of the crude oil by volume ; the specific gravities of
each fraction must then be determined.
In Germany special apparatus is prescribed for
the use of Custom officers. The directions are laid
down in an official publication entitled, Anleitung
fiir die Zollabfertigiuig, Berlin, 1906, part iii.
FiQ. 3.
VI. FLASHING POINT.
The flashing point of an oil is the temperature at which it gives off
so much vapour, in the "open test," that the latter takes fire when a
FLASHING POINT
flame is passed over the surface of the oil ; or in the " close test," that
temperature at which so much vapour collects above the surface of the
oil in a closed vessel (Abel's, Gray's, or Pensky's apparatus) that it
forms an inflammable mixture with the air contained in the vessel.
Crude oils from different sources have different flashing points,
mostly in the neighbourhood of 0°. Those containing much naphtha,
such as Javanese and American petroleum, have a considerably lower
flashing point, whilst oils free from naphtha, such as the heavy
Hanoverian oils, flash between yo" and 80°.
Fio. 4.
The flashing point is determined in this country by means of the
standard Abel apparatus (see p. 29) in the case of low-flash oils, and
by means of either the Pensky-Martens or Gray's apparatus in the
case of high-flash oils. In Germany the Abel-Pensky and the Pensky-
Martens apparatus are used for low-flash and high-flash oils respectively.
At the recent International Petroleum Congress (Vienna, 1912), the
Abel-Pensky (Abel-P.) apparatus was adopted as an international
standard, provided, of course, it be sanctioned by legislation in the
respective countries.^
VII. DETERMINATION OF ASPHALT.
Some crude petroleums (especially those of Hanover) contain
notable amounts of asphalt. Analytical methods for its detection and
^ Cf. Petroleum, 1912, 7, 468.
10 MINERAL OILS
quantitative estimation have been proposed by Holde. These methods,
however, yield only comparative results, and therefore can be only
looked upon as provisional, especially so as much depends on the
character of the petroleum spirit employed for the extraction. In
Germany a special " normal benzine " of the sp. gr. 0-695-0/05 at
15° and boiling from 65'-95° has been proposed for this purpose.
{C/.P.21.)
Detection of Asphalt. — About i c.c. of crude oil is shaken in a test
tube with 40 c.c. of petroleum spirit, and the liquid allowed to stand.
If asphalt be present dark flocks separate out either immediately or on
standing (for a day if necessary).
Or, 0-5 c.c. of oil is dissolved in 5 c.c. of ether, and 7 c.c. of alcohol
are added. Hard and soft asphaltic substances are thereb)- precipitated
as a viscous mass adhering to the sides of the vessel.
Determination of Asphalt.
1. Hard Asphalt. — 5 g. of crude oil are shaken in an Erlenmeyer flask
with 220 c.c. of petroleum spirit ; in the case of oils poor in asphalt, 5-20
c.c. of oil are taken. After standing for at least a day, the clear liquid
is decanted through a small pleated filter. The bulk of the precipitate
is brought on the filter, and the flask and filter are washed with the
solvent until the filtrate no longer leaves an oily residue on evaporation.
The asphalt on the filter is then dissolved by means of hot benzene, the
solution concentrated by distillation, the remainder washed into a
weighed dish, and the solid residue, after evaporation and drying at
100°, weighed. This procedure leaves any non-asphaltic matter which
may have been precipitated by petroleum spirit on the filter; this
may be estimated separately.
When it is desired to differentiate between dissolved and suspended
asphalts in the crude oil, two determinations are made, as above —
one on the original oil, the other on the same oil after it has been
filtered without warming. The difference found represents suspended
asphalt,
2. Soft Asphalt. — 5 g. of crude oil are dissolved at is"" in 25 vols,
of ether, and \2\ vols, of 96 per cent, alcohol are added, drop by
drop, from a burette, with continuous shaking. After standing for five
hours at 15 , the liquid is filtered as above, and tiie precipitate washed
with ether-alcohol (2:1), so long as oily matter is extracted ; it is then
dissolved in benzene and evaporated down. In order to remove any
paraffin wax in the residue, it is boiled out repeatedly with 30 c.c. of
96 per cent, alcohol, until no more paraffin wax separates out on
cooling. Finally, the residue is dried for a quarter of an hour at 105°,
and weighed.
PARAFFIN WAX
11
VIII. PARAFFIN WAX.
I. A method of determining paraffin, originally proposed by
Grotowsky, worked out by Engler and Bohm, and modified by Holde,
is carried out as follows : — lOO g. of crude petroleum are rapidly distilled
from a glass retort until a thermometer placed in the vapours registers
300°. The condenser is then removed, a fresh receiver of known weight
is fitted, and the remainder of the oil is distilled without a thermometer,
until only coke is left behind. The weight of the heavy distillate, which
is considered to contain all the paraffin wax, is then ascertained.
Of the heavy distillate 5-10 g. are dissolved at the ordinary
temperature in a mixture of equal volumes of
absolute alcohol and ether. The solution is placed
in a test tube (see Fig. 5) cooled to —20" until
a clear solution results, and so much of the ether-
alcohol mixture is added until, at —20'^, all oily
matter has disappeared, and only flocks of paraffin
are observed. The paraffin wax is then filtered
off by suction, in a funnel cooled by a freezing
mixture (see Fig. 5), washed with previously cooled
ether-alcohol, and finally washed off the filter
with hot petroleum spirit or benzene into a
weighed glass dish. After removal of the solvent
by cautious evaporation on the water-bath, the
outside of the dish is wiped dry, and its contents
are examined. If the paraffin is hard, the dish is
heated for a quarter of an hour at 105", allowed to
cool in a desiccator, and weighed. Should the
paraffin, however, be soft, i.e., melting below 45°,
it is better to dry it for several hours at 50° in a vacuum desiccator.
In washing the precipitated paraffin with cooled ether-alcohol, 5 c.c.
of the filtrate must be tested from time to time by evaporation ; wash-
ing is complete when either the residue is negligible in amount or is
solid at the ordinary temperature.
When the method is applied to crude paraffin waxes, 0-5-1 g. is
weighed out and dissolved in 10-20 c.c. of ether-alcohol (see p. 46).
A correction is made for the solubility of paraffin wax in ether-
alcohol. The percentage found is increased by 0-2 per cent, in the
case of fluid oils, 0-4 per cent, in the case of oils beginning to solidify at
15°, and I per cent, in the case of crude paraffin wax.
This method gives the true proportion of paraffin only in the
case of hard paraffin waxes suitable for candle-making. Soft paraffin
waxes melting below 50" are not completely precipitated by ether-
Fio.
12 MINERAL OILS
alcohol at —20 ; but the greater part of the paraffin which goes into
solution can be recovered by evaporating down the filtrate, and redis-
solving the residue in the least possible quantity of ether-alcohol (i : 2)
at— 20. In the preliminary distillation (which is only necessary
with the dark kinds of crude oil), a small proportion of paraffin wax
undergoes decomposition. This source of error is the more serious, the
higher the paraffin content of the crude oil ; when there is 5 per cent,
of paraffin present, the error may amount to 0-5 per cent, on the content
of paraffin.
As the method described is universally applicable, other methods
which have only a restricted application, need only be briefly
mentioned.
2. R. Pawlewski and J. Filemonowicz ^ shake from 5-20 c.c. of oil
with 100-200 c.c. of glacial acetic acid, filter off the separated paraffin, and
wash it two or three times with glacial acetic acid and then two or
three times with 75 per cent, alcohol, dry the precipitate, and weigh.
The method does not, however, give reliable results for the paraffin
wax in lignite or petroleum, as soft paraffin wax is soluble in glacial
acetic acid, and heavy mineral oils cannot be separated quantitatively
from paraffin wax by glacial acetic acid.
3. R. Zaloziecki - dissolves 10-20 c.c. of the sample in five times its
volume of amyl alcohol, and precipitates with the same quantity of 75
per cent, ethyl alcohol at a temperature not exceeding 4". After stand-
ing for several hours in the cold, the liquid is filtered through a cooled
filter, and washed with a cooled mixture of 2 parts of amyl alcohol and
I part of 70 per cent, alcohol. The paraffin wax is then dissolved in ether,
and after evaporating this off, it is dried at 125^' until the amyl alcohol
is completely removed. This procedure may be used to determine
paraffin wax in the presence of fatty acids, neutral fats, rosin and rosin
oils, but cannot be used in the presence of beeswax, as this is also
precipitated from amyl alcoholic solution by ethyl alcohol. Shukoff and
Pantuchoff-' subsequently suggested, as improvements on Zaloziecki's
method, the use of 90 per cent, ethyl alcohol for the precipitation, and
the cooling of all the solutions to 0°. The process is not suitable for
mineral lubricants, especially those which are very viscous, as it is
hardly possible to separate the paraffin wax completely from the oil.
If, however, the precautions mentioned are carefully observed, it can be
used with success for lignite-tar products. The drying of the paraffin
wax at lower temperatures than 125° is recommended.
4. R. Holand's method * for the determination of paraffin wax in
» Ber., 1888, 21, 2973.
■- Dingl.polyt.J., 1888, 267, 274 ; /. Soc. Chem. Ind., 1888,7, 349-
^ Russian '■'■Journal of Fats y 1900.
^ Chem. Zeil., 1893, I?. 1473. ^'nd 1483 ; /. Soc. Chem, InJ., 1894, 13, 286.
SPECIFIC HEAT la
lignite-tar products has not been tested for other materials, and is
probably unsuitable for petroleum products. It depends on the fact
that the lignite-tar oils containing paraffin are soluble in absolute
alcohol, and that at a certain temperature only the paraffin separates
out.
IX. SPECIFIC HEAT.
The specific heat of crude oils is of importance, if it be a question
of using the waste heat of steam for pre-heating the oil previous to
distillation ; or if dehydration of a crude oil by means of indirect steam
is contemplated, when the amount of heating surface required can be
calculated. The specific heat is also required for calculating the
capacity of the refrigerating plant needed for the recovery of the
paraffin wax.
Two methods are in use for the determination of the specific heat.
E. Graefe^ burns 0-4 1-0-43 S- of a substance of known heat of
combustion {e.g. pure cellulose, in the form of absorbent pads manu-
factured by Schleicher and Schiill ; 1 kg. =4175 Cal.) in a bomb
calorimeter. The sample of oil is used as the outer liquid in the calori-
meter. From the quantity of cellulose taken («), the quantity of oil {b),
the water equivalent of the calorimeter (W), and the observed rise of
temperature (T), the specific heat can be calculated from the formula : —
«.4i75 = W T 4- ^^T.
By this method Graefe found the specific heat of various oils to
range from 0-4-0-5.
Another method ^ depends upon the measurement of the heat
produced by passing a current of known intensity (/) for a given time
(2) through a strip of nickelin of resistance r immersed in the oil under
examination. The rise of temperature {t) is read off, and the specific
heat calculated from Joule's law {w being the water equivalent of the
calorimeter), according to the formula : —
{ni . c-\-iu) t = 0-239 z'2 r z.
The results obtained by this method in the " Reichsanstalt " are in
good agreement with those of Graefe.
The more hydrogen an oil contains, the higher is its specific heat,
and the richer it is in carbon and oxygen, the lower its specific heat.
The specific heat as calculated from the elementary composition by
Kopp's law, according to which the molecular heat equals the sum of
the atomic heats, is in very good agreement with the experimental
value. It is not even necessary to know the molecular composition
^ Petroleum.^ 1907, 2, 521.
^ Cf, Kohlrausch, Introduction to Physical Measurements^ translated by Waller and Procter,
3rd ed., p. 118.
u
MINERAL OILS
of the oil, as it is sufficient to divide the percentages of C, H, and O
by the respective atomic weii^hts, and to multiply these quotients by
the atomic heats, viz., C= i-8, H = 2-3, 0 = 40.
X. LATENT HEAT OF EVAPORATION OF PETROLEUM FRACTIONS.
A knowledge of these constants is necessary, in designing a works
plant, for determining the requisite heating arrangements, the dimen-
sions of the condensers, and the supply of condensing water. It is true
that these data are commonly arrived at by empirical methods, but
occasions arise when first principles have to be resorted to. The latent
heats as required for the proper calculation of distilling and condensing
plant may be conveniently determined in the apparatus designed by
V. Syniewski,^ shown in Fig. 6.
Fio. 6.
The vapour generated in the flask A, charged with about 400 c.c.
of the fraction to be examined, passes through a b to the jacketed
vessel f, and thence past the bell-valve z into the condensing worm c
fitted inside the calorimeter B. The calorimeter system is closed off
by z as long as condensation of vapour takes place in l\ whence
condensed liquid runs off through d. When c contains only vapour,
free from liquid, ;: is opened and the vapour is admitted into the
calorimeter, which is charged with about 1200 c.c. of water. The
thermometers T and / serve to show the temperatures of the calori-
meter and of the vapour respectively. Distillation into the calorimeter
is continued until the boiling point has risen by 20^, it being convenient
to deal with fractions at intervals of 20^ boiling point. The calorimeter
is now closed off at .:; and the whole of the distilling apparatus
1 Z. angeu'. Chein., 1898, II, 621 \J. Soc. Chem. fnJ., 189S, 17, 751.
LATENT HEAT OF EVAPORATION
15
removed, when the amount of condensed liquid is determined by
weighing. The determination of the specific heat is conveniently
carried out with the condensed liquid. The total heats of evaporation
determined in this way at the " Reichsanstalt " ranged from 130-190 Cal.
in the case of various crude oils and the products derived therefrom.
E. Graefe determines the heat of evaporation by passing the
vapour of the mineral oil through a form of Liebig's condenser and
measuring the rate of flow and rise of temperature of the condenser
water, on the principle of the observations made with the Junkers'
calorimeter. The loss of heat by radiation is determined in a
preliminary experiment by distillation of a liquid of known heat of
evaporation. The heats of evaporation of various lignite-tar oils were
found to range from 120-220 Cal.
Graefe^ has also shown that the heat of evaporation can be
calculated from the molecular weight and the boiling points. Trouton
had established for definite chemical compounds that when equimole-
cular quantities are taken, the quotient of the heat of evaporation
and the absolute temperature of the boiling point is a constant,
approximately 20. Now although the mineral oils are not definite
chemical compounds, and moreover have not a constant boiling point,
Trouton's formula can still be applied to them if mean values are
adopted for the molecular weight and boiling point. The heat of
evaporation is then : —
20 T
VV
M
The mean molecular weight of an oil is determined by the lowering
of the freezing point of commercial stearic acid. The molecular
depression is ascertained in a preliminary experiment with a substance
of known molecular weight ; a weighed quantity {0) of the oil is then
dissolved in a known quantity {s) of the stearic acid and the depression
of the freezing point determined. \( k be the molecular depression of
the stearic acid and t the depression of the freezing point,
c.ioo. k
M =
s t
The following mean molecular weights were obtained in this way.
Table 3.
Lignite-tar oil.
Light crude oil
Heavy crude oil
Gas oil
Light paraffin oil
Sp. gr.
0-883
0-905
0-890
0-920
Mol. \vt.
113
158
158
190
Petroleum^ 1910, 5, 569.
16 MINERAL OILS
Charitschkoff,' by calculating the molecular weights from determina-
tions of the vapour density by Hofmann's method, arrived at results
similar to those of Graefe.
For the determination of the mean boiling point the oil is distilled
continuously in Englcr's apparatus, and the boiling points noted for each
lo per cent. The arithmetical mean of these temperatures gives the
mean boiling point. Graefe found the following figures for a light
crude oil. The liquid commenced to boil at 124°.
Distillate . 10 p. c. 20 p. c. 30 p. c. 40 p. c. 50 p. c.
Temperature . 173 184 192 201
no
Distillate . 60 p. c. 70 p. c. 80 p. c. 90 p. c. 98 p. c.
Temperature . 221 234 255 285
;oo
From this follows the mean boiling point = 2 16° C. = 489° abs.
Using Trouton's formula, the heat of evaporation is : —
W = ^ = --^^^^ = 86.5.
M 113 ^
In order to calculate the total heat of evaporation, the heat necessary
to raise the oil from the ordinary temperature (25°) to the mean boiling
point (216°) must be included. Taking the specific heat of the oil as
0-43, this gives 0-43 (216 — 25) = 82 Cal. Hence, the total heat of
evaporation is 86-5+82= 168-5 Cal. It is thus seen that in the case of
this oil, almost as much heat is used in heating the oil to its boiling
point as in the actual distillation. In many cases the conditions are
still less favourable. From this result the great importance of warming
the oil by waste heat before distilling is apparent.
> ^.—NAPHTHA.
The term " Naphtha," or " mineral naphtha," or " petroleum naphtha,"
is generally held to cover all those fractions of crude petroleum which
boil bjslow 150°. The limit of 150^ is not observed by all refineries,
and the naphthas sold are apt to show wide variations. The nature
and value of both crude and redistilled naphtha arc determined in the
laboratory by fractional distillation with a dephlcgmating apparatus.
In the commercial valuation of naphthas great stress is laid on a
mild smell and on water-white colour. Patents have recently been
taken out for masking the evil smell of badly refined naphtha by the
admixture of turpentine and treatment with alkali. Such additions are
detected by the methods given on p. 21.
^ Physikahsche Unkrsuchuug des Erdoh,
NAPHTHA
17
I. SPECIFIC GRAVITY.
This is measured either by Mohr's balance, hydrometers, or pykno-
meters, and is stated for a temperature of 15" (see "Lubricants," p. 61).
The specific gravity test serves chiefly for the identification of a
sample.
The subjoined Table, due to Mendelejeff, facilitates the calculation of
the specific gravity at the working temperature to that at the standard
temperature of 15°: —
Table 4.
Sp. gr.
Correction for 1°.
Russian oil.
Pennsylvanian oil.
0-700 to 0-720
0-720 „ 0-740
0-740 „ 0-760
0-760 „ 0-780
0-780 „ 0-800
0-00082
0-00081
0-00080
0-00079
0-00078
0-00086
0-00082
0-00077
0-00072
0-00068
II. EVAPORATION TEST.
Petroleum spirit boiling below ioo° (sp. gr. o-yo-o-yi) should leave
no residue when evaporated in a watch-glass on a lukewarm water-bath,
nor should it leave a grease-spot on paper. A negative result with
both of these tests indicates the certain absence of heavy oils.
III. FRACTIONAL DISTILLATION.
Petroleum spirit used as motor fuel should, according to Continental
practice, contain nothing, or at very most 5 per cent., boiling above 100°.
If this limit is exceeded, evaporation in the carburettor may become so
sluggish, especially in cold weather, as to lead to misfires. Hence
motor petrols, no less than solvent naphthas, need to be tested by
fractionation. The commercial motor oils, sold in this country under
the technical term " petrol," have higher boiling points ; as a rule,
60-70 per cent, only boil below 100°, about 25 per cent, pass over
between ioo°-i20°, 5-6 percent, from 120°- 13 3'', and about 3 per cent,
above 133".^ Petrols containing much larger proportions of higher
boiling fractions are, however, now used in modern carburettors in
which the exhaust gases jacket the in-going air.
In the usual commercial distillation test 100 c.c. of naphtha are dis-
tilled directly from an Engler distilling flask, in the manner described
^ Cf. B. Blount, " The Composition of Commercial Petrols," The Incorporated Institution of
Automobile Engineers, loth March, 1909 ; J. Soc. Chem, Ind,, 1909, 28, 419.
Ill £
18
MINERAL OILS
on p. 6 for crude oil, and the fractions are collected for each interval
of lo"). The point at which the first drop of distillate falls from the
condenser is taken as the commencement of boiling, and the moment
at which the bottom of the distillation flask is just dry is taken as the
end point.
If the barometric pressure is not normal, this must be taken into
account in stating the boiling points and quantities of liquid in the suc-
cessive fractions.^ The receiver is changed, in such a case, not exactly
at each round lo", but at a slightly higher or lower temperature based
on the deviation of the boiling point of water from the normal at the
prevailing barometric pressure. R. Kissling has shown that this
correction is sufficiently accurate for all technical purposes. Such a
correction is to be applied whenever the atmospheric pressure deviates
by more than 5 mm. from 760 mm. To correct automatically for
differences of pressure, Fuss has suggested the use of a thermometer
with an adjustable scale, the 100" point being adjusted according to the
boiling point of water under the given barometric pressure; the ther-
mometer is divided into ^ degrees, so that ^V degrees can be estimated.
IV. FLASHING POINT.
As the vapour of petroleum naphtha (boiling as described above)
ignites well below o^, the determination of the flashing point in the
Abel apparatus requires special precau-
tions, and should aim at keeping the
temperature well below freezing point.
The container of the Abel apparatus
(Fig. 7) is therefore placed in a cylindrical
metal pot /;, about 60 mm. high and 90 mm.
wide, filled with alcohol. The pot is placed
in a larger vessel r, about 'jo mm. high
and 160 mm. wide, also filled with alcohol,
and well insulated by felt. The cooling
below o" is effected by introducing solid
carbonic acid into the alcohol as required.
The ignition mechanism should be inserted, not from the beginning,
but immediately before the actual test commences ; otherwise the flame
may go out during the test, owing to clogging of the wick by cold.
Moreover, the spring which governs the insertion of the ignition flame
is apt to work badly at low temperatures, and must be helped by
frequently turning the knob on the lid of the igniter. A temperature
Fio. 7.
* Cf. Ubbelohde, Z. angnv. Chtm., 1906, 19, 1 155 ; and R. Kissling, Client. Zeit., 1908,32,
695.
RISK OF EXPLOSION
19
of —50° to —60° having been reached, the container a is taken out
bodily, and wrapped carefully in a cloth ; the test is then carried out
in the usual manner. After the flash test has been made, the ignition
point may be determined ; for this purpose the lid is taken off.
The following flashing points and ignition points of some naphtha
fractions are given by Holde ^ : —
B.P. 50'-60^ (30'-7S°
Flashing point below -58° -39°
Ignition point ... ~34°
70°.88°
SOMOO-
SOMIS-
100°-150
-45"
-22°
-22°
+ 10°
-42°
...
-19°
+ 16''
V. RISK OF EXPLOSION.
In gas engines, explosive mixtures of gas and air are purposely
generated. It is to be borne in mind that combustible gases become
explosive only when they are mixed with air, oxygen, or other gases
which exercise an oxidising action. However, not every mixture of a
combustible and an oxidising gas yields an explosive mixture, proper
proportions of the two being required. Hence, there is a limited range
of composition, within which explosion can occur. H. Bunte ^ has
determined the explosive limits for various mixtures of air and gas
(Table 5) in a gas-burette of 19 mm. diameter, the gas being ignited
by a powerful electric spark.
Table 5.
Gas.
Percentage of combustible gas in tlie mixture.
No explosion.
Limits of explosion.
No explosion.
1. Carbon monoxide .
16-4
16-6 to 74-8
75-1
2. Water gas
12-3
12-5 „ 66-6
G6-9
3. Hydrogen
9-4
9-5 „ 66-3
66-5
4. Acetylene
3-2
3-5 ,. 55-2
52-4
5. Coal gas
7-8
8-0 „ 19-0
19-2
6. Ethylene
4-0
4-2 „ 14-5
14-7
7. Alcohol
3-9
4-0 „ 13-6
13-7
8. Methane
6-0
6-2 „ 12-7
12-9
9. F.ther .
2-6
2-9 „ 7-5
7-9
10. Benzene
2-6
2-7 „ t)-3
6-7
11. Pentane
2-3
2-5 „ 4-8
5-0
12. Petroleum spirit .
2-3
2-5 „ 4-8
5-0
These experiments were carried out under strictly comparable
conditions, as the range of the limits of explosion depends not only on
the nature of the gas, but also on the diameter of the tube, the method
of ignition, the pressure, and the temperature. The influence of the
last factor was determined in the case of carbon monoxide. Whereas
' Mill. k. MaUrialpriif., 1899, p. 70. - J. Gasbekucht, 1901, 44, 835.
20
MINERAL OILS
the lower limit for this gas at the ordinary temperature is i6-6 per cent.,
it sinks to 14-2 per cent, at 400"", and to 7-4 per cent, at 600".
It is seen from the Table that the limits of explosion for petroleum
spirit lie very close together, the upper limit being onl)' 5 per cent,
of the vapour. On the other hand, it must not be overlooked that
very small quantities of petroleum spirit are sufficient to cause an
explosion.
It is advantageous, instead of employing Bunte's method of deter-
mination, to allow a certain quantity of vapour of petroleum spirit to
evaporate into a gasometer holding a known volume of air, and then to
draw the mixture into a Hempel explosion pipette over mercury for
the ignition.
VI. HEAT OF COMBUSTION OF NAPHTHA (PETROL).
Since benzine has come into use for motors, especially for auto-
mobiles {cf. also p. 45), the determination of its heat of combustion has
become of importance, as the value of an oil depends upon its calori-
metric effect. The determination is carried out in a calorimetric bomb
(Berthclot's, Mahler's, Krocker's) placed in a water calorimeter, with a
known quantity of oil and compressed pure oxygen, the ignition being
effected electrically. The heat evolved by the combustion is measured
by the rise in temperature of the calorimeter. The apparatu-s and
the method of determination are described in the section on " Fuel,"
Vol. I., pp. 254 ct seq.
The heats of combustion of benzine and burning oils are given in
Table 6 in comparison with those of some other fuels.
Table 6.
Heating material.
Heat of combustion.
Naphtha
Petroleum .....
Benzene
Motor Alcohol ....
Anthracite
Coal
Lignite (air-dry)
11,160 to 11,225
11,000 „ 11,100
10,038
5,940
8,000
7,000 to 7,500
4,500 „ 5,000
VII. AROMATIC HYDROCARBONS.
I. Qualitative Dctectio?t. — Asphalt, free from mineral matter, is finely
powdered and thoroughly extracted with petroleum spirit of sp. gr.
NAPHTHA 21
0-70-07 1. A pinch of this is placed in a small filter, and the naphtha under
examination is poured on to it. The filtrate is collected in a test tube ;
if it be colourless, benzene is absent, whereas if it show a yellow or
brown tinge, the presence of benzene or toluene is indicated. This test,
which is based on the solubility of asphalt in benzene, is sensitive
enough to indicate an admixture of from 5-10 per cent, of aromatic
hydrocarbons.
2. Quantitative Determination. — The method proposed by G. Kramer
and W. Bottcher,^ and based on the absorption of aromatic and olefinic
hydrocarbons by sulphuric acid of sp. gr. 1-84 at 15° (prepared by
mixing 20 vols, of fuming with 80 of ordinary concentrated acid), gives
only approximately correct results.
VIII. OIL OF TURPENTINE (AMERICAN, RUSSIAN).
Oil of turpentine is best detected by determining the boiling point
the specific gravity, and the iodine value of the sample, or if need be of
the fractions. American oil of turpentine yields 90 per cent, of distillate
boiling from i55°-i65°, has the sp. gr. 0-865 at i5°-5, and an iodine
value of about 400.
Russian oil of turpentine ("Kienoel") yields 90 per cent, of distillate
boiling from i6o°-i85°, has the sp. gr. 0-8610, and an iodine value of
about 320. Benzine, on the other hand, has a much lower specific
gravity and a very low iodine value - (if any).
IX. DEGREE OF PURIFICATION.
Commercial naphtha is more or less deep yellowish. Refined
naphtha should be absolutely water-white, should impart no colour to
concentrated sulphuric acid on shaking with it, and should yield no
acid or other impurities to boiling distilled water.
X. SOLUBILITY IN ABSOLUTE ALCOHOL.
The naphtha fractions are completely soluble in absolute alcohol ;
naphtha is not miscible with 90 per cent, alcohol.
XI. PETROLEUM SPIRIT (NAPHTHA OR "NORMAL BENZINE").
As benzines used for the determination of "asphaltic substances" in
dark mineral oils yield very different results according to their individual
boiling points, the German " Verband fiir die Materialpriifungen der
^ Gewerbejleiss, 1887.
- Cf. Lewkowitsch, Chem. Technology of Oils, Fats, and Waxes, vol. iii., p. 125.
22 MINERAL OILS
Technik" introduced in 1903 a "normal benzine" for these tests. This
benzine is supplied solely by the firm of C. A. F. Kahlbaum, Berlin,
under the control of the Royal Materialpriifungsamt at Gross-Lichter-
felde near Berlin. This normal benzine must answer the following
requirements : —
Sp. gr. at 15°, 0-695-0-705 ; extreme limits of boiling point 65^-95°
(determined by continuous distillation from a small flask with a three-
bulb Le Bel-Henninger fractionating column). It must not contain
more than 2 per cent, of substances which dissolve in a mixture of 80
parts of concentrated and 20 parts of fuming sulphuric acid.
XII. PETROLEUM SPIRIT FOR VARNISHES AND OIL OF
TURPENTINE SUBSTITUTES.
The identification of pure oil of turpentine substitutes, such as
"Kienol" (see above, p. 21), perchlorethylene, etc., presents no
analytical difficulties.^
The substitutes used in the manufacture of varnishes, sold in this
country as " White Spirit," have, as a rule, a flashing point above 23°
(73° F.), mostly at 26''-7 (80° F.), evaporate as nearly as possible at
the same rate as does genuine oil of turpentine, yield 90 per cent, of
distillate up to 140", have a sp. gr. of about 0-785, and are characterised
by a mild odour.
The rate of evaporation is determined by a comparative tes.t with
pure oil of turpentine, the liquids being evaporated in a platinum dish
on a boiling water-bath. Pure oil of turpentine may leave from 1-5-2
per cent, of a solid residue ; the substitute, however, should leave no
residue. A convenient comparative test, which can be carried out in
the cold, is to moisten a strip of filter paper with an equal number
of drops of turpentine and the benzine under examination, and to
observe the time which elapses before the liquid has evaporated off
completely.
Many quantitative methods have been proposed for the determina-
tion of benzine in turpentine substitutes,- but these have all been
rejected on account of inaccuracy. The method which has proved
itself the best is J. Marcusson's^ modification of Burton's method, in
which fuming nitric acid is allowed to act on 10 c.c. of the oil at — lo^
Turpentine and " Kienole " pass completely into solution under this
treatment, or give at most 1-5 per cent, of precipitate. A defect in the
original method was that certain components of the benzines, viz.,
1 Cf. Lewkowitsch, loc. cit.
2 QC H. E. Armstrong, /. Soc. Chem. Ind., 1882, I, 478 ; Richardson and Bowen, /. Soc.
Chem. /luL, 1908, 27, 613 ; Burton, Amer. Chem. /., 1890, 12, I02 ; Allen, Chem. Znitr., 1890,
II., 125.
'■^ MilUilungen, 1908, p. 157 ; J. Soc. C/um. /mi., 1909, 28. 1096.
BURNING OIL (KEROSENE)
23
aromatic and olefinic hydrocarbons, also pass into solution, giving rise
to low results in the determination of the benzines. In the subjoined
Table a series of results obtained by this method for oil of turpentine
mixed with Galician and Sumatra benzines are given.
Table
7-
Source of benzine used.
Percentage
of benzine.
Insol.
in
nitric
acid.
Extract from nitric acid
solution (freed from acid).
Benzine
content
found.
Difference
between
found
and true.
Per cent.
g.
c.c.
Per cent.
on
original oil.
Per cent.
Percentage.
Sumatra (heavy)
„ (light) .
80
80
49-0
57-5
3-82
2-40
3-32
2-10
33-2
21-0
82-2
78-5
+ 2-2
-1-5
(heavy) .
Galicia .
60
40
33-0
30-0
2-80
ro2
2-44
0-90
24-4
9-0
57-4
39-0
-2-6
-1-0
20
11-0
1-03
0-90
9-0
20-0
+ 0-0
Sumatra (heavy) .
10
4-0
0-79
0-70
7-0
11-0
+ 1-0
Marcusson's method also gives valuable information as to the source
of the benzine present. If the range of boiling point is ioo°-i8o° and
the specific gravity of the portion insoluble in nitric acid is 072-0-73,
the benzine is probably of American origin ; a specific gravity of
o- 74-0-75 indicates Galician or Roumanian benzine ; 0-76-0-77, Indian ;
0-78, Russian. A second criterion is the content of substances soluble
in nitric acid. Taking, as before, a boiling point from ioo°-i8o°, the
percentage of soluble matter calculated on the total benzine is, in the
case of American and Russian benzines, 8-10 per cent. ; in Galician and
Roumanian, 15-20 per cent. ; in Indian, 22-40 per cent.
A modification of Armstrong's polymerisation method for this
estimation has been recently recommended by R. S. Morrell.^
C— BURNING OIL (KEROSENE).
I. COLOUR.
Good burning oil (Kerosene, paraffin oil, etc.) boiling between 150°
and 300° and prepared by treating the crude oil with sulphuric acid,
should be clear, transparent, and, at most, of a faintly yellow tint. The
higher grades, such as " water-white," are colourless. On exposure to
sunlight all burning oils become slightly discoloured, without however
suffering to any extent in their illuminating properties. For commercial
purposes burning oil is classified according to colour. Standardising
1 J. Soc. Chetn, Ind., 1910, 29, 241.
24:
MINERAL OILS
colorimeters, which enable the grade of an oil to be determined, have
been devised by A. Wilson, and by C. Stammer.
I. IVt/son's Colorimeter consists of a box, the lid of which may be
clamped at an)' angle and acts as a stand for two brass tubes b (Figs.
8 and 9), 16 in. long, holding the oil and the standard glasses
respectively. Both tubes are closed by thin glass plates fixed in
screw-caps. A mirror at the bottom of the lid reflects the light through
the tubes and through a pair of prisms into the eye-piece. The field, as
seen through the eye-piece, is divided by a sharp line which allows of
the comparison of the two halves of the field, which are tinted
respectively with the colour of the oil and that of the standard. A
series of four standard glasses is supplied with each colorimeter,
corresponding, in ascending order of depth, to the four commercial
grades — water-white, superfine white, prime white, and standard
white.
Fio. 8.
Fig. 9.
In making a determination, one of the tubes is filled with oil, the
other remaining empty. The tubes are first fixed in position ; one-half
of the field seen through the eye-piece will now, of course, be darker
than the other. Standard glasses are then inserted in the empty tube,
until both halves of the field have approximately the same tint. The
grade of the oil is thus fixed.
It is very rare that an oil corresponds exactly to one of the standard
glasses. Since, however, these are the only recognised standards, if the
colour of an oil should lie between say No. 2 and No. 3 standard, the
oil is classified according to the darker tint, i.e. as No. 3. In Baku the
common practice is to express the grade in fractions of the standard
number.
The colour of the burning oil manufactured at Baku generally lies
between the standard numbers 2 and 3. Intermediate fractions are
determined as follows : — Standard glass No. 2 is placed over the tube
containing the oil, and No. 3 over the empty tube. If the two halves
of the field be found to be equalised, then the grade of the oil is 2\.
KEROSENE. COLOUR
25
If under these conditions the oil appears too dark, the grade 2f is
assigned to it ; if too h'ght, the grade 2j. Again if glass No. i on the
filled tube compensates No. 3 on the empty one, the oil is graded as
No. 21
2. Stammers Colorimeter. — This instrument has the advantage over
that of Wilson that it allows of the variation of the length of the column
of oil measured, whereby the shade
of colour can be more accurately de-
fined. It is largely used at Baku.
The construction of the apparatus
is shown diagrammatically in Fig. 10.
A fixed tube ^, on which is placed a
standard glass plate ti is arranged side
by side with a cylinder c in which the
oil is placed ; this cylinder can be
moved up and down by means of the
hand-wheel k, whereby the length of
the column of oil under comparison is
varied at will. Both z and c are closed
at the bottom by thin glass plates
through which the light reflected from
the mirror p reaches the eye-piece 0.
The length of the column of oil is
adjusted until both fields, as seen
through the eye-piece, have the same
depth of tint, and this length is
measured on the scale m.
The use of the single glass standard
was found by Boverton Redwood ^ to
be open to objection, as the sensitive-
ness of the test was much impaired in
cases in which the column of oil had
to be greatly shortened for the com-
parison. Modifications introduced by R. Redwood have overcome this
defect. The space between any two of the four commercial shades is
divided into ten equal parts, so that if the colour, for instance, of a
sample is midway between " water-white " and " superfine white " it
would be indicated by the figure 1-5.
The following Table gives the relations between grade number by
Wilson's colorimeter, and height of column in Stammer's colorimeter.
The figures in the third column, in the case of whole grade num.bers,
were arrived at by direct experiment, and in the case of the remaining
numbers, by calculation.
1 Cf. Petroleum and its Products^ 3rd ed., 191 3, vol. ii , p. 215.
Fig. 10.
26
MINERAL OILS
Standard white
. No
4
?o
mm.
Prime white .
. No. 2l
172
>)
)i
3^
68
11
Superfine white
• » 2
199
Prime white
5)
3
86-5
>)
)»
• „ li
255
>i
))
24^
H5
>)
Water-white .
• ., I
310
»»
»>
2^
143
)i
inm.
According to the rules of the Baku section of the Imperial Russian
Technical Society, the colour of a burning oil is by no means the only
factor determining its degree of purity or its behaviour in burning.
As, however, burning oil is bought and sold very largely on a basis of
colour, it was regarded as desirable to standarise the colorimetric tests
employed. Since the tints of the standard glasses in the above-described
colorimeters are found to vary a little, a minute comparison of grades,
Wilson numbers, and Stammer columns, was made by the Baku
section with a readily reproducible standard, viz., potassium chromate
dissolved in acidulated water in a column 404-6 mm. high. The results
of these tests are given in the following Table : —
Table 8.
Grade.
Number.
Percentage
strength of
Column of oil
In mm.
K2Cr04 solution.
Water-white .
1-0
•000272
957^9
1-1
•000309
843-2
11
91 * *
1-2
•000346
753-1
f 1 * *
1-3
•000384
680-3
9) * *
1-4
•000421
618^9
11 • •
1-5
•000458
568-4
tv • •
1-6
•000495
526-4
!• * *
1-7
•000532
489-8
1-8
•OOOf.70
557-1
11 • •
1-9
•000607
429-3
Superfine white
2-0
•000644
404-6
11 * *
2-1
•000836
294-1
If • *
2-2
•001129
230-8
2-25
•001220
208-5
2-3
•001371
191-1
11 * •
2-4
•001614
161-4
>1 ■ •
2-5
•001856
140-4
11 * *
2-6
•002098
124-2
11 • •
2-7
•002341
111-3
11 • •
2-75
•002462
105-8
11 " •
2-8
•002583
100*9
11 • •
2-9
•002826
92-2
Prime white .
3-0
•003068
84-9
»1 • *
3-1
•003325
78-4
11 * *
3-2
•003581
72-8
11 • "
3-3
•003838
67-9
11 ' •
3-4
•004094
63-6
11 • *
3-5
•004351
59-9
1 1 • •
3-6
•004608
56-5
11 * "
3-7
•004864
53-5
)1 • •
3-8
•005121
50-9
n ' •
3-9
•005377
48-5
Standard white
4-0
•005634
46-2
It will be observed that the scale of solutions of potassium chromate
is so designed that each interval between two standard commercial
grades is divided into tenths. Thus the difference for each unit
KEROSENE. SPECIFIC GRAVITY
27
is -000037 per cent, chromate between water-white and superfine white,
•0000242 per cent, between superfine white and prime white, and so on.
The colour of any given oil can be stated in terms of this scale by
comparing it in a Stammer colorimeter with a standardised glass
having the tint of a 404-6 mm. column of superfine white oil. Superfine
white is the most suitable standard, because with it the inevitable
qualitative differences of colour are reduced to a minimum. An oil
paler than superfine white must be compared with a water-white glass,
since columns longer than 404-6 mm. cannot be examined.
When comparison is made with a glass corresponding to water-
white, the following Table gives the requisite data : —
Table 9.
Grade.
Number.
Percentage
strength of
Column of oil
K2Cr04 solution.
Water-white .
1-0
•000272
404-6
1-1
•000309
356-2
1-2
•000346
318-1
1-3
•000384
286-6
1-4
•000421
261-4
1^5
•000458
240-3
1^6
•000495
222-3
1-7
•000532
206-9
1^8
•000570
193-1
1^9
-000607
181-3
Superfine white
2^0
-000644
170-9
Colorimeter glasses which have not quite the correct standard colour
are themselves standardised by comparison with potassium chromate
solutions. The amount of divergence having been ascertained, the
proper correction is applied in the fourth column of the Tables, when
such a glass is used.
II. SPECIFIC GRAVITY.
The specific gravity is, as a rule, expressed for a temperature of 15°
compared with water at 4".
The corrections to be applied for temperatures differing from 15°
are given in the following Table prepared by Mendelejeff : —
Table 10.
Range of sp. gr.
Correction for 1°.
0-760 to 0-780
0-780 „ 0-800
0-800 „ 0-810
0-810 „ 0-820
0-820 „ 0-830
0-830 ,, 0-840
0-840 „ 0-850
0-850 „ 0-860
-000790
•000780
•000770
•000760
•000750
•000740
•000720
•000710
28 MINERAL OILS
Petroleum increases perceptibly in specific gravity on keeping for a
long time, even in stoppered bottles; Engler^ ascribes this as being
due to polymerisation.
in. VISCOSITY.
This, if required, may be determined by means of Redwood's visco-
meter, which is fully described in the section on " Lubricating Oils "
(p. 66).
IV. SOLIDIFYING POINT.
Burning oils, if likely to be used in open places, must remain liquid
below the freezing point of water. The test is carried out as described
in the section on " Lubricants" (p. 70).
American petroleum separates particles of paraffin at - 10° unless it
has been carefully distilled, whereas Russian petroleum remains
perfectly clear at — 20°.
V. FLASHING POINT.
The flashing point of a mineral oil is that temperature at which it
begins to evolve inflammable vapour in sufficient quantity for a
momentary " flash" to occur on the application of a flame. The testing
of the flashing point as a safeguard against the presence of very
volatile hydrocarbons in burning oils has been made the basis of
legislation in regard to petroleum. The test is an arbitrary one, and
various forms of instruments have been adopted in different countries
for legislative purposes.
The first Petroleum Act in this country was passed in 1862, but
remained practically inoperative, as no method of testing was prescribed.
Subsequent Acts were passed in 1868 and 1871, in which an "open
test " was prescribed. Petroleum was defined for the purposes of these
Acts as "any Rock oil, Rangoon oil, Burma oil, oil made from
petroleum, coal, schist, shale, peat, or other bituminous substance, or
any products of petroleum, or any of the above-mentioned oils which
gives off an inflammable vapour at a temperature of less than i(X)° F,"
In 1879 a further Petroleum Act was passed, as the result of investiga-
tions by Sir Frederick Abel, in which the " closed test," now known as
the Abel test, was adopted. The result of a large number of experi-
ments on the difference between the flashing points with the open-cup
instrument and with Abel's closed tester gave a mean value of 27' F., in
accordance with which the new standard of temperature was fixed at
73° F. (22'.8C.). This Act of 1879, in conjunction with that of 1871,
is still in force. The specification of the test apparatus and the details
for applying the test are given below. Every apparatus in use for
official purposes must be standardised by the Board of Trade.
Ber., 1900, 33, 7.
KEROSENE. FLASHING POINT
29
The Abel Petroleum Test Apparatus.
Specification of the Test Apparatus. — The following is a descrip-
tion of the details of the apparatus, Fig. 1 1 : — The oil cup consists of a
cylindrical vessel 2 in. diameter, 2j% in. height (internal), with outward
projecting rim yV i"- wide, f in. from the top, and if in. from the
bottom of the cup. It is made of gun metal or brass (17 B.W.G.)
tinned inside. A bracket, consisting of a short stout piece of wire bent
upwards and terminating in a point, is fixed to the inside of the cup to
serve as a gauge. The distance of the
point from the bottom of the cup is i^ in.
The cup is provided with a close-fitting
overlapping cover made of brass (22
B.W.G.), which carries the thermometer
and test lamp. The latter is suspended
from two supports from the side by means
of trunnions upon which it may be made
to oscillate ; it is provided with a spout,
the mouth of which is tV ^i^- i^"* diameter.
The socket which is to hold the thermo-
meter is fixed at such an angle and its
length is so adjusted that the bulb of the
thermometer when inserted to its full
depth shall be li in. below the centre of
the lid.
The cover is provided with three square
holes, one in the centre, j% in. by yV ^"-j
and two smaller ones, j\ in. by y%- in.,
close to the sides and opposite each other.
These three holes may be closed and
uncovered by means of a slide moving in
grooves, and having perforations corres-
ponding to those on the lid.
In moving the slide so as to uncover
the holes, the oscillating lamp is caught
by a pin fixed in the slide, and tilted in
such a way as to bring the end of the spout just below the surface
of the lid. Upon the slide being pushed back so as to cover the holes,
the lamp returns to its original position.
Upon the cover, in front of and in line with the mouth of the lamp,
is fixed a white bead, the dimensions of which represent the size of the
test flame to be used.
The bath or heated vessel consists of two flat-bottomed copper
cylinders (24 B.W.G.), an inner one of 3 in. diameter and 2| in. height,
30 MINERAL OILS
and an outer one of 5^ in. diameter and 5^ in. height ; they are soldered
to a circular copper plate (20 B.W.G.) perforated in the centre, which
forms the top of the bath, in such a manner as to enclose the space
between the two cylinders, but leaving access to the inner cylinder.
The top of the bath projects both outwards and inwards about '^ in. ;
that is, its diameter is about 4 in. greater than that of the body of the
bath, while the diameter of the circular opening in the centre is about
the same amount less than that of the inner copper cylinder. To the
inner projection of the top is fastened, by six small screws, a flat ring of
ebonite, the screws being sunk below the surface of the ebonite,
to avoid metallic contact between the bath and the oil cup. The
exact distance between the sides and bottom of the bath and of the oil
lamp is one-half of an inch. A split socket similar to that on the cover
of the oil cup, but set at a right angle, allows a thermometer to be
inserted into the space between the two cylinders. The bath is further
provided with a funnel, an overflow pipe, and two loop handles.
The bath rests upon a cast-iron tripod stand, to the ring of which is
attached a copper cylinder or jacket (24 B.W.G.) flanged at the top, and
of such dimensions that the bath, while firmly resting on the iron ring,
just touches with its projecting top the inward-turned flange. The
diameter of this outer jacket is 6h in. One of the three legs of the
stand serves as support for the spirit lamp attached to it by means of a
small swing bracket. The distance of the wick holder from the bottom
of the bath is i in.
Two thermometers are provided with the apparatus, the one for
ascertaining the temperature of the bath, the other for determining the
flashing point. The thermometer for ascertaining the temperature of
the water has a long bulb and a space at the top. Its range is from
about 90''-r9o'F. The scale (in degrees Fahrenheit) is marked on
an ivory back fastened to the tube in the usual way. It is fitted
with a metal collar, fitting the socket, and the part of the tube below
the scale should have a length of about 3^ in. measured from the lower end
of the scale to the end of the bulb. The thermometer for ascertaining
the temperature of the oil is fitted with a collar and ivory scale in a
similar manner to the one described. It has a round bulb, a space at
the top, and ranges from about 55 -150" F.; it measures from end of
ivory back to bulb 2\ in.
Note. — A model apparatus is deposited at the Weights and
Measures Department of the Board of Trade.
Directions for applying the Flashing Test. — i. The test apparatus
is to be placed for use in a position where it is not exposed to
currents of air or draughts.
2. The heating vessel or water-bath is filled by pouring water into
the funnel until it begins to flow out at the spout of the vessel. The
ABEL FLASHING POINT APPARATUS 31
temperature of the water at the commencement of the test is to be
1 30° F., and this is attained in the first instance either by mixing hot
and cold water in the bath, or in a vessel from which the bath is filled,
until the thermometer which is provided for testing the temperature of
the water gives the proper indication ; or by heating the water with the
spirit lamp (which is attached to the stand of the apparatus) until the
required temperature is indicated.
If the water has been heated too highly, it is easily reduced to
I30°F. by pouring in cold water, little by little (to replace a portion of
the warm water), until the thermometer gives the proper reading.
When a test has been completed, this water-bath is again raised to
I30°F. by placing the lamp underneath, and the result is readily
obtained while the petroleum cup is being emptied, cooled, and refilled
with a fresh sample to be tested. The lamp is then turned on its swivel
from under the apparatus, and the next test is proceeded with.
3. The test lamp is prepared for use by fitting it with a piece of flat
plaited candle wick, and filling it with colza or rape oil up to the lower
edge of the opening of the spout or wick tube. The lamp is trimmed
so that when lighted it gives a flame of about 0-15 in. diameter, and this
size of flame, which is represented by the projecting white bead on the
cover of the oil cup, is readily maintained by simple manipulation from
time to time with a small wire trimmer.
When gas is available it may be conveniently used in place of the
little oil lamp, and for this purpose a test- flame arrangement for use
with gas may be substituted for the lamp.
4. The bath having been raised to the proper temperature, the oil
to be tested is introduced into the petroleum cup, being poured in
slowly until the level of the liquid just reaches the point of the gauge
which is fixed in the cup. In warm weather the temperature of the
room in which the samples to be tested have been kept should be
observed in the first instance, and if it exceeds 65° F. the samples to
be tested should be cooled down (to about 60° F.) by immersing the
bottles containing them in cold water, or by any other convenient
method. The lid of the cup, with the slide closed, is then put on, and
the cup is placed into the bath or heating vessel. The thermometer in
the lid of the cup has been adjusted so as to have its bulb just immersed
in the liquid, and its position is not under any circumstances to be altered.
When the cup has been placed in the proper position, the scale of the
thermometer faces the operator.
5. The test lamp is then placed in position upon the lid of the cup,
the lead line or pendulum, which has been fixed in a convenient
position in front of the operator, is set in motion, and the rise of the
thermometer in the petroleum cup is watched. When the temperature
has reached about 66" F. the operation of testing is to be commenced.
32
MINERAL OILS
the test flame being applied once for every rise of one degree, in the
following manner : —
The slide is slowly drawn open while the pendulum performs three
oscillations, and is closed during the fourth oscillation.
Note. — If it is desired to employ the test apparatus to determine
the flashing points of oil of very low volatility, the mode of proceeding
is to be modified as follows : —
The air chamber which surrounds the cup is filled with cold water
to a depth of ih in., and the heating vessel or water-bath is filled as
usual, but also with cold water. The
lamp is then placed under the ap-
paratus and kept there during the
entire operation. If a very heavy
oil is being dealt with the operation
may be commenced with water pre-
viously heated to 120', instead of
with cold water.
Effects of Variation in Baro-
metric Pressure. — The results ob-
tained with the Abel apparatus vary
with the barometric pressure, the
difference in the flashing point
amounting to o^'-6t,6 F. (0^-30 C.) for
each 10 mm. difference in pressure.
A Table of corrections, given on
p. 37, is in use in Germany in con-
nection with the Abel-Pensky instru-
ment ; no corrections are prescribed
by the Petroleum Act in this
country.
Effect of a Tropical Climate- — The effect of a tropical climate on
the liberation of vapour causes a lowering of the flashing point. In-
vestigations by F. Abel and Boverton Redwood ^ have shown that this
source of error in the determination of the flashing point may be
overcome by commencing the test many degrees below the flashing
point, so that the vapour is withdrawn by the current of air created by
the test flame, in successive quantities too small to cause a flash
before volatilisation of the oil begins. With this modification, which is
embodied in the Indian Petroleum Act, 1899 (as modified to 1st Nov,
1903), the results obtained at a tropical temperature agree very closely
with those obtained in a temperate climate.- The Act prescribes the
Pensky modification of the Abel apparatus (p. 33) for carrying out the
Fig. 12.
test.
J C/iat/i. A'fws, 1884, 49, 196.
- C/. Redwood, Petroleum and its Products, vol. ii-, pp. 231-23S.
ABEL-PENSKY APPARATUS
33
Petroleum Mixtures. — Since mixtures of petroleum with other
substances present similar dangers to petroleum without admixture,
an Order in Council^ was introduced in 1907 in regard to such
mixtures. The prescribed apparatus (Fig. 12) differs from the Abel
apparatus described above in the addition of a stirrer, to equalise
the temperature throughout the sample during the test, and must be
used for all viscous and sedimentary mixtures.
The Abel-Pensky Petroleum Test Apparatus.
This modification of the Abel apparatus is provided with a clock--
work arrangement for the removal of the slide and the application of the
Fia. 13.
test-flame, whereby greater uniformity is secured in the tests and the
liability to the personal error introduced by the method of applying the
1 Statutory Rules and Orders, 1907, No. 483. Published by Wyman & Sons, Fetter Lane,
London, E.G.
Ill c
34
MINERAL OILS
test-flame is considerably reduced. It has been adopted as the
standard instrument for legislative purposes in Germany, Russia, and
in India.
The apparatus (Fig. 13) consists of a water-bath W, an oil-container
G, a lid fitted with a thermometer, and an igniting device, operated by
a special mechanism. In the lid of the water-bath are fixed a funnel C,
an exit-pipe (not shown in the figure), and a thermometer /.,. A hollow
copper vessel dips into the water-bath. This acts as an air-jacket to the
container, and has an ebonite-lined neck. The container G, which fits
into this neck, is tinned internally and provided with a grip //j, up to the
level of which it is filled with the oil to be tested. The lid of G carries
a thermometer /j, and on it lies the flat metal slide-valve S, which is
actuated by the clockwork mechanism T, and is pierced with a series
of holes corresponding with holes in the lid of G ; at one end of the
stroke G is thus closed off, and at the other end it communicates with
the open air through the holes referred to.
To set the clockwork in action, the screw b is turned to the right as
far as it will go. On depressing the lever //, the slide-valve is set in
motion. At the same time the small lamp <?, which oscillates on a
horizontal swivel, is made to dip downwards; the lamp has a spout d,
which carries a wick at which a tiny flame is kept burning. Matters
are so adjusted that this flame dips into the upper part of G (which
contains a mixture of oil vapours and air) for two seconds at the point
where the openings of the slide-valve are over the openings of G. '
To determine the flashing point the oil is introduced into the
container by means of a pipette, and is cooled, before the ignition
mechanism is brought into play, to 2° below the lowest possible
limit of the flashing point. The initial adjustment of temperature is
effected before G is placed in the water-bath. Care should be taken
that no oil lodges on the inside of G above the level of//.
The relation between the barometric pressure and the temperature
at which testing should begin is shown by the following Table : —
Table 11.
Barometric pressure.
Initial temperature.
From 685 to 695 mm.
+ 14-0°C.
Above 695 „ 705 „
14-5
,1 705 „ 715 „
15-0
,1 715 „ 7'25 „
15-5
11 725 „ 735 „
16-0
„ 735 „ 745 „
16-0
11 745 „ 755 „
16-5
„ 755 „ 765 „
17-0
„ 765 ,, 775 „
17-0
1, 775 „ 785 „
17-5
ABEL-PENSKY APPARATUS 35
The ignition flame, which is fed, through a cotton wick, from the
petroleum reservoir de, is lighted when the temperature of the water-bath
has reached 54°-55° C. (i29°-i3i° F.), and is set in motion by winding
up b and depressing li ; at the same time the spirit lamp L is
extinguished. The test is made at \° intervals. A white bead let
into the lid of the tester indicates the size to which the flame should
be adjusted.
As the flashing point is approached, the ignition flame is observed to
grow larger through the formation of a halo of light surrounding it.
The true flashing point, however, is not reached until a momentary blue
flame plays over the whole empty space above the oil. A further
condition is that the ignition flame shall not be blown out by this
occurrence, as often happens in the first flashings. The temperature at
which definite flashing sets in is read off at the thermometer t^.
The test is repeated with a fresh portion of the oil, and if the result
of the second test does not differ by more than o°-5 from the first, the
mean of the two temperatures is taken as the flashing point; should
the two readings differ by i° or more, a third test is made, and if the
maximum difference between the three readings does not exceed i°-5,
the average is takeif.
The minimum flashing point prescribed in Germany is 21° C.
(69''-8 F.) at 760 mm. pressure. The apparent flashing points must be
corrected for pressure in accordance with Table 12 (p. 37), in which
flashing points from i5°-S-25°-9 are tabulated under pressures from
650-785 mm. ; the flashing points at the normal pressure are given in
the column between the two thick lines, and the corresponding flashing
points at other pressures are given in the same horizontal line.
Other Apparatus for testing the Flashing Point of Petroleum.
Several other forms of apparatus have been devised for testing the
flashing point of petroleum.
In the State of New York an apparatus devised by A. H. Elliot is
prescribed for legal purposes, whilst in many of the other States of the
American Union the Tagliabue closed tester or cup has been adopted.
In France, Granier's automatic tester is employed officially. A full
description of these instruments together with directions for their use
and the legislative conditions governing the testing, storage, transport,
and use of petroleum and its products in the respective countries
is given in the treatise on Petroleum and its Products^ by Sir
Boverton Redwood, vol. ii., pp. 216-266, and vol. iii., pp. 1-81, 3rd
ed, 191 3.
The Pensky-Martens apparatus and that of J. Gray, both of which
are employed for determining the flashing point of the heavier mineral
oils, are described in the section on " Lubricants," pp. TJ et seq.
36 MINERAL OILS
An important series of experiments with the apparatus used for
the determination of the flashing points of illuminating oils has been
carried out by J. A. Ilarker and W. F. Higgins at the National Physical
Laboratory, for the International Commission on Petroleum Products.^
VI. IGNITION OR "FIRE" TEST.
The temperature at which an oil takes fire on the approach of a flame
and continues burning is known as the Ignition or "Fire Test." It
may be determined in Abel's apparatus by using it as an open tester.
A small flame is brought near to the surface of the oil for a second or
two after each rise of i° of temperature, or the lid of the container may
be removed after a flashing point determination and the heating
continued with periodical applications of the ignition flame.
When the flashing point of an oil is well above the prescribed
minimum, the fire test is of little interest and is only determined
in special cases.
VII. FRACTIONAL DISTILLATION.
Valuable information as to the composition and true quality
of kerosene is afforded by a fractionation test. No fixed standards
have been generally accepted, but it is usual to collect and note
the distillates below 150^ from iSo"'-200^ from 20o''-25o'', and from
25O°-3O0° ; the residue above 300° is estimated by difference. -The
measurements are usually made by volume, from which the actual
weights can be ascertained, if required, from the volumes and specific
gravities.
The apparatus used for the examination of crude petroleum can be
employed for the fractionation [cf. p. 6). Other forms of apparatus
have been described by J. Biel- and by W. Thorner.^
VIII. DEGREE OF PURIFICATION.
I. Sulphur Compounds. — The presence of sulphur compounds in
kerosene gives rise to a disagreeable smell in the products of combus-
tion and vitiates the atmosphere.
They may be estimated by burning a known weight of the oil in a
suitable lamp and passing the products of combustion through a
cylinder moistened with ammonia, as in the Gas Referees' Test for
sulphur in illuminating gas ; the sulphur dioxide formed is then oxidised
and finally weighed as barium sulphate. This test is fully described in
the section on "Illuminating Gas and Ammonia," Vol. II., Part II.,
pp. 669 et seq. As the result of an extended investigation Boverton
1 Petroleum World, 1911, pp. 303, 35 1, 397. - Dingl. polyt. J., 1884, 252, II9.
3 Chem. Zeii., 1886, 10, 528, 553, 573, 582, and 601 ; /. Soc. Chem. Ind., 18S6, $, 371.
CORRECTION OF FLASHING POINT
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38 MINERAL OILS
Redwood ^ arrived at the conclusion tliat tlie only satisfactory method
for the determination of sulphur compounds applicable to all descrip-
tions of petroleum is that of combustion in oxygen in the Mahler bomb
and subsequent estimation as barium sulphate ; he recommends that
2 g. of the sample should be burnt, and that the ox)-gen should be at a
pressure of 30 atmos. The results obtained are concordant to
the second place of decimals. A description of the Mahler bomb with
details of working is given in Vol. I., Part I., in the section on
"Fuel," p. 256.
The following method for the determination of the total sulphur in
kerosene, by means of the Parr calorimeter, has been proposed by
J. M. Sanders : - — 2-3 g. of the sample are weighed into a 100 c.c.
porcelain dish, o-oi g. of potassium bromide is dusted over the surface,
and 4 c.c. of pure fuming nitric acid are added. After the energetic
reaction has ceased, the dish is heated on the water-bath until the
liquid becomes dark brown and somewhat viscous. It is then well
mixed with 05 g. of pure light magnesia, and whilst continuing the
stirring, is heated over a small flame until the mass shows a tendency
to solidify on cooling. The granular mass thus obtained is brushed
into a Parr calorimetric bomb, any trace of oily matter left in the dish
being removed by warming with a little more magnesia. The standard
quantity (i measure full) of sodium peroxide is also introduced into
the calorimeter vessel, and after mixing, the combustion is effected in
the usual way. A few seconds after firing, the vessel should be
removed from the water in the calorimeter, and its temperature allowed
to rise, but not high enough to injure the rubber washer. After about
45 seconds, the bomb is cooled, opened, and the fused mass transferred
to 25 c.c. of water in a 200 c.c. nickel beaker, to which the washings are
also added. The solution is made slightly acid with hydrochloric acid,
filtered through cotton wool if necessary, boiled to expel chlorine,
neutralised with ammonia, acidified with hydrochloric acid, and the
sulphur precipitated as barium sulphate in the boiling solution. The
method is rapid and the results agree with those obtained by the use
of the Mahler calorimetric bomb. The construction and use of Parr's
calorimeter is described in the section on "Fuel," Vol. I., pp. 256-260.
Good burning oil should not contain more than 002 per cent, of
sulphur. Commercial oils, even those made from crude Ohio petroleum,
usuall)' fulfil this condition. E. Hcusler and M. Dennstedt^ have drawn
attention to the presence of alkyl sulphuric acids in kerosene (due to
purification by means of sulphuric acid), w^hich, in their opinion, form
sulphuric acid on combustion, and increase the tendency of the burning
oil to carbonise the lamp-wick.
' PelroUum an 1 its ProJuUs, vol. ii., p. 319. - /. Chem. Soc, 1912, lOI, 358.
* Z. attgew. Chfm., 1904, 17, 264 ; /. Soc. Chem. Ini., 1904, 23, 3 [7.
KEROSENE. CHEMICAL EXAMINATION 39
2. The Acid Test. — Properly refined petroleum shaken up with
sulphuric acid of sp. gr. 1-73 should produce no more than a very slight
yellow coloration in the acid.
The official Russian test (Baku section of the Imperial Russian
Technical Society) is as follows:^ — 100 vols, of oil are shaken for two
minutes at a temperature not exceeding 32° with 40 vols, of the above
acid in a stoppered cylinder. The liquid is transferred to a separating
funnel and the clear acid drawn off into a glass tube, in which its colour
is compared with that of an equal column of a standard solution of
Bismarck brown. To prepare the latter, 0-5 g. of Bismarck brown is
dissolved in a litre of water; a series often standards is then made up
by mixing i, 2, 3, etc., parts of this solution with 99, 98, 97, etc., parts
respectively of water, so that the darkest standard (No. 10) contains
0-005 per cent, of the dye, and the lightest (No. i) 0-0005 per cent. The
degree of purification is then expressed by the standard number to which
the sample corresponds. Aqueous solutions of Bismarck brown keep
fairly well in stoppered bottles.
It has been found in practice that the lamp oil fraction refined on
the large scale with 0-5 per cent, of sulphuric acid of sp. gr. 1-84 attains
as a rule the colour of standard No. 2. With 0-75 per cent, of acid a
slightly higher degree of purity is obtained, but no further advantage is
gained by increasing the proportion of acid. The majority of
commercial oils fall within the range of numbers 1-8. Hence, standard
No. 8 is considered the limit beyond which an oil must be regarded as
insufficiently purified.
3. Determination of Acidity. — 100 c.c. of oil dissolved in neutralised
alcohol-ether should give with one drop of decinormal alcoholic
sodium hydroxide a pink colour, phenolphthalein being used as
indicator.
4. Salts of Naphthenic and Sulphonic Acids. — The presence of
these salts, which impair the burning properties of lamp oil, are detected
by extracting the oil with dilute alkali hydroxide in the following
manner : — 300 c.c. of the oil are placed in a stoppered 500 c.c. flask with
18 c.c. of sodium hydroxide solution of sp. gr. 1-014, heated to about
70° on the water-bath, and thoroughly shaken for one minute. The
aqueous layer is separated off, cleared by filtration if necessary, and
divided into two halves. To the first half concentrated hydrochloric
acid is added, drop by drop, until the liquid is just acid to litmus or
methyl orange. To the second half exactly the same amount of acid
is added, and the solution then held immediately over small print. If
the print can be read without difficulty, the sample may be considered
free from organic salts ; if not, the ash of the oil should be determined.
A turbidity does not, however, necessarily prove that naphthenic or
1 J. Soc. Chem. Ind., 1896, 15, 678.
40 MINERAL OILS
sulphonic salts are present, since under the influence of light and
air petroleum may become sufficiently acid to give a positive indication
in this test.
5. Inorganic Residue (Ash). — A litre or half a litre of oil is
gradually introduced into a retort and distilled off until about 10 c.c.
are left behind. The residue is washed with petroleum spirit into a
tared platinum dish, evaporated or burnt off, and finally incinerated at
a low red heat Good lamp oil should not contain more than 2 mg. of
ash per litre.
6. The *' Breaking " of Petroleum. — This phenomenon is due to the
separation of sodium sulphate or sulphonates from an oil which has
been standing for a long time.
LX. UNSATURATED HYDROCARBONS.
Many petroleums, especially those from Galicia and Roumania,
contain unsaturated hydrocarbons of the olefinic and benzene series,
together with cyclic compounds consisting of partly reduced aromatic
hydrocarbons.
According to G. Kramer and W. Bottcher and recent experiments of
M. Weger,^ the quantity of unsaturated hydrocarbons as determined by
their solubility in concentrated sulphuric acid (p. 21) forms an
important indication of the quality of a burning oil.
A characteristic of these hydrocarbons is that they cause the oil to
burn with a reddish flame. Thus Borneo oil burns badly in ordinary
lamps, but after the removal of the aromatic hydrocarbons its illuminat-
ing power equals that of the best American oils.
X. BURNING QUALITY.
As a practical test of the value of an oil for illuminating purposes,
the determination of its burning quality under conditions as near
as possible to those of ordinary use is of considerable value.
The following method of carrying out this test is recommended by
Boverton Redwood.- The oil is burnt in the lamp at a constant
temperature of preferably 60° F., the wick being raised to yield the
largest flame obtainable without smoke. A camera is employed
to register variations in the size and shape of the flame during the test.
The oil-chambers of the lamps employed should be of uniform
dimensions, and the burners must be tested to ascertain that they give
similar flames with the same oils. The wicks employed are examined
in a special apparatus in which a given length of wick is arranged
to draw, by means of capillarity, an oil of known quality from a vessel
^ Chem. Ind., 1905, 28, 24 ; J. Soc. C/iem. Itid.^ 1905, 24, 126.
2 Petroleum and its Products, vol. ii., p. 21 2.
KEROSENE. ILLUMINATING POWER 41
at a fixed temperature ; the value of the wick is judged from the
quantity of oil drawn out in a certain time, and any defective portion is
rejected for testing purposes.
No general agreement has been arrived at as to the extent of
diminution that should be allowed in a flame classed as of satisfactory
burning quality,
XI. ILLUMINATING POWER.
In its physical principles the photometry of illuminating oils does
not differ from that of coal gas. A Bunsen photometer fitted with
Lummer and Brodhun's prismatic device is the best instrument to use.
A full description of the methods of photometry is given in the section
on " Illuminating Gas and Ammonia," Vol. II., Part II., pp. 697-716.
The following points are to be noted with regard to the photometry
of petroleum : 1 —
1. Constructio7i of tJie Lamp. — A great deal depends on the construc-
tion of the lamp in which the oil to be tested is burnt. The mode
of air-supply, the shape of the chimney and the height of its constriction,
and the kind of wick employed, are also important factors. It is therefore
desirable to test an oil as far as possible in a lamp resembling those in
which it is usually burnt in practice. One and the same kind of lamp
must, of course, be used for comparative tests of two or more oils.
Wicks should be dried at 105°, and soaked in the oil whilst still warm.
Lamps for testing should be provided with capacious oil-wells,
so that the level of the liquid may change as little as possible during
burning.
2. Adjustment of the Flame. — With some oils, notably the Russian
oils, the burning should be started with a comparatively small flame.
For the first five minutes the flame is allowed to reach the constriction
of the chimney, and no further ; it is then gradually raised during the
first quarter of an hour to the maximum height, that is, until flickering
or smoking ensues on increasing the height of the flame. The position
of the constriction should be such that a fully developed flame possesses
the maximum of illuminating power. For accurate photometric work
the height of the flame should be measured.
3. Photometric Measurements are not carried out until the flame has
burnt at full height for at least half an hour. In accurate work the
measurements are repeated after 4, 5, 6, etc., hours of burning.
When an oil contains an undue proportion of fractions boiling above
270°, its inferior character is only displayed after several hours' burning;
a marked diminution of its illuminating power then sets in.
4. Consumptio7i of Oil is determined by weighing the oil-reservoir
before and after a series of tests. The final results are stated as mean
^ Eger, Chem. Rev.^ 1899, p. 81.
42 MINERAL OILS
photometric intensity, total consumption of oil, and consumption per
candle-hour. The height and weight of the charred portion of the wick
are noted, as also odour, etc.
5. In special cases the residue remaining after half the oil has been
burnt is submitted to fractional distillation, and the result compared
with the fractionation of the original oil.
6. The Standard of Light in England is the Harcourt lo-candle
pentane lamp, in America the International Standard Candle (since
April 1909), in Germany the Hefner amyl acetate lamp, and in France
the Carcel lamp. A comparison of photometric standards and units is
given in the section on " Ilkiminating Gas and Ammonia," Vol. II.,
Part II., p. 703.
XII. SOLUBILITY IN ABSOLUTE ALCOHOL.
Lamp oil is soluble in twice its volume of absolute alcohol, and in
many cases in less at the ordinary temperature. According to S.
Aisinman,^ all petroleum fractions with a specific gravity up to 0835
are miscible with absolute alcohol in all proportions.
XIII. DETERMINATION OF THE ORIGIN OF A PETROLEUM.
As it is sometimes of importance to ascertain the origin of a
petroleum, various investigations have been made with this object
in view.
When a drop of bromine is added to 2-3 c.c. of American petroleum
it is decolorised almost instantaneously, whereas all other oils remain
coloured for a considerable time. Hence, several determinations have
been made both of the iodine and bromine values of petroleum. The
following iodine values were found by E. Graefe :- —
Iodine value.
Solar oil (probably a Saxo-Thuringian oil) . . 80
Russian petroleum
American petroleum
Galician petroleum
Wietze petroleum
o to 16
5-5 „ '6-5
oi
07
The following bromine values were determined by F. Utz :^ —
Source of petroleum. liromine value.
Russia ...... 072 to 08
Roumania ...... 0-56 „ o-8
Austria ...... o-88
Galicia ...... i-44
Pennsylvania ..... 2-o
Petroleum arc-light .... 2-56
1 Dingl. polyt. J., 1895, 297, 44 ; /• Soc. Chetn. hid., 1895, 14, 812.
"^ Z. angtw. Chem., I905i 18, 1 580.
3 Petroleum, 1906, 2, 43 ;/. Soc. Chevt. Ind., 1906, 25. 1 140.
TRANSFORMER OILS 43
No definite conclusions can, however, be derived from these figures,^
nor can any reliability be placed on the colour test proposed by
C. Heragen,^
Z?.— GAS OILS FROM CRUDE PETROLEUM.
The oils used for the production of gas are obtained from crude
petroleum, lignite tar, and shale oil tar. These oils are mobile liquids,
of a pale to dark yellow colour ; as regards boiling point, they are
intermediate between burning oil and lubricating oil, i.e. they boil
between 300" to 400°. They are generally soluble for the most part in
two volumes of alcohol at the ordinary temperature. Occasionally gas
oils of lower boiling point are met with, and these are, like petroleum,
easily soluble in two volumes of alcohol.
As a rule, i kg. of gas oil yields about 500-600 1, of gas, 300-400 g.
of tar, and 40-60 g. of coke.
Further details in regard to gas oils, together with a full account of
the methods employed for their examination and valuation, are given in
the section on "Illuminating Gas and Ammonia," Vol. IL, Part II.,
pp. 626-629.
^.—TRANSFORMER OILS.^
The chief requirements for oils used for high-tension electrical
transformers are freedom from moisture and mineral acids. Further,
they should exhibit little or no volatility at 100° ; hence, many
electrical works specify a flashing point of not below 160° (open test).
When kept for several hours at 100" the oil should show no signs of
decomposition ; it should remain quite liquid at the lowest winter
temperature, say — 15°, to which it may be subjected in practice.
Formerly heavy rosin oil was used for transformers on account of
Us low price, but to-day the higher petroleum fractions, more or less
identical with lubricating oils, are preferred. Thus, a good transformer
oil is specified as follows : — Petroleum distillate of viscosity (Engler)
9-8 ; sp. gr. 0-8825 ; flashing point 185° ; loss after five hours' exposure to
100° in Archbutt apparatus (see p. 74), o-o6 per cent, and after two hours
at 170°, I per cent. Some electrical works stipulate a viscosity not
exceeding 8 (Engler) at 20^
Rosin oils are considerably more volatile at 100" and 170° than
heavy or even light petroleum lubricants. After five hours at 100° rosin
oils lose 0-4 to 0-8 per cent. After two hours at 170° thick rosin oils lose
' Cf. F. Schwarz, Mitt. Kg/. Materialpriifungsamt. Gross-Lichterfelde, 1909, 27, 25 ; /. Soc.
Chem. Ind., 1909, 28, 467.
2 Chem. Zeit.y 1909, 33, 20 ; J. Soc. Chem. Inc/., 1 909, 28, 83.
^ Cf. K. Duckham, Electrician, 191 1, 67, 212 ; F. Breth, Petroleum, 191 1, 7, 290 ; A. Beringer,
Mitt. K.K. Tech. Gewerb. Museum, Vieuna, 191 1, 21, 211 ; y. Soc. Chem. Ind., 1912, 31, 1 14.
44 MINERAL OILS
5-6 to 7-4 per cent. Light lignite oils show much higher losses at ioo°,
and are therefore unsuitable for use with transformers.
Those machine oils derived from petroleum which have a flashing
point of over i6o° (open test) with a volatility of less than oi per
cent, in five hours at lOO", provided they satisfy the electrical require-
ments, are suitable for use in transformers. Rosin oils do not meet
these requirements.
Oils serving as high-tension switch insulators must be free from
moisture and acid, and must above all be practically non-volatile, so as
not to be liable to catch fire from a spark. Cylinder oils are the best
adapted to this purpose.
Transformer oils are tested for electrical insulating properties, not
by determining the ordinary insulation resistance, but by measuring
the E.M.F. requisite to send a spark through a column of oil of
definite length. A spark gap is set up within a cylindrical glass vessel
of about 200 c.c. capacity and 3 cm. diameter containing the oil, and
the E.M.F. is raised until a spark passes. The terminals must be
polished spherical knobs, and their distance apart must be kept fixed.
Bubbles of water or air and floating fibrous matter affect the results
very seriously.
7?:— LIQUID FUEL FOR INTERNAL COMBUSTION ENGINES.
Petroleum distillates of all grades — from the light petrol to heavy
fuel oils— form the principal liquid fuels emplo)'cd in internal com-
bustion engines. In addition, coal-tar oils, lignite-tar oils, and even
crude tar are used to a small extent in the most modern forms of
Diesel engine.
For high speed motors petrol is the usual fuel. With the spray
carburettors now employed heavier grades of petrol are serviceable ;
the average specific gravity is about 072. Many modern carburettors
are capable of giving a good mixture with air with petrol of higher
density, that of sp. gr. 076 being employed for motor-bus vehicles and
others of similar type. The gross calorific value of petrol is about
11,100 calorics per pound ; the net value 10,200 calories.
The specific gravity alone is but a rough guide to the character of
the petrol. A distillation test should be conducted to ascertain the
various fractions over given ranges of temperature. A good petrol of
sp. gr. 071 will }icld nearly 80 per cent, below 120", and 90 per cent,
below 140".
Benzene (90 per cent, benzol) is an efficient substitute for petrol.
In many cases the two liquids are employed, mixed in various pro-
portions. The calorific value of benzol is 9900 calories gross, and 9500
calories net per pound.
HEAVY FUEL OILS 45
In slow speed oil engines ordinary kerosene is employed on a large
scale. Owing to its low vapour tension at ordinary temperatures, the
kerosene has to be vapourised by heat before admixture with air.
The Diesel engine, with the semi-Diesel type which followed the
introduction of the Diesel principle, are not dependent on the formation
of an explosive mixture, but on the steady combustion of a fine oil
spray through a great portion of the working stroke. The introduction
of this type of engine has extended enormously the range of liquid
fuels available for power.
Heavy petroleum oils are employed usually, but the very great
advantage of being able to use coal-tar and lignite-tar oils cannot be
overestimated in countries depending on foreign supplies for all
petroleum products. With the latter oils a small quantity of a
petroleum oil is injected by an independent pump, to serve as the
means of ignition of the coal-tar oil forming the major bulk of the
fuel. Since a fine spray has to be produced, it is essential that the tar
or tar oil shall contain but little free carbon.
(7.— FUEL 'OILS (MASUT, ASTATKI).i
Crude oils, liquid still-residues (Masut), tar residues, cheap lignite tar
oils, etc., are largely used, where economic considerations permit, for
steam-raising purposes under locomotives, marine engines, and other
boilers. The oils must be atomised by some suitable injector, these
being operated either by steam, air under pressure, or by forcing the
heated oil under pressure through special atomisers.
The examination of fuel oils consists essentially in the determination
of the calorific value and the specific gravity. The flashing point is also
invariably determined on account of safety in use. In the British
Mercantile Marine oil is not permitted for fuel purposes unless the
flashing point is above 150'' F.
The calorimetric value is determined in a Berthelot, Krocker, or
Mahler bomb (see Vol. I., Part I., p. 254) ; it can also be calculated from
the elementary composition by means of the following formula given by
Mendelejeff : —
Q = 8iC-f30oH + 26(0-S).
According to the revised Admiralty specification ^ (1912) for oil
fuel the flashing point shall not be lower than 175° F., close test, Abel
or Pensky-Martens. (In the case of oils of exceptionally low viscosity,
such as distillates from shale, the flashing point must not be less than
^ Cf. Zaloziecki and Lidow, Naphtha, 1904, Nos. 21, 22.
^ Cd. 7010, J. Soc. Chetn. Ind., 1913, 32, 859.
46 MINERAL OILS
200' F.) The proportion of sulphur contained in the oil shall not
exceed 300 per cent. The oil fuel supplied shall be as free as possible
from acid, and in any case the quantity of acid must not exceed 005
per cent., calculated as oleic acid when tested by shaking up the oil
with distilled water, and determining by titration with decinormal alkali
the amount of acid extracted by the water, methyl orange being used
as indicator. The quantity of water delivered with the oil shall not
exceed 05 per cent.
The viscosity of the oil supplied shall not exceed 2000 seconds for
an outflow of 50 c.c. at a temperature of 32' F., as determined by
Sir Bovcrton Redwood's standard viscometer (Admiralty type for
testing oil fuel). The oil supplied shall be free from earthy, car-
bonaceous, or fibrous matter, or other impurities which are likely to
choke the burners.
^—DUST-LAYING OILS.
The most suitable dust-laying oils for roads are crude oils, heavy
asphalt oils, oily by-products, tars, liquid asphalt, and emulsions of oils
and water (Westrumite). Raschig has recently proposed a mixture of
tar and clay under the name of "Kiton."
An extensive series of dust-laying oils was investigated by R.
Heise,^ who concluded that the so-called water-soluble oils (see
p. 102), which are diluted with water before use, are not to be recom-
mended. Thin pure mineral oils are considered by him to be the
most efficient
Dust-laying oils used for wooden floors and linoleum should be pure
mineral oils of high specific viscosity, and should give no separation of
sticky substances in the course of a few weeks.
/.—PARAFFIN WAX.
Crude paraffin wax or paraffin scale always contains some of the
high-boiling hydrocarbons from which it has crystallised on cooling.
The "scale" is subsequently refined to form the paraffin wax of
commerce.
Hard paraffin wax for the manufacture of candles should melt at
about 50.° Soft paraffin wax, prepared by cold-pressing comparatively
light oils, melts at about 30", and is used for impregnating textiles, etc.,
and as an addition to hard candle-paraffin.
The examination of hard paraffin wax is described in the section
on " Special Methods employed in the Oil and Fat Industries," this
Vol., p. 179.
' Arbeiten aus d. Kais. GesundkitisamI, 1909, 30, part i.
TAR AND PITCH RESIDUES 47
Paraffin Scale ^ contains various quantities of impurities or "dirt"
(fibres of press-cloths, sand, etc.), water, and hydrocarbons of low
melting point termed " oil," which consists chiefly of" soft paraffin."
Determination of " Dirt." — A weighed quantity of the sample is
melted, allowed to subside, the clear paraffin wax poured off, the
residue mixed with naphtha or petroleum spirit, the whole transferred
to a tared, dry filter paper, washed with the solvent used, dried, and
weighed.
Determination of Water. — The scale is strongly heated in a copper
flask connected with a condenser, and the distillate collected in a
narrow graduated measure in which the volume of water that has
distilled over is read off. A little light oil distils over with the water.
The condenser tube must be washed out with naphtha or petroleum
spirit (previously saturated with water), as a little water usually adheres
to the sides.
Determination of Oil. — A quantity of the scale, freed from water and
dirt by melting and subsidence, is allowed to cool overnight to a
temperature of 15°, the solid residue ground to powder, and a portion
treated in a press provided with a pressure gauge to express the oil.
For this purpose the sample is wrapped in fine linen press-cloth and a
sufficient number of layers of filter paper to absorb all the oil.
These methods for the examination of paraffin scale, which have
been agreed upon by the Scottish Mineral Oil Association, have
been described with full details by J. S. Thomson.^
^.— TAR AND PITCH RESIDUES.
{Petroleum Tar, Asphalt, and Pitch.)
In the distillation of crude oil a variety of dark-coloured residues
are obtained which are used as paving asphalt, lubricants, or as raw
materials for the same, and also for a number of other purposes. The
more fluid of these residues are sometimes sold directly as cylinder oils ;
others, which only just melt on the water-bath, may be worked up by
"cracking," often with a yield of more than 50 per cent, into dark
lubricating oils.
In the examination of these products the testing of their viscosity
affords no useful criteria. Their value depends on their softening- point
and melting point. The melting point is best determined by G.
Kraemer and S. Sarnow's method, which is fully described in the
section on "Coal Tar," Vol. II., Part II., p. 837. The results obtained
^ Cf. Lewkowitsch, Chemical Technology and .Analysis of Oils, Fats, and Waxes, 4th ed.,
1909, vol. iii., p. 211.
^y. Soc. Chem. Ind., 1891, 10, 342.
48
MINERAL OILS
by this method are consistent in themselves, but, of course, differ for a
given substance from the melting point as taken by the capillary tube
method. This is illustrated by the following data : —
Table 13.
Melting point.
Material.
Kraemer and Sarnow's
metlicxi.
Capillary tube
method.
Ceresin ....
Beeswax
Paraffin wax .
Rosin ....
Asphalt (refined) .
Asphalt (brittle) .
Petroleum pitch (Alsatian)
52°
55° -5
46°
67° to 67°-5
51° -5 to 52°
82°
105°
47° to 53°
61°-5 „ 63°-5
45° „ 48°
Indefinite
11
»i
11
For the determination of the specific gravity, if it be desired only to
ascertain whether this is greater or less than i-o, a fairly large quantity
of the sample is melted and a drop or two allowed to fall into a beaker
of water at 15°; air-bubbles, if present, must be removed with a feather.
For accurate determinations a pyknometer is used.
For the estimation of the content of Paraffin Wax the products
must first be refined. This is carried out in the same manner as in
the jexamination of ozokerite (p. 55). The paraffin wax is then
determined by the method described on p. 179.
The recognition of the presence of Fat Pitches, such as are obtained
in the candle, wool-fat, etc. industries, is rendered easy by their contain-
ing, as a rule, besides hydrocarbons, notable proportions of fatty acids
and esters, which are, of course, absent from petroleum. Very hard
fat pitches, however, obtained by pushing the distillation to the utmost
limit, only contain small proportions of fatt)' acids and esters. The acid
value and the saponification value of these compounds are determined
by the methods described in the section on " Oils, Fats, and Waxes,"
this Vol., pp. 122 and 1 14.
The subjoined Table gives an indication of the values obtained with
" Stearine Pitch," and " Petroleum Pitch," respectively : —
Table 14.
Stcarine
pitch.
Petroleum
pitch.
Stearine
pitch.
retroleuni
pitch.
Acids values -
0-2
1-0
2-4
2-9
4-0
01
0-3
0-3
1-2
f
Saponification
values
2-2
2-4
4-3
8-3
1-3
1-8
1-7
2-6
1-1
TAR AND PITCH RESIDUES 49
When soft fatty pitches are destructively distilled considerable
quantities of fatty acids are found in the distillate, especially in the
first runnings. In the case of hard pitches only the first drops that
distil over contain notable amounts of acids ; the yield of acids can,
however, be considerably increased by distilling with the aid of super-
heated steam at 300^ The distillate from lignite pitches, on the
contrary, contains only minute proportions of acids.
The detection of IVood-tar PitcJi is facilitated by the characteristic
smell of creosote, and by its almost complete solubility in absolute
alcohol and in glacial acetic acid, in which petroleum pitch and fat
pitches are, for the most part, insoluble. According to E. Donath and
B. Margosches,^ wood-tar pitch differs from all other pitches by its
sparing solubility in carbon tetrachloride.
Coal-tar Pitch may be detected by the presence of a considerable
amount of free carbon. The best method, however, is to distil the
sample destructively and to estimate the anthracene in the distillate by
Luck's method, as described in the section on "Coal Tar," Vol. II.,
Part II., p. 805.
The detection of Petroleum Pitch in Natural Asphalt is frequently
required. The following method proposed by J. Marcusson and
Eickmann ^ can be employed for this estimation : —
30 g. of the sample are dissolved in 45 c.c. of benzene in a small
flask under a reflux condenser, and the solution poured into 600 c.c. of
petroleum spirit boiling below 80° ; the flask is rinsed out with 50 c.c.
of petroleum spirit. After standing for some time the solution is
sucked off" from the asphaltic precipitate, and the filtrate shaken three
times successively with 45 c.c. of concentrated sulphuric acid in a
separating funnel to remove all asphaltic substances. It is then
further shaken with a N\\ solution of alkali in 50 per cent, aqueous
alcohol and then several times with water, and finally evaporated, dried
for ten minutes at 105°, and weighed.
The following data may furnish some guidance in the interpretation
of the results so obtained : natural asphalt gave 1-4-31 per cent, of oily
matter, yellow-brown to brown in colour, and distinctly liquid at 20° ;
paraffin wax appeared to be absent, since on cooling the alcohol-ether
solution to - 20°, only tarry, transparent substances separated out.
Petroleum pitch, on the other hand, gave 26-58 per cent, of oily
matter of a green to greenish-black colour, which was not liquid at 20°
but pasty (sometimes almost liquid and sometimes very viscous), with
solid particles; the content of paraffin wax amounted to 3-3-i6-6 per
cent.
If the quantity of petroleum pitch present is large, it is recommended
1 Chem. Ind., I904, 27, 220 ; J. Soc. Chem. Ind., 1904, 23, 541.
2 Chem. Zeit., 1908, 32, 965.
50 MINERAL OILS
to distil the pitch destructively, and if small, to distil the oil)' substances
dissolved by petroleum spirit, and to determine the paraffin wax in the
distillate.
The detection of petroleum asphalt in natural asphalt may also be
based on the comparatively high percentage of sulphur usually found
in the latter, which varies from 2-10 per cent.
The above method will be found useful in the examination of
Asphalt Substitutes, consisting of mixtures of powdered limestone and
petroleum pitch. For this purpose it is necessary to first extract the
bitumen, which is effected as follows: —
From 2-5 g. of the finely powdered air-dry material arc boiled in a
conical flask under a reflux condenser with 100-200 c.c. of benzene.
The flask is allowed to stand overnight in a slanting position, and the
main portion of the clean supernatant liquid is poured off into a second
conical flask which is also kept in a slanting position. The solid residue
is shaken up with a fresh quantity of benzene, which is allowed to settle
as before, and decanted, on the same day, into the second flask. This
is allowed to settle overnight, and the clear benzene solution is then
finally run off and distilled. The residue is dried at 105' in a tared
dish, and weighed. A further quantity of bitumen is extracted from
the solid residue by decomposing it with hydrochloric acid and shaking
up with benzene. From the total soluble bitumen thus obtained the
mineral ash, as determined by incineration, is subtracted. The nature
of the soluble bitumen is then examined.
An alternative method for the extraction of the bitumen has been
proposed by A. Prettner.^
Z.- BY-PRODUCTS OF THE PETROLEUM INDUSTRY.
BY-PRODUCTS OF THE REFINING OPERATIONS.
1. Acid Tar. — The acid tar which separates from, the concentrated
sulphuric acid, used in refining, by dilution with water consists chiefly
of resinous substances of unknown composition. It also occludes free
sulphuric acid and sulphonic acids. Their determination, which is,
however, very rarely required, may be carried out by the methods
described under "Turkey Red Oils," in the section on "Special Methods
employed in the Oil and Fat Industries," this Vol., pp. 170 et seq.
2. Pitch. — This is examined for the melting point and ash, as
described in the section on " Coal Tar," Vol. II., Part II., pp. 836 ct scq.
3. Waste Acid. — This consists of the dilute acid separated from the
acid tar, and is valued by the determination of the proportion of actual
acid contained.
' Chem. Zeit., 1909, 33. 917, 926 ; /. Soc. Chem. Ind., 1909, 28, 983.
SHALE AND LIGNITE OILS
51
J/.— PRODUCTS OF THE SHALE AND LIGNITE INDUSTRIES.
By the destructive distillation of shale and of lignite, tars are
obtained which yield crude oils on distillation. These are treated
similarly to crude petroleum, and are worked up into naphtha, burning
oil, gas oil, and paraffin wax. *
EXPERIMENTAL DISTILLATION TEST.
The yield of oil which a bituminous shale or lignite will give
is determined by an experimental distillation test.
Scotch oil-shales show considerable differences in the yield of oil.
The richer shales yield about 30 gallons of oil per ton of shale, and in
some cases as much as 40 gallons, and average about 73 per cent, of
mineral matter; Broxburn shale yields 12 per cent, of crude oil, 8 per
cent, of water, 9 per cent, of coke, 4 per cent, of gas, and 6"] per cent, of
mineral residue. A high-grade lignite yields approximately 10 per
cent, of tar, 52 per cent, of water, 32 per cent, of coke, and 6 per cent, of
gas, including loss. The bituminous shale of Messel (near Darm-
stadt) yields 6-10 per cent, of tar, 40-45 per cent, of water, and 40-50
per cent, of residue.
A laboratory distillation, although of limited value in estimating the
yield obtainable on a large scale, is frequently serviceable. The following
method of carrying out the test is recommended : —
A tared retort of refractory glass, holding 150-200 c.c, is connected
with a water-cooled receiver fitted with
an exit tube, as shown in Fig. 14.
From 20-50 g. of the pounded sample
are heated, at first with a small and
finally with a full flame, as long as any
vapours condense. The gases issuing
from the receiver are tested with a
flame from time to time; if the distilla-
tion is properly conducted (over four to
six hours) they should either not be
inflammable, or only burn weakly and fitfully. The distillate,
consisting of turbid water and tar, is weighed. The tar which has
condensed in the neck of the retort is melted and run down into
the receiver ; the latter is then placed in hot water, and some hot
water poured into it, so that all the tar may collect on the surface.
After cooling, the solidified tar is broken up, after the water has
drained ofl". The lumps are dried preliminarily with rolls of filter-paper,
then air-dried, and weighed. It is safer to extract the tar by means of
benzene, and then to evaporate and weigh the residue. To translate
Fia. 14.
52 MINERAL OILS
laboratory yields into working yields they must be diminished by a
large factor, sa}' by 30-40 per cent., according to the conditions of
manufacture. (Lignite tar as produced in works is less acid and
specifically lighter than the laboratory product.)
As an alternative to this method, a metal retort and a considerably
greater quantity of the sample may be used for the initial distillation.
I. Shale Oil.^
The manufacture of paraffin and paraffin oil by the destructive
distillation of shale was initiated by James Young in 1851. A highly
bituminous mineral known as Boghead coal or Torbanehill mineral was
first used, from which a yield of 120 to 130 gallons of crude oil per ton
was obtained ; the supply of this mineral was, however, exhausted
within a k\v years, and the shales now employed in Scotland, which is
the chief centre of the industry, are those found between the Coal-
measures and the Old Red Sandstone.
This oil-shale, which is dark grey or black in colour and has a
specific gravity of about i-75, is distilled at a comparatively low tempera-
ture. Horizontal retorts were at first employed for the distillation, but
vertical retorts and continuous methods of distillation in presence of
superheated steam have since been introduced by Young, Henderson,
and Beilby, whereby increased efficiency and control of the conditions
of working have been effected.
Crude shale oil has a specific gravity of o-86o-o-900, and solidifies
at the ordinary temperature ; it consists of 70-80 per cent, of paraffins
and olefines, small quantities of benzene hydrocarbons and naphthenes,
a small proportion of phenol and cresols, and a larger proportion of
basic constituents (pyridine, etc.). The refining process comprises
fractional distillation, together with treatment with acid and alkali ;
the solid paraffin is separated from the portion of the oil, the specific
gravity of which is above 0840, by cooling and cr)-stallisation. The
commercial products thus obtained vary with the nature of the mineral
and the process of distillation adopted ; they may be classified under
the following headings : —
Sp. gr.
Gasoline ...... o-6oo to 0-690
Naphtha or shale spirit
Burning or paraffin oil
Medium or light mineral oil
Lubricating oil
0700 „ 0760
0760 „ 0-840
0-840 „ 0-870
0S65 „ 0-910
M.P.
Paraffin wax or " scale " . . . . 43° to 60°
' C/. B. Redwood, Petroleum and its Products, 3rd ed., 1913, vol. ii., pp. 83 etseq.\ I. L
Redwood, Mineral Oils and their By-Producis ; W. Scheithauer, Shale Oils and Tars and their
Products, English translation by C. Salter ; also "The Oil-Shales of the Lothians," Memoirs
of the Geological Survey^ Scotland, 191 2.
LIGNITE TAR 53
Gasoline and naphtha contain from 60-70 per cent, of defines and
other hydrocarbons acted upon by fuming nitric acid, burning oil from
30-80 per cent. ; lubricating oil consists almost entirely of olefines.
B. Redwood^ gives the following examples of the average )'ield of
commercial products obtained at two of the principal Scottish refineries
in 1895 ; the grouping of the fractions is somewhat different in the two
cases : —
I. II.
Gasoline"*
NaphthaJ "
Burning oils
Intermediate and heavy oils
Lubricating oils .
Paraffin scale
Paraffin (refined or semi-refined)
Loss
6-09
3.0
31.84
39-0
23-97
« • •
• • • •
i8-o
13-53
• • •
.
lO-O
24-57
30-0
I GO-GO
lOO-CK
The distillation of the bituminous shales of New Brunswick, Canada,
and of the United States has been investigated by C. Baskerville.-
The Examination of Shale Oil and of Shale Oil Products.
The methods of examination described in connection with petroleum
are applicable to the corresponding products from shale oil. These
comprise the determination of the specific gravity, the solidifying point,
the distillation test, the flashing point, the burning quality, the illumin-
ating value, and the content of " paraffin scale " and paraffin wax.
The Solidifying Point of the crude oil is determined by dipping a
thermometer into the oil, previously heated to 6o°-70°, then withdrawing
it and allowing to cool ; the temperature at which the drop adhering to
the bulb of the thermometer is seen to solidify is taken as the solidify-
ing point. This point is higher the greater the percentage of paraffin
present.
The methods for the determination of Paraffin " Scale " and of
Paraffin Wax are described in the section on " Special Methods
employed in the Oil and Fat Industries," this Vol., p. 179.
II, Lignite or Brown Coal Tar.^
The distillation of brown coal or lignite forms an important industry
in Germany ; it is not carried on in this country, nor in the United
States. The methods of distillation are similar to those employed in
the case of shale, and the resulting tar is fractionated and purified for the
preparation of commercial products on analogous lines.
^ Petroleum and its Products^ vol. ii., p. 124.
2 Eng. and Min.J., 1909, 88, I49, 195, and 501 ; /. Soc. C/ietn. /nd., 1909, 28, 878.
^ Cf. B. Redwood, Petroleum and its Products ^ vol. ii., pp. 124 ei seq.
54 MINERAL OILS
At the ordinary temperature lignite tar is a butter-like mass, yellow
to brown in colour, and having a smell of creosote and often of
sulphuretted hydrogen. The solidifying point ranges from i5'-3o°; it
begins to boil between 80° and loo^and the bulk of the distillate comes
over, as a rule, between 250 and 350'.
The tar consists mainly of saturated and unsaturated hydrocarbons,
of which the former predominate. Owing to the higher proportion of
unsaturated hydrocarbons as compared with shale oil the iodine values
both of the crude oil and of the paraffin wax obtained from lignite are
higher, and amount to 70 and 9 respectively. Other constituents of the
tar which are present only to a small extent are phenol, cresols, benzene
and its homologues, naphthalene (o-i-o-2 per cent.), chrysene (Ci^Hj.,),
and picene (Co.>HjJ ; and in very small quantities, aldehydes, ketones,
pyridine bases, quinoline, carbon bisulphide, thiophene and mercaptans.
The Examination of Lignite Tar is conducted similarly to that
of shale oil, and the products obtained therefrom are tested in an
analogous manner.
For the Distillation Test of the Crude Tar, about 200 g. are distilled
from a retort. The first runnings, up to the point when a drop
crystallises on being cooled with ice, are collected and weighed as light
oil, and the subsequent fraction, until reddish resinous matter begins to
distil, represents crude paraffin wax ; the ensuing picene fraction is
collected separately, the residue of coke in the retort weighed, and
the gaseous products plus loss taken by difference.
Examination of Gas Oil. — This forms an important fraction of lignite
tar. It should be practically free from creosote, which is ascertained by
shaking 100 c.c. of the oil with 100 c.c. of sodium hydroxide solution of
sp. gr. 1-05 for five minutes and measuring the decrease in volume. The
oil should also be free from sulphur. For the Distillation Test fractions
are collected at intervals of 50^ ; the greater the proportion of the
sample that distils below 300" the greater is its value as a gas oil.
in. Montan Wax.
Montan Wax was first prepared by E. von Bogen ^ from the
bitumen extracted from dried Thuringian lignite by means of volatile
solvents or from freshly mined lignite by treatment with superheated
steam. The resulting product is redistilled repeatedly with superheated
steam, and finally distilled in a vacuum. It is used chiefly as a Carnaliba
wax substitute in the manufacture of polishes, and as an insulating
material in place of ceresin.
The wax forms a hard, white mass, which melts above 70°, and
consists of a mixture of fatty acids and a hydrocarbon. The acid
1 Gcr. P.its. ior373 ; 1 16453; Eng. Pat., 5999(1900). /. Soc. Chem. Ind., 1900, 19, 728;
Z. angew. Chem., 1901, 14, llio ; /. Soc. Chem. Ind., 1901, 20, 1221.
OZOKERITE AND CERESIN 55
" Montanic acid" melts at 80°, and has a sp. gr. of 0-915 ; the hydro-
carbon is a saturated compound, melts at 58°-59°, and has a sp. gr. of
0-920. The latter is readily carbonised on heating with concentrated
sulphuric acid, a reaction which differentiates it from paraffin wax.
A sample of Montan wax examined by H. Ryan and T. Dillon,^
which was of a yellowish colour, had a melting point of 76°, an acid
value of 73-3, a saponification value of 73-9, and an iodine value (Hiibl-
Waller) of 16-0. It yielded 47 per cent, of unsaponifiable matter and
53 percent, of crude montanic acid. The latter had an acid value of
138-3 and consisted in the main of an acid, CogH^gOo, with a molecular
weight of 432 and a smaller quantity of an acid of lower molecular
weight. The unsaponifiable matter had an acid value of 31-3 ; from its
elementary composition it did not appear to be a pure hydrocarbon, but
was free from hydroxylic constituents.
Montaniji Wax is a similar product to Montan wax, but differs
greatly in its physical properties.^
iV.— OZOKERITE AND CERESIN.
Ozokerite is a naturally occurring bituminous product which is
found in several localities in the vicinity of petroleum springs. The
best-known product is that from Galicia ; it is also found in Roumania,
Utah, the Argentine, and the Orange River Colony.^
Crude ozokerite varies in colour from yellow to dark brown. The
specific gravity varies from 0-91-0-97; the melting point depends upon
the proportion of liquid hydrocarbons, and it is accordingly difficult to
fix a lower limit, but an upper limit of 100° may be accepted. It is
purified from mineral matter, clay, etc., by a liquating process and by
boiling out with water, and then consists chiefly of h}'drocarbons
together with oxygenated and wax-like substances. Fraudulently
added impurities comprise asphaltum (mineral pitch) and residues
from paraffin-oil distilleries.
In the examination of ozokerite the loss on heating to 150° (which
should not exceed 5 per cent.), the melting and solidifying points, and
the proportion of mineral matter should be determined. For the
estimation of the mineral contents small pieces are cut from the bottom
of the blocks and extracted with petroleum spirit.
A reliable valuation of ozokerite can be effected by closely following
the method of refining as adopted on the large scale.
The following method for the commercial valuation of ozokerite is
recommended by B. Lach:^ — 100 g. of the sample are treated in a
tared porcelain basin with 200 g. of fuming sulphuric acid at a
^ Proc. Roy, Dublin Soc.^ 1909, 12, 202 ; J. Soc. Chem. Ind., I909, 28, 878.
^ C/". J. Berlinerblau, Das Erdwac/is, Ozokerit und Ceresitt, 1 897.
' C/ietn, Zeit., 1885, 9, 905 ; /. Soc, Chem. Ind,, 1885, 4, 488.
56 MINERAL OILS
temperature of 1 70^-1 80°, with constant stirring, until sulphur dioxide
ceases to be evolved, and the basin then allowed to cool, and weighed ;
the loss in weight represents the sum of the water and hydrocarbons.
The residue is then melted and 10 g. of animal charcoal, previously
dried at 140°, stirred in. A tenth part of this mixture is weighed off in
a paper thimble, extracted in a Soxhlet thimble with petroleum spirit
boiling below 80°, and the filter dried at 130'^ and weighed; this gives
the content of ceresin. This result may be checked by evaporating the
petroleum spirit solution and drying the residue at 180''; the melting
point of the residual ceresin is then determined. The proportion of
fuming sulphuric acid used may be varied according as the colour of
the refined product is desired to be yellow or white.
According to E. von Boyer,^ 5 g. of the sample is sufficient for a
technical analysis.
Ozokerite is exclusively worked up to-day for the preparation of
Ceresin. For this purpose it is heated with sulphuric acid, with
constant stirring, decolorised with charcoal, and filtered through a filter-
press. The cakes thus obtained are then treated with volatile solvents
to extract the contained ceresin. The methods of the examination of
ceresin are described in the section on " Special Methods employed in
the Oil and Fat Industries," this Vol., p. 187.
C>.— ICHTHYOL.
By the dry distillation of the bituminous shales containing fossil
fish found at Seefeld in the Tyrol, a crude volatile oil is obtained,
which when treated with an excess of concentrated sulphuric acid and
subsequently neutralised by ammonia yields the product known as
" Ichthyol," the ammonium salt of ichthyol sulphuric acid. It has
been frequently stated to be a definite compound of the composition
C23H3gS30c(NHJo, but it has been definitely proved by F. W. Passmore,^
from its behaviour towards solvents, that this is not the case ; the
sulphur is present both as sulphonate and sulphate, and in addition
a portion is derived from the original oil previous to sulphonation
(" sulphidic " or non-oxidised sulphur).
According to Passmore, ichthyol contains 10-72 per cent, of total
sulphur, of which 594 per cent, (reckoned as ammonium sulphate) is
present as mineral sulphates. From these figures and other data he
calculates the total organic sulphur on the dry organic residue as i8-66
per cent, and that of the "sulphidic" sulphur as 12-51 per cent.
Passmore has also published analyses of a number of preparations
of a similar character to ichthyol which have been introduced for
medicinal purposes under various trade-names, such as, " Ichthynat,"
1 Z. angew. C/iem., 1898, 17, 383 ; /. Soc. Chem. /nd., 1898, 17, 609.
2 Chem, and Drug., 1909, 75, 935.
PEAT TAR 57
'• Ichtosan," " Isurol," etc. ; these contain from i2-go-i6-66 per cent, of
organic sulphur, and from 4-oy-g-ii per cent, of "sulphidic" sulphur,
calculated as above on the dry organic residue.
Ichthyol and the allied preparations are used in medicine chiefly for
the external treatment of skin diseases, such as chronic eczema, and as
internal antiseptics.
Properties of Ichthyol. — Ichthyol in the form of the ammonium
salt is a reddish-brown viscid liquid with a bituminous odour and taste.
It is soluble in water, glycerine, oils, fats, and vaseline. Treated with
potassium hydroxide, ammonia is liberated, and the mixture after
drying and igniting gives off sulphuretted hydrogen when treated with
hydrochloric acid. When dried on a water-bath it loses about 45 per
cent, of its weight.
P. -PEAT TAR.
In the peat-distilling industry, peat is either distilled right down to
coke, which is used in metallurgical operations, or it is only partially
carbonised so that the residue may be employed as a household or
industrial fuel. The distillates obtained contain respectively 4 or 2 per
cent, of tar; 40 or 36 per cent, of products soluble in water, consisting of
ammonia, methyl alcohol, and acetic acid; and 21 or 12 per cent, of
gaseous products.
To carry out an experimental distillation on the laboratory scale,
about 500 g. of the sample are distilled from an iron retort ; the works
yield of tar may be taken as 70 per cent, of that obtained in the
laboratory test. A good peat should not contain more than 6-8 per
cent, of ash. The tar contains a considerable proportion (30-40 per
cent.) of creosote.
Literature.
AlsiNMAN, S. — Taschenbuch fiir die Mineralol-Industrie, 1896.
Benedikt, R., and Ulzer, F. — Analyse der Fette und IVachsar/en, 1903.
Berlinerblau, J. — Erdwachs, Ozokerit und Ceresin, iSgy.
Engler, C, and HoFER, H. — Das Erd'dl, 191 1.
Graefe, E. — LaboratoHumsbuch fiir die Braunkohlenteerindustrie, 1908.
HOLDE, D. — Untersuchung der Miner aid I e und Fette, 3rd edition, 1909.
Kohler, H. — Chemie und Technologie der Natiirlichen und Kilnstlichen Asphalte,
1904.
Lewkowitsch, J. — Chemical Technology and Analysis of Oils, Fats, and Waxes,
4th edition, 1909.
RakusiNj M. A. — Die Untersuchung des Erdols und seine Prodiicte, 1906.
Redwood, Boverton — Petroleutn and its Products, 3rd edition, 1913.
Redwood, I. I. — Mineral Oils and their By-products, 1897.
SCHEITHAUER, W. — Fabrikation der Mineralole und dcs Paraffins aus Schwelkohle,
1895.
SCHEITHAUER, \N ,— Shale Oils and Tars and their Products, English translation
by C. Salter, 19 13.
Veith, a. — Industrie der Mineralole, 1902.
WiSCHiN, R. A. — Die Naphthene, 1901.
LUBRICANTS
By Prof. D. HOLDE, Ph.D., Divisional Director of the Royal Testing Laboratory,
Gross-Lichterfelde, Berlin, in collaboration with G. Meverheim, Ph.D.
English translation revised by the late J. Lewkowitsch, M.A., Ph.D.i
The substances used as lubricants may be classified as follows: —
(a) Mineral Lubricants. — Owing to their cheapness and to certain
technical advantages possessed by them, mineral oils enjoy at present
by far the widest application. In Western Europe they are imported
mainly from America and Russia, to a smaller extent from Galicia and
Austria-Hungary ; lubricants are also obtained as one of the products
of the Scotch shale-oil industry. Germany produces about one-fifth of
its consumption from native material, chiefly from Wietze petroleum.
All mineral lubricants of whatever grade are more or less alike
chemically, in that they are composed of petroleum hydrocarbons.
There are two chief requirements to which they all must conform.
They must not be appreciably volatile, so that loss of volume and risk
by fire may be reduced to a minimum, and they must possess a certain
viscosity so that they can adhere to the metal surfaces which they are
to lubricate, and maintain a film of sufficient thickness between them.
The nature and quality of mineral lubricants vary with the purpose
to which they are applied. The principal grades in common use are
the following ; the flashing points given are all by the closed test : —
1. Spindle Oils, especially adapted to spinning machinery, pale
mobile oils of flashing point i6o°-200°.
2. Compressor Oils {^Freezing Machinery Oils). — Thin oils of solidify-
ing point below —20°; flashing point 140°- 180".
3. Lubricating Oils for Light Machinery. — (Oil for shafting, light
motors, turbines, and dynamos.) Moderately thick oils of flashing
point i7o''-220^ Gas-engine oils should flash at i95°-220°.
4. Lubricating Oils for Lleavy Work. — Thick oils of flashing point
1 90° -2 20".
The above-mentioned varieties are generally refined oils ; they arc
of a clear yellowish- or reddish-brown colour; certain high-class oils of
groups I, 2, and 3 are nearly colourless ; compressor oils are sometimes
^ The Editor is indebted to Mr J. S. S. Brame, Lecturer on "Fuel," The Sir John Cass
Technical Institute, for very kindly reading the proofs of this section, the manuscript of which
had been revised by the late Dr. Lewkowitch, C.A.K.
58
CLASSIFICATION OF LUBRICANTS 59
artificially coloured to a violet tint. The cheaper kinds of heavy
machinery oil are opaque.
5. Heavy Railway Waggon and Engine Oils. — " Summer oil," flash-
ing point above 140°, solidifying point below —5°. "Winter Oil,"
solidifying point below —20°.
6. Cylinder Oils represent the highest boiling fractions of petroleum.
They are mainly the still residues of the lubricating oil fractions of
heavy consistency; they congeal to vaseline-like masses at ordinary
temperatures or a few degrees above 0°. Those oils, which have
been filtered over fuller's earth, are brownish-red and translucent ;
undistilled and unfiltered oils are greenish-black and opaque. In
reflected light the paler American oils show a greenish-grey, the
Russian oils a bluish fluorescence. The flashing points range from
22o°-3i5°, the better qualities flashing not below 260°. Superheated
oils flash at from 28o''-300°, or even higher.
{b) Fatty Oils and Liquid Waxes. — The chief kinds employed
as lubricants are crude and refined rape (colza), olive, castor, animal
oils (lard, tallow, neat's foot, bone, etc.), sperm and arctic sperm oils,
and palm oil. Even blubber oils and also wool-grease are occasionally
used as lubricants.
(c) Mixtures of Fatty and Mineral Oils are used frequently. For
marine engines a mixture of blown rape oil and a mineral oil sold as
" marine oil " is largely employed. Mineral cylinder oils often receive
an admixture (2-12 per cent.) of bone fat.
(cf) Lubricating Greases are employed to some extent on account
of their easy and, in certain cases, economical application. They
consist of solutions of lime-soaps or lime-alkali-soaps in mineral oils,
and contain, as a rule, from 2-6 per cent, of water ; they usually liquefy
at 70° or 80°. Other lubricating greases are mixtures of wool-grease,
tallow, alkali-soaps, etc., with mineral oil. Lubricants containing
graphite are employed as lubricants for cog-wheels, bicycle chains, and
the like. This class of lubricants is likely to be replaced in the near
future by the Acheson Graphite Company's compounds ("Oildag,"
" Aquadag ").^ The lowest class of lubricating greases is represented
by the axle and waggon greases ; these contain lime-soaps, rosin oil,
lignite-tar or coal-tar oils, also magnesium silicates such as talcum.
The cheapest products are adulterated with barytes, plaster of Paris, etc.
(e) Water-Soluble Oils have the property of yielding homogeneous
emulsions with water, and are prepared by dissolving ammonia- or
alkali-soaps in pale mineral oils (sometimes with the addition of
petroleum naphtha). They are chiefly used for lubricating tool-
machines, for charging hydraulic presses and conduits, for oiling yarn
in the textile industries, and as dust-laying oils.
^ Cf. Archbutt and Deeley, Lubrication and Lubricants^ 3rd ed., 1912, pp. 150 et seq.
60 LUBRICANTS
(/) Thickened Oils. — For some purposes mineral oils are thickened
by dissolving in them small amounts of unvulcanised rubber or of
aluminium sulphate.
{g) Non-Oleaginous Lubricants. — There are a few exceptional
cases in which oily lubricants would be dissolved or chemically attacked,
and are therefore inapplicable. In chlorine and oxygen compression
plants, for example, strong sulphuric acid and dilute glycerine respec-
tively are the lubricants used. In the sulphur dioxide industry the
liquid sulphurous acid itself acts as a lubricant for the pistons and
c)-linders.
^.—MINERAL OILS.
Physical Tests.
I. APPEARANCE.
A practised observer can derive valuable information from the
colour, transparency, smell, and consistency of a lubricating oil. The
odour of an oil is best observed by rubbing a drop or two in the palm
of the hand.
(a) Colour. — The colour of an oil is conveniently noted in a thickness
of lo cm. In special cases the examination may be carried out either
with Lovibond's tintometer,^ or with Stammer's colorimeter (see the
section on " Mineral Oils," p. 23).
Colour varies, according to the degree of purification, from water-
white to dark red by transmitted light. Pale oils (not treated with
nitronaphthalene or aniline dyes to render them non-fluorescent)
invariably show a fluorescence, which is green in the case of American
oils and bluish in the case of Russian oils.
Fluorescence is best ascertained by observing a drop of oil upon
glazed black paper; fluorescent oils appear blue, whilst treated oils
appear simply black. For the detection of deblooming substances
such as nitronaphthalene, etc., see p. 94.
Oils containing still residues in notable quantity and not filtered
over fuller's earth are opaque and very dark. Machinery oils are
almost without exception transparent.
Unfiltered cylinder oils have an opaque greenish- or brownish-black
appearance. If filtered or mixed with filtered residues they are dark
red and translucent. Solid, readily melting particles separating in thin
layers from the oil are, as a rule, paraffin wax, pitch, or ozokerite ;
the latter material is added as a thickening agent to certain Russian
cylinder oils.
A slight turbidity in pale oils is frequently due to suspended water.
' Cf./. Soc. Chem. hid., 1888, 7, 424 ; 1890, 9, 10 ; 1894, 13, 308.
MINERAL OILS. SPECIFIC GRAVITY 61
(b) Consistency. — Cylinder oils are liable, owing to changes of
temperature and agitation immediately before examination, to present
very puzzling indications. It is best to pour such oils into a test
tube 15 mm. in diameter and 3 cm. high, warm for ten minutes in the
water-bath, and allow to cool for one hour in water at 20°. The con-
sistency is then observed on inclining the test tube.
(c) Mechanical Impurities are easily recognised in pale oils. Dark
oils must be passed through a sieve of ^ mm. mesh ; not less than
250 c.c. should be poured through the sieve.
II. SPECIFIC GRAVITY.
The specific gravity of mineral lubricating oils is of importance
only when oils of known definite origin are to be compared, or as
a means of identification, although it is usual in commerce to sell the
oil with a statement as to the specific gravity.
Determination of the Specific Gravity by Means of the
Hydrometer.
(a) Standard Hydrometer — The specific gravity of mineral
oils (and liquid fats or waxes) may, if sufficient material is available, be
determined by means of a reliable hydrometer.
In Germany officially calibrated hydrometers, standardised for
+ 15° C, water at +48° being the basis, are obtainable ; Tables specially
adapted to American petroleum and its products have been prepared by
the Normal-Eichungs-Kommission of Germany.^ The temperature of
the experiment is determined by a thermometer attached to the
hydrometer spindle.
Hydrometer readings are, whenever possible, taken at the flat level
of the liquid, viewed from below ; but when the oil is too dark, it
is necessary to read at the upper edge of the meniscus and to add
0001 5 or o-ooio, according to the dimensions of the scale, to the specific
gravity found. Care must be taken that the hydrometer floats freely in
the liquid ; the reading should not be taken before fifteen minutes
have elapsed after the immersion of the hydrometer.
The specific gravity is corrected to the standard temperature of 15°,
For each degree difference between the observed and standard tempera-
ture a correction of ± -00068 is made.
Exainple.
Hydrometer reading at i7°-5 .
0-9010
Meniscus correction .
4-0-OOIO
Temperature correction, 2-5 x -00068 .
+0-0017
Specific gravity at 15
0-9037
^ Published by J. Springer, Berlin.
62
LUBRICANTS
The following Table, worked out by Mendelejefir, gives the tempera-
ture corrections for high-boiling Russian petroleum oils: —
Table 15.
Sp. gr. of fraction.
Correction per 1°.
0-860 to 0-865
0-000700
0-865 „ 0-870
0-000692
0-870 „ 0-875
0-000685
0-875 „ 0-880
0-000677
0-880 „ 0-885
0-000670
0-885 „ 0-890
0-000660
0-890 „ 0-895
0-000650
0-895 „ 0-900
0-000640
0-900 „ 0-905
0-000630
0-905 „ 0-910
0-000620
0-910 „ 0-920
0-000600
(6) Determination of the Specific Gravity by Pyknometers. —
ii great accuracy is required, or if
there is not enough oil available to
use a hydrometer, a pyknometer, such
as the ordinary Sprengel tube or a
Mohr's balance, is employed for the
determination of the specific gravity.
A serviceable form of pyknometer
devised by Gockel for highly viscous
oils is shown in Fig. 15; it has a
capacity of 10 c.c. at 15° and is fitted
with a ground-in thermometer. If
the calibration is correct, the absolute
weight of the sample divided by 10
gives the specific gravity at 15° with-
out further calculation. Correction to
standard temperature and water at
4° is made by the aid of the data
given above.
If only a few cubic centimetres of the sample are available, a small
pyknometer is used.
In order to determine the specific gravity of pitch-like lubricants
heavier than water, the pyknometer is employed as follows. A
small quantity of the substance, melted if necessary, is poured on the
bottom of the vessel and allowed to cool ; the pyknometer is then
weighed, filled up with water, and again weighed.
(c) Determination of the Specific Gravity by the Flotation
Method. — The specific gravity of very small quantities of a lubricant
Fig. 15.
MINERAL OILS. EXPANSIBILITY
63
may be determined, provided the substance is insoluble in dilute alcohol,
by floating it in dilute alcohol of identical density.
Table i6.
Specific Gravity of various Oils at 15°.
American.
Russian.
Lamp oil .
Spindle oil . . .
Machinery oil .
Cylinder oil .
0-780 to 0-800
0-840 „ 0-907
0-875 „ 0-914
0-883 ,, 0-895
0-800 to 0-830
0-850 „ 0-900
0-900 „ 0-915
0-909 „ 0-932
(exceptionally up to 0-950)
Heavy rosin oil .
Coal-tar oil ....
Lignite-tar oil ....
0-973 to 0-982
(exceptionally up to 1-000)
1-090 to 1-100
0-893 „ 0-974
Preliminary trials are made by dropping a little of the oil or melted
fat into a series of mixtures of alcohol and water of progressive densities,
in order to ascertain approximately the upper and lower limits. The
liquid nearest to the substance in specific gravity is then adjusted, by
adding very dilute, or as the case may be, absolute alcohol, a thermometer
being used as a stirring-rod, until the substance just floats in the liquid
without either rising or sinking. The specific gravity of the liquid is
then determined accurately ; it equals the specific gravity of the sample
at the temperature of experiment. It is essential that no air-bubbles
adhere to the floating globules of oil.
in. EXPANSIBILITY.
Although coefficients of expansion do not find a place among the
commonly accepted characteristic constants of oils, they are required for
calculating specific gravities to different temperatures, and especially for
calculating the expansion-space to be allowed for transport, and in
storage vessels.
The expansibility is determined either by taking the specific
gravity at successive temperatures (for corrections for temperature, see
p. 65) or by a dilatometric method. For the latter purpose an apparatus
which allows of the simultaneous examination of eight samples has
been devised by Holde (Figs. 16-18). The dilatometers (Fig. 16) have
the shape of bulbs of about 30 c.c. capacity, with graduated stems
07 mm. in bore, holding about 850 cb.mm. The initial volume of
oil at ordinary temperatures is adjusted in a large water-bath arranged
like a calorimeter as shown. For higher temperatures the water-bath
B is placed in a vapour-bath A (Fig. 17) heated by a Bunsen burner.
64
LUBRICANTS
The vapourising liquid, which is chosen according to the temperature
required, may be ethyl ether (boiling point 35''), ethyl bromide (boiling
point 38'), chloroform (boiling point 61''), carbon bisulphide, alcohol,
or any other suitable liquid. Reflux condensation is provided for at e.
A number of dilatometers, together with a thermometer graduated to
tenths of a degree, are suspended by means of rubber rings in the
water-bath. Fig. 18 illustrates the method of charging the dilato-
meters with oil by suction with a copper or brass capillary tube ;
discharging is performed similarly by blowing in air. Air-bubbles
remaining at the junction of the bulb and stem can usually be
removed by judicious use of the suction-capillary. Any oil adhering
-^#=2
Fig. 16.
Fig. 17.
Fio. 18.
to the upper part of the stem is wiped away by means of a spiral wire
wound with cotton wool.
The stems of the dilatometers are carefully calibrated, once for all,
with the aid of mercury. To empty the mercury for the purpose of
weighing, a thread of glass, which is weighed with the receiving beaker,
is pushed up the stem. The volume of the dilatometer up to the zero
mark is determined by weighing it filled with water ; in this case the
weighings must be reduced to vacuum, which is unnecessary in the case
of the mercury thread calibration.
The coefficient of expansion a is calculated by the following
formula : —
V,-V
a
(^-/)V
+<?
MINERAL OILS. VISCOSITY 65
where V is the initial volume at temperature /, V^, the greater volume
at the higher temperature t^, and c the cubic expansibility of glass, which
may be taken as 0-000025, or may be ascertained by determining the
apparent expansion of the mercury before the experiment.
For heavy viscous machinery and axle oils of sp. gr. not less than
0-908, the value of a between 20^ and 78° is o- 00070-0- 0007 2. Oils of
this class from which particles of wax or pitch separate out at and below
+ 20° show a higher value between 12° and 20"^, namely, 0-00075-0-00081.
For light spindle and dynamo oils, of sp. gr. less than 0-905 at 15",
the value of a is 0-0072-0-00076 between 20° and 78°.
In the case of oils which are homogeneous liquids, the value of a
increases slowly with the rise of temperature.
When an oil contains fusible matter in suspension, a decreases with
rising temperature up to the point when all the suspended particles are
liquefied, and then increases as in the case of a homogeneous liquid.
In the case of oils of different origin but of equal viscosity, a
difference in expansibility corresponds to a difference in chemical
composition.
According to Singer,! Roumanian petroleum residues have an
expansibility of 0-00073-0-00079.
Specific Gravity Correction. — In recalculating the specific gravity
from a higher to a lower temperature, or vice versa, the allowance per
1° for liquid mineral lubricants is 0-00063-00072, or 0-00065 as a mean
value.
When specific gravities are determined by the pyknometer at
temperatures above 30°, allowance must, in addition, be made for the
expansion of the pyknometer itself.
In the case of vaseline-like lubricants or of very viscous cylinder oils,
for which a ranges from 0-000777-0-000876,^ a mean correction of 0-00075
per i'' may be taken.
IV. VISCOSITY.
The accurate determination of the internal friction of liquids
requires the use of apparatus which is unsuited for technical work.
For practical purposes more simple apparatus is employed, by means of
which a relative determination of viscosity is effected. The determina-
tion is usually made by ascertaining the times occupied by two equal
volumes of the liquids under comparison to flow through a narrow
aperture under exactly the same conditions. The numbers thus
obtained are entirely arbitrary, and are different with the various forms
of apparatus, viscometers, employed for the purpo.se.
The viscosity of oils is, in practice, generally compared with that of
^ C/iem. Rev.^ 1896, 13, 298. ^ Miiteilungen, 1895, Ergiinzungsheft, v., p. 23.
Ill E
66 LUBRICANTS
rape oil. Boverton Redwood^ found from a number of tests carried out
with refined rape oil in his viscometer that the average time occupied
by the outflow of 50 c.c. at 60^ F. (i5'-5 C.) is 535 seconds. Taking this
as a standard and its viscosity as = lOO, the viscosity of any other
oil is found by multiplying the number of seconds occupied by the out-
flow of 50 c.c. by 100 and dividing by 535. If the specific gravity of the
oil differs from that of rape oil, which is 0-915 at 60' F., Redwood
introduces a correction by multiplying the above result by the specific
gravity of the sample and dividing by 915.
The viscosity of an oil, V, is therefore obtained from the equation : —
■y _ nx 100 X J-
535x915
where n is the time of outflow and s the specific gravity of the oil under
examination.
As there is no correlation between the specific gravity and viscosity
of an oil, it is more useful to record the numbers as obtained by the
direct determination of the viscosity, and to omit the specific gravity
correction (Lewkowitsch).
Of the many forms of viscometer that have been designed, those of
Redwood, of Saybolt, and of Engler are the most important. Redwood's
apparatus is the recognised standard instrument in this country, and
has been adopted by the Government, by the principal Railway
Companies, and by the Scottish Mineral Oil Association. Saybolt's
viscometer is used in the United States, and that of Engler in Germany,
and generally on the Continent. In France an instrument known as an
" Ixometre," designed by Barbeys, is employed.
Boverton Redwood's Viscometer.- — This instrument, which is
shown in Fig. 19 and in section in Fig. 20, consists of a silvered copper
oil-cylinder C, about i| in. diameter and 3^ in, deep. The bottom of
the cylinder is provided with an agate jet D, the cavity of which can be
closed by means of the plug E formed of a small silvered brass sphere
attached to a wire. A small bracket F terminating in a point is fixed
at a short distance from the top of the inside of the oil cup, and serves
as a gauge of the height to which the oil must be filled. The ther-
mometer T is immersed in the oil. The oil-cylinder is surrounded by
a copper jacket J, provided with a closed side-tube K, which serves for
heating the contained liquid to the desired temperature ; a revolving
agitator L, worked by the handle II, is provided together with a ther-
mometer T^ for recording the temperature of the liquid in the jacket.
The whole instrument is supported on a tripod stand furnished with
levelling screws.
' /. Soc. CItem. Ind., 1886, 5, 126. » /^/^^
THE REDWOOD VISCOMETER
67
To carry out a determination, the copper jacket is filled with water
for temperatures up to 95°, and for higher temperatures with a suitable
mineral oil, up to a height corresponding roughly with the pointer F in
the cylinder C. After the liquid in the jacket has become heated to
the required temperature, the oil to be tested, previously purified and
dried and heated to the same temperature, is poured into C until its
level just coincides with the point of the gauge ; great care must be
e %^
Fig. 19.
Fig. 20.
taken that this level is reached exactly, and that the temperature remains
constant during the observation. A narrow-necked flask holding 50 c.c.
to a point marked on the neck is then placed below the jet D in a
vessel containing a liquid of the same temperature as the oil. The plug
E is then raised, and the number of seconds required for 50 c.c. of the
oil to flow out is carefully observed by means of a chronometer.
At least two tests should be made at the same temperature ; if due
care has been taken the two observations should be closely concordant.
The viscosity value is then calculated to the standard of rape oil as
described above.
68
LUBRICANTS
Saybolt's Viscometer. — The jet of this viscometer is made of metal,
and is eiiclused in a tube which extends below the orifice. The oil-
vessel is contracted above the jet, and is cut away longitudinally on each
side to expose a glass tube with which it is lined, and which can be seen
by means of glass windows provided in the water-bath in which the oil-
vessel is placed. The upper level of the oil is regulated by means of an
overflow gallery, the position of which determines the length of the oil
column, and the outflow, which is observed through the windows of the
bath, is stopped w^hen the oil reaches a certain point in the inner glass
tube of the oil vessel.^
C. Engler's Viscometer. — The vessel A (Fig. 21), which serves for
the reception of the oil to be tested, is filled with oil up to the tip of
Fio. 21.
a small pointer fixed to the side of the vessel, whilst the efflux tube,
which is either made of or lined with platinum, is closed by a wooden
rod b which passes through the cover c. The oil (or water) is caught
as it flows out in the measuring flask which is graduated at 200
and 240 c.c. When the measuring vessel has three bulbs as in
Fig. 21, and has a graduation mark at 100 as well as at 200, each
experiment can be controlled in itself by reading the time of outflow
from 100-200 c.c.
In order to heat the oil to the required temperature for the test, the
inner vessel is surrounded by a heating jacket B, which is filled either
' For further details see Redwood, Petroleum and its Products, 3rd ed., 191 3, vol.
ii., p. 279.
VISCOSITY OF MIXTURES 69
with water or with a high-boiling mineral oil ; the heating is effected
by a movable ring-burner at least lo cm. in diameter, and the bath
stirred by the stirrer DE, thus avoiding any superheating of- the outlet
hole ; F is a small catch which supports the plunger and prevents it
from slipping into the orifice during the experiment.
The expression for the viscosity, generally called " Engler degrees,"
is the quotient obtained by dividing the time of flow for 200 c.c. of
the oil at any specified temperature, by the time of flow of 200 c.c. of
distilled water at 20°.
The relative value of viscosity determinations by Redwood's and
by Engler's apparatus has been investigated by W. F. Higgins.^
Calculated from theoretical considerations, the ratio of the readings
is approximately constant for times of flow on the Redwood viscometer
greater than 100 seconds and is = i-8i (Engler : Redwood) ; below
this the ratio increases with decrease in the time of flow from 1-82- 1-83.
Experimental results on three different oils and at temperatures vary-
ing between 10° and 45° gave ratios between 1-74 and 1-84.
Viscosity of Mixtures of Oils.
As the viscosity is not an additive property, the viscosity of
mixtures cannot be calculated directly from the proportions of the
components, but is always lower than the calculated value. According
to experiments by H. Sherman, T. Gray, and H. Hammerschlag,^ if the
viscosities are plotted as ordinates and the percentages of ■ the
components as abscissae on squared paper, the relationship between
the two is expressed by hyperbolic curves which deviate more strongly
from the straight lines joining the extreme points, the more the
viscosities differ from one another. Mixtures of different mineral oils
give greater deviations from the straight lines than mixtures of mineral
with fatty oils.
For the determination of the viscosity of the unsaponifiable portion
of a blended oil, the viscometers described above will, as a rule, be found
to be too large. In such cases Kiinkler's viscometer, which requires
only 30 c.c. of the sample, will be found useful.''
Absolute Viscosity.
The desirability of expressing viscosities in absolute measure,
instead of by the arbitrary values at present adopted, has recently
received consideration. The absolute viscosities of water and of
1 J. Soc. Chem. Itid., 1 91 3, 32, 568.
2 J. Ind. Eng. Chem., 1909, 1, \2 \ J. Soc. Chem. Ind., 1909, 28, 17.
^ Dingl. Polyl. /., 1893, 290, 2S1. Cf. also Lewkowitsch, Chemical Technology and Analysis of
Oils^ Fats, and Waxes, vol. iii. , p. 52.
70
LUBRICANTS
glycerol have been determined by L. Archbutt and R. Deeley,^ and
a series of determinations of the absolute viscosities of a number of
mineral oils in C.G.S. units has been carried out by W. F. Higgins-
at the National Physical Laboratory in connection with his work
for the International Commission for the unification of tests on
petroleum products.
n^
V. BEHAVIOUR OF OILS AT LOW TEMPERATURES.
In order to judge accurately of the consi.stency of oils when exposed
to cold, the following points must be taken into account.
When mineral oils, in passing from the fluid to the semi-solid
condition, are disturbed, the network of separated solid matter is
ruptured, and the "crystallising" process is greatly affected. In ex-
amining oils at low temperatures, therefore, cooling must take place
without agitation.
Oils must be cooled during at least one hour to the desired
temperature, since the solid particles separate with great reluctance,
_ and temperature equilibrium is attained very slowly. If an
oil has been heated before being cooled down, its physical
condition is altered to such an extent as to modify the
freezing point considerably. In the same way, the effect
of alternate cooling and warming to room-temperature is to
render the freezing point hopelessly variable. Oils may be
exposed to fluctuations of temperature during transportation
or storage, and this possibility must be taken into account
when they are tested.
Pale heavy mineral oils are sometimes known to set to a
jelly whilst remaining perfectly transparent.
The question to be decided is whether, and to what
extent, an oil is fluid at a certain temperature, say — s"
or —15"; or, alternative!)-, at what temperature solids
separate out and the oil becomes semi-solid. Much time
is saved by making a preliminary test with the apparatus
shown in Fig. 22 : the oil is cooled down in a test tube
by means of a mixture of ice and salt, and its behaviour on tilting
the test tube is observed from time to time. The approximate solidi-
fying point being now known, a series of refrigerating solutions which
can be kept at a constant freezing point for an hour or more is pre-
pared, according to the subjoined data. These solutions are partially
frozen by means of a mixture of one part of salt and two parts of
pounded ice or snow.
' Lubrication and Lubricants, pp. 153 ^/ seq.
2/. Soc. Client. Ind., 1913, 32, 568.
I
FlO. 22.
BEHAVIOUR AT LOW TEMPERATURES
71
Temperature.
o
o
- 4° .
- 5° .
- 8°7.
-io° .
-14° •
- 15° to
15-4
Solute.
Parts to 100 of water
Ice
• • •
KNO3
13
fKNOa
iNaCl
1'^
I 2
/KNO3
iNaCl
\ 3-3
BaCl.,
35-8
KCl
22-5
NH^Cl
20
NH4CI
25
For most practical purposes it is sufficient to ascertain whether an
oil flows or does not flow at the temperature of experiment. The
apparatus shown in Fig. 23 may be used with advantage for this
Fio. 23.
purpose.^ A vessel of enamelled iron a, about 12 cm. wide, holds the
standard solution, and is surrounded with a freezing mixture d con-
tained in the earthenware pan c, which is lagged with felt. Test tubes
filled up to a mark (3 cm. high) with oil are placed in the holder
attached to a. After the samples have been cooled for one hour they
are examined as in the preliminary test. A further differentiation as
to consistence may be made by placing glass rods in the test tubes
for a quarter of an hour, and noting whether the tubes are moved up
bodily when the rods are lifted. If the standard refrigerating solution
shows any tendency to fall below the proper temperature, the ice which
has deposited round the inner sides of the vessel is knocked away
and the outer freezing mixture is removed. Temperatures are read
by means of a thermometer graduated to tenths of a degree. The
freezing mixture may have to be renewed from time to time, but as a
rule this is not required, except at the lowest working temperatures.
^ C/. Hofmeister, Mitteilmjgen^ 1889, p. 24.
72
LUBRICANTS
Constant temperatures of —20" to —21° may be maintained by
filling both the inner and outer vessels with the freezing mixture of
ice and salt. To obtain still lower temperatures a thin metal inner
vessel (not enamelled) is used, and both this and the outer vessel are
charged with alcohol into which solid carbon dioxide is thrown as
required.
Quantitative Comparison of Fluidities. The Freezing
Point or Cold Test.
A quantitative statement as to the behaviour at low temperatures is
sometimes required for the valuation of dark railway oils, and ma)- be
obtained by the aid of the apparatus shown in Figs. 24, 25, and 26.
Fio. 24.
Fio. 25
20
10
0
S
This determination is not so important in this country as in the United
States and on the Continent, where the danger exists of machinery
being damaged by the oil becoming solid in the lubricators. Fig. 24
is a diagrammatic representation of the apparatus prescribed for the
testing of oils by the Prussian State Railways ; Fig. 26 shows the
actual form of the apparatus. To carry out the test the oil is thoroughly
shaken in the sample bottle, and freed from mechanical impurities by
filtration through a sieve of ^ mm. mesh. In order to take the effect of
previous heating into account, four tests are made, two with untreated
oil, and two with oil which has been heated on the water-bath to 50" for
ten minutes. In all cases, as also when the simple test described in the
preceding paragraph is carried out, it is well to conduct the preliminary
heating and cooling in the actual testing vessel, be it a test tube or a
U-tube.
FLUIDITY TEST
73
The oil is charged by means of small pipettes fitted with a rubber
ball into the longer limb of the testing vessel. This latter consists of
a U-tube (Fig. 25) of 6 mm. bore, having a millimetre graduation as
illustrated. It is important that these tubes should have no constric-
tion at the bend ; at no point should the bore exceed or fall short of
6 mm. by more than 0-3 mm. The level of the oil is adjusted to stand
at the zero mark, which is 3 cm. above the bottom of the U-tube. The
tube is immersed in a vessel h (Fig. 24 in which two tubes are shown)
filled with the freezing mixture of the specified temperature, and
Flo. 26.
surrounded by the vessel /, which is also filled with the freezing
mixture ; the temperature is controlled by the thermometer /. The
U-tube should stand for at least one hour in the freezing mixture without
being disturbed, the level of the oil being about 10 mm. below that of
the freezing mixture. The tube is then carefully drawn out so far that
the level can be observed, when the rubber tube d is slipped over its
end whilst the pinch-cock e is open. This pinch-cock is then closed and
the pinch-cock f opened, whereby a pressure of 50 mm. is allowed to
act on the oil ; this pressure is generated by pouring water into the
vessel a, in which a weighted funnel b is placed, and controlled exactly
by the manometer c. The height to which the sample of oil has risen
when compressed is read off on the shorter limb of the U-tube, the oil
74 LUBRICANTS
adhering to the sides showing the required level even though the body
of oil may have sunk a little ; this height expresses quantitatively the
fluidity of the sample under compression.
The Scottish Mineral Oil Association directs that the setting point
of mineral oils be determined in the following manner:^ — Place the
sample in a test tube, having a diameter of ij in., to the depth of
about 2 inches. Immerse the test tube in a freezing mixture and
stir the oil slowly with a thermometer until it has cooled down con-
siderably below the temperature at which solid paraffin wax first
appears. Then remove the test tube from the freezing mixture, stir
constantly with the thermometer, and observe the temperature at which
the last trace of solid paraffin wax disappears. The temperature thus
found is the setting point.
VI. VOLATILITY AND INFLAMMABILITY,
Within certain limits, volatility runs parallel with the flashing point,
which latter is readily determined either by the "open" or "closed"
test. Thus the quality of machinery and cj-linder oils may, so far as
volatility is concerned, be judged by their flashing points.
Flashing points, however, are not reliable criteria of volatility unless
they lie above the minimum admissible limit, i.e., unless lower petroleum
fractions are absent. To decide this point it may be necessary to
undertake a fractionation of the oil, or to determine the loss in weight
on heating in an open vessel. The fixing of minimum flashing points
for the various sorts of lubricating oils is a great desideratum. When
lower fractions are absent, the distillation test is useless and even mis-
leading. In practice almost the only lubricants which are tested for
volatility are cylinder, superheated, and turbine oils, also transformer
oils (see preceding Section, p. 43).
Volatility may be judged not only by the flashing point of an oil
but also by its ignition point, i.e., the temperature at which the oil takes
fire and burns steadily. Some authorities hold that this is an even
better criterion of volatility than the flashing point.
(a) Evaporation or Volatility Test.
The volatility of a mineral lubricating oil is ascertained by determin-
ing the loss in weight it undergoes at a given temperature. Several
special forms of apparatus have been constructed for this purpose.
I. L. Archbutt's Vaporimeter.- — This consists of a straight copper
tube 1-2 ft. in length, having a branch tube attached at one end
and coiled round it as shown in Fig. 27. The tube and coil are placed
1 /. Soc. C/iem. hid., 1891, 10, 347. - Ibid., 1896, 15, 326.
THE ARCHBUTT VOLATILITY TEST
75
in an air-oven provided with a thermometer; the ends of the tube are
closed by brass screw-caps, one of which is provided with an exit-
tube. The sample of oil is placed in a platinum boat which is placed
in a glass carrier. The current of air in which the drying is effected is
first heated to the required temperature in the coil before entering the
actual drying tube, whereby a constant temperature is ensured ; it is
maintained at a constant speed by means of a suitable regulator.
The sample is exposed to the current of air for exactly one hour ;
0-5 g. of oil is taken for each determination, and the temperature of the
oven is varied to suit the requirements of the test. For cylinders
working at 150 lbs. pressure per square inch, the oil is tested at 370" F.
CcpperpifjA Oil tray Clasaiuhe
Fio. 27.
(188° C), and should not lose more than o-5-i-o per cent, in weight. At
400° F. ( = 235 lbs. pressure) the loss of weight of cylinder oils is about
two and a half times as great as at 370° F.
A flashing point apparatus in use in the United States, known as
the New York State Board of Health Tester, is so fitted as to allow of
the determination of the evaporation loss as well as of the flashing
point. The outer bath of the tester is charged with water, whilst a
known weight of the oil under examination is placed in the usual
container. By keeping the water boiling, the oil is maintained at
208^-210° F. (about 98^-5 C.) during five hours, whereupon it is rapidly
cooled to about 10° F. (5°-5 C.) and again weighed. Under these con-
ditions a good machinery oil ought not to lose more than o-i per cent.
The apparatus is apparently not intended for determining evaporation
losses at higher temperatures.
76
LUBRICANTS
2. F. Schreiber's Apparatus.' — This is a modification of the
apparatus desii^ned b\' Iluldu for the determination of the volatility, the
object of which is to obtain indications of the actual efficiency of a
lubricant under working conditions.
The oil to be tested is spread out in a thin layer and is uniformly
heated from all sides, as in the cylinder of the steam engine.
The oven (Fig. 28) consists of a heating jacket in which high-boiling
compressor oil is heated by a Bunsen burner. If the gas pressure is
constant, the variations of temperature do not exceed ± 2 . The oils
are placed in shallow glass dishes of So-85 mm. diameter and 20 mm.
deep, which are placed on a perforated shelf in the middle of the oven.
The top of the oven has six openings to allow the vapour to escape, or
to allow steam or gases to be passed through the oven in case it is not
desired to carry out the test in air. 10 g. of the oil are weighed out
into each of the dishes and heated for ten to twenty-four hours at 200^
The loss of weight by evaporation, and the increase of the amount of
substances insoluble in benzine and benzene are ascertained. It has
been found that in the case of oils which have not proved efficient under
practical conditions, both of these amounts are high (Oils I. and II. in
Table 17). Specific gravity, viscosity, and flashing point do not always
give reliable indications of the volatility, as is shown by a comparison
of the samples II. and V. in the subjoined Table, which have the same
flashing point and specific gravity, but which gave very different losses
on heating, viz., 878 per cent, in the case of II. and only 1-35 per cent,
in the case of V. The results obtained in the case of five mineral oils
are shown in Table 17 ; of these the two first proved unsatisfactory
under working conditions.
Table 17.
Oil number.
Specific gravity
,,. ., fat 100°
Viscosity 1^^ J5Q. ^ _
Flashing point "\ in open/
Burning temperature J vessel \^
Per cent, of T Insoluble in benzine
asphallic -! InsoIul:ile in ether-
substances y alcohol
Loss on evaporation after 16 hours,
per cent. . . • . .
Asphallic substances after healing,
insoluble in benzine, per cent. .
Insoluble in hot benzene after
heating
Other characteristics
0-904
2 '65
317°
362=
0-16
1-07
13-6
II.
0-905
2-30
331°
372°
0-04
0-54
8-78
at 250
- 10-8
mostly
insoluble
oil was solid
and resembled
parchment
•13
4-04
oil was a
tough doughy
mass
in.
IV.
0-906
0-916
6-24
6-32
2-34
2-34
338°
319°
382°
374°
0-05
0-64
1-59
1-65
1-15
3-66
0-908
7-00
2-51
332°
378°
0-05
2-29
1-35
at '280'
1-26 1-84 1-28
1-02 1-46
0-98
liquid, without
appieciable change
1 Z. angew. C/iem.^ 1910, 23, 99 ; /. Soc. Chcm. Ind., 1 910, 29, 202
Fig. 28.
I To Jace page 76.
THE FLASHING POINT
77
The great increase of asphaltic substances is due to oxidation, as
was proved by the influence of steam and gases on the evaporation and
character of the oil. A certain amount of formation of asphaltic
compounds occurred even on heating in steam or carbon dioxide, but
this may be ascribed to the presence of small quantities of oxygen ;
at any rate it was much less than when the oil was heated in air. A
mineral oil containing 0-07 per cent, "insoluble" in benzine gave the
results shown in Table 18.
Table 18.
Results of evaporation.
In a current of
air.
In a current of
carbon dioxide.
In a current of
steam.
Quantity evaporated in 24 hours at 280° .
Insoluble in benzine, per cent. .
Insoluble in hot benzene, per cent.
Other characteristics
19-15
15-10
13-53
the oil formed
a solid parch-
ment-like mass
5-30
0-99
0-23
15-31
0-16
completely
so uble
V
the oil was liquid without
appreciable change
(b) The Flashing Point.
The "Open" Test. — In the ordinary method of conducting this test
the oil is simply heated up in an open crucible, in which a thermometer
is placed, in a flat sand-bath and the temperature observed at which an
inflammable vapour is given off. Owing to its simplicity this test is
still largely accepted for railways, etc., and is in common use in factories
for purposes of works control, and in trade generally.
A modification of this test proposed by J. Marcusson consists
in applying the mechanical arrangement used in the Abel apparatus
(see section on " Mineral Oils," this Vol., p. 29) for approaching the
flame to the surface of the heated oil.
The Pensky-Martens Apparatus (Fig. 29). — Whereas determina-
tions by the open test are subject to many uncertainties, and there
is great difficulty in preventing the dissipation of vapour over the oil-
surface, this apparatus is fitted with devices which ensure even heating,
convenient approach of the igniting flame, and ready observation of
the flash. A further advantage of the Pensky tester is that it gives
results with low-flashing oils which stand in definite relation with the
results by Abel's apparatus. As compared with the " open test," it is
very sensitive to minute quantities of low petroleum fractions in other-
wise high-flashing oils, the vapours of the former, which would simply
escape in the open test, being detected by a low flashing point.
The oil to be tested is poured up to a mark M into the container E,
which stands 34 mm. high, and is heated by a triple burner. E rests,
(8
LUBRICANTS
with an air-space interposed, in the iron bath H, which is protected
against radiation by an asbestos-Hned brass mantle L. When the
temperature of the oil has risen to about lOO , the hand-worked stirrer
J is brought into operation, and is kept agitating without interruption
until the end of the test. Fig. /; is a cross section of the cover and Fig.
c a holder for removing the hot container. From 120 onward the
Fio. 29.
ignition flame Z, burning gas or colza oil, is plunged into the upper
part of E at intervals of 2° ; later on, when the flame is seen to increase
in size on insertion, it is applied at one-degree intervals, until flashing
sets in. The temperature read on the thermometer T may be corrected
for the errors of the instrument itself, and for the column of mercury
protruding above the heated region. Not infrequently the flash extin-
guishes the ignition flame. On immediately again introducing the
flame, the same flashing point need not necessarily be observed, since
THE PENSKY-MARTEN'S APPARATUS
79
further heating may be requisite to collect a sufficiency of inflammable
vapour.
The heating should be so controlled that, with continual agitation,
the temperature rises 6'-iO° per minute up to 120' , and only 4°-6° per
minute from about 20" below the flashing point.
It rarely happens that the flashing point of a lubricating oil falls
below 120°, but when this is the case, stirring should be begun at 80°,
and the insertion of the ignition flame at 100°. In order to rekindle
the latter when it goes out, a stationary flame S is kept burning near it.
Repeated determinations usually agree to within o°-2'' ; the
difference rarely amounts to 3°. Two determinations, of which the
mean is taken, are therefore, in general, sufficient.
Fig. 30.
Much less concordance may be expected when the oil consists of a
mixture of mineral oils and glycerides.
A sample of oil which has once undergone a flashing test should not
be used for a repetition of the same, since it has necessarily lost some of
its most volatile constituents.
When an oil containing water is heated in the Pensky apparatus
the steam spasmodically generated has the effect of blowing out the
ignition flame. If serious trouble be experienced from this cause, it
is well to dry the oil beforehand by treatment with calcium chloride and
filtration. There is no difficulty in distinguishing the blowing out of the
flame by steam from that which takes place in the neighbourhood of the
flashing point.
80
LUBRICANTS
If lubricants should contain lamp oil, and hence flash too low to be
dealt with by Pensky's apparatus, the Abel tester may be used
(see p. 29).
J. Gray's Apparatus.' — This apparatus is frequently used in this
country for the determination of the flashing point of heavy mineral
oils. A section of the cup and surrounding iron jacket is shown in
Fig. 30, and the complete apparatus in Fig. 31. The cup rz which is
m
Fig. 31.
made of brass is closed by a tightly fitting lid, through the centre
of which passes a steel shaft carrying two sets of stirrers, one above and
the other below the surface of the oil. A small bevelled wheel // is fixed
on the top of the shaft and geared with the vertical wheel £■ which is
worked by the small handle d. The lid is provided with four openings,
one of which serves for the insertion of a thermometer, whilst the other
three serve for the mechanism provided for the testing of the flashing
point.
' /. Soc. Chem. IiiJ., 1891, 10, 348.
OPTICAL TESTS 81
To carry out the test the cup is filled with the oil up to a mark
inside which is ih in. from the bottom, the test-lamp lighted, and the
flame adjusted so that it is about -|- in. high. The oil-cup is then heated,
either by means of a Bunsen burner or on a sand-bath, the stirrers being
rotated so that the temperature of the oil rises about 5" per minute at
first, and then less rapidly as the flashing point of the oil is approached ;
it is important not to work the stirrers too rapidly as otherwise oil is
sent up the side of the vessel, whereby the ratio of the surface of oil
exposed to the air space is increased, with the result that the
observed flashing point may be 2° to 3° too low. The mechanism
of the apparatus is then brought into play, whereby the stirring
of the oil is stopped, the cover of the cup opened, and the test-
lamp tilted into the opening over the cup. The temperature at
which a slight explosion is produced is taken as the flashing point
of the oil. If there is no flash the heating is continued as before
and the test repeated.
Differences between the Flashing- Points by the "Open" and
"Closed" Tests. — In the "open" test vapours arising from the oil are
soon carried away by atmospheric convection currents, whereas this
cannot occur to any extent in the Pensky - Martens or in Gray's
apparatus. Consequently the flashing points always come out higher
by the latter than by the former method. With ordinary mineral
lubricants the differences range from 5°-40^ according to the flashing
point.
(c) The Ignition Point.
The ignition point or " Fire Test " is the lowest temperature
at which the oil will continue to burn after a flame has been brought
into contact with its surface for a few seconds. It is determined after
the flashing point has been taken by removing the cover, continuing
the heating, and testing with a small flame.
VII. OPTICAL TESTS.
Optical Activity.
Certain crude petroleums and the fractions distilled from them
slightly rotate the plane of polarisation. Rosin oils, on the other hand,
exhibit considerable rotations.
Mineral oils have specific rotatory powers ofo to +i°-2 rarely rising
to +3°- 1. The rotation of rosin oils fluctuates between +30" and 44°.
(Demski-Morawski records +50".) Fatty oils do not appreciably rotate
the plane of polarised light, with the exception of sesame oil, which
has a specific rotation of from +3°- 10 to 9", castor oil, which has a
rotation of from +4o''-7 to +43", and some rarer oils and fats.
Ill F
82 LUBRICANTS
The rotatory power is determined with the usual polarimetric
apparatus. Strongly coloured oils are first dissolved, in known con-
centration, in a colourless, inactive mineral oil, or in petroleum spirit or
benzene.
If [a] D be the specific rotation of the substance, the formula for
calculation in the case of the original oils is : —
^"^•^ = ltd
and in the case of solutions: —
r n looxa
L«Jd =
ly.pY.d
where a is the angle of deviation read off on the polarimeter, / the
length of the column of liquid, d the specific gravity of the oil or of
the solution, and/ the percentage concentration of the latter.
Refractivity.
The refractive index permits of the detection of rosin oil in lubricants.
Zeiss' rcfractometer (see section on "Oils, Fats, and Waxes," this Vol.,
p. 109), is the most serviceable instrument for the determination.
The refractive index of high-boiling rosin oils is from i-530-i-55o;
that of mineral lubricating oils from i-490-i-5oo; that of colza oil from
I -472- 1 -474; and that of neat's-foot oil from 1-467- 1-470, all at 18'.
Chemical Tests.
viii. acidity and free alkali.
In pale refined mineral oils there is no free acid, or at most traces
(up to 003 per cent., calculated as SO3) may occur. Dark oils may
contain up to 0-3 per cent., although their normal acidit)- may be
taken to be 0-15 per cent, or less; if waste oils have been added the
acidity may rise up to 0-5 per cent. The acidity is due either to
resinous substances or to naphthenic acids of uncertain molecular
weights ; the acidity is expressed either in terms of SO.} or as the "acid
value." For lubricants the acidity is stated on the Continent in terms
of SO.J. i.e.^ the number of grams of SO3 equivalent to the potassium
hydroxide required for the neutralisation of the free acids in icx) g.
of the oil. The "acid value" represents the number of milligrams of
potassium hydroxide required for the neutralisation of i g. of the oil.
1 per cent. SO3 is equivalent to an acid value of 14 ( = 705 per cent,
oleic acid).
Free sulphuric acid and free alkali due to traces of these substances
CHEMICAL TESTS 83
left from the refining processes are very rarely met with in lubricants ;
they are detected and determined in the usual manner after extraction
with hot water. The acidity of oils is determined by titrating either
their ether-alcoholic solutions or their alcoholic extracts.
Pale Oils. — For the estimation in this case lo c.c. of the sample are
washed with 150 c.c. of a neutralised mixture of two parts of absolute
alcohol and one of ether into a flask which already contains a little of
the same mixture, i c.c. of i per cent, alcoholic solution of phenol-
phthalein is added, and the titration is carried out with standardised
alcoholic sodium hydroxide solution of such a strength that i c.c.
corresponds to 0-004 S- SO3 (i.e. decinormal).
Dark Oils. — In this case 20 c.c. of oil are well shaken, after warm-
ing, if necessary, in a stoppered measuring cylinder with 40 c.c. of
neutralised absolute alcohol. The liquid is allowed to settle over night,
and 20 c.c. of the alcoholic layer are then withdrawn with a pipette, and
titrated as described above. If the acidity exceeds 0-03 per cent., the
alcoholic liquid is poured off and the oil shaken up once or twice with
a fresh 40 c.c. of alcohol, and again titrated.
The Detection of Mineral Acid is confined to sulphuric acid.
About 100 c.c. of oil are shaken with twice the volume of hot distilled
water in a capacious flask ; after the two layers have separated, 20-30
c.c. of the aqueous extract are withdrawn with a pipette, filtered clear,
and tested with a drop of methyl orange solution (03 g. per litre).
Further portions of the aqueous extract may be tested for added glue,
soap, salt, etc. (see p. 95).
Mineral oils thickened with soap yield emulsions which refuse to
separate into two layers ; these emulsions invariably show a decided
alkaline reaction.
In the case of mineral oils (especially those intended for com-
pressors) which are artificially coloured with coal-tar dyes, the
disturbing influence of the dyestuff may be obviated by proceeding in
one of the following ways : —
a. If the dyestuff is soluble in hydrochloric acid, a solution of the oil
in petroleum spirit is shaken repeatedly with dilute hydrochloric acid ;
this is then removed by thorough shaking with water. The decolorised
solution is then titrated as above.
6. If the dye is insoluble in acid, the oil is first treated with tin and
hydrochloric acid, whereby the colouring matter is, as a rule, reduced to
the leuco-base or other colourless derivative. The decolorised oil is
then dissolved in petroleum spirit, washed free from acid, and titrated.
y. A solution of the oil in petroleum spirit is shaken with a
measured quantity of A^io alcoholic sodium hydroxide (containing
about 50 per cent, of water). The whole of the liquid is then titrated,
using phenolphthalein as the indicator, until the aqueous layer is
84 LUBRICANTS
colourless. The total acid required is subtracted from the amount
corresponding to the sodium h\droxide added ; the difference repre-
sents the acidity of the oil.
S. U the dyestuff is insoluble, or nearly so, in alcohol, it is often
possible to extract the oil with hot 80 per cent, alcohol ; the (almost)
colourless extract can then be titrated.
Oils containing soap as well as colouring matter may be dealt with
directly either by method y or 0 ; but it is better, whenever possible, to
free the oil from soap by extraction with petroleum spirit or anhydrous
acetone.
Mineral acids can be detected just as easily in d}'cd as in undyed
oils by means of methyl orange, since the dyestuffs do not pass into
aqueous solution.
In dyed oils which contain Fatty Admixtures, the determination of
acidity may be conducted by methods a, y, or 0. Method /3 is inad-
missible, since the fatty matter may become hydrolysed by concentrated
hydrochloric acid.
Thus the acidity in a blue-black leather grease, consisting of waxes,
oil of turpentine, and dyed with nigrosine, was determined by boiling
up 5 g- of the grease with petroleum spirit, allowing to cool, and
filtering ; this operation was repeated several times. Most of the dye
remained in the residue, the solutions being only slightly coloured.
They were then repeatedly extracted with dilute hydrochloric acid,
washed thoroughly with water, and titrated.
Differentiation of Naphthenic and Fatty Acids. — To ascertain
whether the free acids present in an oil are naphthenic or fatty acids,
Davidsohn ^ has recourse to the solubility in water of the alkali-earth
salts of the latter. The alkali-soap is dissolved in water, an excess of a
10 per cent, magnesium chloride solution added, the whole boiled, and
the precipitate filtered off. The filtrate is concentrated on the water-
bath, and treated with a few drops of hj'drochloric acid, when the
presence of naphthenic acids is indicated by the solution becoming
strongly turbid.
IX. ROSIN IN LUBRICATING OILS.
Qualitative Detection. — The presence of rosin in mineral oils is
indicated by high acidity. An acidity of i per cent, of SO3, or an acid
value of 14, corresponds to about 9 per cent, of rosin (colophony).
Rosin is characterised by an acid value of from 146-170, a saponifica-
tion value of from 167-194, and an iodine value of from 100-125.
In order to isolate the rosin, the oil is thinned with petroleum spirit
and extracted repeatedly with dilute sodium hydroxide solution. From
' Seifensieder Zeit.y 1909, Nos. 51 and 5a.
"GUMMING" OF OILS 85
this solution the rosin is separated by mineral acid. It is identified by
the above characteristics, its specific gravity, and by means of the
Liebermann-Storch colour reaction (see " Detection of Rosins in Oils,"
this Vol., p. 130). For this test the substance is dissolved in a little
acetic anhydride, and a drop of sulphuric acid of sp. gr. 1-53 added;
colophony gives a violet coloration.
The Quantitative Determination of Rosin. — If fatty oils and fatty
acids are absent, this is effected by extracting the oil with sodium
hydroxide solution, acidifying the solution, and weighing the separated
rosin ; when fatty matter is present as well as rosin, the separated mass
contains both. The rosin is then separated from the fatty matter by
Twitchell's process (see " The Determination of Rosin in Soap," this
Vol., p. 195).
For this purpose so much oil is weighed or measured out that
about 5 g. of rosin and fatty acids will be obtained. The mixture is
saponified by means of alcoholic alkali, and the soap solution thus
obtained is freed from unsaponifiable matter by extraction with ether
or petroleum spirit, and is then evaporated to dryness ; the residue is
taken up with water, acidiQed with hydrochloric acid, and extracted with
ether. The aqueous liquid is again neutralised, evaporated to about
25 CO., acidified, and again extracted with ether. The combined
ethereal extracts are then evaporated down. The residue is then
subjected to the Twitchell process as described under " Soap," this Vol.,
p. 195.
X. LIABILITY TO "GUM" OR " RESINIFICATION " OF LUBRICANTS.
Pale mineral oils, on exposure in thin layers, volatilise almost
completely at 100° within thirty-five hours.
Dark oils containing still residues scarcely thicken at ordinary
temperatures, even after a very long time ; but at 50''- 100" they are apt
to resinify to a considerable extent, since the more volatile hydrocarbons
partly evaporate off and partly become oxidised, leaving a residue
of pitch-like bituminous matter.
In order to test an oil in this respect, a drop is allowed to spread on
a sheet of glass 5 by 10 cm., and kept at 50° for machinery oils, or at
100° for cylinder oils ; from time to time, say once a day, the sample
is cooled down and its consistency noted.
In consequence of the modern method of ring-lubrication and the
mode of lubrication of turbine engines, where the same oil remains for a
long time on the bearing, the requirements of the user, as regards
liability to gumming of oils, especially of oils subjected to high tempera-
tures for considerable periods, have become much more stringent than
formerly, when the oil used for lubrication ran away. Hence more
86 LUBRICANTS
searching methods of detennining the liabih"ty of an oil to undergo
change are required.
R. Kissling^ has proposed to determine the "tar number," the
"coke number," the "tar formation number," and the "coke formation
number," as a means of examining lubricants from this standpoint.
The "tar number" is the term he applies to the percentage content,
which can be extracted from the oil with hot alcoholic sodium hx-droxide
at 80', and after acidification can be extracted from this solution with
benzene. The "coke number" is determined on the residual oil after
extracting the "tar," and is the quantity of "coke-like substances"
insoluble in petroleum spirit. If the oil is heated for fifty hours to 150^,
and the "tar" and "coke" numbers are again determined as described,
the quantities obtained are termed the "tar formation number" and
" coke formation " number respectively.
As Kissling's proposals have not yet been adopted by other workers,
it will suffice to record the following results : —
Pennsylvanian oils. Sum of tar and coke formation numbers . 0-2 to 0-5
Russian oils „ „ „ . 1-2
Texas oils „ ,, „ . 2-2 to 28
The higher these numbers in an oil, the more rapidly it is found to
undergo changes in practical use.
XI. FORMOLITE REACTION (A. NASTJUKOFFS TEST).2
For the determination of the unsaturated cyclic hydrocarbons in
a mineral oil, Nastjukoff treats the oil with formaldehyde in presence of
concentrated sulphuric acid, whereby a solid yellow product is separated
for which the name " formolite " has been proposed. The " formolite-
number" is the amount of air-dry "formolite" obtained from 100 g. of
an oil.
The test is carried out by adding 30 c.c. of concentrated sulphuric
acid to the same quantity of the oil, and then, without shaking, adding
15 c.c. of a 40 per cent, formalin solution, whilst cooling the mixture.
When this has cooled to the ordinary temperature, it is poured
into water, neutralised with ammonia, filtered off on a Buchner funnel,
and washed, first with petroleum spirit or ether, and then with hot
water. After drying in an oven at iio''-ii5'' the product is bright
yellow to dark brown in colour, amorphous, and, according to Nastjukoff,
insoluble in the usual solvents ; V. F. Herr, however, found it to be
distinctly soluble in a large quantity of hot chloroform (i : 100), and has
suggested applying the test directly to crude oils without previously
1 Chem. Zeit., 1906, 30, 932; 1907, 31, 328 ; 1908, 32, 938 ; and 1909, 33, 521.
- Petroleum, 1909, 4, 1336, 1397,
THE FORMOLITE REACTION 87
treating the oils with sulphuric acid, as Nastjukoff does. Herr
obtained the following values : —
Table 19.
Crude oil from
Formolite number.
Binagdy ....
Bibi-Eybat ....
Balachany ....
63-3
28-3
21-3
These figures correspond to the chemical behaviour of the oils, as
the Balachany oil is the richest in naphthenes, and the naphthenes
do not yield " formolite." This reaction furnishes valuable practical
information as to the working up of crude naphtha.
The formolite numbers of various American and Russian lubricating
oils (cylinder oil, machine oil, spindle oil, vaseline oil), given by
Nastjukoff,^ show that all these oils consist essentially of unsaturated
cyclic hydrocarbons. Thus American cylinder oils gave formolite
numbers of 92-97, Russian cylinder oils of from 58-87, and vaseline oils
of from 7-8-22.
Herr- has recently pointed out that formalin maybe advantageously
replaced by methylal CH2(OCH3).„ as the latter acts at the same time
as a solvent for the oil, and as a condensing agent, and, moreover, forms
a better condensing agent for the detection of benzene hydrocarbons
than does formaldehyde.
XII. BEHAVIOUR TOWARDS METALS.
Corrosion of bearings by machinery and axle oils never takes place
to an appreciable extent at ordinary temperatures, unless fatty oil
containing free acid is present. Comparative tests, carried out first
by I. I. Redwood,^ may be made by immersing polished and weighed
plates of the metal concerned, 30 or 50 mm. square, in the oil contained
in glass or porcelain basins, and heating them, protected from dust, in an
air-bath. From time to time during the period of the test, which may
be continued for weeks, the plates are cleaned with tissue paper and
ether, inspected, and weighed. It must, however, be pointed out
that these tests by no means furnish reliable guidance as to the
behaviour of the oils on a practical scale.
XIII. MOISTURE.
Qualitative Detection. — The presence of moisture in pale oils is
usually indicated by a more or less pronounced cloudiness, especially
1 Petroleum, 1909, 4, 1336, 1397.
2 Chem. Zeit., 1910, 34, 893 ; J. Soc. Chem. Ind,, 1910, 29, 1094.
'^ J. Soc. Chem. htd., 1886, 5, 362.
88 LUBRICANTS
after the sample has been shaken. By heating on the water-bath, the
oil loses its cloudiness, which dififerentiates it from the cloudiness caused
by the separation of paraffin wax, etc.
Quantitative Determination. — From 10-12 g. of the sample are
weighed into an open glass or porcelain dish of 6-10 cm. diameter; if
much moisture is present, 3-5 g. are weighed out and mixed with lo-i 5 g.
of the same oil, previously dehydrated with calcium chloride and
filtered. The dish is heated on a briskly boiling water-bath until no
more froth is formed, when the oil is stirred with a glass rod. Side by
side another sample, but which has been previously dehydrated, is treated
in exactly the same way. The percentage loss in weight of the latter is
subtracted from that of the former ; the difference represents the moisture
in the original sample. In the case of practically non-volatile cylinder
oils, the blank test may be omitted.
XIV. MINERAL ASH.
No ash is obtainable if the oil is completely soluble in petroleum
spirit and benzene, and the aqueous and hydrochloric acid extracts of
the oil give no perceptible residue on evaporation. Well-refined
machine oils should not contain more than o-oi per cent., and cylinder
oils not more than o-i per cent, of ash, which should not, however,
contain any appreciable quantity of alkali.
For the determination of the ash 20-30 g. of the oil are carefully
evaporated in a platinum dish over a small flame, until the residue is .
solid ; this is incinerated and the residual ash weighed. If the
carbonaceous residue is difficult to burn off by simple heating, the
combustion is assisted by adding ammonium nitrate.
XV. PRESENCE OF SOAP.
It has been pointed out above that solid lubricants contain alkali- or
lime-soaps which are purposely added.
The presence of alkali-soap is indicated by the oil, on being
shaken with water, giving an emulsion having an alkaline reaction to
phenolphthalein.
After acidification with a mineral acid, sodium or potassium may
be detected by the usual methods. The presence of ammonia-soaps
is recognised by the smell of ammonia (see also p. 103). Lime-
or alumina-soaps are best tested for in an acid extract of the
oil.
Quantitative Determination. — For the quantitative determination of
soap, use is made of the fact that, by agitating the sample with mineral
acid, the soap is decomposed, its equivalent amount of free fatty acid
ADMIXTURES OF FATTY OILS 89
being dissolved by the oil, the total acidity of which is then greater by
that amount than its original acidity. The nature of the soap-acids
may be ascertained by isolating them and examining them according to
the methods described in the following Section. The soap-bases are
identified in the aqueous solution.
To carry out the determination lo c.c. of the oil are dissolved in a
separating funnel in 40-60 c.c. of ether. The solution is thoroughly shaken
with so much dilute hydrochloric acid that the aqueous layer remains
distinctly acid. The latter is separated off, and the residue repeatedly
washed with water until free from acid. Any emulsions formed are
broken by adding more ether or a strong solution of common salt, or a
little alcohol, which is poured on without shaking.
If the emulsion persist, nevertheless, warm petroleum spirit is
substituted for ether, and the solution washed with w^arm water.
Separation having been effected, the ethereal solution is titrated for
acidity as described on p. 82. Finally, the acidity of the original oil is
determined ; the difference between the two acidities corresponds to the
amount of fatty acids present as soaps.
XVI. ADMIXTURES OF FATTY OILS.
To detect the presence of fatty oils rapidly, 3-4 g. of the sample are
heated in a test tube with either sodium or sodium hydroxide for a
quarter of an hour in a paraffin-bath, pale oils to 230'', dark and cylinder
oils to 250°. In the presence of 0-5 per cent, of glycerides in pale oils, of
2 per cent, in dark oils, a formation of soapy froth will be observed, and
the oil will gelatinise on cooling.
It should be pointed out, however, that gelatinisation may take
place without frothing, if rosin and naphthenic acids are present.
Quantitative Determination. — The percentage of fatty oil is
determined quantitatively by heating 10 g. of the sample for half an
hour with 25 c.c. of 2/A^ alcoholic potassium hydroxide and 25 c.c. of
benzene under a reflux condenser; 25 c.c. of water are then added,
and the solution is washed into a separating funnel with 50 per cent,
alcohol. The soap solution is shaken out several times with 50 c.c. of
low-boiling petroleum spirit, until the last extract leaves no oily residue
on evaporation. The united petroleum spirit extracts are shaken out
three times successively, with 15 c.c. of 50 per cent, alcohol to which
a trace of alkali has been added. This alcohol extract is shaken out
once with petroleum spirit, and is then added to the soap solution.
The petroleum spirit solutions are evaporated, and the residue heated
on a water-bath until the solvent is driven off completely. After
drying for five minutes at 100" the mineral oil thus obtained is
weighed. The difference between the amount of mineral oil thus
90 LUBRICANTS
found and the quantity of oil originally taken gives the content of
saponifiable fat.
If approximate data suffice, it is simpler to determine the saponifica-
tion value of the sample (see next section, " Saponification Value,"
p. 114).
For this purpose 4-10 g. of the oil are heated for half an hour under
a reflux condenser with 25 c.c. of A^/2 alcoholic potassium hydroxide, or,
in the case of very thick oils, 25 c.c. of A^'i potassium hydroxide and
the same volume of benzene. The excess of alkali is then titrated back
with NI2 hydrochloric acid, using phenolphthalein as the indicator, and
the saponification value calculated as described in the next Section,
p. 115.
For the calculation 195 may be taken as a mean saponification value
of the oils that come under consideration, with the exception of rape
oils, for which 175 should be taken; the saponification value of mineral
oil is, of course, nil. Hence, e.g., if the sample has the saponification
value 97-5, the percentage of fatty oil, if rape oils be absent, is 50 per
cent. Any alkali necessary to neutralise free acid in the oil (acid value)
must, of course, be deducted from the saponification value, and the
difference calculated to glycerides.
For exact determinations the fatty acids are separated and examined
as described in the following Section, p. 130.
In the presence of wool grease (the saponification value of which
is about 105), a complication arises owing to the higher alcohols of the
wool grease remaining with the unsaponifiable mineral oil. In this
case the latter is boiled, after removal of the soap solution, with an
equal weight of acetic anhydride for two hours under a reflux condenser,
whereby the alcohols are converted into esters. These remain dissolved
in the warm acetic anhydride solution which is separated off; the
mineral oil is then washed several times with a few cubic centimetres
of warm acetic anhydride in a separating funnel. From 3-5 per cent,
of mineral oil are lost in this process, and must be duly taken into
account. Owing to the fact that wool grease itself contains hydro-
carbons, and further that it is not completely saponified by boiling with
alcoholic alkali, quantitative determinations of wool grease by the
method described above, yield only approximate results.
The Identification of the Fatty Matter. — This is carried out by
the methods described in the following Section, pp. 130 et seq.
XVII. ROSIN OILS AND TAR OILS.
Rosin Oils. — Heavy rosin oils, boiling above 3CX)°, are produced by
the destructive distillation of colophony, light rosin spirit or pinolin
coming over in the first runnings.
ROSIN OILS AND TAR OILS 91
Crude rosin oil is mainly a mixture of hydrocarbons (which consist,
according to Bruhn and A. Tschirch/ principally of reduced retenes) ;
according to the care with which it has been distilled it may contain up
to 30 per cent, of rosin acids.
Crude and refined rosin oils find application as electrical insulators,
and in the manufacture of lubricants, varnishes, and water-soluble oils.
Rosin oil dissolves in twice its volume of absolute alcohol to the
extent of 50-100 per cent,, in mineral oils to 2-15 per cent., and in very
light mineral oils to 35 per cent. It is miscible in all proportions with
acetone, whereas mineral oils require several volumes for complete
solution.
The refractive index of rosin oils is I-535-I-550 at 18", that of mineral
oils I-490-I-507. The specific gravity varies from o-88o-o-9i5. Rosin
oils are strongly optically active: [ajo ranges from +30° to +50°;
mineral oils, on the other hand, are as a rule inactive, or at most have
The iodine value of rosin oils varies from 43-48. It may be pointed
out that cracked petroleum distillates have iodine values, sometimes
reaching 70.
When a few cubic centimetres of rosin oil are shaken with an equal
volume of sulphuric acid of sp. gr. i-6, a deep red colour results. This
colour reaction is due to impurities which are absent from well-refined
rosin oils, such as are now placed on the market.
On adding to a mixture of i c.c. of oil and i c.c. of acetic anhydride
a drop of sulphuric acid of sp. gr. 1-53, a fine violet colour is produced
(Liebermann-Storch reaction, see p. 130). This reaction is given by
rosin as well as by rosin oil. When both are present together rosin
oil may be detected by its odour, and by the further characteristics
described below.
If a lubricating oil is suspected of containing rosin oil, the examina-
tion must be based on the properties described above ; if necessary, the
tests are performed on that portion of the lubricant which is soluble in
absolute alcohol in which the rosin oil is much more soluble than the
mineral oil.
Determination of Rosin Oil in Mineral Oils. — The best method for
this determination is that of E. Valenta, which is based on the difference
in the solubilities of rosin oils and mineral oils in glacial acetic acid at
50"; 10 c.c. of glacial acetic acid dissolve 17788 g. of the former, and
from 0-2833-0-6849 g. of the latter.
For the determination, 2 c.c. of the unsaponifiable matter are mixed
in a test tube with 10 c.c. of glacial acetic acid, and the tube, loosely
closed by a cork, is immersed in a water-bath at 50° for five minutes
^ Chem. Zeit., 1900, 34, 1105 ; Arc/i. P/iaim., 1903, 291, 523.
2 Rakuzin, C/iem. Zeit,, 1904, 38, 574.
92 LUBRICANTS
the contents being frequently shaken. The mixture is then filtered
through a moistened filter, and the middle portion of the filtrate
collected. Part of this is then weighed off accurately, and the content
of acetic acid determined by titration with Nji sodium h}-droxide.
The difference between the weight of the acid taken and the weight
thus found corresponds to the quantity of rosin oil dissolved.
The accuracy of this method has been confirmed by J. H. Walker
and C. D. Robertshaw.^
Rosin acids, if present in the rosin oil, influence the solubility, and
render the determination inaccurate. In this case, the greater part of
the acetic acid is neutralised, the solution diluted with water, and the
rosin oil extracted with ether,^
According to the method due to L. Storch,^ which applies only in
absence of fatty oils, lo g. of oil are well shaken with five parts of warm
96 per cent, alcohol. After cooling, the alcoholic solution is separated
off, and the residue washed with a small quantity of the solvent. The
combined solutions are evaporated in a tared conical flask and heated
on the water-bath till free from alcohol. The weighed residue (A) is
then treated with ten parts of alcohol, and the substance dissolved is
again isolated and weighed (B). There will still be some mineral
oil in B, and its amount is calculated as follows : — Suppose a grams
of alcohol to have acted upon the original material, and b
grams upon A; then a-b grams dissolve A-B grams of mineral oil;
therefore b grams dissolve ^ j— grams of the same. This
latter amount is worked out and subtracted from B, and thus gives
the quantity of rosin oil in the original 10 g. of mixed oil.
Detection of Mi)ieral Oil in Rosin Oil. — Mineral oils afford no very
characteristic qualitative reactions, and when there is less than 15 per
cent, in a sample of rosin oil, no information can be gained by the
ordinary solubility methods. Holde's procedure for detecting small
admixtures of mineral oil is based on differential solubilities and on
differential refractivities. According to this method 10 c.c. of oil are
shaken up with 90 c.c. of 96 per cent, alcohol at the ordinary temperature.
If any considerable amount of oil remains undissolved, the presence of
much mineral oil is indicated. In this case the insoluble oil is allowed
to settle out overnight, rinsed with alcohol, and tested by the refracto-
meter. A refractive index of less than 1-533 ^^ ^8° is evidence of
mineral oil.
Heavy rosin oils lose much more weight at loo'^ and iSo' than
mineral oils, even than light spindle oils. Similarly the flashing point
1 Anatys/, 1902, 27, 238.
^ A. H. Allen, Commercial Organic Analysis, 2nd ed., vol. ii., p. 465.
^ Ber. Osterr. Gesell. z. Forder. der Cliem. Ind., 1891, 9, 93 ; /. Soc. Chem. I mi., 1 891, 10, 276.
COAL-TAR OILS
93
of rosin oil is relatively lower. The following Table affords some
guidance for examination : —
Table 20.
Loss on heating (per cent.).
Flashing point.
For 5 hours
at 100°.
For 2 hours
at 170°.
Peusky.
Open test.
Heavy rosin oil
Spindle oil . . .
Machinery oil .
0-4 to 0-8
0-05 „ 0-10
0-06 „ 0-13
5-6 to 7-4
0-5 „ 1-8
0-6 „ 1-05
109° to 146°
177° „ 203°
188° „ 195°
148° to 162°
189° „ 213°
205° „ 221°
Coal-tar Oils. — The oils which come under consideration here and
which are used as lubricants in gas-suction pumps and as ingredients
of lubricating greases, are the dead anthracene oils, heavier than water,
and having a characteristic smell of creosote. They are completely
soluble in alcohol at the ordinary temperature, and are dissolved by
concentrated sulphuric acid on the water-bath forming compounds
soluble in water. With - nitric acid of sp. gr, 1-45 they yield nitro-
products with evolution of heat and sometimes with almost explosive
violence. The following method for their determination, which gives
approximate results, has been based on the rise of temperature
produced by this treatment: — 7-5 c.c. of the sample are placed in a
graduated tube, cooled to 15°, and 7-5 c.c. of nitric acid of sp. gr. 1-45,
previously cooled to 15° added; the tube is closed by a cork provided
with a thermometer, the contents thoroughly shaken, and the rise of
temperature read off It is well to try a preliminary test always, in
order to ascertain whether a violent reaction takes place or not, as a
guide to the quantity of the sample to be taken, and the size of the tube
to be employed for the test.
For the differentiation of coal-tar oils from mineral oils the reaction
proposed by E. Valenta^ may be used. This depends upon the
solubility of benzene hydrocarbons as found in coal-tar in dimethyl
sulphate (SOo(OCH3).,) at the ordinary temperature, and the insolubility
of crude petroleum, benzine, illuminating oil, mineral oil, and rosin oil.
A certain quantity of the oil is shaken for a minute in a measuring
cylinder with i|-2 vols, of dimethyl sulphate and allowed to separate,
whereupon the difference of volume is read off
This method has been tested by E. Graefe,^ who found that it gave
almost theoretical values in the case of mixtures of high-boiling coal-tar
and mineral oils, but that in the case of very low-boiling petroleum
derivatives, the solubility in dimethyl sulphate is appreciable. In
1 Chein. Zeit., 1906, 30, 266 ; J. Soc. Chern. Ind.^ 1906, 25, 366.
2 Chem. Rev. Fetl-Ind., 1907, 14, 1X2.
94 LUBRICANTS
lignite-tar oils a constant error of approximately lo per cent, occurs ;
but if this be taken into account, the separation of coal-tar and lignite-
tar oils can be effected by this method. The method has also been
examined by T. W. Harrison and F. IM. Perkin/ who found that
aromatic oils are soluble in dimethyl sulphate in all proportions, but
that mineral oils are not insoluble. Thus 8-5 per cent, of Russian
petroleum was dissolved by its own volume of the reagent, and by
repeated extraction with fresh quantities as much as 80 per cent,
could be dissolved. Hence it is concluded that the method cannot be
applied quantitative!)', although of value as a qualitative test.
Heavy Lignite Oils {cf. the section on "Mineral Oils," p. 53) have
a sp, gr. of 0-89 0-97, and dissolve to the extent of 20-60 per cent, when
shaken with 2 vols, of cold alcohol; the viscosity is usually low. These
oils have a faint smell of creosote ; their properties are, on the whole,
not sufficiently well-marked to render them certain of detection.
XVIII. INDIA RUBBER.
The presence of india rubber in lubricating oils may be recognised
by their tendency to run into threads when drawn out by a glass rod, or
between the fingers. A rough determination of the india rubber may be
effected by dissolving the oil in ether and precipitating with absolute
alcohol. If present in a homogeneous dissolved condition, india rubber
may be regarded as a perfectly harmless ingredient, since it neither
attacks metals nor tends to thicken ; it has the effect of rendering the'
oil peculiarly slippery and adhesive.
As yet there is no standard method of determining the amount of
india rubber in lubricating oils. Methods based on the formation of
addition products, insoluble in acetone, either with nitrous acid or with
hyponitrous acid, have not yet been worked out for the estimation of
india rubber in oils.
XIX. DEBLOOMING AGENTS AND PERFUMES.
Mono-nitronaphthalene, CidH-NO.„ is added to mineral oils to mask
the fluorescence, whilst the presence of an objectionable smell is over-
come by the addition of nitrobenzene. The latter is recognised at once
by its characteristic odour of bitter almonds. Yellow coal-tar dyes,
which are also used similarly to nitronaphthalene, are indicated by their
deep yellow colour. Oils treated with nitronaphthalene become darker
on keeping.
Detection of NitronaphtJialene. — As a preliminary test from 1-2 g.
of the oil are boiled with 2-3 c.c. of concentrated alcoholic potassium
' Analyst, 1908, 33, 2.
IMPURITIES IN LUBRICANTS 95
hydroxide (about 2/A^) in a test tube for a minute or two. In the
presence of nitronaphthalene or nitrobenzene the liquid becomes blood-
red or even violet, owing to the formation of azo-compounds. The
reaction is especially well observed when drops of the liquid adhering to
the upper part of the test tube are gently warmed.
If the colour test has given a positive indication, the following con-
firmatory test proposed by N. Leonard may be applied.^ A few cubic
centimetres of the oil arc placed in a conical flask, and reduced by warming
with tin and hydrochloric acid for five to ten minutes. A piece of platinum
wire may with advantage be placed in the liquid. The acid aqueous
solution is separated from the oil, filtered into a separating funnel, and
treated with sufficient potassium hydroxide to neutralise the acid and
redissolve the stannous hydrox'de precipitate. The presence of nitro-
naphthalene in the original oil is indicated by the characteristic unpleasant
smell of a naphthylamine. This is extracted with 10-20 c.c. of ether and
the ethereal solution evaporated in a glass dish. Naphthylamine then
remains as a malodorous oil of a violet colour. On adding a drop of
hydrochloric acid a semi-solid mass of the hydrochloride is formed ; this,
after evaporating off the excess of acid, gives a clear solution in water.
The solution yields with ferric chloride a bulky blue precipitate which
when filtered off, assumes a reddish-purple colour, whilst the filtrate
shows a fine violet tint.
XX. WATER-SOLUBLE SUBSTANCES.
Glue occasionally finds its way into mineral oils from carelessly
glued casks. It is detected as follows : — 100 g. of the oil are thoroughly
shaken up with boiling water in a conical flask, the aqueous layer
separated off and an aliquot part, say 60 c.c, filtered into a measuring
cylinder, and evaporated to dryness in a glass dish on the water-
bath. If there is an appreciable residue which, whilst hot, seems to
smell of glue, it is extracted two or three times with 5-8 c.c. of hot
absolute alcohol, whereby any soap, if present, is removed. The dried
residue may be weighed. If it consists mainly of glue, the characteristic
smell given off on heating, as also the precipitate obtained from its
aqueous solution by tannic acid, serve as confirmatory tests.
Sodium sulphate, to which (a rarely-occurring) opacity or the break-
ing of mineral oils may be due, is detected in an aqueous extract by
means of barium chloride.
XXL SUSPENDED MATTER.
Mechanical Impurities are detected in pale oils by mere inspection.
1 Chem. News, 1S94., 68, 297 ; J. Soc. C/iem. ImL, 1 891, 13, 69.
96 LUBRICANTS
For their quantitative determination, 5-10 g. of the sample are
dissolved in 100 c.c. of petroleum spirit, or in the case of dark oils in
benzene. After standing overnight the solution is poured through a
tared filter, and the residue washed thoroughly with the same solvent.
The filter is then dried at 105° and weighed.
Bituminous and Pitch-like Matter in suspension in dark oils,
beside mechanical impurities, is determined as described in the section
on " Mineral Oils," p. 10.
Vaseline, Paraffin, Iron-soap, etc. — These may be detected in
the residue after filtration by methods varying with the character of the
sample. Iron-soap, which is a not uncommon impurity, is easily
recognised by the formation of ferric oxide on ignition.
XXII. ASPHALT AND PARAFFIN IN SOLUTION.
The determination of asphaltic substances and paraffin wax, which
must be considered as normal constituents of lubricating oils, is carried
out by the methods described under " Crude Petroleum " in the section
on " Mineral Oils," p. 9.
XXIII. CHANGES LUBRICATING OILS UNDERGO IN USE.
Recovered Oils. — For reasons of economy, used lubricating oils are
collected and again used after some process of purification, whereby
mechanical impurities and moisture are removed. In the laboratory
water is removed by prolonged warming in a salt-bath, or by adding
calcium chloride.
The recovered oils are, as a rule, darker than the original oils.
Recovered cylinder oils, containing fatty oils, usually show a notable
amount of free fatt)' acid, asphaltic substances, and of iron-soap ; the
last-named impurity causes a slight increase of specific gravity and
viscosity.
Solid residues found in slide valves, etc.,^ are extracted first
exhaustively with chloroform. The insoluble residue is treated with
hydrochloric acid, which decomposes iron-soaps and dissolves iron
oxide. The substances insoluble in the acid consist generally of
carbon, sand, etc. ; of these the carbon is determined by incineration.
The portion dissolved by chloroform is treated with petroleum spirit ;
the insoluble portion is generally identical with the original lubricating oil
in specific gravity and elementary composition. The portion insoluble
in petroleum spirit is usually soluble in benzene, and consists of asphaltic
substances.
1 Cf. G. Worrall and J. E. Southcombe, /. Soc. Chem. InJ., 1908, 27, 308 ; J. E.Southcombc,
/(^/f/., 191 1, 30, 261.
VASEUNE 97
Condenser Water being frequently used as feed water for the boilers,
the removal of the emulsified oil by some process of purification is
imperative. To test the efficiency of the purifying plant the oil content
in the water, after filtering, is determined by extracting 1-2 litres
of the water exhaustively in a separating funnel with freshly distilled
ether. The extracts are filtered through a filter paper, the ether
distilled off, and the residue dried for ten minutes at 105° and weighed.
In view of the small quantities obtained, all sources of error must
be guarded against.
E. Graefe recommends the precipitation of the oil in the water by
means of alumina or ferric hydroxide, and the extraction of the oil from
the precipitate.
B. FATTY OILS.
Since mineral oils have been introduced the use of pure fatty
oils as lubricants has been greatly restricted. Nevertheless, consider-
able quantities are still used, either as such or in admixture with
mineral oils.
The suitability of a fatty oil for lubricating purposes is gauged by
the purity of the oil, which is ascertained by the methods given
in the following Section on " Oils, Fats, and Waxes."
C. MIXTURES OF MINERAL AND FATTY OILS.
Mixtures are dealt with, in the main, by the methods described in
the previous section on " Mineral Oils." When it is desired to separate
the fatty and mineral oil constituents quantitatively, the procedure given
on p. 89 is followed.
D. VASELINE.
Two kinds of vaseline are known in commerce. The one is prepared
from crude American petroleum by slow distillation of the volatile
fractions and purification of the residue by means of acid or Fuller's
earth (Chesebrough vaseline). The other is compounded by dissolving
paraffin wax and ceresin in colourless petroleum oils (artificial vaseline,
German vaseline). Though used principally for cosmetic and pharma-
ceutical purposes, vaseline is also, to some extent, applied as a lubricant
and as a rust preventative. The laboratory methods for testing vaseline
do not differ from those which hold good for petroleum derivatives
generally. The specific gravity is best measured at 100° by means of a
hydrostatic balance, the thermometer plummet of which has a range
reaching to 100" ; or, it may be determined with a Sprengel pyknometer.
Chesebrough vaseline is stated to have a sp. gr. of 0-845, artificial
vaseline of 0-827, both at 100'.
Ill G
98
LLliUICANTS
Distinction between Natural and Artificial Vaseline.' — A com-
parison of the viscosities gave the following values : —
Material.
Viscosity (Engler).
45°.
60*.
80°.
100'.
Natural American vaseline .
Artificial vaseline
4-8
does not flow
3-7
does not flow
2-1
1-5
1-6
1-2
Artificial vaseline did not flow in the Engler apparatus even at 65",
whereas when completely molten at 80", and 100 , it is much more fluid
than natural vaseline.
Differences are also observed in the absorption of o,x)-gen. Engler
and Bohm heated quantities of 11-15 g. of vaseline with the addition of
2-3 c.c. of water in sealed tubes, with 53-76 c.c. of oxygen for twenty-
four hours at 1 10 -i 15", with the following results : —
Material.
Absorption of oxygen.
Quantity of .N'/IO alkali required
to neutralise the acid from
100 g. of vaseline.
Natural vaseline .
Artificial vaseline
Hog's lard ....
35-0 to 46-5 c.c.
4-2 „ 4-7 „
42-0 „ 50-0 „
5-5 to 10-5 mg. KOH
0-7 „ 1-4
31-0 ., 39-0
E. SOLID LUBRICANTS.
The substances included under this head vary widely in their nature
and composition. General methods of examination, therefore, cannot
well be laid down, and it is necessary to modify the laboratory tests
according to the nature of the products concerned. Some data as to
the composition of solid lubricants have been given above (p. 59).
Some varieties melt at 6o'-65^ whilst others do not become liquid until
temperatures well over 100" are reached.
The following are the main features to be taken into account with
regard to solid lubricants: —
I. Appearance^ etc.
I I. Liquefying and Dropping points.
III. Qualitative Composition.
IV. Quantitative determination of: —
{a) Free Fatty Acid, {h) Soap, {c) Neutral Fats (glycerides)
and unsaponifiable matter (Mineral Oil, Rosin Oil, Wool
Grease, etc.). {d) Water, {e) Glycerol. (/) Nitrobenzene
and Nitronaphthalene. (g) Free Lime. (//) Impurities
and adulterants.
' C/. Engler and Bohm, Dingl. polyl. J., l8S6, 262, 468.
SOLID LUBRICANTS
99
L Appearance, etc.
A good deal of information as to quality may be gained by inspection.
Properly compounded greases should be quite uniform with respect to
colour and consistency. Additions of rosin oil, tar oil,
nitrobenzene, etc., may be detected by the smell.
ir> - o
o
o
IL Liquefying and Dropping Points.
The temperature at which lubricating greases become
fluid ranks as one of the most important criteria in their
commercial valuation.
These greases do not possess a definite melting point.
When warmed, they at first gradually soften at the sur-
face ; when further heated, the soap may remain sus-
pended in the molten fatty matter, and complete melting
may only occur when a portion of the moisture has been
lost by evaporation.
The most serviceable method for the determination
of the liquefying and _ dropping points is that of L.
Ubbelohde, in which the temperature is ascertained at
which a drop of the sample detaches itself by its own
weight from the uniformly heated mass.^
The apparatus (Fig. 32) consists essentially of a ther-
mometer a, to which is closely fitted a metal cylinder b,
and a small glass receptacle ^, 10 mm. long, and having
an opening of 3 mm. bore. The metal cylinder has a
small opening at c, and grips both the thermometer and
the receptacle firmly.
To carry out the test the substance under examination
is pressed into the receptacle, and the excess struck off
neatly with a knife ; the receptacle is then fitted to the
thermometer, as shown. In the case of paraffin wax and
ceresin, the substance is first melted (with a glass plate
held under the receptacle) and the thermometer inserted
before it has solidified. Three small guides d prevent ^-
the thermometer from being pushed down too far. The
thermometer is fixed by means of a cork in a test tube
of 4 cm. bore, which is placed in a water-bath (a 3 litre
beaker filled with water) and heated slowly so that the
temperature rise per minute does not exceed 1°.
The temperature at which a drop of the melted lubricant begins to
make its appearance is noted as the " Liquefying point," and that at
1 Z. angew. C/iein., 1905, 18, 1220 ; /. Soc. Cliem. Ind„ 1905, 24, 941. The apparatus
is supplied by Messrs Bleckmann and Burger, Berlin.
O
fiP-
<S
o
o
^CL
W-
^a
FlQ. 32.
100 LUBRICANTS
which the first drop falls as the " Dropping point," The latter point is,
as a rule, from 3^-6 above the liquefying point, although in some cases
the difference may amount to 15 and even more.
III. Qualitative Examination.
If the lubricant should be completely soluble in petroleum spirit
or ether, and leave no ash on incineration, it is only necessary to test
for rosin and possibly for ceresin, as described on pp. 84 and 187.
The presence of water is indicated by the spurting that occurs on
incineration.
The examination of the fatty matter is carried out by the methods
described in the following Section (pp. 1 14 r/ seq).
As the majority of lubricating greases contain soap, and are therefore
only partially soluble in petroleum spirit, the sample is treated with
a hot mixture of 9 vols, of petroleum spirit, and i vol. of absolute
alcohol and, after standing for a short time, filtered whilst still warm.
Any insoluble residue (lime, calcium carbonate, barytes, infusorial
earth, graphite, etc.) remains on the filter and is examined by the
ordinary methods of inorganic analysis.
IV. Quantitative Determinations.
(a) Free Acid. — Free mineral acid, if present, is detected and
estimated by titrating a hot-water extract of the grease. Free fatty*
acids are determined by the method described in the following Section
(p. 130).
(6) Soap. — For this estimation 10 g. of the sample are dissolved in
petroleum spirit, decomposed with hot, dilute hydrochloric acid, and the
acid layer of liquid separated. This layer is sometimes coloured red
owing to the presence of colouring matters that have been added to the
lubricant ; in such cases the extraction with hydrochloric acid is
repeated until a final colourless extract is obtained. If the sample is
not coloured, two successive extractions are sufficient. After the
separation of the acid, the residual petroleum spirit is washed either
with water or with a solution of sodium sulphate (to avoid the
formation of an emulsion), and titrated, after the addition of 20
c.c. of absolute alcohol, phenolphthalein being employed as the
indicator.
The acid value obtained represents the sum of the free fatty acids
present (ascertained as in {a), above) and of the fatty acids formed by
the decomposition of the contained soap; the difference represents the
fatty acids present as soap. This value may be calculated cither to
sodium or to calcium soap, as the case may be. It is sufficiently
SOLID LUBRICANTS. QUANTITATIVE TESTS 101
accurate to take 280 as the mean molecular weight of the fatty acids ;
should there be reason to assume the presence of rape oil, the mean
molecular weight 310 may be adopted.
(c) Neutral Fats (Glycerides) and Unsaponifiable Matter — The
petroleum spirit solution obtained under {b) is freed from fatty
acids in the usual manner by extraction with 50 per cent, alcohol,
distilled to dryness, and the residue, consisting of neutral fats and
hydrocarbons, is weighed. The proportion of glycerides in it is
determined by estimating its saponification value (p. 1 14) and calculating
to percentage of the original material.
If the nature of the unsaponifiable matter is to be examined, this
constituent is separated from the soap as described above.
(cf) Water. — For most purposes it is sufficiently accurate to mix a
weighed quantity of the grease with dried sand, and dry in a water
oven.
A more lengthy but more accurate method is that proposed by
J. Marcusson, which is carried out as follows : — 100 g. of the sample are
dissolved in 100 c.c, of xylene in a 600 c.c. Erlenmeyer flask, some
fragments of pumice added, and the solution distilled from an oil-
bath through a Liebig's condenser. Unless very little water is present,
distillation begins below 100°. The distillate is collected in a 100 c.c.
measuring cylinder, in which the separation into layers of water and
xylene rapidly takes place. Distillation is continued until pure
xylene comes over ; any drops of water which adhere to the con-
denser are rinsed down with xylene. The amount of water driven
over is read off directly and calculated to percentages of the original
substance.
(e) Glycerol. — The small quantities of glycerol (from. 0-5-2 per
cent.) occurring in lubricating greases are derived from the saponifica-
tion of the fatty constituents. The determination of glycerol is carried
out only in exceptional cases ; the method described in the following
Section is then employed (p. 123).
(/) Nitronaphthalene and Nitrobenzene. — The method for the
estimation of these substances has been described above (p. 94).
{g) Free Lime is determined by heating 10 g. of the sample
with 50 c.c. of benzene and 5 c.c. of alcohol for a quarter of an hour
under a reflux condenser. The residue is filtered off, thoroughly
washed with a hot mixture of benzene and alcohol in the above
proportions, and the contained free lime determined by the usual
methods.
(/i) Impurities and Adulterants. — Plaster of Paris, barytes, starch,
talc, graphite, lampblack, and the like remain undissolved when the
sample is extracted with the mixture of benzene and alcohol as
described under {g), and are determined in the residue thus obtained.
102 LUBRICANTS
F. WATER-SOLUBLE LUBRICANTS.
Water-soluble lubricants have the property of forming permanent
emulsions or almost clear solutions with water. Latterly they have
become important articles of commerce, and are prepared by dissolving
ammonia-, potash-, or soda-soaps of oleic, sulpho-fatty, rosin, or naph-
thenic acids in mineral oils. Frequently ammoniacal liquor, petroleum
naphtha, or alcohol is added ; in some cases the rosin oils are first blown
with air. The resulting water-soluble products may be regarded as
(colloidal) solutions of mineral oil in an acid soap solution Such
preparations are largely employed as lubricants in boring, milling,
lathe-cutting, and polishing operations. They have the advantage
over aqueous solutions of soap that iron-work with which they come
in contact does not rust so easily ; other applications are dressing
wool-fibre in spinning and weaving, for laying dust in streets, and
so on.
The Solidifying" Point of such oils is, of course, lowered by the
addition of water. Thus a mixture of 80 parts of water with 20
parts of oil is still liquid at —5'; for this reason water-soluble oils
are often used in place of glycerine in hydraulic presses and pressure
mains.
The Emulsifying Properties or Solubility in Water is determined
by preparing solutions of varying concentration, and observing the
permanence of the emulsion after standing for one or more da}-s. In
the case of oils containing ammonia-soaps, the soaps gradually lose
ammonia, and the emulsifying properties then fall. Such oils must
therefore be tested (and kept) in well-closed receptacles.
Analytical Examination.
This comprises the following determinations : —
(a) Volatile Matter (Water, Alcohol, Naphtha).— The content of
water is determined by distilling about 20 g. of the oil in a i -litre
Erlenmeyer flask, with the addition of 100 c.c. of xylene and small
pieces of pumice (r/!, The determination of water in petroleum in the
section on " Mineral Oils," this Vol., p. 5).
The aqueous distillate is fractionated and tested for alcohol, either
by the specific gravity of the distillate, or, if necessary, by the iodoform
test. To determine the petroleum naphtha, the oil is decomposed by
dilute sulphuric acid, and the volume of naphtha either measured
directly or after being distilled over by steam.
If both alccjhol and naphtha are present, the oil is distilled with acid
potassium sulphate, and the distillate shaken with sodium hydroxide,
whereby the alcohol is completely separated. The volume of naphtha
WATER-SOLUBLE LUBRICANTS 103
is then measured, and the alcohol separated from the alkaline liquid by
a further distillation, and determined as above.
(b) Free Organic Acid. — In the absence of ammonia the sample is
titrated with iV/io alcoholic sodium hydroxide.
In the presence of ammonia-soaps, it is necessary to determine the
ammonia by distilling 20-30 g. of the sample with an excess of concen-
trated sodium hydroxide solution from a very capacious conical flask
fitted with a vapour-trap; the distillate is collected in Ay 10 sulphuric
acid, and the excess titrated back with standard alkali.
Should ammonia be the only base present, it may be determined by
simply titrating an aqueous emulsion of the material with N/2 hydro-
chloric acid, using methyl orange as the indicator. The amount of acid
corresponding to ammonia, found by either method, is calculated to
" acid value," and is subtracted from the total acid value obtained by
direct titration ; the difference represents free acid.
(c) Neutral Fatty Matter. — The sample is shaken up with petroleum
spirit and N/io alcoholic sodium hydroxide (50 per cent, alcohol), and
the neutral fat isolated as described above (p. 89).
(d) Soap. — I. When, the soap acids present are ordinary fatty or
naphthenic acids, sulphonated fatty acids or oxidised resin acids being
absent, the soap content of the material can be determined as in
ordinary lubricants (p. 88). Ammonia, if present, beside fixed alkali,
must be determined and allowed for.
2. Sulphonated acids or oxidised resin acids introduce complications,
as they combine with considerably more alkali than ordinary fatty acids.
Thus sulphonated fatty acids require one equivalent of alkali for the
carboxyl group and a second one for the sulphonic acid group. In such
cases the organic acid present in the form of soap is determined as
above, and in addition the total alkali absorbed is determined gravi-
metrically by incineration. The carbonate found by incineration is
calculated to metal and added to the soap acid, whereby the amount of
soap as such is arrived at.
Exaviple : —
Free acid found = 10 (" Acid Value " ).
Weight of total acid, as under c = 15 g. (corresponding to " acid
value" 30).
Hence, weight of free acid = — = 5 g- ^i^d
weight of soap acid = 10 g.
Alkali found as ash, calculated to metal, =2 g.
Hence weight of soap present approximately = 10-^2= 12 g.
Whether soap alkali is to be determined by titration (i) or by
incineration (2) is decided by a preliminary qualitative test of the
isolated organic acids,
104 LUBRICANTS
Literature.
Archbutt L. and Deely, R. M. — Lubrication and Lubricants, 3rd edition, 1912.
Grossmann, J. — Die Schmiennittel, Methoden zu Hirer Untersuchung und Wert-
bcstimmung, 1909.
HOLDE, D. — Untersuchung der Mineralole und Fette, 1909.
Hurst, G. H. — Lubricating Oils, Fats, and Greases, 3rd edition, revised by H.
Leask, 191 1.
Lewkowitsch, J. — Chemical Technology and Analysis of Oils, Fats, and Waxes,
vol. iii., 4th edition, 1909.
Redwood, I. I. — Lubricants, Oils, and Greases, 1898.
OILS, FATS, AND WAXES
By the late J. Lewkowitsch, M.A., Ph.D. English translation
revised by the Author.
CLASSIFICATION OF OILS, FATS, AND WAXES.
The oils, fats, and waxes which form the raw material of the fat and
oil industries are found ready formed in plants and animals. The oils
and fats differ chemically from the waxes, in that the former are glyceryl
esters of fatty acids, whereas the latter are esters derived from fatty
acids and monohydric alcohols. On this basis it is easy to distinguish
between oils and fats, on the one hand, and waxes, on the other hand, by
chemical means ; namely, by the detection of glycerol. In nature
apparently only triglycerides occur ; mono- and diglycerides are the
result of a secondary reaction which may be regarded as a natural
hydrolysis. The present section deals only with the triglycerides.
The natural oils and fats represent complicated mixtures of the most
varied triglycerides, including not only simple triglycerides containing
a single fatty acid, but also mixed triglycerides in which the glyceryl
radicle is combined with different fatty acids ; hence an exhaustive
scheme of analysis similar to the systems of inorganic analysis is
impracticable. There is, however, no necessity for such a scheme, as
it is generally possible to indentify a given oil, fat, or wax on the basis
of a systematic method of examination, and in addition to determine
whether a sample is pure or adulterated ; these are the most important
problems in their technical analysis.
It is also possible, with the help of the methods described below, to
identify a mixture of two or more oils or fats, and to obtain an approxi-
mate indication as to their relative proportions. The larger the
number of components in a mixture, the more difficult their detection
and estimation will naturally be. If, however, the tests are applied on
a strictly logical basis, and the methods described are combined in
a suitable manner, it is frequently possible to ascertain, with sufficient
accuracy for technical purposes, the composition of mixtures which
appear at first to be hopelessly complicated.
As glycerol is obtained as a product of saponification from all oils
and fats, the differentiation of the glycerides must necessarily depend
upon the differences of the several fatty acids occurring in the natural
105
lOG OILS, FATS, AND WAXES
oils and fats, disregarding for the present the more intricate and
hitherto scarcely investigated differences depending upon the isomerism
of the mixed glycerides. Hence it follows that in addition to the
examination of the oils and fats themselves, an investigation of the
fatty acids is of great importance.
In tlie case of the waxes, whose alcoholic constituents, in contra-
distinction to glycerol, are insoluble in water, the examination of the
alcohols is of increased importance. The alcoholic compound is spoken of
in technical practice as " unsaponifiable matter," although this expression,
in contrast to saponifiable matter, includes not onl)- the alcohols, but
also (unsaponifiable) hydrocarbons, such as, mineral oils, rosin oils, tar
oils, etc. Strictly speaking, only the fatty acids themselves are
saponifiable, that is, capable of conversion into soaps. As, however,
glycerol, in itself unsaponifiable, is soluble in water, in contradistinction
to the alcohols of the waxes and to the hydrocarbons, the glycerides
are technically considered as completely saponifiable.
A systematic investigation would therefore comprise the examination
of the oils, fats, and waxes of the fatty acids, and of the unsaponifiable
matter.
THE EXAMINATION OF OILS, FATS, AND WAXES.
Both physical and chemical methods are employed in the examina-
tion of natural oils and fats.
A. — Physical Methods.
Preliminary indications are obtained from the colour, consistency, and
also from the smell and taste. The colour is chiefly of importance for
the recognition of certain individual substances amongst the solid fats,
e^., raw palm oil and aouara oil. The consistency at ordinary tempera-
ture helps to give a ready indication as to whether a sample belongs to
the class of liquid fats (oils) or of solid fats. Smell and taste characterise
the oils derived from marine animals. In the case of other commercial
oils and fats these " organoliptic " indications can only be made use of
by experts, for they require an extensive experience which is not at
the disposal of every technical chemist, the acquirement of which is,
however, very desirable. In the examination of oils and fats which
form articles of food, both the smell and taste are of very great
importance.
The determination of the specific gravity, melting point, solidifying
point (especially of fatty acids), and of the refractive index is of
primary importance. The viscosity, the optical rotation, and the
solubility are frequently determined as subsidiary tests.
PHYSICAL METHODS OF EXAMINATION
107
I. DETERMINATION OF THE SPECIFIC GRAVITY.
The specific gravity of liquid oils and waxes is determined by the
hydrometer, pyknometer, or the hydrostatic balance. It is advisable
to make the determinations at the normal temperature of 15° C. (or, as
is usual in England and America, at 15"- 5 C, corresponding to 60° F.),
as most of the observations recorded in the literature have been made
at this temperature, and can therefore be used for purposes of com-
parison. However, if it is impossible to make the determination at this
temperature, a correction of ±0-00064 per degree is applied. The
determination is often made at higher temperatures. In such cases,
Sprengel's pyknometer (Fig. 33) is used. The Sprengel tube is filled
with the fat by dipping the tube b into the oil
and sucking it up with the aid of a rubber tube
attached to a. The tube is then suspended as
deeply as possible in a beaker of water, which is
heated to boiling. The oil expands in the Sprengel
tube in the direction of least resistance towards a^
so that the side tube a -always remains full. If
the meniscus of the liquid lies beyond ;;/, the
excess is removed at a by a small roll of filter
paper. If, on the other hand, there is too little
oil in the tube, a drop of the oil is brought in
contact with <7 on a glass rod, and is drawn into
the tube by capillarity. The specific gravity of
the substance is compared with that of water at
the same temperature as found by determining
the specific gravity of water under identical con-
ditions. The temperature of the water in the
control test must always be stated.
The specific gravity of solid fats is usually determined at 100°, in
the same manner as described above. In the case of beeswax, however,
the test is generally carried out as follows : — The wax is first melted
on a watch-glass on the water-bath and allowed to solidify gradually.
Small pieces are then cut out of the mass, brushed with a damp brush
to remove air bubbles, and carefully introduced into dilute alcohol with
the aid of a pair of forceps. Water or alcohol, as the case may be, is
then added until the wax neither floats nor sinks, but remains suspended
in the liquid. The alcohol is filtered off, and its specific gravity
determined ; the value obtained is, of course, identical with the specific
gravity of the wax.
As a rule the determination of the specific gravity gives but little
information as to the nature of a given sample. It furnishes, however,
indications in the case of the liquid waxes, which are characterised by a
Fio. 33.
108 OILS, FATS, AND WAXES
low specific gravity, as also in the case of castor oil, the specific gravity
of which is high. The specific gravity also frequently helps to indicate
adulteration, or serves as a confirmation of conclusions drawn from the
other methods detailed below. A list of the specific gravities of
the commoner oils, fats, and waxes is given below (see Tables, pp. 146
et seq.).
II. DETERMINATION OF THE MELTING POINT AND THE
SOLIDIFYING POINT.
The fats and waxes have no sharply defined melting points, such as
pure chemical substances exhibit when tested in capillary tubes. If
this method be applied to fats, the melting point extends over several
degrees, the substance first softening, then melting at the edges
and becoming translucent, and finally melting to a clear liquid. Hence
there is considerable uncertainty as to what temperature should be
accepted as the melting point. Some chemists define the melting point
as that temperature at which the fat softens so that it is driven up
the tube by the hydrostatic pressure of the water, when immersed in
water in a small tube open at both ends. Others, again, dip the bulb of
a mercury thermometer into the molten fat, allow it to solidify, and
take that temperature at which the fat softens sufficiently to drop off the
bulb as the melting point. As several different methods are still in
technical use, it is absolutely essential to state precisely in every
instance the procedure by which the melting point has been
determined.
Further, it is to be noted that a freshly melted sample does not show
the correct melting point, and that it is necessary to allow such
a sample to remain at rest for twenty-four hours before determining
the melting point.
The following methods are still in commercial use in tendering for
supplies of fats : —
Pohl's method, which consists in dipping the bulb of a thermometer
into the molten substance so that a thin layer remains on the glass. The
thermometer is then allowed to stand for one to two days in a wide test
tube, which is corked so that the bulb of the thermometer is at a distance
of 1-25 cm. from the bottom. The test tube is then heated in
a water-bath, and the temperature at which the fat collects as a drop at
the bottom of the bulb is taken as the melting point.^ L. Ubbelohde has
increased the accuracy of the method by the introduction of a special
thermometer (see " Lubricants," Fig. 32, p. 99), to the bottom of which
a small glass vessel containing a hole is attached. The temperature at
which the fat softens may be recognised by the formation of a drop,
and the melting point is taken as the temperature at which it drops off.
' Cf. R. Mcldrum, C/iem. Xncs, 1913, 108, 199, 233.
THE REFRACTIVE INDEX 109
Hitherto this method has not met with general acceptance, at any rate
in this country, and the somewhat high cost of the apparatus forms a
drawback to its introduction.
A better method is that introduced by Boverton Redwood, which
gives good results with sufficiently solid fats, when applied in the
following manner : — A lump of the fat, not recently melted, is brought on
to a bright surface of mercury, and slowly warmed in a dish over
a beaker. The temperature at which the fat spreads over the mercury
is taken as the melting point.
The determination of the melting point is still frequently made
in a capillary tube. As the fat passes through successive phases
of softening, translucency, and finally of melting, it is usual to state the
initial and final point of the melting.
The determination of the melting point is only of importance in the
case of " winter oils " and chocolate fats.
The solidifying point of the fatty acids, or, as it is technically called,
the "titre," is of far greater importance. For this purpose the fatty
acids must first be isolated by the method described in the following
Section (p. 174).
III. DETERMINATION OF THE REFRACTIVE INDEX.
The determination of the refractive index, which has been
very considerably simplified by the introduction of the oleo-refractometer
of Amagat and Jean, and especially by the construction of Zeiss' butyro-
refractometer, forms one of the simplest and most important preliminary
tests for oils and fats, especially of butter fat and of lard. Formerly
unjustified objections were raised by various workers against the
reliability of the refractometric method ; ;more recently, however, on
account of the ease and rapidity of measurement by the butyro-
refractometer, this mistrust has given place to undue optimism,
as is evidenced by many recent publications, so that a warning in
this connection is necessary. In the testing of butter fat especially,
conclusions have been drawn which are unsubstantiated. With
the help of the butyro-refractometer it is possible to tell at a
glance whether a butter fat has been grossly adulterated ; but when
the readings differ but slightly from the " normal " value, or even when
" normal figures " are obtained, this is no proof of the purity of a butter
fat, for it is an easy matter to prepare mixtures of margarine and cocoa-
nut oil, which give the same refractive index as does normal butter fat.
Even when abnormal values are obtained, this does not afford certain
proof of adulteration, for there are certain kinds of butter which give
refractometric figures deviating considerably from the normal ones.
The refractometric test must, therefore, be considered only as a
110
OILS, FATS, AND WAXES
preliminary test, although one of great importance. It would be quite
unjustifiable to attempt to identify oils and fats by this method alone.
As a rule, there e.vists a certain correlation between the refractive
index and the iodine value, as may be gathered from the Tables given
on pp. 146 ct see]., in which the refractive indices of the most important
oils and fats arc collated.
The Butyro-Refractometer.
The essential parts of this instrument (Fig. 34) are two glass prisms
Fio. S4.
contained in the two metal cases A and B. One face of each of
the prisms is exposed. The case B can be rotated on the axis C, so
that the two exposed faces of the prisms can be brought into contact
and removed from one another. The two metal cases are hollow ;
if warm water is allowed to flow through them, the glass prisms are
heated. A metal jacket which holds a thermometer M is attached to the
inner case, the mercury bulb reaching into the case. K is a telescope
THE BUTYRO-REFRACTOMETER
111
containing a scale divided from i-ioo, and J a mirror for illuminating
the prisms and scale.
The heating arrangement shown in Fig. 35 is used to warm
the water. The boiler, heated by the gas burner B^ is fitted with
a thermometer T^ and a thermo-regulator S^. The neck A^ is connected
by a glass and rubber tube with a vessel C^, placed above the heater
and charged with cold water ; the rubber tube carries a screw clip E^.
Before heating the boiler, water is allowed to flow into it by opening
the clip Ep The clip is then closed, and the rubber tube G^ is connected
to the gas supply and the flame lit at B^. By turning the screw Pj^, the
flow of gas to the burner Bj is regulated once
for all, so that a constant temperature of the
water in the boiler is maintained.
Directions for fitting up the Refractometer
in connection with the Heating Apparatus. —
The instrument is placed in a convenient posi-
tion, and is illuminated either by daylight or by
lamplight.
The rubber tube attached to the prism jacket
of the refractometer (Fig: 34) is connected to
the nozzle D^ of the heating bath ; at the same
time a rubber tube is attached to the outlet of
the metal jacket of the refractometer and is led
to an empty vessel placed at a lower level, or to
a sink. The screw clip E^ is then opened, and
water is allowed to flow from the vessel C^
(F^ig- 35) into the heating bath. This causes
warm water to flow through the outlet tube of
the bath and so through the rubber tube D
into the prism jacket B, thence through the
rubber tube shown in Fig. 34 into the other
prism jacket, through the metal jacket of the
thermometer, and so through the outlet and rubber tube. The two
glass prisms and the bulb of the thermometer are thus heated by the
warm water.
The flow of water through the heater is regulated by the screw clip,
so that the water trickles out in a slow stream, and the thermometer
indicates the desired temperature (as a rule, 40°).
Application of the Oil or Fat to the surface of the Prism, and
Reading of the Refractometer Value. — The prism jacket of the
refractometer is opened by turning the milled head F (Fig. 34) about
half a revolution to the right until it releases the catch, whereupon one
half of the jacket may be turned round the other. The support H
holds B in the position shown in Fig. 34. The instrument is moved by
Fig. 35.
112
OILS, FATS, AND WAXES
the left hand into such a position that the exposed surface of the prism
B is approximately horizontal, and three drops of the filtered oil (or
molten fat) are applied to the surface with the aid of a small glass rod,
and spread with the rod, so that the whole surface is covered. The
prism jacket is then closed by bringing B and A together, and turning
the milled head to the left into its original position. The mirror is then
brought into such a position that the border line between the bright
and the dark portions of the field is seen distinctly. The upper part of
the telescope, which can be drawn out, is focussed so that the scale
appears quite distinct.
Three minutes are allowed to elapse before reading off the scale
division at which the border line between the bright and dark portions
of the field lies ; fractions of the marked divisions are estimated by
the eye. The thermometer is read immediately after taking the
reading.
The refractometer reading.s, if not taken at 40 , must be corrected to
this temperature by adding 0-55 division to the reading for every degree
of temperature above 40 ; conversely, for every degree below 40', 0-55
division must be subtracted.
Cleaning of the Refractometer.— After every experiment, the
surfaces of the prisms and their metal fittings must be carefully cleaned
with soft linen or soft filter paper, moistened with ether.
Testing the Adjustment of the Refractometer Scale. — The
refractometer itself should be tested from time to time with the normal
liquid supplied with the apparatus.
For this purpose the thermometer is fitted into position, water at
the ordinary temperature allowed to flow through the prism jacket (no
heating being necessary in this case), and the refractometer number of
the normal liquid determined, the thermometer reading being taken at
the same time. If the scale is correctly adjusted, the following refracto-
meter numbers should be obtained at different temperatures : —
Temperature.
Divisions on scale.
Temperature.
Divisions on scale.
25° C.
71-2
16° C.
76-7
24°
71-8
15°
77-3
23°
72-4
14°
77-9
22°
73-0
13°
78-6
21°
73-6
12°
79-2
20°
74-3
11°
79-8
19°
74-9
10"
80-4
18°
75-5
9°
81-0
17°
76-1
8°
81-6
If necessary, the scale must be adjusted with the key supplied with
the instrument.
VISCOSITY. OPTICAL ROTATION
113
The divisions of the scale correspond to the following refractive
indices : —
Divisions on scale.
Refractive index.
Dift'erence.
0
1-4220
0-0080
10
1-4300
0-0077
20
1-4377
0-0075
30
1-4452
0-0072
40
1-4524
0-0069
50
1-4593
0-0066
60
1-4659
0-0064
70
1-4723
0-0060
80
1-4783
0-0057
90
1-4840
0-0055
100
1-4895
Intermediate values are easily obtained by interpolation.
The refractometers of the newest construction are provided with a
micrometer screw, which permits of a more accurate estimation of the
tenths of a degree.
IV. THE DETERMINATION OF THE VISCOSITY.
This is determined in one of the known forms of viscometer, the
Redwood's viscometer being in general use in England, that of
Saybolt in the United States, and that of Engler in Germany. These
apparatus and the method of testing are fully described in the section
on " Lubricants," pp. 66 and 68. This test is of importance only for
oils which are used for lubricating purposes, e.g., rape oil and blown oils.
V. DETERMINATION OF THE SOLUBILITY.
This test is of secondary importance, as almost all fats are readily
soluble in the common solvents. Castor oil alone forms an exception,
being readily soluble in alcohol and sparingly so in petroleum hydro-
carbons. This abnormal behaviour may be used to identify castor oil,
and to distinguish it from other oils.
VI. OPTICAL ROTATION.
This has up to recently been seldom used in technical analysis, and
was chiefly applied for the detection of rosin oils in fatty oils. Recently,
however, this test has gained in importance, since the oils of the
chaulmoogra group can be identified with the aid of the polariscope.
In this manner the poisonous "Cardamom oil" (which the author first
identified as chaulmoogra oil) can be recognised in margarines.
Ill H
114 OIL, FATS, AND WAXES
B. — Chemical Methods.
The chief chemical methods which are used in technical anal}'sis
consist in the determination of certain values depending upon the
nature of the fatty acids contained in the oils, fats, and waxes. As
these figures are a measure of the quantity of different fatty acids or
groups of fatty acids present, without, however, showing their absolute
quantit)', these methods are appropriately termed "quantitative
reactions."
Besides these quantitative reactions, a number of other tests are
available which may conveniently be grouped together as "qualitative
methods."
I. QUANTITATIVE METHODS.
The values which are obtained by quantitative methods may be
divided into two classes.^
(a) Characteristics, that is, numbers which determine the nature of
an oil, fat, or wax, and may therefore serve for the identification of a
given specimen.
(b) Variables, that is, numbers which serve to determine the quality
of a product, as these numbers depend upon the method of purification
of the raw product, the age, rancidity, and other features.
The acetyl value takes up an intermediate position, as it may
sometimes be regarded as a characteristic and sometimes as a
variable.
(a) Characteristics.
The following characteristics, which are given in the order of their
relative importance, will be considered : —
1. Saponification Value.
2. Iodine Value.
3. Reichert (Reichert-Meissl, or Reichert-VVollny) Value.
I. Determination of the Saponification Value.
The saponification value (Kottstorfer Value) indicates the number
of milligrams of potassium hydroxide required for the saponification of
I g. of a fat or wax.
The saponification value is determined as follows: — 1-5-2-0 g, of the
filtered fat or wax are weighed into a 150-200 c.c. flask (of good glass),
and 25 c.c. of an approximately A^J2 alcoholic solution of potassium
hydroxide are added. The alkali is best measured out from a pipette,
' The expression "constant" origin.illy used in tlie older editions of Lewkowitsch's Chemical
Technology and Analysts of Oils, Fats, and Waxes, may be advantageously replaced by "character-
istics," as the former expression has been taken by many chemists in far too literal a sense.
SAPONIFICATION VALUE 115
which is always allowed to run out in exactly the same manner — both
in the experiment proper and in the control test. The flask is attached
to a reflux condenser or a simple glass tube and heated either on a water-
bath, or over a small flame, so that the alcohol simmers gently. The
flask is agitated from time to time, as long as any oil layer is visible
at the bottom. After half an hour the saponification is almost invariably
complete; only in the case of waxes {cf. p. 184) is it necessary to use
strong alcohol and to boil briskly for at least an hour over a free
flame. (The stronger the alcohol used for the preparation of the
alcoholic potash, the more quickly the saponification proceeds. It is
inadvisable to use alcohol of less than 96 per cent, strength.) i c.c. of
a I per cent, alcoholic solution of phenolphthalein is then added, and
the excess of alkali is titrated back with N\2 hydrochloric acid.
A blank test is conducted in exactly the same way with 25 c.c. of
the alcoholic potassium hydroxide solution. The difference of the
amounts of acid used in the two experiments corresponds to the
potassium hydroxide that has combined with the fatty acids.
Example. — 1-6775 g. of lard were saponified with 25 cc. of an
alcoholic potash solution, which corresponded to 24-6 c.c. of 7V/2 hydro-
chloric acid (i c.c.-=o-o5t5i g. KOH). For the back-titration 12-95 c.c.
of A72 hydrochloric acid were required. Hence, the amount of alkali
used in combining with the fatty acids is 24-60- 1 2-95 = 1 1-65 c.c.
This corresponds to U:^!^':^^^ = 32678 mg. KOH.
Hence i g. of fat requires ^^ryr = 194-8 mg. KOH.
The saponification value is therefore 194-8.
The "cold saponification" suggested by R. Henriques ^ has no
advantage over the above method, except in testing india rubber
substitutes.
The saponification values of most oils and fats lie in the neighbour-
hood of 195, and the mean molecular weight of their fatty acids
{cf. p. 131) is therefore approximately 276. The oils of the rape oil
group are, however, distinguished by a lower saponification value,
namely, about 175, as these oils contain considerable quantities of
erucic acid of molecular weight 338. On the other hand, oils and fats
containing considerable quantities of volatile fatty acids have a higher
saponification value than 195. Thus, the saponification value of butter
fat is 227. Fats containing much myristin or laurin have still higher
numbers ; thus the saponification values of the fats of the cocoa-nut oil
rise as high as 240-260.
The saponification values of the waxes are far lower than those of
1 Z. angew. Chem., 1895, 7, 721 ; 1S96, 8, 221 ; /. Soc. C/iein. hid., 1896, 15, 299, 476.
116 OILS, FATS, AND WAXES
the oils and fats, and are for the most part between 80 and 136. It is
therefore possible to distinguish between the waxes (liquid and solid),
the oils of the rape oil group, butter fat, and the oils of the cocoa-nut
oil group by the determination of the saponification value alone. This
holds, of course, only on the assumption that the samples under
examination contain only negligible amounts of unsaponifiable oils,
as the latter obviously reduce the saponification value.
The influence of free fatty acids in a fat on the saponification value
has been investigated by the author.^
2. Determination of the Iodine Value,
The iodine value indicates the amount of iodine chloride, expressed
in per cent of iodine, which the fat or wax is capable of absorbing.
The iodine value is a measure of the unsaturated fatty acids, as these
acids, both in the free state and also when combined with glycerol,
absorb one molecule of iodine chloride, corresponding to two atoms of
iodine, for each pair of doubly linked carbon atoms.
The determination of the iodine value was introduced into fat
analysis by A. von Hubl,and is carried out, either in the form originally
proposed by him, or as modified by J. Wijs, On the basis of many
years' experience, the latter is to be recommended as the more rapid
and reliable method. As, however, the Wijs method has not yet met
with the general acceptance which it undoubtedly deserves, both
methods will be described.
Hiibl's Method. — The quantities of oil or fat taken for the test are
as follows: — Drying oils and fish oils, o-i5-o-i8 g. ; semi-drying oils,
0-2-0-3 g. ; non-drying oils, 0-3-0-4 g. ; solid fats, o- 8-1 -o g. The oil is
best weighed in a small weighing bottle, the cork of which is fitted with
a small pipette, so that a certain number of drops of the oil or molten
fat can be withdrawn with the help of a rubber tube fixed to the
pipette. With a little practice the weight can be estimated to within
a few centigrams by the number of drops. The weighed quantity is
introduced into a well-stoppered flask of 500-800 c.c. capacity, 10 c.c.
of carbon tetrachloride (or chloroform) added, and the substance is
brought into solution, if necessary, by gentle warming ; 25 c.c. of an
iodine chloride solution are then introduced by means of a pipette, this
solution being prepared as follows : — Two solutions are made up, one
of 25 g. of pure iodine in 500 c.c. of 95 per cent, alcohol ; and the other
of 30 g. of mercuric chloride in the same quantity of alcohol ; these
solutions arc kept separate. The quantit)' necessary for an experiment
is made up twenty-four hours before use by mixing equal volumes of the
two solutions. The mixture must not be used at once, as the iodine
chloride solution alters its titre rapidly immediately after its prepara-
' Chemical Technology and Analysis of Oils ^ Fats, and Waxes, vol. i., p. 385.
IODINE VALUE 117
tion ; the titre alters gradually even after twenty-four hours' standing,
but remains sufficiently constant during the experiment.
In order to avoid any loss of iodine by evaporation, it is advisable
to moisten the glass stopper of the flask with a concentrated solution of
potassium iodide. A clear solution should be obtained on gently
agitating the flask ; if it is not clear, more carbon tetrachloride (or
chloroform) must be added. The flask is then allowed to stand,
protected from the light. At the same time a blank experiment is
made, in which exactly the same quantity of carbon tetrachloride (or
chloroform) and iodine chloride are brought together ; this solution
serves to determine the titre. After about two hours the solution must
still have a deep brown colour, otherwise the quantity of iodine is
insufficient, and a further quantity of 25 c.c. of the iodine chloride
solution must be added. The absorption of the bulk of the iodine
chloride takes place during the first two hours ; after this time it
becomes more sluggish. It must not, however, be considered as com-
plete before about six to eight hours in the case of solid fats and non-
drying oils, or twelve to eighteen hours in the case of drying oils and
fish oils. For semi-drying oils eight to ten hours suffice.
After the necessary time has elapsed, 20 c.c. of a 10 per cent,
solution of potassium iodide are added, and, after shaking, 400 c.c. of
water. If a red precipitate of mercuric iodide separates, more potassium
iodide solution must be added. The excess of free iodine is then
titrated back by the addition of Nj 10 sodium thiosulphate, the titre of
which has been accurately determined with potassium bichromate.
The contents of the flask are gently rotated during the titration, so that
the free iodine which is dissolved in the carbon tetrachloride (or chloro-
form) may pass into the aqueous solution. When the colour, which was
originally deep brown, has become pale, a few drops of starch solution
are added and the titration completed. Tlie iodine in the blank test is
determined in exactly the same manner. The difference between the
two results corresponds to the quantity of iodine chloride absorbed, and
is calculated to per cent, of iodine.
The potassium bichromate solution used for fixing the strength
of the thiosulphate solution is made up by dissolving 3-8657 g. of
bichromate in 1000 c.c. of water; i c.c. of this solution is =o-oi g. I.
10 c.c. of a 10 per cent, potassium iodide solution are placed in a
stoppered bottle, 5 c.c. of hydrochloric acid added, 20 c.c. of the
bichromate solution then run in from a burette, and the liberated iodine
titrated with the thiosulphate solution.
To save time in the calculations, the author has prepared a Table in
0'2
which the logarithms of the quotients t-. 7~. are given.^
c.c. thiosulphate
^ J. Lewkowitsch, Laboratory Compa?tion to the Fats ajid Oils Industries, Table II, p. 28.
118 OILS, FATS, AND WAXES
Example— oil<^\ g. of lard were treated with 25 c.c. of iodine
chloride, which required in a blank test 60-9 c.c. of thiosulphate solution,
1 6-45 c.c. of which were equivalent to o-2 ^. of iodine. For titrating
back the excess of iodine 396 c.c. of thiosulphate solution were required.
Hence the iodine absorbed corresponds to 609- 396 = 21-3 c.c. thio-
sulphate solution. Since 16-45 c.c of thiosulphate are equivalent to
0-2 e. iodine, the iodine absorbed is " r" . — = 0-25S9 ?• Hence
° 1 0-45
r, , , , 0-2589 X 100 ^ o • A-
<j. of lard absorb — ^^ — = 76-28 g. lodme.
0-3394
The iodine value of the sample is therefore 76-28.
For a discussion of the theory of the complicated chemical
changes occurring in Hiibl's iodine chloride .solution, cf. Lewkowitsch,
Chemical Technology and Analysis of Oils, Fats, and Waxes, vol. i.,
pp. 398 et seq.
Wijs' Method. — Solutions of 7-9 g. iodine trichloride and Z-y g.
iodine respectively, in glacial acetic acid, are made up by warming on
the water-bath, taking care that no moisture from the air be absorbed.
The glacial acetic acid must be pure (it must give no green tinge when
warmed with potassium bichromate and concentrated sulphuric acid).
The two solutions are poured into a litre flask and made up to i litre
with glacial acetic acid.
In a laboratory in which many iodine values are determined, it will
be found cheaper to dissolve 13 g. of iodine in i litre of glacial acetic acid,
to ascertain the exact titre of the solution by means of thiosulphate, and
then to pass washed and dried chlorine gas into the solution until the
titre has exactly doubled. With a little practice, the exact point
at which the iodine has just become converted to iodine chloride
can be judged by the change in colour of the solution.
The iodine value is determined exacth- in the manner described
above for Hiibl's method. Carbon tetrachloride is used as the solvent
instead of chloroform, as the latter frequently contains alcohol. Wijs'
solution can, however, be used immediately after preparation, and
remains unaltered for months, so that it is not necessary to carry
out a blank test in every case. The solution also offers the great
advantage that solid fats and non-drying oils require only half an
hour, semi-drying oils one hour, and drying oils two to six hours
(according to the iodine absorption) for the completion of the
reaction.
The iodine value is one of the most important data in the analysis
of fats, as all oils, fats, and waxes within the groups given in the Tables
below can be arranged in a natural system according to the magnitude
of the iodine values (see Tables, pp. 146 et seq.).
REICHERT VALUE
119
3. Determination of the Reichert (Reichert-MeissI, or Reichert-
Wollny) Value.
The Reichert (Reichert-MeissI, or Reichert-Wolhiy) value indicates
the number of cubic centimetres of A^/io potassium hydroxide necessary
for the neutralisation of that portion of the soluble volatile fatty acids
which is obtained from 2-5 g. (or 5 g.) of a fat by the Reichert distillation
process.
E. Reichert, who introduced this method into the analysis of fats,
used 2- 5 g. of fat for the estimation ; it is, however, now more usual to
take 5 g, of fat, as recommended by E. Meissl and R. Wollny. The
Reichert-MeissI or Reichert- Wollny value is not, however, simply twice
that of the Reichert value, as is frequently assumed. It is always
necessary to state precisely how the distillation has been carried out.
Fig. 36.
as the results differ somewhat according to the method adopted. As a
rule, however, the Reichert-MeissI or Reichert-Wollny value may be
taken as approximately 2-2 times the Reichert value.
The following details of the method have been agreed upon by a
Committee of the Government Laboratory and the Society of Public
Analysts.^
The Reichert- Wolhiy Method. — The apparatus used is shown in
Fig. 36. The fat is filtered and 5 g. are introduced into a 300 c.c. flask.
A sodium hydroxide solution is made up by dissolving pure 98 per
cent, sodium hydroxide in an equal quantity of water. This solution
must be preserved from the action of atmospheric carbon dioxide as
completely as possible. 2 c.c. of this solution and 10 c.c. of alcohol
(about 92 per cent, strength) are added to the fat, and the mixture is
^ Analyst^ 1900, 25, 309.
120 OILS, FATS, AND WAXES
heated under a reflux condenser for about fifteen minutes on a boiling
water-bath. The alcohol is then distilled off on the water-bath until a
dry soap is left. This is dissolved in lOO c.c. of hot water, which
has been previously boiled for at least ten minutes, the flask being
heated until all has passed into solution. Then 40 c.c. oi N/i sulphuric
acid, and three or four pieces of pumice, about the size of peas, are
added, and the flask at once connected by means of the bulb-tube to the
condenser. The flask is heated on a sheet of asbestos 12 cm. in
diameter, and having a hole in its centre 5 cm. in diameter. The flame
is at first turned low to melt the fatty acids. W^hen these have become
clear, the flame is turned up, and the solution distilled so that exactly
no c.c. pass into the measuring flask in thirty (twenty-eight to thirty-
two) minutes. The distillate is shaken, 100 c.c. are filtered off, 0-5 c.c.
of an alcoholic solution of phenolphthalein (i g. in 100 c.c.) added to the
filtrate, and this then titrated with A710 alkali or baryta.
A blank experiment is made in exactly the same manner with the
same reagents. The A710 alkali used in this test must not exceed 0-3 c.c.
The amount of alkali used in the blank experiment is subtracted from
that used in the actual experiment, and the difference is multiplied
by I -I.
The number thus found is the Reichert-Wollny value ; the Reichert-
Meissl value is almost identical with this. The Reichert-Meissl value
of the majority of oils and fats, namely, those whose saponification value
is below 200, is less than 0-5. All oils and fats whose saponification
values exceed 200 have Reichert-Wollny values above i-o.
The Reichert-Meissl value furnishes important information as to the
nature of an oil or fat. Thus, butter fat is characterised by a Reichert-
Wollny value of about 27-29, the fats of the cocoa-nut oil group have a
Reichert-Wollny value of 5-8, and finally, dolphin oil and porpoise oil
have Reichert-Meissl values of 47-120 (cf. Tables on pp. 146 et scq.).
The Leffmann-Beam saponification method is generally used when it
is desired to determine at the same time the titration number of
the insoluble volatile fatty acids (see p. 156).
A solution of 100 g. of sodium hydroxide in 100 c.c. of water is made
up, and 20 c.c. of this solution are mixed with 180 c.c. of pure concen-
trated gl)-cerol. 20 c.c. of this glycerol alkali solution and 5 g. of the
filtered fat arc placed in an Erlenmeyer flask, and heated for two or three
minutes over a free flame until the water is driven off, and the liquid is
clear. For the rest, the procedure is the same as described above.
Determination of the Acetyl Value.
The acetyl value indicates the number of milligrams of potassium
hydroxide required for the neutralisation of the acetic acid obtained
on saponifying i g. of the acetylated fat or wax.
ACETYL VALUE 121
The determination of the acetyl value of oils and fats is based on
the principle that glycerides containing hydroxylated fatty acids take
up an acetyl group for each hydroxyl group on heating with acetic
anhydride. The chemical change consists, therefore, in the replacement
of the hydrogen atom of the alcoholic hydroxyl group or groups by the
radicle of acetic acid.
The determination of the acetyl value is carried out by the method
given by the author^ as follows : — lo g. of oil are heated for one or two
hours under a reflux condenser with double the quantity of acetic
anhydride. The solution is then poured into a beaker of looo c.c.
capacity, mixed with 500-600 c.c. of boiling water, and heated for half
an hour, a slow current of carbon dioxide being at the same time passed
through the liquid ; this prevents the liquid from bumping. The
mixture is allowed to separate into two layers, the water layer syphoned
off, and the oily layer boiled out three times successively with water.
The last traces of acetic acid are removed in this way, the liquid
being tested with litmus paper. If the heating be unduly prolonged,
the acet}'l derivative is hydrolysed to an appreciable extent, and the
acetyl value found is too low. The acetylated product is then filtered
through a dry filter paper in a drying oven.
About 5 g. of the acetyl derivative are then saponified by boiling
with an accurately measured quantity of alcoholic potassium hydroxide,
as described under the determination of the saponification value
(p. 1 14). The alcohol is evaporated off, the soap dissolved in water and
a quantity of Nji sulphuric acid added, equivalent to the alcoholic
potash used. On careful warming, the fatty acids separate as an oily
layer, which is then filtered off and washed with boiling water until the
washings are no longer acid. The filtrate is then titrated with Njio
alkali. The number of cubic centimetres required is multiplied by 56-1
and divided by the weight of substance. Triglycerides which contain
no hydroxy-acids and no soluble fatty acids give no acetyl value. Tri-
glycerides of hydroxylated fatty acids give the values required by
theory, hence the acetyl value is in this case a characteristic of the fat.
Triglycerides which contain hydroxy-acids, and at the same time
also soluble fatty acids, give acetyl values which include also the soluble
acids. In order to obtain the true acetyl value, the quantity of alkali
required to neutralise the soluble acids (which must be determined by a
blank experiment) must be subtracted from the apparent acetyl value, as
determined above. In this case also the acetyl value is a characteristic.
In the natural oils and fats, however, which contain varying
quantities of free fatty acids, and hence also varying quantities of
monoglycerides and diglycerides, the acetyl value is a variable, as its
value depends not only on the presence of hydroxy-acids, but also on
' J. Soc. Chem. Inci., 1897, 16, 503.
1 9 0
1 Ml ^
OILS, FATS, AND WAXES
the amount of monoglycerides and diglycerides present. The natural
oils and fats contain also small quantities of free alcohols, which also
contribute in some degree to the acetyl value. As oxidised acids (see
p. 139) also give acetyl values, the acetyl value is very probably a
measure of the rancidity of an oil or fat.^
(b) Variables.
The following variables are considered here : —
1. The Acid Value.
2. The content of Glycerol.
3. The Unsaponifiable Matter.
I. Determination of the Acid Value.
The acid value indicates the number of milligrams of potassium
hydroxide required to neutralise the free fatty acids in i g. of fat or wax.
The acid value is thus a measure of the free fatty acids in a fat or
wax. For the determination an accurately weighed quantity — as a rule
not less than 5 g. — is mixed with neutral (or neutralised) alcohol, or
dissolved in a mixture of alcohol and ether, and titrated with aqueous
or alcoholic potassium hydroxide, with phenolphthalein as indicator.
The acid value is calculated as shown in the following example: —
Example. — For the neutralisation of the free fatty acids in 6- 508 g.
of tallow, 3-5 c.c. of A710 potassium hydroxide were required, corres-
ponding to 3-5 X 5-61 mg. KOH. The quantity required for i g. is
r 3-5X5-6I
therefore -^ — =7; — = 3-01.
6-508 ^
The acid value is frequently expressed in per cent, of oleic acid ; it
is then sufficiently accurate to give half the acid value as the percentage
of free fatty acid.
Older methods of calculating take as units, in some cases, the
quantity of acid calculated as sulphuric acid ; in others, the "degrees of
acidity," that is, the number of cubic centimetres of normal alkali required
to neutralise 100 g. of fat. The following Table facilitates the conversion
of one term into anv other : —
Acid value.
Oleic acid.
SO3.
Degrees of acidity.
Per cent.
Per cent.
1-0
0-5036
0-0714
1-7857
rgs.'i?
1-0
0-142
3-5458
14-0
7-042
1-0
25-0
0-5G
0-2817
0-04
1-0
' Cf. Lewkowitsch, Chemical Technology and Analysis of Ois, Fats, and Waxes, vol. i,
P- 435-
CONTENT OF GLYCEROL 123
In the literature on fats the acid value is much too frequently con-
sidered as a "characteristic" (constant). This is entirely misleading,
as the acid values of the natural oils and fats, and perhaps also of the
waxes, are dependent upon the purity of the sample, the age, the degree
to which hydrolysis has occurred, and any oxidation which has taken
place. The acid value may therefore vary from o to the maximum of
about 195 for any fat; the latter value would correspond to 100 per
cent, of free fatty acids, which number the author has, in fact, found in
the case of a very old palm oil.
The designation of the "ether value" or "ester value" (that is, the
difference between the saponification value and the acid value) as a
"characteristic " (constant) is equally misleading.
2. Determination of the content of Glycerol,
If the natural oils and fats were neutral triglycerides, the quantity of
glycerol could be calculated from the saponification value according to
the following equation : —
C3H,(OR)3 .+ 3KOH = C3H3O3 + 3KOR.
In this case the glycerol content would form a "characteristic." As,
however, the majority of the natural oils and fats contain free fatty
acids, and hence in all probability mono- and diglycerides, the glycerol
content varies, and must therefore be considered as a "variable."
The determination of glycerol in oils and fats is best effected
indirectly by the acetin method, as the glycerol obtained by the saponi-
fication of a fat invariably contains organic impurities, which give
abnormally high values when the glycerol is determined by oxidation
(by permanganate or bichromate).
For the acetin method, a crude glycerin must first be prepared.
For this purpose, 20 g. of the sample are saponified with alcoholic
potash as described under the determination of the saponification value
(p. 1 14), and the alcohol evaporated off on the water-bath. The
resulting soap is dissolved in water, and decomposed by sulphuric acid,
so that the precipitated fatty acids may be filtered off. The filtrate is
treated with excess of barium carbonate, and evaporated on the water-
bath until the bulk of the water is driven off. The residue is then
extracted with a mixture of ether and alcohol (i : 3), the bulk of the
ether-alcohol evaporated off by careful heating on the water-bath, and
the residue dried in a desiccator and weighed. It is not necessary to
dry to constant weight, as the glycerol in the crude product is accurately
determined by the acetin method.
This method depends upon the complete conversion of glycerol to
triacetin on boiling with acetic anhydride, and the subsequent hydrolysis
of the product with sodium hydroxide. The acetic acid thus formed is
124 OILS, FATS, AND WAXES
a measure of the amount of glycerol. The crude gl)xerol obtained as
above is heated to boiling with 8-10 c.c. of acetic anhydride and 4 g. of
sodium acetate, in a round-bottomed flask of about 100 c.c. capacity,
under a reflux condenser, for one and a half hours. It is then allowed
to cool a little, the condenser rinsed out with hot water, and the acetin
brought into solution by gentle agitation. If necessary, the contents
of the flask may be gently heated, but must not be boiled, as triacctin
is volatile with steam. The liquid is filtered from a flocculent pre-
cipitate which separates into a wide-necked flask of about 500-600 c.c,
capacity, and allowed to cool to the ordinary temperature. Phcnol-
phthalein is added, and the acetic acid neutralised with sodium hydroxide
of about 5 per cent, strength. During the addition of the alkali
the flask must be continually shaken round so that there is never
any local excess of alkali. The neutral point is reached when the pale
yellow colour just becomes reddish-yellow. The addition of so much
alkali that a red colour is formed must be avoided. If an excess has
been accidentally added, so that the neutral point has been over-
stepped, the experiment must be rejected. With practice the colour
change can be easily observed. Exactly 25 c.c. of sodium hydroxide
solution of about 10 per cent, strength are then added, the strength of
this solution being determined by a blank experiment, and the solution
is boiled for a quarter of an hour. The free alkali in both experiments
is then titrated back with Nji hydrochloric acid ; that is, the total alkali
in the blank experiment, and the excess of alkali in the experiment
proper. The difference gives the amount of alkali required for tht
saponification of the triacetin.
Example. — 1-5064 g. crude glycerin weighed out. 25 c.c. sodium
hydroxide solution required in the blank experiment, 53-0 c.c. Nil
hydrochloric acid, and in the actual experiment, 14-7 c.c. Nji hydro-
chloric acid for the back-titration. Hence, 530— i47 = 38-3 c.c. were
required for the saponification of the triacetin. Since 1 c.c. A71
hydrochloric acid corresponds to — ^ = 0-03067 g. glycerol, the crude
glycerin contained 0-03067 x 38-3 = 1-1746 g. glycerol (= 77-97 per
cent, glycerol). The 20 g. fat originally taken for the test contained,
therefore, 1-1746 g. glycerol, or 5-87 per cent.
A direct method for the determination of glycerol, proposed
by A. Shukoff and P. Schestakoff,i by extraction of a solution containing
at least 40 per cent., has not yet met with general acceptance on
account of its tediousness.
3. Determination of the Unsaponifiable Matter.
The term "unsaponifiable matter" comprises all those sub.stances
* Z. angew. Chem., 1905, 18, 294 ; J. Soc. Clum. Iml.y 1905, 24, 294.
UNSAPONIFIABLE MATTER 125
which are insoluble in water, or which do not form soluble soaps with
caustic alkalis. The natural oils and fats always contain small
quantities of unsaponifiable matter.
The unsaponifiable matter is separated as such, and to this end the
fat must first be saponified. It is convenient to combine the determina-
tion of the unsaponifiable matter with that of the saponification value;
it must, however, be borne in mind, that in view of the very small
quantity of unsaponifiable matter, it is necessary to take at least 5 g. for
the test The procedure is as follows : — 5 g. of the sample are saponified
with 25 c.c. of alcoholic sodium hydroxide, containing 80 g. of sodium
hydroxide per litre, by heating on a water-bath in a porcelain dish, and
evaporated to dryness. The soap is dissolved in 50 c.c. of hot water,
transferred to a separating funnel of about 200 c.c. capacity, and the
residual contents of the dish rinsed into the separator with 20-30 c.c. of
water. After cooling, about 50 c.c. of ether are added, and the whole
is well shaken. If the layers do not separate readily, a little alcohol or
concentrated sodium hydroxide is added. The clear soap solution is
run off into a second separating funnel and shaken out again with
ether. The ethereal extracts are combined, washed with a little water,
and transferred to a weighed flask. The ether is evaporated off on
the water-bath, the residue dried at 100°, and weighed. In the case of
most oils and fats, ether is preferable to petroleum spirit for the
extraction.
This method is not suitable for determining the unsaponifiable
matter in beeswax, carnauba wax, and other solid waxes, as not only
are the alcohols derived from these esters sparingly soluble in cold
ether, but also the alkali salts of the fatty acids do not dissolve easily
in water, nor even in dilute alcohol. In such cases it is advisable
to neutralise the soap solutions, after adding phenolphthaiein, with acetic
acid, and to precipitate with either barium chloride or lead acetate.
The precipitate is then washed, dried, mixed with sand in a mortar,
and extracted in a Soxhlet apparatus with petroleum spirit boiling
below 80°.
A characteristic component of the unsaponifiable matter of vegetable
oils and fats is sitosterol or other closely allied phytosterols ; the
unsaponifiable residue of animal oils and fats, on the other hand, contains
cholesterol. A further examination of the unsaponifiable matter
is imperative when it is necessary to distinguish between vegetable and
animal fats (see p. 1 39).
II. QUALITATIVE METHODS.
The following qualitative methods of examination frequently yield
important clues for the detection and valuation of individual oils and
fats, and must be used to supplement the quantitative reactions, when
126 OILS, FATS, AND WAXES
the latter fail to give definite indications. A number of qualitative
reactions have become superfluous since the method of determining the
iodine value has come into use, e.g., the elaidine test, the sulphur
chloride test, and also the thermal reactions with sulphuric acid,
bromine, and sulphur chloride. Only the following methods need
therefore be described : —
1. Oxygen absorption.
2. Bromide test.
3. Colour reactions.
I. Oxygen Absorption.
The absorption of atmospheric oxygen is of great importance
in judging the danger of spontaneous combustion when oils are
distributed in a finely divided condition on organic fibres {cf. "Wool
oils," p. 160) ; it is generally determined in the case of drying oils. The
methods used for this purpose are mostly " practical " tests ; these are
described in the following Section (p. 165).
If a convenient method for the determination of the total oxygen
absorbed during drying were available, it would be possible to obtain a
quantitative expression of the drying properties, or as it might be
termed, of the " oxygen value." Quantitative determinations have in
the past been made, but in a very unsystematic fashion, such important
factors as the temperature, the influence of light, the moisture of the air,
the thickness of the layer, and the age of the oil having been more or
less ignored.
As the drying of an oil requires a somewhat lengthy period of time,
attempts have been made to accelerate the absorption of oxygen, by
adding finely divided lead (" molecular " lead) (A. Livache^), or finely
divided copper (Hubl, Lipperf-). The lead powder is obtained by
precipitating a lead salt by means of zinc. The precipitate is washed
with water, alcohol, and ether in rapid succession, and finally dried in a
vacuum. Livache's test is carried out as follows : — i g. of the lead
powder is spread out in a thin layer on a fairly large watch-glass, and
0-6-07 g. (not more) of the oil allowed to drop on to the powder,
care being taken to let each drop fall on to a separate place on the lead
(or copper) powder, and not to allow the drops to run together. The
watch-glass is then allowed to stand at the ordinary temperature in the
li'^ht. Linseed oil attains its maximum absorption in a few days,
whereas under other conditions the same result is obtained only after a
prolonged time. Livachc states that drying oils attain their maximum
absorption in eighteen hours, or in some cases after three days, whereas
non-drying oils show an increa.se of weight only after four to five days.
1 CompUs rend., 1886, 102, I167 ; y. Soc. CJieiii. IiuL, 1886, 4, 494.
- Uum. Revue, 1 899, p. 67.
OXYGEN ABSORPTION 127
Weger ^ rejects Livache's method and suggests the use of larger
quantities of lead, 2 g. of lead being used for each o-2 g. of oil. But
even under these conditions the results are unsatisfactory.
M. Weger- and also W. Lippert^ have undertaken a systematic
study of the drying properties of oils, the oils being exposed to the air
in extremely thin layers on glass plates. It was shown that the glass
plates could not be replaced by any other lighter material ; plates of
celluloid, gelatin, and even ebonite were found altogether unsuitable ;
mica plates were satisfactory but are too easily broken, whilst thin
metal plates are too easily deformed. The following precautions are
necessary in the experiments : — The glass plate must be quite clean
(free from dust), and the oil must be very carefully spread out in a
uniform thin layer. If the layer is uneven in thickness, it is possible
for an increase of weight to be taking place in one place, whilst a
decrease is occurring at another. A series of tests showed that, the
thinner the layer of oil, the more rapidly the oxygen is absorbed at
the commencement of the experiment, whilst an equilibrium sets in
after about twenty-four hours. The thicker the layer, the more slowly
the weight increases; but if the layer is altogether too thin, unreliable
results are obtained. The best conditions for the absorption of oxygen
seem to be reached when the layer of oil is so thin that 0-0005 g- cover
I sq. cm. of the glass plate.
This method is obviously very tedious, and depends upon the
accuracy with which decimilligrams can be weighed ; moreover, it
does not yield absolute data, and can only be used as a guide in
comparative experiments. If it is only a question of distinguishing
between drying, semi-drying, and non-drying oils, the determination of
the iodine value (p. 1 16) is not only more easily carried out, but has also
the advantage of giving quantitative results. At the same time, it must
be emphasised that the iodine value is not an absolute measure of
the drying properties ; for fish oils and liver oils add just as much
iodine as the best drying oils, and yet absorb much less oxygen.
Furthermore, the former are distinguished essentially from the latter
in that they do not form a skin as linseed oil does. Fish oils and liver
oils are, however, best distinguished from the drying oils by the bromide
test (^/ p. 137).
2. The Bromide Test.
On the basis of Hazura's work on the action of bromine on
unsaturated acids, O. Hehner and C. Mitchell ^ proposed the following
1 Chem. Revue, 1898, p. 246.
2 C/iem. Rev Fett-lnd., 1897, 4, 313, 327 ; /. Soc. Chem. Ind., 1898, 17, 257, 360.
3 Chem. Rev. Feit-fnd., 1899, 6, 65 ; /. Soc. Chem. hid., 1899, 18, 693.
* Analyst, 1898, 23, 313-
128
OILS, FATS, AND WAXES
test, which is described with certain modifications which have been
worked out in the author's laboratory : — 1-2 g. of the oil are dissolved
in 40 c.c. of ether with the addition of a few cubic centimetres of glacial
acetic acid. The solution is cooled in a corked flask to 5°, and bromine
then added, drop by drop, from a drawn-out tube, until the brown
colour no longer disappears. After standing for three hours at 5°, the
liquid is filtered through a pleated filter and washed four times
successively with 10 c.c. of ether cooled to 0°. The residue is finally
dried in a water-oven to constant weight. In the following Table a
number of results obtained by this test are collated, of which some are
given by Hehner and Mitchell, and the remainder obtained by the
author and his assistants. Walker and Warburton.
The bromide test is especially adapted to the testing of drying oils
and fish oils. It is still better to apply it to the fatty acids, as it is
possible in this way to distinguish between vegetable dr)'ing oils and
fish oils (cf. p. 137).
Table 21.
Yield of Hexabromides from Glycerides.
Oil.
Yield of bromides
insoluble in ether.
Observer.
Per cent.
Linseed oil (iodine value
181) .
23-14; 23-52
Walker and Warburton
II ( 11
186-4)
24-17
Lewkowitsch
11 C. 11
190-4)
37-72
11
i> • •
• •
23-86 to 25-8
Hehner and Mitchell
Tung oil .
0
II
„ (sample 1) .
0
Walker and Warburton
I, ( „ 2).
0-38; 0-39
i>
Candle nut oil .
8-21 ; 7-28
II
Walnut oil
1-42; 1-9
Hehner and Mitchell
Poppy seed oil .
0
M
Soya bean oil .
3-73
Lewkowitsch
Maize oil .
0
Hehner and Mitchell
Cotton seed oil .
0
11
11 • •
0
Lewkowitsch
Brazil nut oil .
0
Hehner and Mitchell
Almond oil
0
11
Olive oil .
0
II
Japan fish oil .
21-14 ; 22-07
Walker and Warburton
F'ish oil deodorised ,
49-01 ; 52-28
II
Cod liver oil
42-9
Hehner and Mitchell
11 ■ "
35-33; 33-76
Walker and Warburton
,, (Newfoundl
and)
32-68 ; 30-62
11
Shark liver oil .
22
Hehner and Mitcliell
II * •
21 •2-2; 19-08
Walker and Warburton
Seal oil .
27-54 ; 27-92
11
Whale oil
25
Hehner and Mitchell
(old) . .
15-54; 16-14
Walker and Warburton
„ (fresh)
20-1 ; 22-6
Lewkowitsch
Sperm oil.
2-61 ; 2-42
Walker and W^arburton
11 • • •
3-72; 3-69
11
after standing for
48 hours
COLOUR REACTIONS 129
3. Colour Reactions.
Of the almost innumerable colour reactions which have been
proposed, and are still being proposed, only the following, as the
author has shown by extensive tests, can be recommended as trust-
worthy and of practical value.^
(a) H. Baudouvi's Test. — This reaction, originally introduced by
Camoin, is used for the detection of sesame oil, certain components of
which give a characteristic red colour with hydrochloric acid and cane
sugar. As cane sugar is converted by hydrochloric acid into levulose
and furfural, Villavecchia and Fabris have suggested the following
method of carrying out the test : — A solution of i vol. of colourless
furfural in lOO vols, of absolute alcohol is made up, and to o-i c.c. of this
solution, 10 c.c. of the sample, and 10 c.c. of hydrochloric acid of sp. gr.
1-19 are added, the whole well shaken and allowed to settle. If the
sample contains even less than i per cent, of sesame oil, the lower
aqueous layer shows a distinct crimson-red colour. In case colouring
matters are present in the fat, which give a coloration with hydro-
chloric acid alone, these should be removed first by shaking the sample
with concentrated hydrochloric acid. The only objection to this treat-
ment is that it is sometimes necessary to repeat the shaking so many
times that the chromogenetic substance in sesame oil is also destroyed.
(b) Halphen's Test. — This indicates cotton seed oil. Equal volumes
of the sample, amyl alcohol, and carbon bisulphide containing i per
cent, of flowers of sulphur in solution, are heated for fifteen to thirty
minutes in a test tube in a water-bath or salt water-bath for fifteen to
thirty minutes. In presence of cotton seed oil a characteristic red
colour is obtained. The value of this test must not be overestimated
since on the one hand cotton seed oil, which has been previously heated
to i8o°-25o'', fails to give the reaction, and on the other hand when cattle
are fed with cotton seed oil cakes or cotton seeds, the chromogenetic
substance passes into the milk fat ; it also passes into lard, when hogs
have been fed with cotton seed or cotton seed oil cakes. It must also
be noted that kapok oil and baobab oil also give this reaction. Recently
E. Gastaldi- has shown that only commercial amyl alcohol produces
the colour, which is therefore produced by impurities in the amyl
alcohol. Pyridine and allied bases give the colour reaction very
distinctly.
(c) Becchi's Test (Silver nitrate test). — This test for cotton seed oil
is less reliable than Halphen's. It is most trustworthy when carried
out as proposed by Tortelli and Ruggeri : 5 g. of the sample are
^ J. Soc. Chem. Ind.^ 1894, 13, 617 ; also Lewkowitsch, Chemical Technology and Analysis of
Oils, Fats, and Waxes, \o\. i., pp. 398 et seq.
^ Ami. Lah. Gabelle, 1912, 6, 601 ; J. Soc. Chem. hid., 1912, 31, 934.
Ill I
130 OILS, FATS, AND WAXES
saponified and the liquid fatt\' acids are isolated {cf. p. 134); these are
dissolved in 10 c.c. of 95 per cent, alcohol, i c.c. of a 5 per cent, solution
of silver nitrate added, and the solution warmed to 70'-8o'. In presence
of cotton seed oil, the silver nitrate is at once reduced, whereas other
oils reduce it only after a considerable time.
(d) The Nitric Acid Test is frequently useful as a preliminary
indication of cotton seed oil. A few cubic centimetres of the sample
are shaken with an equal volume of nitric acid of sp. gr. 1-375 and
allowed to stand for some time (up to twenty-four hours). In presence
of cotton seed oil a coffee-brown colour is observed, which is still
produced by heated cotton seed oil and its fatty acids (which, as stated
above, fail to give the Halphen reaction).
The three last-mentioned colour reactions for the detection of cotton
seed oil must be used with the greatest circumspection, and must be
considered at the best only as confirmatory tests.
(e) Liebcrj)iann-Sto)-ch Test. — This colour reaction is extremely
trustworthy for the detection of rosin oils. A quantity of 1-2 c.c. of
the sample is dissolved in acetic anhydride with moderate warming ;
after cooling a dpop of sulphuric acid of sp. gr. i-53 (prepared by
mixing 34-7 c.c. of concentrated sulphuric acid with 35-7 c.c. of water)
is added. In presence of rosin acids a beautiful violet-red fugitive
colour is obtained. Cholesterol also gives a similar colour. If the
latter is suspected the rosin acids must be separated from the
unsaponifiable cholesterol. The best method for the detection of
cholesterol is described below (p. 139).
(f) The Sulphuric Acid Test. — All the colour reactions with sulphuric
acid given in the older literature are unreliable, with the exception of
the reaction for the detection of liver oils.
To carry out the test i drop of the oil is dissolved in 20 drops of
carbon bisulphide, and a drop of concentrated sulphuric acid is added.
If liver oils are present a violet-blue colour is produced, which quickly
changes to red and brown. The colour seems to be produced not only
by cholesterol but also by " lipochromes."
C. — Examination of the Fatty Acids.
In case the methods described above have not given sufficient
information for the identification of a sample, the free fattv acids must
be examined. For this purpose physical methods such as the deter-
mination of the solidifying point (titre) {cf. the following Section, p. 174,
and Tables, p. 146) are used, but more especially the following chemical
methods, which are to some extent based upon the above quantitative
reactions.^
^ For further methods, cf. Lewkowitsch, Chemical Technology and Analysis of Oils, Fats, and
Waxes, vol. i., chap. viii.
EXAMINATION OF FATTY ACIDS 131
1. Determination of the Neutralisation Value, from which the mean
molecular weight can be derived.
2. Determination of Lactones (Anh)drides).
3. Determination of Insoluble Fatty Acids.
4. Determination of Soluble Fatty Acids.
5. Separation of Saturated Fatty Acids from Unsaturated.
6. Examination of the Saturated Fatty Acids.
7. Determination of Oleic, Linolic, Linolenic, and Clupanodonic
Acids.
8. Determination of the "Oxidised" Fatty Acids.
The free fatty acids are prepared as described in the following
Section under the "determination of the titre of tallow," p. 174).
The soluble volatile fatty acids need only be taken into consideration
in the case of oils and fats whose saponification value exceeds
200.
If great accuracy is desired, the unsaponifiable matter should be
removed with ether, before decomposing the soap solution with mineral
acid (see p. 124).
I. Determination of the Neutralisation Value and the
Mean Molecular Weight.
The neutralisation value indicates the number of milligrams of
potassium hydroxide required to saturate i g. of the mixed fatty
acids.
The determination of the neutralisation value is carried out in
exactly the same manner as described under "acid value" (p. 122), but
using aqueous normal alkali. It is advisable to take at least 5 g. of
the sample for the determination. Deductions as to the approximate
composition of a mixture of fatty acids may be obtained from the
following Table {cf. also the Tables given on pp. 146 et seg.).
From the neutralisation value thus found, the mean molecular
weight is calculated as follows : — Let M be the mean molecular weight
of the fatty acid ; then M grams must, according to theory, be
neutralised by 56-1 g. potassium hydroxide. If « be the number of
grams of potassium hydroxide which have been shown by experi-
ment to neutralise i g. of fatty acid, then the proportion M : 56-1
= I : ;/. and hence M = . The value of fi is found by multiplying
n
the number of cubic centimetres of normal alkali required for i g. fatty
acid by 00561, If this number of cubic centimetres be a then
n = rtX 0-0561. Introducing this into the above equation : —
T\,T 56-1 1000
M = — ~ >- = .
^xo-050i a
132
OILS, FATS, AND WAXES
Table 22.
Neutralisation Values of Fatty Acids.
Aci-I.
Formula.
Molecular weight.
Neutralisation
value. 1
Acetic ....
C..H,0..
60-03
934-5
1 Butyric
c^H.o.;
88-06
637-07
Caproic
CfiHrP,
116-10
483-22
1 Caprylic
C,H„P,
144-13
389-23
Capric .
CiqHoo^'o
172-16
325-85
Laurie .
CijHjjiOa
'200-19
280-30
Myristic
C]4H2f,02
228-22
245-81
Palmitic
Ci«H,.0,
256-26
218-90
Stearic .
C,,H,^0,
284-29
197-33
Oleic .
^lHri^CJ.>
282-27
198-74
Linolic
cZ^hPl
278-24
200-17
' Linolenic
CigHgoOo
280-26
201-62
Clupanodonic
^IH"-28^-2
276-22
203-09
Ricinoleic
^is^.-mOs
298-29
188-08
' Arachidic
^20"-4o'-'2
312-32
179-62
Erucic .
V-/.>> ti 42^2
338-34
165-81
Cerotic
C36HB2O2
396-42
141-52
Melissic
^30 "60^2
452-48
123-98
Hydroxystearic
CisHneO;;
300-29
186-81
' Dihydroxysteaiic
C]8H.3604
316-29
177-33
Triiiydroxystearic
^is^'se'-'s
332-29
168-82
Sativic .
CigHseOe
348-29
161-07
Linusic
CisHsfiOg
380-29
147-51
2. Determination of Lactones (Anhydrides.)
If the free fatty acids, instead of being examined for their neutralisa-
tion values as described above, are boiled with excess of alcoholic
potash as in the determination of the saponification value (p. 1 14), the
same value should be obtained, or in other words, the saponification
number of a fatty acid should be identical with its neutralisation value
on the assumption that the amount of unsaponifiable matter is negligible.
If, however, the fatty acids contain lactones or anhydrides, the saponifica-
tion value will be greater than the neutralisation value. The difference
forms a measure of the lactones or anh)'dridcs present. Its determina-
tion is of importance in the examination of candle materials (see next
Section, p. 173).
3. Determination of Insoluble Fatty Acids.
For this determination the fat is filtered, and 3-5 g. arc saponified as
described under "saponification value" (p. 114), using, of course, a flask
of double the capacity given above. The alcohol is then completely
evaporated off, until the snap solution becomes thick. Then i(X)-i50c.c.
of hot water are added, the solution acidified with dilute sulphuric acid,
and heated until the liberated fatty acids float on the surface as a clear
EXAMINATION OF FATTY ACIDS 133
oily layer. The solution is next filtered through a filter paper of about
lo cm. diameter, previously dried at lOo" and weighed, taking care first to
fill the filter paper half full of hot water. The liquid is then brought on to
the filter, keeping it half full throughout the operation. The fatty acids
are washed with hot water on the filter, until a few cubic centimetres of
the filtrate no longer redden sensitive litmus paper. In the case of
fats of the cocoa nut oil and dika fat groups, 2 or 3 1. of water are
sometimes necessary. On the completion of the washing the funnel and
filter are immersed in cold water, so that the liquid in the filter and the
water outside are at the same level. This causes most fatty acids
to solidify. The water is allowed to drain off, the filter brought into a
small weighed beaker and dried for two hours at 100". After weighing,
the drying is continued for an hour, and the weighing repeated. The
difference between the two weights does not usually exceed i mg. ;
absolute constancy cannot be expected, as there are two sources of
error, which, however, usually compensate one another. On the one hand
unsaturated fatty acids become slightly oxidised, and on the other hand
they volatilise to some extent. The fatty acids of highly unsaturated
oils are best washed with, ether into a tared flask, and dried in a current
of carbon dioxide or hydrogen.
Most fats give a yield of 95 per cent. ; only those fats which have
high Reichert values yield less than 95 per cent. It must be borne in
mind that any unsaponifiable matter is weighed with the acids, and that
the yield cannot therefore be identified with the percentage of fatty
acids. In most oils and fats the proportion of unsaponifiable matter
may, as a rule, be neglected, but in accurate analyses this must
be determined as described on p. 124, and deducted. In the case
of waxes, the alcohols separate out together with the fatty acids, and
thus results exceeding 100 per cent, are obtained,
4. Determination of Soluble Fatty Acids.
A high Reichert- Meissl value points to the presence of considerable
quantities of volatile fatty acids. The volatile fatty acids — comprising
butyric, caproic, caprylic, capric, and lauric acids — are conveniently
subdivided into soluble volatile acids and insoluble volatile acids,
although a sharp analytical distinction between these two classes cannot
be drawn. The Reichert- Meissl method estimates a. part of the soluble
volatile fatty acids (almost all the butyric acid, part of the caproic, and
a little caprylic acid). Similarly Polenske's method which is carried out
in conjunction with the Reichert-Meissl method (see p. 156) gives
approximatel}' the insoluble volatile acids (comprising very little butyric
acid, a little caproic, more capr)'lic, almost all the capric and all the
lauric acid which has passed over, together with traces of myristic acid).
In the analysis of butter fat for the detection of fats of the cocoa nut oil
13t OILS, FATS, AND WAXES
group, the determination of both groups of acids and of their mean
molecular \veiL;ht leads to important results.^
5. Separation of Saturated from Unsaturated Fatty Acids.
The best method (though still an incomplete one) for this separation
is based upon the solubility of the lead salts of unsaturated fatty acids
in ether, in which the lead salts of the solid fatty acids are almost
insoluble. This method is most trustworthy when carried out in the
following manner worked out in the author's laboratory. The method
depends upon a combination of the modifications proposed by ?iluter
and de Koningh, and by Lane, to a method originally devised by
Gusserow and Varrentrapp.
From 3-4 g. of the fatty acids are neutralised in the usual manner in
a 300 c.c. flask, with 50 c.c. of about Nj2 aqueous potassium hydroxide.
(If the determination is started with the original fat this must be boiled
with alcoholic potash to saponify it. After adding phenolphthalein the
solution is rendered faintly acid with acetic acid, and finally exactly
neutralised with alcoholic potash). The solution is made up to about
100 c.c. with water. A solution prepared from 30 c.c. of a 10 per cent,
solution of lead acetate and 150 c.c. of water, is then heated to boiling
in a beaker, and poured, whilst boiling hot, into the soap solution,
shaking continuously, so that the precipitated lead soaps ma}' deposit
themselves on the walls of the flask. The flask is filled to the neck with
hot water and allowed to cool. After the liquid has become clear it is •
poured off or filtered if necessary. The lead soaps are carefully washed
with hot water. It is advisable to cool the hot solutions before filtering,
thus causing the cooled lead soaps to adhere to the sides of the flask.
The last traces of water are removed b\' means of a small roll of filter
paper. It is not advisable to dry the lead salts, as in the case of dr)'ing
oils they absorb oxygen somewhat rapidly from the air. Next 150 c.c.
of ether are added to the lead salts, the flask corked and shaken
repeatedly, so as to disintegrate the lead salts. The flask is then
attached to a reflux condenser, and heated on a water-bath for some
little time with frequent shaking. The lead salts of the liquid fatty
acids dissolve readily in the hot ether; at the same time a certain
quantity of the saturated acids pass into solution. When the undissolved
salts settle out at the bottom of the flask as a fine powder, the heating
is discontinued. If all operations are conducted somewhat rapidly, and
unnecessary exposure to the air is avoided, it is not essential to work
in an atmos[)here of h)'drogen or carbon dioxide. The ethereal solution
is allowed to cool, and filtered through a pleated filter covered with a
watch glass, into a separating funnel. The undissolved salts are brought
' C/. Lewkowitsch, Chemical 'leclinology and Analysis of Oils, Fats, and Waxes, vol. i., p. 538.
EXAMINATION OF FATTY ACIDS
135
on to the filter by rinsing out the flask three or four times with ether,
using 30-40 c.c. each time. The ethereal filtrate is then shaken with
dilute hydrochloric acid to decompose the lead soaps. The ether
dissolves the free fatty acids as they form, and the undissolved lead
chloride and aqueous solution are drawn off. The ethereal solution is
washed with water until the wash water is free from acid. P^inally the
Table 23.
The Iodine Value of Unsaturated Fatty Acids and their Glycerides.
Iodine value of
Acid.
Formula.
Iodine value
of
fatty af-id.
Mono-
Di-
Tri-
glyceride.
glyceride.
glyceride.
Tiglic
C5H8O2
253-68
145-79
198-18
225-10
*» *
,
CjoHmO^
128-88
93-26
112-22
120-39
*i •
,
CuHoyO.,
112-21
85-54
99-84
106-26
Hypogx'ic .
-
Physetoleic
^16"30^'2
99-84
77-32
89-93
95-10
Lycopodic .
Oleic .
"■
Elaidic
-
^I8'':u02
89-92
71-24
81-80
86-06
Rapic.
J
Doeglic
Jecoleic
}
r H r^
85-67
68-54
78-28
82-15
Erucic
Brassidic
\
C2.2H4.2O2
75-02
61-55
69-23
72-31
Linolic
J
Tariric
Telfairic
C,8H,,0.,
181-14
143-28
164-68
173-31
Elseomargaric
Linolenic .
1
/
Isolinolenic
^18 "30^2
273-69
216-16
248-65
261-76
J ecoric
Clupanodonic
18 28 2
366-24
289-04
332-63
350-23
Isanic
,
^14 20^2
461-19
345-11
409-12
436-08
Ricinoleic .
•\
Isoricinoleic
Ri(inelaidic
^18 "34^3
85-13
68-17
77-79
81-37
Ricinic
Mixed Triglycerides .
—
Myristopalmito-olein
...
31 -54
Oleodipalmitin .
, .
30-43
Oleodimargirin .
• . ■
,,
29-48
Oleopalmitostearin
> • •
• * •
, ,
29-48
Oleodistearin
28-55
Elaidodistearin .
..
28 -55
Dioleostearin
...
57-24
ether solution is filtered through a small pleated filter into an ordinary
flask. In case the liquid fatty acids consist chiefly of oleic acid, the
result.*: will be accurate enough if the ether be evaporated off on the
water-bath, and the residue dried in a water-oven. If, however, more
highly unsaturated acids than oleic are suspected (from linseed oil, soya-
bean oil, maize oil, marine animal oils), the ethereal solution must be
136 OILS, FATS, AND WAXES
evaporated down in a current of dry hydrogen or dry carbon dioxide.
The precipitate collected on the filter consists of the soaps of the
saturated fatty acids ; the free acids are obtained by decomposing these
soaps with hydrochloric acid in the manner described above.
It must be especially emphasised that this method of separation is
not absolutely accurate ; thus the solid fatty acids always retain
unsaturated acids (the quantity of which can be estimated approximately
by the iodine value). Moreover, the ethereal solution of the lead salts
retains a certain quantity of saturated fatty acids, especially the volatile
fatty acids. Nevertheless the method gives results which are sufficiently
accurate for the ordinary purposes of technical analysis. It is advisable
to estimate the iodine value of the liquid fatty acids, as this supplies
valuable information as to the composition of the fats when the Table
on p. 135 is taken as a guide {cf. also under No. 7, p. 137).
6. Examination of the Saturated Fatty Acids.
The only solid fatty acids which can at present be determined with
sufficient accuracy are arachidic and stearic acids.
Arachidic Acid. — The determination of this acid is necessary for
the recognition of arachis oil in mixtures of oils containing arachis oil
(adulterated olive oil). For the estimation, the solid fatty acids
obtained from 10 g. of oil are dissolved in 50 c.c. of hot 90 per cent,
alcohol. In presence of arachidic acid a cr)'stalline mass is obtained on
cooling the alcoholic solution. This consists of "crude arachidic acid,'\
that is a mixture of arachidic and lignoccric acids. The crystals are
filtered off and washed, first with a measured quantity of 90 per cent.
alcohol, then with 70 per cent, alcohol ; the latter dissolves only traces
of the acid. The crystals on the filter are finally washed with boiling
absolute alcohol, and the filtrate collected in a porcelain dish or a
flask. The alcohol is evaporated off and the dried crystals weighed.
A correction must be made for the arachidic acid dissolved by the 90
per cent, alcohol, taking as a basis that 100 c.c. dissolve at 15°, 0022, or
at 20°, 0-045 g- crude arachidic acid. Finally, the melting point of the
crude arachidic acid is determined ; this should be 'J\°-'J2°>
Stearic Acid. — The determination of stearic acid depends upon the
observation due to David, that alcohol saturated at 0° with pure stearic
acid, dissolves all the lower solid fatty acids as also all the unsaturated
acids, whereas stearic acid remains undissolved. The method may be
applied either to the total fatty acids, or to the saturated fatty acids
isolated as described on p. 134. It should, however, be observed that
any arachidic acid present must be removed beforehand, as it would
' For details and criticism of a modified method of estimation proposed by Tortelli and
Ruggeri, cf. Lewkowitsch, Chemical Technology and Analysis of Oils ^ Fats, and Waxes, vol. ii.,
P- 253.
SATURATED FATTY ACIDS 137
otherwise be estimated as stearic acid. O. Hehner and C. Mitchell ^ have
worked out a method on this basis, which is applicable in most cases,
though, it must be pointed out, not in all. The stearic acid solution
is prepared by dissolving 3 g. of stearic acid in lOOO c.c. of hot alcohol
of sp. gr. 0-8183 in a stoppered flask. The flask is allowed to remain
overnight in ice, and the mother-liquor is syphoned off, without taking
the flask out of the ice water. This is done with the aid of a tube
widened at the end to a small funnel which dips into the alcoholic
solution ; the small funnel is covered with fine linen to retain the
separated crystals of stearic acid. The filter tube is bent twice at right
angles, and fitted to a flask so that the clear liquid may be drawn off
quickly by means of a filter pump.
If the fatty acids are solid, o-5-i-o g. is taken; if liquid, 5 g. This
is weighed accurately in a flask, and treated with 100 c.c. of the above
described stearic acid solution. The flask is allowed to stand overnight
in ice water. On the next day the liquid is shaken, the flask being still
in the ice water, to promote the separation of crystals, and then left in
the ice water for another half hour. The alcoholic solution is drawn off
as described above, and the precipitate remaining in the flask is washed
three times successively with quantities of 10 c.c. of the alcoholic solu-
tion cooled to 0°. Finally, the crystals of stearic acid adhering to the
filter are washed into the flask with hot alcohol. The alcohol is
evaporated off, the residue dried at 100" and weighed, and calculated to
pure stearic acid. The melting point of the crystals should not be much
below 68°- 5. A correction of 0-005 g. is applied for the stearic acid
introduced by the alcoholic solution of stearic acid. If the melting
point of the isolated acid is below 68^, the acid must be again subjected
to the same treatment.
7. Determination of Oleic, Linolic, Linolenic, and Clupanodonic
Acids.
From the iodine value of the liquid fatty acids, a preliminary indica-
tion as to their nature is obtained. In the present state of our know-
ledge, the acids which come chiefly into consideration are oleic, linolic,
linolenic, and clupanodonic acids. If the iodine value is about 90, this
indicates, as a rule, practically pure oleic acid ; if, however, the iodine
value is much higher, then in the case of vegetable oils the presence of
linolic and linolenic acids is indicated, and in the case of marine animal
oils, the presence of clupanodonic acid is most probable. In the case of
mixtures, the presence of all of these acids is possible. Linolenic and
clupanodonic acids are detected by the bromide test, and are estimated
quantitatively as follows : —
1 Analyst, 1896, 21, ?2i
138
OILS, FATS, AND WAXES
A solution of 0-3 g. of the fatty acid in glacial acetic acid is cooled
in a corked flask to 5 . Bromine is then added, drop by drop, until the
brown colour no longer disappears. Any evolution of h)drogen
bromide is caused by too high a temperature. After standing for three
hours to permit of complete absorption of the bromine, the solution is
filtered through a pleated filter, and washed with four successive
quantities of 10 c.c. of cold ether. The residue on the filter is dried to
constant weight in a water-oven. The melting point of the bromide
lies between 175 and 180 , in the case of the hexabromide of linolenic
acid (from drying oils). If the bromide has not melted at 180 , but
blackens at 200' or above, it consists of octobromidcs (from marine
animal oils). If the residue be suspected to be a mixture of hexa-
bromides and octobromidcs, these are separated by boiling the residue
with benzene, in which the octobromidcs are insoluble ; the two are
identified by their melting points after the removal of the benzene.
Linolic acid may be approximately estimated in the filtrate as the
tetrabromide by the following method given by K. Farnsteiner. The
solution is evaporated and the residue, consisting presumably of a
mixture of the dibromide of oleic acid and the tetrabromide of linolic
acid, is treated with hot petroleum spirit of boiling point SS°-^7'S- ^n
cooling, a crystalline tetrabromide of linolic acid separates out, whilst a
liquid tetrabromide and the dibromide of oleic acid remain in solution.
The crystals which are filtered off should melt at about 1 12°.^
The following Table contains a number of determinations carried out
in the author's laboratory : —
Fartty acids from oils.
11
-o
's
o
X
V
X
4>
-a
■§
o
k.
O
'Linseed (iodine value 181)
„ ( „ 184)
„ ( „ 190-4)
,, liquid acids (iodine va
Candle nut
Stiilingia ....
Safflower ....
Soya bean
Rape ....
'Japan fish (old samples) .
(fresh „ ) .
Deodorised fish
Cod liver (Norway) .
„ (Newfoundland)
Shirk liver
Seal
Whale (old samples)
,, (fresh samples)
Sperm ....
ue 208)
Bromides insoluble in
ether.
Per cent.
29-06; 29-34
31-31 ; 30-44; 30-80
38-1; 42-0
34-9
11-53; 11-23; 12-63
25-78
1-65; 0-65
3 to 5
2-4; 3-4
23-04 ; 23-32
44-2; 44-7
38-42; 39-27
29-86; 20-36
39-1 ; 37-76
12-68; 15 08
19-83 ; 19-93
12-38 ; 12-44
22-59; 27-77
2-05
' For further details c/. Lewkowiisch, Chemical Technoloey and Analysis of Oils, Fats, and
Waxes, vol. i., pp. 560 et seq.
UNSAPONIFIABLE MATTER 139
8. Determination of Oxidised Fatty Acids.
The "oxidised" fattv^ acids comprise those acids which are present
in oxidised oils and fats, and which are distinguished from other fatty
acids by their tnsolubiHty in petroleum spirit. They are estimated
as follows by W, Fahrion's method^:— 4-5 g. of an oxidised fat or oil
are saponified in the usual manner with alcoholic potash. The alcohol
is evaporated off, the soap dissolved in hot water, introduced into a
separating funnel, and decomposed by hydrochloric acid. After cooling,
the liquid is shaken with petroleum spirit (boiling below 80°) and then
allowed to stand until it has completely separated into two layers.
The insoluble oxidised fatty acids adhere to the walls of the funnel or
form lumps under the layer of petroleum spirit. The aqueous solution
is drawn off, the petroleum spirit layer decanted, and the oxidised
fatty acids again well shaken with petroleum spirit to wash out all
occluded soluble fatty acids. If the quantity of oxidised acid is
large, it is advisable to dissolve it in potassium hydroxide solution,
decompose the soap again with hydrochloric acid, and shake out as
before with petroleum spirit. The residual oxidised acids are dissolved
in warm alcohol, the solu-tion brought into a tared dish, the alcohol
evaporated off, and the residue dried to constant weight. -
/^.—Examination of Unsaponifiable Matter.
The unsaponifiable matter, which is isolated in substance as
described above (p. 124), can be further examined immediately. If
the samples have not been adulterated with mineral oils, rosin oil, or
tar oil, the quantity of unsaponifiable matter will be very small, as the
unsaponifiable substances which occur naturally in oils and fats amount
generally to less than i per cent. (^ above, p. 124). In waxes, however,
the quantity is much greater — up to 50 per cent. The examination of
the unsaponifiable matter may be divided into : —
I. The examination of those unsaponifiable substances which are
naturally present.
II. The detection and estimation of unsaponifiable substances which
have been added purposely.
I. The Examination of Unsaponifiable Substances
which are Naturally Present.
(a) In Oils and Fats.
The unsaponifiable matter in natural oils and fats contains chiefly
cholesterol or phytosterol, accompanied by small quantities of hydro-
1 Z. angew. Chem., 1898, II, 781 ; 1903, 16, 79, 1 199;/ ^oc. Chem. Ind., 1898, 17, 958 ;
1904. 23, 26.
- For the further examination of these acids, cf. Levvkovvitsch, Chemical Technology and
Atialysis of Oils, Fats, and Waxes, vol. iii., p. 468.
140
OILS, FATS, AND WAXES
carbons, higher aliphatic alcohols, colouring matters, resinous substances,
and albuminous matter. Since, as shown above, "cholesterol" is
characteristic of animal oils and fats, and " phytosterol " (mostly sito-
sterol) is characteristic of vegetable oils and fats, the examination of
the unsaponifiable matter supplies a means of distinguishing between
animal and vegetable products. If the sample consist of a mixture of
animal and vegetable fats, both alcohols will be found in the residue.
X
X
a 7f c d
Fio. 37.— Crystals of Cholesterol.
n A
r d /' f/
Fia. 38.— Crystals of Phytosterol.
For the examination, the unsaponifiable matter is dissolved in the
smallest possible quantity of absolute alcohol,^ and set aside to
crystallise. If only very small quantities of colouring matter and
resinous substances are present, well-formed crystals are generally
obtained ; if this is not the case, the unsaponifiable matter is dissolved
in 95 per cent, alcohol, and the colouring matter removed by treatment
of the hot solution with animal charcoal. The filtrate is then evaporated
Pio. 89.— Crystals from a mixture of Cholesterol and Phytosterol.
to dryness, the residue taken up with absolute alcohol and allowed to
crystallise. The crystals are removed from the mother-liquor and
examined under the microscope. If either cholesterol or sitosterol
(phytosterol) alone is present, it may frequently be recognised by its
characteristic crystalline form, as shown in Figs. 37 and 38. If, however,
' A. Burner, Z. Unters. A'a/ir. it. Genussvi., 1898, 8, S44 ; /• '^'"^- C/iem. hid., 1898,
17. 954-
UNSAPONIFIABLE MATTER 141
cholesterol and sitosterol are present simultaneously, the microscopic
examination yields very uncertain results. A. Bomer showed that mixed
crystals are obtained (Fig. 39), whilst in the author's experience the
crystallisation of mixtures of cholesterol and sitosterol frequently yields
the separate crystals of the two alcohols side by side and not the mixed
forms.^
The uncertainty of the microscopic method of examination is,
however, obviated by the phytosterol acetate test worked out by
Bomer.^ In this test the alcoholic solution containing the crystals
which have separated is evaporated to dryness and heated for a short
time over a small flame in a dish with 2-3 c.c. of acetic anhydride for
each 100 g. of fat, the dish being covered with a watch-glass. The
watch-glass is then removed and the excess of acetic anhydride
evaporated off on the water-bath. The residue is then heated with the
smallest possible quantity of absolute alcohol and set aside to crystallise.
To avoid immediate solidification or crystallisation a few cubic centi-
metres of alcohol are added. The crystallised acetates are collected on
a small filter and washed with 95 per cent, alcohol. They are then
again placed in the dish, dissolved in 5-10 c.c. of absolute alcohol, and
again allowed to crystallise. The crystals are filtered off and their
melting point is determined. As cholesterol acetate melts at ii4°-3-
ii4°-8 (corn), whilst the " phytosterols " obtained from various oils and
fats gives acetates melting between i25°-6 and 137° (corn), it is possible
to draw a preliminary conclusion as to the presence of cholesterol or
phytosterol alone from the melting point of the recrystallised pro-
duct. In cases of doubt it is advisable to repeat the crystallisation
several more times. If the melting point of the fifth crystallisation
is still below 116", the absence of phytosterol may be considered as
established.
For the identification of stigmasterol and brassicasterol, and for
the detection of traces of paraffin wax with which lard, for instance,
may have been adulterated in order to circumvent the phytosterol
acetate test, cf. J. Lewkowitsch, Chemical Technology and Analysis of
Oils, Fats, and Waxes, vol. i., pp. 591 et seq. ; vol. ii., chap, xiv.,
" Lard."
(6) In Waxes.
As the waxes contain considerable quantities of higher alcohols
which prevent a rapid saponification, it is advisable to saponify with
2\N alcoholic potash under pressure, or with sodium ethylate. A
^ Cf. also Lewkowitsch, Chemical Technology and Analysis of Oils, Fals, and Waxes, vol. i.,
P- 584.
'^ Z. Unlers. Nahr. u. Genussm., 1901, 4, 865, 1070 ; 1902, 5, 1018 ; cf also R. H. Kerr,
U.S. Depart, of AgriculL Bureau Animal Chem. Circular 212, loth May 1913 ; J. Soc. Chem. huL,
1913,32, 917-
142 OILS, FATS, AND WAXES
systematic examination of the unsaponifiable matter from waxes is
difficult, and is therefore seldom carried out in commercial anal\'sis.^
The melting point of the unsaponifiable matter ma\' furnish a rough
guide as to the nature of the substances under investigation. The
behaviour towards acetic anhydride permits of definite conclusions as to
the alcoholic or hydrocarbon nature of the substance, and in certain
cases, such as spermaceti, for the identification of the wax. For this
purpose the mixture of unsaponifiable substances is boiled with double
its quantity of acetic anh)'dride for a short time under a reflux condenser.
The appearance of the hot solution is then observed. If all has passed
into solution, aliphatic alcohols or cholesterol and " phytosterol " are
present and have undergone acetylation. If, on the other hand, an
undissolved oil floats on the surface of the hot acetic anhydride solution,
paraffin wax or ceresin is present. The aliphatic alcohols generally
remain dissolved in the acetic anhydride even after cooling. If a mass
of crystals separates out, it may be concluded that cholesterol or " phyto-
sterol" is present, although the presence of higher aliphatic alcohols is
not excluded.
A summary of those characteristics which will prove of assistance in
the examination of the solid unsaponifiable substances is given in the
subjoined Table (p. 143).
2 The Detection and Determination of Admixed
Unsaponifiable Substances.
The presence of admixed unsaponifiable substances in oils and fats
is generally indicated by abnormally low saponification values. Solid
unsaponifiable substances such as paraffin wax and ceresin are identified,
in absence of waxes, by their state of aggregation and melting point.
As a rule, especially in liquid fats, any admixed unsaponifiable matter
consists of liquid substances belonging to one of the three following
groups : —
(a) Mineral oils.
(d) Rosin oils.
(c) Tar oils.
The three classes of oils are scarcely ever present simultaneously.
It is therefore only necessary to consider the possible presence
of mineral oil together with rosin oil, or of rosin oil together with
tar oil.
It should be observed that a certain percentage of mineral oil is not
necessarily to be considered as an adulteration, as it often happens (as
for instance in burning oils or lubricating oils) that mineral oil is
legitimately added to fatty oils. To ascertain more closely the nature
^ For further details, c/. Lewkowilsch, Chemical Technology and Analysis of Oils ^ fals, and
Waxes, vol. i., chap. ix.
UNSAPONIFIABLE SUBSTANCES
143
u
(0
0)
■M
U
n{
u
rt
x:
U
0)
Xi
c
tfl
0)
a
c
to
XJ
3
CO
3
■ «-«
C
o
a
nJ
(/)
G
a
o
Increase of weight on
boiling with ai'etic
anhydride.*
2
g (N>ncp?oo50ia505 c^oo •" .'P
"Ot-_vni-(Oioooo3 ;oo ••" :io»->
^ i-Hi— lr-( r-Hf-*T-H "f— IF— 1 t>, '"'05
0 <»
•
CD
<
a
o
P.
tc
a
°c.
22 to 23
31
65
70
114
under 100
125-6 to 137
141
o
U
c
o
o<
ee
m
0 ^2
•t^O(NCD>-i>-'r-io2'f'^0.- :^CO
•0500CO.— COCOCOtMOCOvn-, "OOIM
r— If— If— <f— (r- II— ti-Hi— II— li— (r— r— <i< r-(F— <
CO 2
F-( ""^
0
c»
<D 2
'v. £*
° o
.D
^ L/ CO OO * CO ,„ . . .
^oooo^;^^go ;^ : i2 : i
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CO 'i'
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C
'o
_C
"3
38 to 82
50
59
79
85
148-5
137 to 138
137 ., 138
170
25-5 to 27-5
88 „ 90
44-4 „ 48-9
75 to 76 ; 65 to 66-1
49-5 to 59-2
46-7 ■
78
c
oroooooo
: X E ffi K K E s: ffi "• ■ ■ ^- ■-•
00000000
1
Paraffin wax, ceresin
Cetyl alcohol . . . .
Octodecyi alcohol
Ccryl alcohol
Melissyl (myricyl) alcohol .
Cholesterol
Isocholesterol
Phytosterol, sitosterol
Stigmasterol
Alcohols from sperm oil
„ carnaiiba wax
,, wool wax .
,, crude wool wax
,, beeswax
Hydrocarbons from beeswax
Alcohols from spermaceti .
,, insect wax .
D ":!.
a ^.
O to
to tfi
Q 3 r:;
O .— tr
rt ^- 0:1
-" *" o
»-. .0
5.$.%
u
T)
c
3
ri
V*
>
C3
to
C
0
o3
3
if
-?>
w
m
0
m
A
.5 3
tj -*^
.2 -
o ^
c *
• .2 5
"" 3 .a
(» ;3 ^
^ a -
g g o
. ««
o .S
•a
c
. 3
O 3
o
3
c
a;
c4
o
13
.2
s
3
S 2
^ 3
*-. ■" . rt
O - « uj
m J" 9 .3
= S •* >.
c3 - c -O
3 -a
o 2 fi
^ C i-i
^5 ^
1 g s 1
Hi OILS, FATS, AND WAXES
of the isolated unsaponifiable oil, a quantity sufficient for the examina-
tion is prepared, and the specific gravity is first determined. As the
mineral oils in question have a sp. gr. of 0-84-0-92, and the
rosin oils 0-96- i-oi, whilst the tar oils have a gravity over i-oi, the
specific gravity may give useful indications, if only one oil is present.
If a mixture of mineral oil and rosin oil is present, the Liebermann-
Storch reaction is the best test for the qualitative detection of rosin oil.
In this test, 1-2 c.c. of the unsaponifiable oil are gently warmed
v.'ith acetic anhydride in a test tube and shaken. After cooling, the
bottom layer is removed by means of a finch- drawn out pipette, and
the solution tested as described above (p. 130). In presence of rosin
oil a beautiful violet fugitive colour is obtained. It must not be
forgotten that cholesterol gives a similar colour reaction. The presence
of rosin oil may also be ascertained by the determination of the optical
rotation, as mineral oils rotate the plane of polarised light but little,
whereas rosin oils show a marked optical activity. (It must not,
however, be overlooked that the hydrocarbons obtained from the dis-
tillation of wool fat arc also optically active, as first shown by the
author.)
The quantitative determination of rosin oil in mineral oil is best
effected by Valenta's method : — 10 c.c. of glacial acetic acid dissolve
at 50", 0-2833-0-6849 g. or 2-6-6-5 per cent, of mineral oil as compared
with 1-7788 g. or 16-9 per cent, of rosin oil. For the determination, 2 c.c.
of the unsaponifiable oil are mixed with 10 c.c. of glacial acetic acid in a
test tube, which is then loosely corked and heated for five minutes in a
water-bath with frequent shaking. The solution is then filtered through
a moistened filter paper, and the middle portion of the filtrate collected.
A weighed quantity of this is titrated to determine the acetic acid.
The difference between the percentage of acid found and that originally
taken gives the quantity of undissolved oil.^
If the sample consists of a mixture of mineral oil and tar oil, the
presence of the latter is detected by treatment with nitric acid of sp.
gr. 1-45. Tar oils cause a considerable rise of temperature, whereas
mineral oils become only slightly warmer.
For details of Valenta's proposal to treat the unsaponifiable oils
with dimethyl sulphate, cf. J. Lewkowitsch, Chemical Technology and
Analysis of Oils, Fats, a7id Waxes, vol. i., p. 61 1.
With the aid of the subjoined Tables 25-27, which are arranged as
far as feasible according to a natural system, it will not be difficult to
identify a sample of oil, fat, or wax, when the above described methods
have been applied. More complete Tables are given in the author's
Laboratory Companion to Fats and Oils Industries. A series of examples
> Cf. Lewkowitsch, Chemical Technology ami Analyns of Oils, Fats, ami Waxes, vol, iii.,
chap. XV.
UNSAPONIFIABLE SUBSTANCES 145
which may serve as a guide to the investigation of more complex
problems, are given in vol i., chap, xi., of the author's Chemical Technology
and Analysis of Oils, Fats, and Waxes. The special methods described
in the following Section should also be consulted.
Literature.
Lewkowitsch, J. — Chemical Technology and Analysis of Oils, Fats, and Waxes,
Vol. I., 5th edition, 1913 ; Vols. II. and III., 4th edition, 1909.
Lewkowitsch, J. — The Laboratory Companion to Fats and Oils Industries, 1901.
[Tables 25, 26, 27.
HI K
146
OILS, FATS, AND WAXES
Table 25— Data for the Identification
OILS.
Characteristics.
Sp. gr.
0.
c
I
V
3t
3
"3
a
•5
^=1
c 00 tf
1-35
°C.
•c.
'C.
KOH.
mg.
Per cent.
A-/IO KOH.
c.c.
Per
cent.
Vegetable
Drying.
Linseed
15
0-9315-0-9345
-27
-20
192-195
171-201
* • •
95-5
Tung oil, Chinese^
(Japanese) wood* J
Candle nut
15
15-5
0-9360-0-9432
0-9256
below - 17
liq. at
-18
193
192-6
150-165
163-7
...
92-2
95-5
Hemp seed
Walnut
Safflower .
Poppy seed
Sunflower .
15
15
15-5
15
15
0-9255-09280
0 9250-0-9260
0-9251-0-9280
0-9240-0 9270
0 9240-0-9258
-27
-27-5
-18
- 18-5
192-5
195
186-6-193-3
195
193-5
148
145
129-8-149-9
133-143
119-135
1-54 (R.-M.)
0
95-4
95-37
95-2
95
Semi-Drying.
Cotton seed group —
Soja bean
Cameline (German "\
Sesame) . J
Pumpkin seed .
Maize
15
15
15
15-5
0-9242-0-9270
0-9200-0 9260
09237
0-9213-09255
-8
-18
-15-5
-10 to -20
...
192-7
188
188-4
188-193
137-140
135-142
123-130
113-125
4-5 (R.-M.)
95-5
96-2
■ 93-96
Kapok
Cotton seed
18
15
0-9199
0-9220-0-9250
...
3-4
181
193-195
116
108-110
...
94-9
95-96
Sesame
15
0-9230-0 9237
-5
...
189-193
103-108
1-2 (R.-M.)
95-7
Beech nut
Brazil nut
Curcas
15
15
15-5
0-9200-0-9225
0 9180-0 9185
0-9204
-17
0-4
-8
...
191-196
193-4
193-2
104-111
106-2
98-110
0-5 (R.-M.)
95-2
95 "3
Croton
Rape group — Ravison .
Hedge mustard
Rape (Colza) .
Black mustard seed .
15
15-5
15
15-5
15
0-9500
0-9183-0-9217
09175
0-9132-0-9168
0-916-0-920
-16
-8
-8
-2 to -10
-17
\
210-215
174-179
174
170-179
174
102-104
101-122
105
94-102
96-110
12-13-6
(R.-M.)
6-3
89-0
95-1
95-1
White mustard seed .
Radish seed
Jamba
15-5
15
15
0-914-0 916
0-9175
0-9154
-8 to -16
-10 to
-17-5
-lOto-12
...
170-174
173-178
172-3
92-97
93-96
95-4
0-33 (R.-M.)
96-2
95-9
No\-Drying.
A Imond group —
Cherry kernel .
Apricot kernel .
Plum kernel .
15
15-5
15
0 9234
0-9195
0-9160-0-9195
-19 to -20
-14
- 5 to - 6
...
193-195
192-.-.
191-5
110-114
96-108
93-3-100-3
0
95-4
Peach kernel .
15
0-918-09215
below -20
...
192-5
93-109
...
...
Almond .
15
0 9175-0-9195
-10 to -20
191
93-97
...
962
* To be separated on the basis of the specilic gravities. Cf. Lewkowitsch»
VEGETABLE OILS
147
of Vegetable Oils and of Animal Oils.
Variables.
Characteristics of fatty acids.
Refractive
index.
>
<
1
"3
>
S
<
>
■<
_2
a .
§•3
a
t3
Sp. gr.
1.3
•a 3
+3
a
0
P.
to
a
1
0
■is
f'
0
3
■3
>
1
0
>
Butyio-
refracto-
meter.
"c.
Scale
divisions.
KOH.
mg.
Per cent.
"C.
0 r, Titre.
C. OQ
°C.
KOH.
mg.
Total
fatty
acids.
Liquid
fatty
acids.
°c
Oils.
20
84-90
3-98
0-8-8-4
0 •42-1-1
15-5
0-9233
13-17
19-4 to
17-21
197
179-182
190-201
60
1-4546
40
72-5
...
20-6
...
...
...
7-6-12
0-44
...
...
31; 34
37-2
31;
43-8
188-8
144-159
...
...
15
76
9-86
8-1
0-76
1-08
*.•
• ■>
13
15
16-6
20-21
18-19
. . .
141
...
...
...
40
64 -8
...
...
• . .
• • •
. • •
•..
16
• . .
16-18
**•
150
167
...
...
40
65-2
16-1
0-33-20
. • •
...
• ■ •
...
• • •
. . •
40
63-4
• • •
• • •
0-7-11
0-43 '
ibo
0-8886
16-5
16-2
20-5
199
139
15b
60
1-4506
25
72-2
...
11-2
4-5
0-31
0-22
...
...
18
24
14-13
...
22-24
28
18-20
201-6
124-134
119
136-8
154-3
165-4
60
1-4531
25
70-2-72-5
24-5
28-29
197
7-5 to
1-7-20-6
1 •35-2-86
...
16-14
18-20
198-4
119-5
140-144
...
...
8-75
0-9162
24-23
29
191
108
25
67-6-69-4
7-6 to
18
0
0-73-i-64
15-5
0-9206 to
0-9219
32-35
32-35
35-38
202-208
111-115
147-151
60
1-4*460
25
68
...
0-23 to
66(0
0-95-1-32
...
23-5
17
22-9 to
23-8
26-32
23-24
200-4
110-45
114
129-136
60
1-4461
■ ••
...
...
...
...
32-25
29
• . •
108
...
. • *
• •■
25
65
7-5
0-7-8-5
0-5-0-58
...
26-5to
28
27-5 to
105-1
■ . •
, ,
• <M
40
56-5
25-7
30-5
27
77-5
19-32
...
0-55
...
16-7
19
...
201
111-5
...
...
...
20
73-74
4-8-12
1-45-1-66
100
0-8802
...
124-2
25
70-5-71 -5
...
...
...
...
...
...
> ■ .
. . *
• ••
25
68
14-7
1-4-13-2
0-58-1
ioo
0-8758
16
12-13
16-19
185
99-103
121-125
60
1-4991
40
59-5
...
1-36 to
7-35
...
...
...
15-5
...
16
...
109-6
...
...
40
58-5
5-4
...
...
...
. . .
. t .
15-16
• . *
95-3
. . .
40
57-5
...
14-5
...
...
• ••
15-13
16-11
15-13
...
20
19-21
19-21
173-9
189
97-1
96-1
109
124-7
...
25
66-6
...
...
o"64
0-55
...
...
...
0
15-13
..•
3-4
20-22
3-5
194
200-5
103
103 (!)
111-5
98-6
...
...
25
66-1-67-2
...
...
...
...
...
...
...
13 to
13-5
10-18
200-9
94-101
101-9
...
25
64-4
1-5
5
10-1 to 13-14
204
93-96-5
101-7
60
1-4461
11-8
Chemical Technology and Analysis of Oils, Fals, and Waxes, vol. ii., p. 03.
148
OILS, FATS, AND WAXES
Table
Cha
racteristics.
it!
a
5
3
ally
tor.
o
d .
^-^ <L/ : .
\~ d *^
OILS.
Sp. gr.
1'^
c
a
%
- a
c >
a
X!
>
a
'i
-5a « >
s, X ce
°C.
'C.
"C.
KOH.
mg.
Per cent.
N/IO KOH.
c.c.
Per
cent.
Vegetable
Non-Drying (coni.).
Olive group — Arachis'^
15
0-9170-0-9209
- 3 toO
0
190-196
83-100
...
95-8
(earth nut) . /
Hazel nut
15
0-9146-0-9170
-17
192
83-90
0-99 (R.-M.)
95-6
Olive
15
0-916-0-918
-6 to 2
185-196
79-88
0-3
95
Olive kernel .
15
0-9184-0-9191
183
87-4
Ben ....
15
0-9120-0-9198
"6"
82
Castor group —
Grape seed
15
0-935
-lOto -13
178-5
96
0-46 (R.-M.)
92-13
Castor
15'5
0-9600-0-9679
-lOto - 18
183-186
83-86
1-4
Animal
Marine Animals.
/^?5/2 —Menhaden
15-5
0-927-0-933
-4
...
190-6
139-173
1-2
Sardine .
15
09330
...
...
161-193
94-5
Japanese sardine \
(Japanese fish oil) J
15
0-9160
...
20 to
189-8-192-1
100-164
96-97
22
Herring .
15-5
0-9202-0-939
...
171-194
123-.0-142
95-64
Stickleback
• • *
...
...
162-0
95-78
Sturgeon .
15
0-9236
...
186-3
125-3
Sprat
15-5
0-9284
Liver — Cod
15
0-9210-0-9270
0 to"'-10
171-6-189
167
95-3
Haddock .
15
0-9298
188-8
154-2
93-3
Skate
15
0-9307
• > •
185-4
157-3
94-7
Tunny
. . •
• • ■
...
155-9
95-79
Shark (Arctic) .
15
0-9163
• ••
161-0
114-6
86-9
Coal fish .
15
0-925
177-181
137-162
...
Hake .
15-5
0-9270
Ray.
15-5
0-9280
Ling
15
0-9200
...
184-1
132-6
Blubber— ^tzX .
15
0-9155-0-9263
- 2 to - 3
189-196
127-141
0 07-0-22
95-45
Whale .
15-5
0-9250
below -2
188-0
121-136
0-7-2-04
93-5
Dolphin (body)
15
0-9180
below - 3
197-3
99-5
5-6
93-07
Dolphin (jaw) .
• • •
• • •
290
32-8
65-92
66-28
Porpoise (body)
15
0-9258
-16
195
...
23-5
Porpoise (jaw)
15
0-9258
...
254-272
22-50
47-77-65-8
70*23
Land Animals.
Sheep's foot
15
0-9175
0 to - 15
194-7
74-2
Horse's f ^ot
If,
0-91 3-0-927
• • •
195-9
73-8-90
Neat's foot
1 .
0-9H-0-916
0 to - 15
...
194-3
69-3-70-4
...
...
Egg .
1.')
09144
8 to -10
22-25
184-4-190-2
68-5-81-6
0-4-0-7
(R.-M.)
95-16
VEGETABLE AND ANIMAL OILS
149
25 — cofttinued.
Variables.
Characteristics of fatty acids.
Refractive
0)
•+J
a
index.
0?
■3
0
"3
0
3
>
■0
a
Sp. gr.
be
hi
-So
'0
Qt
bO
a
^3
*3 >
>
a
?
Butyro-
refracto-
meter.
3
0
<
eg
■3
^
^
•a
0
l-H
PS
•0.
Scale
divisions.
<
<
KOH.
mg.
Percent.
°C.
°C.
Titre.
'C.
°c.
KOH.
mg.
Total
fatty
acids.
Liquid
fatty
acids.
'C.
Oils — con tin ued.
25
66-67-5
...
3-2
1-2 to
32(!)
0-54-0-94
0-5
100
0-8790
26
19-20
29-2
27-7 to
32
22-24
201-6
200-6
96-103
90-3
105-128
91-3 to
97-6
60
1-4461
25
62-4
...
10-64
1-9-50
2-3-5
0-46-1
100
0-8749
22-17
17-2 to
26-4
24-27
193
86-90
95-5 to
103-5
60
1-4410
16-2
-
20-18
24
187-4
99
25
78
146-7
to
150
• ' '
0-14 to
14-61
. . *
15-5
0-9509
3
•" •
13
192-1
87-93
106-9
60
1-4546
Oils.
11-6
1-6-2-2
...
...
13-0
4-21
10-35
1-8-44
21
0-52-0-86
0-48-2-6
0-99-10-7
1-73
...
...
...
28-2
...
178-5
181-5
...
...
...
25
75
...
4-8
10 -6
li-'g
1-25
0-2-34
1-26 to
0-54-7-83
1-1
0-97
1-0-1-8
10-2
...
...
18-4 to
24-3
2i-25
204-207
177-0
130-5 to
170
60
1-4521
...
...
...
...
16-5
1-68
11 -0
1-9-40
2-23
0-38-1-4
...
...
...
15-5 to
15-9
22-23
...
193-2
...
25
70
1
1
1
...
13-b
22-0
0-5-37
5-0
0-92-3-72
3-7
16-4
100
0-8922
...
23-9
21-1
2-86
26-1 to
26-5
27-0
...
...
29-8 to
30-8
...
131-2
61 -98 to
63-26
144-7
25
68-5
...
1-2
1-7
...
...
...
...
34-39
194-9
72-9
...
...
...
150
OILS, FATS, AND WAXES
Table 26. — Data for the Identification
Characteristics.
4^
a
1
6
_3
• 1
FATS.'
3p.gr.
C
43
1>
C3
>
C
i >: ea
2 = a
s
CJ
s
1"
1
-5 fc,'5
1 11 so
acids
flab
°C.
"C.
°c.
KOH.
mg.
Per cent.
.Y/10 KOH.
CO.
Per
cent.
Vegetable.
Laurel oil group —
Laurel oil
15
0-9332
25
32-34
197-9
68-80
1-6
. . .
Mahua butter .
100
(100 = 1)
0-8981
19-22
28-31
190-194
53-67
0-5-0-9
(R.-M.)
94-82
Mowrah seed oil
15
0-9175
36
42
188-192
50-62
94-76
Macassar oil .
15
0-9240
10
22
221-5
48-55
91-5
Shea butter (Galam^
15
0-9175
17-18
25-3
179-192
56-6
94-76
butter) . . /
Palm oil .
15
0-921-0 -9245
...
27-42-5
196-202
51-5
0-5
94-97
Nutmeg butter .
15
0-945-0-996
41-42
38-51
154-191
40-52
(50-81)
1-4-2
(R.-M.)
...
Cocoa group — Mkanyi .
15
0-9298
38
40-41
190-5
41-9
1-21
(R.-M.)
95-65
Malabar tallow
15
0-9150
30-5
36-5
188-7-192
38-2
0-2 to
0-44
(R.-M.)
Cocoa butter .
15
0-9500-0-976
23-21-5
28-33
193-55
32-41
0-2-0-8
(R.-M.)
94-59
Chinese vegetable^
15
0-9180
27-31
36-46
200-3
28-37
.»
"...
tallow . . /
Kokum butter (Goa\
butter). . J
40
0-8952
37-6 to
41-42
187-191
33-6
0-1-1-5
95-1
(15 = 1)
37-9
(R.-M.)
1
Borneo tallow .
...
...
...
35-42
...
(31 ?)
...
...
Cocoa nut oil group —
Mocaya oil
22
24-29
240-6
24-63
7-0 (R.-M.)
Maripa
100
(15-5 = 1)
0-8686
24-25
26-5 to
27-0
270-5
17-35
4-45
(R.-M.)
88-88
Palm seed oil .
15
(15-5 = 1)
0-9520
20-5
23-28
242- -250
13-14
5-6 (R.-M.)
87-6 to
91-1
Cocoa nut oil • it .
40
(15-5 = 1)
0-9115
22-14
21-24
246-260
8-9-5
7-8-4
(R.-M.)
88-6-90
Myrtle wax
15
0-995
39-43
40-44
208-7
10-7
Japan wax .
15
0-9700-0-980
48-5-53
50-54
217-237-5
4-9-8-5
...
90-6
Dika oil (oba oil, wild)
...
0-8200
34-8
41-6
. . •
31-1
mango oil) , /
Animal.
Drying — Polar bear .
15
0-9256
. . .
187-9
147
...
Semi-drying —
Black cock
15
0-9296
...
...
201-6
121-1
2-1
...
Hare
15
0-9349
17-23
35-40
200-9
102-2
1-59
95-4
Rabbit (wild) .
15
0-9393
17-22
35-38
199-3
99-8
0-7
...
„ (tame) .
15
0-9342
22-24
40-42
202-6
67-6
2-8
95-5
Wild duck
...
15-20
• • <
198-5
84-6
1-3
• •■
Tame duck
, , ,
22-24
36-39
58-5
Horse
15
0-9189
43-30
34-54
195-197
71-86
0-2-0-4
95-96
For subsidiary groups, cj. J. Lewkowitsch, BiM. Sac. Chim., 1909, 42. (Conference : Fatty Compounds.)
VEGETABLE AND ANIMAL FATS
151
of Vegetable and Animal Fats.
Variables.
Refractive
index.
Butyro-
refracto-
meter.
'C.
40
40
Scale
divisions.
52-1
lfi:
48-85
40 46-47-8
25
40
40
1-4628
36-5
-r34
18
2-8
>
'3
<
a
KOH.
mg.
Per
cent.
Characteristics of fatty acids.
Sp. gr.
°C.
26-3
34-56
6-2 to
35-4
29-4
24-200
17-44-8
23-3
38
1-1 to
1-88
2-2-7-5
21
20
1-9 to
8-4
0-9 to
12-3
27 to
31-2
40
40
40
49
49
53-7
8-36
5-50
3-4-4
7-33
19-6
3-12
3-5
5-9
2-73
7-2
6-2
1-5
0-2-44
100
0-8701
1-lto
1-63
100
(15-5=^1)
98-99
(15 -5 ---1)
98-99
(15-5 = 1)
0-8230
0-8354
0-8480
~ o
o
38-40
38
40
57-5
54-8
47-45
59-4
53-5 to
54
22-20
25
20-16
46
53-0 to
56-5
15
15
15
15
Titre.
'C.
15-1
a
40-3 45
51-6 to 52-55
53-2
53-8
35-910
45-5
35-9
61-5
48-3
45 -2 to
53-5
58
47-50
42-5
59 to
61-5
56-6
48-50
53-57
60-61
a
o
Mi
"A
KOH.
mg.
191-6
205-6
Total
fatty
acids.
23-25
... '27-5to
28-5
20-5 to 25 to
25-5
22-5 to
25-2
59-4
0-9374
0-9361
0-9246
0-9264
25-28
36-40
35-36
37-39
30-31
37-7
28-5
25-27
47-5
56-62
190
182-208
198-9
254
258-264
258-266
230-9
213-7
30-33
44-47
39-41
40-42
36-40
199-3
209
209-5
218-1
33-7 37 -5 to 202-6
39-5
81-8
56-6
50-58
56-57-2
63-3
42-1
33-39
30-39
Liquid
fatty
acids.
103-2
94-6
12-15
12-0
8-4-9-3
120
93-3
101-1
64-4
84-87
18-6
60
60
60
1-422
1-4310
1-4295
40
40
But'r. refr-
36
But'r. refr.
36
152
OILS, FATS, AND WAXES
Table
FATS.
Characteristics.
Sp.gT.
If
a
"3
c.
to
B.
■^
a
o
ll
|5
C
•n
6
a
a
o
v u Z
ps
■- =3 -J
C, i C3
S 3 =
.= + =
Ui
-c.
°C.
'C.
KOH.
mg.
Per cent.
A'AO KOH.
c.c.
Per
cent.
Animal {cont.).
Non -dry inf; —
Horse marrow .
Goose (domestic)
Wild goose
Lard
Wild boar
Beef marrow .
Bone
Beef tallow
Mutton tallow .
Butter
Stag
15
15
15
15
15
15
15
15
15
15
15
0-9204-0-9221
0-9274
0-9158
0-934-0-938
0-9424
0-9311-0-9380
0-914-0-916
0-943-0-952
0-937-0-953
0-926-0-940
0-9670
24-20
18-20
18-20
27-1 to
29-9
22-23
31-29
15-17
35-27
36-41
20-23
39-48
35-39
32-34
36-40-5
40-44
37-45
21-22
45-40
44-45
28-33
49-52
199-8
193-1
196
195-4
195-1
199
190-9
193-2-200
192-195-2
227
199-9
79-1
67-71
99-6
50-70
76-6
55-4
46-55-8
38-46
35-46
26-38
20-5-25-7
1
0-98
0-2-0-3
(R.-M.)
0-68
1-1
0-25
12-5-15-2
1-66
95
93-96
95-6
95-5
86-5 to
89-8
Table 27. — Data for the
Characteristics.
s
...
c
t
_o
a
■3
t(R.
hert
t.-M
e.
waxks.
Sp. gr.
■So
s
05
0
= A
0 >
^
•3=J ? >
eg
~3
0
2 t:'s
"0.
°c.
°c.
KOH.
Percent.
A'/IO KOH.
mg.
c.c.
Liquid —
Sperm oil .
15
0-8799-0-8835
...
...
125-2-132-6
81-90
1-3
Bottlenose oil .
15
0-8764
123-135-9
67-82-1
1-4
Vegetable —
Carnaiiba .
15
0-990-0-999
80-81
85-86
79-95
13-5
Animal —
Wool (wool fat)
17
0-9413-0-9449
30-30-2
31-35
102-4
17-1-28-9
Bees.
15
0-964-0-970
60-5-62-8
61-5-64-4
90-98
7-9-11
0-34-0-54
Spermaceti
15
0-90r.-0-960
42-47
42-i9
123-135
Insect (Chinese)
15
0-926-0-970
80-5-81
80-5-83
80-5-93
...
...
VEGETABLE AND ANIMAL FATS. WAXES
153
26 — continued.
Variables.
Characteristics of fatty acidi).
Refractive
index.
3
05
bO
a
'0
.2
a
<o
.
"5
.^fe
Ba
0.
2 3
C"
s A
3
§"S
Sp.
gr-
to
'3'c3
a
Sg
Butyro-
«
0.5
^
i^>
refracto-
<
tn
03
©
a
->
tf
meter.
<
H)
a
i5
^0,
Scale
KOH.
ivr
°C.
°C.
Titre.
°c.
KOII.
Total
fatty
Liquid
fatty
0
divisions.
mg.
cent.
u.
nig.
acids.
acids.
...
...
1
15
0-9182to
0-9289
36-34
• . .
42-44
210-8to
217-6
71 -8 to
72-2
...
40
50-50-5
0-59
15
0-9257
31-32
• • •
38-40
202-4
65-3
. . .
...
...
...
...
0-86
15
0-9251
33-34
...
34-40
196-4
65-1
[
92 -i*
60
l-i395
40
48-6 to
51-2
2-6
...
0-54 to
1-28
2-6
0-23
99
15
0-8445
0-9333
39
32-5 to
33-5
41-42
43-44
39-40
201-8
203-6
64 \
81-2
90-1 06t
22
Oil refr.
-30
...
4-2
1-6
...
15
0-9300 to
0-9399
37-9 to
38
44-46
204-5
55-5
...
...
...
...
11-3
29-6-53
0-5 to
1-8
•
...
28
...
30
200
55-7 to
57-4
...
...
...
40
49
2-7to
8-6
3-5-50
100
(100^1)
0-8698
...
37-9to
46-2
43-44
197-2
41-3
92-4
60
1-4375
...
...
...
1-7-14
...
...
...
41
40-15
to 48-2
49-50
210
34-8
92-7
60
1-4374
40
41-42
1-9 to
8'6
0-45 to
35-38
...
37-75
a5-5 = l)
0-9075
33-38
...
38-40
210-220
28-31
...
60
1-437
40
44-5
...
3-5
...
15
0-9685
46-48
50-52
201-3
23-6
...
...
* European lard.
t American lard.
Variables.
Characteristics of fatty acids.
Refractive index.
a
>
0
<
Acid value.
Fatly acids.
Sp. gr.
Solidifying
poiut.
so
a
4^
t-l
a
"3
0
"o
s
5
3
■3
2
0
Butyro-
refractometer.
'C.
Scale
divisions.
KOH.
mg.
Per
cent.
°C.
^C.
Titre.
°C.
'C.
Per cent.
40
46-2
4-5-6-4
60-64
15-5
0-899
16-1
11-1-11-9
13-3
281-294
83-2-85-6
...
4-1-6-4
...
61-65
...
...
10
8-3-8-6
10-3-10-8
...
82-7
...
• •«
55-24
4-7
...
...
...
...
...
...
23-3
59-8
40
41-8
327-5
17
62
29-5-30
15-24
2-63
16-8-21-2
...
...
...
...
...
...
...
SPECIAL METHODS OF ANALYSIS EMPLOYED
IX THE OIL AND FAT INDUSTRIES
By the late J. Lewkowitsch, M..\,, Ph.D. English translation
revised by the Author.
A.— OIL SEED, OIL CAKES, CRUDE FATS, ETC.
The raw materials of the oil and fat industries in which the content of
fat is to be determined are subdivided as finely as possible, and
extracted with ether, petroleum spirit, or other such solvents. The dis-
integration of the hard oil seeds may be effected by pounding in a
porcelain mortar ; in this case, it is necessary to rinse out the mortar
with the solvent to avoid losing any fat which has been pressed out.
Oil seeds may also be ground in an ordinary coffee mill, but in this case
it is impossible to avoid loss of oil. M. Lehmann ^ has constructed a
grinding mill of such small dimensions that
->,^ after grinding the sample the whole mill may
/ \ be put into the extractor, together with the
ground material. If the substances contain
a considerable amount of moisture, the
sample should be dried in an air-oven previ-
ously to extraction, provided that this can be
done without detriment to the fat ; but if any
oxidation or loss of volatile ingredients be
feared, the complete extraction of moist sub-
stances is effected by using petroleum spirit
(boiling completely below So"). Ethyl ether,
carbon bisulphide, or chloroform maybe u.sed
only for dry substances. The choice of solvent is not always im-
material ; carbon bisulphide, as a rule, extracts more foreign matter
than either ether or petroleum spirit.
Of the numerous forms of extraction apparatus that have been
proposed, that of Soxhlet (Fig. 40) is the most generally employed. A
wei-T-hed quantity (20-50 g.) of substance is introduced into a " thimble "
of filter paper (either bought ready-made or prepared by rolling filter
paper round a cylindrical piece of wood). The tube B is then attached
to a flask of 100-200 c.c. capacity, and the solvent added at A, until it
1 C/iem. Zei/., 1 894, 18, 412.
154
V^"
Fig. 40.
OIL SEED, OIL CAKES, CRUDE FATS, ETC. 155
overflows the syphon. After adding a little more solvent, A is attached
to a reflux condenser and the flask heated on a water-bath.
In using this form of extractor, it is always a matter of doubt when
the extraction is complete, and it is therefore generally carried on
longer than is necessary, with consequent loss of time and solvent.
For this reason a modified form of Soxhlet's apparatus proposed by the
author,^ and shown in Fig. 41, may be used with advantage ; after
certain intervals of time a sample is drawn off into a watch-glass, and
evaporated down to see if any residue of fat remains.
When the extraction is complete, the heating is discontinued, the
solvent distilled off, and the residue weighed. As ethyl ether extracts
from moist substances not only considerable quantities of water but also
non-fatty substances, it is advisable, when using ether, to take up the
residual fat with petroleum spirit, after distilling off the ether.
The drying may be done by laying the flask in a drying oven heated
to 100''- 105^, and turning it round occasionally. When all droplets of
water have disappeared, the drying may be considered complete. As a
check, the substance is dried for another half an hour, and weighed
again. In the case of drying oils, the flask is heated to ioo°-i05° in an
oil-bath, and a slow current of carbon dioxide or hydrogen is passed
over the heated fat. The nature of the extracted fat is determined by
the methods described in the foregoing Section on " Oils, Fats, and
Waxes." In the case of oil seeds and oil cakes, a careful microscopic
examination gives useful information as to their source, purity, etc. For
further details of this subject, special treatises must be consulted, such
as J. Konig's Untersuchung landwirtscJiaftlicJi und gewerblicJi wichtiger
Stoffe, pp. 244 and 278.
^.—EDIBLE OILS AND FATS.
The examination of these products is carried out by the methods
described in the previous Section. Most frequently it is required to
detect cotton-seed oil, sesame oil, and arachis oil in table oils, sold
under the name of olive oil. The determination of the acid value is of
importance, although it is not always safe to condemn a sample, the
acid value of which is somewhat high (over 2), on this test alone. The
taste is rather to be regarded as the determining factor. This Section
is restricted to the examination of the following- edible fats : —
't>
I. Butter.
The methods of examination to be described are concerned only
with butter fat. The butter fat is prepared by melting the sample
and pouring off the clear molten fat through a dry pleated filter.
1 J. Chem. Soc.^ 1889, 55, 359.
156
ANALYSIS IN OIL AND FAT INDUSTRIES
The refractive index serves as a preliminary test {cf. p. 109). The
determination of the Reichert-WoHny value (p. 119) is of importance,
and should exceed 24 in a "normal" butter. If a lower value be
obtained, adulteration with other animal fats or vegetable fats may be
suspected, except in the case of " abnormal " butters. The former are
introduced into butter mostly in the form of margarine. If the
margarines contain sesame oil, prescribed by law in some continental
countries, indications of its presence are obtained by a positive result of
the Baudouin reaction (p. 129); if this is not the case, the saponification
value, specific gravity, etc, and other characteristics (see preceding
Section) must be determined,^ and as margarines contain, as a rule,
vegetable fats, the phytosteryl acetate test should be applied.
With the aid of this test the presence of vegetable fats is most
rapidly ascertained. The detection of small quantities of cocoa-nut
oil in butter fat is of importance. For this
purpose E. Polenske's method- is the most
applicable ; in the absence of better methods,
this may be regarded as supplementary to the
ph)'tosteryl acetate test.
To carr)' out the test, 5 g. of filtered butter
fat are saponified by heating in a 300 c.c. flask
over a free flame with 20 g. of gh-cerol and
2 c.c. of a solution of sodium hydroxide in an
equal quantity of water (Leffmann and Beam's
process). The solution is allowed to cool below
100'', 90 c.c. of water added, and the soap
brought into solution by warming on a water-
bath to about 50 . The solution should be
clear and almost colourless. If a brown solu-
tion has been obtained, the test must be
rejected. Then 50 c.c. of dilute sulphuric acid
(25 c.c. pure concentrated sulphuric acid in
1000 c.c. water) is added to the hot solution,
together with some poivdered pumice. The flask is then attached
immediately to a condenser. The apparatus used must correspond
precisely in all details with the dimensions given in Fig. 42. The
heating must be so regulated that 1 10 c.c. distil over in nineteen to
twenty minutes. The flow of condenser water is regulated so that the
distillate is collected in the 1 10 c.c. flask at a temperature not exceeding
20°-23''. As soon as 1 10 c.c. have distilled over, the 1 10 c.c. flask is
removed and replaced by a measuring cylinder of 20 c.c. capacity.
^ Cf. Lewkowilsch, Chemical Technology and Analysis of Oils, Fats, and Waxes, vol. ii., p. 667.
- Arbeiten atis. d, Kaiserl, Gesundheitsamt, 1904, p. 543 ; cf. also R. R. Tallock and R. T.
Thomson, y. Soc. Chetn. Iiid., 1909, 28, 69.
Fig. 42.
BUTTER 157
The distillate must not be shaken. The flask is immersed almost
completely in water at 15°; after about five minutes, the neck of the
flask is gently tapped, so that the drops of oil floating on the surface
attach themselves to the walls of the flask. After a further lapse of ten
minutes, the consistency of the insoluble acids is observed, to see whether
they form a solid or semi-solid mass or oily drops. The contents of
the flask are then well mixed up, by inverting the closed flask four or
five times, without, however, shaking it vigorously. Then 100 c.c. are
filtered off through a filter paper of 8 cm. diameter, and titrated with
A710 alkali exactly as in the Reichert process (p. 119). In order
to remove the soluble acid completely, the filter is washed three times
successively with 1 5 c.c. of water, which have been passed severally
through the condenser tube, then into the 20 c.c. measuring cylinder,
and finally into the no c.c. flask. The condenser tube, measuring
cylinder, and 1 10 c.c. flask are then rinsed out in the same manner
with three successive washings of 15 c.c. of neutralised 90 per cent,
alcohol, each washing being allowed to drain off completely before the
next is brought on to the filter. The alcoholic filtrate is finally titrated
with N/io alkali. In the following Tableanumber of the values published
by Polenske for pure butter fats are given, together with the values for
the same butter fats containing respectively, 10, 15, and 20 per cent,
of cocoa-nut oil. The expression "new butter value" proposed by
Polenske has been avoided by the author, as it is better expressed by
"titration value of the insoluble volatile acids."
Polenske claimed that with the help of this Table an approximately
quantitative estimation of the cocoa-nut oil present in an adulterated
butter could be obtained ; this is based upon the deduction from the
data in the Table, that the amount of alkali necessary for the neutralisa-
tion of the insoluble acids is increased by o-i c.c. for each per cent,
of cocoa-nut oil added. The mode of calculation may be illustrated by
an example. Suppose a sample of butter fat gave a Reichert-Meissl
value of 24-5 and required 3-0 c.c. of TV/ 10 alkali for the neutralisation
of the insoluble volatile fatty acids. The insoluble volatile fatty acids
were of a liquid consistency. According to the Table a pure butter fat
of Reichert-Meissl value 24-5 should require only i-6 c.c. of iV/io alkali
for the neutralisation of the insoluble volatile fatty acids ; hence
3-0— 1-6 = 1-4 c.c. was necessary for the neutralisation of the insoluble
volatile acids ; the sample in question must therefore be considered to
have been adulterated with cocoa-nut oil. As each o-i c.c. of alkali is
taken to correspond to i per cent, of cocoa-nut oil, the sample is looked
upon as having been adulterated with 14 per cent, of cocoa-nut oil.
Examples 15 and 22 of the Table (24-2, 3-0 and 24-8, 3-0) would
indicate an addition of 10 per cent, of cocoa-nut oil. The sample
which gave the above figures actually contained lO per cent, of cocoa-nut
158
ANALYSIS IN OIL AND FAT INDUSTRIES
oil. A method based upon the same principle, but differing in the
practical details, has been described by A. Miintz and H. Coudon,^
Table 28.
Titration Values of Butter Fats. (Polenske.)
Titration values, i.e., number of c.c. X/10 KOU required for the neutralisation of the :—
^^
09
^
CQ
j^
X
^
93
X 0
S
~5
■S5
•o
■a s
2
'0
O
o
u
"5 "3
d
■5 C3
e3
O 03
o3
£■ S
tf
« >
0
« >
<s
eS >
£
* >
S
0^
IT *
=3
II
.2 «
5~
'•3
il
cO s
ea £>
eS V
cS »
oS
0
>
oS
>
OS
oS
3
>
''S
0
>J,
o
f-
a>
" ^
a
© tn
0 ^
•— 1
C U
C Im
No.
35
3
3
22
:3
S 2
2
1-2
3
3
3 y
3 0
S'o
3 U
l|
"3
s
II
1
II
"3
03
a
II
"o
C
>^
t-t
N.^
""^
Same butter fat with
Same butter fat with
Same butter fat with
Pure butter fat.
addition of 10 per cent.
addition of 15 per cent.
addition of 20 per cent.
cocoa-nut oil.
cocoa-nut oil.
cocoa-nut oiL
1
19-9
1-35
18-7
2-4
18-1
2-9
17-6
3-3
2
21-1
1-4
19-7
2-3
192
3-0
18-5
3-6
3
22-5
1-5
21-0
2-5
20-4
2-9
19-8
3-5
4
23-3
1-6
22-0
2-5
21-5
3-1
21-0
3-7
5
23-4
1-5
22-3
2-4
21-7
3-1
21-2
3-7
6
23-6
1-7
22-5
2-5
21-9
3-3
21-4
4-0
7
21-5
1-6
23-3
2-5
22-4
3-1
21-7
3-7
8
24-7
1-7
23-8
2-9
22-9
3-5
22-1
3-9
9
24-8
1-7
23-5
2-7
22-7
3-2
10
24-8
1-6
23-4
2-5
22-8
3-0
22-1
s-'e
11
25-0
1-8
23-0
2-7
23-3
3-1
21-8
3-6
12
25-1
1-6
23-5
2-5
23-1
3-0
22-5
3-8
13
25-2
1-6
23-4
2-6
22-9
3-0
22-3
3-7
14
25-3
1-8
24-0
2-9
23-5
3-5
22-6
41
15
25-4
1-9
24-2
3-0
23-7
3-6
22-6
4-1
16
25-6
1-7
24-1
2-7
23-3
3-1
22 "7
3-7
17
25-4
1-7
23-8
2-6
23-0
3-1
...
18
26-2
1-9
25-0
31
24-2
3-6
23-6
4-0
19
26-5
1-9
25-0
2-9
24-1
3-5
23-2
4-1
20
26-6
1-8
25-4
2-9
24-6
3-3
23-9
3-8
21
26-7
2-0
25-2
3-2
24-5
3-6
237
4-2
22
26-8
2-0
24-8
3-0
24-2
3-4
23-5
4-0
23
26-9
2-1
25-2
2-9
24-1
3-6
23 2
4-2
24
26-9
1-9
24-9
2-9
24-0
3-3
23-3
4-0
25
27-5
1-9
25-7
2-7
24-9
3-3
24-0
39
26
27-8
2-2
26-0
3-1
25-0
3-7
...
...
27
23-2
2-3
26-1
3-1
25-1
3-8
24-5
4-4
28
28-4
2-3
26-5
3-5
25-7
40
25-1
4-5
29
28-8
2-2
26-8
3-3
26-0
3-9
...
...
30
28-8
2-5
27-1
3-5
26-3
4-0
25-4
4-7
31
29-4
2-6
27-6
3-8
26-9
4-2
...
32
29-6
2-8
27-5
3-8
26-2
4-2
25-5
4-9
3:5
29-5
1 2-5
27-4
3-5
26-6
4-1
25-4
4-7
34
30-1 3-0
27-8
3-8
26-9
4-4
26-2
5-0
It must, however, be clearly pointed out that the titration values
must not be considered as definite and final indications, as was formerly
' MoniL Scient., 1904, 18, 530 ; /. Soc. Chem. Ind., 1904, 23, 764 ; cf. Lewkowitsch, Chemical
Technology, etc., vol. ii.. p. 695.
BUTTER. MARGARINE. LARD. 159
supposed ; indeed, as a rule, they do not furnish any more information
than the Reichert-Meissl value themselves. For the detection of tallow
and hog's lard in butter fat, with the aid of the "difference number"
(difference of melting points), cf. Lewkowitsch, Chemical Technology, etc.,
vol. i., p. 324.
2. Margarine.
The examination of margarine fat comprises the determination of
the Reichert-Wollny value, and in those countries in which sesame oil
must be added, its detection by the Baudouin test. If the quantity of
milk prescribed by law in this country (10 per cent, of butter fat) has
not been exceeded in the preparation of the margarine, the Reichert-
Wollny value must not exceed 4. This is, however, only the case when
the margarine contains no cocoa-nut oil, but since the latter has come
into use in the manufacture of margarine Reichert's method must,
if necessary, be supplemented by Polenske's test. Margarines consisting
entirely of cocoa-nut oil are readily identified by the Reichert value,
saponification value, iodine value, and titration value of the insoluble
volatile acids.
3. Lard, xA-Rtificial Lard, Lard Substitutes.
The testing of lard for impurities and the detection of substitutes
are among the most important problems in the analysis of edible fats.
The refraction is first observed in a (butyro) refractometer ; the iodine
value of the fat and that of the liquid acids are also determined. If
these tests give cause for suspicion, the sample is examined for vegetable
oils and fats by the phytosteryl acetate test (p. 141). If cocoa-nut oil or
palm kernel oil is suspected, the Reichert-Meissl (Reichert-Wollny)
value (p. 119) and the titration value of the insoluble volatile acids
(Polenske's method, p. 156) are determined.
The detection of Talloiv or Beef Stearitie is a difficult problem ; for
information the reader is referred to the monograph on " Lard " in the
author's Chemical Technologj' and Atialj'sis of Oils, Fats, and Waxes, vol.
ii., p. 560.
4. Chocolate Fats, Cocoa-butter Substitutes.
Under the former of these two terms, the author includes all the
fats which serve as substitutes for the expensive cocoa-butter in the
manufacture of cheap chocolates. These are for the most part " cocoa-
nut oil stearine " and " palm kernel stearine," which are recognised by
their low iodine values and high saponification values, as also by their
Reichert-Meissl values. The melting point of these "stearines" is
frequently raised by the addition of tallow or of oleostearine. The
determination of the melting point of the fat and the titre test of the
fatty acids are of importance.
160
ANALYSIS IN OIL AND FAT INDUSTRIES
C.—WOOL OILS.
These are oils which are used to lubricate the wool fibre previous to
spinning and weaving. The\' are either pure fatty oils (olive oil, lard
oil, neat's foot oil) or oleic acid, or mixtures of this acid with unsaponifi-
able oils (mineral oils, wool-fat hydrocarbons).
The value of wool oils depends upon the ease with which the\- are
removed from the fibre by scouring, and further upon their freedom from
liability to spontaneous combustion.
The quantitative estimation of the unsaponifiable matter (p. 124)
furnishes important information. This is insisted upon by Fire Insur-
ance Companies, as the insurance premium is fixed at a higher rate the
greater the amount of unsaponifiable matter present.
The liability to spontaneous combustion is ascertained b)' determin-
ing the flashing point (cf. the sections on " Mineral Oils," p. 28, and
" Lubricants," p. yy) ; and, further, in the case of pure oils and pure
fatty acids, by the behaviour of
the wool oil to cotton fibre, at a
somewhat high temperature in
W. Mackey's "Cloth Oil Tester."
This apparatus^ (Fig. 43) con-
sists essentially of a cylindrical
water-bath, closed by a lid in
which a thermometer is fixed.
In the lid are fitted two tubes.
A and B, through which air is
circulated in the direction of the
arrows. The water - bath con-
tains a wire-gauze cylinder C,
in which is placed a wad of
cotton wool impregnated with
the wool oil under examination.
To carry out the test, 7 g. of pure cotton wool is weighed out and
soaked with 14 g. of the wool oil in a flat porcelain dish. This must
be done carefully so as to distribute the oil uniformly. It is best to
teaze the cotton wool out and to impregnate it carefully with the
oil, as the success of the test depends, to a large extent, upon the
uniform distribution of the oil. The cotton wool containing the oil is
brought into the cylinder C, the thermometer being held firmly so that
the cotton wool is packed round the mercury bulb. The water in the
steam jacket is heated until it boils vigorously, the C)-linder introduced
into the bath, the cover brought down over the thermometer and held
in place by the clamp D. After about an hour, during which time the
1 Made by Messrs Reynolds & Branson, Leeds.
Fi.i. 4S.
LINSEED OIL
161
water is kept boiling vigorously, the temperature is observed. Moisture
must be rigorously excluded.
If, after an hour, the thermometer shows a temperature exceeding
ioo°, the oil is considered as liable to spontaneous combustion. In the
case of very dangerous oils the temperature rises to 200° within forty-
five minutes. If the temperature rises above 150° it is advisable to
remove the thermometer, as the oiled cotton wool easily becomes ignited.
This method gives only comparative values ; hence the details must
be precisely observed. Before proceeding with the experiment, it is
advisable to test olive oil and pure cotton-seed oil as examples,
representing a safe and a dangerous oil respectively.
Z*.— LITHOGRAPHIC VARNISHES— POLYMERISED
LINSEED OILS.
Lithographic varnishes are obtained by heating drying oils — chiefly
linseed oil — to high temperatures in absence of air. The more strongly
the oil is heated the more energetic is the resulting polymerisation.
The determination of the iodine value does not furnish sufficient data
for the valuation of such oils. According to the author,^ the determina-
tion of the yield of insoluble bromides (p. 138) gives reliable results.
Thus, whilst raw linseed oil yields up to 42 per cent, of insoluble (hexa)
bromides, the yield in the case of highly polymerised oils falls to zero.
The data given in the following Table will serve as a guide in the
interpretation of the values found.
Table 29.
Values of Polymerised Linseed Oils — Lithograph Varnishes.
(Lewkowitsch.)
OJ
CO
>,
b
§
>
m
1
"3
a5
3
03
-.J
a
0
-a
■4^
ClC
m
'3
0
>
0
"as
^1
a
w
Oxidised fat
§1
rv e8
0
>
'0
>
3;a
"3 '3
> a
a
0
3
Pur
Per
Per
Per
Per
cent.
cent.
cent.
cent.
cent.
Raw linseed oil
0-9308
...
186-4
24-17
...
...
Linseed oil heated
to 310°
0-9354
...
176-3
8-44
Thin varnish I.
0-9676
189-5
107-7
0-17
94-75
4-17
1-76
9-71
6-09
6-5
114-74
39-31
n. .
0-9691
193-0
125-3
2-0
94-8
0-34
0-13
Medium varnish I. .
0-9693
194-4
121-9
0-95
93-8
1-48
0-57
II .
0-9703
190-5
126-5
0-0
1-53
1-8
Thick oil I.
0 9720
190-0
109-4
0-24
94-68
6-36
1-45
9-17
5-12
1-65
13-53
32-31
„ IF. . .
0-9747
193-7
118-5
0-0
95-6
0-36
0-25
Burnt varnish .
0-9912
178-6
102-69
0-0
93-53
9-12
1-14
...
...
...
Analyst^ 1904, 29, 2.
Ill
162 ANALYSIS IN OIL AND FaT INDUSTRIES
£.— "BOILED" LINSEED OIL, LINSEED OIL VARNISH,
VARNISH OILS.
The term " boiled " oil originates from the times when the now
almost obsolete process of heating the oil over free fire to 2io°-26o^,
with the addition of suitable metallic salts or metallic oxides (siccatives,
driers) was practised. Now " boiled " oil is prepared by heating linseed
oil by steam to 150°, at the same time mixing the oil intimately with
added siccatives by vigorous stirring. According to the nature and
quantity of the siccative and the duration of the heating, the resulting
product is a "pale boiled oil" or "double boiled oil." ^
Linseed oil is practically the only drying vegetable oil which serves
for the technical preparation of good boiled oil.
The examination of the raw materials comprises the testing of: —
1. The Linseed Oil.
2. The Siccatives.
I. Linseed Oil.
The specific gravity should not be below 0-930. The iodine value
should be as high as possible, but at least 170, and the higher the
better. The oil must be free from adulterants such as marine animal
oils (bromide test), rosin oils, mineral oils, and rosin acids (colophony).
For the valuation of a linseed oil which has been found to be free
from impurities, the time it requires to dry is of importance. In
addition to the determination of the time required to dry to an elastic
skin, the valuation of a linseed oil for varnish manufacture often
includes the determination of the quantity of oxygen which it absorbs.
Livache's method and the glass plate method (p. 127) may indeed be
used for quantitative measurements, but, except in special cases, these
give but little information. It is of far greater importance to ascertain
the time of drying and the consistency of the elastic skin. This is
done by the method generally used in practice. Much experience is,
however, required in order to judge an oil by the drying test. In
examining an oil it is therefore advisable to make comparative tests
with a boiled oil known to be pure and of good drying quality, on glass
plates covered with a thin la\'er of the oil (spread with the aid of a
spatula, not with a brush). A good linseed oil should dry in less than
three days ; after this time it should not be sticky to the touch and
should give a coherent, elastic skin. (Oils containing considerable
(juantities of unsaponifiable matter or foreign oils are recognised as
adulterated by this test alone, as the presence of the impurities prevents
the formation of a good elastic skin.)
' For the theory of the process of "boiling" and further details, and the preparation of
varnishes at ordinary temperatures, cf. Lewkowitsch. Chemical Technology of Oils, etc., vol iii.,
r- 138.
LINSEED OIL 163
An important test for judging the suitability of a linseed oil for
boiled oil (and especially for varnishes), consists in heating the oil in a
test tube until it begins to boil. Good oil remains clear (it generally
becomes somewhat paler after heating) ; if a mucilaginous mass
(" spawn," " break ") separates out, the oil must be rejected as unsuit-
able. In the case of oils of inferior quality the "spawn" extends
through the whole mass of the oil like frog spawn. Such oils are
useless for the manufacture of boiled oil and varnish in this condition.
Freshly expressed ("green") linseed oil froths on heating, whereas old
" tanked " oils, from which water and mucilage have settled out, do not
froth. As the latter are most suitable for the above-named purposes,
the preference of the manufacturers for "tanked" oil is readily under-
stood. The mucilaginous mass consists, as G. Thompson ^ has shown, to
the extent of one-half of phosphates (and sulphates) of calcium and
magnesium, which on settling out carry down with them organic
impurities.
2. SlCCATIVES.2
In the older processes for the manufacture of varnishes the only
drying agents used were Oxides of lead and manganese, such as massicot,
red lead, and pyrolusite. The salts of zinc, copper, and iron do not
possess the property of imparting the desired effect to the oil. More
recently, manganese acetate, oxalate, and borate have also come into
use. As colophony absorbs oxygen from the air, the metallic salts of
rosin acids, lead rosinate, manganese rosinate, and calcium rosinate are
also employed as siccatives. The metallic salts of the rosin acids are
prepared either by precipitating solutions of their sodium salts with
metallic salts {e.g. sodium rosinate and manganese sulphate), or by
melting together a metallic oxide with colophony. Hence, a distinction
is made in commerce between " precipitated " siccatives and " molten "
siccatives. By melting or precipitating colophony with a mixture of
manganese and lead salts, " molten " or " precipitated " as the case may
be, manganese-lead siccatives are obtained. A simple method of
distinguishing between "molten" and "precipitated" siccatives is to
determine the proportion of water. Only the " precipitated " siccatives
contain a considerable quantity of water (up to 6 per cent). The
degree of fineness is also of importance. The further valuation of these
siccatives is carried out by the ordinary methods of mineral analysis.
A further development in the industry of driers is the use of metallic
salts of the fatty acids of linseed oil. These salts are prepared either
by precipitating soap solutions (obtained by the saponification of
linseed oil with caustic soda) with metallic salts, or by melting together
1 y. Soc. Chem. Ind., 1903, 22, 1 005.
'■^ C/. Weger, Z. angew. Chem., 1896, 9, 531 ; 1897, 10, 401, 542, 560 ; y. Soc. Chem. hid.,
1896, 15, 728 ; 1898, 17, 360.
164 ANALYSIS I\ OH. AND FAT INDUSTRIES
the fattv acids and metallic oxides. In this manner " precipitated " and
" molten " manganese and lead linoleates are obtained. The salts
derived from linseed oil fatty acids and colophony are soluble in
turpentine, ether, chloroform, and in linseed oil ; hence they are termed
"soluble siccatives." Solutions of such siccatives in linseed oil or
turpentine, or in mixtures of these, are met with in commerce under
fancy names, such as " liquid driers," " terebene," etc.
The valuation of the Soluble Siccatives cannot be based upon the
content of metal, as found by direct ignition and weighing the ash,
since suspended metallic oxides, which are not chemically combined to
fatty acids or rosin acids, are not only useless, but actually detrimental
to the manufacture, as they render the finished product turbid. As a
preliminary test, the drier is treated with organic solvents, A good
drier should dissolve completely in ether, or in the case of lead rosinate, in
chloroform and in turpentine. (Turpentine also dissolves lead rosinate
on warming, but the dissolved siccative separates out again on cooling.)
In the analysis of a Soluble Drier, the organic component is first
burnt off in a porcelain crucible, and the lead, manganese, etc., deter-
mined in the ash. The weight of the ash alone does not always give
reliable results, as the " molten " siccatives often contain sand, etc.
Besides lead and manganese, calcium should also be determined in the
ash. (Calcium rosinate is admissible as a component of driers.) A fresh
portion of the sample is then extracted with ether, chloroform, or
turpentine, the solution filtered, the solvent evaporated off, and the
residue incinerated. In the ash the lead or manganese (or both) are"
determined quantitatively ; the difference between the lead and
manganese found, and the proportion of these metals in the original
determination corresponds to the weight of lead and manganese present
as insoluble excess. The result may be checked by the determination
of the dissolved metal in an aliquot part of the solution. In case of a
rosinate, the dissolved lead must be determined by difference, as it is
stated that chloroform can be removed completely from the rosinate
only at a red heat, at which temperature part of the lead chloride
volatilises.
The determination and examination of the fatty and rosin acids {cf.
p. 195) is of less importance; it can, however, be carried out by decom-
posing the ethereal solution with a mineral acid. It must, however, be
emphasised that the chemical examination does not furnish sufficient
information as to the "drying" properties of the siccative. The colour
of the boiled oil to be prepared, its drying properties and other
conditions, are the determining factors in the choice and quantity of a
drier.
The chemical examination of the finished boiled oil comprises the
detection of adulterants such as marine animal oils, vegetable oils other
LINSEED OIL
165
than linseed oil, mineral oils, rosin oils, and colophony. Oils which
have been prepared with liquid siccatives may contain small quantities
of turpentine as a legitimate ingredient. The so-called "patent
varnishes " are mostly adulterated oils.
Boiled Linseed Oil is distinguished from raw linseed oil by its
higher specific gravity — above 0-94— also by the presence of a drier ;
hence on incinerating the oil a residue remains. Boiled oil is frequently
mixed with raw linseed oil, as boiled oil when used alone sometimes
gives a " hard " surface which readily cracks ; hence a method for the
detection of raw linseed oil in the boiled oil is only of some importance
in those countries in which linseed oil and boiled oil pay different
Customs duties.
The best method for the detection and approximate estimation of
raw linseed oil in boiled oil which has been manufactured at hio-h
temperatures is the bromide test ^ (p. 13S). A number of data in
regard to linseed oils are given in the following Table : —
Table 30.
Values for Linseed Oils. (Lewkowitsch.)
Sp. gr
Iodine
Insoluble bromides
value
from the glycerides
Per cent.
Linseed
oil (raw)
0-9308
186-4
24-17
(light boiled) .
0-9429
171-0
20-97
(double boiled .
0-9449
169-96
13-03
(ozonised)
0-9310
180-1
36-26 to 36-34
M • •
0-9388
171-2
25-73
»
0-9483
169-7
30-19
The quantity of oxidised acids (p. 139) in boiled oils should not
exceed a iew per cent.
It should be noted that in consequence of the presence of metals in
boiled oils, the iodine value found is too high, unless the metal be
previously removed by treatment with mineral acids. The magnitude
of the error which may result from this cause is shown by the following
data : —
Varnish oil from
Original boiled oil.
After separating
the metal.
Linseed oil . . '
173-3
177-2
169-7
171-1
The valuation of a boiled oil which has been found free from
^ Lewkowitsch, Analyst^ 1904) 29, 2.
16G ANALYSIS IN OIL AND FAT INDUSTRIES
adulterants must be based on practical tests, the oil being spread out
in a thin layer on glass plates and exposed to the air as described on
p. 127. The boiled oil is taken either in its original state, or mixed
with pigments, such as are used for paints. A weighed or measured
quantity of the boiled oil is very intimately mixed with a weighed
quantity of pigment on a glass plate, the mixture spread out in a thin
la\'er, and exposed to the air, side by side with a paint prepared in
precisely the same way with a boiled oil of good quality. Practical
experience is, however, indispensable to arrive at a correct opinion.
Boiled linseed oil is used extensively for the preparation of paints
and varnishes.
/^.—LINSEED OIL PAINTS AND VARNISHES.
Linseed Oil Paints. — No great difficulties are involved in the
testing of linseed oil paints. The paint is shaken with ether, a mineral
acid added to decompose the metal soap and to bring it into solution,
in case it be soluble in acids, and the ethereal solution separated from
the aqueous solution and from any insoluble residue. After evaporat-
ing off the ether the residual oil maybe further tested. The mineral
substances are examined by the usual methods of mineral analysis.
The oil content, as a rule, amounts to 8-10 per cent, in the case of
white lead, and to 30-40 per cent, in the case of black paints ; other
pigments require intermediate amounts.
Varnishes consist of a mixture of boiled oil, with various gum resins .
and oil of turpentine.'
The preparation of these products is guarded as a valuable trade
secret. The "art" of the manufacturer lies in the choice of suitable
gum resins, and in the treatment of these previous to their introduction
into the boiled oil. Most gum resins must be heated beforehand to over
2,00^. This causes them to melt and to undergo a partial decomposition,
certain oily products distilling over; the loss of weight caused by this
treatment is from 5 to 25 percent. In the manufacture the melted gum
resins are dissolved whilst hot in a drying oil or a boiled oil ; in
the former case the oil is " boiled " after the addition of a suitable drier.
The product thus obtained is termed " varnish oil." The varnish oil is
allowed to stand, so that "foots" may separate out, or it is filtered
through a filter press. Finally, the commercial enamel varnish is
prepared by diluting the "varnish oil " with turpentine.
The most suitable oil, and in fact the only oil which is used for the
manufacture of the best varnishes, is linseed oil. A large number
of patents has been taken out for the manufacture of linseed oil
^ Lacquers are simple solutions of gum resins in alcohol, turpeniine, fusel oil, etc., the
examination of which lies outside the scope of ih'S section.
LINSEED OIL PAINTS AND VARNISHES 167
substitutes, the linseed oil being replaced by tung oil, or by a mixture of
linseed and tung oils. In most of the products thus prepared which
have come under the author's notice, the expensive gum resins had been
replaced by colophony.
The oil of turpentine is also frequently replaced by cheaper hydro-
carbons, especially by petroleum hydrocarbons of the same boiling point.
A complete chemical examination of varnish oils is in our present
state of knowledge a very difficult problem. Whilst the fatty oil used
and the volatile solvent can be more or less easily identified, it is in
some cases absolutely impossible to identify the gum resins by chemical
means alone, and an extended practical experience is necessary
to interpret the results furnished by the chemical tests
In the chemical examination of a varnish the volatile solvent is first
isolated by distilling lOO g. of the varnish in steam until no more
volatile oil passes over. The examination of the volatile oil is
comparatively simple; the specific gravity, boiling point, and iodine
value of the sample yield the requisite data. The iodine values
of genuine American turpentine from the live tree lie between 370 and
400. Oil from the dead w^ood, such as " Kienol," has a lower iodine
value.^
The residue remaining in the flask is freed from water and the
quantity of fatty oil is estimated approximately by determining the
quantity of glycerol obtained after saponification. The separation of
the gum resins from the boiled oil cannot always be satisfactorily
effected. The usual characteristics of the gum resins do not always
yield sufficient information, as their composition is completely altered
on heating to 300^ The values given in the following Table ^ may
furnish useful information.
The examination of the ash shows what metal or metals were
present in the siccative. Considerable quantities of lime in the ash
indicate the presence of calcium rosinate, which is frequently added in
much too large proportion in order to impart a fictitious hardness and
lustre to the dried varnish.
The chemical examination must be supplemented by "practical"
tests. The practical examination of the fatty oil as to its usefulness
and drying properties is carried out in a similar manner to that
described above under boiled oil. The influence of atmospheric
conditions (moisture, light, etc.) can only be determined by practical
tests either of the varnish alone, or in admixture with pigments.
Enamels.' — This is the technical term for mixtures of varnish with
pigments such as zinc oxide, lead oxide, iron oxide, etc. Their chemical
^ Cf. Lewkowitsch, Chemical Technology, etc., vol. iii., p. I2i.
^ Cf. Lewkowitsch, Analyst, 1901, 26, 37.
* Not to be confused with the enamels of the ceramic industry.
168
ANALYSIS IN OIL AND I AT INDUSTRIES
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OXIDISED OILS 169
examination consists in a combination of the methods given for linseed
oil paints and varnishes.
6^.— OXIDISED OILS.
Under this term the author includes all those oils which have
taken up oxygen on exposure to the air, or have been oxidised
artifically by heating (" blowing ") in a current of air or oxygen.
It is convenient to subdivide the oxidised oils into two groups.
I. Oxidised Oils, obtained from Semi-drying Vegetable
Oils, Marine Animal Oils, and Liquid Waxes.
These oils (commercially known as " blown oils," " thickened oils,"
"soluble castor oil") are obtained by treating vegetable semi-drying
oils, marine animal oils, or liquid waxes, with a current of air at
a somewhat high tem.perature whereby the density and viscosity of the
oils are increased. They thus approximate in their properties to castor
oil, but differ from the latter by being miscible with mineral oils — hence
their designation as "soluble castor oil." They further differ from
castor oil in their insolubility in alcohol. The most striking chemical
change which accompanies the "blowing" is that a considerable
quantity of soluble fatty acids and of oxidised fatty acids are formed.
For this reason these oils have high saponification values and somewhat
high Reichert-Meissl values. Their acetyl values are also high.^
The blown oils are used com.mercially as lubricants, for the most
part in admixture with mineral oils, fatty oils, and rosin oils.
2. Oxidised Oils obtained from Drying Oils.
When drying vegetable oils are exposed to the air or to a current of
air or oxygen at somewhat high temperatures, the production of the
oxidised acids proceeds much more rapidly than is the case with semi-
drying oils. Extended use is made of this property in the employment
of paints and varnishes, the vegetable oil — especially linseed oil — drying
finally to a solid mass which forms a continuous skin on the surface
of the object with which the paint or varnish is coated.
The chemical change which occurs when a vegetable oil dries to a
solid elastic skin has been only incompletely investigated. The process
seems to be the same whether raw linseed oil absorbs oxygen from the
air, or whether the drying is accelerated by conversion of the oil into a
" boiled " oil, or finally, whether the raw linseed oil is treated with
a current of oxygen at higher temperatures after the addition of driers.
It is probable that in the first stage the linolenic acids of the linseed
^ Detailed Tables, showing the characteristics of "blown" oils, are given in Lewkowitsch's
Chemical Technology^ etc., vol. iii., pp. 132 et seg.
170 ANALYSIS IN OIL AND FAT INULSTHIES
oil are attacked ; the iodine values decrease and the amount of oxidised
fatt)' acids increases. When the oxidation of the linseed oil is carried
further, i.e. until the linseed oil has taken up the maximum quantity of
oxygen, a gelatinous solid mass is obtained, which is known as " solid
linseed oil," or "oxidised linseed oil" ("linoxyn ").^
Solid linseed oil is used very extensively for the manufacture
of Lino/eimi, the solid oil being mixed with various gum resins,
powdered cork, and materials added to increase the weight. The mass
thus obtained is called Liuoleiun Cement. It is pressed on a jute cloth
by means of rollers, and finally allowed to "ripen" at a temperature of
about 20 . The valuation of linoleum depends almost entirely upon
practical tests. The chemical examination consists in the determination
of the ash and the treatment of the powdered mass with ether. Any
considerable quantity of linseed oil in the extract in addition to gum
resins would indicate that the oil has not been treated sufificientl}' long
with oxygen. The methods of testing used by the Techuische
Versuchs-Anstalten in Germany- have been adversely criticised by H.
Ingle,-'' who has proposed alternative methods.
//.—VULCANISED OILS, INDIARUBBER SUBSTITUTES.
See the section on " Indiarubber and Rubber Goods," this Vol.,
pp. 398 et seq.
/.— SULPHONATED OILS, TURKEY RED OILS.
Turkey red oils are thick, oily, dark yellow liquids, which are used
in printing and dyeing cotton. The part which they play in fixing the
dye is not yet fully elucidated. Genuine Turkey red oil is prepared by
the action of concentrated sulphuric acid on castor oil. The resulting
oil is isolated by drawing off the acid layer, washing with sodium
sulphate solution, and partially neutralising the acid with caustic soda
solution or ammonia until the product gives a perfectly clear solution
with a little water.
The portion of the product of the action of sulphuric acid on castor
oil which is soluble in water contains for the most part ricinoleo-
sulphuric acid, which is partially hydrolysed by boiling with dilute
acids into sulphuric acid and ricinoleic acid (a further portion is
converted to inner anhydrides of ricinoleic acid). The portion insoluble
' For recent views as to the process of drying, cf. Lewkowitsch, Chemical Technology, etc.,
vol. iii., p. 139.
"^ H. Bjrchartz, Mitt, kdnigl. tech. Versuchsarist., 1899, 17, 285 ; /. Soc. Chetn. hid., 1900,
19. 255-
•' y. Soc. Chem. Ind., 1904, 23, 1197; cf. Lewkowitsch, Chemical Technology, etc., vol. ii.,
p. 146.
SULPHONATED OILS. TURKEY RED OILS 171
in water contains ricinoleic acid and anhydrides of this acid, together
with unchanged oil (neutral fat). The testing of Turkey red oil consists
of preliminary tests (chiefly a dyeing test) and the determination of the
chemical characteristics.
Prelii/iifiary Tests. — Turkey red oil should give a perfect emulsion
with lo vols, of water; no drops of oil should separate until the
emulsion has stood for a long time. The emulsion is compared with
an emulsion prepared in exactly the same way from an oil known to
be of good quality. If an excess of alkali is present it must be reduced
to a minimum by the addition, drop by drop, of dilute acetic acid.
The emulsion should react faintly acid towards litmus. A good oil
should dissolve to a fairly clear solution in all proportions of ammonia,
and on diluting considerably only a slight turbidity should result.
For the dyeing test the oil under examination is diluted (together
with a check sample) in 15-20 parts of water, and pieces of cotton cloth
of equal size are soaked in exactly the same manner with the two
diluted Turkey red oils. The cloths are then dried, mordanted with
alumina, and dyed with alizarin. Recently paranitraniline red has been
preferred by practical dyers. It is difficult for anyone who has not had
practical experience to judge a Turkey red oil correctly on the strength
of the dyeing test alone.
Determination of the Characteristics. — The value of a Turkey red oil
is primarily dependent upon the proportion of total fat contained, that
is, upon the sum of the insoluble fatty acids and the neutral fat which
separate out when the oil is decomposed by boiling with dilute acids.
The total fat is determined as follows : — A small deep porcelain
dish of 100-150 c.c. capacity is tared together with a glass rod; then
3-4 g. of Turkey red oil are weighed into it and stirred with 20 c.c. of
water, which is gradually added. If the liquid becomes turbid, a drop
of phenolphthalein solution is added and ammonia run in carefully until
the red colour persists ; this produces a clear solution. Then 30 c.c. of
dilute sulphuric acid (1:4) and 5-8 g. of beeswax are added, and the
whole heated to gentle boiling until the oil layer has separated out
completely. The solution is allowed to cool, the solidified cake of fat
is lifted out with the aid of the glass rod, treated as described under the
analysis of "Soap" (p. 191), and weighed. The weight of the beeswax
is, of course, deducted from the total weight.
The following shortened method, described by Finsler, and recom-
mended by F. Breindl,^ is often used in works : — 30 g. of the sample
are accurately weighed out and rinsed into a flask of about 200 c.c.
capacity with about 70 c.c. of hot water. The neck of the flask is
divided in \ or ^^ c.c. To the contents of the flask 25 c.c. of sulphuric
acid of sp. gr. 1-563 are added and the mixture is heated, with frequent
1 Miiteil. d. k. L Tech. gew. Museums, 1888, p. 81 ; /. Soc, Chem, Ind., 1889, 8, 573.
172 ANALYSIS IN OIL AND FAT INDUSTRIES
shaking, to boiling until the fatty matter forms a clear, transparent
layer. A hot saturated solution of common salt or sodium sulphate is
then carefully added to raise the layer of fatty matter completely into
the neck of the flask. After standing for about half an hour the volume
of the fat is read off. The number of cubic centimetres found multiplied
by 3-33 corresponds to the percentage of the total fat. As, however, the
specific gravity of the fatty matter is, as a rule, 0-945, ^ corresponding
correction must be applied.
The total amount of fatty matter thus found is less than the actual
sulphonated oil dissolved in the water by the amount of sulphuric acid
split off on boiling with hydrochloric acid.
In addition to the total fatty matter the examination also comprises
the determination of (<^) Neutral Fat, (/') Sulphonated Fatty Acids,
(c) Alkalis (Ammonia and Soda), (d) Sulphuric Acid.
(a) Neutral Fat. — 30 g. of the sample are dissolved in 50 c.c. of
water, treated with 20 c.c. of ammonia and 30 c.c. of glycerol, and
extracted two or three times successively with 100 c.c. of ether. The
combined ethereal extracts are washed with water, the ether distilled
off from a small weighed flask, and the residue dried in the flask at 100°
and weighed.
(b) Sulphonated Fatty Acids. — For their estimation 4 g. of the
sample are boiled in an Erlenmeyer flask with 30 c.c. of dilute sulphuric
acid (i : 5) for forty minutes, with frequent shaking. After cooling, the
liquid is transferred to a separating funnel and extracted with ether.
The aqueous layer is drawn off and the ethereal layer washed with
water. The washings are added to the main portion of the aqueous
solution, and the sulphuric acid is estimated by precipitation with
barium chloride. A deduction must be made from the amount of
sulphuric acid found, to allow for any sodium or ammonium sulphate
present as estimated under {d). The difference is calculated to
recinoleic acid. 80 parts SO3 correspond to 378 parts of recinoleo-
sulphuric acid, Cj3H3.jO.vO.SO3H.
(c) Amvio7iiiiin or Sodium Hydroxide. — From 7-10 g. of the sample
are dissolved in ether and shaken out with four successive amounts of
5 c.c. of dilute sulphuric acid.
For the determination of the ammonia the acid liquid is distilled
with potassium hydroxide solution in the usual way and the evolved
ammonia absorbed in a known volume of standard acid.
For the determination of sodium hydroxide the acid liquid is
evaporated in a platinum dish on a water-bath, the excess of sulphuric
acid driven off by heating on a sand-bath, the residue mixed with
ammonium sulphate, ignited, and the remaining sodium sulphate
weighed.
(d) Sulphuric Acid. — The sulphuric acid which is present as
STEARINE CANDLES 173
ammonium or sodium sulphate is determined by dissolving a weighed
quantity of the sample in ether, and shaking out several times with a
few cubic centimetres of concentrated salt solution which is free from
sulphate. The total washings are diluted, filtered, and the filtrate
precipitated with barium chloride.
If it be required to determine the nature of the oils used in the
preparation of the Turkey red oil, the acetyl value of the total quantity
of fat must be determined.
If the acetyl value is 125 or more, the oil is derived from pure
castor oil; if other material has been used, the acetyl value is
lower.
AT.— THE CANDLE INDUSTRY.
The tallow candle industry is now practically extinct. At present
the candles met with in commerce are — i, Stearine Candles, generally
containing considerable amounts of paraffin wax ; 2. Paraffin Candles,
always containing small additions of stearine ; 3. Spermaceti Candles ;
4. Wax Candles (beeswax candles). Ceresin is not used solely as
a material for candles^ but it is employed extensively in the
manufacture of night-lights.
I. Stearine Candles.
The materials used in the manufacture of "stearine" ("stearic
acid ") for candles are primarily beef and mutton tallow, bone fat, and
palm oil. Less important raw materials are some solid vegetable fats,
such as Chinese tallow, Malabar tallow, shea-butter, etc. In the candle
industry three main products are obtained, i. A mixture of solid fatty
acids known as " stearine," the actual candle material; 2. " Oleine " or
technical oleic acid, which is used in the manufacture of soaps or as
wool oil ; and 3. Glycerin. The resolution of the fats into free fatty
acids and glycerol is efifected by one of the following processes : — •
(i) Treatment with water under high pressure; (2) Hydrolysis with
lime or magnesia or zinc dust ; (3) Hydrolysis by means of concentrated
sulphuric acid ; (4) The combination of methods 2 and 3 ; (5) Hydro-
lysis by means of Twitchell's reagent (prepared by allowing an excess
of sulphuric acid to act on a solution of oleic acid in aromatic hydro-
carbons). The solid fatty acids obtained by these processes and
separated by pressing the liquid fatty acids differ considerably in
value, for whereas those prepared by methods i, 2, and 5 consist
essentially of the solid acids originally present in the fats (chiefly
palmitic and stearic acids), concentrated sulphuric acid converts oleic
acid partially into " iso-oleic " acid, a solid mixture of several isomeric
oleic acids, capable of being used as a candle material, and solid
stearolactone.
]7t ANALYSIS IN OIL AND FAT INDUSTRIES
(a) Testing of the Raw Material.
The proportion of water and the quantity of non-fatty substance
are of importance. These are first determined. The solidifying point
of the fatty acids and the colour of the fat are also of great importance.
It is frequently required to determine the unsaponifiable matter, the
free acids, the oleic acid, and the yield of glycerol. A description of
these determinations has been given in the main in the preceding
Section, to which the following details are a necessary supplement.
1. Fats Zi'hich contain targe quantities of Unsaponifiable Matter — e.g.
certain kinds of shea-butter, containing 15 per cent, of unsaponifiable
matter — are unsuitable for the manufacture of candles. A small quantity
of unsaponifiable matter such as is found in bone fats is not detrimental.
2. The Solidifying point of the Fatty Acids, termed in commerce the
"Titre" ("tallow titre "), is the most important criterion for the valua-
tion of the raw materials for use in the manufacture of candles. The
higher the titre the more valuable is the material. As it is necessary
in determining the titre, by which tallows are mostly sold, to adhere
precisely to a standard method of working in order to avoid differences
of even tenths of a degree, it is necessary to give a detailed description
of the method of determining the titre as adopted by the International
Congress of Applied Chemistry in London in 1909.^
The method proposed originally by Dalican has been adopted in
England, France, and the United States for the testing and valuation
of commercial fats. It gives reliable results and constant figures in
duplicate examinations, as the author can confirm from his own '
experience, so long as care is taken to perform the test under precisely
the same conditions.
For the determination, 50 g. of the sample are saponified by heating
with 40 c.c. of aqueous potassium hydroxide solution ofsp.gr. 1-4 and
40 c.c. of strong alcohol in a flask under a reflux condenser, or in a
porcelain dish on the water-bath. A flask is preferable for hard fats,
to ensure complete saponification. The soap solution is freed from
alcohol, dissolved in 1000 c.c. of water, and the fatty acids liberated with
sulphuric acid, separated from the water, and finally filtered through
a dry pleated filter into a porcelain dish. The fatty acids are then
allowed to solidify in a desiccator and left to stand over night. (Accord-
ing to the resolutions of the Congress it is permissible to determine the
titre after a few hours' standin;^ in cases of exceptional urgency.) On
the following day the fatty substance is carefully melted in an air-bath
or over a free flame, and enough is poured into a test tube 16 cm. long
and 3-5 cm. broad to fill the tube more than half full. The tube is then
fitted by means of a cork into a wide-mouthed bottle, 10 cm. wide and
^ Comptes rendus de la Commission inlernationaU d' Analyses au I7//"'< Congres Inttrnalional
de la Chimie applttjucr, par L. I indet, Paris, 1909 p. 181.
STEARINE CANDLES
175
13 cm. high, and an accurate thermometer divided in yV degrees is
immersed in the fatty acids, so that the bulb is in the middle of the mass.
The tube is then allowed to cool slowly. As soon as crystals are seen
at the bottom of the test tube the mass is stirred by means of the
thermometer, first three times from right to left, and then three times
from left to right. The stirring is continued rapidly with the thermo-
meter, care being taken that it does not touch the sides of the tube, so
that all solidified particles are well stirred into the mass as soon as they
appear ; the fatty acids then become turbid throughout the whole mass.
The temperature is now carefully watched. It first falls, and then
suddenly rises a few tenths of a degree, reaching a maximum and
remaining at this point for a short time before it falls again. The
maximum temperature observed is called the " Titre " or solidifying
point.
R. Finkener ^ uses large quantities of fatty acids in a small pear-
shaped flask of about 50 mm. diameter. To avoid rapid cooling, he
places the vessel containing the molten
fatty acids in a wooden box (Fig. 44).
This apparatus has been adopted as the
official apparatus in the German Custom
offices. In Austria the process proposed
by F. Wolfbauer- is used in technical
work. In this method the fatty acids
(from 120 g. of the sample) are dried
for two hours at lOO"' ; the rest of the
determination is carried out exactly as
described above.
A. Shukoff-^ has constructed an ap-
paratus by means of which it is possible
to avoid small personal errors, which consists of a vessel surrounded by
a Dewar vacuum jacket ; this prevents too rapid cooling of the fatty
acids on the walls of the vessel. The dimensions of the apparatus are
given in Fig. 45.
For the determination, 30-40 g. of the melted fatty acids are poured
into the inner vessel, which is then closed by a cork, through which
passes a thermometer divided into i degrees. When the temperature
has fallen to about 5° above the presumable solidifying point, the vessel
is vigorously and regularly shaken up and down, until the contents are
distinctly turbid and opaque. The thermometer is then closely watched
to observe the maximum temperature of solidification.
Fio. 41.
Fig 45.
1 Mitt. K. techn. Versuchanst, 1889, p. 27 ; 1890, p. 153 ; /. Soc. Chem, hid., 1889, 8, 423 ;
1890, 9, 1671. C/. also Lewkowitsch, Chemical Technology^ etc., vol. i., p. 501.
- Milt. tech?!. Gew. Museums, 1891, p. 57 \ J. S'o:. Chem. hid., 1894, 13, 181, 908.
3 Chem. Rev. Fett-fnd., 1899, 6, li.
176 ANALYSIS IN OIL AND FAT INDUSTRIES
Shukoft" showed subsequently^ that the vacuum jacket is not
absolutely necessary, and that equally good results are obtained when a
test tube 2^-3 cm. wide, fitted with a thermometer, is fixed by means
of a cork into the neck of a wide-mouthed bottle.
Titre tests of the fatty acids are given in Table 26, pp. 150 et seq.
of the previous Section.
3. TJic Colour is an important criterion in the valuation of tallow.
Imported tallows, which are chiefly dealt with on the English market,
are therefore sold under such names as " good colour," " off colour," " no
colour," etc.
4. The Content of Free Fatty Acids in the case of fresh animal fats is
fairly small. Foreign tallows frequently contain 20 per cent, or more of
free fatty acids. In palm oil the free fatty acids often much exceed this
figure. The amount of free fatty acid is ascertained by determining
the acid value (see p. 122).
5. The Yield of Solid Fatty Acids obtainable from tallow by lime
saponification may be ascertained with the help of an empirical Table
compiled by Dalican.- For technical purposes a separate Table for each
class of fats should be prepared by making mixtures of solid and liquid
fatty acids similar to those obtained technically on a large scale, and
determining the titre of the several mixtures of known composition.
Dalican's Table is obviously inapplicable to candle material obtained by
sulphuric acid saponification, and separate Tables must be prepared for
this purpose.^ More accurate results are obtained in the case of
saponification by water and lime (or magnesia) by determining the -
iodine value and calculating it to oleic acid. This method is, however,
unreliable when applied to candle material obtained by sulphuric acid
hydrolysis or by the mixed process, as " iso-oleic " acid also absorbs
iodine.
6. The Yield of Glycerol is determined directly as described in the
Section on " Oils, Fats, and Waxes" (p. 123). This determination is,
however, generally superfluous, as it is sufficient to reckon on a yield of
10 per cent, from neutral fat, and to deduct i per cent, for every 10 per
cent, of fatty acids.*
(6) Testing of Intermediate and Finished Products.
The progress of hydrolysis is watched by determining the unchanged
neutral fat from time to time. An average sample is taken, and in the
case of the sulphuric acid saponification process, boiled with water, and
in the case of the lime or magnesia saponification process with dilute
sulphuric or hydrochloric acid, then allowed to cool, and the cake of
1 Chem. Zeit., 1901, 25, 99.
- Cf. Lewkowitsch, Chemical Technology, etc., vol. ii., p. 641. ^ Ihid., vol. iii., p. 184.
■» Lewkowitsch, The Laboratory Companion to Fats and Oils Industries, Table 5, p. 13.
STEARINE CANDLES Hi
fat taken off and washed free from acid. The acid and saponification
values are then determined.
Exa7nple. — If the saponification value, k, of a sample of tallow taken
from the autoclave water process be 203, and the acid value, a, be 162-2,
then k — a = 201—162-2 = A,o-Z corresponds to the amount of neutral fat
present in the sample. As the saponification value of a neutral tallow
is in round numbers 195, the proportion is : —
195 : 100 = 40-8 \x. X = 20-92.
The percentage of neutral fat in the sample is therefore 20-29, and
the percentage of free fatty acids 100 — 20-92 = 79-08.
The intermediate products are valued according to their solidifying
points, and iodine values (with the above-mentioned limitation).
As regards the Final Products, those obtained by the water, lime,
and magnesia saponification processes are technically known as " saponi-
fication " products, whilst those from the other processes are known as
" distillation " products, since the fatty acids must always be purified by
distillation. Hence in commerce, the terms saponification stearine,
distillation stearine, saponification oleine, distillation oleine, saponifica-
tion glycerin, and distillation glycerin are emplo}ed.
The value of Saponification Stearine depends upon the solidifying
point. The higher this is, the more valuable the candle material. A
definite iodine value shows the quantity of residual oleic acid in the
press cakes. A distinct difference between the neutralisation value and
the saponification value corresponds to the quantity of neutral fat which
has escaped saponification, and has not been pressed out with the oleic
acid. For commercial purposes it is seldom necessary to estimate the
quantities of palmitic and stearic acids separately.
Distillation Steai'ine is also valued according to its solidifying point,
which is generally lower than that of saponification stearine. The iodine
value of a " distillation stearine " forms a measure of the quantity of
"iso-oleic" acid present; the difference between the saponification
value and the neutralisation value shows the amount of stearolactone
present.
A complete examination of distillation stearine comprises, therefore,
the determination of the iodine value, the neutralisation value, and the
saponification value, and the direct determination of the stearic acid.
The palmitic acid is then found by difference. It is thus possible to
distinguish between" saponification stearine "and "distillation stearine"
by means of the iodine value. The iodine value of the former product
seldom exceeds a few units, whereas distillation stearines give iodine
values which lie for the most part between 1 5 and 30.
A considerable amount of neutral fat is contained in the candle
material used for the " composite candles," which consist of a mixture
III M
178 ANALYSIS IN OIL AND FAT INDUSTRIES
of stearine and cocoa-nut stearine. If an accurate determination of the
neutral fat is required, it is best to saponify 50 g. of the sample, and to
estimate the quantity of glycerol obtained.
Adulterants of "stearine" are solid hydrocarbons (paraffin wax,
ceresin), distilled wool fat stearine, also carnaiiba wax, which is
sometimes added to raise the solidifying point of the candle
material.
The presence of these substances is ascertained by the determination
of the unsaponifiable matter. The unsaponifiable matter is examined
as described in the previous Section (p. 139). In this manner paraffin
wax, ceresin, and carnaiiba wax are detected. The presence of
cholesterol indicates an addition of " distilled wool fat stearine."
Candles consisting almost entirely of stearine are generally used in
hot countries, as candles which contain much paraffin wax in addition
to stearine are liable to bend and gutter, in consequence of their low
melting point.
In temperate climates, candles are generally made of mixtures of
stearine and paraffin wax.
Co))iuiercial Oleic Acid — Olcine — is a by-product, and is, as stated
above, placed on the market in two qualities, " saponification oleine "
and "distillation oleine."
Saponification Oleine is generally dark in colour, and if it has not
been freed from "stearine" by cooling, contains considerable quantities
of solid fatty acids. Hence the iodine value of an oleine lies con-
siderably below 90. All neutral fat which has escaped hydrolysis •
in the autoclave process is present in this " oleine " ; its saponification
value is therefore higher than its neutralisation value. All the un-
saponifiable matter contained in the original fat is also present in the
"oleine."
Distillation Oleine obtained in the sulphuric acid saponification
process or by the "mixed process" is a distillation product, and
accordingly represents a bright, transparent oil. It contains, as a
rule, small quantities of solid fatty acids, so that the iodine value of
a distillation oleine, prepared commercially from tallow, lies between
80 and 86.
Before the method of distilling the fatty acids had reached its present
state of perfection distilled oleines contained considerable quantities of
hydrocarbons, which resulted from the decomposition of neutral fat
remaining in the still. Hence it was formerly possible to distinguish
" distillation oleine " from " saponification oleine " by the presence of
hydrocarbons in the former. At present, however, owing to the
improvements in the process of manufacture, the distillation oleine of
commerce is {practically free from decomposition products.
The other by-product. Glycerin, is treated in detail later (p. 198).
PARAFFIN CANDLES 179
2. Paraffin Candles (see also "Mineral Oils," p. 52).
The chemical composition of paraffin wax is not yet definitely known,
and varies with its origin. American paraffin wax may be considered as
consisting of a mixture of hydrocarbons of the ethane series. The
paraffin wax obtained in the lignite industry of Saxo-Thuringia
contains a small percentage of olefines. Hence the iodine values of
the paraffin waxes met with in commerce vary. Paraffin wax obtained
from petroleum must not be taken to be identical with that obtained by
destructive distillation. As a rule, the paraffin wax obtained by
destructive distillation is superior to petroleum paraffin wax in its
commercial application.
Scotch crude paraffin wax is known in commerce under the name of
" scale." This contains varying quantities of impurities, dirt, water, and
hydrocarbons of lower melting point, which consist principally of "soft
paraffin." The latter is commercially known in England as "oil," as it
is valueless to the candle-maker.
There is no definite dividing line between the solid hydrocarbons
and the " oil," as the bard paraffin hydrocarbons pass by gradations
through soft paraffin or lower melting paraffins to " oil." The quantity
of oil which is pressed out in the manufacture depends naturally upon a
number of conditions, such as temperature, pressure, length of time
during which the pressure is applied to the mass, etc. It is therefore
easily understood that a laboratory test for " oil " must be more or less
empirical.
For this reason special tests are laid down between the buyer and
seller in specifications.
The final product of the Scotch paraffin oil industry is sold as " Soft
Paraffin " in case the melting point is below 48° (118° F.). Paraffin wax
of melting point over 48°-9 (120" F.) is termed "Hard Paraffin." The
candle material produced in the Saxo-Thuringian industry has, as a
rule, a melting point of 53°-56° ; material of lower melting point (5o°-52°)
or of higher melting point is but seldom placed on the market.
Apart from colour, transparency, and smell, the most important
characteristic in valuing paraffin wax is the melting point. The melting
point and solidifying points coincide in the case of paraffin wax. A
uniform method for the determination of the solidifying point of
paraffin wax has not yet been agreed upon. The following three
methods are met with in commerce, and are known respectively as
(i) The English test; (2) The American test; and (3) The German
test (Halle specification).
I. TJie English Test. — A test tube of about i in. diameter is filled
to a depth of 2 in. with molten paraffin wax. A small thermometer is
immersed in the mass and the latter slowly stirred, so that the tube and
180 ANALYSIS IN OIL AND FAT INDUSTRIES
its contents cool gradually. The temperature at which the thermometer
remains stationar\' for a short time is taken as the melting point. It is
to be noted that the paraffin wax does not behave like a mixture of
fatty acids, which exhibits a rise of temperature on solidifying. In
the case of paraffin wax the mercury column remains stationar)' for
about half a minute, but no sudden rise of the mercury takes place ;
subsequently the mercury falls gradually. The stationary point is
especially distinct when larger quantities — about 50 g. — are taken for
the determination.
2. The American Test. — A quantity of paraffin wax sufficient to fill
a dish 3f in. in diameter three quarters full is melted. A thermometer
with a round bulb is then immersed into the molten mass, so that only
three-quarters of the bulb is in the paraffin wax. The wax is then
allowed to cool gradually, and the temperature, at which the first sign of
a film is seen to form from the wall of the dish across to the thermo-
meter, is taken as the melting point
3. The German Test. — A beaker about 7 cm. in height and 4 cm. in
diameter filled with water is heated to about yo" , and a small lump of
the sample is thrown on to the hot water, the lump being of such a size
that after melting it spreads out to a disc of about 6 mm. diameter.
As soon as the wax is liquid a thermometer of the special pattern pre-
scribed by the " Verein fur Mineralolindustrie " is plunged into the liquid
so that the horizontal mercury bulb of the thermometer is completely
immersed. At the moment when the paraffin film forms a solid skin
the solidifying point is read off on the thermometer. During this
operation the beaker must be carefully protected from draughts by glass
plates ; also, the paraffin layer must not be cooled by breath from the
mouth.
It is evident that the determination of the melting point by the
American and German methods must lead to very uncertain results.
It is therefore recommended to adopt the English method.
Candles prepared exclusively from commercial paraffin wax are too
soft and bend too easily ; it is therefore necessary to add from 3-15 per
cent, of" stearine " to paraffin wax, according to its melting point.
It has been already pointed out above (p. 173) that "stearine" is
mixed with varying quantities of paraffin wax. The melting point of a
mixture of stearine and paraffin wax cannot be calculated from the
melting points of the components. It is, therefore, alwa\'s necessary for
the control of the manufacture to construct an empirical Table for the
special materials concerned.
The following Tables of this character have been prepared by I. I.
Redwood for mixtures of Scotch paraffin wax and "stearine," and
by W. Scheithauer for mixtures of Saxo-Thuringian paraffin wax and
" stearine."
PARAFFIN CANDLES
181
Table 32.
Melting Points of Candle Material from "Mixed Paraffin Wax"
(Scotch Pyroparaffin) and "Stearine." (I. I. Redwood.)
Paraffin wax.
Per cent.
90
80
70
60
50
40
30
20
10
90
80
70
60
60
40
30
20
10
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Melting point.
°F.
102
102
102
102
102
102
102
102
102
120
120
120
120
120
120
120
120
12'0
120-25
120-25
120-25
120-25
120-25
120-25
120-25
120-25
120-25
125
125
125
125
125
125
125
125
125
130
130
130
130
130
130
130
130
130
132-50
132-50
132-50
132-50
132-50
132-50
132-50
132-50
132-50
"Stearine.'
Per cent.
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
Melting point.
°F.
121
121
121
121
121
121
121
121
121
123
123
123
123
123
123
123
123
123
129-75
129-75
129-75
129-75
129-75
129-75
129-75
129-75
129-75
121
121
121
121
121
121
121
121
121
121
121
121
121
121
121
121
121
121
129-75
]29-75
129-75
129-75
129-75
129-75
129-75
129-75
129-75
Mixture.
Melting point.
'F.
100-0
98-5
100-0
104-5
110-5
111-0
113-5
117-5
119-0
118-0
116-50
114-0
112-0
110-0
109-0
113-0
118-50
119-50
118-50
116-75
114-50
112-25
113-0
118-75
122-0
124-50
127-0
123 0
121-0
119-0
117-50
114-0
111-0
107-0
114-0
117-0
1-28-0
125-50
123-0
121-0
118-50
114-0
109-0
115-50
118-0
130-50
128-50
126-50
124-25
121-0
117-75
119-50
125-25
127-50
182
ANALYSIS IN OIL AND FAT INDUSTRIES
Table 33.
Melting Points of Candle Material from Saxo-Thuringian '• Paraffin
Wax" and • Stearine" (W. Scheithauer.)
ParafiQn wax.
"Stearine."
Mixture.
Per cent.
Helting point.
Per cent.
Melting point.
Melting point.
"C.
-c.
•c.
90-0
36-5
10-0
36-5
66-6
33-3
33-3
66-6
54
39-0
45-75
10-0
90-0
51-75
90-0
37-5
J
10-0
'^
36-5
66-6
33-3
33-3
66-6
54
35-5
47-0
10-0
90-0
■
52-0
90-0
40-75
10-0
'1
54
39-75
66-6
33-3
33-3
66-6
40-5
47-5
10-0
90-0
52-0
90-0
- 45-0
10-0
\
44-0
66-6
33-3
33-3
66-6
54
40-75
48-0
10-0
90-0
52-5
90-0
48-5
J
10-0
y 54
47-5
66-6
33-3
33-3
66-6
45-0
47-75
10-0
90-0
52-5
90-0
>
10-0
54
49-0
66-6
33-3
I 50-0
33-3
66-6
47-0
47-5
10-0
J
90-0
52-5
90-0
54-0
10-0
54
J
53-0
66-6
33-3
33-3
66-6
49-0
47-0
10-0
90-0
52-5
90-0
10-0
\
55-5
66-6
33-3
\ 54
62-0
33-3
56*o
*
66-6
47-5
10-0
90-0
J
52-5
The proportion of stearic acid in paraffin candles is determined by
dissolving 5-10 g. of the sample in petroleum spirit or ether, adding a
few cubic centimetres of alcohol and titrating with normal alkali, using
phenolphthalein as indicator. The number of cubic centimetres of
WAX AND BEESWAX CANDLES 183
alkali used is multiplied by 0-284 and divided by the weight of substance
taken.
3. Spermaceti Candles.
Spermaceti candles are made of refined spermaceti. They are still
used for lighting purposes, although they are, for the most part, super-
seded by the cheaper stearine and paraffin candles. Until recently,
spermaceti candles were always used as normal candles for photometric
measurements in this country.
Spermaceti alone cannot be used for candle-making, as it is too
brittle ; hence beeswax, tallow, " stearine," paraffin wax, or ceresin is
added. The standard spermaceti candles used for photometric work
are only allowed to contain an addition of best air-bleached white
beeswax of melting point 62° ; no other material is admissible, and the
amount of beeswax allowed is between 3 and 4-5 per cent. The
spermaceti itself must melt between 45° and 46°.
The characteristics of spermaceti given in Table 27 of the Section
on " Oils, Fats, and Waxes," p. 153, permit of the detection of adultera-
tion with the above-named materials,
4. Wax Candles, Beeswax Candles.
The wax candles for use in churches in Russia, which account for a
very considerable proportion of the total wax consumption of the world,
must always be made of pure beeswax. The Catholic Church now
allows for ritual purposes, church candles containing 75 per cent, 65
per cent, and even less of beeswax.^ Hence, excepting the candles
destined for Russia, very few "beeswax" candles are met with which do
not contain admixtures. The commonest additions are stearic acid,
tallow and rosin, spermaceti, and, above all, ceresin and paraffin wax.
Vegetable waxes such as carnaiiba wax make beeswax practically
worthless. Beeswax contains no glycerides ; in addition to free fatty
acids of high molecular weight (much cerotic and little melissic acid), it
consists chiefly of myricin (myricyl palmitate), free myricyl and ceryl
alcohols, and, in addition, smaller quantities of hydrocarbons, and also
some unsaturated acids. Crude beeswax has, as a rule, a yellow to
reddish-brown colour. It has the pleasant smell of honey, a fine-grained
structure, and is sufficiently soft at the ordinary temperature to be
kneaded ; at lower temperatures it is brittle. It always contains
imbedded grains of pollen which facilitate its microscopic detection.
When purified by repeated melting over hot water and bleached by
exposure to the sun or by chemical means, white wax is obtained. This
is pure white or pale yellow, inodorous and tasteless, brittle and heavier
than yellow wax, and generally shows a smooth fracture.
1 Cf. Lewkovvitsch, Chemical Technology, etc., vol. iii., p. 337.
184 ANALYSIS IN OIL AND FAT INDUSTRIES
The most important characteristics of pure, yellow beeswax are
given in Table 27, p. 153. It is, however, to be noted that these values
do not hold for Indian waxes (" Ghedda wax"), which give abnormal
values.^ "Ghedda" wax appears to differ from ordinary yellow
beeswax in that it contains ceryl alcohol as the only alcoholic
constituent.
A preliminary indication of the purity of a wax is given by its
melting point, specific gravity, and solubility in chloroform.
The iodine value, which varies from 9- 11 in the case of pure
yellow wax, whereas it is lower (about 4) for white wax, may afford
further information in cases of doubt.
The most important characteristics in the examination of pure
beeswax are the acid and saponification values. The acid value of
yellow wax is from 18-22 (as a rule 19-20); the saponification value is
88-99, hence the difference between the acid value and the saponification
value is 69-79. (This difference was termed by Hiibl the " ether value " ;
the author avoids this term, as it is somewhat misleading.) As the
higher and lower values frequently occur together, the quotient : —
saponification value — acid value
acid value
i.e. " Hiibl's ratio value," varies within narrow limits, namely, between
3-6 and 3-8. For white wax the limits must be somewhat extended,
namely, for the
Acid value ..... to i9-7o-24-oo
Saponification value . . . „ 93-6o-io7-oo
Hiibl's ratio value . . . . „ 2-96-3-97
The method of determining the saponification value is practically
the same as for fats (p. 114), modified, however, by the fact that the
esters of beeswax, as also its more frequently used adulterants (paraffin,
ceresin), are almost insoluble in alcohol. Since these form a protective
coating round the soluble portions, and thus inhibit the action of the
alkali, incorrect results ,may be obtained unless the saponification be
carried out as described below.
For the determination of the acid value, 3-5 g. of beeswax are
warmed for some time with 25 c.c. of 95 per cent, alcohol, and the free
acid then titrated with Nji alkali, using phenolphthalein as indicator.
The saponification value is determined on a separate quantity of 1-5-2
g. with 25 c.c. of an A72 alcoholic solution of potassium hydroxide
prepared with strongest (almost absolute) alcohol. The boiling must
be continued over a wire gauze and under a reflux condenser for at
least an hour, as the saponification is otherwise incomplete.
If the main problem be to ascertain the purity of a beeswax, it is
' C/. Lewkowitsch, Chemical Technology, etc., vol. ii., p. 755.
WAX AND BEESWAX CANDLES
185
sufficient to determine the acid and saponification values. If these
give normal values the specific gravity is determined, and further,
ceresin and paraffin wax are tested for by Weinwurm's method (see
p. 1 86). If these hydrocarbons are absent and the specific gravity lies
within the limits given above, the sample may be pure. The melting
point and also the iodine value should, however, be determined as well.
The following Table gives the characteristics of pure beeswax and
of the usual adulterants found in it (average values) : —
Table 34.
Characteristics of Beeswax and of the usual Adulterants found in it.
Acid value.
Saponiflcation
value.
Ratio value.
Beeswax (yellow)
„ (white) .
Carnatiba wax
Chinese (insect) wax .
Japan wax . ...
Myrtle wax ....
Spermaceti .....
Tallow and tallow stearine .
Stearic acid (commercial)
Rosin .....
Paraffin wax and ceresin * .
19 to 21
19-7 „ 24
2
0
20
3
0
4 to 10
200
130 to 164-6
0
91 to 97
93-5 „ 107
80
80-4
227
208
130
195
200
146-8 to 194
0
3-62 to 3-84
2-96 „ 3-97
39
lb -8
68-3
18-5 to 48
0-126 to 0-191
0
* Commercial paraffin and ceresin are not always quite free from acid.
From these data the following conclusions may be drawn : — If the
saponification value of a sample is below 92 and at the same time the
" ratio value " equal to that of a pure wax, paraffin wax or ceresin is
present.
If the "ratio value" exceeds 3-8, adulteration with tallow, Japan
wax, spermaceti, or other waxes is probable. If, at the same time, the
acid value is below 20, Japan wax is excluded. An abnormally low
" ratio value " (high acid value) leads to the conclusion that stearic acid
or rosin (colophony) is present. The values quoted in the Table show,
however, that more complicated adulterations are possible by the
simultaneous addition of several adulterants. Their presence cannot
be recognised readily by the test just mentioned. Thus, the addition
of a mixture of 37-5 per cent, of Japan wax, 6-5 per cent, of stearic acid,
and 56 per cent, of ceresin, a mixture containing no beeswax whatever,
furnishes perfectly "normal" values. In such cases the adulteration
can be detected, not only by the appearance of the sample (fracture,
taste), but also by the following tests : —
Detection of Glycerides. — If 20 g. of the sample are saponified and
tested for glycerol, a positive result indicates the presence of fats (Japan
wax, tallow).
18G ANALYSIS IN OIL AND FAT INDUSTRIES
Detection of Stearic Acid. — Stearic acid is more readily soluble in
alcohol than the free cerotic acid occurring in beeswax. Hence if i g.
of wax be boiled with lo c.c. of alcohol of 80 per cent, by volume,
allowed to cool, filtered, and water added to the filtrate, the liquid
becomes only slightly turbid in the case of pure wax, whilst any stearic
acid present separates in flocks ; as little as i per cent, of stearic acid
can be thus detected.
It is, however, to be borne in mind that if rosin is also present, this
also dissolves and gives an emulsion with water.^
Detection of Rosin. — The presence of rosin in beeswax is easily
recognised by its taste and stickiness. In contrast to pure beeswax it
adheres to the teeth when chewed. To detect rosin the Liebermann-
Storch reaction (p. 130) is used; its quantitative determination is
carried out by Twitchell's method (p. 195).
Detection of Ceresin and Paraffin Wax. S. Weinwurm's Test.- — 5 g.
of beeswax are saponified with 25 c.c. of N/2 alcoholic potash, the
alcohol evaporated off, 20 c.c. of concentrated glycerol added, and the
solution heated further until all is dissolved. On adding 100 c.c. of
boiling water, genuine beeswax gives a more or less clear, transparent
to translucent solution. If a paper printed with letters of normal size
is placed under the vessel the printing must be perfectly legible. If, on
the other hand, the wax contain 5 per cent, or more of ceresin or
paraffin wax, a turbid solution or a precipitate is obtained which makes
the printing illegible. If the turbidity is but slight, about 3 per cent,
of ceresin may be present. To detect this, a second test is made, 3 per,
cent, of ceresin being added to the wax before saponification. If a
decided turbidity is now obtained, then small quantities of foreign
hydrocarbons must have been originally present; if the turbidity is not
more distinctly marked, the presence of hydrocarbons is not proved.
In presence of 8 per cent, of ceresin or paraffin wax a precipitate is
obtained.
It must, however, be borne in mind that this test is only of a
preliminary character. Moreover, a turbidity does not necessarily
point to the presence of paraffin wax and ceresin, for a beeswax to
which 50 per cent, of carnaiiba wax or insect wax has been added gives
(as the author has shown) just as great a turbidity as one containing
5 per cent, of paraffin wax.
For the quantitative estimation of ceresin or (and) paraffin wax, the
following method of A. and P. Buisine-^ is recommended: — 2-10 g. of
the sample are melted in a small porcelain crucible, the same weight of
1 For a method of detection proposed by Buchner and criticised by Berg, c/. Lewkowitsch,
Chemical Techtiology, etc.^ vol. ii., p. 770.
2 Chem. Zeit., 1897, 21, 519 ; /. Soc. Chem. hid., 1897, 16, 939.
3 Monit. Scient., 1890, Scr. [iv.], 4, 1 134.
WAX AND BEESWAX CANDLES 187
finely powdered potassium hydroxide added, and the whole stirred.
The hard mass resulting on cooling is powdered and intimately mixed
with 3 parts of potash lime for i part of wax, (The potash lime is
prepared from i part of potassium hydroxide and 2 parts of lime.) The
mixture is placed in a test tube or a small pear-shaped flask and heated
in a mercury bath, the temperature being maintained for two hours at
250°. The bath consists of an iron vessel with an air-tight cover
having three openings ; in one of these the small flask is fixed, in the
second a thermometer, whilst in the third a long iron tube is fitted, to
condense the mercury vapour. After cooling, the melt is powdered,
extracted with dry ether, the extract filtered, the ether distilled off,
and the residue (if necessary after a second treatment with ether and
filtering) dried and weighed. The proportion of hydrocarbons in yellow
beeswax varies from I2-5-I4-5 per cent. (Hett and Ahrens found up to
I7'35 P^r cent.). An addition of 3-5 per cent, of ceresin or paraflin
wax can thus be detected with certainty,
Detectio7i of Carnailba Wax. — An addition of carnaiaba wax raises
the specific gravity and the melting point. Carnaiiba wax is not
completely soluble in chloroform, in contradistinction to pure yellow
wax. Weinwurm's test also serves as a good preliminary test. An
incontrovertible proof of the presence of carnaiiba wax is a difficult
problem, and its quantitative determination still more so ; these can
only be effected by an exhaustive examination of both the free and
combined fatty acids. This applies also to the detection of insect wax.
For the detection of the several ingredients of a white wax candle
consisting of a mixture of bleached beeswax, spermaceti, stearic acid,
paraffin (and) or ceresin, and for the detection of adulterants, cf. J.
Lewkowitsch, Chemical Technology, etc., vol, ii., p. yyG, and vol. iii.,
P- 335-
5. Ceresin.
Ceresin is the product obtained by refining ozokerite (earth wax),
a natural bituminous product, found mostly in the neighbourhood of
petroleum springs. The richest pockets of ozokerite are at present
found in Galicia, The refined ceresin varies in colour from dark orange
yellow to almost pure white. It has a specific gravity of 0-9 18-0-922,
melts at 6i°-'j2>'' (higher than paraffin wax), has a conchoidal fracture,
and is not crystalline. Pure specimens are odourless. It is largely
adulterated with paraffin wax and with rosin. Additions of carnaiiba
wax for the purpose of raising the melting point are also made
sometimes.
The melting point of ceresin is much lowered by the addition
of considerable quantities of paraffin wax. For technical purposes the
melting point is still frequently determined by Pohl's method which is
stipulated in specifications. The accuracy of this method has been
188 ANALYSIS IN OIL AND FAT INDUSTRIES
improved by employing Ubbelohde's apparatus {cf. " Oils, Fats, and
Waxes," p. 108).
For the detection of paraffin wax in ceresin, J. Marcusson and H.
Schliiter^ have recommended a method which is said to give approxi-
mately correct results under certain conditions, but which, at present,
stands in need of confirmation.
Ceresin containing rosin has a definite acid value. Unadulterated
ceresins are, however, met with which contain a small proportion of acid,
owing to the sulphuric acid used in the refining process (acid value up
to 4), but samples adulterated with rosin show much higher acid values.
Rosin is detected and estimated in the alcoholic extract as described on
p. 186.
Z.— SOAP.
Salts of fatty acids are termed soaps. A differentiation is made
between salts of alkali metals on the one hand, and salts of the alkaline
earths and heavy metals on the other. In commerce, the term "soap"
refers only to the alkali salts of the non-volatile fatty acids. According
as the base is soda or potash the products are distinguished as hard
soaps (soda soaps) and soft soaps (potash soaps, soft soap). These
soaps are also termed soluble soaps.
The salts of the alkaline earths and heavy metals are also termed
metallic soaps, or water-insoluble soaps {cf. infra).
Soda Soaps.
These are prepared on the large scale by two methods — (i) b\- the
so-called cold process ; (2) by the boiling process (hot process).
For the manufacture by the former process, the vegetable fats of the
cocoa-nut oil group are especially suitable. For their saponification,
concentrated solutions of caustic soda must be used. With the help of
these fats, other fats which are in themselves not readily hydrolysed by
concentrated caustic soda (such as olive oil, tallow, lard) may be
saponified in the cold. The " cold-made " soaps which thus result contain,
of course, all the glycerin, and any salts present as impurities in the
caustic soda, and frequently also free alkali, and even unsaponified fat.
Theoretically, a soap prepared from cocoa-nut oil or palm kernel oil
has the following composition : —
Fatty acid anhydrides
Sodium o.xide (Na^.O) ....
Water and glycerol (by difference) .
loO'Oo per cent.
" Filling " materials are frequently added to these soaps.
' Cliem. Zeit.^ 1907, 31, 348 ; /. Soc. Clum. J>uL, 1907, 26, 491.
54-50
per
cent,
8-86
)»
36-64
5)
SOAP 189
The soaps prepared by the second method (boiling process) are
obtained either by boiling mixtures of neutral oils and fats with caustic
soda solution, or by boiling " fatty acids," which are manufactured on a
large scale, with sodium carbonate and caustic soda. A third process
depending upon the double decomposition of lime soap with soda ash
is in use in a few small soap factories on the Continent. The soap
paste obtained in the boiling process is " salted out" with common salt;
the curd is again boiled to a paste, and then converted into pressed
soap, which solidifies on cooling to a solid mass, so that it can be cut up
into the well-known soap bars and cakes. The glycerol of the neutral
fats passes into the soap lye. Such soaps cannot be prepared with a
higher proportion of fatty acids than 63-64 per cent. The theoretical
composition (taking the mean molecular weight of the fatty acids as
275) is as follows : —
Fatty acid anhydrides . . . 61 -So per cent.
Sodium oxide (Na^O) .... 7-21 ,,
Water and glycerol (by difference) . . 30-99 „
loo-oo per cent.
If it be desired to prepare soaps with a smaller percentage of water,
as in the manufacture of milled toilet soaps, the curd must be deprived of
part of its water (" water of constitution "). If, on the other hand, a
higher proportion of water be desired, additions of solutions of silicate
of soda, soda ash, sodium sulphate, common salt, etc., are made, either
in the soap pan itself, or in special mixing machines. These " run " soaps
represent the cheap household soaps ; their proportion of fatty acids
may be reduced by " filling" to as little as 12-16 per cent.
Further varieties of soda soaps are : —
1. Transparent Soaps, made either by dissolving the soap in alcohol,
distilling off the alcohol, and moulding the gelatinous residue, thus yield-
ing soaps containing a high percentage of fatty acid, or (cheap) " filled "
soaps, rendered transparent by the addition of sugar solution.
2. Soap Powders, Washiiig Powders, " Dry Soap" which are prepared
by grinding soda soaps with soda, etc.
Potash Soaps (Soft Soap).
These are made by boiling neutral fats or commercial " fatty acids "
with solutions of caustic potash, or a mixture of this with potassium
carbonate. These soaps are not salted out, and hence the soft soaps
contain, like the "cold-made" soda soaps, all the glycerol contained in
the neutral fat, together with the excess of alkali, the potassium
carbonate, and any "filling" material which may have been added.
Normal soft soaps cannot be obtained in the soap pan with more than
about 40 per cent, of fatty acids. Hence the theoretical composition of
190 ANALYSIS IN OIL AND FAT INDUSTRIES
a soft soap made from neutral fats or " fatty acids," assuming a mean
molecular weight of 275 for the fatty acids, is as follows : —
Fatty acid anhydrides . . . 38-70 per cent.
Potassium oxide (K.,0) . . . 6-84 „
Water and glycerol (by difference) . . 54-46
»
100-00 per cent.
Potash soaps are frequently '* filled," so that the proportion of
fatty acid in commercial products falls to 25 per cent, and less.
Frequently rosin is introduced, so that the isolated fatty acids include
the rosin acids. The latter are estimated by Twitchell's method
(P- 195).
The number of substances which are openly added to soaps, to
impart to them some useful (real or supposed) property, is enormous.
It must be left to the analyst to decide in each individual case whether
petroleum, paraffin wax, tar oil, sulphur, etc., are to be regarded as
adulterants or not.
In the present state of the soap industry, and in view of the require-
ments of the consumer, it is difficult to say what constitutes
Adulteration.
Rosin (colophony) is a legitimate substitute for fatty acids, as the
alkali salts of the rosin acids possess washing properties. Hence rosin
acids, which are obtained on decomposing a soap with mineral acid, are
generally reckoned together with the fatt}' acids and returned as fatty
acids.
Silicate and borate also possess washing properties ; these substances
must, however, be considered as standing on the border line between
legitimate ingredients and adulterants.
Dyes in soaps must not be considered as illegitimate additions, as
there is a demand for coloured soaps. Provided that the colouring
matter is harmless, no objection need be raised against such an
addition. At the most, the analyst will have to determine whether the
colouring matter contains poisonous metals or not.
Essential Oils in soaps have become almost a necessity. The
quantity contained is generally very small, and, as a rule, such
ingredients do not come within the scope of the analytical examination.
There can, however, be no doubt as to adulteration having taken
place when filling materials or "weighting substances" arc found in a
soap. Starch, clay, talcum, sand, etc., fall under this category.
Naturally, the sand found in a " sand soap," sold as such, cannot be
looked upon as an adulterant.
Raw Materials.
The raw materials of the soap industry arc the neutral fats and
SOAP 191
" fatty acids," which are examined by the methods described in the
foregoing Section. In the " fatty acids " the quantity of neutral fat and
fatty acids is determined {cf. p. 177).
In the following paragraphs the most reliable methods (omitting a
large number of suggestions) for the testing and valuation of commercial
soaps are given. The author has made no attempt to give a general
and complete system for ths analysis of soaps which would include
every possible ingredient, as such a procedure would have but little
value.
Sampling. — In sampling great care must be taken to avoid
errors in the determination of moisture. By exposure to the air soap
dries on the surface, and as soon as a "skin" has formed on the outer
surface of a hard soap the interior is protected against further evapora-
tion. Therefore, in the case of hard soaps the samples for analysis
must be taken from the middle of the piece, the skin being cut away ;
an inspection of the sample will generally indicate how much must be
cut away, as a transverse section shows to what depth the drying has
progressed. Suggestions to take a sample by means of a cork borer or
by cutting out a transverse section, so as to obtain an " average sample,"
lead to incorrect results. If the sample to be tested is fresh, thus contain-
ing at least 30 per cent, of water, a somewhat large quantity is quickly
weighed out (as soap readily loses water in the dry air of a balance
case). For the same reason, the sample should not be sliced before
weighing ; at most, this is permissible only in the case of a milled or of
a dried soap.
In such cases the well-known devices to prevent loss of water during
weighing must be employed.
Similar precautions must be observed in sampling soft soaps. The
sample must be taken from the middle of the soap.
(a) Determination of the Fatty Matter and Total Alkali.
A rapid method, sufficiently accurate for commercial purposes, is the
following : — 5-10 g. of the sample (or 50 g. weighed on a balance which
indicates correctly to centigrams) are accurately weighed out, and
dissolved in hot water in a beaker or a porcelain dish, the liquid being
stirred constantly with a glass rod to prevent the caking of the soap at
the bottom of the vessel. After adding a few drops of methyl orange
an excess of standard sulphuric acid (or in case chlorides and sulphates
are to be determined, dilute nitric acid) is added, and the liquid heated,
with constant stirring, until the separated fatty acids have liquefied.
About 5 g. (or 20 g. for 50 g. of soap) of dry beeswax or paraffin wax,
weighed accurately in a tared watch-glass (which is afterwards used for
weighing the fatty matter), are added, and the liquid again heated until
the mixture of fatty acids and wax has separated on the surface of the
192 ANALYSIS IN OIL AND FAT INDUSTRIES
aqueous layer as a clear, transparent layer of oil, free from solid particles.
(If it be known that the fatty acids solidify to a hard mass, the addition
of wax, etc., is, of course, superfluous.) The glass rod is rinsed with hot
water, and the liquid again heated until the fatty substance forms a
uniform mass. The source of heat is then removed and the vessel allowed
to cool. Any white precipitate found on the bottom of the vessel
indicates the presence of silicate or of " filling " materials, which are
insoluble in mineral acid.
The solidified cake of fatty matter is lifted off by means of a
platinum spatula, rinsed with cold water, and placed on filter paper.
Any remnant of fatty matter adhering to the walls of the vessel are
carefully scraped off and added to the main portion. The cake is dried
with filter paper and brought on to the same watch-glass which was
used before, bottom side upwards, and allowed to dry in a desiccator
and weighed. (For the control of the manufacturing process, for which
purposes 50 g. should be taken, it is sufficiently accurate to weigh at
once after drying with filter paper, but care must be taken that all water
present in crevices of the cake are removed by filter paper.) If the cake
has crevices enclosing water and perhaps even acid, which occurs only
when the mass has not been heated sufficiently long, the cake must be
melted over water, allowed to solidify, and again treated as before.
The weight of the beeswax or paraffin wax is deducted from
the weight thus found, and the difference is reckoned as fatty matter;
when no further examination is required, it is generally returned
as fatty acids ; this is, however, only correct if the absence of neutral
fat, wax, and unsaponifiable matter has been proved. Rosin acids are
included in the fatty acids, except in cases where a separate deter-
mination of rosin acids is required. The acid liquid is filtered,
the excess of mineral acid titrated back with standardised alkali, and
the total alkalinity thus found.
Any soluble fatt)' acids present in the soap pass to some extent
into the acid liquid ; as a rule they are neglected, except when cocoa-
nut oil or palm kernel oil soaps are under examination. In such cases
it is best to work with concentrated solutions, or, if permissible, to add
common salt, which renders the bulk of these acids insoluble, so that
the dissolved portion may be neglected. If great accuracy is required,
the soap is decomposed under ether ; all the fatty acids are thus
obtained in ethereal solution as they are liberated. A less accurate
method is to titrate the aqueous solution to neutralit)- with methyl
orange, then to add phenolphthalein, and to titrate again with Njio
alkali. In this case the alkali used for the second titration is calculated
to caprylic acid, CyH^^O.^, molecular weight 144, and the amount thus
found is added to the main portion of the fatt\' acids.
A considerable number of methods supposed to increase the
SOAP 193
accuracy of the determination have been suggested. In the author's
opinion, however, they only comph'cate the analysis without offering any
advantage.
If the absence of neutral fat, wax, and unsaponifiable matter (p. 196)
has been proved, the fatty material is returned as fatty acids. In
a complete soap analysis this amount is multiplied by 0-9675 to convert
it to anhydride.
The higher the percentage of fatty acids, the more actual soap is
present. A comparison of the analytical results with the theoretical
compositions of soaps given above will furnish a useful guide in the
valuation of a sample,
(b) Combined Alkali, Free Caustic Alkali, and Alkaline Salts.
Free Fatty Acids.
The total alkali is the sum of the several amounts of alkali present
in the soap, as (i) alkali combined with fatty and rosin acids termed
"combined alkali"; (2) free caustic alkali; (3) alkali as carbonate,
silicate, or borate.
1. The Combined Alkali is generally found by difference, ie. by
subtracting the sum of the amounts of alkali found under (2) and (3)
from the total alkali. It can, however, be determined directly by
titrating the alcoholic solution with methyl orange, after having made it
neutral to phenolphthalein. This may be done as a check, or to avoid
the separate determination of alkali present as carbonate, silicate,
or borate, as the latter can then, of course, be determined by difference,
2. Free Caustic Alkali. — A preliminary test is first made by
placing a drop of phenolphthalein on to a freshly cut surface of the
soap. A red colour indicates the presence of free sodium hydroxide;
if the soap is moist the red colour may be produced also by carbonate,
silicate, or borate, but if it has been dried these salts produce no colora-
tion. In order to separate the free caustic alkali from alkaline salts,
part of the sample is dissolved in absolute alcohol and filtered. The
alkaline salts remain on the filter, so that the alcoholic filtrate can then
be tested with phenolphthalein.
Soaps which have been properly manufactured should not contain
free alkali ; this holds especially for toilet soaps. As great care
and experience are necessary in the process of " filling," in order
to produce a soap practically free from excess of alkali, most commercial
soaps, especially household soaps, contain an excess of free alkali. If
this quantity be very small, the free alkali becomes converted to
carbonate by exposure to the air, so that in some cases no free
alkali is found, especially if the outer layer only is tested.
Free caustic alkali is estimated quantitatively^ by dissolving 10-30 g.
1 Hope, C/ietn. News, 1 88 1, 43, 219,
III N
194 ANALYSIS IN OIL AND FAT INDUSTRIES
of the sample in hot absolute alcohol in a loosely closed flask (to
avoid the absorption of atmospheric moisture). Soaps containing much
moisture must be partially freed from water, care being taken to exclude
air, to avoid absorption of carbon dioxide. The hot solution is rapidly
filtered, so that the soap does not separate out as a gelatinous mass on
the filter ; when the operation is carried out with care, a hot-water funnel
is unnecessary. The filter is washed with absolute alcohol and the
filtrate collected in a flask. Phenolphthalein is then added, and the
solution titrated with A710 hydrochloric acid.
In some cases the alcoholic soap solution may react acid to
phenolphthalein. This is due to the presence of an acid salt (distearate,
dipalmitate, dioleate), in consequence of faulty fitting, or also to
intentional addition of fatty acids to the soap with the object of
neutralising the free alkali. The quantity of Njio alkali necessary to
neutralise the solution is calculated to free fatty acids in terms of oleic
acid.
3. Carbonate, Silicate, and Borate. — The residue remaining on
the filter consists of carbonate, silicate, and borate, together with other
insoluble substances added as filling materials, such as starch, talcum,
dyes, etc. (For a complete examination of this residue, see p. 197).
For the determination of the alkali contained in the alkaline salts, the
residue is washed on the filter with cold water {cf. (e) i, p. 197). The
alkali in the filtrate is determined by titration with normal acid, using
methyl orange as the indicator, and is calculated to Na.^O.
(c) Determination of Water.
The direct determination of water in a soap is, as a rule, unnecessary.
In the case of genuine soaps it is sufficient for all practical purposes to
calculate the fatty acids to anhydrides and to add the quantity of alkali
found in the several forms ; the water is then found by difference.
The direct determination of water is therefore carried out only in
exceptional cases. For this purpose the soap is introduced in thin
shavings into a porcelain dish, weighed with a glass rod, so that from
time to time the dry skin, which prevents the evaporation of water from
the interior layers, can be broken. This is especially necessary in the
case of highly " run " soaps.
For the valuation of a sample of soap it is generally sufticient to
carry out tests (a) to (c). Further tests include the examination of the
fatty matter and the detection and estimation of other ingredients of
the sample.
(</) Examination of Fatty Matter ("Soap Stock")-
Assuming no wax, etc., has been used in the separation of the fatty
matter, this can be used at once for further examination. The fatty
SOAP 195
matter may contain in addition to fatty acids: i. Rosin acids;
2. Neutral fat ; 3. Unsaponifiable matter.
I. Rosin Acids- — These are determined by Twitchell's method/ as
the author has shown that the older methods proposed by Barfoed and
Gladding and others, and the modifications of these methods, give
unreliable results.
E. Twitchell's method depends upon the property of the aliphatic
acids that they are converted into esters by treatment with hydrogen
chloride gas in alcoholic solution, whereas rosin acids under the same
treatment undergo only a very slight alteration, abietic acid separating
from the solution.
For the determination, 2-3 g. of the mixed fatty and rosin acids are
weighed out accurately in a flask and dissolved in ten times their
quantity of absolute alcohol. The use of absolute alcohol is indispens-
able, as esterification is incomplete in 90 per cent, alcohol. The flask
is immersed in cold water, and a current of dry hydrogen chloride is
passed through the liquid. After about three-quarters of an hour,
when the gas is passing through the liquid unabsorbed, the operation
is finished. In order to achieve as complete esterification as possible,
the flask is allowed to stand for an hour. During this time the ethyl
esters and the rosin acids rise to the surface as an oily layer. The
contents of the flask are diluted with 5 vols, of water, and heated until
the aqueous solution has become clear. The analysis can then be
completed either volumetrically or gravimetrically.
(a) Volumetric Method. — The contents of the flask are transferred
to a separating funnel, and the flask rinsed out several times with ether.
After shaking well the acid layer is drawn off, and the ethereal solution,
which contains the ethyl esters of the fatty acids and the unchanged
rosin acids, is washed with water until the hydrochloric acid is
completely removed. Then 50 c.c. of alcohol are added to the
solution, and it is titrated with normal alkali, phenolphthalein being
used as the indicator. The rosin acids combine at once with the
alkali, whilst the ethyl esters remain almost unchanged. The combin-
ing weight of the rosin acids is taken as 346 ; thus the number of
cubic centimetres of normal alkali used in the titration multiplied by
0-346 gives the quantity of rosin acids in the sample.
(b) Gravimetric Method. — The contents of the flask are mixed with
some petroleum spirit boiling below 80°, and transferred to a separating
funnel, the flask being rinsed out with petroleum spirit. The petroleum
layer should amount to about 50 c.c. After shaking, the acid solution
is drawn off, the petroleum layer washed once with water, the water
drawn off, and 50 c.c. of an aqueous solution of potassium hydroxide
containing 0-5 g. of potassium hydroxide and 5 c.c. of alcohol are added.
' J. Anal, and Applied Cheni., 1891, 5, 379 ; J. Soc. Chem. Ind., 1891, 10, 804.
196 ANALYSIS IN OIL AND FAT INDUSTRIES
The rosin acids are extracted by the dilute alkahne solution, forming
soaps, whilst the ethyl esters still dissolved in the petroleum spirit float
on the surface. The soap solution is drawn off, decomposed with
hydrochloric acid, and the separated rosin acids are weighed, cither
directly on the filter, or preferably after extraction with ether and
evaporation of the ether. The residue gives the quantity of rosin acids
present in the sample.
Of all the methods hitherto proposed for the estimation of rosin
acids, Twitchell's method gives the best results. These must not,
however, be considered as strictly accurate, as the author has shown in
an exhaustive investigation of the volumetric and gravimetric methods
that the results are only approximate.^
2. Neutral Fat. — A properly manufactured soap will seldom
contain unsaponifiable fat. In case neutral fatty matter has been
purposely added to the finished soap, as in the case of " superfatted "
soaps (olive oil, or, in certain toilet soaps, wool wax), it is obtained
together with the unsaponifiable matter. The neutral fat must then be
separated from the unsaponifiable matter.
The neutral fat plus unsaponifiable matter can be obtained directly
from the sample by dissolving a weighed quantity in water or alcohol,
titrating with normal alkali in the presence of phenolphthalein to
neutralise any free fatty acids, and then extracting the soap solution as
described in the Section on " Oils, Fats, and Waxes," p. 124.
The residue of the ethereal solution consists of neutral fat plus
unsaponifiable matter. The separation of the two components is
effected by saponifying and extracting again with ether.
If no unsaponifiable matter be present, the ether residue consists
essentially of neutral fat ; otherwise the neutral fat is found by
difference, or it may also be ascertained directly by isolating the fatty
acids and calculating the quantity found to glycerides.
A complication occurs when the soap contains wool wax. If this
ingredient is suspected, the ether residue must be saponified with dilute
alcoholic potash on the water-bath, in order to obtain at least a portion
of the wool wax in the form of unsaponifiable matter, which can then be
examined and irlcntified.
3. Unsaponifiable Matter. — This is determined together with the
neutral fat, as described. In case no neutral fat be found, the whole of
the ether residue is taken as unsaponifiable matter. This is examined
as described in the Section on " Oils, Fats, and Waxes," p. 139.
Besides the substances given on p. 139, the possibility of the
presence of vaselin, petroleum hydrocarbons, naphthalene, parafifin wax,
wool-fat hydrocarbons, etc., must be taken into account.
The examination of the fatty acids themselves (after separating the
' J. Soc. Chein. Ind., 1 893, 12, 504.
SOAP 197
rosin acids, neutral fat, and unsaponifiable matter) is also carried out as
described in the Section on " Oils, Fats, and Waxes."
(e) Substances Insoluble in Alcohol.
The determination of all the substances which are insoluble in
alcohol is conveniently combined with the estimation of free caustic
alkali (p. 193), the insoluble residue being collected on a previously
dried (at 100') and weighed filter, and then weighed after again drying
at 100°.
Good soaps generally give a negligible residue. Only the toilet
soaps prepared by the " alcohol process " are quite free from insoluble
substances.
The residue on the filter may consist of: —
1. Water-soluble substances, such as chloride, sulphate, carbonate,
silicate, and borate of the alkali metals.
2. Mineral substances insoluble in water, such as colouring matters,
*' filling " and " weighting " materials such as talcum, etc.
3. Organic substances, especially starch, dextrin, gelatin (Carragheen
mucilage).
1. Water-soluble Substances. — The residue on the filter is washed
with f^/(a^ water, so that any gelatin present does not pass into solution.
The presence of silicate will have been already detected in the deter-
mination of the fatty matter when decomposing the soap by acid (see
above under (a)). The silica can be determined at this stage, assuming
that no other substances insoluble in water are present, by acidifying
the filtrate with hydrochloric acid, after determining the total alkali by
titration (see (d) 3) and evaporating to dryness in the usual way. The
filtrate from the precipitated silica can be examined for boric acid.
In case boric acid is absent, carbonate and silicate may be found
from the total alkali as estimated by titration, and the silica as found by
weighing. If boric acid is also present and its quantity is to be
determined, it is best to divide the solution into three parts. In the
first the carbonic acid is determined, in the second the silica, and in the
third the total alkali by titration.
Chlorides and sulphates are best determined in aliquot parts of the
acid liquid obtained after separating the fatty matter as described under
(a). In this case, as stated above, nitric acid must be used for the
decomposition of the soap.
2. Substances Insoluble in Water are incinerated to remove
organic matter, and the residue weighed. The ash is examined
qualitatively and quantitatively in the usual way.
3. Organic Matter. — The microscopic examination of the total
residue insoluble in alcohol may furnish valuable information.
Starch can be detected in this manner ; the microscopic examina-
198 ANALYSIS IN OIL AND FAT INDUSTRIES
tion may be confirmed by the iodine test. If a quantitative examination
is required, the starch is converted to glucose. The residue insoluble in
alcohol is washed on the filter with cold water to remove substances
soluble in water, and dextrin, and is then boiled with dilute sulphuric
acid, the water being replaced as it evaporates. The liquid is neutralised
with potassium carbonate, filtered, and the glucose determined by
Fehling's solution.
Dcxtriri is removed by cold water together with the soluble salts.
It is determined by precipitation with alcohol. This is best done in a
small beaker weighed together with a glass rod. The liquid is
vigorously stirred so that all the dextrin settles out on the sides of the
beaker. The aqueous solution is then decanted, the residue washed
with alcohol, and determined by weighing after drying at ioo°.
Gelatin is removed by washing the residue insoluble in alcohol with
hot water. The filtrate is then tested with tannic acid to corroborate
the presence of gelatin.
(/) Other Substances which occur in Soaps.
1. Glycerol. — The small quantities of glycerol left behind in hard
soaps prepared by the boiling process can be determined with accuracy
only by working with a large quantity of soap. On decomposing the
soap with mineral acid, the glycerol passes into the aqueous solution ;
this is examined by the method described below (p. 202) for the
"determination of glycerol in soap lyes." From the quantity of glycerol
found a conclusion may be drawn as to whether a hard soap has been
prepared by the cold process or not. In this case about 5 per cent, of
glycerol will be found. The absence of glycerol in a soft soap proves
that the soap has been manufactured from " fatty acids."
Considerable quantities of glycerol are added to certain toilet soaps
in the milling process. Glycerol must, in virtue of its cosmetic pro-
perties, be considered a valuable constituent of such soap. It is determined
by dissolving the soap in water, separating the fatty matter by means
of a mineral acid, and filtering. The filtrate is neutralised with barium
carbonate, evaporated to a syrup, and the residue extracted with a
mixture of 3 parts of 95 per cent, alcohol and i part of ether. The
alcoholic solution is filtered, evaporated on the water-bath to a small
volume, and finally dried in a desiccator. The glycerol in the crude
glycerin thus obtained is then estimated by the acetin method (p. 123).
In case a soap also contains sugar, the sugar must first be removed.
2. Sugar (Saccharose) is found in considerable quantities (up to 25
per cent, and more) in cheap, transparent soaps. The determination of
the cane sugar is best effected by boiling the filtrate obtained in (^^),
or an aliquot portion, with dilute sulphuric acid, to invert the sugar,
then making the solution alkaline, and heating with Fehling's solution.
SOAP 199
after diluting considerably to prevent oxidation of the glycerol. The
cuprous oxide which separates out is determined in the usual way and
calculated to cane sugar. If the quantity of sugar is considerable, it
may be determined polarimetrically.
If glycerol and sugar are present simultaneously, they are separated
by the method of E. Donath and J. Mayrhofer,i ^vhich consists in adding
a sufficient quantity of slaked lime to combine with the sugar, then an
equal quantity of washed and ignited sand, evaporating to a syrup,
powdering the residue after cooling, and extracting in a closed flask
with 80-100 c.c. of a mixture of equal volumes of alcohol and ether.
The solution will then contain the glycerol free from sugar, and the
glycerol present is determined as in (i).
3. Carbolic Acid. — The determination of "carbolic acid" (phenol
and cresols) in carbolic soaps is carried out with sufficient accuracy by
the following method (Lewkowitsch) : —
A considerable quantity of the sample (about 100 g.) is weighed out,
dissolved in hot water, and sufficient sodium hydroxide solution added
to make it strongly alkaline. The soap is then salted out with common
salt, the curdy soap filtered off, and the soap washed with salt solution.
The solution, which now contains the phenol and cresols as sodium
salts, is evaporated down, and any dissolved soap is precipitated by a
further addition of common salt. The solution is filtered again, evapor-
ated down to a small volume, introduced into a graduated stoppered
cylinder of 50-100 c.c. capacity, and common salt added until some
remains undissolved ; the solution is then acidified with sulphuric acid.
The volume of the separated phenols is read off, and the number
of cubic centimetres is reckoned as equivalent to the same number
of grams.
If greater accuracy be required, the separated phenols are extracted
with ether, the ether evaporated off, and the phenol and cresols
determined by the methods described in the Section on " Coal Tar,"
Vol. ii., part ii., pp. Sii e^ seq.
Metallic Soaps.
These are either salts of the fatty acids or of rosin acids, or mixtures
of both, as, for instance, the driers described on p. 163. To this class
of soaps belong the Lend Plasters, chiefly lead oleate ; Aluminiu7n
Oleate, which is used to thicken lubricating oil ; Lime Soaps, which
are used in the manufacture of lubricating greases ; Magnesium Oleate,
used in petroleum spirit solution by dry-cleaners as a protection against
the generation of electric sparks ; and, finally, Zific, Lron, Chromium,
and Copper Soaps, used in anti-fouling and anti-rusting paints.
For analysis, the metallic soaps are decomposed by a suitable
1 Z. anal. Chem., i88l, 20, 383-
200 ANALYSIS IX OIL AND FAT INDUSTRIES
mineral acid (hydrochloric, nitric, sulphuric), the fatty and rosin acids
being obtained as an oily layer, or, if the salts are decomposed under
ether (which is frequently the more suitable method), the acids pass
into the ether layer and the metal into the acid solution. The separated
fatty and rosin acids are examined as described above,
i7/.— GLYCERIN.
The glycerins met with in commerce are classified as : i. Crude
glycerin ; 2. Distilled glycerin ; Dynamite glycerin ; 3. Chemically pure
glycerin.
I. Crude Glycerin.
Three kinds of crude glycerin are distinguished in commerce : (a)
Crude saponification glycerin ; {/>) Crude distillation glycerin ; (c) Soap-
lye crude glycerin ; Soap crude glycerin.
(a) Crude Saponification Glycerin.
This is a product of the autoclave process (see p. 173). It is
evaporated down to a sp. gr. of 1-240- 1-242, and sold as " 28° Be. saponi-
fication glycerin" or "crude candle glycerin." It has a pure sweet
taste, and varies in colour from bright yellow to dark brown. It gives
only a slight precipitate with lead acetate, and scarcely any turbidity
with hydrochloric acid. The valuation of this glycerin comprises the
determination of the ash, which should not exceed 0-3-0-5 per cent., the
determination of the glycerol, and of the organic impurities.
The glycerol is best determined by the acetin method as described
in the Section on "Oils, Fats, and Waxes" (p. 123). Of the oxidation
methods, only Hehner's modification of the bichromate method can
be recommended. The author has, however, shown that this method
gives too high a percentage, especially in the case of impure glycerins.^
Since, nevertheless, the bichromate method is still frequently used
in commercial analysis, it may be described here. The following
normal solutions are required : (i) A solution of potassium bichromate
containing 74-86 g. K^Cr^Oy per litre. Hehner recommends the
addition of 150 c.c. of concentrated sulphuric acid before the solution is
made up to 1000 c.c. The author considers it preferable to keep the
unacidified solution as a stock solution, and to add the sulphuric acid
only at the time of the experiment. The actual oxidising value of the
solution must be determined by titrating a known solution of ferrous
sulphate or pure ferrous ammonium sulphate, or pure iron wire. (2)
Solution of ferrous ammonium sulphate, containing about 240 g. per
litre. (3) A bichromate solution, prepared by diluting 100 c.c. of
> Analyst, 1903, 28, 104.
GLYCERIN 201
solution (i) to looo c.c. The solution (2) must correspond accurately
to the strong bichromate solution of which i c.c. is equivalent to o-oi g.
of glycerol.
For the determination about 1-5 g. of crude glycerin is accurately
weighed out into a 100 c.c. flask, diluted with water, silver oxide added
(or copper sulphate and potassium hydroxide solution), and after
standing for a short time a few drops of lead acetate are added and the
whole made up to 100 c.c. After filtering, 25 c.c. of the solution are
transferred to a beaker, previously cleansed with concentrated sulphuric
acid and potassium bichromate, and 40 c.c. of the concentrated
bichromate solution are added. As the bichromate solution is un-
avoidably a concentrated one, it is necessary not only to measure it
with great care, but also to observe the temperature of the solution.
Hehner states that this bichromate solution expands 0-05 per cent, per
degree. The author avoids corrections by keeping the solutions at
normal temperature in a large water-bath until the titration is finished.
Then 25 c.c. of concentrated sulphuric acid are added, the beaker is
covered with a watch-glass, and placed for two hours in boiling water.
The excess of bichromate is then reduced with an excess of ferrous
ammonium sulphate solution, and the excess of the latter finally titrated
back with the dilute bichromate solution, potassium ferricyanide being
used as indicator.
The glycerol content of commercial samples varies, as a rule, between
85 and 90 per cent.
Organic Impurities are determined quantitatively by heating a few
grams gradually to 160° in a platinum dish in a drying oven. Rapid
heating tends to cause the formation of polyglycerols, which of course
lead to incorrect results. It is best to moisten the glycerin from time
to time with a few drops of water, so that the glycerol may evaporate
with the water. The residue is dried to constant weight. The amount
thus found is the sum of the ash and organic impurities. The ash is
found by incineration, and subtracted from the total residue found.
Crude glycerin obtained by the fermentation process is also some-
times termed " saponification glycerin " ; it should be noted that it
contains, as a rule, a considerably larger amount of ash and organic
impurities.^
(6) Crude Distillation Glycerin.
This crude glycerin is obtained from the acid water resulting from
the acid saponification process. The solutions are evaporated down to
a sp. gr. of I -240- 1 -242. The crude glycerin has generally a bright
yellow colour and a sharp astringent taste ; when rubbed on the hand it
has an unpleasant odour. As a rule it contains 84-86 per cent, of
^ CJ. Lewkowitsch, Chemical Technology, etc., vol. iii., p. 332.
202 ANALYSIS IN OIL AND FAT INDUSTRIES
glycerol. The ash generally varies from 2-3-5 P^^ cent. The per-
centage of glycerol can be determined with greater accurac)- by the
acetin method than by oxidation. This crude gl)'ccrin gives a decided
precipitate with lead acetate ; on addition of hydrochloric acid a marked
turbidity is generally obtained (fatty acids).
A product of a similar character is the gl)'cerin obtained by
Twitchell's process (p. 173).
(c) Crude Soap-lye Glycerin ; Crude Soap Glycerin.
This glycerin is obtained from waste soap-lyes. The specific gravity
of the commercial product should not be below 1-3, the content of
glycerol should be at least 80 per cent, and the proportion of salts
should not exceed 10-5 per cent.
The percentage of glycerol is best determined by the acetin method
in preference to the bichromate method (p. 200).
For the determination of the ash, 3-5 g. are slowly incinerated in a
platinum dish over a small burner. When the bulk of the glycerol has
been driven off, the dish is more strongly heated ; a voluminous
carbonaceous residue remains in the dish. The organic matter is then
burnt off, care being taken that no sodium chloride volatilises. The
residue, which contains some carbon, is exhausted with water, and the
filtrate evaporated in the platinum dish on a water-bath. This residue
must be white ; it is heated to dryness (not over 400° to avoid volatilisa-
tion of sodium chloride), and weighed. The carbon residue is burnt, and
the residual ash is also weighed ; this is especially necessary when the
sample contains lime.
Crude glycerin which contains sulphates and thiosulphates is
almost worthless to the refiner ; the qualitative detection of these sub-
stances is therefore of importance.
Recently an International Committee, consisting of manufacturers
and some analytical chemists, has published, under the title of " Inter-
national Standards for the Analysis of Crude Glycerin," somewhat
more detailed methods of examining crude soap-lye glycerins,^
2. Distillation Glycerin ; Dynamite Glycerin. {C/. the
Section on " Explosives," Vol. ii., part i., p. 490.)
These glycerins are obtained from the above-described crude
glycerins by distillation.
The distilled glycerins vary in colour from yellow to almost white.
Their proportion of glycerol varies according to the specific gravity,
which generally lies between 1-220 and 1-260; it can be found approxi-
mately from the specific gravity {cf. Table 35, p. 205). As, however,
» J. Soc. C/iem. Ind., 191 1, 30, S56 ; 1912, 31, 1084 ; 1913, 32, 1039-
GLYCERIN 203
these glycerins contain a little ash, it is necessary in accurate analyses
to determine the glycerol by the acetin method (or by an oxidation
method, such as the bichromate or even the permanganate method,
p. 207). In this case also the oxidation methods easily lead to high
results. Dynamite glycerin is a special quality of distilled glycerin
which has a specific gravity of from i-26i-i-263. The colour varies from
deep yellow to bright pale yellow. From a large number of specifications
regulating the conditions of sale of this glycerin, the author has
extracted the following requirements : —
(a) Specific Gravity. — This must not be less than 1-261 at 15-5°.
(b) Liine^ Magnesimn, and Aluviina must be absent.
(c) Chlorides may only be present in traces. i c.c. of glycerin
diluted with 2 c.c. of water must not give a decided milky turbidity with
silver nitrate.
(d) Arsenic. — Only traces are permitted. As the Gutzeit test
(p. 208) is too sensitive, the following method is used. The sample is
made just alkaline with a very small quantity of ammonia, and silver
nitrate is added when no milky turbidity should be observable. An
excess of ammonia is, to be avoided, as silver arsenite is soluble
in ammonia.
(e) Foreign Organic Matter. — i c.c. of the sample is diluted with 2
c.c. of water, and a {&w drops of a 10 per cent solution of silver nitrate
are added. On standing for ten minutes there should be no brown or
black coloration.
(f) Total Residue. — This is determined as described above (p. 201).
(Polyglycerols).
(g) Free Acid. — The glycerin must not redden blue litmus paper.
Volatile fatty acids are detected most readily by the pleasant odour
emitted (recalling that of pine apple) on warming the sample
with alcohol and concentrated sulphuric acid. On diluting i c.c. of the
sample with 2 c.c. of water, and adding concentrated hydrochloric acid,
no turbidity should be noticeable.
(h) Nitration and Separation Test) — A commercial sample may
pass all the above-mentioned tests satisfactorily and yet be unsuitable
for the manufacture of nitroglycerin. Its suitability for this purpose
must, therefore, be especially ascertained by the following method, which
is based upon the large scale process. A mixture of i part by weight
of fuming nitric acid of sp. gr. 1-5 with 2 parts by weight of pure
concentrated sulphuric acid of sp. gr. 1-845 is prepared, and allowed to
cool in a closed vessel, and 375 g. of this mixture are weighed into
a beaker of about 500 c.c. capacity ; a thermometer which serves
as a stirrer during the nitration is introduced, and the beaker is placed
in a capacious vessel of cold water. The water is kept circulating by
^ Lewkowitsch, Chem. Zeit., 1895, 19, 1423.
204 ANALYSIS IN OIL AND FAT INDUSTRIES
passing it through a stout rubber tube carefully laid on to the sides of
the cooling vessel. The water is allowed to run away by overflowing
the vessel. It should be carefully noted that the rubber tube must be
securely attached to the tap if the nitration is carried on near the water-
supply tap, as it may easil\- happen that it is thrown off the tap owing
to a sudden alteration of pressure in the supply pipe. If any water
is thrown into the nitration mixture, the temperature may easily rise
to danger point. The safest plan is therefore to use a thin-walled
beaker, so that in case of emergency the thermometer may be quickly
pushed through the bottom.
When the temperature of the acid mixture has fallen to 12^-15^
50 g. of the dynamite glycerin to be tested is weighed out into a lipped
beaker and allowed to fall, drop by drop, into the acid, whilst continually
stirring with the thermometer. The temperature should be read after
the addition of each drop. As this operation is not without danger, it
is best for an unpractised experimenter to have the process demonstrated
to him. If this be impossible the nitration should be performed very
slowly and exactly as described, that is, with continual stirring to avoid
any local overheating, taking care that no further glycerin be added,
until the temperature has fallen to 25°. A temperature of 30' must
never be exceeded. A practised operator will, of course, proceed much
more quickly.
When all the glycerin has been introduced the stirring is continued
until the temperature falls to 15°. The mixture of nitroglycerin and
acids is then transferred to a perfectly dry separating funnel. (It is
best to rinse out the separator with concentrated sulphuric acid
beforehand.)
If the glycerin is of good quality, the nitroglycerin separates
quickly, floating on the acid as an oily, somewhat turbid layer. The more
rapidly the separation into two layers with a sharply defined dividing
line takes place, the better is the glycerin. If slimy or flocculent
particles remain suspended in the nitroglycerin, or the separation
is incomplete after five to ten minutes, or if the dividing line is indistinct
in consequence of a cloudy intermediate layer, the gl)cerin is unsuitable
for the manufacture of nitroglycerin.
In the case of a very bad glycerin no separating line at all can be
observed, and the nitroglycerin appears honeycombed with cellular
matter which separates out only after many hours' standing. Such a
glycerin must of course be rejected.
In consequence of the danger attending this test, it has been
proposed to reduce the quantity of glycerin taken for the determination
to 15 g. This should, however, be the lowest permissible limit, as the
results of the nitration become absolutely unreliable when as little as
10 g. are taken.
GLYCERIN
205
Table 35.
Specific Gravities of Aqueous Solutions of Chemically pure Glycerin.
Lenz.
Strohmer.
Gerlach.
Nicol.
Glycerol.
Sp. gr. atl2'tol4°C.
Sp. gr. at 17°-5C.
Sp. gr. atl5°C.
Sp. gr. at 20° C.
Sp. gr. at 20° C.
Per cent.
Water at 12° =1.
Water at 17° -5 = 1.
Water at 15°= 1.
Water at 20° = 1.
Water at 20°= 1.
100
1-2691
1-262
1-2653
1-2620
1-26348
99
1-2664
1-259
1-2628
1 -2594
1-26091
98
1-2637
1-257
1-2602
1-2568
1-25832
97
1-2610
1-254
1-2577
1-2542
1-25572
96
1-2584
1 -252
1-2552
1-2516
1-25312
95
1-2557
1-249
1-2526
1-2490
1-25052
94
1-2531
1-246
1-2501
1-2464
1-24790
93
1-2504
1-244
1-2476
1-2438
1-24526
92
1-2478
1-241
1-2451
1-2412
1-24259
91
1-2451
1-239
1 -2425
1-2386
1-23990
90
1-2425
1 -236
1-2400
1-2360
1-23720
89
1-2398
1-233
1-2373
1 -2333
1-2.3449
88
1-2372
1-231
1-2346
1-2306
1-23178
87
1-2345
1-228
1-2319
1-2279
1-22907
86
1-2318
1-226
1 -2292
1-2252
1-22636
85
1-2292
1-223
1-2265
1 -2225
1-22365
84
1-2265
1-220
1-2238
1-2198
1-22094
83
1-2238
1-218
1-2211
1-2171
1-21823
82
1-2212
1-215
1-2184
1-2144
1-21552
81
1-2185
1-213
1-2157
1-2117
1-21281
80
1-2159
- 1-210
1-2130
1-2090
1-21010
79
1-2122
1-207
1-2102
1-2063
1 -20739
78
1-2106
1-204
1 -2074
1-2036
1-20468
77
1-2079
1-202
1-2046
1-2009
1-20197
76
1-2042
1-199
1-2018
1-1982
1-19925
75
1-2016
1-196
1-1990
1-1955
1-19653
74
1-1999
1-193
1-1962
1-1928
1-19.381
73
1-1973
1-190
1-1934
1-1901
1-19109
72
1-1945
1-188
1-1906
1-1874
1-18837
71
1-1918
1-185
1-1878
1-1847
1-18565
70
1-1889
1-182
1-1850
1-1820
1-18293
69
1-1858
1-179
1-18020
68
1-1826
1-176
1-17747
67
1-1795
1-173
...
1-17474
66
1-1764
1-170
...
1-17201
65
1-1733
1-167
1-1711
1-1685
1-16928
64
1-1702
1-163
• ■ •
1-16654
63
1-1671
1-160
1-16380
62
1-1640
1-157
...
1-16107
61
1-1610
1-154
1-15834
60
1-1582
1-151
1-1570
1 -1550
1-15561
59
1-1556
1-149
...
1-15288
58
1-1530
1-146
...
1-15015
57
1-1505
1-144
...
1-14742
56
1-1480
1-142
...
1-14469
55
1-1455
1-140
1-1430
1-1415
1-14196
54
1-1430
1-137
1-13923
53
1-1403
1-135
...
• • ■
1-13650
52
1-1375
1-133
...
1-13377
51
1-1348
1-130
...
1-13104
50
1-1320
1-128
1-1290
1-1280
1-12831
45
1-1183
1-1155
1-1145
1-11469
40
1-1045
• • •
1-1020
1-1010
1-10118
35
1-0907
1-0885
1 -0875
1-08786
30
1-0771
• ■ •
1-0750
1-0740
1-07469
25
1 -0635
• • •
1-0620
1-0610
1-06166
20
1-0498
1-0490
1-0480
1-04884
15
1-0374
1-03622
10
1-0245
■ * •
1-0245
1-6235
1-02391
5
1-0123
• • «
...
1-01184
0
1-0000
...
1-0000
1-6000
1-00000
206
ANALYSIS IN^ OIL AND FAT INDUSTRIES
3. Chemically pure Glycerin.
This glycerin forms the purest commercial product, and should —
except for the presence of a small proportion of water — represent the
chemical compound, CgH^Oa, i.e. glycerol. In commerce the following
qualities are recognised : —
Chemicallypureglycerinofsp.gr. . . . i'24
1-25
»
»
5>
1-26
The percentage is most rapidly determined from the specific gravity
in accordance with Table 35, p. 205.
When determining the specific gravity of the most concentrated
glycerin, it is of importance to ensure that it is free from air-bubbles. To
avoid these it is best to warm the sample in a corked flask until all the
bubbles have risen to the top. The flask is then allowed to cool to the
ordinary temperature, and the glycerin carefully transferred to a pyk-
nometer by pouring it down the side of the vessel.
Table 36.
The Specific Gravities and Refractive Indices of Aqueous
Solutions of Glycerin. (Lenz.)
"2
>.
"3)
00
0
>>
Ji
<
(-1
0
*^
Is
if
p— I
i
s
>>
"3)
3
S
>»
•5
0
CI
d
32
5 ^
efi 0
Anhydrous glycerol.
e
-»^
0
d
OQ
X .
0 CO
•a „•
.5 "^
1
>>
a
•a
>>
.a
<
l-H
•Ad
CI
•s
X .
a 00
.^ r-t
100
1-2691
1-4758
74
1-1999
1-4380
49
1-1293
1-3993
24
1-0608 , 1-3639
99
1-2664
1-4744
73
1-1973
1-4366
48
1-1265
1-3979
23
1-0580
1-3626
98
1-2637
1-4729
72
1-1945
1-4352
47
1-1238
1-3964
22
1-0553
1-3612
97
1-2610
1-4715
71
1-1918
1-4337
46
1-1210
1-3950
21
1-0525
1-3599
96
1-2584
1-4700
70
1-1889
1 -4321
45
1-1183
1-3935
20
1-0498
1-3585
95
1-2557
1-4686
69
1-1858
1-4304
44
1-1155
1-3921
19
1-0471
1-3572
94
1-2531
1-4671
68
1-1826
1-4286
43
1-1127
1-3906
18
1-0446
1-3559
93
1-2504
1-4657
67
1-1795
1-4267
42
1-1100
1-3890
17
1-0422
1-3546
92
1-2478
1-4642
66
1-1764
1-4249
41
1-1072
1 -3875
16
1-0398
1-3533
91
1-2451
1-4628
65
1-1733
1-4231
40
1-1045
1-3860
15
1-0374
1-3520
90
1-2425
1-4613
64
1-1702
1-4213
39
1-1017
1-3844
14
1-0349
1-3507
89
1-2393
1-4598
63
1-1671
1-4195
38
1-0989
1 -3829
13
1-0332
1-349 J
88
1 -2372
1-4584
62
1-1640
1-4176
37
1 -0962
1-3813
12
1-0297
1-3480
87
1-2345
1-4569
61
1-1610
1-4158
36
1-0934
1-3789
11
1-0271
1-3467
86
1-2318
1 -4555
60
1-1582
1-4140
35
1-0907
1-3785
10
1-0245
1-3454
85
1-2292
1-4540
59
1-1556
1-4126
34
1 -0880
1-3772
9
1-0221
1-3442
84
1 -2265
1-4525
58
1-1530
1-4114
33
1-0852
1-3758
8
1-0196
1-3430
83
1-2238
1-4511
57
1-1505
r4]02
32
1-0825
1-3745
7
1-0172
1-3417
82
1-2212
1-4496
56
1-1480
1-4091
31
1-0798
1 -3732
6
1-0147
1-3405
81
1-2185
1-4482
55
1-1455
1-4079
30
1-0771
1-3719
5
1-0123
1 -3392
80
1-2159
1-4467
54
1-1430
1-4065
29
1-0744
1-3706
4
1-0098
1-3380
79
1-2122
1-4453
53
1-1403
1-4051
28
1-0716
1-3692
3
1-0074
1-3367
78
1-2106
1-4438
52
1-1375
1-4036
27
1-068!)
1-3679
2
1-0049
1 -3355
77
1-2079
1-4424
51
1-1348
1 -4022
26
1-0663
1-36C6
1
1 -0025
1-3342
76
1-2046
1-4409
50
1-1320
1-4007
25
1-0635
1-3652
0
1-0000
1-3330
75
1-2016
1-4395
1
i
GLYCERIN
207
The refractive index may also be used to determine the proportion
of glycerin. Table 36, p. 206, gives the numbers determined by Lenz.
For exact determinations it is necessary to adhere to the tempera-
tures given, and for this reason Lenz recommends determining the
refraction of the glycerin, and then that of pure water, at the same
temperature, immediately afterwards; the influence of temperature and
of small fluctuations in the adjustment of the scale are thus eliminated.
The differences between the refractive indices of glycerin solutions
and of pure water are given in the following Table : —
Table 37.
Differences between the Refractive Indices of Aqueous Solutions
of Glycerin and Pure Water. (Lenz.)
si
■5) 0
Per cent, of
glycerol
by weight.
p a>
Per cent, of
glycerol
by weight.
si
"So a
Per cent, of
glycerol
by weight.
"21
■3) a
Per cent, of
glycerol
by weight.
0-1424
100
0-1046
74
0-0645
48
0-0288
22
0-1410
99
0-1032
73
0-0630
47
0-0275
21
0-1395
98
0-1018
72
0-0616
46
0-0261
20
0-1381
97
0-1003
71
0-0601
45
0-0238
19
0-1366
96
0-0987
70
0-0587
44
0-0225
18
0-1352
95
0-0970
69
0-0572
43
0-0212
17
0-1337
94
0-0952
68
0-0556
42
0-0199
16
0-1323
93
0-0933
67
0-0541
41
0-0186
15
0-1308
92
0-0915
66
0-0526
40
0-0173
14
0-1294
91
0-0897
65
0-0510
39
0-0160
13
0-1279
90
0-0889
64
0-0495
38
0-0146
12
0-1264
89
0-0861
63
0-0479
37
0-0133
11
0-1250
88
0-0842
62
0-0464
36
0-0120
10
0-1235
87
0-0824
61
0-0451
35
0-0108
9
0-1221
86
0-0806
60
0-0438
34
0-0096
8
0-1206
85
0-0792
59
0-0424
33
0-0083
7
0-1191
84
0-0780
58
0-0411
32
0-0071
6
0-1177
83
0-0768
57
0-0398
31
0-0058
5
0-1162
82
0-0757
56
0-0358
30
0-0046
4
0-1148
81
0-0745
55
0-0372
29
0-0033
3
0-1133
80
0-0731
54
0-0385
28
0-0021
2
01119
79
00717
53
0-0345
27
0-0008
1
01104
78
0-0702
52
0-0332
26
0-0000
0
0-1090
77
0-0688
51
0-0318
25
0-1075
76
0-0663
50
0-0315
24
0-1061
75
0-0659
49
0-0302
23
For the determination of the refractive index of dilute glycerin
solutions, the " immersion-refractometer " may also be used. It should
be noted, however, that this instrument may only be used for solutions
containing less than 28 g. of glycerol in 100 c.c. of solution.
In the case of dilute solutions containing chemically pure glycerin,
the best method of estimation is oxidation with either bichromate or
permanganate. The latter is best carried out by using the modification
208 ANALYSIS IN OIL AND FAT INDUSTRIES
of Waiiklyn and Fox's process proposed by R. Benedikt and R.
Zsigmondy.^ This depends upon the complete oxidation of the
glycerol in cold, strongly alkaline solution to oxalic acid, according to
the equation : —
C3HP3+3O, = C,H..0, + C0, + 3H,0.
For the test, 0-2-0-3 g. of highly concentrated glycerin or the corre-
sponding quantity of dilute glycerin (calculated approximately from the
specific gravity) are placed in a capacious flask and diluted to about
250 c.c. with water. 10 g. of solid potassium hydroxide are added, and
then a 5 per cent, solution of potassium permanganate, at the ordinary
temperature, until the solution is no longer green but blue or blackish.
If preferred, solid, finely powdered potassium permanganate may be
added. On heating to boiling, hydrated manganese dioxide separates
out, and the liquid becomes red. A solution of sulphurous acid or
sodium sulphite is then added until the liquid is just decolorised. The
solution is filtered through a smooth filter paper of such a size that it
takes at least half of the liquid at once, the filter is carefully washed
with hot water, and the filtrate acidified with acetic acid. The last
washings are frequently turbid through containing some hydrated
manganese dioxide ; this turbidity disappears, however, in the acidifica-
tion with acetic acid as the liberated sulphurous acid reduces the
manganese dioxide. The solution is heated to boiling, and the oxalic
acid precipitated by the addition of 10 c.c. of a 10 per cent, solution
of calcium chloride. The precipitate of calcium oxalate is further
treated in the usual way, and the oxalic acid is calculated to glycerol
according to the above equation.
The content of ash plus polyglycerols should not exceed 0-03 per
cent. ; the ash itself should not exceed o-oi per cent.
Acrolein (and other reducing substances) are best detected by the
addition of a few drops of silver nitrate solution to the dilute solution
of the gl}xerin, the solution being allowed to stand for twent}'-four
hours at the ordinary temperature. The test is still more delicate if
ammoniacal silver nitrate be used.
Volatile Fatty Acids are recognised by heating the gl\cerin with
alcohol and concentrated sulphuric acid, when ethyl esters of the acids
are formed, which can be detected by their odour, recalling that of pine
apple.
Sugar is determined polarimetrically.
Arsenic should be entirely absent. A rapid and most sensitive test
for arsenic is that of Gutzeit. For this test, 2 c.c. of the sample are
introduced into a tall test tube and treated with zinc (free from arsenic)
and a few cubic centimetres of absolutely pure dilute sulphuric acid.
1 Chem. Zeit., 1885, 9, 975 ; /. Soc. Clum. bid., 1885, 4, 610.
GLYCERIN 209
The mouth of the test tube is covered with a close-fitting cap of filter
paper, two or three layers in thickness, the innermost layer of which has
been moistened with a 50 per cent, solution of silver nitrate with the aid
of a glass rod. In presence of arsenic, arseniuretted hydrogen is evolved.
After standing for ten minutes, the paper cap is taken off. There
should be no deep yellow stain on the inner layer of paper. Only a
very pale yellow coloration is permissible. This test is so extremely
sensitive, that it is absolutely essential to carry out a blank test with the
same reagents. This silver nitrate test is almost too sensitive (although
commercial glycerins are met with which give no colour after ten
minutes), and has been replaced by the less delicate test, in which
the silver nitrate solution is replaced by a concentrated solution of
mercuric chloride. A glycerin may be considered as practically free
from arsenic when no yellow colour is obtained after ten minutes.
If mercuric chloride is used, hydrochloride acid may be taken
instead of sulphuric ; with silver nitrate, hydrochloric acid is not
permissible, as small quantities of hydrogen chloride gas may be
evolved if the solution becomes warm.
The Marsh-Berzelius test may of course also be used. This is fully
described in the section on the " Manufacture of Sulphuric Acid," Vol. i,,
part i., pp. 363 et seq.
Literature.
Lewkowitsch, J. — Chemical Technology and Analysis of Oils, Fats, and Waxes,
Vol. I., 5th edition, 1913 ; Vols, II. and III., 4th edition, 1909,
Lewkowitsch, J. — The Laboratory Companion to Fats and Oils industries, 1901.
Ill O
RESINS, BALSAMS, AND GUM-RESINS
By K. DiETERlCH, Ph.D., Lecturer in Pharmaceutical Chemistry, the Royal \'eterinary
High School, Dresden. English translation revised by the late J. LewkowitsCH,
M.A., Ph.D.
Resins, balsams, and gum-resins are the secretions of chiefly exotic
plants, and represent mixtures of varying composition. They are used
in industry and in medicine. The methods employed to obtain them
are usually so cumbersome and so crude that the substances which come
on the market as resin, balsam, and gum-resin are completely changed
products, differing widely from their original form as they occur in
nature. Since most of the consignors are non-Europeans, it has been
possible only in the case of a few resins to obtain authentic samples.
On account of the great distances from which the resins come, the
many hands through which they pass, and their completely changed
and varying composition, the examination of samples obtained direct
from the tree, and of authenticated purity, is extremely useful and
of fundamental importance. The analytical data obtained from such
genuine samples, e.g. of Peru balsam, have led to definite conclusions,"
but have also shown that the commercial article very seldom
corresponds to the genuine resin. A demand for the genuine article
would lead to the rejection of nearly all commercial samples. Hence
in the examination of commercial samples certain variations must be
allowed, and concordant results, such as are obtained in the case of fats
and oils, must not be expected ; unfortunately, the analyses of resins
so far published not only vary within wide limits, but are, speaking
generally, actually contradictor}-. For this reason it is not possible, at
present at any rate, to lay down reliable methods of examination, or
even to fix certain limits within which characteristic values may vary.^
As regards classification, the subdivision into resins, balsams, and
gum-resins has been retained, although numerous attempts have been
made to classify these substances on a chemical basis.^ This sub-
division appears to be the most convenient, especially from the stand-
point of commercial and technical considerations.
The examination of resins comprises both qualitative and quanti-
^ C/. K. Dieterich, Analyse der Harze, Ba!same, und Gummiharze nebst ihrer Chemie und
Pharni.ikognosie, 1 900.
- Cf. A. Tschirsch, Harze und HarzbehSller.
210
METHODS OF ANALYSIS 211
tative tests. Whereas formerly qualitative tests, colour reactions, etc.,
were used almost exclusively for identification and for evaluation, a
large number of quantitative tests (to some extent included in the
Pharmacopoeias) are now available. The most important of these are
the determination of the acid and saponification values (and their
difference, the ester values), a method of valuation borrowed from the
analysis of fats and oils. While the determination of these values
furnishes really useful numbers, the iodine-bromine values of the resins
are of minor importance. As more recent proposals the following
quantitative methods, which may be used to complement the above
values, may be mentioned : — The methyl value (Gregor and Bam-
berger), the carbonyl value (Kitt), the acetyl value (K. Dieterich), and
the examination of the resin alcohols and acids (K. Dieterich).
The determinations now generally included in the analysis of resins
are : —
{a) The Acid Value.
{b) The Saponification or Resin Value.
{c) The Ester Value (the difference between (a) and {b).
(d) Loss at ioo° (Mojsture).
{e) Ash.
{/) Proportion soluble in Alcohol.
{g) Proportion insoluble in Alcohol,
(//) Specific Gravity.
And the following more special determinations : —
{{) Determination of the Cinnamein and Resin Esters in Peru
Balsam.
{k) Acetyl, Carbonyl, and Methyl Values.
(/) Examination of Resin Acids and Alcohols,
(w) Qualitative Reactions.
Any single estimation in the case of resins cannot obviously be
regarded as conclusive, but the relations of the several data obtained
under the above headings often renders it possible to draw certain
conclusions,
A. — Methods of Analysis.
The meaning of certain terms, as used in this Section, is as
follows : —
The Acid Value. — The number of milligrams of potassium
hydroxide required for the neutralisation of the free acid in i g. of
the resin.
The Acid Value of the Volatile Portions. — The number of mil-
ligrams of potassium hydroxide required to neutralise 500 g. of
distillate obtained from o-S g. of gum-resin by distillation in a current
of steam, e.g., in ammoniacum, galbanum.
212 RESINS, BALSAMS, AND GUM-RESINS
The Saponification Value. — The number of milligrams of potassium
hydroxide required to saponify i g. of resin.
Tiie Resin Value. — The number of milligrams of potassium
hydroxide required to neutralise i g. of (certain) resins and gum-
resins on cold fractional saponification with alcoholic potassium
hydroxide alone.
The Total Saponification Value (Fractional Saponification). — The
total number of milligrams of potassium hydroxide required to
neutralise i g. of (certain) resins and gum-resins on cold fractional
saponification successively with alcoholic and aqueous potassium
hydroxide.
The Gum Value. — The difference between the total saponification
value and the resin value.
The Ester Value. — The difference between the acid value and the
saponification value.
The Acetyl Value. — The difference between the acetyl saponification
value and the acetyl acid value.
The Carbonyl Value. — The percentage of carbonyl oxygen in the
resin.
The Methyl Value. — The percentage of methoxyl, calculated as
" methyl" (CH3), obtained from i g. of the resin.
The details for the determination of these characteristic values
depend on the nature of the substance under examination (see
examples) ; for most resins several alternative methods have hitherto
been in use.
(a) The Acid Value.
I. By Direct Titration (A. Kremel). — If the resin is completely
soluble in alcohol, chloroform, or benzene-alcohol, the solution of i g.
of the sample is titrated with Njz or A710 alcoholic potassium
hydroxide, phenolphthalein being used as the indicator. If the
substance is not completely soluble an alcoholic extract is titrated
as above, and the result calculated to i g. of the sample. {Examples : —
Gum-resins, benzoin, storax.) An alternative method is to prepare
a water-alcohol extract by heating i g, of the finely ground substance
with 30 c.c. of water under a reflux condenser, adding 50 c.c. of 96 per
cent, alcohol, and boiling again under the reflux condenser for fifteen
minutes for each extraction ; the extract is allowed to cool and is then
titrated without filtering the solution. {Examples: — Myrrh, bdellium,
opoponax, sagapenum.)
2. By Indirect Titration (K. Dieterich).
(a) In the case of completely or almost completely soluble ester-
free resins, the alkali simultaneously neutralises the ac'd and dissolves
the resin, i g. of the ester-free resin is digested in a glass-stoppered
THE ACID VALUE 213
bottle with 25 c.c. of A'/2 alcoholic potassium hydroxide solution and
50 c.c. of light petroleum spirit — or benzene in the case of copal — for
twenty-four hours ; Nji sulphuric acid, with phenolphthalein as the
indicator, is used for the titration of the excess of alkali. {Examples : —
Colophony, dammar, sandarac, mastic, guaiacum, copal.)
(/3) In the case of partially soluble resins, containing esters which
are saponified with difficulty, when the alkali neutralises the acid and
dissolves out the acidic portions, i g. of the finely ground resin is
digested in a stoppered bottle for twenty-four hours with 10 c.c. of
alcoholic, and 10 c.c. of aqueous, iV/2 potassium hydroxide solution,
and the excess of alkali titrated back after addition of 500 c.c. of water.
{Examples : — Asafoetida, olibanum.)
(y) In the case of partially soluble resins, containing esters, a
water-alcohol extract is used, i g. of the finely ground resin is boiled
with 50 c.c. of water for fifteen minutes under a reflux condenser;
100 c.c. of strong alcohol are added, the liquid boiled for a further
fifteen minutes, allowed to cool, and made up to 150 c.c. To 75 c.c.
of the filtrate, equivalent to 0-5 g. substance, are added 10 c.c. of
jV/2 alcoholic potassium hydroxide solution, and after standing in a
small flask for exactly five minutes the solution is titrated back with
N/2 sulphuric acid, using phenolphthalein as indicator. (Examples : —
Ammoniacum, galbanum.)
((5) In the case of almost completely soluble resins, containing easily
saponifiable esters, the natural product as such is used. The finely
ground sample is digested for exactly five minutes with 10 c.c. of
N/2 alcoholic potassium hydroxide solution. {Example : — Benzoin.)
3. By estimating the Acid Value of the Volatile Acids. — (For
gum-resins containing much essential oil.) A small quantity of water
is added to 0-5 g. of the resin in a flask attached to an inclined
condenser and heated on a sand-bath (to avoid excessive condensation),
and a current of steam passed through. The condenser tube dips
into 40 c.c. of N/2 potassium hydroxide solution contained in a
receiver. When exactly 500 c.c. have passed over, the condenser tube
is rinsed with distilled water, and the solution titrated back with
standard acid, using phenolphthalein as the indicator. {Examples: —
Ammoniacum, galbanum.)
(6) The Saponification Value.
I. Determination in the Hot Solution.
(a) I g. of a completely soluble resin is boiled for thirty minutes
under a reflux condenser with 25-30 c.c. of N/2 alcoholic potassium
hydroxide, diluted with alcohol and titrated with N/2 sulphuric acid,
using phenolphthalein as the indicator. {Examples : — Almost all balsams
and resins.)
214 RESINS, BALSAMS, AND GUM-RESINS
If the substance is not completely soluble, either of the two following
methods may be used : —
(,8) The alcoholic extract is titrated exactly as in (a), and the result
calculated on i g. of the sample. {Examples: — Gum-resins, benzoin,
storax.)
(y) Water is added to the sample to dissolve the gummy portions,
and it is then heated as in (a). {Exa))iple : — Myrrh.)
2. Determination in the Cold Solution (K. Dieterich).
(a) In the case of completely soluble resins i g. of the sample is allowed
to stand for twenty-four hours at the ordinary temperature in a 500 c,c.
stoppered bottle with 50 c.c. of petroleum spirit of sp. gr. 0-700 at 15",
and 50 c.c. of iV/2 alcoholic potassium hydroxide solution; it is then
titrated back with A72 sulphuric acid. To dissolve any salt which may
have separated on the bottom of the bottle, which may happen with
Peru balsam, 300 c.c. of water are added before titration. {Exaviples : —
Peru balsam, copaiba balsam, benzoin, storax.)
(/3) In the case of incompletely soluble resins, two portions of i g.
each are powdered and allowed to stand, with frequent shaking, for
twenty-four hours at the ordinary temperature in a i litre stoppered
bottle with 50 c.c. of petroleum spirit of sp. gr. 0-700 at 15° and 25 c.c.
q{ N\2 alcoholic potassium h}'droxide solution, added in the order given.
One portion is titrated back after addition of 500 c.c. of water with
N\2 sulphuric acid, using phenolphthalein as the indicator, the liquid
being agitated during the titration by imparting a rotary motion to
the flask. This gives the " resin value." To the second portion are
added 25 c.c. of NI2 aqueous potassium hydroxide and 75 c.c. of
water; this is allowed to stand, with frequent shaking, for a further
twenty - four hours, when 500 c.c. of water are added, and is then
titrated with iV/2 sulphuric acid, with agitation as before. The result
obtained is the " total saponification value." The difference is termed
the "gum value." {Examples : — Ammoniacum, galbanum.)
(c) The Ester Value.
This value is the difference between the acid and the saponification
values.
{d) Loss at 100° (Moisture).
For this determination from 2-3 g. of the resin are heated in an oven
at 100" to constant weight. Resins containing essential oils lose, of
course, volatile substances as well as water. {Examples : — All resins
except balsams.)
(e) Ash.
This is determined by incinerating the residue obtained in {d).
SOLUBILITY. ESTERS 215
(/) The proportion Soluble in Alcohol.
The sample is extracted with 90 or 96 per cent, alcohol, either by
mixing 10 g. of the sample with sand and extracting in a Soxhlet
apparatus, or by dissolving in a flask attached to a reflux condenser,
filtering the resulting solution on a tared paper and washing the
residue with hot alcohol. The solvent in the filtrate is evaporated
off and the residue dried at 100' to constant weight. To avoid
creeping during the evaporation, the dish is placed in water in a larger
dish, which serves as a water-bath; by adopting this expedient the
alcohol never rises above the level of the water outside. In the case
of resins containing essential oils, such as gum-resins, it is preferable
to estimate the insoluble portion and to calculate from this the
soluble portion : the volatile portions, which otherwise might be over-
looked, are thus included in the result.
(g) The proportion Insoluble in Alcohol.
The residue from (/) is dried at 100° to constant weight.
Instead of using alcohol for the extraction in (/"), and (g-), ether,
petroleum naphtha, light petroleum spirit, chloroform, etc., may be
employed.
(h) Specific Gravity at 15°.
The specific gravity of liquid resins, such as Mecca, Copaiba, and Peru
balsams, is determined with the Mohr-Westphal balance, and that of
solid resins by the methods used for wax (see p. 107).
For solid resins, such as colophony, salt solutions of known concentra-
tion may be used.
(/■) Determination of the Cinnamein and Resin Esters
in Peru Balsam.
The estimation of the cinnamein is best carried out immediately
after the determination of the portion soluble in ether (see g above).
The ethereal filtrate is shaken out twice successively in a separating
funnel with 2 per cent, sodium hydroxide solution, using 20 c.c. each
time, washed twice with water and dried for thirty minutes on the
water-bath (Thoms).
The determination of the resin esters follows conveniently on the
cinnamein determination, the brown alkaline resin solution from which,
after separation from the ethereal liquid, is precipitated with dilute hydro-
chloric acid. The precipitate is collected on a tared filter and washed
on the pump until free from chlorine. The resin is dried at 80° to
constant weight and its percentage calculated. {^Example: — Peru
balsam.)
216 RESINS, BALSAMS, AND GUM-RESINS
(k) The Acetyl, Carbonyl, and Methyl Values.
1. The Acetyl Value.
The resin is boiled under a reflux condenser with an excess of acetic
anhydride and anhydrous sodium acetate either until solution is com-
plete, or until no more dissolves. The solution thus obtained is poured
into water, and the separated product collected on a filter and exhausted
with boiling water until all free acetic acid has been removed. (The in-
soluble residues from dammar and copal are similarly treated.) The
acetyl products are dissolved in alcohol and the acid and saponifica-
tion values determined as described in the section on " Oils, Fats, and
Waxes," pp. 122 and 1 14. The difference between the acetyl acid value
and the acetyl saponification value is the "acetyl (ester) value."
[Examples : — Turpentine, colophony, sandarac, dammar, copal.)
2. The Carbonyl Value (M. Kitt).
The substance is warmed with sodium acetate and an accuratel)-
measured quantity of phenylhydrazine hydrochloride in dilute alcoholic
solution. The excess of phenylhydrazine hydrochloride is ascertained
by oxidation with Fehling's solution and measuring the nitrogen
evolved. The carbonyl value is found from the formula; —
Percentage of carbonyl oxygen = V — Vq ^-^ where \' is the
volume of nitrogen obtained from the total phenylhydrazine hydro-
chloride added, and V^, that of the excess left, both reduced to o'' and
760 mm., and S the weight of substance used. {Exaviplcs : — Sandarac,
elemi, colophony, copal, acaroid.)
3. The Methyl Value (G. Gregor).
This determination is based upon Zeisel's method. The methoxj'l
groups present are removed as meth\l iodide by means of h)-driodic
acid, and the meth}-l iodide estimated as silver iodide.^
(/) Examination of the Resin Acids.
The saponification products of the resins, as obtained above {b i and
b 2) are decomposed with acid, washed and dried. The resulting
substances are examined both qualitatively and quantitatively by
determining their solubility in various solvents, and their acid and
saponification (also ester) values. {Examples: — Balsams, benzoin,
colophony, dammar, copal).
(m) Qualitative Reactions.
These are described below under the heading B.
■ C/. G. Gregor, MonalsL, 1 898, 19, 116;/. Soc. Cliem. Ind., 1 898, 17, 609.
CHARACTERISTIC VALUES
217
B. — Characteristic Values and Standards of Quality.
The subjoined tabular statement of the characteristic values of resins,
balsams, and gum-resins is based on the determinations of Williams,
Kremel, von Schmidt and Erban, Gehe and Co., Beckurts and Briiche,
E. Dieterich, K. Dieterich, Tschirch, and others. The values, which are
given in round numbers, do not constitute a criterion of purity and
quality ; they are merely intended to show the limits of the numbers, as
determined by the several methods of examination employed. The
solubilities given represent the demands which present experience
justifies. Only the most important balsams, resins, and gum-resins are
included in the Tables.
I. Balsams.
Copaiba.
1. Maracaibo.
Acid value (by a\)*
Saponification value (by i^la)
( M '''2a)
Ester value
Sp. gr
Methyl value (by kZ')
2. Para (Maranham).
Acid value (by aV) .
Saponification value (by /'la)
( M '^2a)
Ester value
Sp. gr
3. Bast Indian (Gur-
jun Balsam).
Acid value (by «1) .
Saponification value (by lAa)
„ ( „ bla)
Ester value
Sp.gr
4. Peru Balsam.
Acid value (by al).
Saponification value (by i^la)
( ., ^2a)
Ester value . . . .
Methyl value (by kZ)
Cinnamein (by i) .
Resin esters (by i) .
Saponification value of cinna-
mein (by ^la)
Sp. gr
75 to 100
80
80
- 0-5
0-96
100
90
8
0-99
25 to fi5
30 „ 70
30 „ 60
2 „ 18
0-91 „ 0-99
5 to 20
8 „ 20
10 „ 25
1 „ 15
0-955 „ 0-980
40 to 80
220 „ 260
240 „ 270
140 „ 200
14-4 „ 22-6
60 „ 61%
19 „ 28
240
1-138 to 1-148
Solubility.
Ether .
Chloroform .
Petroleum spirit .
Oil of turpentine .
Carbon bisulphide
Alcohol (90%) .
Ethyl acetate
Ether .
Chloroform .
Benzene
Oil of turpentine .
Alcohol (90%) .
Ethyl acetate
Petroleum spirit .
Carbon bisulphide
Alcohol (90%) .
Chloroform .
Ethyl acetate
Benzene
Oil of turpentine .
Ether .
Petroleum spirit .
Carbon bisulphide
Chloroform .
Ethyl acetate
Alcohol
Ether .
Benzene
Petroleum spirit
Oil of turpentine
Carbon bisul
phide
90%
92 to 98%
94
66
85
98%
} 86 „ 88%
Completely
soluble
Only
partially
soluble
1
Completely
soluble
Only
partially
soluble
Completely
soluble
] Only
r partially
J soluble
^ Completely
j soluble
r Almost
-! completely
[ soluble
Soluble
The letters and figures refer to the methods given under A (pp. 211 zt seq.).
218
RESINS, BALSAMS, AND GUM-RESINS
II. Resins.
Amber.
tiolubility.
Fused.
Natural.
Acid value (by (j1)
15 to 35
Alcohol .
. almost insol.
.•Mmost insol.
Saponification value
Ether .
. partially sol.
11
(by/.l;3) . .
86 „ 145
Methyl alcohol
. almost insol.
Ester value .
71 „ 91
Amyl alcohol .
. partially sol.
u
Moisture
Ash ....
1%
0-2 to 0-3%
Benzene
/almost com-
\ pletely sol.
r
Petroleum spirit
. almost insol.
)i
Acetone .
* 1*
Insol.
Glacial acetic acid .
. partially sol.
11
Chloroform .
M
11
Carbon bisulphide .
falmost com-
\, pletely sol.
l Partially sol.
Oil of turpentine .
f almost com-
\ pletely sol.
I
Copal, which may be confounded with amber, is soluble in cajuput
oil, while amber is not. On ignition, amber blackens moist lead acetate
paper ; copal does not. Adulterants and artificial products from
colophony arc recognised by their solubility in alcohol and their high
acid values.
Benzoin.
1. Siam.
2. Sumatra.
Acid value (by al) .
120 to 170
Acid value (by a\)
95 to 190
( „ «2o) .
140 „ 170
II II ( 11 ''25) .
100 „ 130
Saponification value (by 61^)
170 „ 210
Saponification value (by /'lj8)
155 „ 270
( ,. i2a)
220 „ 240
1, ( 1, ^^a)
180 „ 230
Ester value
35 ,, 75
Ester value ....
30 „ 175
Ash ....
0-2 „ 1-5%
Loss at 100°
4 .1 9%
Methyl value (by /3) .
28-5 „ 43-5
Ash
0-2 „ 1-5%
(Should be soluble in alcoho
Methyl value (by /3) .
13 „ 25-5
with little residue, at mosi
(Should be soluble to the
5% vegetable tissue.)
extent of 70 to 80% in alcohol.)
Colophony.
Solubility.
Acid value (by al)
I. ( I, «2a)
Sp. gr.
Loss at 100°
Ash .
■\retvl fh /Ti /■'^^''^ value
y K y J 1^ Saponification value
Carbonyl value (by /2)
Methyl value (by /3)
(Its solution in acetic acid gives a
fine red coloration with sulphuric acid.)
145 to 180
145
1-045
0-0
0-2
155-82
251-21
0-54
185
1-085
0-5%
1-2%
1.55-84
274-94
0-56
Alcohol
Oil of turpentine
Essential oils
Acetone
Ether
Chloroform
Methyl alcohol .
Amyl alcohol .
Ethyl acetate
Benzene .
Carbon bisulphide
Petroleum naphtha
Light petroleum
spirit
Completely
soluble
Partially
soluble
CHARACTERISTIC VALUES
219
Copal (Zanzibar).
Acid value (by al)
35 to 95
( „ «2a)
60 „ 65
Loss at 100°
0-5 „ 2-5%
Ash
0-25 „ 2-0%
\ ^ ^ /-u L^\ r Acid value
Acetyl (by /fl) (saponification value .
77^1 \ on the soluble
203-29 / portion
( /I") /^'^'^ value
" <.>'-' 1^ Saponification value
210-10 to 221-14 \on the insoluble
203-94 „ 231 -27 J portion
Carbonyl value (by X-2) ....
0-61
Solubility.
Natural.
SheUed.
Alcohol
Insoluble
Almost soluble
Ether .
Partially soluble
Partially soluble
Methyl alcohol .
Insoluble
Insoluble
Amyl alcohol
Slightly soluble
Partially soluble
Benzene
Partially soluble
Almost completely soluble
Petroleum spirit .
Insoluble
Insoluble
Acetone
Almost soluble
Glacial acetic acid
Partially soluble
Partially soluble
Chloroform .
.
Carbon bisulphide
Insoluble
Almost soluble
Oil of turpentine .
Partially soluble
M
Cajuput oil .
Completely soluble
Completely soluble
Chloral hydrate (80% solution) .
Quite insoluble
Quite insoluble
Dammar.
Acid value (by al)
( n «2a)
Loss at 100°
Ash
A . 1 ,-u 1.1 \ f Acid value ....
Acetyl (by /51)|s,p,„ifi,,tion value . .
20 to 35
20 „ 30
0-1 „ 1%
0-01 „ 0-1%
50-52 „ 51-80
132-08 „ 134-86
Guaiacum.
Acid value
(by al) .
20
to 45
11
( „ «2a)
•
70
,. 97
Ash
• •
• •
2-
10%
Acetyl (by ^1) { ^f^
value .
value .
13 to 23
163 „ 193
Methyl va
lue (by /f3)
• •
73
„ 84
Solubility.
Alcohol . at least 80%
Water . . . 3 to 5%
Petroleum spirit 0-06 ,, 10%
Ether . . . 22 „ 91%
Benzene . . 20 „ 90%
Carbon bisulphide 12 „ 37%
Chloral hydrate (60 and 80%
solutions) ....
Soluble
Almost
completely
soluble
220
RESINS, BALSAMS, AND GUM-RESINS
Mastic (Levant).
Solubility.
Acid value (by al) .
50 to 70
Alcohol ....
Partially sol.
( „ «2a)
44 „ 66
Ether .
Soluble
Loss at 100° , . . .
0-9 „ 1-5%
Methyl alcohol .
Partially sol.
Ash
0-1 „ 0-2%
Amyl alcohol
Soluble
Methyl value (by JtS)
0 „ 1-9
Benzene
Petroleum spirit .
Acetone
Glacial acetic acid
Chloroform .
Carbon bisulphide
Oil of turpentine .
1'
Insoluble
Partially sol.
It
11
Slightly sol.
Partially sol.
Chloral hydrate (60 to 80%
solution) ....
'»
Pine Resin.
SolubUity.
Acid value (by «1) .
Saponification value (by iJla) .
Ester value ....
Loss at 100° ....
Ash
Acetyl (by «){t:j?;£ :
100 to 160
150 „ 190
10 „ 30
5 to 12-5%
1%
155-27 to 158-48
222-86 „ 230-75
Alcohol (90%) .
Chloroform . .
Ethyl acetate .
Benzene .
Carbon bisulphide
Ether
Oil of turpentine
Petroleum spirit
Completely sol.
11
11
■I*
»i
1*
Partially sol.
Sandarac.
Solubility.
Acid value (by al) .
95 to 155
Absolute alcohol
Completely sol.
(by a2a)
130 „ 160
Ether .
II
Loss at 100° ....
0-04 „ 0-2%
Amyl alcohol .
1*
Ash
0-1 „ 2%
Methyl alcohol
Partially sol.
Ace.y.(by.0(^,fvat':
166 „ 170
Acetone .
Completely sol.
239 „ 252
Chloroform
,
Partially sol.
Carbonyl value (by >f2) .
0-43 „ 0-74
Essential oils .
Benzene .
Glacial acetic acid .
Carbon bisulphide .
'1
Almost insol.
Partially sol.
Almost insol.
Chloral hydrate
(60%
/ Almost com-
\ pletely insol.
solution)
Petroleum spirit
Partially sol.
Australian samples are more soluble in petroleum spirit than the
above African sandarac.
CHARACTERISTIC VALUES
221
Storax.
Solubility.
Acid value (by al) .
Saponification value (by dl^ .
(ii^la).
Ester value ....
Loss at 100° ....
Ash
Methyl value (by y63)
35 to 180
130 „ 250
100 „ 190
70 „ 185
5 „ 40%
0-0 „ 1-5%
3-6 „ 4-5
Alcohol .
Ethyl acetate .
Chloroform
Ether
Benzene .
Oil of turpentine
Carbon bisulphide
Petroleum spirit
f Almost com-
\ pletely sol.
Partially sol.
11
II
II
II
II
Turpentine.
1. Ordinary Turpen-
tine.
Acid value (by al) .
Saponification value ((^la)
Ester value
Carbonyl value (by /f2) .
(This turpentine hardens
with calcium hydroxide.)
2. Larch Turpentine
Acid value (by al) .
Saponification value (by 61a)
Ester value
(This turpentine does not
harden with calcium hy-
droxide.)
110 to 145
108
180
2
60
123
126
187
217
0-28
0-57
65 to 100
85 „ 130
0 ,, 55
70 „ 72
179 „ 191
Solubility,
Alcohol (90 %)
Ether
Chloroform
Ethyl acetate .
Benzene .
Oil of turpentine
Carbon bisulphide
Petroleum spirit
Alcohol .
Ether .
Methyl alcohol
Amyl alcohol .
Benzene .
Petroleum spirit
Acetone .
Glacial acetic acid
Chloroform
Ethyl acetate .
Carbon bisulphide
Oil of turpentine
Completely sol.
/ Almost com-
\^ pletely sol.
Partially sol.
Soluble
f Almost com-
^^ pletely sol.
Soluble
( Almost com-
^^ pletely sol.
Completely sol.
III. GUxM Resins.
Ammoniacum.
Solubility.
Acid value (by al)
( „ a3) .
.._ .( .1 «27)
Saponification value (by 31/3)
Total sap. value (by i2p')
Ester value
Resin value
Loss at 100° .
Ash
Methyl value (by iS)
55 to 135
100 „ 200
80 „ 105
145
235
155
100
99
60
145 „ 162
2-0 „ 15%
1
8-6
7-5%
11
Partially soluble in all indifferent sol-
vents. Alcohol dissolves 90%, water up to
20%. Galbanum is tested for by boiling
5 g. of the ammoniacum, as finely divided
as possible, in a dish with 15 g. hydrochloric
acid (sp. gr. 1*19) for fifteen minutes,
filtering through a double moistened filter,
and carefully adding to the clear filtrate
an excess of ammonia. The presence of
galbanum is shown by the characteristic
blue fluorescence of umbelliferon in reflected
light.
222
RESINS, BALSAMS, AND GUM-RESINS
Galbanum.
Solubility.
Acid value (by al) .
5 to 70
As for ammoniacum. Ash
not to exceed
( ,, «3) .
72 „ 115
10%.
( n «27)
20 „ 70
Saponification value (by il^ .
75 „ 245
Total sap. value (by 62^')
107 „ 123
Ester value ....
50 „ 180
Resin value ....
115 „ 136
Loss at 100° ....
1 ,, 31%
Ash .....
1 „ 30%
Methyl value (by -^3) .
3-7
Myrrh.
Solubility.
Acid value (by al) .
Saponification value (by il^) .
( M ^17) .
Ester value
Ash
Methyl value (by i3)
60 to 70
159 „ 216
220 „ 230
95 „ 145
1 „ 10%
3-6 „ 4-5
Partially soluble in all indifferent
solvents. Water should not extract more
than 50%, and alcohol not less than
35%. Ash not to exceed 7%.
Olibanum.
Acid value (by al)
„ (by ^2^)
Saponification value (by Sl^') .
( „ ^517) . .
Ester value ......
Carbonyl value (by ,^2) ....
Methyl value (by /f3) . . . .
45 to 60
30 „ 50
65 „ 120
110 „ 120
6 „ 60
0-36
5-3 to 6-4
Literature.
DiETERICH, K. — Analyse der Harze, Balsame, unci Gummiharze nebst ihrer Chemie
und Pharmacognosies 1 900.
TSCHIRCH, A. — Harze u. Harzbehdlter, 2nd edition, 1906.
DRUGS AND GALENICAL PREPARATIONS
By K. DiETERiCH, Ph.D., Lecturer on Pharmaceutical Chemistry, The Royal
Veterinary High School, Dresden. English translation revised by
Frederick B. Power, Ph.D., LL.D,, Director of the Wellcome Chemical
Research Laboratories, London.
Drugs are generally considered to comprise all those crude products
which represent either the dried parts of plants or plant extracts, and
which serve as initial material for the manufacture of various important
pharmaceutical or medicinal preparations. The fact that drugs, to a
large extent, only come into the hands of the manufacturer as
secondary or even more completely altered products, is due to the
chemical changes^ which always take place in connection with their
production, whether these changes be unintentional or otherwise. As
a result, even with consideration of differences in the character of the
soil, drugs always vary in composition, and methods for their examina-
tion and valuation have therefore become necessary. The standards
resulting from such methods of examination, as in the case of the
resins, can, however, only be expressed by figures denoting the maximum
and minimum limits ; for although pharmaco-chemistry has made
great progress, we do not know as yet the constituents, either active or
inactive, of many drugs, to say nothing of being able to determine
their active principles quantitatively. Even with such drugs as contain
alkaloids that are known and can be quantitatively determined, it must
be taken into consideration that the presence, for example, of a certain
proportion of alkaloid does not always afford a guarantee for the good
quality and purity of the drug. The conditions with regard to the
galenical preparations made from the drugs are similar, but for these
many other analytical factors have become available as the result of
experience.
Drugs in a more extended sense, that is, those which are not of
vegetable origin, and also those drugs and preparations for which
complete quantitative tests are given in the Pharmacopoeia, have not
been included in this account of the subject. Furthermore, other
drugs have been excluded which are more correctly designated as crude
^ Cf, K. Dieterich, " On the chemical changes in the production of Drugs," Helfenberger
Annalen^ 1896, pp. 9-20,
223
224 DRUGS AND GALENICAL PREPARATIONS
products, such as the fats, oils, waxes, paraffins, and ceresins, since
they are dealt with in other Sections.
In view of the large number of drugs which are now technically
utilised on a large scale, and the limitations of space, it has naturally
only been possible to include here the more important. The present
standards of value and the requirements are in accordance with experi-
ence, and such as are recorded in the numerous works on pharmaceutical
chemistry and pharmaco-chemistr}'.
^.— DRUGS.
Gambir.
PALE CATECHU. CATECHU PALLIDUM. TERRA JAPONICA.
An extract prepared from the leaves and twigs of Ourouparia
Gambir (Hunter), Baillon.
Gambir and Catechu are frequently confused, but, although similar
in character, they are recognised in commerce as distinct products and
are obtained from totally different botanical sources. The British
Pharmacopoeia under the title of Catechu recognises the above-defined
product, to which the United States Pharmacopoeia gives the title of
Gambir. The fourth edition of the German Pharmacopoeia included
both of the above-mentioned products under the title of Catechu, bu.t
in the present edition the term is restricted to the so-called Black
Catechu or Cutch.
(a) Reaction for Idetitity (according to K. Dieterich). — If to 3 g.
of gambir there be added 25 c.c. oi N\i aqueous potassium hydroxide and
50 c.c. of light petroleum (sp. gr. O/OO at 15^), and the whole shaken
a few times in a glass separating funnel, after the separation of the two
layers the light petroleum will show in reflected light a green fluorescence,
increasing in intensity according to the time of action of the alkali
(gambir-fluorescin).
If to the dilute alcoholic solution a solution of ferric chloride be
added, an intense green coloration will be produced, which persists for
some time.
(b) Plant Residues. — If 20 parts of gambir be extracted with 200
parts of boiling alcohol, the insoluble residue, dried at 100', should
amount to not more than 6 parts, or 30 per cent.
(c) Determination of Ash. — i g. of gambir is carefully incinerated,
and the residue heated until, after cooling in a desiccator, a constant
weight is obtained. Both the British and United States Pharmacopoeias
require that gambir should yield not more than 5 per cent, of ash.
CATECHU. ERGOT 225
Pegu Catechu.
BLACK CATECHU. CATECHU NIGRUM. CUTCH.
An extract prepared from the heartwood of Acacia Catechu (Linne
fil.), Willdenow.
The following methods of examination and requirements are those
of K. Dieterich and of the German Pharmacopoeia : —
(a) Reaction for Identity. — If to a solution of Pegu catechu in dilute
alcohol a solution of ferric chloride be added, a green coloration ensues
which quickly changes to brown, and a precipitate is formed which gives
a bluish-violet colour with alkalis.
Pegu catechu does not give the fluorescence reaction of gambir.
(b) Plant Residues. — The plant residues, determined by the method
given under gambir, should not exceed 30 per cent.
(c) Determination of Ash. — If this determination be conducted as
given under gambir, Pegu catechu should yield not more than 6 per cent,
of ash.
Ergot.
ergota. secale cornutum.
(a) Determination of Extract, — To 10 g. of the finely crushed drug
100 c.c, of water are added, and the mixture allowed to stand for
twenty-four hours in a closed vessel. 20 c.c. of the filtered liquid are
then evaporated in a tared porcelain dish to dryness, and the residue
heated at 100" until the weight is constant. The weight of dry
extract, multiplied by fifty, expresses the percentage of water-soluble
extract yielded by the drug.
(b) Determination of Alkaloid (according to C. C. Keller). — 25 g.
of dry powdered ergot are extracted in a glass percolator with light
petroleum. When nothing more is removed by this solvent, the drug
is dried at a gentle heat, and brought into a tared, dry flask of
250 c.c. capacity. To the powder 100 g. of ether are added, and, after
ten minutes, milk of magnesia, prepared by mixing i g. of calcined
magnesia with 20 c.c. of water. The whole is shaken continuously
and vigorously until the ergot has agglomerated and the liquid becomes
clear. The shaking is then frequently repeated for half an hour,
after which 80 g. of the ethereal liquid, representing 20 g. of the drug,
are decanted. This solution is shaken three times in a separator with
25, 15, and 10 c.c. respectively of 0-5 per cent, hydrochloric acid. If
the extraction is not then complete, the liquid is shaken once or twice
more with 10 c.c. of 0-5 per cent. acid. The acid solution is shaken
with an equal volume of ether and an excess of ammonia, and this
extraction repeated twice with less ether. The ethereal liquids are
united, transferred to a tared flask, and the solvent removed. After
III P
226 DRUGS AND GALENICAL PREPARATIONS
treating the residue twice with a Httle ether, and evaporating the
latter, the flask with its contents is finally dried and weighed. The
weight of dry residue, multiplied by five, expresses the percentage of
alkaloid present in the ergot.
The following minimum and maximum values have been obtained : —
Extract . , . 1250 to 17-84 per cent.
Alkaloid . . . o-io „ 034 „
Requirements. — Ergot has an oily, unpleasant taste, and when mixed
with 10 parts of hot water should develop the odour peculiar to it,
but this should be neither ammoniacal nor rancid. It should yield
the largest possible amount of extract and of alkaloid.^
Isinglass.
ICHTHYOCOLLA. COLLA PLSCIUM.
{According to K. Die tench.)
(a) Preparatio7i of the Material. — The kinds of isinglass which are
capable of being divided into small pieces by means of shears, or a
knife, etc., are cut into strips i cm. in width, and these again into squares
of i cm. When the isinglass is very hard and cannot be divided in
this manner, it is best ground in a mill to a powder, which, however,
should be as coarse as possible, as the production of a fine powder
renders the subsequent operation of filtering extremely difficult.
(b) Dcternii)iation of the Moisture. — About 5 g. of the isinglass,
divided into small pieces as described above, is heated in a drying
oven at ioo°-i05° until the weight is constant.
(c) Determination of the Ash. — The perfectly dried isinglass remain-
ing from the determination of the moisture is heated by a small flame
in a fume chamber having a good draught until the material ceases to
emit dense vapours, which have the smell of burnt horn, and there is no
longer a strong intumescence. All possible care should also be taken
that the isinglass does not burn on to the vessel, so that after a while
a brownish black carbonaceous mass remains which is somewhat
readily combustible. By the application then of a larger flame, and
eventually moistening the material once with water, it ma)- completely
and quickly be reduced to a light brown ash.
(d) Determination of Potassium Carbonate in the Ash. — The ignited
residue obtained by the determination of the ash is taken up with
hot water, transferred to a small filter, and washed with about 75-100
c.c. of boiling, distilled water. The filtrate, after the addition of a
' For recent investigations concerning tlie allviiloids of ergot cf. J, Cliem. Soc.^ 1907,
91. 337 ; 19091 95. "23 ; 1910, 97, 284, 2592 ; 191 1, 99, 2336 ; /. Pharm. Chim., 1909 [vi.],
30. 145-
ISINGLASS 227
little tropreoHn or methyl orang-e, is titrated with A^io hydrochloric
acid, and the amount of potassium carbonate calculated either on the
original substance or on lOO parts of ash.
(e) Deterviination of the portions soluble and itisolnble in Boiling
Water. — lo g. of the finely divided isinglass are placed in a tall
enamelled vessel, preferably an internally enamelled litre measure, with
a spout, since glass beakers cannot be used for this purpose. About
500 c.c. of water are then added, and the mixture kept in a steam-bath
or water-bath until the isinglass floats for the most part on the
surface, so that it cannot burn on to the bottom of the vessel by the
subsequent treatment. It is then heated to boiling over a free flame,
and the boiling continued until the intense frothing has ceased or
abated. During the evaporation the froth, mixed with the impurities
contained in the isinglass, is firmly deposited on the sides of the
vessel. At this stage 400 c.c. of hot distilled water are added, and
the liquid evaporated to about 300 c.c. Pieces of the isinglass which
may adhere to the sides of the vessel are detached from time to time
by means of a glass rod, and brought into the boiling liquid. The
vessel is then removed from the burner, placed on a steam-bath, and
the solid material allowed to deposit, after which the liquid is decanted
as completely as possible into a graduated litre flask. About 800 g.
of boiling water are then added, the mixture again heated over a free
flame, and then evaporated to about 200 c.c, after which it is allowed
to deposit, and the liquid decanted as before. This operation is
repeated altogether three or four times, until the litre flask is about
nine-tenths filled. The flask, especially during warm weather, should
be kept hot on a steam-bath or water-bath during the entire pro-
cedure, in order to prevent the solution from spoiling. The vessel
employed for heating is cleaned from all adhering particles of isinglass
by means of a glass rod over which a piece of rubber tubing is drawn,
and a little water, and the entire residue finally washed into the
litre flask. The contents of the flask are then cooled to 15", filled up
to the mark, and the whole thoroughly shaken and filtered. 50-100
c.c. of the filtrate, which is more or less opalescent, are evaporated
in a tared dish, the residue dried at loo'-ios" until the weight is
constant, and calculated for the percentage of substance soluble in
boiling water. The sum of this percentage and that of the moisture,
subtracted from lOO, gives the percentage of substance contained in
the isinglass which is insoluble in boiling water,
(f) Swelling Value and Gelatinising Power. — To determine the
swelling value 10 g. of the isinglass are placed in a tared, enamelled
litre measure, 800 c.c. of hot water added, and, together with a glass rod
which is weighed at the same time, the mixture evaporated on a steam-
bath, with frequent stirring, to a total weight of about 510 g. If
228 DRUGS AND GALENICAL PREPARATIONS
gelatinisation does not ensue, when completely cold, an additional 50-
100 g. of water are evaporated, and it is again allowed to cool. When
the point is thus determined at which a jelly is formed, the whole is
weighed. If, for example, the weight is found to be 370 g., the
gelatinising power is i : 36, or the swelling value is 36.
Since it has been found by experience that the gelatinising power
is affected by heating over a free flame to boiling and subsequent
evaporation, a steam-bath should be employed so that the temperature
does not exceed loo^
(g) Deterniination of the Fat. — 10 g. of the finely divided isinglass
are weighed into an extraction thimble, placed in a Soxhlet apparatus,
and extracted for three hours with ether of sp. gr. 0720. The contents
of the extraction flask are then evaporated, and dried for a short time
at 100' until the weight is constant, the weight of the flask itself having
been previously determined. The contents of the extraction thimble
are also dried, and, after all the ether has evaporated, used for the
determination of the glutin,
(h) Deterniinatio)i of the Collagen. — The combined weights of the
soluble and insoluble portions, minus the fat, expresses the amount of
collagen.
(i) Deter minatioji of the Crude Glutin. — The dried contents of the
extraction thimble, remaining from the determination of the fat,
contains the so-called collagen, that is, the pure gelatin-yielding
tissue freed from fat, and this is used for the determination of the
glutin as follows : — The contents of the thimble are completely extracted
with boiling water, in the same manner as described for determining
the portion of the isinglass soluble in boiling water (cf. e). 500 c.c. of
the filtrate which is finally obtained, corresponding to 5 g. of the
isinglass deprived of fat, i.e. collagen, are placed in an accurately
weighed beaker, and evaporated to about 50 c.c. To the solution,
while still warm, 200-300 c.c. of absolute alcohol are gradually added in
a thin stream, and the precipitate thus produced allowed to stand for
at least twelve hours, or until the supernatant liquid has become
perfectly clear. Although the glutin is usually precipitated as an
extremely viscid, white mass, opalescent on the surface, it is best to
bring the mixture on to a small, weighed filter. The filtrate, together
with the alcohol used for washing the glutin and the filter, are then
evaporated in a tared dish, the residue being finally dried and weighed
(extractive matter not precipitable by alcohol).
It may be noted that in the technical preparation of glutin the
isinglass is usually treated with dilute hydrochloric acid before being
deprived of fat, in order to remove inorganic constituents. This
procedure cannot be adopted in the cjuantitativc determination of
glutin, for the reason that other constituents would be dissolved
ISINGLASS 229
together with the inorganic substances, and the action of hydrochloric
acid is too strong for analytical purposes. If it is desired to ascertain
the nature of the small amount of inorganic matter present, the ash
yielded by the glutin is determined.
(k) Determination of the Acid Value. — If the filtrate obtained by the
determination of the soluble portion of the isinglass, when tested with
sensitive litmus paper, gives a distinctly acid reaction, the acid value of
the solution may be ascertained as follows : — 2 g. of isinglass, together
with 100-150 c.c. of distilled water, are placed in a flask of 200 c.c.
capacity, the liquid heated for about three hours on a steam-bath, then
brought once to boiling over an open flame, allowed to cool, filled up
to the mark, and filtered after being well shaken. 50 c.c. of the filtrate
are finally titrated with Njio aqueous potassium hydroxide, using
phenolphthalein as the indicator.
(1) Determination of the Iodine Value} — Since isinglass belongs to
the albuminoids, or albumen-like substances, its property of absorbing
iodine may be used for its identification and the detection of adultera-
tions, as in the case of albumen itself. The determination of the iodine
value may be carried out as follows : — 50 c.c. of the same filtrate as that
employed for the determination of the acid value or of the filtrate used
for determining the soluble portion of the isinglass, representing 0-5 g.
of the latter, are mixed with 20 c.c. of an N\\o solution of iodine in
potassium iodide in a glass-stoppered bottle of 500-750 c.c. capacity.
The mixture is then well shaken, allowed to stand for twenty-four
hours, and the excess of iodine titrated back with A710 sodium
thiosulphate, using starch as an indicator. The number of c.c. of N\io
iodine solution used, multiplied by 0-012697 and 200 respectively, gives
the iodine value of the sample.
(m) Test for Sulphur. — The test for sulphur is important, inasmuch
as isinglass is often artificially bleached with sulphurous acid, and such
a product is generally not so good as that obtained by natural methods.
The test consists in fusing the isinglass with a mixture of potassium
nitrate and sodium carbonate, and testing the aqueous extract of the
fused mass for sulphate in the usual manner,
(n) Test for Starch. — The test for starch may also serve as one
for identity, since pure isinglass gives no reaction for starch, whereas
artificial products may do so. To the aqueous solution a little solution
of iodine in potassium iodide is added, when pure isinglass will show a
reddish-brown, but no blue coloration.
(o) Determination of the Optical Rotation of the Glutin Solution. —
The aqueous glutin solution is laevo-rotatory, and the optical rotation
is therefore also to be determined as proof of identity of a natural
isinglass.
1 Cf. K. Dieterich, Hel/enberger Annalen, 1897, pp. 1-29.
230
DRUGS AND GALENICAL PREPARATIONS
Table 38.
Analytical Values for Isinglass (K. Dieterich).
(Expressed in round numbers.)
American :
Adulterated
Rnssian :
Salianaky,
Chinese.
Brazilian,
Venezuelan,
Saliansky,
iniprepnated
with glue.
Beluga, Samovy.
Jlaracaibo,
and scraps.
Moisture .
13 10 20 p. c.
11 to 17 p. c.
13 to 18 p.c.
16 p. c.
Ash .
O'O to 1"7 p. c.
0-9 to 2-3 p. c.
1 to 3-7 p.c.
0-6 p.c.
Potassium carbonate in
100 parts of ash .
1 8 to 33 p. c.
32 to 53 p. c.
6 to 37 p.r.
72 p.c. !
Soluble portion
65 to 81 p. c.
68 to 86 p. c.
59 to 75 p. c.
82 p. c.
Insoluble ponion
1 to 19 p. c.
2 to 15 p.c.
9 to 25 p. c.
1*5 p. c.
Swelling value .
0 to 49
14 to 25
16 to 55
25
Fat .
0-1 to 1-2 p. c.
0-1 to 1-2 p.c.
0-1 to 0-8 p. c.
0-3 p.c.
Collagen .
79 to 85 p. c.
81 to 88 p. c.
80 to 87 p. c.
83 p. c. !
Crude glutin
66 to 82 p. c.
69 to 74 p. c.
66 to 75 p. c.
82 p c. !
Acid value
0 to 6-0
0
0 to 2-76
3-8 p. c. !
Iodine value
19 to 45
39 to 46
30 to 47
37
Ash of crude glutin .
. 0-4 to 0-7 p. c.
0-67 p.c.
0-4 to 0-7 p.c.
0-4 to 0-7 p.c.
Optical rotation of crude
glutin .
I laevo
laevo
laevo
\xvo
)
Test for sulphur
positive
positive
positive
positive
OriUM.
{According to K. Dieterich and the German Pharmacopaia!)
(a) Dctcrniinatioji of Moisture. — 2 g. of the opium are heated in a
drying oven at 100° until the weight is constant.
(b) Deter jumatioji of Ash. — The dried opium is incinerated, and the
residue ignited until the weight remains constant.
(c) Determination of MorpJdne. — The following method is that of the
German Pharmacopoeia: — 7 g. of opium, dried at 60^ and in moderately
fine powder, are triturated with 7 g. of water, the mixture being then
washed with water into a flask and the total weight made up to 61 g.
by the further addition of water. After having stood for an hour with
frequent shaking, the mixture is transferred to a dry, folded filter of
10 cm. diameter. To 42 g. of the filtrate ( = 488 g. opium) there is then
added 2 c.c. of a mixture of 17 g. solution of ammonia (sp. gr. 0960) and
83 g. of water, and the whole filtered immediately through a dry, folded
filter into a flask. To 36 g. of the filtrate ( = 4 g. opium) are then added,
with agitation, 10 c.c. of ethyl acetate and another 5 c.c. of the above-
mentioned dilute ammoniacal liquid. After corking the flask, the
contents are shaken for ten minutes, then 20 c.c. more of ethyl acetate
added, and the whole allowed to stand for a quarter of an hour with
occasional gentle agitation. The ethyl acetate layer is then first
OPIUM 231
transferred as completely as possible on to a smooth filter of 8 cm.
diameter, lO c.c. of ethyl acetate added to the aqueous liquid remaining
in the flask, the mixture agitated for a moment, and the ethyl acetate
layer then again brought on to the filter. After the ethereal liquid has
ceased to pass, the aqueous solution is poured on the filter, without
regard to the crystals adhering to the sides of the flask, and the filter as
well as the flask washed three times with water which has been saturated
with ether, using 5 c.c. each time. When the liquid has thoroughly
drained from the flask, and ceased to drop from the filter, both the flask
and filter are dried at 100°.
In order to determine the amount of morphine gravimetrically, the
dried contents of the filter are transferred to the previously tared flask
by means of a camel's-hair brush, and the whole heated at 100° until the
weight is constant. The weight of substance, when multiplied by 25,
then represents the percentage amount of anhydrous morphine in the
opium. The German Pharmacopoeia directs, however, that the morphine
shall ultimately be determined by the following volumetric method : —
The crystals of morphine, as obtained above, are dissolved in 25 c.c. of
Njio hydrochloric acid, the solution poured into a graduated flask of
100 c.c. capacity, the filter, flask, and stopper then carefully washed with
water, and the solution finally diluted to the measure of 100 c.c. 50 c.c.
of this solution, representing 2 g. of powdered opium, are placed in a
flask of about 200 c.c. capacity, and about 50 c.c. of water added,
together with so much ether that the latter forms a layer about i cm. in
depth. After the addition of 10 drops of iodo-eosine solution, Njio
potassium hydroxide is allowed to flow into the liquid, shaking actively
after each addition, until the lower aqueous layer has assumed a pale
red colour. For this purpose not more than 4-1 c.c. of Njio potassium
hydroxide should be required, so that at least 8-4 c.c. of A^io hydro-
chloric acid are used for the neutralisation of the morphine present.
This corresponds to a minimum of 12 per cent, of morphine in the
opium, since i c.c. Njio hydrochloric acid = 0-02852 g. of morphine,
Ci7Hjg0.3N, with iodo-eosine as the indicator.
The British Pharmacopoeia (1898) requires that opium dried at 100°
should contain about 10 per cent, of anhydrous morphine. The
United States Pharmacopoeia (eighth revision) specifies that opium in
its normal moist condition should contain not less than 9 per cent, of
crystallised morphine, Ci7H^,,03N, H2O, or, when dried at 85° not less
than 12 per cent, nor more than 12-5 per cent, of crystallised morphine.
It should be noted, however, that these percentages of morphine are
based upon the methods of assay prescribed by the respective
pharmacopoeias, since different methods are likely to yield somewhat
divergent results.
(d) Microscopic Test, especially for starch.
232 DRUGS AND GALENICAL PREPARATIONS
The following variations in composition have been found in the
examination of opium : —
Moisture . . . 7-35 to 24-13 per cent.
Ash . . . . 3-55 „ 5-49
Aqueous extract . . 45-00 „ 45-25 „
Morphine . . . 9-98 „ 15-82 „
Vegetable Drugs.
The method of examination of vegetable drugs should be of an
individual character, in accordance with the purpose for which the
drug is to be used, and with due consideration of the preparation that
is to be made from it. In cases where official preparations are
concerned the method of testing adopted should be in accord with
the respective directions given in the current pharmacopceias. Since
these examinations only involve the determination of comparative
values, and not exact figures for the purpose of manufacture, H. Mix
and K. Dieterich regard it as sufficient to extract the drug once
only, and to allow not more than forty-eight to sixty hours for the
operations of expression, filtration, evaporation, and drying to constant
weight.
I. BARKS.
Cascara Sagrada.
The dried bark o{ Rkaninus PursJiimia, DC.
DetenntHntt'oH of Extract. — The bark is extracted by the following
methods, according as it is to be used for the preparation of
(i) aqueous extract ; (2) alcoholic extract ; or (3) liquid extract.
1. As indicated under Ergot (p. 225).
2. As indicated under Flowers (III.), cither with 68 per cent,
alcohol, or with a mixture of 2 parts by weight of 90 per cent,
alcohol and 3 parts of water.
3. Like the preceding, with a mixture of i part by weight of
90 per cent, alcohol and 2 parts of water.
The German Pharmacopoeia requires that the bark, when completely
extracted with a mixture of 3 parts of alcohol and 7 parts of
water, should yield at least 24 per cent, of extract, and that, when
incinerated, it should leave not more than 6 per cent, of residue.
Cascarilla.
The dried bark of Crot07i Elutcria, Bennett.
Determination of Extract. — As described in the introduction to
Leaves (p. 239), in the proportion of 10 : 200.
VEGETABLE DRUGS 233
Cinchona.
The British, United States, and German Pharmacopceias all
recognise the dried bark of the stem and branches of cultivated
plants of Cinchona succirubra, Pavon. In addition to the latter the
United States Pharmacopoeia, under the general title of CincJiona,
comprehends the dried bark of Cinchona Ledgenana, Moens, C. Calisaya,
Weddell, C. officinalis, Linne, and hybrids of these with other species
of CincJiona.
(a) Aqueous Extract — lo g. of the finely powdered bark are
mixed in a beaker with lOO c.c. of cold water, and the mixture allowed
to stand for twenty-four hours, with frequent stirring. It is then
allowed to settle, 20 c.c. of the filtered liquid ( = 2 g. of bark) evaporated,
and the residue dried until of constant weight.
(b) Alcoholic Extract. — Proceed as under {a), but with the use of
68 per cent, alcohol.
The following yields of extract have been obtained : —
Dry aqueous extract . . . ir-i to 26-0 per cent.
Dry alcoholic extract . . . 34.0 „ 39-5 „
(c) Determination of Alkaloid. — The following method is that of the
German Pharmacopoeia : —
To 12 g. of the finely powdered bark, contained in a flask, are
added 30 g. of chloroform and 30 g. of ether (sp. gr. 0720), and, after
vigorous shaking, 5 g. of solution of sodium hydroxide (15 per cent.)
and 5 g. of water. The mixture is then allowed to stand for three
hours, with frequent vigorous shaking. 60 g. of ether are subsequently
added, the whole being well shaken, and, after the liquid has become
clear, 80 g. of the chloroform-ether mixture ( = 8 g. of cinchona bark)
are filtered through a dry, well-covered filter into a flask, and about
two-thirds of the solvent distilled off. The cooled residue is transferred
to a glass separator (I.), the flask washed three times with a mixture
of 2 parts of chloroform and 5 parts of ether, using 5 c.c. each
time, then once with 20 c.c. of dilute hydrochloric acid (containing i per
cent, of acid of sp. gr. 1-126), these liquids being also brought into the
separator, and, after the addition of so much ether that the chloroform-
ether mixture floats on the surface of the acid liquid, the entire
mixture is vigorously shaken for two minutes. When the liquids have
become clear, the hydrochloric acid solution is allowed to flow into
another separator (II.), and the ethereal liquid shaken twice successively
in the same manner with the above-mentioned dilute hydrochloric acid,
using 5 c.c. each time.
To the combined hydrochloric acid liquids are added 5 c.c. of
chloroform, then a solution of sodium carbonate until the reaction is
234 DRUGS AND GALENICAL PREPARATIONS
alkaline, and the mixture at once shaken vigorously for two minutes.
When the liquids have become perfectly clear, the chloroform extract
is allowed to flow into another separator (III.), and the alkaline liquid
shaken three times successively with chloroform, using 5 c.c. each
time. To the combined chloroform extracts are added 25 c.c. of
N/io hydrochloric acid, and so much ether that the chloroform-ether
mixture floats on the surface of the acid liquid, after which the whole
is well shaken for two minutes. When it has become perfectly clear,
the acid liquid is filtered through a small filter, moistened with water,
into a graduated flask of 100 c.c. capacity, the chloroform-ether
mixture shaken three times successively for two minutes with water,
using 10 c.c. each time, these aqueous liquids being also passed through
the same filter, which is finally washed with water, and the entire
aqueous, acid liquid diluted with water to 100 c.c. 50 c.c. of this
liquid ( = 4 g. of cinchona bark) are placed in a flask, about 50 c.c. of
water added, and then a freshly prepared solution of a fragment of
haematoxylin in i c.c. of alcohol. Subsequently N'lO potassium
hydroxide solution is added to the liquid, with gentle agitation, until
the mixture assumes a deep yellow colour, which by vigorous agitation
quickly passes into bluish-violet. For this purpose not more than
4-1 c.c. of iV/io potassium hydroxide solution should be required, so
that at least 84 c.c. Njio hydrochloric acid would be used up for the
neutralisation of the alkaloids present. This would correspond to a
minimum of 6-5 per cent, of alkaloids in the bark (i c.c. Njio hydro-
chloric acid =0-0309 g. quinine and cinchonine, using haematoxylin as
the indicator).
5 c.c. of the alkaloid solution which was not used for the titration,
when mixed with i c.c. of chlorine water, should give a green coloration
on the addition of solution of ammonia.
Standards for Alkaloid. — The German Pharmacopoeia requires that
red cinchona bark, when assayed by the above method, should yield
at least 6-5 per cent, of alkaloids of the composition C20H04O.2N.,
(quinine) and Cj,,H.2.pN2 (cinchonine), having an average molecular
weight of 309. The British Pharmacopcjeia requires between 5 and
6 per cent, of total alkaloids, of which not less than half should consist
of quinine and cinchonidine, when estimated by the official method.
The United States Pharmacopoeia requires for Ciuclioua succirubra not
less than 5 per cent, of anhydrous cinchona alkaloids ; for the species
mentioned under Cinchona not less than 5 per cent, of total anhydrous
cinchona alkaloids, and at least 4 per cent, of anhydrous ether-soluble
alkaloids, when a.ssayed by the official process.
Since the various pharmacopruias prescribe different methods of
assay, and the percentage of alkaloids required to be contained in a
bark is based on a particular method, it is obvious that this is to be
BARKS 235
considered in connection with the vakiation of any given species of
cinchona which is to be used for pharmacopoeial purposes.
Cinnamon and Cassia.
The true Cinnamon consists of the dried inner bark of the shoots
of Cimiauioiimm zeyla?iic?im, Breyne, and is distinguished in commerce
as Ceylon Cinnamon.
Cassia bark is obtained from one or more undetermined species of
CimiauioDiHvi grown in China, and is also known as Chinese Cinnamon.
The British and German Pharmacopoeias recognise only Ceylon
Cinnamon, whereas the United States Pharmacopoeia also includes
Saigon Cinnamon, which is the bark of an undetermined species of
Cinnmnoviuvi.
Determination of Extract. — The yield of aqueous extract is deter-
mined as stated under Ergot, and that of alcoholic extract by the
method described under Flowers (III.), with the use of 68 per cent,
alcohol.
Determination of Aldehyde. — The yield of cinnamic aldehyde may
be determined by the method of J. Hanus.^
The German Pharmacopoeia requires that cinnamon bark should
yield on ignition not more than 5 per cent, of ash.
Condurango.
The probable botanical source of this bark is Marsdenia cundnrango,
Reichenbach fils.
Determination of Extract. — When the bark is to be used for the
preparation of extract, the yield of alcoholic extract is determined as
under Flowers (III.), with the use of a mixture of 2 parts by weight
of 90 per cent, alcohol and i part of water. For the preparation of a
liquid extract it is treated in the same manner, but with a mixture of
I part by weight of alcohol and 3 parts of water. P^or a tincture the
extraction is conducted with 68 per cent, alcohol.
Frangula.
The dried bark oi Rhammis frangula, Linne.
Determination of Extract. — The bark is extracted by one of the
following methods, according to its intended use for the preparation of
(i) an aqueous extract ; (2) an alcoholic extract; (3) a liquid extract;
or (4) a tincture.
(i) It is extracted with cold water in the manner described under
Ergot (p. 225), or with boiling water as described in the introduction
to Leaves (p. 239), in the proportion of 10 : 200.
1 Z. Unters. Nahr. it. Genussin., 1 903, 6, 817 ; /. Soc. Chem. fnd., 1 903, 22, 1 1 54.
236 DRUGS AND GALENICAL PREPARATIONS
(2) In the manner described under Flowers (III.), ^vith a mixture
of 2 parts by weight of 90 per cent, alcohol and 3 parts of water.
(3) In the same manner, with a mixture of 3 parts by weight of 90
per cent, alcohol and 7 parts of water.
(4) In the same manner, but with 6S per cent, alcohol.
I!. BULBS.
SquiH.
Squill consists of the bulb of Urgitiea maritima (Linnc), Baker,
divested of its dry, membranous outer scales, cut into slices, and dried.
Determination of Extract. — The squill, in moderately fine powder, is
extracted with either cold or hot water, or with 68 or 90 per cent,
alcohol, according to the methods which have been described, and
adhering as closely as possible to the directions for making the
respective preparations.
The German Pharmacopoeia requires that squill shall yield on
ignition not more than 5 per cent, of ash.
in. FLOWERS.
In the case of flowers the alcoholic extract is generally determined
in accordance with the following method : —
(a) Alcoholic Extract. — To 10 g. of the ground flowers, contained in
a flask, are added 100 c.c. of a mixture of i part by weight of alcohol
and 2 parts of water. The flask is then closed, allowed to stand for
twenty-four hours, with frequent shaking, and, after the material has
deposited, the liquid is filtered. 20 c.c. of the filtrate ( = 2 g. of the
drug) are then evaporated in a tared dish, and the residue dried at 100°
until the weight is constant.
(b) The official flowers should conform to the requirements of the
respective pharmacopoeias.
Chamomile Flowers.
The Chamomile Flowers of the British and United States
Pharmacopoeias consist of the dried flower heads of Anthemis nobilis,
Linn6, whereas the German Pharmacopoeia recognises only the dried
flower heads of Matricaria cJianioniilla, Linne, which are commonly
known as German Chamomile.
Determination of Extract. — The German chamomile flowers, accord-
ing to their intended use for the preparation of (i) tincture ; (2) extract
or syrup ; or (3) oil, are extracted by one of the following methods : —
(i) As described above, with 68 per cent, alcohol.
(2) As described above, with a mixture of 2 parts by weight of 90
per cent, alcohol and 3 parts of water.
FLOWERS. FRUITS 237
(3) In the same manner, with 200 c.c. of a mixture of 150 g. of 90
per cent alcohol and 2 g. of a solution of ammonia (sp. gr. 0-960).
All extractions of chamomile flowers should be conducted in the
proportion of 10 g. of the flowers to 200 c.c. of the respective liquid.
Red Poppy Petals.
Red Poppy petals are obtained from Papmier Rkoeas, Linne.
Determmatioii of Extract. — This is conducted according to the
method described in the introduction to Leaves (p. 239), in the pro-
portion of 10 : 200, but the temperature of extraction should not exceed
about 35°-40°, and 0-2 g. of citric acid should be added to 10 g. of the
red poppy petals or to 200 c.c. of water respectively.
Rose Petals.
This title refers to the petals of the Pale Rose or Cabbage Rose,
which are obtained from Rosa centifolia, Linne.
Determination of Extract. — The extraction is conducted in the
proportion of 10 parts of the petals to 200 parts of liquid by one of
the following methods, according to the use of the petals for the
preparation of (i) an alcoholic extract ; or (2) for honey of rose.
(i) By the above general method, with the use of 68 per cent,
alcohol.
(2) As described in the introduction to Leaves (p. 239), in the pro-
portion of 10 : 200.
IV. FRUITS.
Buckthorn Berries.
The fruit of Rhainnns cathartica, Linne.
Determination of Extract. — The well-crushed berries are extracted
by the use of 10 parts of berries to lOO parts of solvent, as described
in the introduction to Leaves (p. 239).
Capsicum. Spanish Pepper. Cayenne Pepper.
In the German Pharmacopoeia Capsicum is defined as the dried, ripe
fruit of Capsicum annuum, Linne, whereas the British and United States
Pharmacopoeias recognise the smaller fruit of Capsicum minimum,
Roxb. {C. fastigiatum, Blume).
Determination of Extract. — According to the intended use of
capsicum for the preparation of (i) a liquid extract; (2) a tincture;
or (3) a thick extract, it is extracted with one of the following solvents,
as indicated under Flowers (III.).
(i) With 90 per cent, alcohol,
(2) With 68 per cent, alcohol.
238 DRUGS AND GALENICAL rilEPARATIONS
(3) With a mixture of 2 parts by weight of alcohol and 3 parts of
water.
The German Pharmacopceia requires that powdered capsicum should
yield on ignition not more than 6-5 per cent, of ash.
Elder Berries.
The fruit of Sanibitcus Jiigra, Linnc.
Dctcy))n)iation of Extract. — This is conducted as indicated under
Buckthorn berries.
Fennel.
The ripe fruit of Fooniciiluiii capillaccuui^ Gilibert.
Dctcr)}iination of the Essential Oil (according to K. Dieterich). —
10 g. of the finely crushed fruit are distilled in a current of steam until
the distillate (about 500 c.c.) no longer possesses an odour. The
distillate is then saturated with common salt and allowed to stand for
twenty-four hours, after which the oil is extracted with 50 c.c. of ether
by shaking in a separator. The ethereal liquid is filtered through a
little well-dried salt, the latter subsequently washed with 20 c.c. of ether,
and the combined liquids allowed to evaporate spontaneously in a beaker
which is covered with finely perforated filter paper. When the ether
has completely evaporated, the residue is dried for twelve hours in a
desiccator, and weighed.
The yield of essential oil has been found to be from 3-0 to 40 per
cent.
The German Pharmacopceia requires that powdered fennel fruit
should yield on ignition not more than 10 per cent, of ash.
Juniper Berries.
The dried, ripe fruit oi ftcniperus communis^ Linne.
Determination of Extract. — As described in the introduction to
Leaves (p. 239).
The juniper berries are previously well crushed, but extracted
only in the proportion of 10 parts of berries to 100 parts of liquid,
and the heating for a quarter of an hour in a hot-water bath is
omitted.
The German Pharmacopcuia requires that powdered juniper berries
should yield on ignition not more than 5 per cent, of ash.
Parsley Fruit.
The fruit of Caruni Petroseliiinm, Jicnth. et Hook.
Determination of the Essential 6?// (according to K. Dieterich). — As
described under Fennel, and according to the Supplement to the
German Pharmacopoeia, 4th edition.
HERBS. LEAVES 239
Poppy Capsules.
Poppy capsules or heads are the dried, immature fruits of Papaver
soniniferuni, Linne.
Detcnnination of Extract. — This is conducted as described under
Flowers (III.), with lOO c.c. of a mixture of i part by weight of 90 per
cent, alcohol and 9 parts of water.
V. HERBS.
The general directions for the examination of herbs consist in
determining either the yield of alcoholic extract, as described under
Flowers (III.), or the aqueous extract, as described under Leaves (VI.).
When the herbs are to be used for making extracts, the prescribed
directions for the respective extract should be strictly followed. The
herbs should be used in a finely cut state.
Carduus Benedictus (Blessed Thistle).
The dried leaves and flowering branches of Cnicus benedictus, Linne.
Dctermmation of Extract. — As described under Alexandrian Senna
leaves (p. 244).
Linaria (Common Toad-flax).
The flowering plant of Linaria vulgaris. Miller.
Determination of Extract. — As described under Flowers (III.), with
the use of 100 c.c. of a mixture of 150 g. of 90 per cent, alcohol and
5 g. of a solution of ammonia (sp. gr. 0-960).
Marjoram (Sweet Marjoram).
The leaves and flowering stems of Origanum Majorana, Linne.
Determination of Extract. — As described under Linaria.
Milfoil or Yarrow.
The flowering plant oi Achillea Millefolium, Linne.
Determi)iation of Extract. — As described under Flowers (III.), with
a mixture of 2 parts by weight of 90 per cent, alcohol and 3
parts of water, and in the proportion of 10 g. of herb to 200 c.c.
of liquid.
VI. LEAVES.
The general method for the examination of leaves consists in
determining the yield of water-soluble extract. The procedure is as
follows : —
(a) Determinatioji of Extract. — To 10 g. of the finely cut leaves,
contained in a tared beaker, 100 g. of boiling water are added, the
240 DRUGS AND GALENICAL PREPARATIONS
whole heated for ten to fifteen minutes in a hot-water bath, and allowed
to stand for twenty-four hours. The amount of evaporated water
is then replaced, the liquid filtered, 20 c.c. of the filtrate ( = 2 g. of the
drug) evaporated to dryness, and the residue heated at 100° until
of constant weight.
(//>) Those leaves which are officially recognised are also to be
tested according to the respective pharmacopcuia.
The examination is somewhat differently conducted with belladonna,
coca, digitalis, senna, and menyanthes leaves.
Belladonna (Deadly Nightshade).
The dried leaves of Atropa Belladonna, Linnc, which, according to
the German Pharmacopoeia, should be collected from plants growing
wild and at the time of flowering.
Determination of Hyoscyamine, C17H.23O3N. — The following method
is that of the German Pharmacopoeia : —
To 20 g. of finely powdered belladonna leaves, contained in a
flask, are added 120 g. of ether, and, after vigorous shaking, 5 g. of
a solution of sodium hydroxide (15 per cent.) and 5 g. of water. The
mixture is then allowed to stand for an hour, with frequent and
vigorous shaking. When the liquid has become perfectly clear,
60 g. of the ethereal solution (= 10 g. of belladonna leaves) are filtered
through a dry, well-covered filter into a flask, and about two-thirds
of the ether distilled off. The cooled residue is transferred to a glass
separator (I.), the flask washed three times with ether, using 5 c.c. each
time, and then once with 10 c.c. of dilute h)'drochloric acid (i part
of acid, sp. gr. 1-126, to 49 parts of water), these liquids being also
brought into the separator, and the whole shaken vigorously for two
minutes. When the liquids have become perfectly clear, the hydro-
chloric acid solution is run into another separator (II.). and the ethereal
liquid again shaken in the same manner with two successive portions,
of 5 c.c. each, of dilute hydrochloric acid (1:49), the latter having
previously been used for the further rinsing of the flask.
To the combined hydrochloric acid extracts are added 5 c.c. of
chloroform, then sufficient solution of sodium carbonate to impart an
alkaline reaction, and the mixture at once shaken vigorously for two
minutes. After having become perfectly clear, the chloroform extract
is run into another separator (III.), and the aqueous, alkaline
liquid again shaken three times successively with chloroform, using
5 c.c. each time. To the combined chloroform extracts 20 c.c. of
A710 hydrochloric acid are then added, and so much ether that the
chloroform-ether mixture floats on the surface of the hydrochloric acid,
after which the whole is shaken vigorously for two minutes. After
having become perfectly clear, the acid liquid is filtered through a small
LEAVES 241
filter, previously moistened with water, into a colourless glass flask of
about 2(X) c.c. capacity, the chloroform-ether mixture again shaken
three times successively for two minutes with water, using lo c.c. each
time, these liquids being passed through the same filter, which is
subsequently washed with water, and the entire liquid finally diluted
to about 100 c.c.
After having added so much ether that the layer of the latter is
about I cm. in depth, and lo drops of iodo-eosine solution, iV/ioo
solution of potassium hydroxide is added to the liquid, the mixture
being actively shaken after each addition, until the lower aqueous
layer has assumed a pale red colour. For this purpose not more than
9-6 c.c. of N/ioo potassium hydroxide should be required, so that at
least 10-4 c.c. of N/ioo hydrochloric acid would be used up for the
neutralisation of the alkaloid present. This would correspond to a
minimumi of 0-3 per cent, of hyoscyamine in the leaves (i c.c. Njioo
hydrochloric acid = 0-00289 g. hyoscyamine, using iodo-eosine as the
indicator).
The United States Pharmacopceia, in conformity with the above
standards, requires that belladonna leaves should yield not less than
0-3 per cent, of mydriatic alkaloids, when assayed by the official process.
The amount of dry, aqueous extract yielded by belladonna leaves
has been found to vary from 23-9 to 32-9 per cent.
The German Pharmacopceia requires that powdered belladonna
leaves should yield on ignition not more than 15 per cent, of ash.
Coca.
The dried leaves of Erythroxyluvi Coca, Lamarck.
Determination of Cocaine (according to C. C. Keller). — To 12 g. of
powdered coca leaves, contained in a flask of 150 c.c. capacity, are
added 120 g. of ether, then after fifteen minutes 10 c.c. of a solution of
ammonia (sp. gr, 0-960), and the whole frequently and vigorously
shaken. After half an hour, 20 c.c. of water are added, and the separa-
tion of the drug effected by prolonged, vigorous shaking. Subsequently
100 g. of the dark green, ethereal solution (=10 g. of the leaves) are
decanted, and allowed to stand for a short time, when a small amount
of the finest particles of the drug, together with drops of water, will be
deposited at the bottom of the flask. The clear solution is then trans-
ferred to a separator, shaken first with 50 c.c. of 0-5 per cent, hydro-
chloric acid, and then once again with 25 c.c. of the same dilute acid.
The acid, aqueous liquid is placed in another separator, made alkaline
with ammonia, and shaken twice successively with ether, using 40 c.c.
each time. The clear, ethereal solution is then transferred to a tared
flask, the ether distilled off, and the residue dried in a water-bath and
weighed.
Ill Q
242 DRUGS AND GALENICAL PREPARATIONS
The standard is about i per cent, of cocaine.
Although the German Pharmacopoeia restricts the definition of
Coca to the leaves of ErytJiroxylum Coca, which is the Bolivian or
Huanuco variety, the British and United States Pharmacopoeias also
recognise the Peruvian or Truxillo Coca, from E. Tnixillcnse, Rusby.
The latter requires the dried leaves of either species to contain not less
than 0-5 per cent, of the ethcr-solublc alkaloids of Coca, when assayed
by the prescribed method.^
Digitalis.
The dried leaves of flowering plants o{ Digitalis purpurea, Linne.
Determination of Digitoxin (according to C. C. Keller). — 20 g. of the
leaves are thoroughly extracted in a suitable apparatus, or by percola-
tion, with 70 per cent, alcohol. The completeness of this operation may
be controlled by allowing 3-4 c.c. of the last portions of the percolate to
evaporate, taking up the residue with about 3 c.c. of water and two
drops of hydrochloric acid, and testing the filtered liquid with a solution
of tannin, when no appreciable turbidity should ensue.
The entire percolate is evaporated in a porcelain dish on the
water-bath, with active stirring, to about 25 g., in order to remove the
alcohol, the residue then taken up with water, washed into a flask of
250 c.c. capacity, and the total weight brought to 222 g. To this turbid
solution of the extract are added 25 g. of a solution of basic acetate of
lead, when a copious precipitate will be formed. By a gentle swaying
of the flask a uniform mixture is obtained, but it should not be strongly
shaken, otherwise much froth will be produced, which renders the
subsequent filtration more difficult. The very voluminous precipitate,
when washed and dried, weighs about 7 g., so that 12 g. of the
liquid correspond to i g. of digitalis leaves. The thick mixture is
brought on to a filter of about 18 cm. diameter, 132 g. of the filtrate
collected, and to this clear, pale yellow liquid a solution of 5 g. of
sodium sulphate in 7 g. of water is added, to precipitate the excess of
lead. If the precipitation is conducted in an Erlenmeyer flask, which
after some time is placed in a sharply inclined position, the lead
sulphate will be deposited in such a manner that in the course of four or
five hours 1 30 g. of the liquid ( = lo g. of digitalis leaves) can be decanted
perfectly clear, and the difficulty of collecting and washing the precipi-
tate on a filter is thus avoided. The liquid is then placed in a
separator, and 2 c.c. of a solution of ammonia (10 per cent.) added,
when it will become somewhat darker in colour, but must remain per-
fectly clear, indicating that only traces of lead remain ; otherwise an
emulsion will be formed by the subsequent extraction. It is then
' For a comprehensive review of the methods of assay suggested for coca leaves, see Arch,
Pharm., igio, 248, 303-336 ; /. Soc. Chem. Ind., 1910, 29, 897.
LEAVES 243
shaken four or five times successively with chloroform, using 30 c.c. each
time. The united and only slightly turbid chloroform solutions are
passed through a double, pleated filter of 8-9 cm. diameter, which has
previously been moistened with chloroform, when the liquid will bi*
obtained perfectly clear. It is then transferred to a tared Erlenmeyer
flask, and the chloroform distilled off in a water-bath, when the digitoxin
will remain as a yellow varnish. If the digitoxin is extracted from an
acid instead of from an alkaline solution, it will be obtained in a much
less pure form.
The crude digitoxin contains small amounts of fat, and especially
the odorous principles of the digitalis, and therefore requires purifica-
tion. For this purpose the residue is dissolved in 3 g. of chloroform,
and to the solution are added 7 g. of ether and 50 g. of light petroleum,
when the digitoxin will be precipitated in white flakes, which are
rapidly deposited, while the liquid, if actively shaken, will become
perfectly clear. In order to obtain the precipitate in a suitable
condition for weighing, a variety of methods may be adopted.
The precipitate may be collected on a small, pleated filter, and the
flask and filter washed vvith a little light petroleum, the small funnel
being meanwhile kept covered with a watch-glass. After the light
petroleum has passed through, the funnel is again placed in the neck
of the flask, to the sides of which a portion of the digitoxin will have
adhered, and the contents of the filter, while still moist, again brought
into solution by pouring some hot absolute alcohol upon it. The
alcoholic solution is evaporated, about 5 c.c. of ether added to the
residue, and the ether then removed by heating in a water-bath, when
the varnish-like digitoxin will be partially changed into the crystalline
form. The residue is finally dried in a water-bath and weighed.
Another method is as follows : — The flask with the precipitated
digitoxin is placed in a sharply inclined position, and allowed to remain
undisturbed for some hours, until the flakes have been well deposited,
when the light petroleum is decanted, so far as this may be possible
without loss. The remaining contents of the flask are weighed, and
these evaporated at a gentle heat, which is best effected by blowing a
warm current of air, by means of a hand-bellows, into the flask. Care
should be taken not to place the flask in a hot-water bath, otherwise
the contents will be thrown out with explosive violence. The digitoxin
will remain as a white powder, which can now be weighed, but a
correction of the weight is necessary. If it be assumed that the crude
digitoxin weighed 0-062 g., the purified substance 0-048 g., the decanted
light petroleum 50 g., and the contents of the flask which were
evaporated 10 g., the latter would still have contained 0-0028 g. of
impurities. The purified digitoxin would therefore be calculated as
0-048 — 0-0028=0-0452 g. or 0-452 per cent.
244 DRUGS AND GALENICAL PREPARATIONS
Determination of Extract. — The yield of aqueous extract is deter-
mined by the cold process, as described under Ergot (p. 225).
The following values have been obtained : —
Digitoxin .... 026 to 062 per cent.
Dry, aqueous extract, up to . . 36 per cent.
Menyanthes (Buckbean, Bogbean, Marsh Trefoil).
The leaves oi Menyanthes trifoliata, Linne.
Determination of Extract. — As described in the introduction to
Leaves (p. 239), in the proportion of 10 to 200.
Senna (Alexandrian).
The dried leaflets of Cassia acutifolia, Delile.
Determination of Extract. — In the same manner as with Menj'anthes.
The German PharmacopcKia recognises only the Indian or
Tinnevclly Senna, which consists of the dried leaflets of Cassia
angnstifolia, Vahl, and requires that the powdered leaves should yield
on ignition not more than 12 per cent, of ash.
Strammonium.
The leaves of Datiira Straminottium, Linne, collected at the time of
flowering.
Determination of Extract. — This is conducted as follows, according
to the use of the leaves for the preparation of (i) tincture ; (2) oil ; or (3).
extract.
(i) By extraction with pure alcohol, as described in the introduc-
tion to Flowers (III.) (p. 236).
(2) By extraction with a mixture of 150 g. of 90 per cent, alcohol
and 4 g. of a solution of ammonia (sp. gr. 0-960), in the same manner
as the preceding.
(3) By extraction with either cold or hot water. 10 g. of the sample
are extracted with 100 g. of water ; the extraction with hot water is
carried on for a quarter of an hour in a hot-water bath, the water lost
by evaporation being made good.
The United States Pharmacopoeia directs the assay of strammonium
leaves for alkaloid to be conducted in the same manner as prescribed
for belladonna leaves, and requires that they shall contain not less than
0-25 per cent, of mydriatic alkaloids.
The German Pharmacopoeia requires that powdered strammonium
leaves should yield on ignition not more than 20 per cent, of ash.
Uva Ursi.
The dried leaves oi ArctostapJiylos Uva-Ursi i^xwwC), Sprengel.
RHIZOMES 245
Determinatioti of Extract. — By extraction with cold water, as
indicated under Ergot (p. 225).
By extraction with hot water, as described in the introduction to
Leaves (p. 239), in the proportion of 10 : 200.
By extraction with a mixture of equal parts by weight of 90 per
cent, alcohol and water, as described in the introduction to Flowers
(III.) (p. 236).
VII. RHIZOMES.
The rhizomes are examined in precisely the same manner as the
roots, for which the details are given below (p. 247). The yield of
either aqueous or alcoholic extract is determined as the directions for
making the extract may require. The tests of the Pharmacopoeia are
also to be considered. In the case of calamus rhizome the yield of
alcoholic extract is determined.
Galangal.
The dried rhizome oi Alpmia offidnaruiii, Hance.
Determination of Extract. — By extraction with 68 per cent, alcohol
in the usual manner.
Ginger.
The dried rhizome of Zingiber officinale, Roscoe.
Deterniinatiofi of Extract. — This is conducted either by extracting
with a mixture of i part of 90 per cent, alcohol and 8 parts of water,
or with 6?) or 90 per cent, alcohol.
The German Pharmacopoeia requires that powdered ginger should
yield on ignition not more than 7 per cent, of ash.
Hydrastis (Golden Seal).
The dried rhizome and roots of Hydrastis cattadettsis, Linne.
(a) Deternmiation of Alcoholic Extract. — This is conducted according
to the general method described under Roots (VIII.). The yield
should be not less than 20 per cent. It has been found to vary from
2004 to 28-0 per cent.
(b) Determination of Hydrastine. — The following method is that of
the German Pharmacopoeia: — To 6 g. of hydrastis rhizome in moderately
fine powder, contained in a flask, are added 60 g. of ether, and, after
vigorous shaking, 10 c.c. of a solution of ammonia (sp. gr. 0-960), the
mixture being then allowed to stand for three hours, with frequent
and vigorous shaking. When the liquid has become perfectly clear,
40 g. of the ethereal solution (=4 g. of hydrastis rhizome) are
filtered through a dry, well-covered filter into a flask, and the ether
distilled off. The residue is then gently heated with 10 c.c. of
dilute hydrochloric acid (i part of acid, sp. gr. M26, to 99 parts of
246 DRUGS AND GALENICAL PREPARATIONS
water), and the solution passed through a small filter, previously
moistened with water, into a separator, the flask being washed twice
successively with dilute hydrochloric acid of the above strength, using
5 c.c. each time. These liquids are passed through the same filter into
the separator, the filter being finally washed with a little water. To
the united acid liquids are added 40 c.c. of ether, the mixture being
vigorously shaken, and then sufficient solution of ammonia to impart
an alkaline reaction, after which the mixture is at once shaken
vigorously for two minutes. When it has become perfectly clear, the
aqueous liquid is drawn off, the ethereal liquid remaining in the
separator again shaken, and, when clear, 30 c.c. of it ( = 3 g. of hydrastis
rhizome) are transferred to a light, tared flask. The ether is then
allowed to evaporate at a moderate heat, and the residue dried at 100°
until the weight remains constant. The amount of residue should be
not less than 0-075 g-) corresponding to at least 2-5 per cent, of
hydrastine, C.2iH._,^OyN.
The same percentage of hydrastine is required by the United States
rharmacopceia, when determined by the prescribed method of assay.
Male Fern.
The rhizome of Aspiduim Filix-mas (Linne), Swartz, collected in the
autumn, divested of the roots, leaves, and dead portions, and carefully
dried.
The United States Pharmacopoeia, under the title of Aspidiuvi,
recognises the dried rhizome of Dryopteris Filix-mas (Linne), Schott,
or of D. via)-ginalis (Linne), Asa Gray.
Dctcniiiiiation of Extract. — 10-20 g. of the rhizome, dried and in
moderately fine powder, are extracted in a Soxhlet apparatus for one
and a half to two hours with ether (sp. gr. 0720). The ether is then
evaporated off in a tared flask, and the residue dried and weighed.
Rhubarb.
The dried rhizome of RJicuni palinatuiii, Linne, and R. officijialc^
Baillon.
Determinatio7i of Extract. — Either the yield of aqueous extract is
determined by the cold process, as described under Roots (VII L), or
the extraction may be conducted with dilute alcohol according to the
following method of the German Pharmacopoeia : —
To 5 g. of rhubarb, in fine powder, are added 50 c.c. of a mixture
of equal parts by weight of 90 per cent, alcohol and water, and the
mixture allowed to stand for twenty-four hours, with frequent agitation ;
20 c.c. of the clear, filtered liquid are then evaporated in a tared dish,
and the residue dried at 105° until the weight is constant. The weight
ROOTS 247
should be not less than 07 g., corresponding to at least 35 per cent, of
extract.
The powdered rhubarb should yield on ignition not more than 12
per cent, of ash.
VIII. ROOTS.
The directions, in general, are as follows, according to whether the
yield of aqueous or alcoholic extract is to be determined : —
(a) Aqueous Extract. — To 10 g. of the finely powdered root are
added 100 g. of cold water, and the mixture allowed to stand for
twenty-four hours, with frequent stirring ; the liquid is then passed
through a dry filter, 20 c.c. of the filtrate ( = 2 g. of the root) evaporated
in a tared dish, and the residue dried at 100° until of constant weight.
(b) Alcoholic Extract. — The procedure is the same as in the case of
the aqueous extract, but with the use of a mixture of equal parts of
alcohol and water.
Belladonna.
The dried root of Atropa Bellado7ina, Linne.
Determination of Alkaloid (according to C. C. Keller). — To 12 g.
of dried belladonna root, in the form of powder, and contained in a
flask, are added 90 g. of ether and 30 g. of chloroform, and the
mixture allowed to stand for ten minutes, with frequent shaking.
10 g. of a solution of ammonia (sp. gr. 0-960) are then added, and the
maceration continued for half an hour, the mixture being repeatedly
shaken. Subsequently 15 g. of water are added, the whole shaken
vigorously for a few minutes, or until the powdered drug has agglomer-
ated, and 100 g. of the clear liquid then decanted. This is shaken
three times successively with i per cent, hydrochloric acid, the com-
bined acid liquids made alkaline with ammonia, these extracted with
a mixture of chloroform and ether, the ethereal liquid evaporated in
a tared flask, and the residue weighed. The latter is subsequently
dissolved in a little alcohol, the solution diluted with water, and
titrated with N\\o hydrochloric or sulphuric acid with the use of
haematoxylin as the indicator. i c.c. of iV/io acid = 00289 g.
of atropine.
The yield of alkaloid should be not less than 0-5 per cent. {cf.
also the method of assay described under belladonna leaves, Section
VI., p. 240).
The following variations in yield have been found : —
Aqueous extract . . . 20-0 to 23'33 per cent.
Alkaloid .... 0-63 „ 070 „
The United States Pharmacopoeia requires that belladonna root
should yield not less than 0-45 per cent, of mydriatic alkaloids, when
assayed by the method prescribed for belladonna leaves.
248 DRL'GS AND GALENICAL PREPARATIONS
Gentian.
The dried rhizome and roots of Gcntiana /utea, Linne, or of other
species of Gctitiana, of which the German Pharmacopoeia specifies
G. pa7inonica,^ZQ'^o\\\ G. purpurea, \S\x\Xik.; and G. punctata, \J\x\x\(t.
Deten)ii7iation of Extract. — For the preparation of extract the root
is treated as described for Frangula bark, under (L) (p. 235); for a
Hquid extract it is extracted with a mixture of equal parts of alcohol
and water ; and for a tincture with 68 per cent, alcohol.
Ipecacuanha.
The dried root of Uragoga ipecacuanha (Willdenow), Baillon.
(a) Deterviination of Extract. — For the preparation of a liquid
extract the root is extracted with 90 per cent, alcohol, for a tincture
with 68 per cent, alcohol, and for the preparation of the syrup with a
mixture of i part of alcohol and 8 parts of water,
(b) Dctermijiation of Alkaloid. — The following method is that of
the German Pharmacopoeia. To 12 g. of finely powdered ipecacuanha,
contained in a flask, are added 90 g. of ether and 30 g, of chloroform,
and, after vigorous shaking, 5 g. of a solution of sodium carbonate (i : 2)
and 5 g. of water, the mixture being then allowed to stand for three
hours, with frequent vigorous shaking. When it has become perfectly
clear, 60 g. of the chloroform-ether mixture ( = 6 g. of ipecacuanha) are
passed through a dry, well-covered filter into a flask, and the liquid
distilled off. The residue is heated with 10 c.c, of dilute hydrochloric
acid (i part of acid, sp. gr. 1-126, to 99 parts of water), the solution
passed through a small filter, previously moistened with water, into
a separator (I.), the extraction of the residue being then repeated
with two successive portions of the same dilute acid as above, using
5 c.c. each time, these liquids passed through the same filter, and the
flask and filter finally washed well with water. To the united acid
liquids are added 5 c.c. of chloroform, then a solution of sodium
carbonate until the reaction is alkaline, and the mixture at once
shaken vigorously for two minutes. When perfectly clear, the chloro-
form solution is run into another separator (IL), and the extraction
repeated three times in the same manner with chloroform, using 5 c.c.
each time. To the united chloroform solutions are added 10 c.c. of
A710 hydrochloric acid, and so much ether that the chloroform-ether
mixture floats on the surface of the acid liquid, after which the whole
is vigorously shaken for two minutes. When perfectly clear, the acid
liquid is passed through a small filter, previously moistened with water,
into a flask of 100 c.c. capacity, the chloroform-ether mixture then
shaken three times successively for two minutes with water, using
10 C.C. each time, these liquids also passed through the same filter,
ROOTS 249
which is finally washed with water, and the entire liquid diluted with
water to lOO c.c. 50 c.c. of this solution ( = 3 g. of ipecacuanha) are
transferred to a flask, about 50 c.c. of water added, together with a
freshly prepared solution of a fragment of haematoxylin in i c.c. of
alcohol, and so much Njio potassium hydroxide solution run into
the liquid, with agitation, that the mixture assumes a deep yellow
colour, which, by vigorous agitation, quickly passes into bluish-violet.
For this purpose not more than 2-6 c.c. of Njio potassium hydroxide
solution should be required, so that at least 24 c.c. of N/io hydrochloric
acid are used up for neutralising the alkaloids present. This would
correspond to a minimum of 1-99 per cent, of alkaloids (i c.c. Ayio
hydrochloric acid =0-02482 g. of alkaloids, calculated as emetine,
C30H44O4N2, with haematoxylin as the indicator).
The amount of alkaloid has been found to vary from 0-97 to
3-20 per cent.
The United States Pharmacopoeia requires that ipecacuanha shall
yield not less than 1-75 per cent, of alkaloids, when assayed according
to the prescribed method.
Liquorice (Russian).
The dried root of Glycyrrhiza glandtilifera, Waldstein and Kitaibel.
Determination of Extract. — If the liquorice is to be used for the
preparation of an extract or syrup, the yield of extract is determined
by the aid of heat in the following manner : —
To 10 g. of finely cut or coarsely powdered liquorice root, contained
in an enamelled vessel which is best weighed with a stirring rod, are
added 300 g. of cold water, and the whole allowed to stand for an hour
at the ordinary temperature, with frequent stirring. It is then slowly
heated to boiling, with frequent stirring, and evaporated to about
210 g. After standing overnight, the evaporated water is replaced,
the mixture again stirred vigorously, and the whole brought upon a
dry filter ; 20 c.c. of the clear filtrate (=1 g. of root) are then evaporated
in a tared porcelain dish and the residue dried until of constant weight.
The yield of extract by the cold process can be determined by
extracting with a mixture of 99 g. of cold water and i g. of a solution
of ammonia (sp. gr. 0-960) in a closed vessel. For the purpose of
preparing an alcoholic extract or syrup, the root is extracted with
100 c.c. of a mixture of 49 g. of 90 per cent, alcohol, 48 g. of water, and
3 g. of solution of ammonia (sp. gr. 0-960).
Rhatany.
The dried root of Kravieria triandra, Ruiz and Pavon (Peruvian
Rhatany), and of K. argentea, Martius (Para or Brazilian Rhatany).
250 DRUGS AND GALENICAL PREPARATIONS
In addition to these two sorts the United States Pharmacopoeia also
recognises Savaniila Rhatan)', from K. Ixina, Linne.
Dcterviiuation of Extract. — The yield of aqueous extract is
determined by the cold process, as described under Ergot (p. 225).
Senega.
The dried rhizome and roots oi Polygala Senega, Linn(^.
Dcteri)iinatio7i of Extract. — This is conducted as follows, according
to the use of the roots for the preparation of (i) syrup ; (2) solid extract ;
(3) liquid extract ; or (4) permanent extract (" Daucrextrakt," Dieterich).
(i) B}' extraction with a mixture of i part of 90 per cent, alcohol
and 3 parts of water.
(2) By extraction with a mixture of 2 parts of 90 per cent,
alcohol and 3 parts of water.
(3) By extraction with a mixture of 2 parts of 90 per cent,
alcohol and i part of water.
(4) By extraction with either cold or hot water. The extraction
with hot water is carried on for a quarter of an hour in a hot-
water bath.
Valerian.
The dried rhizome and roots of Valeriana officinalis, Linne.
Determination of Extract. — This is conducted in the usual manner
with a mixture of equal parts of alcohol and water.
IX. SEEDS.
Kola Seeds. Kola Nuts.
The seeds of Cola vera, Schumann, or of Cola acuminata, Schott
and Endlichcr.
The following methods of examination have been given by
K. Dieterich: —
(a) Determination of Total Alkaloid. — 10 g. of the finely rasped
drug, which has been uniformly moistened with water, are mixed with
10 g. of granular, unslaked lime, and the mixture placed in an extraction
thimble. This is then extracted with chloroform in a Soxhlet apparatus
for three-quarters of an hour, or only so long as the chloroform runs off
clear, then washed with chloroform, and the solution evaporated in a
dish to approximate dryness. The residue thus obtained is taken up
with 20 c.c. of iV/i hydrochloric acid, by the aid of a very gentle heat,
and the solution filtered into a separator of 100 c.c. capacity, the dish
and filter being carefully washed, and the washings added to the acid
liquid. The contents of the separator are made strongly alkaline with
ammonia, allowed to stand for a quarter of an hour, with frequent
shaking, and then extracted with three successive portions of chloroform,
using 20 c.c. each time. The united chloroform solutions are finally
SEEDS 251
evaporated in an Erlenmeyer flask or in a crystallising basin, in the
latter case placing the basin in a dish of hot water but not in a
steam-bath, in order to prevent loss by the creeping of the liquid, and
the caffeine, which is now quite white, dried until the weight is
constant. The weight obtained, multiplied by lo, gives the percentage
of total alkaloid.
(b) Free aiid combined Alkaloid and Fat. — lo g. of the finely rasped,
dry drug are mixed, without previously being moistened, with lo g. of
coarse, purified sand, and extracted for two hours in a Soxhlet apparatus
with chloroform. The resulting solution is evaporated, the residue
dried until of constant weight, and the total weight of fat and free
caffeine determined. This mixture is extracted with boiling water, the
solution filtered, and the filter carefully washed. The aqueous solution
is evaporated, and the crude caffeine, for the purpose of its purification,
taken up with 20 c.c. oi N\\ h}'drochloric acid, as in the determination
of total alkaloid. The acid solution is filtered, made alkaline with
ammonia, and, after standing for a quarter of an hour, extracted three
times successively with chloroform. The united chloroform liquids are
then evaporated, and the residue dried until the weight is constant.
This weight, multiplied by 10, gives the percentage of free caffeine.
By subtracting the amount of the latter from that of the caffeine arid
fat, as determined above, the amount of fat present is ascertained. The
difference between the amount of free caffeine and that of the total
alkaloid represents the combined caffeine.
(c) Determination of Moisture. — 5 g. of the finely rasped drug are
dried in a platinum dish at 100° until the weight is constant.
(d) Determination of Ash. — The 5 g. of drug which had been used for
the determination of moisture are ignited until, after cooling in a
desiccator, the weight remains constant.
(e) Test for Identity. — 20 g. of the drug are mixed with 10 g. of
calcined magnesia, the mixture moistened with dilute alcohol, and then
extracted with 100 g. of the latter by digestion at a gentle heat, which
is best effected by allowing the mixture to stand in a warm room for
twelve hours. The liquid is then expres.sed, filtered, and the filtrate
transferred to a white glass vessel, the width of which is at least 10 cm.
In a layer of this depth the liquid will show a bluish-green fluorescence,
resembling that of curcuma tincture. This reaction is only given by
unroasted kola powder.
The following are the minimum and maximum values obtained : —
Total Alkaloid . . . i-o to 2-0 per cent.
Free Alkaloid .
Combined Alkaloid
Fat
Moisture
Ash
o-io6 „ 0778
0788 „ 1-282
0324 „ 1-298
9-49 ,, 13-57
279 » 5-46
252 DRUGS AND GALENICAL PREPARATIONS
Requirements. — The extreme limits should be within the above
figures, and the drug should contain the largest possible amount of
alkaloid, but not less than i per cent., with a preponderating amount
of combined alkaloid.
It may be noted that, according to Gadamer, the caffeine is present
in only a very loose form of combination, and that, both in the free and
combined form, it is probably first produced in the process of dr}-ing.
The much shorter method of examination of C. C. Keller or that of
Siedler,^ with the use of ammoniacal chloroform, does not give so pure
a caffeine, but suffices for a crude analysis.
Black Mustard Seed.
The ripe seed of Brassica tiigra (Linne), Koch.
Detennination of the Essential Oil. — The following method is that
of the German Pharmacopoeia : — To 5 g. of powdered mustard seed,
contained in a flask, are added 100 c.c. of water at 20 -25^ The
corked flask is then allowed to stand for two hours, with repeated
agitation, 20 c.c. of alcohol and 2 c.c. of olive oil are added, and the
mixture distilled with careful condensation. The first 40-50 c.c.
which pass over are collected in a flask of 100 c.c. capacity which
contains 10 c.c. of a solution of ammonia (sp. gr. 0-960), and 20 c.c. of
Njio silver nitrate solution are added. A small funnel is then placed in
the flask, and the mixture heated for an hour in a water-bath ; after
cooling, it is diluted with water to 100 c.c. To 50 c.c. of the clear
filtrate are added 6 c.c. of nitric acid and i c.c. of ferric ammonium
sulphate solution (i part of ferric ammonium sulphate to be dissolved
as required in a mixture of 8 parts of water and i part of dilute
sulphuric acid of sp. gr. M09-M 14) ; not more than 6-5 c.c. of A710
ammonium thiocyanate solution should then be required to produce a
red coloration, which would correspond to at least 0-7 per cent, of all\l
mustard oil (i c.c. of A710 silver nitrate solution = 0004956 g. of allyl
mustard oil, with ferric ammonium sulphate as the indicator).
i^.— GALENICAL PREPARATIONS.
Since the manufacture of galenical preparations has become a
branch of industry on a large scale, and is no longer restricted to the
pharmacy, methods for their examination have been worked out.
This has been rendered necessary by the fact that, as shown in the
preceding Section, " Resins, Balsams, and Gum-Resins," the crude
materials and drugs used for this purpose are not only subject to great
variations, but also occur in commerce of such poor quality that the
galenical preparations made from them must naturally be inferior
in character. Although the methods for the examination of galenical
1 Ber. d. deutsch. pharm. G(S., 1898, p. 18.
GALENICAL PREPARATIONS 253
preparations, such as tinctures and extracts, cannot be regarded as
final, they, nevertheless, permit of forming an opinion which is to
some extent useful respecting their quality and that of the drugs
from which they were made. The methods employed depend
upon the observation of such physical characters as transparency,
colour, odour, taste, specific gravity, and, when practicable, the
quantitative determination of some essential constituent. Such methods
of examination have now been incorporated to a large extent in the
German Pharmacopoeia, whereas the British and United States
Pharmacopoeias do not as yet describe the physical characters of
galenical preparations, and requirements respecting the control of
quality or strength are restricted to those preparations of special
potency whose active constituents permit of being quantitatively
determined.
The following data comprise some of the special methods of
examination : —
Papers.
Test Papers.
{A'ccordlng to E. Dieterick.)
Sensitiveness. — Ten different strengths of dilute sulphuric acid are
prepared, which should contain i part of SO3 in 1000, 5000, 10,000,
20,000, 30,000, 40,000, 50,000, 60,000, 80,000, and 100,000 parts of
water respectively, and also ten dilute solutions of ammonia which
shall contain NH3 in the same proportions. The test papers prepared
from filter paper are then examined for their sensitiveness by dipping
a strip of the paper once in the solutions of sulphuric acid or ammonia,
in the order of strength indicated above, and observing with which
solution a change of colour takes place.
The test papers prepared from writing paper are examined by
placing on them a drop of the above solutions.
The papers should respond to the following limits of sensitiveness : —
Congo Red Paper . . i : 5000 to i : 10,000 SO3
Curcuma Paper . . . i : 5000 „ i : 10,000 NH3
Blue Litmus Paper . . i : 10,000 „ i : 40,000 SO3
Red Litmus Paper . . I : 10,000 „ i : 30,000 NH3.
Mustard Paper and Mustard Lint.
{According to K. Dieterich and the German Pharmacopcsta.)
(a) Amount of Mustard Flour. — This is determined by carefully
scraping the mustard with a knife from 100 sq. cm. and weighing it.
(b) Determination of Mustard Oil} — 100 sq. cm. of the mustard
1 Cf, the determination of essential oil in black mustard seed, under Drugs. Also
the determination of mustard oil in mustard flour, by C. Brioux, Ann. Cliim. analyi., 191 2, 17, 3 ;
J. Soc. C/iem. Ind., 1912, 31, 148 ; and Greenish and Bartlett, Pharm.J., 1912, 88, 203.
254 DRUGS AND GALENICAL PREPARATIONS
paper, cut in strips, arc placed in a flask, and 50 c.c. of water at 20°-25"'
added. The flask is then corked, allowed to stand for two hours with
repeated agitation, 10 c.c. of alcohol and 2 c.c, of olive oil added, and
the mixture distilled with careful condensation. The first 30 c.c. which
pass over arc collected in a flask of 100 c.c. capacity which contains
10 c.c. of a solution of ammonia (sp. gr. 0-960), and 10 c c. of A' 10 silver
nitrate solution are added. A small funnel is then placed in the flask, and
the mixture heated for an hour in the water-bath, when, after cooling,
it is diluted with water to 100 c.c. To 50 c.c. of the clear filtrate are
added 6 c.c. of nitric acid and i c c. of ferric ammonium sulphate
solution; not more than 3-8 c.c. of A710 ammonium thiocyanate
solution should then be required to produce a red coloration, which
would correspond to at least 001 19 g. of allyl mustard oil in 100 sq. cm.
(i c.c. of A710 silver nitrate solution = 0-004956 g. of allyl mustard oil,
with ferric ammonium sulphate as the indicator).
The mustard paper and mustard lint should conform to the
following limits : —
I. Coarse Flour.
Coarse Mustard Flour to 100 sq. cm., 2-oi6-4-55i g.
Mustard oil, calculated on the flour, 0-89- 1-57 per cent.
I I. Fine Flour.
Fine Mustard Flour to 100 sq. cm., 1-50-2-991 g.
Mustard oil, calculated on the flour, 0-80-1-44 per cent.
III. Mustard Lint.
Mustard Flour to 100 sq. cm., 2-1-2-711 g.
Mustard oil, calculated on the flour, i-ii-i-2i per cent.
The British Pharmacopoeia directs that CJiarta Sitiapis (Mustard
Plaster) should be prepared by spreading a mixture of 5 g. of equal
parts of black and white mustard seed, deprived of fixed oil, with a
sufficient quantity of solution of india-rubber, over about 2 sq. dm. of
cartridge paper, whilst the United States Pharmacopoeia requires of
Mustard Paper that a surface of 60 sq. cm. should contain about 4 g. of
black mustard, deprived of fatty oil.
Plasters.
Plasters having a rubber basis, which* are now most largely used in
medical practice, should be examined first of all for the amount of
caoutchouc they contain.
A method for the determination of caoutchouc has been worked out
by K. Dieterich.^
' " Ueber die quantitative Bestimmung von Kautschuk in Kautschuk-Pflasterii," P/uirm.
Zeit,^ 1903, No. 78, and the Helfenberger .AnnaUn^ KJ03.
LIQUID OR FLUID EXTRACTS 255
The general method for the examination of plasters consists in the
determination of the water. This is effected by heating i g. of the
respective plaster, contained in a tared, shallow, porcelain dish, in a
drying oven at loo^, until the weight remains constant.
The determination of glycerin, which is sometimes carried out, is
very uncertain ; a reliable method is required before any conclusions
can be drawn as to the amount of glycerin present.
Liquid or Fluid Extracts.
According to the general method of examination the following
points are to be considered : —
(a") Tests for Identity. — See the Helfenbei'ger Aimalen, 1891, pp. 50-80.
(b) Specific Gravity at 15°.
(c) Dry Residue at [00°. — 5 g. of the liquid extract are evaporated
in a previously ignited and weighed platinum dish, and the residue
dried at 100° until the weight is constant.
(d) AsJi. — The dry residue is ignited.
(e) Exaniinatio7t according to the Pharmacopoeia. — The number of
liquid extracts adopted .by the national pharmacopoeias not only
varies considerably, but in many cases there are also important
differences with respect to their method of preparation, or in the
nature of the solvent employed for the extraction of the drug. In
accordance with these facts preparations bearing the same name
may differ appreciably in character, and in the examination of such
products consideration must therefore be taken of the requirements of
the particular pharmacopoeia to which they are expected to conform.
These differences are, moreover, by no means constant, since changes
in the method of preparation or in strength are frequently made in
successive revisions of a pharmacopoeia. The British Pharmacopoeia
directs the following liquid extracts to be assayed for the proportion
of their active constituents : — Belladonna root, cinchona, ipecacuanha,
nux vomica, and opium. In the United States Pharmacopoeia
such requirements are extended to the following fluid extracts: —
Aconite, belladonna root, cinchona, coca, colchicum seed, conium,
guarana, hydrastis, hyoscyamus, ipecacuanha, nux vomica, pilocarpus,
scopola, and strammonium.
A special method is given for the following unofficial preparation : —
Liquid Extract of Kola.
(From unroasted nuts, according to K. Dieterich.)
(a) Determinatio?t of Total Alkaloid. — 20 g. of the liquid extract are
evaporated to a syrupy consistency, or until all the alcohol has been
removed, and the residue then treated as described under Kola Nuts
256 DRUGS AND GALENICAL PREPARATIONS
(Section IX., Seeds, p. 250). The weight of total alkaloid, multiplied by
5, expresses the percentage.
(b) Free and CoDibined Alkaloid. — 20 g. of the liquid extract are
evaporated to a syrupy consistency, or until all the alcohol has been
removed, and the residue treated as described under Kola Nuts (/;)
(p. 251). By multiplying with 5 the percentage of free caffeine is
obtained, and by subtracting the latter from the total alkaloid the
percentage of combined caffeine is indicated.
The purification of the caffeine can only be effected by means of
acid, since many liquid extracts contain glycerin, from which the
caffeine cannot be separated by either water or alcohol.
(c) Ash
(d) Specific Gravity \ According to the usual methods.
(e) Residue, dried at 100
(f) Identification. — The identification of liquid extract of kola may
be effected either with the alkaloidal residue obtained, or with the
extract itself. In the first case the identification depends upon the
purple coloration which caffeine gives with chlorine water and
ammonia (the so-called murexide reaction), or, if the extract be used,
20 g. of the liquid are evaporated, the residue triturated with a solution
of ammonia, and then shaken with ether. On evaporating the ethereal
liquid, a residue will be obtained which, although impure, yields a purple
colour with the above reagents.
The figures obtained for the extract should be within the following
limits, which will indicate that it has been prepared from the more active
unroasted kola nuts : —
Total Caffeine
Free Caflfeine
Combined Caffeine
Dry Residue
Ash .....
Specific Gravity at 15°
Thick Extracts and Dry Extracts.
In addition to the liquid or fluid extracts the German Pharmacopoeia
recognises the following three forms of an extract : —
I. T/iin Extracts, which have a degree of fluidity resembling that
of fresh honey ; 2. Thick Extracts, which, when cold, do not permit of
being poured ; and 3. Dry Extracts, which are such as can be powdered.
In other pharmacopoeias their characters are designated as "soft,"
" firm," " in powder," of a " pilular consistence," etc.
The general method for the examination of the above-mentioned
extracts is, according to E. Dieterich, as follows : —
(a) Reactions for Identity.
0-95 to
1-5 per cent
O-IIO „
o-8io „
. 0-03 „
I-OI9
. I4-0 „
I7-0
I -04 „
1-42 „
. 0-974 „
0-976.
TINCTURES. OINTMENTS 257
(b) Loss on djyijig at ioo°. — 2 g. of the extract are dried at ioo°
in an ignited and weighed platinum dish until the weight is constant.
(c) Ash. — The dried extract is incinerated.
(d) Examination according to the Pharmacopoeia. — The remarks con-
cerning the variations in liquid or fluid extracts are equally applicable
to the so-called solid extracts. Among those recognised by the British
Pharmacopoeia the following are directed to be assayed for the pro-
portion of active constituent : — Belladonna root, nux vomica, and opium.
The United States Pharmacopoeia extends these requirements respect-
ing strength to the following extracts : — Belladonna leaves, colchicum
corm, hyoscyamus, nux vomica, opium, physostigma, scopola, and
strammonium.
Tinctures.
The class of galenical preparations known as " Tinctures " exhibits
not only great variation with respect to the number adopted by the
different national pharmacopoeias, but also with regard to their mode
of preparation and strength. No general standards can therefore be
adopted for them, such as those of specific gravity and the amount of
dry residue which they 5'ield on evaporation, and the more specific
requirements must naturally be in conformity with those of the
respective pharmacopoeias. The British Pharmacopoeia directs the
tinctures of belladonna, nux vomica, and opium to be assayed for
alkaloid, and the tincture of jalap is required to contain a definite
amount of resin ; whereas the United States Pharmacopoeia extends
these more precise requirements to the tinctures of aconite, belladonna,
colchicum seed, hydrastis, hyoscyamus, nux vomica, opium, physostigma,
and strammonium.
Ointments.
The British and United States Pharmacopoeias restrict their require-
ments concerning ointments and cerates to the prescribed methods of
preparation and strength. The only exception is the more precise
requirements of the latter work for the following preparation : —
Mercurial Ointment.
The United States Pharmacopoeia directs that the amount of
mercury contained in this preparation shall be determined by the
following method:^ — Weigh lo g. of mercurial ointment in a tared dish,
melt it, then remove it from the flame and add 50 c.c. of warm petroleum
spirit. Stir the mixture well, allow the mercury to settle completely,
and decant the petroleum spirit. Wash the residue with successive
portions of 10 c.c. each of warm petroleum spirit until it is entirely free
1 For the volumetric determination of mercury in miercurial preparations see Crewe,
Pharm./., 1908, 81, 359 ; and Cowie, ibid., 1911, 87, 885.
Ill R
258 DRUGS AND GALENICAL PREPARATIONS
from fatty matter, carefully retain all the separated mercury in the dish,
and allow all traces of the petroleum spirit to evaporate. Add to the
residue lo c.c. of dilute hydrochloric acid (lo per cent.), heat gently,
and stir with a glass rod until the mercury collects in a globule. Pour
off the acid, warm the mercury with a little distilled water, dry the
globule on filter paper, and weigh. The mercury should weigh not less
than 4-9 g.
The corresponding preparation of the British Pharmacopcuia
{^Ungiicntuvi Hydrargyri) contains about 48-5 per cent, of mercur}-, while
that of the German Pharmacopoeia {Ungucntiini Hydrarg}'ri cincrcu))i)
contains 30 per cent, of mercury.
Literature.
British Phannacopccia, 1898.
British Pharmaceutical Codex, 191 1.
Deutsches Arzneibuch, 5th edition, 1910.
Dispensatory of the United States of America, latest edition.
Greenish, H. G. — Materia Medica, 1909.
Greenish, H. G. — The Microscopical Examination of Foods and Drugs, 19 10.
The National Standard Dispensatory, latest edition.
United States Pharmacopceia, 8th revision, 1900, published 1905.
ESSENTIAL OILS
By E. GiLDEMElSTER, Ph.D., Leipzig. English translation revised by
Frederick B. Power, Ph.D., LL.D., Director of the Wellcome Chemical
Research Laboratories, London.
The 'examination of essential oils for the purpose of detecting
adulterations is conducted partly by physical and partly by chemical
methods.
In the first place, by determining the physical properties it is
ascertained whether the oil under examination is a normal one. That
is the case if all the constants are within the limits adopted for pure
oils. The chemical examination, as a rule, affords information regarding
the quality of the oil, and_ by this means the nature and amount of any
adulterant present may also be found.
The physical tests comprise the determination of the specific gravity,
optical rotatory power, and solubility in alcohol of different strengths,
sometimes also the congealing point, boiling point, and amount of
residue left on evaporation. The usual adulterants, such as alcohol,
fatty oil, petroleum, oil of turpentine, cedar-wood oil, etc., almost always
affect one or more of the physical constants, and may thus be detected.
For example, oil of turpentine when added to oil of sweet orange
diminishes its rotatory power, while the presence of cedar-wood oil in
oil of lavender renders the latter insoluble in 70 per cent, alcohol. The
adulteration of any essential oil with alcohol causes a decrease in
specific gravity, while the addition of petroleum to the oil of star-anise
lowers its congealing point and influences its solubility in 90 per cent,
alcohol.
The chemical examination of an essential oil is closely connected with
its physical tests. If a definite adulteration is suspected, an attempt should
be made to isolate the adulterant and to identify it. Even when an oil
has been found to be normal, a determination of its quality is frequently
desirable, but among the methods subsequently to be described the one
to be employed would depend upon the composition of the respective
oil. The chief constituents of some oils, and those which determine its
value, are alcohols, while in other cases they are esters, aldehydes,
phenols or ketones, and by their quantitative determination information
is not only obtained with regard to the normal or abnormal character
of the oil, but also respecting its quality. Thus, of two unadulterated
259
260 ESSENTIAL OILS
lavender oils, that would be considered the better which contains the
larger percentage of esters. Cassia oil is valued according to its con-
tent of cinnamic aldehyde, caraway oil according to the amount of
ketone it contains, and clove oil according to the amount of its
phenolic constituent.
Determination of the Physical Constants.
Specific Gravity. — When a sufficient quantity of material is avail-
able, the specific gravity is most conveniently determined by means of
the hydrostatic balance of Mohr or Westphal. If the amount of oil is
not sufficient for this method, a pyknometer may be used, the tempera-
ture being maintained at 15".
Optical Rotatory Power. — The rotatory power of essential oils can
be determined in an)- polarising apparatus which is adapted for sodium
light ; the half-shadow apparatus of Laurent is especially to be recom-
mended. In the case of dark oils, short observation tubes having a
length of 50 and 20 mm. may be used, in order to avoid dilution with a
solvent. The angle of rotation, which is directly observed in a 100
mm. tube, is designated as «, and the specific rotatory power ^ as [a]i„
which is calculated according to the formula [a]^ = _ii- In this
formula / denotes the length of the tube in millimetres, and d the
specific gravity of the liquid. In general, it is not necessary to maintain
a definite temperature, but with some oils, such as those of lemon and
sweet orange, the determination is conducted at 20°.
Solubility. — For the customary determination of the solubility of
essential oils, alcohol of 70, 80, and 90 per cent, by volume is chiefly
employed. To i c.c. of the oil, in a small graduated cylinder, alcohol of
a definite strength is added, drop by drop, until solution is effected. In
most cases the liquid will remain clear when further amounts of the
solvent are added, but sometimes an opalescent turbidity will subse-
quently appear, even with pure oils. If the oil under examination
contains petroleum, this will separate on the surface of the liquid in
drops after standing for a time, whereas fatty oil will collect at the
bottom of the vessel. Cedar-wood oil, copaiba oil, and gurjun oil, as
well as oil of turpentine, are quite sparingly soluble in alcohol, and are
indicated by this property when they have been added with a fraudulent
purpose to other more readily soluble oils.
Congealing Point. — The apparatus employed in the laboratory of
Schimmel & Co.- for determining the congealing point of essential oils,
' Cf. H. Landolt, Das optische Dre/iungsvermogen organischer Substanzeit, 2nd Edition, 1898.
English translation by J. H. Long, The Optical Rotating Power 0/ Organic Substances and its
Practical Applications, 1902.
'^ Semi-annual Report of Schimmel & Co., October i8y8, p. 43.
PHYSICAL CONSTANTS
261
such as those of anise, star-anise, and fennel, is adapted from tlie well-
known apparatus of Beckmann for determining molecular weights by
the depression of the freezing point, and has the form represented
in Fig. 46.
The battery jar A serves as a receptacle for the cooling liquid or
freezing mixture. The glass tube B suspended from the metal cover
forms an air-jacket around the freezing tube C, and prevents the pre-
mature solidification of the oil to be tested. The freezing tube C is
wider at the top, and becomes narrower at the place where it rests on
the rim of the tube B. In order to retain C in a fixed position, three
glass supports are fastened on the inside of the
tube B, about 5 cm. below its upper edge. The
thermometer, which is graduated in h degrees,
is securely held by three springs in a metal disc,
which permit of sliding it up or down.
To carry out a determination with anise or
star-anise oil the battery jar is filled with cold
water and pieces of ice, but for fennel oil a
freezing mixture prepared from ice and salt is
used. So much of the oil to be examined is
then brought into the freezing tube as to have
a height of about 5 cm., and the thermometer is
immersed in the liquid without allowing it to
touch the sides of the glass at any point.
During the process of cooling, the super-cooled
oil is protected from any disturbance which
would cause its premature solidification. If the
temperature has sunk to about 5° below the
congealing point, that is, with anise oil to 12°^
with star-anise oil to 10°, and with fennel oil
to 3°, crystallisation is induced by rubbing or
scratching the sides of the glass with the ther-
mometer. If this procedure is not successful, a
small crystal of the congealed oil or a little solid anethol is brought
into the liquid, when solidification will ensue with a considerable
development of heat. The solidification may be accelerated by con-
stant stirring with the thermometer, when the temperature will rise
rapidly, and finally attain a maximum, which is termed the "congealing
point " of the oil.
If such an apparatus as the above is not available, the determination
can be conducted in an ordinary flask, which is cooled by placing it in
a freezing mixture, provided the amount of oil is not too small, that
is, not less than 100 g.
Fractional Distillation. — Fractional distillation is employed when it
Fio. 46.
2G2
ESSENTIAL OILS
is a question of isolating a definite constituent of an oil or of separating
individual portions from each other. For a scientific examination it
is necessary to subject the oil to repeated fractional distillation, with
the aid of a fractionating column, in order to separate the constituents
of different boiling point, and even then the separation is sometimes
Lvery incomplete. In testing for
adulterants, fractional distillation
will frequently effect the isolation
of the adulterating agent, such as
alcohol, petroleum, oil of turpentine,
and other liquids. Lemon oil, rose-
mary oil, and oil of spike are tested
for turpentine oil b}' distilling over
lo or 50 per cent, of the respective
oil, and determining the rotatory
power of the distillate. In order
to obtain concordant results by this
method, distillation flasks of uniform
size must be used, and the fractiona-
tion so conducted that the distillate
passes over drop by drop.
The Ladenburg fractionating
flask, which is used in the labora-
tory of Schimmel & Co.^ for testing
the three above-mentioned oils, has
the shape and size indicated in Fig. 47.
The statements regarding boiling point in this Section refer to
determinations in which the mercurial column of the thermometer
is entirely in the vapour of the liquid.
Fio. 47.
Chemical Methods of Examination.
Determination of the amount of Esters by Saponification.
The esters of the alcohols C^^IIiviO and CjyHooO, on account of
their pleasant odour, represent some of the most valuable constituents
of essential oils. Linalyl acetate is the chief odorous component
of the oils of bergamot, petit-grain, and lavender ; bornyl acetate
imparts to the pine-needle oils their characteristic aroma; menthyl
acetate occurs in peppermint oil, and other examples might be given.
All these esters are readily saponified by an alcoholic solution of
potassium hydroxide, and may thus be determined quantitatively,
in fact, in the same manner as is customary in the analssis of fats.
These methods of examination include the determination of the acid
^ Semi-annual Report of Schimmel & Co., October 1898, p. 41.
CHEMICAL EXAMINATION 263
value (A. v.), ester value (E.V.), and saponification value (S.V.). The
acid value expresses how many milligrams of potassium hydroxide
are necessary for neutralising the free acid contained in i g. of oil.
The ester value denotes the number of milligrams of potassium
hydroxide required to saponify the esters contained in i g. of oil.
The saponification value designates the sum of the acid and ester
values. Since the essential oils usually contain but very little free acid,
this determination can generally be neglected.
The saponification is conducted in a small, wide-necked flask of
potash glass, having a capacity of loo cc. A glass tube, about i m. in
length, which is inserted in a perforated stopper, will serve as a reflux
condenser. In such a flask about 2 g. of the oil are weighed accurately
to I eg. and 10-20 cc. of A72 alcoholic solution of potassium hydroxide
added ; in most cases 10 cc. of NJ2 potassium hydroxide solution are
sufficient, but with some oils having a high ester content, such as
Roman chamomile and wintergreen oils, 30 cc must be used. The
oil should, however, first be tested for free acid, after the addition of a
little alcoholic solution of phenolphthalein. The flask, with the
attached condenser, is then heated on a steam-bath for half an hour to
one hour, after which th'e cooled contents of the flask are diluted with
about 50 cc of water, and the excess of alkali titrated with 7V/2
sulphuric acid. In order to saponify menthyl and bornyl w^^valerates
completely, they must be boiled for two to three hours with a consider-
able excess of alkali.
In order to calculate from the saponification value found the amount
of linalyl, geranyl, or bornyl acetate (QoHi^O.COCHg.molec wt.= 196)
contained in an oil, the following equation is employed : —
196XS.V. , r ,
— — = percentage 01 ester.
In the case of acetic esters of alcohols such as menthol, citronellol,
etc. (C^oHjgO. COCH3. molec wt. = 198), the percentage of esters is
, , ,, ^. 198 X S.V.
expressed by the equation : -^ — .
In order to ascertain the amount of alcohols of the formulae
C10H13O (molec wt. = 154), C10H20O (molec wt. = 156), and C^gHg^O
(molec wt. = 220) respectively, the following equations are used : —
1 54 X S.V. 1 56 X S.V. , 220 X S.V.
^ ) — — ^ , and 2 .
560 560 560
Determination of the amount of free Alcohols by Acetylation.
The alcohols of the formulae CjoHigO, CjoHgoO, and CigH.^^O
respectively, which occur as esters in essential oils, are also frequently met
with in the free state ; for example, borneol, geraniol, terpineol, linalool,
264
ESSENTIAL OILS
thujyl alcohol, menthol, citronellol, and santalol. For their quantitative
determination advantage is taken of their property of becoming converted
into acetic esters by heating with acetic anhydride, in accordance with
the equation : —
CioHisO + (CH3CO),0 = CioHi,O.COCH3+CH3CO,H.
This change only takes place quantitatively in the case of borneol,
geraniol, menthol, citronellol, and santalol. Linalool
and terpineol, on the other hand, become partially
decomposed on heating with acetic anhydride, with
the elimination of water. For the purpose of a
quantitative acetylation,' lo c.c. of the oil, together
with an equal volume of acetic anhydride and about
2 g. of anhydrous sodium acetate, are brought into a
small flask provided with a ground-glass condensing
tube (Fig. 48), and the mixture maintained in a uniform
state of ebullition for one hour. After cooling, some
water is added to the contents of the flask, which is
then heated for a quarter of an hour on a water-bath
in order to decompose the excess of acetic anhydride.
By means of a separating funnel, the aqueous, acid liquid
is subsequently drawn off from the oil, and the latter
washed with water, or preferably with a solution of
common salt, until the washings are neutral.
After having been dried with anhydrous sodium
sulphate, 2 g. of the acetylated oil are saponified according to the
method described above (p. 263). From the ester value thus found,
the corresponding amount of the alcohol contained in the original
oil is calculated, according to the following equations : —
«x 15-4
Fio. 48.
1. Percentage of alcohol CjoH^gO in the original oil =
2. Percentage of alcohol Ci^HgoO in the original oil =
3. Percentage of alcohol C^jHo^O in the original oil
i- — (rt:x 0-042)
axiS-6
s — {ax 0-042)
ax 220
s — {ax 0042)
In these formulae a designates the number of c.c. of N/i potassium
.hydroxide solution used, and s the amount of acetylated oil employed
for saponification, expressed in grams.
Aldehyde Determination by the Bisulphite Method
of Schimmel & Co.
This method depends upon the property of some aldehydes of
forming compounds with sodium bisulphite which are soluble in water.
' Semi-annual Report of Schimmel & Co., October 1894, p. 62.
CHEMICAL EXAMINATION
265
If oils rich in aldehyde, such as cassia oil, Ceylon cinnamon oil
(cinnamic aldehyde), or lemon-grass oil (citral) be shaken with a hot,
concentrated solution of sodium bisulphite, the total aldehyde will pass
into the aqueous solution, whilst the other constituents of the oil,
being insoluble in water, will float on the surface. The diminution in
volume of the oil by this process corresponds to its content of aldehyde.
For such a determination a special glass flask ^ (cassia flask or
aldehyde flask. Fig. 49) of about 100 c.c. capacity is used. This has
a neck about 13 cm. in length, 8 mm. inside diameter,
and is graduated in —^ c.c. The neck has a capacity of
somewhat more than 6 c.c, and the zero of the scale
is a little above the junction of the body of the flask
and the neck.
By means of a pipette, exactly 10 c.c. of oil are
brought into the flask, the same amount of an approxi-
mately 30 per cent solution of sodium bisulphite added,
the mixture shaken, and the flask then placed in a bath
of boiling water. After the curdy mass which is first
formed has liquefied, so much bisulphite solution is
gradually added, while being constantly heated in the
water-bath and frequently shaken, that the flask be-
comes at least three-quarters filled. The heating is
then continued for some time, or until no more solid
particles float in the liquid, and there is a layer of
clear oil on the surface of the salt solution, while the
odour of the aldehyde has disappeared. After cooling,
the flask is filled with bisulphite solution, so that the
oil rises in the neck, and the lower boundary of the oily
layer is exactly in line with the zero mark on the neck
of the flask. The number of cubic centimetres of non-aldehydic con-
stituents is then read off on the scale, and by subtracting this from
10 the aldehyde content is found.
This method can only be somewhat accurately employed for oils
which are relatively rich in aldehyde, such as cassia oil, cinnamon oil,
and lemon-grass oil. It is quite inadequate for lemon oil, which
contains but small amounts (5-8 per cent.) of aldehyde.
Fio. 49.
Determination of Aldehydes and Ketones with Neutral Sulphite,
according to Burgess (The Sulphite Method).
In place of the acid sulphite, neutral sodium sulphite may also be
used in the cassia flask for the quantitative determination of citral
and cinnamic aldehyde. Even the ketones, carvone and pulegone, may
1 Semi-annual Report of Schimmel & Co., October 1890, p. 18.
266 ESSENTIAL OILS
be determined in the same manner, which is not possible by the method
above described.
The determination is conducted in the following manner: — 5 c.c. of
the oil are brought into a cassia flask, together with a saturated
solution of sodium sulphite, and, after the addition of two drops of a
phenolphthalein solution, the mixture is heated in a water-bath, with
frequent agitation. The sodium hydroxide which is liberated by this
reaction is neutralised from time to time with dilute acetic acid (i : 5)
or with sodium bicarbonate, until a red coloration no longer appears
on further heating. The oil then is brought into the neck by filling the
flask with water, and, after cooling, its volume may be accurately
determined. The amount of oil absorbed, multiplied by 20, gives
the percentage content of aldehyde or ketone.
S. Sadtler^ has proposed to determine volumetrically the sodium
hydroxide liberated by the action of aldehydes or ketones, with the
use of rosolic acid as the indicator, and thus to calculate the amount
of aldehyde or ketone in the oil. This method, however, fails in
practice, owing to the impossibility of determining the end reaction
with precision.
Determination of Phenols.
For an approximately accurate determination, a measured quantity
of the oil to be examined is shaken with a dilute (not more than
5 per cent.) solution of sodium hydroxide. The diminution in volume
of the oil indicates the amount of phenols present. For this purpose
a burette of 60 c.c. capacity is filled to the 10 c.c. mark with a 5 per
cent, solution of sodium hydroxide. 10 c.c. of the oil to be examined
are then brought upon the surface of the liquid, the burette closed with
a tightly fitting cork, and, after shaking the mixture vigorously, allowed
to stand for twelve to twenty-four hours. Any drops of oil which may
adhere to the sides of the glass are detached by tapping or inclining
the burette. When the alkaline liquid has become clear, the amount
of non-phenolic constituents of the oil can be read off.
The cassia flask described on p. 265 can also be used for phenol
determinations in place of a burette.
Detection of Alcohol.
The adulteration of an essential oil with alcohol, which is of frequent
occurrence, is indicated in the first place by a low specific gravity.
When drops of an oil containing alcohol are allowed to fall into
water, they will not remain clear and transparent as in the case of a
pure oil, but will appear opaque or show a milk-like turbidity.
In order to separate and identify the alcohol, the suspected oil is
' J. Soc. Chetn. frui., igo^, 23, 303.
CHEMICAL EXAMINATION 267
heated until it begins to boil, the first few drops of the distillate
collected in a test tube, and then passed through a filter which has
been moistened with water, so as to remove any drops of oil which may
have been mechanically carried over. After the filtered liquid has
been made strongly alkaline with a dilute solution of potassium
hydroxide, and heated to 50°-6o'', a solution of iodine in potassium
iodide is added until a permanent yellow coloration is produced. If
alcohol be present, small crystals of iodoform will be deposited after a
time at the bottom of the liquid. It is, however, to be borne in mind
that acetone and ethyl acetate, as well as the lower aldehydes, will give
the iodoform reaction under the same conditions.
If a measured quantity of an oil containing alcohol be shaken in a
graduated cylinder with water, the increase in volume of the aqueous
layer will correspond approximately to the amount of alcohol present.
The alcohol can then be separated from the water by distillation, and
identified as described above.
The amount of alcohol in an adulterated oil may also be determined
by a comparison of the specific gravity of the oil before and after
shaking with water.
Detection of Fatty Oil.
If an essential oil is adulterated with a fatty oil, it does not yield
a clear solution with considerable amounts of 90 per cent, alcohol, and
leaves a permanent greasy stain when evaporated on writing paper. It
is to be borne in mind, however, that the essential oils obtained by
expression, such as those of bergamot, lemon, and sweet orange, produce
similar permanent stains on paper; but these oils are soluble in 90 per
cent, alcohol, and the stain is not caused by fatty oil. For the detection
of the fatty oil, the essential oil is either distilled over with steam, or
evaporated on a water-bath. The residue, when it consists of fat, will
be insoluble in 70 and 90 per cent, alcohol (only ricinus oil is soluble
in 90 per cent, alcohol, but it is insoluble in 70 per cent, alcohol) ; it
will give off the irritating vapours of acrolein when heated in a test
tube with acid potassium sulphate, and will be saponified by an
alcoholic solution of potassium hydroxide, giving a saponification value
between 1 80 and 200.
Detection of Mineral Oil.
Petroleum, mineral oil, or fractions of the latter, are practically
insoluble in alcohol, even of the highest strength, and they are, there-
fore, easily detected in essential oils. An essential oil which is
adulterated with a mineral oil will yield a turbid mixture when shaken
with 90 per cent, alcohol, but this will soon become clear on standing,
and the separated mineral oil will then float on the surface of the
alcohol. The mineral oil, when repeatedly washed with alcohol, will be
268 ESSENTIAL OILS
recognised as such by its permanence towards a solution of potassium
hydroxide, as also towards concentrated sulphuric and nitric acids.
Detection of Turpentine Oil.
The most frequentl)- observed adulteration of essential oils consists
in an addition of turpentine oil. Those oils which in a pure state
contain no pinene — the chief constituent of oil of turpentine — may be
examined for an adulteration with the latter by repeated fractional
distillation and the isolation of the respective hydrocarbon. The
portion distilling at about i6o° is separately collected, and the pinene
identified by its characteristic derivatives, for which purpose the
nitrosochloride and the bases prepared therefrom, pinene nitrolbenzyl-
amine or pinene nitrolpiperidine, are best adapted.
According to the directions given by O. Wallach,^ 50 g. each of the
respective fraction, glacial acetic acid, and ethyl nitrite (or amyl nitrite)
are well cooled in a freezing mixture, and to the mixture of the three
substances 15 c.c. of crude (33 per cent.) hydrochloric acid are gradually
introduced. The nitrosochloride soon separates in a crystalline form,
and when drained at the pump and washed with cold alcohol is obtained
sufficiently pure for further treatment. A portion of the nitrosochloride
is hydrolysed with a solution of potassium hydroxide and converted
into nitrosopinene,- melting at 132°. To another portion an excess of
an alcoholic solution of benzylamine or piperidine is added,^ the mixture
heated for a short time on the water-bath, and the nitrolamine thus
produced separated by the addition of water. The melting point of
pinene nitrolpiperidine is i i8°-i 19°, that of pinene nitrolbenzylamine,
I22°-I23°.
In those cases in which pinene is a natural constituent of an
essential oil, an adulteration with turpentine oil may be recognised by
a change in its physical constants, such as specific gravity, solubility,
and rotatory power. With regard to the optical behaviour, it should
be noted that there are both dextrorotatory and laevorotatory turpentine
oils.
Constants and Properties of some Essential Oils of
Commercial and Industrial Importance.^
Anise Oil. — From the fruits oi Piiiipinella Anisuui, Linnc.
d"^" 0-980-0-990 ; a^ laevorotatory to — i" 50' (an oil to which fennel
oil or fennel stearoptene has been added is dextrorotatory); soluble in
' Annalen, 1888, 245, 251, and 1889, 253, 251. - Wallach and Lorentz, ibid., 1891, 258, 198.
3 Wallach, ifiid., 1888, 245, 253 ; 1889, 252, I 30.
* Since it is not expedient to enumerate ail the essential oils, reference may be made to the
comprehensive work : Die (vtherischen Oe/e, by E. Gilderaeister and P'r. Hoffmann. This
contains more detailed information respecting their origin, preparation, composition, and
commercial varieties.
CONSTANTS AND PROPERTIES 269
ii-3 vols, of 90 per cent, (by volume) alcohol; congealing point
(see p. 260) + 17" to + 19^ When improperly kept the congealing point
may become depressed to below 0°, and at the same time the oil will
become heavier than water through the formation of anisaldehyde.
Anet/iole, C^^V[^S^.—d''^° 0-984-0-986 ; an ± 0° ; ;/d^^° i-SSQ-I'S^i ;
congealing point 2i°-22°; melting point 22-5°-23° ; boiling point (760
mm.) 233°-234° ; soluble in 2-3 vols, of 90 per cent, alcohol.
Bay Oil. — From the leaves oi Pimenta acris, Wight.
d'^'"'' 0-965-0-985 ; a^ laevorotatory to —3°. Usually not giving a
clear solution with 90 per cent, alcohol. Eugenol content 40-70 per
cent. The determination of the eugenol is conducted in the manner
described under Clove Oil.
Bergamot Oil. — The oil expressed from the rind of the fruit of
Citrus Bergaiiiia^ Risso.
Colour green or yellowish-brown ; (^'^^ o- 881-0-886 ; ar, -f 8" to + 24° ;
soluble in \ vol. or more of 90 per cent, alcohol. Amount of
linalyl acetate (see p. 262) 35-45 per cent; residue on evaporation,
5-6 per cent. For determining the latter, about 5 g. of the oil are
weighed accurately to i eg. in a tared glass dish, and heated on a
water-bath until the residue has completely lost the odour of bergamot
oil. After cooling, the dish is weighed with the residue. This will
amount to more than 6 per cent, of the oil if fatty oil were present.
Rectified bergamot oil is colourless, and volatilises without leaving
any appreciable residue.
Bitter Almond Oil. — Prepared by the fermentation and subsequent
distillation of bitter almonds, from Prunus Amygdalus, Stokes, or of
apricot kernels, from Prunus Armeniaca, Linne, which have been
deprived of fatty oil.
Bitter Almond Oil containing Hydrocyanic Acid. — d^^'^ 1-045-1 -070,
but with a large proportion of hydrocyanic acid the specific gravity is
higher; a^ inactive or nearly so; soluble in 1-2 vols, of 70 per cent,
alcohol.
Bitter Almond Oil deprived of Hydrocyanic Acid. — d^^" 1-050- 1-05 5 ;
boiling point 179". In order to distinguish this oil from one containing
hydrocyanic acid, 10-15 drops of the respective oil are shaken with
2-3 drops of an approximately 30 per cent, solution of sodium hydroxide,
or a corresponding amount of more dilute alkali. After the addition of
a few drops of a partially oxidised ferrous sulphate solution, the mixture
is again shaken, and then acidified with dilute hydrochloric acid, when
the precipitate of ferroso- ferric oxide will be dissolved, and, if hydro-
cyanic acid be present, the characteristic blue precipitate of prussian
blue will be formed.
For the quantitative determination of hydrocyanic acid in essential
oils various volumetric methods have been proposed, some of which.
270 ESSENTIAL OILS
however, give very poor results. The following gravimetric method has
been found most trustworthy : — About i g. of the oil is accurately weighed,
dissolved in ten to twenty times its amount of alcohol, and lo g. of a
chlorine-free, alcoholic solution of ammonia added. After standing for
a time, an aqueous solution of i g. of silver nitrate is added, and the
mixture then acidified with nitric acid. When the liquid has become
clear, the silver cyanide is collected on a dried and weighed filter,
thoroughly washed w^ith water, and dried at lOo' until the weight is
constant.
The silver precipitate thus obtained contains the entire amount of
hydrocyanic acid present in the oil, whereas without the preceding
treatment with ammonia, w^hich decomposes the mandelic nitrile, only
a part of the hydrocyanic acid would be determined.
Detection of Chlorine. — Synthetic bitter almond oil prepared from
benzyl chloride or benzylidene chloride, is more or less contaminated
with chlorinated products. Since synthetic benzaldehyde is much used
to adulterate true bitter almond oil, its presence can be ascertained by
the detection of chlorine. Synthetic cinnamic aldehyde likewise some-
times contains chlorine, and the detection of chlorine in cinnamon oil
is similarly evidence of its adulteration with the synthetic aldehyde.
It should specially be noted, however, that synthetic benzaldehyde and
cinnamic aldehyde which are free from chlorine now also occur in
commerce.
For the detection of chlorine a piece of filter paper 5x6 cm. in size
is folded in the form of a taper, soaked in the oil to be examined, and _
the excess of oil thrown off by two short shakings with the hand. The
paper thus prepared is brought into a small porcelain dish, which is
placed in a larger one of about 20 cm. diameter, and lighted by a flame.
A beaker of about 2 litres capacity, which has been moistened on the
inner surface with distilled water and kept ready for the purpose, is then
quickly inverted over the burning taper. The gaseous products of
combustion condense on the moist walls of the beaker, and are washed
with 10 c.c. of distilled water on to a filter. The filtrate should give no
turbidity, much less a precipitate of silver chloride, on the addition of
a solution of silver nitrate. The genuine oil, that is, such as has been
distilled from bitter almonds or from peach kernels, never gives a reaction
for chlorine.
The above-described method of testing the oil has proved to be
infallible. In order, however, to be certain of the result, a control test
should always be made with a pure distilled oil, since an incorrect
opinion might be formed if the water and the vessels employed were
not perfectly free from chlorides.
Caraway Oil — From the fruits of Carum Carvi, Linne.
^^5° 0-907-0-9I5 ; au+70 to +80°; soluble in 3-10 vols, of 80 per
CONSTANTS AND PROPERTIES 271
cent., or i vol. of 90 per cent, alcohol. Carvone content 50-60 per
cent, (to be determined according to the sulphite method described
on p. 265).
Carvone {Carvol), C^^U^p.—d^'^" o-ge^-o-gGG ; boiling point 229"-230° ;
"d +57°to +60" ; soluble in 16-20 vols, of 50 per cent, alcohol at 20° or
in ^-2 vols, of 70 per cent, alcohol ; n^'^^° 1-497- 1-500.
Cassia Oil, Chinese Cinnamon Oil. — From the leaves of the Chinese
cinnamon, Citinamonuni Cassia^ Blume.
d}^'' I-055-I-070; optically inactive or slightly l?evo- or dextro-
rotatory ; soluble in 2-3 vols, and more of 70 per cent alcohol,
usually with opalescence. Cinnamic aldehyde content (see p. 264) 75-90
per cent. The residue obtained by distillation from a fractionating flask
with a low side tube amounts to 6-8, or, at the most, 10 per cent. This
residue should be pasty, but not hard or brittle, as would be the case if
the oil were adulterated with colophony. Such an addition to the oil
may also be detected in the following manner : — To a solution of
I vol, of cassia oil in 3 vols, of 70 per cent, alcohol is added, drop
by drop, an amount up to \ vol. of a freshly prepared solution of lead
acetate in 70 per cent, alcohol, which has been saturated at the room
temperature. If a precipitate is produced, it indicates the addition
of colophony.
Cinnamon Oil, Ceylon. — From the bark of Cinnanioninn zeylanicuniy
Breyne.
d}-^° 1-023-1-040; od laevorotatory to —1°; soluble in 2-3 vols, of
70 per cent, alcohol ; cinnamic aldehyde content 65-75 per cent., as
determined by the bisulphite method (see p. 264).
Citronella Oil. — From the herb of Cymbopogon Nardus, Stapf.
There are two sorts of this oil, the Ceylon and the Java, the latter
being the more valuable.
Ceylon Citronella Oil. — ^^° 0-900-0-920; au laevorotatory to —21".
It should yield a clear solution with 1-2 vols, of 80 per cent, alcohol,
and with 10 vols, of this solvent should give a solution which is at
most opalescent, but which, on standing, should separate no drops of
oil (Schimmel's Test). The oil should also meet these requirements
after the addition of 5 per cent, of Russian petroleum (Stricter
Schimmel's Test). The apparent amount of alcohol, C\oH^gO
(geraniol + citronellal), as determined by acetylation, at least 57 per
cent, (for method of determination see p. 263).
Java Citronella Oil. — <a^^° 0-886-0-900; od laevorotatory to —5°;
soluble in i or 1-2 vols, of 80 per cent, alcohol. Amount of alcohols,
CjoHigO, usually more than 80 per cent.
Clove Oil. — From the dried flower-buds of Eugenia caryopJiyllata^
Thunberg.
d^^° 1-044-1-070; a-o laevorotatory to —1° 15'; soluble in 1-2 vols.
272 ESSENTIAL OILS
of 70 per cent, alcohol. Eugenol content 80-90 per cent, and
more.
Clove Sicui Oil'is distilled from the stems of cloves, d^^' i 040-1 065 ;
optical rotation and solubility the same as clove oil. Eugenol content
85-95 per cent.
The determination of the eugenol is conducted either in a cassia
flask (Fig. 49, p. 265), with a 3 per cent, solution of sodium hydroxide,
or according to Thoms' improved method/ which also permits of
determining the eugenol contained in the oil in the form of ester.
This method is carried out as follows : — To 5 g. of clove oil are
added 20 g. of a solution of sodium hydroxide (15 per cent.), and the
mixture gently heated on a water-bath for half an hour, when a layer
of sesquiterpene separates on the surface of the liquid. The contents
of the beaker, while still warm, are brought into a small separator with
a short discharge tube, and the eugenol-sodium solution, which soon
settles well, returned to the beaker. The sesquiterpene which remains
in the separator is washed twice with a 15 per cent, solution of sodium
hydroxide, using 5 c.c. each time, and these washings added to the
eugenol-sodium solution. To this solution 6 g. of benzoyl chloride are
added, and the mixture shaken, whereb)- the formation of benzoyl-
eugenol is at once effected, with the development of considerable heat.
The last portions of unattacked benzoyl chloride are decomposed by
heating for a short time on the water-bath. After cooling, the liquid
above the solidified ester is removed by filtration, any small crystals
which may have got on to the filter being washed with 50 c.c. of water
into the beaker, and the mixture heated until the crystalline cake again
forms an oil. After gentle agitation it is again allowed to cool, the
supernatant clear liquid removed by filtration, and the cake, previously
melted, washed twice in the same manner as before with water, using
50 c.c. each time. To the bcnzoyleugenol, while still moist, 25 c.c. of
alcohol (90 per cent, by weight) are immediately added, and the
mixture heated on a water-bath, with gentle agitation, until solution is
effected. After removing the beaker from the water-bath, the agitation
of the contents is continued until the bcnzoyleugenol separates in the
form of small crystals, which takes place within a few minutes. It is
then cooled to a temperature of 17 , the precipitate brought on a filter
of 9 cm. diameter, and the filtrate allowed to flow into a graduated
cylinder, in which it may occupy a space of about 20 c.c. The alcoholic
solution which may still be retained by the crystalline magma on the
filter is displaced by the addition of so much alcohol (90 per cent, by
weight) that the entire filtrate amounts to 25 c.c. The filter with the
precipitate, while still moist, is transferred to a weighing tube, previously
dried with the filter at loT' and weighed, and the whole heated at 101°
• Arch. Pkarm., 1 903, 241, 592.
CONSTANTS AND PROPERTIES 273
until the weight is constant. At 17° the amount of pure benzoyleugenol
dissolved by 25 c.c. of 90 per cent, alcohol is 05 5 g., and this weight
must therefore be added to that of the quantity found.
U a designates the amount of benzoic ester found, d the amount of
clove oil used (approximately 5 g.), and if 25 c.c. of alcoholic solution
are filtered from the ester under the above-mentioned conditions, then
the percentage of eugenol in the clove oil is found according to the
following formula : —
4100(^ + 0-55).
6y.d
This formula is derived from the two equations : —
Benzoyleugenol Eugenol
268 : 164 =(<3: + o-55): the amount of eugenol found.
T-. , i64.(« + o-55)
Eugenol = — =^^^^^7^ — ^^^.
268
Therefore, b : iM^+^iD = 100 : .^ir
268
_ i-64(^? + o-55). 100 ^ 4100(^ + 0-55)
^ ~ - 268.^ 67. b
Eucalyptus Oil. — From the leaves of Eticalyptus globulus, Labil-
lardiere.
d>^" 0-910-0-930; Od +1° to +15^; soluble in 2-4 vols, of 70 per
cent, alcohol. An adulteration with the less valuable laevorotatory oil
of Eucalyptus ainygdalina, LabilL, which consists almost entirely of
phellandrene, Qo^ig. is tested for by adding to the oil, diluted in a
test tube with twice its volume of light petroleum, a concentrated,
aqueous solution of sodium nitrite. If now acetic acid be added in
small portions, phellandrene nitrite will separate in a flocculent form
in case this hydrocarbon be present.
In order to determine quantitatively the cineol,^ the most important
constituent of eucalyptus oil, 100 c.c. of the latter are distilled from
the Ladenburg fractionating flask, described on p. 262, in such a
manner that about one drop passes over per second. In the fraction
boiling between 170° and 190°, after diluting it with an equal volume
of turpentine oil, the cineol content is determined in the following
manner: — To 10 c.c. of the mixture, consisting of the respective
fraction and turpentine oil, and contained in a cassia flask of 100 c.c.
capacity (p. 265), is added so much of a 50 per cent, resorcinol solution
that the flask is about four-fifths filled. The mixture is then vigorously
shaken for five minutes, after which the portions of oil which have not
entered into the reaction are brought into the neck of the flask by
1 Semi-annual Report of Schimmel & Co., October 1907, p. 47, and April 1908, p. 50.
J. Soc. Chem. Ind.^ 1 908, 27, 90.
Ill S
274 ESSENTIAL OILS
filling the latter with the resorcinol solution. As soon as the liquid
has become perfectly clear, or nearly so, which usually requires several
hours, the volume of unchanged oil is read off. Any drops of oil
which may remain attached to the sides of the vessel are brought to
the surface by a frequent rotation and tapping of the flask, and the
amount of cineol thus determined is calculated to its percentage by
volume in the original oil. The cineol content of good Eucalyptus
globulus oils should be from 55-80 per cent.
This method depends upon the property of cineol of forming an
addition product with resorcinol which is soluble in water.
Eucalyptol {Cineol), Z^^^f^. — d}^° 0-928-0-930 ; Oi, ±0^ ; boiling point
I76''-I77°; ^n^o^ 1-458; melting point between +i°and +1-5°.
Fennel Oil. — From the fruits oi Foeniculum vulgare, Miller.
d^^° 0-965-0-977 ; ai,+ i2' to +18', rarely higher; soluble in 5-8
vols, of 80 per cent, alcohol (sometimes with turbidity), and in
I vol, of 90 per cent, alcohol. Congealing point (see p. 260), not
below +5°.
Geranium Oil. — From the leaves of different species o{ Pelargofiium.
(Palmarosa oil is also incorrectly designated as Turkish or Indian
geranium oil).
d}^° o- 890-0- 907 ; an —6" to —16''; acid value 3-12; ester value
42-78 ; soluble in 3 vols, of 70 per cent, alcohol, sometimes with separa-
tion of a paraffin hydrocarbon.
Lavender Oil.— From the flowers oi Lavayidula officinalis^ Chaix.
^^''' 0-883-0-895 ; a,,-,—y to —9°; soluble in 3 vols, of 70 per cent,
alcohol; linalyl acetate content 30-55 per cent, and more (for method
of determination, see p. 262).
The requirements of the German tax commissioners for a lavender
oil which is to be used for denaturing purposes, but which are not
sufficient for differentiating between adulterated and pure oils, are as
follows: — The density of lavender oil at 15° should be between 0880
and 0-900; 10 c.c. of lavender oil at 20° should )'ield a clear solution
with 30 c.c. of spirit containing 6"^) per cent, by weight of alcohol.
Lemon Oil. — Obtained by expression from the rind of the fruit of
Citrus Lijnonujfi, Risso.
d^^° 0-857-0-86I ; 0^+58" to ^-es" at 20"; soluble with turbidity in
90 per cent, alcohol, but giving a clear solution with absolute alcohol.
Residue on evaporation 2-5-3-5 P^r cent, (the method of determination
is described under Bergamot Oil, p. 269). Among the numerous
published methods for the determination of the citral content none
has proved satisfactory.
Lemon-grass Oil. — From the herb of Cyiiibopogon flcxuosus, Stapf.
^/'^ 0-895-0-905 ; ay dextro- or kcvorotatory -f T to —5°; soluble
in 2-3 vols, of 70 per cent, alcohol, but occasionally showing a slight
CONSTANTS AND PROPERTIES 275
turbidity by a further addition of the solvent. Citral content, determined
by the bisulphite method (p. 264), 70-85 per cent., by the sulphite
method (p. 265), 65-80 per cent. In reporting on the citral content
it should be stated which method has been used for its determination.
Citral, QoHipO.— ^15° 0-892-0-895 ; an±o°; 11^20° i -4880-1 -4886 ;
boiling point 228°-229°.
Linaloe Oil. — From the wood of different species o{ B7irsera.
d^^° 0-875-0-890; «,, — 3' to —5°, less frequently dextrorotatory
-1-3° to +8°; saponification value 1-25; soluble in 2 vols, of 70 per
cent, alcohol.
Mustard Oil, true. — From the seed of Brassica nigra, Koch, and
Brassica Juncea, Hooker.
d^^° I -014-1 -025 ; Od ± o' ; boils for the most part between 147° and
153° (760 mm.); soluble in every proportion in 90 per cent, alcohol.
Allyl isothiocyanate content more than 90 per cent.
Mustard Oil, synthetic. — d^''>° 1-020-1-025; u^±d'. Boils chiefly
between 150° and 153° (760 mm.). «d-° 1-527-1-529,
Determination of the Allyl Isothiocyanate in Mustard Oil. — A method
for the quantitative determination of sulphur in mustard oil has been
devised by J. Gadamer^ and improved by M. Kuntze.^ The mustard oil
is converted by ammonia into thiosinamine (allyl thiocarbamide), and
the latter by an ammoniacal solution of silver nitrate into silver
sulphide, allyl cyanamide, and ammonium nitrate, in accordance with
the equation : —
C3H5.NCS + 3NH3-f2AgN03 = Ag2S + C3H5.NCNH + 2NH,N03.
In order that this reaction should proceed smoothly, a large excess
of silver nitrate is necessary. If conducted in alcoholic solution, it is
also necessary that this should be heated, as otherwise the results are
too low. The excess of silver nitrate is titrated back with tV/io
ammonium thiocyanate solution.
For testing the mustard oil it is first converted into the Spirit of
Mustard {Spij-itus Siiiapis of the German Pharmacopceia) by mixing
2 g. of the oil with 98 g. of alcohol (sp. gr. 0-830-0-834).
The determination is carried out as follows: — To 5 c.c. ( = 4-2 g.) of
the spirit, contained in a flask of 100 c.c. capacity, are added 50 c,c. of
N\io silver nitrate solution and 10 c.c. of solution of ammonia (sp. gr,
0-960). After closing the flask with a cork, through which a glass tube
I m. in length is passed, the mixture is heated for an hour on a water-
bath in which the water is in active ebullition. It is then cooled to 15°,
the flask filled to the 100 c.c. mark with distilled water, and the mixture
filtered. In 50 c.c. of the clear filtrate, after the addition of 6 c.c, of
1 Arch. Pharnu, 1899, 237, IIO, 372 ; /. Chetn. Soc. Ahslr., 1899, 76, ii., 712.
2 Arch. Pharm., 1908, 246, 58 ; /. Chem. Soc. Ahsir., 1908, 94, ii. 440,
276 ESSENTIAL OILS
nitric acid (sp..gr. 1153), the excess of silver nitrate is determined by
titration with .\'io ammonium thiocyanate solution, ferric ammonium
sulphate or ferric sulphate being used as the indicator.
Since 2 mols. of silver nitrate (M.VV. = 340) correspond to i mol.
of allyl mustard oil (M.W. = 99), i c.c. Xjio silver nitrate solution
( = 0017 g. AgXOg) is equivalent to 000495 g- of allyl mustard oil.
Nutmeg Oil. — Distilled from nutmeg, the kernel of the seed of
Alyristica fragratis, Houttuyn.
d'^^' 0-S70-0-925 ; 00+7"^ to +30' ; soluble in 1-3 vols, of 90 per cent,
alcohol.
Orange Oil, bitter. — Expressed from, the rind of the fruit of the
bitter orange, Citrus Bigaradia, Risso.
d^^° 0-853-0-857 ; a„ +90" to +93° at 20° C. Does not form a clear
solution with 90 per cent, alcohol. Residue on evaporation (see under
Bergamot Oil, p. 269) 3-5 per cent.
Orange Oil, sweet. — Expressed from the rind of the fruit of the
sweet orange, Citrus Aurantiuni, Risso.
dif 0-848-0-853 ; a^ +95° 30' to +98'^ at 20' C. Does not form a
clear solution with 90 per cent, alcohol. Residue on evaporation 2-4
per cent.
Orange Flower Oil. Oil of Neroli. — A distillate from the flowers
of the bitter orange. Citrus Bigaradia, Risso.
d^-'' 0-870-0-880; au + i"" 30' to +8^; soluble in 1-2 vols, of
80 per cent, alcohol, but on the further addition of the solvent a
turbidity usually occurs owing to the separation of a paraffin ;.
saponification value 24-55.
Palmarosa Oil (also incorrectly termed Indian or Turkish
Geranium Oil). — From the herb of Cymbopogon Martini, Stapf
d^^" 0-888-0-900; a^ slightly dextro- or hevorotatory +6^ to —2°
30'; soluble in 1-5-3 vols, of 70 per cent, alcohol; saponification
value 14-46; saponification value after acetylation not below 225.
Patchouli Oil. — From the leaves oi Pogostemon Patchouli, Pelletier.
d^-' 0-970-0-995 ; ai,— 50° to —68''; soluble in i vol. of 90 per
cent, alcohol.
Peppermint Oil. — From the herb of Mentha piperita, Linne.
There are various commercial sorts of this oil, of which the English,
.American, and Japanese are the most important.
English or Mitcham Peppermint Oil. — cP-'^" 0-900-0-9IO; «„ — 22^ to
— 33"; soluble in 3-5 vols, of 70 per cent, alcohol. Amount of
ester menthol {i.e. menthol present in the form of ester, calculated
as menthyl acetate, Ci(,Hj(,0. COCII.;) 4-12 per cent. = saponification
value 14-41 ; total menthol (free menthol + menthol ester) 50-63 per
cent. = saponification value after acetylation 164-194.
American Peppermint Oil. — a^'-'^' ogoo-o-gio ; a,, — 18'' to —33°.
CONSTANTS AND PROPERTIES 277
Some oils only dissolve in | vol. and more of 90 per cent, alcohol,
whilst others are soluble in 4-5 vols, of 70 per cent, alcohol. Ester
menthol 3-10 per cent, (saponification value 10-36), total menthol
50-61 per cent, (saponification value after acetylation 158-188).
Japanese Peppennint Oil. — At the ordinary temperature a normal
oil is a semi-solid mass, interspersed with crystals of menthol. The
commercial oils are mostly such as have been deprived of a part of
the menthol, and which therefore vary exceedingly with respect to
density, rotatory power, and menthol content. The differentiation of
the individual sorts of peppermint by a physical and chemical examina-
tion is very difficult, and impossible in the case of mixtures of
different oils.
Rose Oil. — From the flowers of Rosa daniascena, Miller.
^^*^° 0-849-0-862 ; a^ — 1" 30' to —3°. On account of the paraffin
hydrocarbons present, the oil does not give a clear solution with 90
per cent, alcohol. Acid value 0-5-3-0; ester value 8-16; total
geraniol content (geraniol + citronellol) 66-75 per cent, (see p. 263).
Congealing point {i.e. the temperature at which the oil, when slowly
cooled, begins to separate the stearopten or paraffins) +19° to +23°-5.
In order to determine the congealing point of rose oil, 10 c.c. of the
oil are brought into a test tube of 15 mm. diameter, and a thermometer
then immersed in it so that it can move freely without touching
the sides of the glass. After the test tube has been warmed to such
an extent that all the stearopten is melted, the contents are slowly
cooled until the first crystals appear.
Rosemary Oil, Italian. — From the flowers of Rosmarinus officinalis^
Linne.
^^° 0-900-0-920; a^ dextrorotatory to +15°; soluble in \ vol.
and more of 90 per cent, alcohol. If from 50 c.c. of the oil, contained
in the flask described on p. 262, 5 c.c. are slowly distilled off', the
distillate should be dextrorotatory. If it is laevorotatory, this is
almost always due to an adulteration with French oil of turpentine.
It should, however, be noted that there are also pure natural products
of which the first 10 per cent, which passes over is slightly laevo-
rotatory. The German tax commissioners no longer give definite
directions for the examination of rosemary oil which is to be used for
denaturing fatty oils.
Sandalwood Oil. — From the wood of Santaluni album, Linne.
(^^° 0-975-0-983 ; un—i^" to —20''; soluble in 5 vols, of 70 per
cent, alcohol at 20°, and this solution should not be rendered turbid by
the further addition of 70 per cent, alcohol ; saponification value 5-20.
Santalol content, calculated for C^gH^^O, at least 91 per cent, (for
method of determination, see p. 263).
Sassafras Oil. — From the root of Sassafras officinalis, Nees.
278 ESSENTIAL OILS
d^'"" I -070- 1 -082 ; rtu+3 to +4'; soluble in 1-2 vols, of 95 per
cent, alcohol.
Safrol, CioHj.,Oo.— ^^' 1105-M07; a^ ± O \ boiling point 233°
(760 mm.); 71^20° i-536-i-540. Congealing point 11 . Safrol often
solidifies with great difficulty, and the crystallisation should therefore
be initiated by introducing a crystal of the substance.
Spike Oil. — Distilled from the flowers of Lavandula Spica, DC.
f/'' 0-905-0-9I5; a^ dextrorotatory to +7"; soluble in 1-5-3 ^'o^^-
of 70 per cent, alcohol. The best spike oils dissolve in 15-20 vols,
of 60 per cent, alcohol. Saponification value 5-20.
Star-anise Oil. — From the fruits of Illiciuui atnsatinn, Linne.
d^^° 0-980-0-990 ; od slightly laevorotatory to — 2', seldom slightly
dextrorotatory; soluble in I-5-2-5 vols, of 90 per cent, alcohol.
Congealing point (see p. 260) + 15'' to + i8^
Thyme Oil. — From the fresh flowering herb of Thymus vulgaris,
Linne.
(P^'"'' 0-900-0-9I5; a^ slightly l.-evorotatory ; phenol content (thymol
and carvacrol) 20-30 per cent, (for method of determination see p. 266) ;
soluble in 1-2 vols, of 80 per cent, alcohol.
Tliymol, CioHi^G. — d^-'' 1-028; crystallised thymol sinks in water,
but in a fused state floats upon it. Melting point 50-51° ; boiling point
228"-23o' ; readily soluble in alcohol, ether, chloroform, and the aqueous
.solutions of caustic alkalis, but very slightly soluble (i : iioo) in pure
water.
Turpentine Oil. — Distilled from the turpentine of various species
of Pi)ius.
American Turpenti?ie Oil. — ^^^° 0-865-0-870; a^ dextrorotatory to
-f 15", very seldom slightly laevorotatory; soluble in 5-7 vols, of
90 per cent, alcohol, old resinified oil being more readily soluble. On
distillation 85 per cent, passes over between 155' and 163^
French Turpentine Oil.—d>^° 0-865-0-876; od - 20' to -40°. The
other properties are the same as those of the American oil.
Spanish Turpentine Oil — This possesses the same constants as the
French oil.
Grecian Turpentine 6>//.— rt!^^° 0-863-0-870 ; a,, +36' to -(-40. Other-
wise the same as the American oil.
Pine-tar Oil (Ger. Kienol) is a product of the dry distillation of coni-
ferous roots, and may be recognised by its disagreeable, empyreumatic
odour, d^-'" 0-862-0-875; aD+14' to -I-24.'' It boils between 160'
and 180'.
Turpentine oil has been much adulterated in recent years, chiefly
with fractional products from petroleum (benzine, etc.), rosin essence,
carbon tetrachloride, pine-tar oil, and many other substances. The
detection, and especially the quantitative determination of these
CONSTANTS AND PROPERTIES
279
™,
!J?,
additions, is often difficult ; for a critical consideration of the respective
methods reference should be made to the work of J. Marcusson and
H, Herzfeld.i
An addition of benzine may be recognised by a lowering of the
specific gravity, since that of pure turpentine oil is between 0-865 ^^^^
0-875, whilst the benzine fractions commonly used to adulterate it,
which boil from ioo''-i8o°, have a density between 0-73 and oSo. The
indices of refraction are also different, that of turpentine oil being
I-47I-I-4735 and that of benzine 1-419-1-450. According to Herzfeld
the addition of benzine may also be recognised by fractional distillation.
In the case of a pure oil the refraction indices of the individual fractions
will differ but slightly from each other, whereas
the portions containing benzine will exhibit great
differences.
The quantitative determination of petroleum in
turpentine oil is carried out according to W. M.
Burton - as follows : — 300 c.c. of fuming nitric acid
are allowed to drop slowly from a dropping funnel
into 100 c.c. of the adulterated oil, contained in a
capacious flask provided with a reflux condenser, the
mixture being kept well cooled. The product of the
reaction is then washed with hot water, and the
residual petroleum weighed.
For this method of determination H. Herzfeld^
has constructed a small apparatus (Fig. 50), which
renders it possible directly to read off the amount
of mineral oil which has not been attacked by the
nitric acid.
Herzfeld^ subsequently recommended the use of
fuming sulphuric acid in the place of nitric acid.
10 c.c. of the turpentine oil to be tested are allowed
to drop slowly, with moderate cooling, into 40 c.c.
of concentrated sulphuric acid. After ten to twelve hours from 8-9
per cent, of the turpentine oil used will separate. The lower dark
brown layer is then drawn off, and the residual oil again shaken with
3-4 c.c. of fuming sulphuric acid. After standing for several hours
only 0-I-0-2 c.c. of oil will then separate, whereas if a mineral oil be
present, the volume will be correspondingly greater.
According to Marcusson it is better to treat the sample of oil at
— lo' with fuming nitric acid ; but opinion is still divided respecting the
relative merits of the nitric acid and sulphuric acid methods. The
1 CAem. Zeit., 1909, 33, 966, 985, 1081 ; 1910, 34, 285 ; 1912, 36, 413, 421. C/. also / Soc
Chem. Ind,, 1909, 28, 1096.
2 Amer. Chem. J., 1890, 12, 102 ; /. Soc. Chem. Ind., 1890, 9, 557.
3 Chem. Zentr., 1903, i, 258. *^Ibid., 1904, i, 548.
Fig. 60.
280 ESSENTIAL OILS
results vary greatl}', especially for the reason that the different sorts of
petroleum (from America, Russia, Galicia, Sumatra, and Borneo) show
a very different behaviour towards the two acids.
Pine-tar oil may be recognised by the fact that a fragment of
potassium hydroxide, when brought into the liquid, will soon become
coated with a )-ellovvish-brown layer. In the case of pure turpentine
oil, considerable time will elapse before the formation of such a layer
occurs. Old, resinified oils should be distilled before the application of
this test. Pine-tar oil, in amounts of not less than lo per cent, may be
detected by the yellowish-green coloration produced by sulphurous
acid (Herzfeld's reaction).^
Rosin essence may be recognised, apart from the low temperature
at which the liquid begins to boil, by Grimaldi's reaction, which
depends upon the collection of fractions of oil, in armounts of 3 c.c. each,
up to a temperature of 170°, and the green coloration which they
yield with a fragment of tin and hydrochloric acid.
Carbon tetrachloride, which, on account of its higher density, is used
to conceal an adulteration with benzine, may easily be detected by
Beilstein's copper test, or by the separation of potassium chloride when
boiled with an alcoholic solution of potassium hydroxide, as also by
fractional distillation. For its quantitative determination when mixed
with turpentine oil and benzine, the chlorine content of the mixture is
determined according to the method of Carius. Pure carbon tetra-
chloride contains 92-2 per cent, of chlorine.
^ Cf. also Wolff, Chem. Zeit. Rep., 1912, 36. 64 ; /. Soc. Chem. Ind., 1912, 31, 692 ; and Piest,
Chem. Zeit., 1912, 36, 198 ; /. Soc. Chem. Ind., 1912, 31, 239.
Literature.
GiLDEMEiSTKR, E., AND HOFFMANN, F. — Die AetJierisclien Oele, 2nd edition, vol. i.,
1910 ; vol. ii., 1913.
English translation of above by E. Kramers. The Volatile Oils, first edition, 1900;
second edition, vol. i., 1913.
Parry, E. J. — The Chemistry of Essential Oils and Artificial Perfuvies, 2nd edition,
1908.
Semmler, F. W. — Die Aethetischen Oele, 1906-7, 4 vols.
TARTARIC ACID
By W. Klapproth, Dr Ing., Chemist to Messrs C. H. Boehringer, Nieder-Ingelheim,
on Rhine. EngHsh translation revised by W. A. Davis, B.Sc, Rothamsted
Experimental Station.
The residues from the manufacture of wine are the raw materials for
the tartaric acid industry. From these residues are manufactured
tartaric acid, cream of tartar, and several other salts of tartaric acid,
such as Rochelle salt, normal (" neutral ") potassium tartrate, tartar
emetic, and tartrate of iron.
These raw materials may be classified as follows : — Lees, taj'tars
(especially the so-called " almnbic^' and " vinaccia " tartars) and " tartrate
of limey They are obtained by drying, or by crude processes of
crystallisation, or precipitation, from the residues obtained in the manu-
facture of wine. The tartaric acid is present in these materials in the
form of potassium hydrogen tartrate (bitartrate), or as normal calcium
tartrate, or as a mixture of both these substances ; the proportions are
very variable.
Wine-lees, the sediment that settles out from the completely
fermented must, is the most important raw material. In the moist
condition, as obtained by pressing out the new wine from this sediment,
lees form a sticky, clay-like mass, with an odour of wine, and having a
dirty yellow to dark red colour. The lees are dried as quickly and
rapidly as possible, in order to avoid the decomposition of the tartaric
acid by the growth of moulds or bacteria, and are usually put on the
market in this form as dried lees. They consist of yellowish to dark red,
irregularly shaped lumps, with an average size about that of a walnut.
The content of tartaric acid is usually between 15-30 per cent, but is
sometimes as high as 40 per cent., although lees of the latter grade are
seldom or never worked in this country. The tartaric acid is present
as acid potassium tartrate and calcium tartrate in variable proportions.
The rest of the material is made up of the dried yeast-cells, small
amounts of inorganic salts, and " impurities " which arise from the grape-
juice, or from the materials used in treating the wine (grape-skins,
stalks, pips, clay, sulphur, sand, and gypsum). Lees are differentiated
according to the place of origin as Italian, Spanish, French, Austrian,
and Levantine. The last-named includes Dalmatic, Greek, Turkish,
and South Russian lees. Lees show very marked differences, especially
281
282 TARTARIC ACID
as regards working, according to their place of origin ; analyses have
been published by Warington, Rasch, and Ciapetti.^
The name of" Tartars" comprises the raw materials which contain
more than 40 per cent, of tartaric acid. A distinction is to be made
between cask-tartars, obtained by the chipping of the scale from wine
casks, and the tartars obtained by boiling out with water the lees and
ma?c or vinacce from the manufacture of wine, and subjecting the
liquors to crystallisation ; tartars obtained in this latter way form the
hicrher-<irade tartars, such as Vinacda tartar. The best half-refined
tartar, known as St Antinio tartar, serves for the manufacture of cream
of tartar, Rochclle salt, and other tartaric acid salts.
Linio, Sablon, and Tartrate of Lime are raw materials obtained by
the precipitation of tartaric acid in tartar works or wine-distilleries.
I. Raw Materials.
Owing to the relatively high value of raw materials for the manu-
facture of tartaric acid and the fact that they are frequently very
far from uniform in character, the sampling must be carried out with
very special care. For this purpose a portion of the material is taken
from each cask or sack, and in general the procedure described in Vol.
I., Part I., pp. 12-14 is followed. The material is first coarsely ground
in the factory mill during the sampling, and then, before analysis, again
finely ground in the laboratory in an ordinary small hand-mill (coffee
mill) kept solely for this purpose.
In judging the raw material, both the total percentage of tartaric
acid and the percentage of tartaric acid present as bitartrate
are of importance ; the former is necessary in all branches
of the tartaric acid industry, whilst the latter is essential in the
manufacture of cream of tartar and of salts of tartaric acid. The
analytical results for the so-called " Total acid " are given as the
percentage of tartaric acid in the raw material ; the " Bitartrate " is
expressed either as the percentage of potassium h}-drogen tartrate, or
as its equivalent in tartaric acid. In England the latter method has been
generally used in the analysis of lees and tartars. It is not a general
practice to return the percentage of moisture present in the sample,
although by neglecting this, not only can differences of analysis arise,
but also an essential factor for judging the raw material is left out of
account. Insufficiently dried samples often lose several per cent, of
tartaric acid in a few weeks, owing to the development of moulds and
bacteria ; even apparently well-dried samples of lees, when kept in
carefully sealed glass bottles, have been shown to lose from 1-3 per cent,
of their tartaric acid in five years. Moreover, slimy substances are
^ See Literature, p. 295.
RAW MATERIALS 283
produced in insufficiently dried material owing to the growth of moulds,
and these give trouble in subsequent factory working. It is therefore
desirable to determine the percentage of moisture obtained by drying
the sample at ioo°.
In estimating either the bitartrate or the total tartaric acid, the
tartaric acid is precipitated in the form of the acid potassium salt, which
is then determined by titration. For the titration, A710, A^/5, NJ2, or
Ay I potassium hydroxide is used, which must be free from carbon
dioxide ; it is standardised by titration with specially recrystallised
potassium hydrogen tartrate (dried at 100") under exactly the same
conditions of concentration as are used in the actual determination. As
indicator, sensitive reddish-violet litmus paper is used exclusively ; the
same paper must be used in standardising as in the actual estimation.
The test is made by " spotting."
The molec. wt. of tartaric acid = 150.
„ „ potassium hydrogen tartrate = 188.
I. The Estimation of Acid Potassium Tartrate (Bitartrate).
An approximate es.timation of bitartrate is effected by simple
titration. With lees of average quality containing from 20-30 per
cent, of tartaric acid, the results obtained in this way are from 3-5 per
cent, higher than the true bitartrate values, owing to the presence of
acid salts and organic substances of acid character ; with unadulterated
tartars the difference is smaller. This method does not accordingly
indicate the adulteration of the raw material with acid substances such
as alum.
Approximate results are also obtained by several other methods
which were formerly in use, such as the " Ignition method " and the
" Methode a la casserole." In the former method, the material was
burnt, the ash extracted with water and the dissolved potassium
carbonate estimated. In the French " casserole test," the sample was
extracted with boiling water and the crystals which separated on
cooling weighed. The methods described in detail by P. Carles ^ are
not applicable, because when certain impurities are present, either by
accident or design, quite incorrect results are obtained.
The method of Philips & Co.'-^ consisted in exactly neutralising the
bitartrate with potassium hydroxide and reprecipitating it from the
filtered solution by acetic acid and alcohol. When other calcium salts
are present, such as gypsum, the results obtained are too high.
F. Klein ^ boils the sample with water, evaporates the filtered solu-
tion to a small volume, and precipitates the bitartrate by adding
potassium chloride. The precipitate is filtered off, washed with a 10 per
1 Les Derives Tartriques, 1903 ; Z. angew. Ckem., 1898, II, 183.
2 Z. anal. Chem., 1890, 29, 577. ^ Ibid., 1885,24, 379.
284 TARTARIC ACID
cent, solution of potassium chloride which has previously been saturated
with the bitartrate, and then titrated. This method, which is based on
Warington's process for the estimation of the total tartaric acid, is not
now in general use, although it gives good results ; it has been much
recommended by Fabre.^
The most-used commercial method, the so-called " Oulman's
method," is described by Stiefel- as follows :— 3-76 g. of the finely
powdered tartar is placed in a litre flask, 750 c.c. of water added, the
latter heated to boiling and kept in ebullition for not more than
five minutes. The flask is then filled to the mark with distilled water
and allowed to cool. After cooling, the volume is adjusted to the exact
litre and the solution filtered through a dry filter. Of this solution,
500 c.c. are evaporated to dryness on the water-bath in a porcelain
dish, the residue moistened with 5 c.c. of water, and after cooling, mixed
with 100 c.c. of 95 per cent, alcohol. After standing for thirty minutes
the alcohol is decanted through a dry filter paper, allowed to drain
thoroughly, and any potassium bitartrate which has passed on to the
filter paper is washed back into the dish with boiling water. The
solution is then made up to about 100 c,c. and titrated whilst hot with
A75 potassium hydroxide. To the number of cubic centimetres of
alkali used 0-2 c.c. is added to correct for the loss of bitartrate in the
alcohol mother liquors.
All methods for estimating bitartrate are scientifically not quite
accurate, as changes may occur in boiling out the samples ; for this
reason, too prolonged boiling should be avoided.
2. The Estimation of the Total Tartaric Acid.
The older methods of Scribani, Scheurer-Kestner, and Oliveri,
based on the precipitation and weighing of calcium tartrate, have been
abandoned on account of their inaccuracy.
The first scientifically sound method was that of R. Warington,^
the principle of which is as follows : — The calcium present was
precipitated as oxalate by means of neutral potassium oxalate, the
mass neutralised with potassium hydroxide, the whole filtered, and
the tartaric acid in solution separated by means of citric acid in
presence of potassium chloride. This method, which was improved
by Grosjean* and A. Borntrager,'* although in use commercially for
many years, and until recently exclusively in this country, has been largely
abandoned owing to its tediousness and also to the fact that it gives
decidedly high results in presence of impurities such as phosphates.
The method which is now in general use for the estimation of
1 Chem. Zeit. Rep., 1899, 23, 4. ^ Das Raffinieren des WeinsUins, 1894.
V- Chem. Soc, 1875, 27, 925. * //>ul, 1879, 35, 341 i 1883, 43. 33i-
^ Z. anal. Client., 1886, 25, 327 ; 1S87, 26, 699.
TOTAL TARTARIC ACID 285
the total tartaric acid is the " Goldenberg Method, 1898," and its
modification known as the " Goldenberg Method, 1907."
These methods are based in principle upon a process, apparently
due to Jules, and described in detail by the firm of Goldenberg,
Geromont & Co., which was adopted in the industry under the name
" Original Goldenberg Method." ^ This method was carried out as
follows : — The substance was boiled with an excess of potassium
carbonate, whereby the calcium was precipitated as carbonate, and
the tartaric acid converted into the normal potassium salt ; the solution
was then filtered and an aliquot portion of the filtrate precipitated by
acetic acid and alcohol, the precipitated bitartrate being washed with
alcohol and titrated. This method is subject to the following errors : —
The potassium hydrogen tartrate is not quite insoluble in the mixture
of dilute alcohol and acetic acid; on the other hand, especially in the
case of wine-lees, other acid substances (pectic material) are precipi-
tated and finally titrated as bitartrate. The results were, therefore,
uniformly considerably higher than the true tartaric acid content, and
depended on the excess of potassium carbonate employed ; further,
the solutions of bitartrate finally titrated were always highly coloured,
so that the results obtained by different analysts often differed widely,
sometimes by several per cent.
These difficulties are avoided in the " Hydrochloric Acid Method,"
also due to the firm of Goldenberg, Geromont & Co. The first form
of the method published in 1888- was defined in greater detail
in 1898.3
The ''Goldenberg Method, 1898."
This method is carried out as follows : — 6 g. of finely ground and
powdered lees are stirred into a uniform mass with 9 c.c. of dilute
hydrochloric acid (sp. gr. i-i), and allowed to stand during one hour at
the ordinary temperature, with frequent stirring. The mixture is then
diluted with an equal volume of water and again left for an hour,
stirring from time to time. The mass is now washed into a 100 c.c.
measuring flask, and the volume made up to the mark. After shaking
well, the solution is filtered through a dry filter paper into a dry vessel ;
50 c.c. of the filtrate are then measured into a beaker which is kept
covered with a clock-glass, and carefully boiled with 18 c.c. of a
potassium carbonate solution (10 c.c. = 2 grm. K.^COy) for ten minutes
until the calcium carbonate is separated in a granular form. After
washing the clock-glass with water, the contents of the beaker are
filtered and the beaker washed with boiling water until the washings
are neutral ; the calcium carbonate on the filter paper is also
thoroughly washed out with boiling water, the alkaline liquid being
1 Z. anal, Chem., 1883, 22, 270. ^ C/iet)!. ZciL, 1888, 12, 390
'^ Z. anal. Chem., 1898, 37, 312, 383.
286 TARTARIC ACID
finally transferred to a porcelain dish. The liquid is then
evaporated to about 15 c.c, and, after covering the dish with a
clock-glass, carefully mixed while hot with 3 c.c. of glacial acetic acid.
After stirring for five minutes the analysis may be completed, or, if
necessary, left for some time, even to the next day if desired. This
long standing, however, should be avoided in the case of low-grade
lees, as a slimy precipitate may separate from which it is difficult
subsequently to wash out the acetic acid completely. If, for any reason,
the analysis must be interrupted at any other point, this is best done
after measuring out the 50 c.c. of the hydrochloric acid solution.
After stirring with acetic acid, 100 c.c. of 94-96 per cent, alcohol is
added, rinsing the clock-glass therewith as it is run in ; the mixture
is then stirred continuously during another five minutes, until the
precipitate, which first separates as curds, has become finely granular-
crystalline. The precipitate of bitartrate is now immediately trans-
ferred to a conical suction-filter in the following way : — The precipitate
is first allowed to settle in the dish in the ordinary manner, and the
alcohol decanted off through the filter paper ; the precipitate is then
washed on to the paper and the dish washed out with alcohol until
there is no further acid reaction. The precipitate on the filter is also
washed with alcohol until 30 c.c. of the alcoholic filtrate mixed with
phenolphthalein shows an alkaline reaction after adding 2-3 drops of
iV/5 potassium hydroxide ; this quantity of alkali is that required to
overcome the slight acidity of the alcohol employed. Finally, the
precipitate, together with the filter paper, is transferred to a beaker, the ,
bitartrate adhering to the porcelain dish and clock-glass being also
washed in by means of boiling water, so that a total volume of from
100-120 c.c. of liquid is obtained. This is titrated with iV/2 potassium
hydroxide; Nji potassium hydroxide can be used if a burette of 10 c.c.
capacity, graduated in ^V c.c, be employed, so that accurate readings
to within -j-^ c.c. can be obtained. To recognise the end point sensitive
litmus paper, with a reddish-violet colour, is u.sed. The alkali used
must be standardised with chemically pure potassium hydrogen
tartrate, using the same litmus paper and about the same concentra-
tion of solution as in the actual analyses. The calculation is corrected
in the following way for the volume of lees-residue remaining
undissolved by hydrochloric acid in the first instance : — With a tartaric
acid content of 20 per cent., a deduction of 07 per cent, is made; and
the apparent value (20-I-;/) per cent, is counted as (20 + ;/) per cent. -
(07 + 0-02;/) per cent, tartaric acid.
In analysing tartars and tartrate of lime, 3 g. of substance is
employed, which is digested with 9 c.c. of hydrochloric acid, diluted to
100-5 c.c, and 50 c.c, of the filtrate is used for the analysis, as above.
In these cases the above correction is avoided.
TOTAL TARTARIC ACID 287
In the case of normal raw materials, not too much contaminated by
factory impurities, this method gives results corresponding with the actual
tartaric acid content. High results due to adulterants are not possible.
Experience, however, has shown that certain points were not sufficienlly
defined, considerable differences being found in the results of different
analysts, especially in the case of lees rich in calcium tartrate. The
manner in which the potassium carbonate was added to the hydro-
chloric acid solution — whether rapidly or slowly— and the time of
heating, etc., were found to affect the result. These differences are not
so pronounced when, conversely, the hydrochloric acid solution is added
slowly to the potassium carbonate. In order to obviate them the exact
details of procedure to be adopted were discussed at the International
Congresses of Applied Chemistry held at Rome in 1906, and at London
in 1909, and the following modification was agreed upon, which is, in
the main, that worked out by Messrs Ogston and Moore.^ This
modification is known as : —
The " Goldenberg Method, 1907."
This revised form oj the Goldenberg method is carried out as
follows : — 6 g. of the sample if it contains more than 45 per cent, of
tartaric acid, or 12 g. if it contains less than 45 per cent, is stirred
continuously during ten minutes with 18 c.c. of hydrochloric acid of
sp. gr. I- 10. The mass is then washed into a 200 c.c. measuring flask,
made up to the mark with distilled water, and, after shaking well, the
solution is filtered through a dry, fluted filter into a dry beaker. 100
c.c. of the filtrate is then measured out by a pipette (the volume of
which agrees exactly with the graduated flask — " standard " measuring
vessels should be used by preference) and added to 10 c.c. of a solution
of potassium carbonate containing 66 g. of the anhydrous salt per 100
c.c. (sp. gr. 1-490). The solution of the potassium carbonate is placed
in a beaker of 300 c.c. capacity, which should be covered with a clock-
glass during the addition of the lOO c.c. of acid solution. After mixing,
the solution is boiled gently for twenty minutes, until the calcium
carbonate has separated in a crystalline form. The liquid is then
washed into a 200 c.c. measuring flask, cooled, made up to the mark,
and filtered through a dry, fluted filter paper.
100 c.c. of the filtrate is then evaporated, either in a porcelain dish-
on the water-bath, or in a beaker of Jena glass, on a hot plate, until the
volume is about 15 c.c. Whilst the solution is still hot 3-5 c.c. of
glacial acetic acid is added gradually, and with constant stirring, and
1 Z. anal, Chem., 1908, 47, 57. Report of Internalional Committee on Analysis, 7th Inter-
national Congress of Applied Chemistry, London, 1909.
^ Porcelain basins having a blue ring on the inside to show the volume of 15 c.c, can be
obtained from B. W. Haldenwanger, Charlottenburg.
288 TARTARIC ACID
the stirring continued for five minutes afterwards. After standing for
ten minutes longer, lOO c.c. of 95 per cent, alcohol is added and the
mixture again stirred during five minutes. After a further ten minutes'
interval, the precipitate of bitartrate is filtered by the aid of a vacuum
pump ; for this filtration a perforated disc of lead or porcelain is used,
with a filter paper cut slightly larger than the disc. Asbestos pulp can
also be used. The precipitate is then washed with alcohol until the
washings cease to give an acid reaction, the washing being continued
until 30 c.c. of the filtrate, mixed with phenolphthalein, require exactly
the same volume of Nj^ alkali to produce redness as 30 c.c. of the
alcohol itself The filter with the precipitate is washed into a porcelain
dish with about 200 c.c. of boiling water, and then titrated with iV/S
potassium (or sodium) hydroxide solution, using sensitive litmus paper ^
as indicator (spot test).
The alkali must be standardised with chemically pure potassium
hydrogen tartrate (dried at 100) using the same litmus paper and
approximately the same concentration of solution.
As the volume of the insoluble constituents of the raw material has
not been taken into consideration the following corrections are
necessary : — It has been agreed to deduct 0-8 per cent, for raw material
yielding less than 45 per cent, of total tartaric acid, 0-3 per cent, for
raw material with 45-60 per cent, and 02 per cent, for material with
60-70 per cent. No deduction is made in the case of samples with
more than 70 per cent, of acid.
The "1907 Method" gives slightly higher results than the "1898^
Method," by an amount which varies between 02 and 0-7 per cent.
In consequence a slightly lower valuation of the raw material is
found with the new method. Both methods are in use, some dealers
preferring to use the one, some the other method. As compared with
the older Warington method, the Goldenberg 1907 method gives
results from I-5-I7 units lower; that is, a difference in the case of
lees of about 6 per cent, and in the case of tartars of 3 per cent, on the
tartaric acid present.
Several other methods have been proposed for estimating tartaric
acid, but none of these has been generally adopted. It will be
sufficient therefore to give the references.
J. Mosczenski.- — Extraction of the material with sulphuric acid, and
direct precipitation with potassium acetate.
K. Ulsch.'* — Action of the material on platinised iron powder, and
measurement of the hydrogen liberated.
H. Ley.^ — Precipitation and weighing as zinc tartrate.
' The most suitable sensitive litmus paper is that obtainable from E. Merck, Darmstadt, or
E. Dieterich, Ilelfenberg. " Z. anal. CJiem., 1900, 39, 57-
■' Z. anal. Clutn.^ 1901, 40, 614. ■• Pharm, Ztit.y 1904, p. 149.
IMPURITY RATIO 289
P. Carles.^ — Precipitation of a hydrochloric acid extract with
calcium acetate, and weighing of the separated crystals of calcium
tartrate.
The following are references to more recent methods : —
A. C. Chapman and P. Whitteridge, Analyst, 1907, 32, i63*
P. Pozzi-Escot, CoDiptes rend., 1908, 146, 103 1.
A. Kling, Comptes rend., 1910, 150, 616.
C. Beis, Bull. Soc. Chim., 1910, 7' 697.
3. Other Estimations.
The adulteration of the raw material employed in the manufacture
of tartaric acid, for example with alum, was formerly practised when
samples were examined merely by simple titration ; since the intro-
duction of the Warington and Goldenberg methods, such adulteration
is no longer met with. The addition of alum would in fact cause an
apparent loss of real tartaric acid in the Goldenberg method.
When the final mother liquors ("Old Liquors") of the tartaric acid
industry, in which impurities such as alumina, iron, and phosphoric
acid have accumulated, are precipitated in the form of calcium tartrate,
the harmful impurities tend to separate also. The working up of these
old liquors is attended with difficulties. It, therefore, may happen that
a parcel of raw material is contaminated with such a product. Such
adulteration, which can in many cases be detected by smell, is also
recognised by estimating the ratio of phosphoric acid, alumina, and iron
to the total tartaric acid present {Inipiirity Ratio). For this determina-
tion a portion of the sample is ignited ; if much calcium tartrate be
present, it is advisable to moisten the material with a concentrated
sugar solution in order to avoid loss. The ash is extracted with
hydrochloric acid, and in the acid extract phosphoric acid, alumina, and
ferric oxide are estimated ; it is generally sufficient to precipitate the
three substances together by adding ammonia, and to weigh the whole
after ignition. The amount found is calculated as a percentage of the
total tartaric acid present.
To estimate the proportion of iron the ignited material is dissolved
by boiling with dilute sulphuric acid, cooled, reduced with iron-free zinc,
and the solution titrated with iV/io potassium permanganate.
The "Impurity Ratio" determined in this way is, in general, for
tartars, less than i, for lees from 1-2, and only seldom in the latter case
reaches 5-6; in impure factory products the ratio reaches 10-20.
By slow or unsatisfactory drying, slimy substances may be formed
in lees, owing to the growth of moulds or bacteria which render the
subsequent working up of the products very inconvenient. It is,
^ Les Derives Tartriques, I903, p. 105.
Ill T
290 TARTARIC ACID
therefore, necessar\' to ascertain in many cases whether a material
contains an undesirable quantity of such fermentation organisms. This
is done as follows, according to the method given by H. Rasch^ : — 40 g.
of lees are mixed with 50 c.c. of 10 per cent, calcium chloride solution
in a beaker of 400 c.c. capacity, and exactly neutralised with milk of
lime in the cold. The beaker is filled up with water, and the mixture
allowed to stand for twenty-four hours at a temperature of 35". W'ith
good, well-dried lees no visible fermentation should begin during this
interval ; at most, a few bubbles of carbon dioxide should be evolved.
The auxiliary materials of the industry, such as sulphuric acid, lime,
chalk in the case of tartaric acid, sodium and potassium carbonates
in the manufacture of tartaric acid salts, must naturally be as free as
possible from alumina, iron, and phosphoric acid. A small amount of
magnesia in the lime or chalk is not prejudicial in the case of tartaric
acid (as it is in the case of citric acid), because magnesium tartrate is
not very sparingly soluble.
II. Control of Working Conditions.
The impurities which accumulate in the works liquors, which consist
mainly of phosphoric acid, alumina, and iron, are of importance as
regards the estimation of the contained tartaric acid. It has been
shown by Lampert^ that if litmus be used as the indicator in the
titration of the tartaric acid a certain amount, which is recoverable in
the actual working, escapes estimation. Rasch^ has therefore recom-
mended the use of phenolphthalein in dealing with works liquors, with
which fairly accurate results can be obtained even though the end-
points are by no means sharp in the case of the cruder liquors.
In the laboratory of Messrs C. H. Boehringer, it is considered
preferable first to remove the iron, the principal impurity, by the
following method : — 50 c.c. of the liquor are measured into a beaker
and titrated with a standard solution of potassium ferrocyanide, using
copper sulphate as outside indicator in the usual way, until a slight
brown coloration is shown. The number of cubic centimetres of ferro-
cyanide used gives a measure of the iron present. 50 c.c. of the
original liquor are then measured into a 100 c.c. flask, mixed with the
volume of potassium ferrocyanide found in the previous experiment to
be necessary, made up to the 100 c.c, filtered, and the tartaric acid
estimated in a measured volume of the filtrate. The estimation of the
iron in the works liquors is a useful means of controlling the purity of
these liquors, as the other impurities stand in a nearly constant ratio to
the content of iron.
^ Fabrikation der IVeinsautr, p. 44.
'■* C/iem. Zei/., 1800, 14, 903 ; c/. also Ordonneau, Bu//. Soc. Chim., 1910, 7i I034»
' Fabrikation der Wemst/ure, p. 22.
CONTROL OF WORKING CONDITIONS 291
The determinations are carried out as follows :—
Calcium Tartrate.— 6 g. of substance are boiled with lo cc of
potassium carbonate solution (500 g. per litre) and about 150 cc* of
water for ten minutes, the solution made up to 200 cc. in a measuring
flask, and filtered. 50 cc. of the filtrate are evaporated to about 15 cc
and precipitated with 3 cc of glacial acetic acid and 100 cc of alcohol'
The washed precipitate is then titrated with N/io potassium hydroxide
to obtain the percentage of tartaric acid, using phenolphthalein as
indicator.
Tartaric Acid Liquors.-2o cc of the weak liquor (or 10 cc of
concentrated liquors), freed from iron, are boiled with 40 cc' of
potassium carbonate solution of the above concentration, the soluiion
made up to 200 cc and filtered; 10 cc of the filtrate are then
precipitated hot with 3 c.c of glacial acetic acid and 100 cc of alcohol
The number of cubic centimetres of N/io alkali used in the titration!
multiplied by 30 gives grams tartaric acid per litre. Phenolphthalein
is used as the indicator.
Old Liquors.-20 cc of the old liquor, freed from iron, are boiled
with 60 ^;^- of potassium carbonate solution, made up to 200 cc. and
filtered. Of the filtrate, 20 cc are precipitated with 5 cc of glacial
acetic acid and 100 cc of alcohol. The number of cubic centimetres of
^/o alkali used in the titration, multiplied by 15, gives the grams of
tartaric acid per litre.
^Vaste Products-Lees Residue and Gypsum.-3oo g of the
sample are heated to boiling in a porcelain dish with 2c cc of
concentrated hydrochloric acid and 500 cc of water, stirring well ' A
part_ of the liquid is filtered, and 50 cc, without evaporation.' are
precipitated with 3 cc of glacial acetic acid and 130 cc of alcohol
Each 5 cc of A/ 10 alkali used in titration corresponds with approxi-
mately o-i per cent, of tartaric acid in the residue
Washings or "Runnings." (obtained from the precipitation of
calcium tartrate).-200 cc of the runnings are evaporated to about
50 cc, boiled for several minutes with 10 cc of potassium carbonate
solution, and made up to 100 cc ; 60 cc of the filtrate are then mixed
in a measuring cylinder with 10 cc of hydrochloric acid of sp gr i-io
and made up with alcohol to a total volume of 180 cc The mixture is
shaken and filtered immediately, and, without delay, to 150 cc of the
filtrate is added successively 10 cc of potassium carbonate solution
(500 g. per litre), 5 cc of glacial acetic acid and 100 cc of alcohol
The mixture is well stirred, left till the following day, and the precipitate
filtered off, washed, and titrated. 10 cc of N/io potassium hydroxide
correspond with 1.50 g. of tartaric acid per litre. Phenolphthalein is
used as the indicator in the titration.
Free Sulphuric Acid in Tartaric Acid Liquors.-2o cc of the
292 TARTARIC ACID
liquor are made up to 200 c.c. with alcohol in a measuring flask, left to
settle overnight, and filtered ; from 100 c.c of the filtrate the alcohol is
completely evaporated on the water-bath, the residue diluted with
water, and the sulphuric acid precipitated by barium chloride, and the
precipitate collected and weighed as usual.
For the approximate determination of the sulphuric acid it is
sufficient to titrate 10 c.c. of the alcoholic solution with .\' 5 barium
chloride solution until it ceases to produce a precipitate.
Harmful Impurities (''Impurity Ratio")- — Alumina, iron, and
phosphoric acid are determined in the same manner as in raw materials
(p, 289) on the ash obtained from a known volume of the liquor (20-100
c.c. according to the grade).
The proportion of the ash which is soluble in water is often a useful
guide in investigating works liquors, as well as the proportion of
potassium carbonate present in this soluble extract. To estimate the
potassium carbonate in the ash the quickest and best method is to add
from 10-20 c.c. of 5 per cent, barium hydroxide solution to the ash,
evaporate to dryness, ignite well, and then extract and filter. To the
filtrate (and washings) 5 c.c of perchloric acid (sp. gr. 1-12) are added,
and the liquid is evaporated until fumes of perchloric acid are given off
strongly. The residue is taken up with 95-96 per cent, alcohol, the
precipitate of potassium perchlorate collected on a Gooch crucible or
Soxhlet tube, washed first with alcohol containing 0-2 per cent, of
perchloric acid, finally with a little pure 95 per cent, alcohol, and
weighed.! (W. A. D.)
III. Finished Products.
Tartaric Acid — Dextrorotatory tartaric acid is the only form made
commercially. It is used as a mordant in dyeing and as a resist and
discharge in printing ; also in medicine and photography and on a large
scale in the manufacture of baking-powders, effervescent salines, fruit
preserves, aerated waters, bon-bons, etc. The acid must be colourless,
without smell, and, when crystalline, must consist of large, well-formed
transparent crystals. A large quantity of tartaric acid, however, is used
in the form of " smalls," that is, consisting of small crystals. Tartaric
acid powder must not cake together and should not contain traces of
free sulphuric acid, although a trace of sulphate (calcium sulphate)
is riot prejudicial. Larger quantities of calcium sulphate, however, tend
to make tartaric acid hygroscopic ; it is generally supposed that this is
due to the action of tartaric acid on the sulphate giving rise to free
sulphuric acid.
As/i. — The limit for ash in tartaric acid crystal or powder used for
' Cf. Section on " Potassium Salts," Vol. I., Part II., p. 530, and W. A. Davis, y. Agric. Set,,
1912,5, 56.
FINISHED PRODUCTS 293
pharmaceutical purposes in Great Britain in past years has been 0-05
per cent. The Committee of Reference to the Pharmacopoeia Com-
mittee (1908) has, however, recommended that this limit should be
raised to o-i per cent, as there is difficulty in obtaining tartaric acid
with ash below 0-05 per cent.
Arsenic is tested for by the following method recommended by the
Royal Commission on arsenical poisoning (1903). From 1-5 g. of
tartaric acid is used, with arsenic-free zinc and hydrochloric acid. The
limit of arsenic adopted is y^^ gr. per lb. (1-4 parts AS2O3 per million,
or 0-00014 per cent). There is no difficulty in obtaining tartaric acid
in which arsenic falls considerably below this figure.^
Lead. — The limit of lead generally adopted in commerce in this
country is 20 parts per million (0-002 per cent), as recommended by
M'Fadden.2 Many methods have been suggested for making the test,
of which the following are probably the most reliable.
Method I. — Based on C. A. Hill's method,^ which is, like the following
one, a modification of Warington's original colorimetric method.*
A standard lead solution is prepared containing 5 parts of lead per
million, by dissolving, pure metallic lead in a minimum quantity of
nitric acid (equal parts of concentrated acid and water) and suitably
diluting ; it is best to prepare a standard stock solution of lead, con-
taining say I g. of lead per litre, and then, when required, to dilute this
for use to the above concentration. The standard solution may also
be prepared from pure lead nitrate or from crystalline lead acetate.
For the test, 7 g. of the sample are weighed out, and a separate
portion of 2 g. for the colorimetric comparison. Each portion is
dissolved in about 10-15 c.c. of water, and to the 2 g. portion is added
as many cubic centimetres of the standard lead solution as there are
suspected to be parts per million of lead in the tartaric acid tested.
Thus to compare with 15 parts of lead per million, 15 c.c. of the
standard lead solution are used. To each solution is then added
1-2 c.c. of 10 per cent, potassium cyanide solution and 13 c.c. of
ammonia of sp. gr. o-88o, and the solutions are boiled for half a minute
or longer so as to get both colourless if possible. They are next
poured into two 50 c.c. Nessler cylinders of clear white glass and diluted
to an equal volume (50 c.c), any difference of colour being corrected if
necessary by the addition of a drop or two of a very dilute solution of
caramel. To each solution is then added 1-2 drops of a freshly
prepared colourless ammonium sulphide solution (obtained by saturating
ammonia (sp. gr. o-88o), diluted with an equal volume of water, with
hydrogen sulphide gas, carefully washed by passing through water).
^ C^ A. W. M'Fadden, Local Government Board Report, Inspector of Foods, No. 2, 1907.
'^ Cf. Tatlock and Thomson, Analyst, 1908, 33, 173 ; T. F. Harvey and J. M. Wilkie, Chem.
and Drug., 1909, 75, 92.
2 Chem, and Drug., 1905, 66, 388. * J. Soc. Chem. Ind., 1893, 12, 97.
294 TARTARIC ACID
The colour of the two solutions is compared by examining them, placed
on a sheet of white paper, in a good light.
Generally it is sufficient to make sure that the quantity of lead
present is less than 20 parts per million, but if it is necessary to
ascertain the exact quantity, comparisons are made with suitable pro-
portions of lead (5, 10, 15, etc. c.c. of the dilute standard lead solution).
Method II. — J. M. Wilkie's Method} — 7 g. of the sample are taken
for the test, and 2 g. for the colorimetric comparison, to which the
standard lead solution is added. Each is dissolved in about 35 c.c. of
hot water, allowed to cool, a few drops of N\\o sodium thiosulphate
solution added, and heated to incipient boiling, when the flame is
removed. Any ferric iron present is rapidly reduced on cooling.
When the solution is water-white, potassium cyanide (1-2 c.c. of
10 per cent solution) is added, and then ammonia until the solution
just smells of it (excess should be avoided). After diluting in Nessler
cylinders, 2 drops of colourless ammonium sulphide solution are added,
and the colorations compared as described above.
In Germany, the following test, due to W. Klapproth, is used. 20 g.
of the sample are ignited with 0-04 g. of calcium carbonate in a porcelain
crucible. The small residue (which contains all the lead) is dissolved in
a few drops of nitric acid, 2 or 3 drops of sulphuric acid added, and the
mixture heated to expel the nitric acid. The residue, consisting of lead
and calcium sulphates, is dissolved in ammonium acetate solution, and
the solution filtered from insoluble matter (ferric oxide).
To the clear solution hydrogen sulphide water is added, and the
resulting brown coloration compared with that of a solution of
ammonium acetate in water, containing a known quantity of lead to
which hydrogen sulphide water has been added under similar conditions.
To make certain that the brown coloration is due to lead and not to
copper, some potassium cyanide solution is added, which destro)'S the
brown colour due to copper, but has no effect on that due to lead.
OtJicr Tests. — Quantities of 3 g. of the acid are dissolved in water,
and submitted to the following tests.
The solution of the pure acid should give no turbidity with barium
chloride ; nor, after the addition of nitric acid, with silver nitrate. The
solution rendered alkaline with ammonia should give no precipitate
with ammonium oxalate. The acid should require for titration the
calculated quantity of normal alkali, which has been standardised by
pure potassium hydrogen tartrate, using phenolphthalein as indicator,
under exactly the same conditions of concentration.
Cream of Tartar. — This occurs in commerce in different grades of
purity, containing varying proportions of calcium tartrate or calcium
sulphate. The usual qualities are 95 per cent., 98 per cent., and 99-100
* J. Soc. Chem. Ind., 1908, 28, 636 ; Harvey and Wilkie, Chem. and Drug., 1909, 75, 92.
FINISHED PRODUCTS 295
per cent. It is employed in dyeing as a mordant, for soupling silk,
in food materials such as baking-powders, and in medicine. The
tartaric acid and the contained calcium are determined.
The total tartaric acid is best estimated by the Goldenberg method.
The Acidity, on which the percentage of cream of tartar is generally
gauged, is ascertained by titrating 5 g. of the sample with TV/i potassium
hydroxide, which has been standardised by titration with 5 g. of pure
recrystaliised 100 per cent, cream of tartar, dried at 100°, under
exactly the same conditions of concentration, using phenolphthalein as
indicator. The titration can also be made with 2 g. of the cream of
tartar with iV/5 alkali, standarised under the same conditions as the
actual test. This observance of exactly similar concentrations for
standardisation and the actual test is necessary if exact results are to
be obtained, owing to the hydrolysis of the neutral tartrate by water,
which causes more alkali to be required (o- 1-0-3 c.c) in dilute solution
than in concentrated solution.
To estimate tartaric acid rapidly in cream of tartar, baking-powders,
etc., F. W. Richardson and J. C. Gregory,^ and R. O. Brooks- have
advocated a polarimetric method.
The requirements as regards Arsenic and Lead 2.xq the same as for
tartaric acid.
Rochelle Salt (Sodium potassium tartrate) is employed in
medicine, in silvering glass, and in electro-plating. The salt should
dissolve in water to a clear solution, and the crystals also should be
clear, where not rendered white on the surface by friction. The tests
for purity are the same as for tartaric acid.
Tartar Emetic (Antimony! potassium tartrate). — This is used as a
fixative for tannin mordants in dyeing, and to a limited extent in
medicine. For analysis, the salt is dissolved in 300 parts of warm water,
the antimony precipitated by hydrogen sulphide, finally with addition
of a little hydrochloric acid, and the liquid, separated by filtration from
the antimony sulphide, used for the estimation of the tartaric acid. The
antimony content is controlled by titration with iodine solution by
Mohr's method (see the section on "Metals other than Iron," Vol. II.,
Part I., p. 282).
Neutral Potassium Tartrate, Borax Tartar, and Iron Tartrate
find some application in medicine.
Literature.
Carles, P. — Les Derives Taririques dit Vz'n, 3rd edition, 1903.
ClAPETTl, G. — Llndustria Tartarica, published by Hoepli, Milan, 1907.
Rasch, H. — Die Fabrikation der Weinsdure, 1897.
ROUX, U. — La Grande Industrie des Acides Organiques, Bitartrate de Potasse,
Acide Tartrique, Acide Citrique, 191 2.
^ J. Soc, Chem. Ind., 1903, 22, 405. ^ y_ Amer, Chem. Soc, 1904, 26, 813.
CITRIC ACID
By WiLHELM Klapproth, Dr Ing., Chemist to Messrs C. H. Boehringer, Nieder-
Ingelheim, on Rhine. English translation revised by W. A. Davis, B.Sc,
Rothamsted Experimental Station.
I. Raw Materials.
Citric acid is obtained from the juice of fruits of several species of
Citrus. Besides the juice of the lemon [Citrus inedica), that of the
Bergamot {Citrus Bergamid) and of several West Indian species of
Citrus, especially the Lime {Citrus Linionuvi) are also worked. Small
quantities of citric acid were obtained experimentally some years back
by the fermentation of sugar by the organism discovered by C. Wehmer.^
The lemon juice is in general prepared at the place of production,
by pressing the fruit, and is then subjected to a short fermentation to
remove protein matter. The juice cleared in this way contains from
45-75 &• of citric acid per litre, and either comes direct into commerce^
or is further concentrated by boiling in open copper vessels. The price
for the juice per "pipe" is calculated on the basis of 64 oz. citric acid
per Imperial gallon. As i pipe =108 Imperial gallons or 490 litres
(1 gallon = 4-536 litres), and i oz. = 28-35 g., the "pipe" of juice of the
above concentration contains 196 kg. of citric acid. Market prices are
referred to this unit. The concentrated bergamot juice is mostly sold
on the basis of 48 oz. per Imperial gallon. For factory purposes it is
often more useful to express the concentrations in grams per litre ; the
above strengths of 64 and 48 oz. per gallon then become 400 g. and
300 g. of citric acid per litre.
Formerly such juice served exclusively as the raw material in the
manufacture of citric acid. Now, however, most of the juice is con-
verted into calcium citrate at the place of production, and this is to-day
the principal raw material. Raw lime juice is, however, still an
important article.
All analyses are expressed in terms of the tribasic citric acid with
I mol. of water of crystallisation, i.e., C^HgO^+HoO, the molecular
weight of which = 2 10.
' Beitti'ige zur Kenntnis einhewiischer Pihe, !., 1893 ; P'abriques de produits chimiques de Thairn
et Mulhouse, Ger. Pat. 72957, 1893 ; Eng. Pat., 5620, 1893,/. Sec. Ckem. Ivd., 1894, 13, 275.
296
RAW MATERIALS 297
The composition and complete analysis of raw juices have been
studied by R. Warington ^ and more recently by K. Farnsteiner.^
The dark brown, concentrated juice was formerly valued either on
its specific gravity, or on its acidity as determined by simple titration.
Adulteration by salts (evaporated sea-water) and acids {e.g. sulphuric
acid) was therefore common. The present method of analysis used in
commerce was introduced by Warington, and is based on the insolubility
of calcium citrate. It must be remembered, however, that calcium
citrate is insoluble only in Jiot water, whilst it is not precipitated from a
cold solution and even redissolves to a considerable extent in cold water.
Warington's method is now generally carried out as follows in this
country and in Sicily (Ogston and Moore).
Calcium Citrate.
4 g. of the citrate is boiled with 30 c.c. of 2 A^-hydrochloric acid in a
100 c.c. standard measuring flask for ten minutes, the solution being
then cooled and made up to the mark with water. It is then shaken
and filtered through a dry filter paper, 50 c.c. of the filtrate being
measured by a standard pipette into a beaker of 300 c.c. capacity, and
exactly neutralised with dilute sodium hydroxide free from carbonate,
using phenolphthalein as indicator. The solution is next made slightly
acid by the addition of 3 or 4 drops of TV-hydrochloric acid, 2 c.c. of
a 45 per cent, solution of calcium chloride added, the liquid raised to
the boil and kept boiling for fifteen minutes ; to avoid bumping it is
necessary to stir the liquid well until actually boiling, after which it can
safely be left. The hot liquid is filtered and the precipitate on the
filter paper washed with boiling water six times. The filtrate and
washings are then made just alkaline by adding a drop or two of dilute
ammonia, and boiled down to about 15 c.c. The precipitate which
forms is collected on a small filter paper and washed with boiling water
six times, using a very small quantity of water for each washing. The
filtrate and washings are treated with a drop of ammonia, if they have
become acid, and are boiled down to about 10 c.c, but as a rule no
further precipitate will be obtained whilst the liquid is hot ; any
precipitate which forms on cooling can be neglected.
The filter papers with their precipitates are dried at 100° and
burnt together in a platinum dish with a cover. The flame should be
kept low until the whole is charred, and then gradually raised until the
ash is white. It is then carefully treated with 30 c.c. of A'-hydrochloric
acid, the whole boiled until all is dissolved and all carbon dioxide
expelled, and the resulting solution titrated back with A75 or Njz
sodium hydroxide, using phenolphthalein as indicator.
The sodium hydroxide is standardised by pure potassium hydrogen
^ J. Chem. Soc, 1875, 28, 925. ^ ^^ [Jnters. Nahr, u. Genussm., 1903, 6, I.
298 CITRIC ACID
tartrate, and the TV/ 1 hydrochloric acid by the alkali; phenolphthalein
is used as indicator.
The number of cubic centimetres of iV/i HCl used for the neutralisa-
tion of the ash x 0-070 gives the weight of citric acid in the portion
tested.
An almost identical method has been described by L. and J. Gadais.^
If the citrate contains much sulphate it is advisable to ash at as
low a temperature as possible, preferably with an alcohol flame. Before
dissolving in hydrochloric acid, the ash should be treated with 10 c.c.
of hydrogen peroxide. [If, as is usual, the hydrogen peroxide contains
free acid, allowance must of course be made for it.]
Lime Juice, Lemon Juice, and Factory Citric Acid Liquors,
The analysis of these materials is conducted as follows : — From
15-20 c.c. of unconcentrated juice, or an amount corresponding with
3 c.c. of concentrated juice (40 g. per 100 c.c), previously diluted to
facilitate exact measurement, are exactly neutralised with pure
potassium hydroxide (iV/S). The liquid, having a volume of about
50 c.c, is heated to boiling, mixed with a slight excess of concentrated
calcium chloride solution, and kept at a gentle boil for half an hour.
The precipitate is filtered off immediately while hot, washed with
boiling water six times, and the mother liquor and washings again
evaporated and worked up as described above under calcium citrate.
The whole of the calcium citrate collected is then dissolved in 30 c.c.
of iV/i hydrochloric acid and the excess of acid estimated as above.
In dealing with the cruder factory liquors three or four evaporations
are generally necessary to separate all the calcium citrate.
The above methods are not entirely free from error,^ but have not
yet been replaced by better. Incorrect results are obtained when the
calcium citrate or juice contains other acids which yield sparingly
soluble calcium salts. The presence of oxalic acid or of tartaric acid
may be detected by the fact that the cold, neutralised solution gives a
precipitate in the cold with calcium chloride.
C. Ulpiani and A. Parozzani '■'' have described a method of analysis
which, according to Klapproth, gives satisfactory results for citric acid
even in presence of other organic acids. This method depends upon
the fact that citric acid, in presence of a sufficient quantity of calcium
chloride, is precipitated by sodium hydroxide in the cold when the whole
of the acid is saturated, and in the hot solution when one-third of the
acid is saturated. M. Spica* has described a method which consists in
measuring the carbon monoxide which is evolved on gently warming
' Bull. Soc. Chun., 1 909 [iv.], 5, 287. ^ Qy q, von Spindler, Chem. Zeit., 1903, 27, 1263.
^ Atti. R. Accad, Lined, 1906 [v.], 15, ii., 517.
* Chem. Zeit., 1910, 34, 1141 ; cf. Barboni, Ann. Lah, Cenlr. deUe GabelU, 1912, p. 311.
RAW MATERIALS 299
the sample with concentrated sulphuric acid. Neither of these methods
has been adopted in commerce.
The presence of sulphuric acid, which can give rise to error owing
to the reduction of calcium sulphate to sulphide during ignition, may be
recognised in the juice or liquors, after adding hydrochloric acid, by
means of barium chloride. If only small quantities of sulphuric acid
or sulphates are present, the above methods can be used ; in presence
of larger quantities, however, the use of hydrogen peroxide (see above)
is necessary, or the following method proposed by J. Creuse ^ may be
used : —
20 c.c. of the unconcentrated or 3 c.c. of the concentrated juice or
liquor is accurately neutralised with pure (about iV/5) potassium
hydroxide and then evaporated to dryness on the water-bath. The
residue is taken up with from 20-30 .c.c. of 63 per cent, alcohol, and the
potassium citrate filtered from the undissolved salts (potassium sulphate,
etc.), the residue being washed with a little 93 per cent, alcohol. To
the solution, which, if necessary, is neutralised with a drop of dilute
acetic acid or ammonia, a neutral alcoholic solution of barium acetate is
added and double the volume of 95 per cent, alcohol, the mixture
vigorously stirred and left to the following day. The barium citrate
precipitate, (CgH507)2Ba3, is then filtered off and washed with 6^ per
cent, alcohol; the barium is estimated in the precipitate, after ignition,
either by precipitation as barium sulphate or by dissolving it in
iV/5 hydrochloric acid and titrating back the excess of acid with alkali.
As the precipitation of barium citrate presents certain difficulties, it
is preferable, after the removal of the potassium sulphate by alcohol, to
evaporate the latter, take up with a little water and precipitate with
calcium chloride, subsequently igniting the calcium citrate and dissolving
it in 30 c.c. of N/i hydrochloric acid as in Warington's method. (W.
A. D.)
To estimate Free lime or Calcium carbonate in calcium citrate, 5 g. of
the sample is dissolved in a known quantity of standard hydrochloric
acid (A^/i or A^/2), kept gently boiling, and when cold the solution is
titrated back with alkali hydroxide in the usual manner. Each cubic
centimetre of normal acid neutralised by the sample corresponds with
0-050 g. CaCOg in the portion taken.
II. Control of Working Conditions.
Although phosphoric acid, alumina, and iron are more readily
removed from citric acid than from tartaric acid liquors, it is necessary,
in order to avoid losses of citric acid, to see that the auxiliary materials
as well as raw material are as free as possible from these substances.
1 Chem. News^ 1872, 26, 50.
300 CITRIC ACID
The "impurity ratio" is determined as in the case of tartaric acid
(see p. 289). Chalk and lime must be free from magnesia in treating
juice, etc., otherwise not only is there loss of citric acid in the precipita-
tion of the calcium citrate, but the citric acid liquors obtained from the
latter will contain magnesium sulphate, which leads to subsequent loss.
Citric acid in the liquors is estimated by the methods given under I.
Free sulphuric acid is estimated as in tartaric acid liquors (p. 291).
III. Final Products.
Citric acid is used in dyeing and textile printing, and very largely
for consumption in effervescent salines, lemonades, fruit essences,
marmalades, bonbons, etc. On account of its pleasant, acid taste, it is
particularly useful for the latter purposes, and it is also used in cake
making. It is employed in medicine as a preventive of scurvy,
gout, etc.
In view of differences in the amount of water of crystallisation
contained by the acid, a titration of the acid is a useful test.
To detect and estimate Oxalic Acid the insolubility of calcium
oxalate in cold solution is utilised ; calcium citrate is not precipitated in
the cold.
To separate and estimate Tartaric Acid the insolubility of potassium
hydrogen tartrate in alcohol is made use of, as in the Goldenberg
method. (See p. 287.)
For detecting small quantities of tartaric acid in citric acid O. von
Spindler utilises a colour reaction which is shown on precipitating.
citric acid solutions containing tartaric acid with a hot solution of
mercuric oxysulphate mixed with potassium bichromate (Denige's test).
A test proposed by P. Pusch consists in heating the acid with
sulphuric acid for thirty seconds ; J. R. Will ^ has prepared a Table
showing the different colorations produced by differing proportions of
tartaric acid.
Lead, Arsenic, and As/i are tested for as under tartaric acid, the limit-
ing quantities allowed being the same as in the case of tartaric acid. (See
p. 293.) It is usual, however, in commerce to require a higher degree
of freedom from lead than in the case of tartaric acid ; the amount
present seldom exceeds 10 parts per million. Arsenic is generally
entirely absent.
Literature.
Hallerb.\CH, W. — Die Citronensiiure unci thre Derivate, 191 1.
ROUX, \2.—La Grande Industrie des Acides Organiques, Bitartrate de Potasse, Acide
Tartrique, Acide Citrique, 191 2.
' Chem. Zeit., 1904, 28, 1 5, I48.
ORGANIC PREPARATIONS
By J. Messner, Ph.D., Messrs E. Merck & Co., Darmstadt. English translation
revised by CHARLES A. Keane, D.Sc, Ph.D.
Acetaldehyde.
CH3 . COH. Molec. wt. 44-03.
Acetaldehyde is a colourless, mobile, inflammable liquid. Sp. gr. 0-79;
boiling point 2i°-22°. The purest commercial product (aldehyde absolu-
tus) contains 95-98 per cent, of aldehyde, " aldehyde concentratissimus "
about 80 per cent, and " aldehyde concentratus " about 60 per cent.
Acetaldehyde is miscible with water, alcohol, and ether in all
proportions ; also with ammonia when a considerable evolution of heat
occurs. A yellowish-brown opalescence is produced on the addition of
sodium hydroxide ; ammoniacal silver solution is reduced on warming.
An intense blue coloration is produced on adding a few drops of
acetaldehyde to 10 c.c. of sodium nitroprusside solution mixed with
2-3 drops of piperidine ; formaldehyde does not give this reaction.^
Tests for Impurities.
Inorganic Matter. — 50 c.c. of the aldehyde should not leave more
than 5 mg. of residue upon evaporation on the water-bath.
Metals. — Aldehyde should be neither coloured nor rendered turbid
by sulphuretted hydrogen water or by the subsequent addition of
ammonia till alkaline.
Hydrochloric acid. Chlorides. — No immediate change should take
place on addition of silver nitrate solution.
Acetic Acid. — On addition of 2 c.c. of N\i sodium hydroxide solution
to 20 c.c. of aldehyde in 100 c.c. of water, the solution should be coloured
red on addition of phenolphthalein. A good sample of aldehyde should
not contain more than 06 g. of acetic acid in 100 c.c.
Quantitative Estimation.
The following method of estimation is due to R. Bourcart.^ The
^ For colour reactions of aldehyde see Z. anal. Chem.^ 1893, 32, 347 ; 1898, 37, 47 ; also
Merck's Reagenzien-Verzeichniss, 1908, p. 289.
- Bull. Soc. Ind. Mulkouse, 1889, 59, 558 ; /. Soc. Chem. hid., 1 890, 9, 557.
301
302 ORGANIC PREPARATIONS
following solutions are prepared: — Potassium bichromate i:ioo;
sulphuric acid lo per cent, by volume ; potassium iodide i : lo ; starch
solution, and sodium thiosulphate solution of such a strength that i c.c.
exactly corresponds to i c.c. of the above bichromate solution when
titrated against it.
To carry out the determination lo c.c. of the sample is made up to
I litre with water, and lo c.c. of the aldehyde solution placed in a well-
fitted 100-125 c.c. pressure flask. To this solution 50 c.c. of the
bichromate solution and 20 c.c. of the sulphuric acid are added, the
flask closed and heated for three hours in a boiling water-bath.
After cooling, the contents of the flask are washed out into a beaker,
and sufficient potassium iodide solution added to produce a clear, brown
solution, which is then titrated back with the thiosulphate. By the
oxidation of aldehyde by means of chromic acid acetic acid is formed,
I mol. of aldehyde requiring ^ of a molecule of bichromate, or
I mol. of bichromate oxidises 3 mols. of aldehyde. i c.c. of
bichromate used up corresponds, therefore, to 0-004485 g. of aldehyde.
In order to arrive at the percentage content of the aldehyde under
examination, the number of cubic centimetres of bichromate solution
used up is multiplied by 4485, provided that the above quantities
have been worked with.
This method is not applicable if the aldehyde contains alcohol, which
is always the case with the poorer qualities. The following method is
then preferable: — A 125 c.c. pressure flask is taken, in which are placed
30 c.c. of water, 20 c.c. of ammonia (sp. gr. 0-91), 25 c.c. of Nji silver,
nitrate solution, and 25 c.c. of a freshly made solution of 2 c.c. of aldehyde
in 100 c.c. of water. After closing the flask securely, it is heated for
about eight hours in a boiling water-bath, allowed to cool, and the product
of the reaction washed out into a 250 c.c. measuring flask which is
finally filled up to the mark with water. After shaking well, the
contents of the flask are allowed to settle, and 50 c.c. of the clear
solution titrated with Nj 10 ammonium thiocyanate solution after
acidifying with nitric acid and the addition of some iron alum solution
as indicator. The quantity of silver solution decomposed by the
aldehyde is thus determined, i c.c. Nji silver nitrate solution corre-
sponds to 0-022016 g. aldehyde.
The following method of analysis, due to A. Seyewetz and J. Bardin,^
is applicable in the presence of alcohol, acetal, and paraldehyde. A
few drops of phenolphthalein solution are added to a 10 per cent,
solution of anhydrous sodium sulphite, which is then neutralised with
sulphuric acid. To 40 c.c. of the neutral solution, which is cooled to
4° or 5", 10 c.c. of a solution of acetaldehyde diluted to 7-8 per cent.
is added, and the solution titrated with Nji sulphuric acid till colour-
1 Bull. Soc. Chim.^ 1905 [iii.], 33, icoo ; J. Soc. C/iem, Ind., 1906, 25, 202.
ACETANILIDE 303
less. The content of aldehyde is calculated fronn the quantity of acid
required for the titration according to the equation : —
2Na.S03+H.3SO, + 2CH3COH = (xXaHSOg+CH^. COH)2+Na,SO,.
The following method is especially recommended : — About 20 c.c.
of well-cooled water are placed in a 100 c.c. measuring flask, the
whole tared on the balance and about 5 g. of acetaldehyde (accurately
weighed) added. The flask is filled up to the mark with water,
shaken, and 10 c.c. of the mixture transferred to a 500 c.c. stoppered
flask containing about 350 c.c. of water and 30 c.c, ofiV/i potassium
hydroxide solution. After the addition of 10 c.c. of a 30 per cent,
hydrogen peroxide solution (perhydrol) and thoroughly well shaking,
the contents of the flask are allowed to stand overnight and then
titrated with Nji hydrochloric acid, using phenolphthalein as indicator.
In addition, the acidity of the acetaldehyde must be determined and
allowed for. For this purpose 10 g, of acetaldehyde are run into 50
c.c. of water and titrated with Nji potassium hydroxide, i c.c. of
potassium hydroxide corresponds to 0-04403 g. of acetaldehyde.
Acetanilide.
CgHs . NH . COCH3. Molec. wt. 135-08.
Acetanilide crystallises in colourless glistening plates which dissolve
in 230 parts of cold and in about 22 parts of boiling water, in 3-5 parts
of alcohol, and readily in ether and chloroform ; all the solutions have a
neutral reaction. It has no smell and a slight burning taste. Acetani-
lide melts at 11 3''-! 14° and boils at 295^
When heated with potassium hydroxide and a few drops of chloro-
form, acetanilide immediately gives the smell of isonitrile. When o-i g.
of acetanilide are gently boiled for about half a minute with 2 c.c. of
hydrochloric acid and 2 c.c. of a 5 per cent, aqueous solution of phenol,
and sufficient calcium hypochlorite solution added, a reddish -violet
turbidity is produced which changes to an indigo-blue solution on the
addition of excess of ammonia.^
Tests for Impurities.
Inorganic Matter. — i g. of acetanilide should, on heating, not leave
more than 0-5 mg. of residue.
Foreign Organic Matter. — o-2 g. of acetanilide should dissolve to a
colourless solution on shaking with 2 c.c. of sulphuric acid. This solu-
tion should not turn yellow on the addition of nitric acid (Phenacetine),
^ For other identifying reactions for acetanilide, cf. Z, aiial. C/iem., 1888, 27, 666 ; 1889,
28, 103, 354, 709, 711 ; Pharm. Zentralb.^ 30, 241, 603 ; 32, 41 ; Pharm, Zeit., 1898, p. 546 ;
Merck's Reag.-Verz.^ 1908, p. 289,
304 ORGANIC PREPARATIONS
The cold, saturated, aqueous solution of acetanilide should not be
coloured by the addition of ferric chloride solution (aniline salts give a
dirty green, antipyrine a red, salipyrine a violet, and thalline a green
coloration).
Free Aui/ine, Dust, Resinous Matter, and Acet-toltdde ma}- be
recognised in the following manner: — A boiling solution of i g. of
acetanilide in 30 c.c. of water, to which is added a drop of potassium
permanganate solution (i : 1000), should retain the rose coloration for at
least five minutes, and on again boiling should not become either
discoloured or cloudy. The commercial product cannot ahva\s be
expected to comply to this stringent test. It is important that the glass
vessel used for the test be scrupulously clean.
Free Acetic Acid. — The cold, saturated, aqueous solution of acetanilide
should not redden blue litmus paper.^
Acetic Acid.
CH3 . COOH. Molec. wt. 60-03.
Pure acetic acid comes into commerce of various strengths.
The 95-99 per cent, acid (glacial acetic acid) is a colourless liquid,
with a suffocating acid smell, miscible in all proportions with water,
alcohol, and ether. It has a sp, gr. of from i-o66-i-05S at 15°; it
should not solidify above 9°-5, and should boil at 110-117^ The
completely anhydrous acid boils at 118" and has a sp. gr. of 1-0553 ^^
Tests for Impurities.
Inorganic Matter and non-volatile Organic Matter. — No appreciable
residue should remain on evaporation of 10 c.c. of acetic acid.
Metals arid Alkaline Earths. — 20 c.c. of acetic acid, diluted with 100
c.c. of water, should show no brown coloration with sulphuretted
hydrogen water. 10 c.c. of acetic acid, diluted with 100 c.c. of water,
should remain unaltered on the addition of excess of ammonia, and
also on allowing to stand in a warm place for some time after the
addition of ammonium sulphide and of ammonium oxalate solution.
Arsenic. — 2 c.c. of acetic acid to which is added 6 c.c. of stannous
chloride solution should show no coloration on standing for an hour.
The Pharmacopoeia Committee of the General Medical Council
recommend the Gutzeit test as a limit-test for arsenic in acetic acid
and other official substances. A special apparatus is described for
1 For the testing and valuation of acetanilide, c/. E. Ritsert, Pharm. Zeit., 1890, 35, 306 ; /.
Soc. Chem. Ind., 1890, 9, 1068.
For the determination of acetanilide in pharmaceutical preparations, see J. L. Turner, and
C. E. V'anderklud, Pharm. J., 1907, p. 521 ; / Soc. Chem. Ind., 1907, 26. 4S6 ; also A. Seidell,
J. Amer. Chem. Soc, 1907, 29, I088 ; J. Soc. Chem. Ind,, 1907, 26, 9S9
ACETIC ACID 305
carrying out the test and filter paper soaked in a saturated solution of
mercuric chloride is used as the test-paper. The limit, in the case of
acetic acid, is placed at 2 parts of arsenic per 1,000,000.^ The Gutzeit
test is described in the section on " Sulphuric Acid," Vol. I., Part I.,
P- 374-
Sulphuric Acid. — A solution of 10 c.c. of acetic acid in 150 c.c. of
water heated to boiling, to which barium chloride solution is added,
should show no formation of barium sulphate even on standing for
several (fifteen) hours.
HydrocJiloric Acid. — A solution of 5 c.c. of acetic acid in 50 c.c. of
water should give no precipitate or opalescence on acidifying with 5 c.c,
of nitric acid and adding silver nitrate solution.
Empyreuinatic impurities and Sulphurous Acid. — 0-3 c.c. of A^/io
potassium permanganate solution should not be discoloured within a
quarter of an hour by 5 c.c. of acetic acid diluted with 15 c.c. of water.
A freshly made mixture of acetic acid and sulphuretted hydrogen water
should remain clear.
Formic Acid. — If a mixture of i g. of acetic acid, i g. of sodium
acetate, 10 c.c. of water, and 5 c.c. of mercuric chloride solution be heated
for half an hour in a boiling water-bath, there should be no separation
of mercurous chloride. Formic acid may be quantitatively estimated
by the following method : — 5 c.c. of the acetic acid are added to a solution
of 5 g. of sodium acetate in 30 c.c. of water ; 40 c.c. of mercuric chloride
solution (5 per cent.) are then added and the mixture heated for two
hours in a steam-bath, using a reflux condenser. The separated
mercurous chloride is collected in a Gooch crucible, washed with hot
water, dried and weighed. The weight found multiplied by 0-097726
gives the quantity of formic acid. -
Acetic acid used for technical purposes, e.g. in the colour industry,
need comply to but a few requirements, and the foregoing tests may
therefore be correspondingly relaxed. {^Cf. section on " Organic
Dyes," Vol. II., Fart II., p. 896.)
Quantitative Estimation.
1. By Titration. — The dilute aqueous solution of the acid is titrated
with N\\ potassium hydroxide, using phenolphthalein as indicator.
I c.c. of N\\ potassium hydroxide corresponds to 0-06003 g- of acetic
acid.
2. A gas-volumetric method of estimation has been proposed by H.
Kux,3
3. By the specific gravity as given in the subjoined Table prepared
by A. Oudemans. On mixing concentrated acetic acid with water, a
' Chem. and Drug., 1912, 81, 122. ^ Cf. Apoth. Zeit., 1910, p. 727.
^ Z, anal. Chem., 1893, 32, 138.
Ill u
306
ORGANIC PREPARATIONS
contraction in volume takes place -Aith a corresponding rise in specific
gravity, the latter attaining a maximum at a point corresponding to the
formation of the hydrate, C^H^O.^+HoO or ortho-acetic acid
[CH3. C(0H)3]. This hydrate contains yj per cent, of acid, and
has a sp. gr. of 10748. On further dilution the specific gravity
diminishes, so that a 51 per cent, acid has the same specific gravity as
an acid of 97 percent. Specific gravities above 10553 may therefore
indicate acids of different strengths. In determining the strength of an
acid by this method, the specific gravity is taken, and if it proves to
be over 1-0553 the acid is diluted with not too much water. If on
dilution the specific gravity rises, the acid is stronger than TJ per cent. ; if
the specific gravity diminishes, the acid is weaker than 'j'j per cent.
Table 39.
Specific Gravities of Acetic Acid at 15 (Oudemans).
Sp. gr.
Per cent.
Sp. gr.
Per cent.
Sp. gr.
Per cent.
Sp. gr.
Per cent.
1 -0007
1
' 1-0363
26
1-0623
51
1-0747
76
1 -0022
2
1-0375
27
1 0631
52
10748
77
1 -00:^.7
3
1-0388
28
1-0638
53
1-0748
78
1 •oo:.2
4
1-0400
29
1-0646
54
1-0748
79
1-0067
5
1-0412
30
1-0653
55
1-0748
80
1-0083
6
1-0424
31
1-0660
56
1-0747
81
1-0098
7
1-0436
32
1-0666
57
1-0746
82
1-0113
8
1-0447
33
1 -0673
58
1-0744
83
1-0127
9
1-0459
34
10679
59
1-0742
84
1-0142
10
1-0470
35
1-0685
60
1-0739
85
1-0157
11
1-0481
36
1-0691
61
1-0736
86
1-0171
1-?
1-0492
37
1-0697
62
1-0731
87
1 0185
13
1 -0502
88
1-0702
63
1-07-26
88
1-0200
14
1 1-0513
39
1-0707
64
1 -0720
89
1-0214
15
1 -0523
40
1-0712
65
1-0713
90
1-02-28
16
1-0533
41
1-0717
66
1-0705
91
1-0242
17
1-0543
42
1-0721
67
1 -0696
92
1-0256
18
1-0552
43
1-0725
68
1 -0686
93
1-0-270
19
1 -0562
44
1-0729
69
1-0674
94
1-0284
20
1-0571
45
1-0733
70
1 -0660
95
1-0298
21
1-0580
46
1 -0737
71
1-0644
96
1-0311
22
1-0589
47
1-0740
72
1 -0625
97
1 -0324
23
1 -0598
48
1-0742
73
1-0604
98
1-0337
24
1-0607
49
1-0744
74
1-058T
99
1-0350
25
1-0615
50
1-0746
75
1-0553
100
Calcium Acetate. — The most important raw material in the
manufacture of acetic acid is crude calcium acetate, which comes into
the market as a grey to brown mass more or less contaminated with
calcium carbonate and cmpyreumatic and decomposed organic matter.
For its valuation, a determination of the content of pure calcium acetate
or of acetic acid suffices. As a matter of practice the valuation may be
limited to the estimation of the latter, by distillation with phosphoric
ACETIC ACID 307
acid, according to the method given by R. Fresenius,^ which is carried
out as follows : —
A tubulated retort of suitable size, with its neck bent at an obtuse
angle, is fitted air-tight to a Liebig's condenser. Into the retort is
placed 5 g. of the calcium acetate to be tested, 50 c.c. of water, and
50 c.c. of phosphoric acid (free from volatile acids) of sp. gr. i-2;
the mixture is then heated on a sand-bath until all volatile products
have distilled over, i.e. to dryness, and the distillate very carefully
transferred to a 250 c.c. measuring flask. When the contents of the
retort have cooled, 50 c.c. of water are added and a second distillation
to dryness carried out. The same operation is repeated a third time,
and finally the total distillate is made up to 250 c.c, and 50 c.c. of the
solution titrated with A^/i sodium hydroxide, using phenolphthalein as
indicator, i c.c. Nl\ sodium hydroxide corresponds to 006003 g. of
acetic acid or 007907 g. of calcium acetate. The number of cubic
centimetres of sodium hydroxide used multiplied by 6-003 gives
the percentage content of acetic acid (CH^.COOH), and multiplied
by 7-907, the percentage content of anhydrous calcium acetate
[Ca(C.,H30,U
The triple distillation as given above may be dispensed with by
somewhat modifying the procedure as follows : — The tubulated retort is
connected up with a suitable steam supply, which may be readily
connected and disconnected and the steam led into the bottom of the
retort by means of a bent glass tube. As soon as the bulk of the
volatile matter has come over on the sand-bath, steam is allowed to
blow in through the thick residue, at the same time reducing the
heat of the sand-bath. F'or the distillation by steam a 500 c.c.
measuring flask is used as receiver. The distillation is stopped as
soon as the distillate ceases to be acid. The receiver is then filled
up to the mark with water and the contents well mixed by shaking.
When working on 5 g. of the crude acetate and using the data for
calculation given above, 100 c.c. of the acetic acid solution obtained by
distillation is titrated.
In this method of estimating acetic acid, small quantities of
homologous acids (propionic, butyric, etc.) contained in the calcium
acetate are determined along with the acetic acid and calculated as
such. This source of error is generally a matter of little importance in
technical work, but should it be desired to take these acids into account,
the method given by E. Luck ^ is recommended, which is based on the
^ Z. anal. Chem., 1866, 5, 315 ; 1875, 14, 172. Cf. also W. Fresenius and L. Griinhut, ihid.,
1908, 47, 597 ; /. Soc. Chem. hid., 1908, 27, 1012 ; J. Jedlicka, ibid., 1910, 49, 97 ; J. Soc. Cliem.
Ind., 1910, 29, 421 ; and T. S. Gladding, J. Ind. and Eng. Chem., 1909, I, 250 ; J. Soc. Chem.
Ind., 1909, 28, 467.
- Z, anal. Chem., 1871, 10, 184 ; cf. also Pharm, Zeit., 1910, p. 810.
308 ORGANIC PREPARATIONS
different solubilities of the barium salts of these homologous acids in
absolute alcohol.
To carry out this method the distillate obtained in the manner
previously given is neutralised with barium h\droxide, evaporated to
dryness, and well boiled with Soo c.c. of absolute alcohol. The alcoholic
solution, which contains the barium salts of the homologous acids and
0-0284 g. of barium acetate per 100 c.c, is cooled and filtered, the
alcohol evaporated off, the residue taken up with water, the barium
precipitated with sulphuric acid, and the barium sulphate weighed.
From the weight of the latter, 0-2085 S- nriust be subtracted to allow
for the barium acetate (as barium sulphate) dissolved by the 800 c.c.
of alcohol, and the remaining barium sulphate calculated to calcium
acetate (i g. barium sulphate = 0-6774 g. calcium acetate). The
quantity of calcium acetate thus found is deducted from the amount
found by titration.
If the calcium acetate to be examined contains appreciable quantities
of calcium chloride, the distillate obtained by the foregoing methods
will contain hydrochloric acid. A portion of the distillate is therefore
tested for chloride by adding nitric acid and silver nitrate solution.
If only an opalescence is produced, the trace of hydrochloric acid
may be neglected, but if a precipitate of silver chloride be formed,
the hydrochloric acid xnust be estimated either volumetrically with A71
silver nitrate solution or by weighing the precipitate of silver chloride,
and the quantity found allowed for.
Acetone.^
CH3 . CO . CH3. Molec. wt. 58-05.
Acetone is a colourless, mobile, neutral liquid, readily inflammable,
burning with a luminous non-smoky flame. It has a peculiar, not
unpleasant smell and a camphor-like taste. Acetone boils at 55-56"',
and has a sp. gr. of 0-798. It is miscible with water, alcohol, ether,
chloroform, and oils in all proportions. When 10 c.c. of acetone are
mixed with 10 c.c. of ammonia, which should produce no warming
of the solution (aldehyde), then 10 c.c. of N/i iodine solution added
and the mixture diluted with 60 c.c. of water, a cloudiness due to the
formation of iodoform is produced.^
Tests for Impvirities.
Non-volatile Matter. — On evaporation, 25 c.c. of acetone should leave
no residue.
^ Cf. the section on " Explosives," Vol. II., Part I., pp. 492 et seq.
'^ For identifying and colour reactions, cf. Pharvi, Ztntralh.^ 36, 616 ; 37, 439 ; Z. anal, C/icm.,
1893, 32, 347 ; 1898, 37, 47 ; Cheni. Zeit., 1909, 33, 570 ; and Merck's Reag.-Verz., 1908, p. 289.
ACETONE 309
Free Acid. — Blue litmus paper should not be reddened.
Einpyreuniatic Matter. — A mixture of equal parts of acetone and
water should be clear.
Aldehyde} — A mixture of lo c.c. of acetone and 5 c.c. of ammoniacal
silver solution is warmed for fifteen minutes in a water-bath at 50", the
test being carried out in the dark. No darkening of the solution or
separation of metallic silver should take place. (The silver solution
for this test is prepared by mixing 10 c.c. of a 5 per cent, silver
nitrate solution with 5 c.c. of 10 per cent, ammonia.)
Action of Potassium Permanganate. — lo c.c. of acetone to which is
added a drop of potassium permanganate solution (i : 1000) should
retain the pink colour for at least fifteen minutes at a temperature not
above 15°. By this test the presence of aldehyde is indicated.^ The
usual requirement in this country is that a distinct colour should remain
for thirty minutes when i c.c. of a o-i per cent, pure permanganate
solution is added to 100 c.c. of acetone at i5°-5. Acetone containing
0-5 per cent, by volume of aldehyde discolours the permanganate in five
minutes, and if it contains 0-25 per cent, by volume of aldehyde, the
discoloration is complete in ten minutes. Free mineral acids should
not be present, since these discharge the permanganate colour in the
case of aldehyde-free acetone.
Water. — 30 c.c. of acetone are shaken in a closed flask with ignited
potassium carbonate, when the latter should show no signs of becoming
damp. On mixing 50 c.c. of acetone with 50 c.c. of petroleum spirit
(boiling point 40°-6o°) no indication of the separation of the liquid into
two layers should be visible.
Quantitative Estimation.
G. Kramer has worked out a method for determining acetone in
methyl alcohol, which may be equally well applied to its estimation in
commercial acetone. For this purpose acetone is diluted with 9 parts
of water, sufficient sodium hydroxide solution and iodine solution
added, and the mixture extracted with an accurately measured quantity
of ether, which dissolves out the iodoform formed. An aliquot part of
the ethereal solution is then evaporated off on a weighed clock-glass, the
residue dried over sulphuric acid and weighed. From the weight of
iodoform found the content of acetone is calculated ; 3-94 g. of iodo-
form correspond to 0-58 g. of acetone.^
Volumetric modifications of this method are described below under
1 <7. Vol. II., Part I., p. 493.
"^ For the detection of aldehyde, cf. also Z. anal. C/iein., 1883, 22, 259 ; 1891, 30, 208 ; 1895,
34. 226.
^ Be}-., 1880, 13, 1000. On a source of error in this method of estimation, f/ Vaubel and
Scheuer, Z. angew. Chem.^ 1905) 18, 214.
310 ORGANIC PREPARATIONS
the estimation of acetone in methyl alcohol (p. 364) and in the section
on " Explosives," Vol. II., Part I., p. 493.
H. Strache ^ has proposed a method which consists in converting
the ketone, in sodium acetate solution, into the hydrazone by means of
an excess of phenylhydrazine. The hydrazone is not acted upon by
Fehling solution, but the excess of phenylhydrazine is decomposed by
hot Fehling solution giving up its nitrogen completely, which latter
may be determined gas-volumetrically. The nitrogen found gives the
unused phenylhydrazine ; the used phenylh}drazinc is obtained by
difference, from which data the acetone can be calculated. -
Acetyl Salicylic Acid (Aspirin).
O.COCHgCO
CgH / . Molec. wt. i8o-o6.
\C00H(2)
Acetyl salicylic acid forms small white crystalline needles possessing
a slightly acid taste, which dissolve in 300 parts of water, readil)' in
alcohol and in sodium hydroxide and sodium carbonate solutions.
Melting point, 175°.
When 0-5 g. of acetyl salicylic acid is boiled for two to three
minutes with 10 c.c. of sodium hydroxide and, after cooling, dilute
sulphuric acid added, a transitory violet coloration is first produced,
and then a white crystalline precipitate of salicylic acid separates out.
If the precipitate is filtered off, the filtrate smells of acetic acid, and on
boiling with a little alcohol and sulphuric acid gives the characteristic*
smell of ethyl acetate.
Tests for Impurities.
Salicylic Acid. — A solution of o-i g. of acetyl salicylic acid in 5 c.z.
of alcohol, prepared in the cold, to which 20 c.c. of water are added,
should not give an immediate violet coloration on the addition of a
drop of ferric chloride solution.
Hydrochloric and Sulphuric Acids. — If i g. of acetyl salicylic acid is
shaken for five minutes with 20 c.c. of water, the filtrate should remain
clear on the addition of silver nitrate and of barium nitrate solutions.
Organic Impurities. — i g. of acetyl salicylic acid should dissolve to a
colourless solution in 10 c.c. of concentrated sulphuric acid.
Inorganic Impurities. — On burning off i g. of acetyl salicylic acid, no
appreciable residue should be left.
' .Monatsh., 1891, 12, 524 ; Z. anal. C/iem., 1892, 31, 573.
- For detecting and estimating wood spirit in acetone, cf. F. W. Rabington, J. Soc. Chem.
Ind., 1907, 26, 243.
For the quantitative estimation of acetone in crude acetone, cf. G. Heikel, Chtm, Zeil., 1908,
32, 75 ; /• So<^- Chem. /W., 1908, 27, 114 ; and S. J. M. Auld, J. Soc. Chem. htd., 1906, 25, 100.
AMYL ACETATE 311
Quantitative Estimation.
I g. of acetyl salicylic acid is boiled for three minutes with 15 c.c. of
Ay I sodium hydroxide solution, allowed to cool, and then titrated with
Nji hydrochloric acid, using phenolphthalein as indicator; 3-9 c.c. of
Nji hydrochloric acid should be necessary to discharge the red colour.
I c.c. of Nji sodium hydroxide corresponds to 0-09003 g. of acetyl
salicylic acid.
Amyl Acetate.
CH3 . COOQH,^. Molec. wt. 130-1 1.
Amyl acetate (isoamyl acetate) is a colourless, mobile, peculiar
smelling liquid. Chemically pure amyl acetate has a sp. gr. of 0-8692,
and boils at 138°. The commercially pure products which come on to
the market have a sp. gr. of 0-867-0-869, and boil between 135°- 142°.
Amyl acetate dissolves readily in alcohol, ether, benzene, chloroform,
and glacial acetic acid, but is quite insoluble in water.
Tests for Impurities.
Inorganic and non-volatile Organic Compounds. — 10 c.c. of amyl
acetate should not leave more than 0-5 mg. of residue on evaporation.
HydrocJiloric Acid and Sulphuric Acid. — On shaking 30 c.c. of amyl
acetate with 15 c.c. of water, the separated water should at most only
give a slight opalescence with silver nitrate solution, and should show
nothing with barium chloride solution, even on standing for some time.
(The separated water always reacts acid on account of the presence of
small quantities of free acetic acid.)
Alcohol. — On shaking 25 c.c. of amyl acetate with 25 c.c. of a
saturated calcium chloride solution and allowing the liquids to
separate completely, the calcium chloride solution should, at most, show
an increase in volume not greater than i c.c.
Note. — Amyl acetate comes into commerce in 10 per cent, alcoholic
solution, as pear oil. On treating such a product with calcium chloride
solution it gives up about 90 per cent, of its volume to the latter ; for
this reason it is better to shake up with a proportionally large volume
of calcium chloride solution. It is generally sufficient in dealing with
such products to only take notice of the content of amyl acetate. The
content of alcohol cannot be judged from the specific gravity, since
alcohol of 75-76 per cent, by volume has the same specific gravity as
amyl acetate.
Water. — Amyl acetate should dissolve to a clear solution when
mixed with ten times its volume of benzene. The purest, anhydrous
amyl acetate mixes in the same proportion (i : 10) with petroleum spirit
312 ORGANIC PREPARATIONS
and with official paraffin oil (liquid paraffin), producing perfectly clear
solutions. The test with the latter is specially sensitive.
Amyl Nitrite.
(CH3).,CH.CH,.CHo.O.NO. Molec. wt. 117-10.
Amyl nitrite is a clear yellow liquid with a fruity smell. It is quite
insoluble in water, but mixes with alcohol and ether in all proportions.
Authorities differ as to the boiling point; Hilger gives 94°-95°,
Bernthsen 96^ Dunstan and Williams ^ 97°, Chapman- 97°-98, and
Guthrie '"^ 99°. Dunstan and Williams give a sp. gr. of o-88o,
Hilger of 0-902, the British Pharmacopoeia of 0-870-0-880, and the
German Pharmacopoeia of 0-875-0-885. The commercial preparations
generally have a lower boiling point than given above. A sample,
however, which begins to boil at 90^ cannot be pure, even if it other-
wise conforms to requirements, whilst a sample boiling above 99° points
to a too high content of amyl alcohol. It is to be borne in mind that
amyl nitrite continually undergoes slow decomposition, which may
account for variations in the boiling point and specific gravity as well
as in the content of acid and of amyl alcohol.
Amyl nitrite burns with a yellow, luminous, smoky flame. On the
addition of hydrochloric acid and a few crystals of ferrous sulphate a
brown coloration is produced.
Tests for Impurities.
Free Nitrous Acid. — A mixture of i c.c. of water, o-i c.c. of ammonia
(sp. gr. 0-96), and 2 drops of tincture of litmus shaken up with 5 c.c.
of amyl nitrite should not be reddened ; this indicates a maximum
content of about 0-35 per cent, of nitrous acid.
Valeryl Aldehyde. — A mixture of i c.c. of amyl nitrite, 1-5 c.c. of
silver nitrate solution, 1-5 c.c. of absolute alcohol, and a few drops of
ammonia should not be turned brown or black on gently warming.
Water. — Amyl nitrite should not become turbid when cooled down
to o^
Ethyl Alcohol. — 10 c.c. of water and 10 c.c. of amyl nitrite are shaken
up in a graduated measuring cylinder. If alcohol is present in not too
small a quantity, the volume of water increases. The separated water
will give the iodoform reaction.
Quantitative Estimation.
Amyl nitrite may be estimated volumetrically in various ways.
1 Pharm.J., 1888, 19, 487. - Laboratory, 1867, p. 375.
^ J. Chem. Soc, 1859, II, 245.
AMYL NITRITE 313
The method given for estimating ethyl nitrite, by E. Schmidt,^ may be
applied, as also that by Curtmann.^
The best and simplest method is the gas-volumetric estimation,
which is carried out as follows : — 26 g. of amyl nitrite are diluted with
91 per cent, alcohol to 500 c.c. in a measuring flask. 5 cc. of the dilute
alcoholic solution are introduced into a nitrometer (Vol. I., Part I., p.
132), and 10 c.c. of potassium iodide solution (i : 5) and then 10 c.c. of
Nji sulphuric acid added. The volume of nitric oxide evolved is
measured and corrected for temperature and pressure. It generally
suffices when reading off the volume at about 20" to reckon ever)- cubic
centimetre of gas as equivalent to 2 per cent, of amyl nitrite. A good
sample of amyl nitrite would liberate at least 40 c.c. of nitric oxide,
equivalent to 80 per cent, of amyl nitrite, whilst a pure 100 per cent,
sample would yield 50 c.c The reaction proceeds according to the
following equation : —
C5H11NO.+ KI + H.3SO, = I + KHSO^ + QHiiOH + NO.
At normal pressure, i c.c. of nitric oxide at 0° weighs 0-0013402 g.
If it is desired to take accurate readings, the volume found is reduced
to 0° and 760 mm. pressure by the following formula : —
^ _ 76o.(i+0'0366/)
where Vq is the corrected volume at 0°, V^ is the observed volume,
b the observed atmospheric pressure, and t the observed temperature.
The following quite good method for the estimation of amyl nitrite
is prescribed by the Dutch Pharmacopceia : — 0-5 g. of amyl nitrite are
dissolved in 10 c.c. of alcohol, and 15 c.c. of an aqueous solution of
potassium chlorate (i : 20) and 5 c.c. of nitric' acid (sp. gr. 1-316) added.
The mixture is allowed to react for one hour, with frequent shaking.
Then 20 c.c. of iV/io silver nitrate solution and 5 drops of an aqueous,
saturated solution of ferric ammonium sulphate are added, and the
excess of silver nitrate determined by titration with A710 ammonium
thiocyanate solution. Not more than 8-6 c.c. of the thiocyanate solution
should be required to produce a red coloration ; this condition corre-
sponds to a minimum content of 80 per cent, of amyl nitrite, i c.c. of
A710 silver nitrate solution = 0-0351 g. of CgH^iNO.,.
Apomorphine Hydrochloride.
C17H17O2N . HCl. Molec. wt. 303-61.
Apomorphine hydrochloride crystallises in small white or grey
crystals which are soluble in about 50 parts of water and 40 parts
1 Pharmazeutische Chetnie., 3rd edition, vol. ii., p. 567.
^ C/. Siidd, Apoth. Zeit., 1898, p. 716 ; also ibid., 1896, pp. 66 and 305, for a description and
criticism of different methods of estimation.
314 ORGANIC PREPARATIONS
of alcohol (of about 85 per cent, by weight). It is quite insoluble
in ether and chloroform. The solutions react neutral with littnus
paper and gradually turn green on standing in the light and in
air ; if some hydrochloric acid, however, is added to the solu-
tions they remain unchanged for a longer time, but the addition
of too much hydrochloric acid causes apomorphine hydrochloride to
separate out. On standing over sulphuric acid, apomorphine hydro-
chloride gradually loses in weight to the extent of about 3-6 per cent.
The salt dried in this way regains its original weight on exposure to
the air.
Apomorphine hydrochloride dissolves in nitric acid, producing
a blood-red coloration. The addition of a drop of very dilute ferric
chloride solution to an aqueous solution of the salt (i : 10,000) turns
the latter blue. If to 10 c.c. of an aqueous solution (i : 10,000) i c.c. of
chloroform is added, and after the addition of sodium h)droxide solution
the mixture is im.mediately shaken with air, the aqueous liquid assumes
a transitory reddish-violet, and the chloroform a blue coloration. Silver
nitrate solution produces with an aqueous solution of the salt, after the
addition of a drop of nitric acid, a white curdy precipitate which
is blackened immediately on the further addition of ammonia.
Tests for Impvirities.
Oxidation Products of Apomorphine. — A freshly prepared solution
(i : 100 of water) should be colourless or only very faintly coloured.
5 c.c. of ether shaken with 01 g. of dry apomorphine hydrochloride
should remain colourless or show only a very faint pink coloration.
Other Alkaloids. — If 01 g. of apomorphine hydrochloride be placed
on a small, dry filter paper, and 5 c.c. of a mixture of i c.c. of hydro-
chloric acid with 4 c.c. of water poured over it, on addition of potassium-
mercuric iodide solution to the filtrate, at most only an opalescent
turbidity should be produced.
^-Cliloro-morpJiide. — 01 g. of apomorphine hydrochloride is dissolved
in 10 c.c. of water, 20 c.c. of ether poured on, 5 c.c. of a cold, saturated
solution of sodium carbonate added, and the mixture shaken until the
precipitate which is first formed redissolves. The aqueous solution is
run off, the ether well washed three times with about 20 c.c. of water,
and then completely evaporated off in a test tube. To the cooled
residue 5 c.c. of concentrated nitric acid containing 05 percent, of silver
nitrate are added, and after standing for ten minutes the test tube is
placed in a boiling water-bath for one hour. At the end of this time
there should be no appreciable flakes of silver chloride at the bottom
of the clear, undiluted brown liquid.^
1 Pharm. Zentral/i., igtl, 52, 537 ; /. Soc. Chem. hid., 1911, 30, 1278.
ATROPINE 315
Inorganic Ivipuritics.— On ignition, i g. of apomorphine hydro-
chloride should not leave more than 05 mg. of residue.^
Atropine.
CiyH^sOgN. Molec. wt. 289-19.
Atropine crystallises in small, colourless needles which dissolve in
about 300 parts of water and which are readily soluble in alcohol
(90 per cent), ether, and chloroform. Melting point, 1 15°-5.
Tests and Quantitative Estimation.
Hyoscyanime. — The free base should be optically inactive. The
more hyoscyamine it contains the more laevorotatory will it be. (The
rotatory power of hyoscyamine is (a)n = - 20°-97.)
The tests for inorganic and organic impurities as well as for foreign
alkaloids are carried out as described below for atropine sulphate.
To estimate atropine volumetrically, about 01 g. is dissolved in
50 c.c. of absolute alcohol, some pure lackmoid ^ added, and the solution
titrated with Njio hydrochloric acid until the blue colour changes to
red. I c.c. of NJio hydrochloric acid corresponds to 0-02892 g. of
atropine.
Atropine Sulphate.
(Ci7H.,303N),H2S04+ H2O. Molec. wt. 694-49.
Atropine sulphate comes into commerce in white crystalline masses
(small crystalline needles). The melting point depends on the con-
ditions under which it is taken. If Roth's apparatus be used, and the
temperature raised very slowly, the best commercial product dried over
sulphuric acid gives a melting point of 185°; if heated quickly, the
melting point is higher, and the same product may be found to give a
melting point as high as 190°. These differences point to the melting
point of atropine sulphate being in reality a decomposition point. The
melting point given by the British Pharmacopoeia is 183°. In doubtful
cases it is safest to prepare the gold chloride double salt and to take
its melting point, which in the case of a good preparation should not be
above 138°. According to the instructions of the German Pharmacopoeia
the melting point of the free base is determined. For this purpose
ammonia is added to the aqueous solution of atropine sulphate (i : 25),
the crystals which separate on standing collected on a small filter paper,
washed with water and dried over sulphuric acid ; they should melt at
115°.
' On doubtful modern commercial preparations of apomorphine, cf. Harnack and Hilde-
brandt, Phar7n. Zeit., 1909, 54, 938 ; 1910, 55, 6 and 693. On apomorphine hydrochloride substi-
tutes, see Frerichs, Apoth. Zeit., 1909, p. 928.
^ Z. atigew. C/iem., 1 903, l6, 449, 468.
316 ORGANIC PREPARATIONS
Atropine sulphate, which dissolves readily in water and alcohol to a
colourless neutral solution, is difficultly soluble in ether, benzene, and
chloroform.
If o-oi g. of atropine sulphate is evaporated to dryness on a
water-bath with fuming nitric acid, a pale yellow residue is left, which,
when cold, produces a violet coloration on the addition of alcoholic
potash.^
Tests for Impvirities.
Inorganic Matter. — On ignition, o-i g. of atropine sulphate should
not leave more than 0-5 mg. of residue.
Organic Impurities. — o-i g. of atropine sulphate should dissolve
without coloration in 5 c.c. of sulphuric acid.
Other Alkaloids. — The solution in sulphuric acid should remain
colourless on the addition of nitric acid. The aqueous solution of
atropine sulphate (o-i : 6) should not be rendered turbid by ammonia.
Hyoscyaniine. — The free base obtained from the aqueous solution by
the addition of alkali and extraction with ether should, after drj'ing,
give the melting point of atropine and be inactive in alcoholic solution.
Water. — i g. of atropine sulphate should not lose more than 0-026 g.
in weight on drying at 100°.
Atropine sulphate may be titrated in pure alcoholic solution with
A710 sodium hydroxide, using Poirrier's blue as indicator, and excluding
carbon dioxide from the air.- {Cf. Quinine hydrochloride, p. 381.)
Benzaldehyde.
CoH,. COH. Molec. wt. 10605.
Benzaldehyde is a colourless, highly refractive liquid with a character-
istic smell. It boils at 1 77°- 1 79", and has a sp. gr. of i-046-i-054. It
dissolves readily in alcohol, ether, benzene, chloroform, and petroleum
spirit, but only sparingly in water (about i in 300 parts).
Tests for Impurities,
Inorganic Matter. — On heating, benzaldehyde burns with a ver)-
smoky flame, and leaves no residue on ignition.
Chlorine. — 2 g. of benzaldehyde are put into a small porcelain
crucible, which is placed on a porcelain plate of suitable size. The
benzaldehyde is ignited with a Bunsen burner, and a 2 litre beaker, the
inside of which is moistened with water, is placed over the burning
benzaldehyde, and is lifted now and again from the plate so as to
regulate the supply of air. It is well to extinguish the flame a few
^ For other identifying reactions, cf. Merck's Reai^.-Verz,^ IQ^S, p. 290.
" For further details, cf. Z. angetu. Chem,, 1903, 16, 470.
BENZALDEHYDE 317
times and re-moisten the beaker before re-lighting. When all the
benzaldehyde is burnt in this manner, the beaker and plate are washed
with a little water, which is then filtered through a small filter paper,
and the filter paper washed with water until a filtrate of 20 c.c. is
obtained. After acidifying the filtrate with a few drops of nitric acid,
silver nitrate solution is added which should only produce a very faint
opalescence.
Synthetically prepared benzaldehyde is never absolutely free from
chlorine.
Organic Chloride {e.g. Benzyl chloride). — 10 g. of benzaldehyde are
subjected to distillation, and the first 10-12 drops that come over are
collected in 5 per cent, alcoholic potash. This solution is then heated
for some time, using a reflux condenser, and the alcohol finally evaporated
off. The residue is taken up with water, shaken with ether to remove
oily products, nitric acid added to the aqueous solution after pouring off
the ether, and the separated benzoic acid filtered off. The filtrate is
tested for chlorine with silver nitrate solution as above.
Chloro-benzaldehyde. — 2 c.c. of benzaldehyde are shaken with 40 c.c.
of water, 6 g. of sodium carbonate (free from chlorine) added, the
mixture gently heated, and 5 per cent, potassium permanganate solution
(free from chloride) added gradually until the smell of oil of bitter
almonds has completely disappeared. If the red coloration due to per-
manganate does not also disappear, alcohol is added, drop by drop,
until the solution is colourless. The mixture is filtered and dilute
sulphuric acid (free from chlorine) added. When quite cold, the
separated benzoic acid is collected on a filter paper, washed with cold
water, dissolved in sodium carbonate solution, and after the addition of
potassium nitrate evaporated to dryness and ignited. The ignited
residue is dissolved in water and nitric acid, made up to 20 c.c, and
tested for hydrochloric acid with silver nitrate as above.
Nitrobenzene. — 2 drops of phenol, 3 drops of water, and a piece of
potassium hydroxide the size of a pea are placed in a small porcelain
dish. The mixture is heated carefully to boiling, and then the benzalde-
hyde under examination, shaken up with water, added. After keeping at
the boil for some time a carmine red ring appears at the edges of the
liquid. On the addition of a saturated solution of calcium hypochlorite
the colour of the ring changes to emerald green in the presence
of nitrobenzene.^ If present in appreciable quantities, nitrobenzene
raises the specific gravity of benzaldehyde. 5 c.c. of pure benzal-
dehyde at 12"'^ weigh from 5-2055-5-222 g. ; if it contain 25 per cent,
of nitrobenzene the weight of 5 c.c. becomes 5-39 g. ; and if 50 per cent,
5-57 g-
A further test for nitrobenzene is carried out as follows: — i g. of
' Marpurgo, Pharm. Zeitschr. /. Russland, vol. 29, p. 205.
318 ORGANIC PREPARATIONS
benzaldehyde, dissolved in 20 c.c. of alcohol, is diluted with water until
a permanent turbidity is produced. Granulated zinc and sulphuric acid
are then added. When the evolution of hv-dro^en has ceased, the
solution is filtered, the alcohol evaporated off, and the aniline formed
from the nitrobenzene detected as follows: — To half the filtrate, a few
drops of potassium bichromate solution is added and the solution
boiled for a short time ; in the presence of aniline a pale violet colora-
tion is produced. The other half of the filtrate is neutralised with
potassium hydroxide, and sodium hypochlorite added ; if aniline be
present a violet coloration is formed.
Alcohol. — If 20 c.c. of benzaldehyde are shaken up with 20 c.c. of a
cold, saturated solution of calcium chloride, the volume of the latter
should not be found to have increased after completely separating the
liquids. If 3 c.c. of benzaldehyde are mixed with 10 c.c. of nitric acid
(sp. gr. 1-4) the presence of alcohol will cause an evolution of gas and of
red fumes.
Water. — Benzaldehyde should dissolve to a perfectly clear solution
in ten times its volume of petroleum spirit (boiling point 50°-75°).
Benzoic Acid. — Benzaldehyde always contains some benzoic acid, since
it readily oxidises in presence of air. In the purest commercial product
1-3 per cent, is not uncommon. Up to 14 per cent, of the acid remains
dissolved in the benzaldehyde at 15°, but if the proportion be larger
it crystallises out. To estimate the benzoic acid, 10 g. of benzaldehyde
are dissolved in 50 c.c. of dilute alcohol (70 per cent, by volume), and the
solution titrated with N\\ sodium hydroxide solution (i c.c. =0-122048 g.
benzoic acid), using phenolphthalein as indicator.
Hydrocyanic Acid. — 2 c.c. of benzaldehyde are shaken with 20 c.c. of
TV/i potassium hydroxide solution, a few drops of ferrous sulphate
solution added, and the mixture heated nearly to boiling. Hydro-
chloric acid is then added in excess, and then a drop of ferric chloride
solution. If hydrocyanic acid be present it will be recognised b)' the
formation of Prussian blue.
II)'drocyanic acid occurs in oil of bitter almonds, and can therefore
be found in benzaldehyde prepared from this source. Oil of bitter
almonds itself usually comes on to the market, labelled either " free
from prussic acid" or "containing prussic acid." The oil of bitter
almonds "free from prussic acid" is not poisonous. Natural oil of
bitter almonds containing prussic acid can be distinguished from the
chemically prepared benzaldehyde by a method due to A. Kremel,^
according to which oil of bitter almonds containing prussic acid yields
benzoin, without the addition of potassium cyanide, whilst the chemi-
cally prepared benzaldeh}'de docs not.
' Pharm. Zenlralh., 30, 134.
BENZOIC ACID 319
Benzoic Acid.
CgHg . COOH. Molec. wt. 12205.
Two varieties of benzoic acid come on to tlie market, the official
benzoic acid prepared from gum benzoin, and the chemically pure
product prepared from either benzyl chloride, benzal chloride, benzotri-
chloride or hippuric acid.
(a) Official Benzoic Acid.
This is sublimed from Siamese gum benzoin, and forms small white
or brown leafy or needle-like crystals of a silky appearance, which
possess a characteristic burning smell. It melts at 120°, and boils
at 249".
Benzoic acid dissolves in 270 parts of water at 15" and readily in
hot water, in ether, alcohol, benzene, chloroform, petroleum spirit, and
carbon bisulphide.
On shaking o-2 g. of benzoic acid frequently during fifteen minutes
with a mixture of i c.c. of iV/i potassium hydroxide solution and
20 c.c. of water, filtering, and adding to the filtrate a drop of ferric
chloride solution, a reddish-brown to dirty red precipitate is produced.
Tests for Impurities.
Official benzoic acid should melt in boiling water, when more acid
is used than will dissolve in the quantity of water taken. Chemically
prepared benzoic acid does not melt under these conditions.
Inorganic and foreign Organic Matter. — On heating 0-2-0-3 g. of
benzoic acid in a test tube, it first melts to a yellow then to a brown
mass, and then sublimes, and should finally leave either no residue or
only a very slight brown residue. No charring should take place ;
should this occur it would point to the presence of sugar, hippuric,
tartaric, or citric acids.
Salicylic Acid. — An aqueous solution of the benzoic acid to which
ferric chloride solution is added, and from which the precipitate pro-
duced is filtered off should show no violet coloration.
Suniatj-a Benzoic Acid ; Cinjiamic Acid. — i g. of benzoic acid heated
in a closed test tube in a boiling water-bath, with i g. of potassium
permanganate and 10 c.c. of water for from ten to fifteen minutes, should
give no smell of oil of bitter almonds on cooling.^
The British Pharmacopoeia prescribes that benzoic acid should not
develop the odour of benzaldehyde when warmed with its own weight
of potassium permanganate, and ten times its weight of dilute sulphuric
acid.
^ Cf. also Schacht's reaction for Siamese benzoic acid ; Merck's Reag.-Verz,, 1008, p. 228.
320 ORGANIC PREPARATIONS
Chcviically prepared Acid. — I g. of benzoic acid dissolves to a yellow
or brown solution in lo c.c. of ammonia, and the addition of excess of
sulphuric acid causes the acid to separate out again. If to this mixture
are added 5 c.c. of potassium permanganate solution (i : 1000), the red
colour of the latter should completely disappear after standing for
four hours.
Hippuric Acid. — 0-2 g. of benzoic acid are rubbed into a paste with
a few drops of water and 0-3 g. of pure quicklime, then dried and
ignited. No ammonia should be liberated.
Synthetic Benzoic Acid. — 04 g. of benzoic acid is mixed with 0-6 g.
of calcium carbonate free from chloride, and a little water, evaporated to
dryness on the water-bath, and then ignited. On dissolving the residue
in nitric acid and water, and making up to 20 c.c, the addition of silver
nitrate solution should only produce a slight opalescence. This test,
which shows the presence of chloro-benzoic acid, and which indicates
whether chemically prepared benzoic acid from benzalchloride, benzyl-
chloride, benzotrichloride, etc., has been added or not, is not absolutely
reliable. Chemically pure benzoic acid comes into commerce containing
no more chlorine than the acid sublimed from gum benzoin, and the
addition of such a chemically pure acid to the acid from gum benzoin
cannot be detected b)- the above reaction for chlorine. Only gross
adulteration by means of cheap benzoic acid containing chlorine can be
detected in this manner. This reaction has been retained up to now,
since for a long time it was not possible to prepare the acid chemically,
free or approximately free from chlorine.^ H. Hagar,- in order to
detect whether a benzoic acid is a pure product from sublimation or
whether it has only been sublimed over gum benzoin, uses a reagent of
doubtful value, prepared by acidifying a solution of ferric chloride and
potassium ferricyanide with hydrochloric acid.
(b) Chemically pure Benzoic Acid.
This acid is distinguished from the acid obtained from gum benzoin
by its pure white colour, its colourless solution in alcohol and ammonia,
and its freedom from empyreumatic matter. It does not melt in
boiling water, melts at 121-4 ^'id boils at 249".
Tests for Impurities.
Inorganic and foreign Organic Matter. — i g. of benzoic acid on
heating should not leave more than 05 mg. of residue. Heated in a
test tube it should sublime completely without charring, i g. of
benzoic acid .should dissolve in 20 c.c. of sulphuric acid to a colourless
or only faint yellow solution.
' For the detection of chlorine in benzoic acid, cf. Pharm. Zeutralh., 1 899, p. 183.
2 Pharm. Zentralh.^ 26, 392.
BROMOFORM 321
Chloro-benzoic Acid. — 0-4 g. of benzoic acid ignited with calcium
carbonate and dissolved, as in the case with the official product, should
show no immediate opalescence on the addition of silver nitrate solution,
and on standing for five minutes only a faint turbidity.^
Quantitative Estimation.
The purity of benzoic acid may be controlled by titration with
potassium hydroxide. For this purpose i g. of benzoic acid is dissolved
in 10 c.c. of N\\ potassium hydroxide solution, diluted with 40 c.c. of
water, and titrated with A^i hydrochloric acid, using phenolphthalein
as indicator, i c.c. of Nji potassium hydroxide corresponds to 0-122048
g. of benzoic acid.
Bromoform.
CHBrg. Molec. wt. 25277.
Bromoform is a colourless liquid with a smell somewhat similar to
that of chloroform. It is very sparingly soluble in water, but is
miscible in all proportions with alcohol, ether, benzene, and petroleum
spirit. The purest bromoform has a sp. gr. of 2-904, melts at 9°, and
boils at I49°-I50°.
Tests for Impurities.
Non-volatile Matter. — 20 c.c. of bromoform should leave no residue
on volatilisation.
Bromine. — Bromoform should be quite colourless. On shaking 5
c.c. of bromoform with 5 c.c. of water, and i c.c. of zinc iodide-starch
solution, the bromoform should remain colourless and the starch
solution should not be immediately turned blue.
Hydrobromic Acid. — On shaking 10 c.c. of bromoform with 10 c.c. of
water, the separated water should not immediately redden blue litmus
paper. On carefully pouring the separated water on to silver nitrate
solution, no opalescent ring should be visible at the point of contact of
the two layers of liquid.
Foreign Orgastic Matter. — On shaking 10 c.c. of bromoform with
10 c.c. of sulphuric acid in a glass cylinder, previously washed out with
sulphuric acid, the sulphuric acid should remain colourless for ten
minutes.
Aldehyde. — On shaking 20 c.c. of bromoform with 10 c.c. of water,
the separated water, on the addition of ammonia and silver nitrate
solution, should show no reducing action on the silver nitrate for at
least half an hour.^
1 Pharm. Zentral/i., 1900, pp. 449, 529.
2 On the decomposition of bromoform by light and air, cf. Berichte der deutschen Pharm. Ges.
Berlin, 1905, p. 387 ; y. Soc. Cliem. Ind,, 1906, 25, 232.
Ill X
322 ORGANIC PREPARATIONS
Caffeine.
C,HO,N,(CH3)3+H,0. Molec. wt. 212-14.
Caffeine crystallises in white, glistening, flexible needles which are
soluble in So parts of water, 50 parts of alcohol (of about 85 per cent,
by weight), and in 9 parts of chloroform ; it is but spariiigl}' soluble in
ether. It effloresces in the air and loses its water of crystallisation
completely at 100°. Melting point 235°.
An aqueous solution of caffeine is precipitated by tannic acid
solution ; the precipitate is soluble in an excess of the precipitating
reagent. On evaporating a solution of i part of caffeine in 10 parts
of chlorine water on the water-bath a yellowish-red residue remains,
which changes to a beautiful purple-red colour on immediately treating
with a little ammonia.^
Tests for Impurities,
Alkaloids. — Caffeine should dissolve to a colourless solution in
concentrated sulphuric acid and in nitric acid. A cold, saturated
solution of caffeine in water should not be rendered turbid by chlorine
water or by iodine solution, and should remain colourless on the
addition of ammonia.
Inorganic Impurities. — i g. of caffeine should volatilise on heating
without charring, and should not leave more than 0-5 g. of residue.
Caffeine is considerably more soluble in water in the presence of
various salts such as sodium benzoate, sodium salicylate, and sodium
cinnamate, than in water alone. This increased solubility is due to the
formation of double salts ; of these double salts caffeine-sodium salicylate
and caffeine-sodium benzoate are the most important, and find applica-
tion in pharmacy.
Caffeine-sodium Salicylate.
This double salt is prepared by evaporating a solution of 5 parts of
caffeine and 6 parts of sodium salicylate in 20 parts of water. It is
a white, amorphous powder or a white, granular mass containing 43-8
per cent, of caffeine, and is soluble in 2 parts of water and in 50 parts of
alcohol (of about 85 per cent, by weight). On heating in a narrow test
tube white vapours smelling of phenol are evolved, and the residue
effervesces on treatment with acids. The aqueous solution even
when very dilute (i : looo) gives a blue-violet coloration with ferric
chloride. On warming the double salt with chloroform, the filtered
liquid yields a crystalline residue on evaporation, which may be identified
as caffeine.
^ For identifying reactions, cf. Merck's Reag.-Verz., 1908, p. 292.
CAFFEINE. CAMPHOR 323
Tests for Impurities.
An aqueous solution of caffeine-sodium salicylate (1:5) should be
colourless. The double salt should dissolve in concentrated sulphuric
acid without effervescence and to a colourless solution (sodium carbonate,
sugar).
Heavy Metals and SnlpJinric Acid. — The aqueous solution (i : 20)
should remain unchanged by sulphuretted hydrogen water and by
barium nitrate solution.
Hydrochlo7-ic Acid. — 2 c.c. of the solution (i : 20), to which 3 c.c. of
alcohol are added and then acidified with nitric acid, should not be
affected by the addition of silver nitrate solution.
Water. — Caffeine-sodium salicylate should not lose more than 5
per cent, in weight on drying at 100".
Quantitative Estimation of Caffeine.
A simple method of estimation consists in shaking up a solution of
I g. of caffeine-sodium salicylate in 5 c.c. of water, four times succes-
sively, with about 5 c.c. of chloroform, evaporating off the chloroform,
and weighing the residue after drying at 100". At least 0-4 g. of
caffeine should be found in the residue. By this method, the whole of
the content of caffeine is not found, since a portion is retained in the
aqueous solution.
Caffeine-sodium Benzoate.
Externally, this preparation does not differ from the preceding
double salt. The caffeine can be extracted with chloroform, and gives,
after evaporating off the solvent, the reactions given above. The
aqueous solution gives a flesh-coloured precipitate with ferric chloride.
Caffeine-sodium benzoate is prepared by evaporating down a solution
of 5 parts of caffeine and 5 parts of sodium benzoate in 10 parts of
water. The testing and quantitative estimation are carried out in
exactly the same manner as given above for caffeine-sodium salicylate.
Camphor (Japan Camphor).
CioHioO. Molec. wt. 152-13.
Camphor comes into commerce in white, transparent, tough, crystal-
line masses. For pharmaceutical purposes it is sold in the form of
balls, cubes, and also as " Flowers of Camphor." Crystallised from
alcohol it forms hard hexagonal crystals. It has a peculiar smell
and taste, and is difficultly soluble in water. According to the British
Pharmacopoeia the solubility is i : 700, according to Schmidt, i : 1200;
it dissolves readily in alcohol, ether, chloroform, acetone, benzene, acetic
acid, and carbon bisulphide, as well as in fatty and essential oils. Its
324 ORGANIC PREPARATIONS
sp. gr. is 0-985-0-996, the melting point 175° (according to J. E. Crane
and C. M. Joyce ^ iyg°'^), and the boiling point 204^ It burns
with a luminous, smoky flame. It is dextrorotatory in concentrated
alcoholic solution, and its specific rotatory power according to Landolt
is (0)0 = +55-4'
Tests for Impurities.
Non-volatile Matter. — On heating i g. of camphor, not more than
0-5 mg. of residue should remain.
"Artificial" Cavtphor {Terpene hydrochloride). — Japan camphor,
when rubbed with an equal quantity of chloral hydrate, should
give a syrupy liquid, whilst, according to Hirschsohn,^ " artificial "
camphor does not become liquid when treated in this manner.^ Since
" artificial " camphor contains chlorine it is readily identified. To test
for its presence 0-5 g. of the sample is stirred into a molten mixture of
potassium hydroxide and potassium nitrate, gently ignited, the cold melt
dissolved in nitric acid and water, and the solution made up to 50 c.c. ;
on the addition of silver nitrate solution no turbidity should be
produced.
Synthetic CampJior. — The synthetical preparation of camphor has
made such advances in recent }-ears that synthetic camphor has now
become a commercial product. It has the same chemical composition
as the natural product, but possesses different phj'sical constants which
serve for its identification. Natural camphor is dextrorotatory, gives
on oxidation with nitric acid an optically active camphoric acid melting
at 187", and gives the Borisch reaction (see below). Synthetic camphor
is optically inactive ; on oxidation it yields an optically inactive acid
melting at 202°-203°, and does not give the Borisch reaction. In
dealing with a mixture of natural and synthetic camphor, the optical
method is the only means of examination, the product to be examined
being compared optically with a genuine sample of Japan camphor, both
in solutions of equal concentration.
The alcoholic solution is most suitable for determining the specific
rotatory power. For a solution in benzene Landolt and Forster give
the following formula when using Laurent's apparatus at 20°: —
C=,.5-205[-.+7.+ ^54367-J,
in which C = the weight of camphor in grams per 100 c.c. of solution,
a — angle of rotation, and / = length of tube in decimetres.*
^ /. Soc. Chem. hid., 1907, 26, 386.
2 Pharm. Zeit.f. Russland, 1897, p. 161.
^ Cf. also B liley's and Dumont's reactions for ariificial camphor. Merck's Keag.-]'ers., 1908,
pp. 12 and 65.
* Cf. J. E. Crane and C. M. Joyce,/. Soc. Chem. Ind., 1907, 26, 386.
CAMPHOR 325
TJie Bon'sch Reaction. — On warming carefully 0-05 g. of camphor in a
test tube with i c.c. of vanillin-hydrochloric acid, as the temperature
gradually rises a rose-red coloration is first produced, which between
75°-ioo° changes to a greenish - blue. This reaction only takes place
with natural camphor ; synthetic camphor gives no coloration. The
test may be carried out in the cold as follows: — About o-i g. of
camphor is treated on 2 watch-glass with 10 drops of a cold
mixture of equal volumes of vanillin -hydrochloric acid (i g. of
vanillin in 100 g. of 25 per cent, hydrochloric acid), and concen-
trated sulphuric acid added. A yellow coloration is at first pro-
duced, and in the course of half an hour to one hour in the case
of natural camphor this changes to a dirty green coloration, and
in the course of another hour to a pure dark green, and after seven
to eight hours to an indigo -blue colour. (Impurities in natural
camphor mask the reaction.) Synthetic camphor treated in a similar
manner only shows the initial yellow coloration, which disappears at
the end of an hour.^
The oxidation of camphor is carried out as follows: — 5 g. of camphor
are placed in a small^ flask fitted with a long vertical glass tube
or upright Liebig's condenser, and heated on the boiling water-bath for
about fifty hours with a mixture consisting of 24 c.c. of nitric acid
(sp, gr. I 42) and 16 c.c. of water. The camphoric acid which has
separated is then collected, washed with cold water, recrystallised from
hot water, converted into the sodium salt, again separated by the
addition of hydrochloric acid and recrystallised several times from hot
water. As stated above, natural camphor yields by this treatment an
acid melting at 187°, whilst synthetic camphor yields an acid melting at
2O2°-203°, or, as is frequently the case, no acid at all, owing to the
oxidation having proceeded too rapidly.^
Carbon Bisulphide.
CSg. Molec. wt 76-14.
Carbon bisulphide is a colourless, bright, neutral, highly refractive,
easily inflammable liquid, having a sp. gr. of i-270-i-272, and a boiling
point of 46°-47°.
Tests for Impurities.
Pure carbon bisulphide contains generally only sulphur as an
impurity, which is found in traces in practically all of the purest
commercial brands. On evaporating 50 c.c. of carbon bisulphide on
^ Pharm. Zentralh.y 1907, 48, 527 and 777 ; J. Soc. Chem. Ind.^ 1907, 26, 1065.
"^ Cf. Deussen, Arch. Pharm., 1909, 247, 3 1 1. On testing synthetic camphor, cf. A. Baselli,
J. Soc. Chem. Ind.y 1907, 26, 431.
326 ORGANIC PREPARATIONS
the water-bath, only a trace of sulphur should remain. On shaking
carbon bisulphide with lead carbonate, the latter should not be turned
brown (absence of sulphuretted hydrogen).
Sulpliuric and Sulphurous Acids. — On shaking lo c.c. of carbon
bisulphide with 5 c.c. of water, the latter should neither redden nor
bleach blue litmus paper.
Quantitative Estimation.
A quantitative estimation of carbon bisulphide is usually not
necessary if the sample conforms to the tests given above. If, however,
a quantitative valuation be required, the method based on A. \V.
Hofmann's xanthate reaction may be used.^ A weighed quantity
of carbon bisulphide is added to alcoholic potassium hydroxide, and
after allowing to react for a short time the mixture is acidified with
acetic acid and insoluble cuprous xanthate (a yellow crystalline pre-
cipitate) precipitated by the addition of copper sulphate. The con-
tained copper may be estimated either volumetrically according to
Grete- and Macagno,^ or weighed as cupric oxide. From the weight
of copper found the value of the carbon bisulphide may be calculated,
since one equivalent of copper corresponds to two equivalents of carbon
bisulphide.*
Carbon Tetrachloride.
CCI4. Molec. wt. 153-84.
Carbon tetrachloride is a colourless liquid, sparingly soluble in water
(about o-o8 to 100), miscible in all proportions with absolute alcohol,
ether, fatty and essential oils. Its sp. gr. is 1-604, ^^^^ its boiling point
76°-77°.
Tests for Impurities.
Non-volatile Matter. — On evaporating 25 c.c. of carbon tetrachloride
on the water-bath, no appreciable residue should be left.
Chlorine. — No blue coloration should be produced on shaking 20 c.c.
of carbon tetrachloride with 5 c.c. of zinc iodide-starch solution.
Hydrocliloric Acid. — 20 c.c. of carbon tetrachloride are shaken with
10 c.c. of water for about one minute. The separated water should not
react acid and should show no reaction with silver nitrate solution.
Organic Impurities. — On shaking 20 c.c. of carbon tetrachloride
frequently during one hour with 15 c.c. of concentrated sulphuric acid in
» Cf. section on "Coal Tar," Vol. II., Part II., p. 796.
2 Z. anal. Chem., 1882, 21, 133. ' Ibid.
* Cf. A. Goldberg, Z. angrw. Chem., 1899, 12, 75 ; /. Soc. Ch<m, Ittd., 1889, 18, 304.
CARBON TETRACHLORIDE 327
a stoppered glass vessel, previously rinsed out with sulphuric acid, the
sulphuric acid should not become coloured.
Aldehyde. — If a mixture of lo c.c. of carbon tetrachloride and lo c.c.
of potassium hydroxide solution (1-3) be warmed for about one minute
and frequently shaken during the warming, the potassium hydroxide
should not become either yellow or brown in colour.
Carbon Bisulphide. — 10 c.c. of carbon tetrachloride are mixed with 10
c.c. of a solution of 10 g. of potassium hydroxide in 100 c.c. of absolute
alcohol. After standing for one hour, 5 c.c. of dilute acetic acid (sp. gr.
I-04-I-042) and copper sulphate solution are added. No yellow
precipitate should separate within two hours.
Any carbon bisulphide present may be quantitatively determined by
the iodometric method worked out by L. G. Radcliffe,^ as an applicable
modification of Gastine's form, of the xanthate reaction. The method is
based on the conversion of the carbon bisulphide into xanthic acid by
means of alcoholic potash, separating it by the addition of acetic acid,
and titrating with iodine solution, whereby it is oxidised to ethyl dithio-
dicarbonate. To carry out the determination, 25 c.c. of alcoholic potash
are run into a flask of suitable size, and the flask loosely closed with a
cork and tared ; i c.c. of the carbon tetrachloride under examination is
then run in from a pipette and the total weight accurately determined.
After five minutes, dilute acetic acid is added until the mixture reacts
faintly acid (discoloration of phenolphthalein), the contents of the flask
cooled, and solid sodium bicarbonate added in excess. The milky,
turbid mixture is titrated with Njio iodine solution after the addition
of starch solution. One molecule of xanthic acid corresponds to one
atom of iodine, as shown in the following equation : —
/OC2H5
2CS<( +I2 = S,(CS.OC2H5)2+2HI.
\5J^ Ethyl dithio-dicarbonate
Xanthic acid
Casein.
Casein, an albuminoid constituent of milk, is a fine, white or
yellowish-white powder, insoluble in water and in alcohol. Sprinkled
on moist blue litmus paper, the latter is turned red. It is soluble in
aqueous solutions of the alkali hydroxides and alkaline earths, as well as
in alkaline carbonates, and is precipitated out from these solutions by
acids. Excess of alkali converts it into albuminate. On artificial
digestion in 02 per cent, hydrochloric acid with pepsin at about 40°,
the clear solution of casein gradually becomes turbid owing to the
separation of nuclein.
^ /. Soc. Chem. I>id., 1 909, 28, 229.
328
ORGANIC PREPAKATIONS
According to Scherer ^ and O. Hammarsten - the elementary com-
position of casein is as follows : —
Scherer.
Hammarsten
Per cent.
Per cent.
Carbon . . . .
54-02
52-96
Hydrogen
7-33
7-05
Nitrogen
15-52
15-65
Sulphur .
075
0-71
Phosphorus
• • •
0-85
Oxygen .
22-38
22-78
Phosphorus is a constituent of casein itself, though it was formerly
assumed to be only a constituent of the contained mineral matter left
on ignition.
Tests for Impurities.
Inorganic Matter. — On burning i g. of casein in free access of air,
only a trace of ash should remain behind. The purest casein yields
up to 0-5 per cent, of ash (according to Hammarsten up to 1-2 per
cent), commercial casein as much as 6 per cent, and the purest casein
from plants up to i per cent In judging casein, these figures for
the percentage of ash may generally be considered as the maxima.
Sodium casein sometimes comes on to the market under the designa-
tion of casein. The salt is readily recognised by its solubility in water
and high percentage of ash (sodium carbonate).
Fat. — 10 g. of casein are well shaken frequently for one hour with
100 c.c. of ether, 50 c.c. of the ethereal extract filtered through a dry
filter paper into a small weighed flask, well covering the funnel to avoid
loss of ether by evaporation, and the ether evaporated off on the water-
bath. The residue is then dried for two hours at 90"- 100'' and weighed.
Good casein should not contain more than o-i per cent of fat In the
purest casein up to 0-07 per cent., in commercial casein up to 0-09 per
cent, and in casein from plants up to o-oi per cent, of fat will be found.
Free Acid {^Acetic Ada). — The purest casein should contain no free
acid, which, however, is frequently not the case with commercial
products. On shaking 10 g. of casein with 100 c.c. of water, the filtrate
should react only slightly acid ; 50 c.c. of the filtrate may be titrated
with TV/ 10 potassium hydroxide, using phenolphthalein as indicator. A
good sample should not require more than 05 c.c. of the iV/io
potassium hydroxide to produce a red coloration.
Quantitative Estimation.
This may be carried out by determining the content of nitrogen
either by Dumas' or Kjeldahl's method. Taking the nitrogen con-
1 Annalen^ 1841, 40, 41.
2 Z. physiot. Chem., 1882-3, 7, 269; c/. also Tangl, PJliiger's Arckiv der Physiol., 1908,
121, S34-
CATECHOL 329
tent of milk albumin as 14-3 per cent, the calculation used in the
analysis of casein is to multiply the percentage of nitrogen found in
the sample under examination by 6-99. A good sample of casein is
expected to give a value of 100 when multiplied by this factor.
According to H. D. Richmond^ the Kjeldahl method is better and
more reliable than the Dumas method for the estimation of nitrogen in
casein. Experimental results gave a mean value of 15-65 per cent, of
nitrogen in casein, corresponding to the factor 6-39.
Catechol (Pyrocatechin).
OH(i)
CgHZ . Molec. wt. 110-05.
^OH(2)
Catechol forms colourless, glistening, slightly odourous, rhombic
scales or columnar crystals, readily soluble in ether, alcohol, benzene,
chloroform, and water. The aqueous solution reacts acid. It melts at
104°, and boils at 240°-245°.
An aqueous solution of catechol gives a green coloration with ferric
chloride ; on the addition of a little sodium hydroxide the colour
changes to violet, and with excess to deep red. Silver nitrate is
reduced by catechol in the cold, but Fehling solution is only reduced
on heating. The aqueous solution is precipitated by lead acetate as
well as by the basic acetate. This differentiates catechol from resor-
cinol and quinol ; resorcinol in aqueous solution is precipitated by basic
lead acetate, but not by the normal acetate, whilst quinol is precipitated
by neither of these reagents.-
Tests for Impurities.
Inorganic Matter. — i g. of catechol should not leave more than 0-5
mg. of residue on ignition.
Phenol. — On boiling an aqueous solution (i:io) it should not be
possible to recognise the smell of phenol.
Foreign Organic Matter. — Catechol dissolves in sulphuric acid
producing a faint rose coloration ; no darkening of the sulphuric acid
should take place.
Quantitative Estimation.
0-5 g. of catechol is dissolved in 50 c.c. of water and a concentrated
aqueous solution of lead acetate gradually run in, the contents of the
beaker being kept agitated during the addition. After allowing the
white precipitate (CgH^OgPb) to settle, a few more drops of lead acetate
1 Analyst, 1908, 33, 1 79.
2 For colour reactions, cf. Chem. Zentr., 1898, II., 1282 ; Z. anal. Chem., 1889, 28, 252, and
1895, 34. 235-
330 ORGANIC PREPARATIONS
solution are added in order to see if the precipitation is complete, and
the precipitate is then collected on a weighed filter paper. After
washing several times with water, the precipitate is dried at lOO and
weighed. The result obtained may be checked by igniting the
precipitate, dissolving in nitric acid, diluting the solution with water,
precipitating the lead as sulphate and weighing it as such.
I g. PbC^H^Oo corresponds to 03494 g. of catechol; i g. of lead
sulphate corresponds to 0-3632 g. of catechol.
Chloral Hydrate.
CCI3COH . H,0. Molec. wt. 165-40.
Chloral hydrate forms colourless, transparent, monoclinic cr}'stals,
which soften at 49" and melt at 53". It dissolves readily in water,
alcohol, and in ether, but only sparingly and slowly in benzene, chloro-
form, petroleum spirit, and carbon bisulphide. In aqueous solution it
reacts slightl}- acid, whilst in other solvents it has a neutral reaction.
On treating chloral hydrate with potassium hydroxide solution,
chloroform is produced.^ The following test serves to differentiate
between chloral hydrate and but\l-chloral hydrate : — On treating chloral
hydrate with a solution of pyrogallol in concentrated sulphuric acid, the
mixture remains colourless in the cold, but on warming carefully and
gently a fine blue coloration is produced ; butyl-chloral hydrate treated
in a similar manner yields a wine-red coloration.^
Tests for Impiirities.
Inorganic Matter. — i g. of chloral h)-drate should leave no appreci-
able residue on ignition.
Hydrochloric Acid. — An alcoholic solution of chloral hydrate (i : 10)
should not show any immediate turbidity with silver nitrate solution,
and should not redden blue litmus paper.
Chloral Alcoholate. — On pouring i c.c. of commercial nitric acid over
I g. of chloral hydrate in a porcelain dish, no yellow coloration should
be produced at the ordinary temperature, or on warming for from three
to four minutes on the water-bath, and also no yellow vapours should
be evolved even on warming for ten minutes. The British Pharma-
copceia gives the following test : — When r g. of chloral hydrate is
warmed with 6 c.c. of water and 0-5 c.c. of potassium hydroxide solution,
the mixture filtered, sufficient iodine solution added to impart a deep
brown colour, and the whole set aside for an hour, no precipitate of
iodoform should result.
* For identifying and colour reactions of chloral hydrate, cf. Merck's Reag.-Verz,, 1908, p.
292.
- Pharm. Zeit., 1 904, p. 91.
CHLORAL HYDRATE 331
Foreign Organic Matter. — i g. of chloral hydrate when shaken up
with 10 c.c. of sulphuric acid in a glass vessel previously rinsed out with
sulphuric acid should not discolour the acid within one hour. Chloral
hydrate required for medicinal purposes should conform to the following
more exacting test: — If 2 g. of chloral hydrate are dissolved in 10 c.c.
of sulphuric acid (sp. gr. 1-84) in a glass-stoppered flask previously
rinsed out with sulphuric acid, and 4 drops of formaldehyde (40 per
cent.) added, the mixture should not become discoloured within half
an hour.^
Quantitative Estimation.
Potassium hydroxide, even in the cold, decomposes chloral hydrate
quantitatively into chloroform and potassium formate : —
CCI3COH.H2O + KOH = CHCI3+H.COOK + H2O.
To carry out the estimation based on this decomposition 5 g. of chloral
hydrate are dissolved in 50 c.c. of N\i potassium hydroxide, phenol-
phthalein added, and the excess of alkali immediately titrated with N\\
hydrochloric acid. In order to arrive at the content of chloral hydrate
in the 5 g. of the sample taken, the number of cubic centimetres of
Nil potassium hydroxide used for the reaction is multiplied by 0-1654.
Should the chloral hydrate contain free hydrochloric acid, 10 g. of the
sample are treated in a 100 c.c. measuring flask with 0-5 g. of calcium
carbonate and 50 c.c. of water, and the mixture well shaken for some
minutes. The flask is then filled up to the mark with water, the con-
tents well mixed and filtered, and 50 c.c. of the filtrate are then treated
with 50 c.c. oi Nji potassium hydroxide, as given above.
T. E. Wallis^ gives the following method :— o-i g. of chloral hydrate
is dissolved in 10 c.c. of alcohol, 10 c,c. of NJi sodium hydroxide added,
and the mixture heated in a suitable bottle, closed with a rubber cork
which is securely tied down, for three hours in the water-bath. The
resulting mixture is neutralised with vV/i sulphuric acid, using phenol-
phthalein as indicator, and the sodium chloride formed in the reaction
titrated with Njio silver nitrate solution. The calculation is made
according to the following equation : —
CCl3CH(OH)2-f5NaOH = 3NaCl + 2H . COONa + sHp.
Not less than i8-i and not more than 18-3 c.c. of Njio silver nitrate
solution should be required.
The estimation of the contained chlorine is also made use of in the
method of valuation devised by P. A. W. Self'' This consists in heat-
ing 0-3 g. of chloral hydrate with i-o g. of aluminium powder (or 2-5 g.
1 Merck's Ja/iresber., 1910, p. 150. ^ P/mrm.J., 1906, 76, 162.
3 Ibid., 1907, 79,4.
332 ORGANIC PREPARATIONS
of zinc filings), 15 c.c. of glacial acetic acid, and 40 c.c. of water for half
an hour under a reflux condenser. The mixture is then filtered, and,
after washing, the chlorine in the solution is determined either gravi-
metrically as silver chloride, or volumetrically by adding excess of ^V/io
silver nitrate solution, filtering, and titrating the excess of silver with
ammonium thiocyanate.
E. Rupp^ gives the following iodometric method of estimation : — 25
c.c. of A^jio iodine solution and 2-5 c.c. of N/i potassium hydroxide
solution are run into a glass-stoppered flask. 10 c.c. of a i per cent,
chloral hydrate solution are added to the above mixture, and the
contents of the flask allowed to stand for from five to ten minutes.
After diluting with about 50 c.c. of water and adding 5 c.c. of hydro-
chloric acid (25 per cent.), the solution is titrated with N/io sodium
thiosulphate solution. From 12-9- 13- 5 c.c. should be required, which
correspond to 100-95 per cent, of chloral hydrate. The decomposition
takes place according to the following equation : —
CCl3CH(OH),-f U = 2HI-fC0.3 + CHCl3.
I c.c. of the iodine solution is therefore equal to 000827 g. of chloral
hydrate.
Chloroform.
CHCI3. Molec. wt. 119-39.
Chloroform is a clear, colourless liquid, possessing a characteristic
smell. The purest chloroform has a sp. gr. of 1-502, and boils at 62°;
C. Baskerville and W. Hamor give the boiling point of specially purified
chloroform as 6i°-2, and the sp. gr. at I574° as 1-49887.- The chloroform
of the British Pharmacopoeia is prepared by the addition of sufficient
absolute alcohol to produce a liquid having a sp. gr. of not less than
1-490 and not more than 1-495. That of the German Pharmacopceia
contains an addition of i per cent, of alcohol and has a sp. gr. of from
I-485-I-489, and boils between 6o°-62°. The addition of alcohol makes
the preparation more stable.^
Chloroform is only slightly soluble in water (i : 200) ; it is miscible
in all proportions with alcohol, ether, carbon bisulphide, fatty and
essential oils. On warming chloroform with potassium hydroxide and
acetanilide, the disagreeable odour of isonitrile is produced.
Tests for Impurities.
Inorganic and noti-volatile Orgafiic ]\ fatter. — On evaporating 25 c.c.
of chloroform, no appreciable residue should be left.
1 Arch. P/iarm., 1903, 241, 326 ; /. Soc. Chem. Ind., 1903, 22, 1019.
2 /. Ind. Eng. Chem., 1912, 4, 212 ; /. Soc. Chem. Ind., 1912, 31, 840.
^ On the value of alcohol for increasing the stability of chloroform, cf. Adrian, J. Pharm,
Chim., 1903, 18, 5 ; /. Soc. Chem. Ind., 1903, 22, 879.
CHLOROFORM 333
Hyd7-ocJiloric Acid. — On shaking 20 c.c. of chloroform with 10 c.c. of
water for about a minute, the separated water should not redden blue
litmus paper, and when poured on to silver nitrate solution the line of
separation of the two layers of liquid should show no turbidity.^
Chlorine. — On shaking 20 c.c. of chloroform with 5 c.c. of zinc iodide-
starch solution, the chloroform should not become coloured nor the
starch solution turned blue.
Foreign Orgattic Matter. — 20 c.c. of chloroform, 1 5 c.c. of concentrated
sulphuric acid, and 4 drops of formaldehyde solution (40 per cent.) are
shaken together in a glass-stoppered flask previously rinsed out with
sulphuric acid ; the sulphuric acid should not become discoloured
within half an hour.^
Carbonyl Chloride. — The smell of chloroform should not be irritating.
20 c.c. of chloroform are treated with a solution of 3 drops of aniline in
5 c.c. of benzene. In the presence of carbonyl chloride either a tur-
bidity or a crystalline precipitate of phenyl urea is produced.^ On
adding clear baryta water to 10 c.c. of chloroform, no white film should
be produced at the junction of the two layers of liquid.
Alcohol — Chlorofornj free from alcohol should not discolour
potassium permanganate solution. According to H. Hager, a some-
what high content of alcohol may be detected by shaking up chloroform
with a mixture of 4 vols, of glycerol and i vol. of water in a graduated
cylinder. The content of alcohol can be gravimetrically estimated by a
method given by M. Nicloux.*
Aldehyde. — If 10 c.c. of chloroform and 10 c.c, of potassium hydroxide
solution are warmed together for about a minute, no yellow or brown
coloration should result.
The following scheme for the examination of chloroform for
anaesthetic and analytical purposes, with particular reference to the
detection of avoidable impurities, has been worked out by C. Baskerville
and W. Hamor, as the result of an extended investigation of the subject.^
" Anaesthetic chloroform " is the term given to chloroform complying
with pharmacopoeial requirements ; it contains ethyl alcohol (up to i
per cent.) and small quantities of water, " Commercial chloroform "
contains at least 99 per cent., by weight, of chloroform, but may contain
small amounts of " organic impurities."
I. Specific gravity is determined by means of a pyknometer at 15°.
' On the decomposition of chloroform by air and light, cf. W, Ramsay, y. Soc. Chem. Ind.,
1892, II, 772 ; also, Ber. der deutsch. pharm. Ges. Berlin, ISOS, p, 387, and C, Baskerville and
W, Hamor,/. Soc. Chem. /nd., 1912, 31, 840.
2 On the preservation of chloroform for anaesthetic purposes, cf. Merck's Jahresher,, 1902, p.
43 ; also, Z. angezv. Chem., 1910, 23, 1546,
^ Scholvien, Pharm. Zetitralh., 34, 611,
* Bull. Soc, Chim., 1906, 35 330 ; J. Soc. Chem. hid., 1906, 25, 611.
5 /. Ind. Eng. Chem., 1912, 4, 212, 278, 362, 422, 499, 571 ; /. Soc. Chem. Ind., 1912, 31, 839,
334 ORGANIC PREPARATIONS
2. Odour. — lOO c.c. are slowly evaporated to about lo c.c. on the
water-bath. The residue from anctsthetic chloroform should be colour-
less and possess no foreign odour, and when allowed to evaporate on
filter paper, no odour of other substances than alcohol and chloroform
should be perceptible as the last portions disappear. (In the case of
pure chloroform, no odour except that of chloroform should be
observed.)
3. Residue. — No appreciable residue should be left when 100 c.c.
of pure or anaesthetic chloroform are evaporated in a platinum dish
at 100°.
4. Organie Impurities. — 20 c.c. of the sample are mixed with 15 c.c.
of concentrated sulphuric acid in a glass-stoppered tube of 50 c.c.
capacity, and after the addition of 0-4 c.c. of pure 40 per cent, form.al-
dehyde solution, the whole is shaken for five minutes. No coloration
should be produced with anaesthetic chloroform, and with pure chloro-
form no coloration should be produced even on allowing to stand for
one hour in the dark.
5. Water. — When 20 c.c. of the sample are boiled with i g. of clean
crystals of calcium carbide, and the vapours evolved passed into
ammoniacal silver nitrate solution, no acetylene reaction should result
in the case of pure chloroform or anhydrous anaesthetic chloroform.^ In
the case of anaesthetic chloroform, 10 c.c. should dissolve to a clear
solution when shaken with an equal volume of paraffin oil of sp.
gr. o-88o.
6. Alcohul. — For pure chloroform, 10 c.c. arc extracted with succes-
sive portions of 4 c.c, 4 c.c, and 2 c.c. of concentrated sulphuric acid,
the acid solution is diluted with 40 c.c. of water, and gently distilled
until 20 c.c. have passed over. 10 c.c. of the distillate are treated with
6 drops of a 10 per cent, solution of potassium hxdroxide, warmed to
50", and treated with a saturated solution of iodine in potassium iodide
until it becomes permanently brown, when it is carefully decolorised
with potassium hydroxide; no iodoform should be deposited. A
negative result with this test indicates the absence of alcohol, acetalde-
hyde, propyl alcohol, acetone, etc. Tests with chromic acid,'- alkaline
permanganate,^ and potassium hydroxide (agitation of the sample first
with ignited potassium carbonate to remove water, and then with a small
piece of fused potassium hydroxide and red litmus paper ; the latter
becomes blue in presence of alcohol) may be used for confirmatory
purposes. In the case of anaesthetic chloroform and commercial chloro-
form, the amount of alcohol present should be determined by the method
of Nicloux* as modified by the authors (shaking the chloroform for at
least ten times in succession with twice its volume of water and using a
1 Cf.y. Soc. Chem. hid., 1898, 17, 864. - Cf, Ihid., 1896, 15, 748.
3 Cf. Ihid., 1882, 1, 117. •• Cf. IbiJ., 1906, 25, 611.
CHLOROFORM 335
portion of the combined aqueous extracts for the determination), or by
Behal and Frangois' method.^
7. Acetone. — For pure chloroform see (6). For anaesthetic chloroform
10 c.c. are agitated with 5 drops of a 0-5 per cent, solution of sodium
nitroprusside and 2 c.c. of ammonia of sp. gr. 0-925, and the mixture
allowed to stand for several minutes. When acetone is present,
the supernatant liquid acquires an amethyst colour. The test should
also be applied to the first 10 per cent, of distillate and the 10 per cent,
of residue obtained on slowly distilling lOO c.c. of the sample. If the
proportion of acetone is as low as i : lOOO, the amethyst colour is
not distinct until the mixture of chloroform with ammonia and sodium
nitroprusside is saturated with ammonium sulphate, shaken, and then
allowed to stand for five minutes. In all cases a blank test should be
made with pure chloroform for comparison.
8. Acetaldchyde. — With chloroform of all grades, no coloration should
be produced even after fifteen minutes when 5 c.c. are agitated with 5
c.c. of Francois' reagent (22 c.c. of sulphurous acid, 30 c.c. of i : 1000
rosaniline acetate solution, and 3 c.c. of sulphuric acid). For pure
chloroform, in addition to test (6), no coloration should be produced
when 5 c.c. are shaken with 5 c.c. of Nessler's reagent and the mixture
allowed to stand for five minutes. For anaesthetic chloroform, 10 c.c.
are shaken with 10 c.c. of water and 5 drops of Nessler's reagent, and
the mixture allowed to stand for five minutes ; no precipitate should
be produced, and the reagent should not become coloured, although it
may become opalescent or slightly turbid.
9. Acidity. — 20 c.c. of the sample are thoroughly agitated with
10 c.c. of water and 2 drops of phenolphthalein solution, and then
titrated with N/ioo potassium hydroxide solution ; in the case of either
pure or anaesthetic chloroform, not more than o-2 c.c. of the alkali solu-
tion should be required to produce a faint but decided alkaline reaction
permanent for fifteen minutes, when the mixture is shaken for thirty
seconds after the addition of each drop of alkali.
10. Decomposition Products of Pure Chloroform. — A dry stoppered
tube of 25 c.c. capacity, containing 15 c.c. of the sample, is filled with a
clear solution of barium hydroxide (1:19) and allowed to stand for three
hours in the dark, without agitation ; the formation of a film of barium
carbonate indicates the presence of carbonyl chloride. In addition to
test (9), both pure and anaesthetic chloroform should comply with the
following test : — When 10 c.c. are agitated with 5 c.c. of water for five
minutes, the aqueous extract should not become turbid or give any
precipitate on addition of silver nitrate solution (absence of hydrochloric
acid, chlorides, etc.), and no reduction should occur on warming (absence
of acetaldchyde, formic acid and formates, etc.). With chloroform of all
1 Cf./. Soc. Cliem. hid., 1897, 16, 566.
336 ORGANIC PREPARATIONS
grades, no liberation of iodine, as indicated by addition of starch
solution, should result when lo c.c. are shaken during fifteen minutes
with 10 c.c. of a lo per cent, solution of cadmium potassium iodide
(absence of chlorine and hydrogen peroxide).
II. Dccoviposition Products of AficBslhelic Chloroform. — For the
detection of acetaldehyde see (8). If the sample fails to comply with
test (9) and contains none of the impurities referred to under (10), the
presence of acetic acid is indicated, and the sample should be rejected.
For the detection of chlorinated derivatives of the oxidation products of
alcohol, 20 c.c. of the sample are shaken during twenty minutes with
15 c.c. of concentrated sulphuric acid, and 2 c.c. of the mixture are
diluted with 5 c.c. of water ; the liquid should remain colourless and
clear, and should possess no odour foreign to anaesthetic chloroform
(chloroform and alcohol) ; it should remain colourless when further
diluted with 10 c.c. of water, and its transparency should not be
diminished on addition of 5 drops of silver nitrate solution.
Quantitative Estimation.
Chloroform may be estimated either volumetrically by the method
given by L. de Saint-Martin,^ or iodometrically according to the
method due to G. Vortmann.^
Cinnamic Acid.
CgHg . CH : CH . COOH. Molec. wt. 148-06.
Cinnamic acid crystallises in colourless, odourless needles or rhombic
prisms which melt at 133' and boil at 300° with partial decomposition.
It dissolves in about 3500 parts of cold water, more readily in boiling
water, in 4-5 parts of alcohol, in 17 parts of chloroform, and in no parts
of carbon bisulphide. On warming o-i g. of cinnamic acid in the water-
bath with 20 c.c. of potassium permanganate solution (i : 1000), a smell
of benzaldehyde is produced.
Tests for Impurities.
Inorganic Matter. — On igniting i g. of cinnamic acid not more than
0-5 mg. of residue should remain.
SuIpJiuric and HydrocJdoric Acids. — Neither barium nitrate nor
silver nitrate solutions should show any reaction with a solution of i g.
of cinnamic acid in 25 c.c. of boiling water.
Foreign Organic or Resinous Matter. — On dissolving i g. of cinnamic
acid in hot sulphuric acid, at most only a light yellow coloration and not
a brown coloration should result.
Benzoic Acid. — On thoroughly shaking i g. of cinnamic acid with
^ CompUs rend., 1888, 106, 492 ; /. Chem. Soc. Aislr., 1888, 54, 570.
^ Anleiluno zur chemischen Analyse organischer Stoffe, 1891, pp. 102 and 401.
CHLOROFORM. CITRIC ACID 337
lOO c.c. of water at 20° at intervals during one hour, and filtering, 50 c.c.
of the filtrate should not require more than 1-4 c.c. of N/io sodium
hydroxide for neutralisation, using phenolphthalein as indicator. At
20°, cinnamic acid is soluble to the extent of i : 2400, and benzoic acid
of I : 360. Treated as above, benzoic acid yields a filtrate, 50 c.c. of
which require ii-2 c.c. of N/io sodium hydroxide for neutralisation.
Traces of benzoic acid in cinnamic acid cannot be detected by this
method, which only detects quantities over i per cent.
A sample containing i per cent, of benzoic acid, treated as above,
requires i-6 c.c. of iV/ 10 sodium hydroxide for neutralisation. According
to A. W. de Jong^ the benzoic acid in cinnamic acid may be determined
by converting the cinnamic acid into phen}'ldibromopropionic acid,
which does not volatilise at loo^ The mixture of the two acids
(about 2 g.) in carbon bisulphide is treated with bromine, and after
allowing to stand for twenty-four hours the carbon bisulphide and
excess of bromine are distilled off; the residue is taken up with ether,
the ethereal solution evaporated at the ordinary temperature, the
residue dried m vacuo over sulphuric acid, then powdered and heated
to loo^ The residual phenyldibromopropionic acid is weighed, and
the content of benzoic acid thus obtained by difference. By determining
the bromine in the residual substance and the quantity of sublimed
benzoic acid, the presence of other substances in the mixture can be
detected.
Quantitative Estimation.
I g. of cinnamic acid is dissolved in 10 c.c. of N\\ sodium hydroxide
and some water, and titrated with iVyi hydrochloric acid, using phenol-
phthalein as indicator, i c.c. of sodium hydroxide neutralised corre-
sponds to 0-1481 g. of cinnamic acid.
Citric Acid.2
CgHsOy-t-HgO. Molec. wt. 210-08.
Citric acid crystallises in large, colourless, rhombic prisms, which
do not effloresce in dry air at the ordinary temperature, but which lose
their water of crystallisation completely at 100° ; in a damp atmosphere
the crystals become moist superficially. The crystallised acid has no
fixed melting point, since it fuses together at 70°-75°, but the
anhydrous acid melts at I53''-I54°. Citric acid dissolves in 0-75 parts
of cold water, in 0-5 parts of boiling water, in i part of alcohol
(about 85 per cent.), and in about 50 parts of ether. On dissolving
1 Rec. trav. chim., igog, 28, 342 ; igir, 30, 223 ; /. Soc. C/iem. Ind., 1910, 29, 112; 1911,
30, 1407.
- Cf. the section on " Citric Acid," this Vol., pp. 296 et seq.
Ill Y
338 ORGANIC PREPARATIONS
oi g. of the acid in i c.c. of water and adding 40-50 c.c. of lime water
(the solution must react alkaline), a white flocculent precipitate is
formed on boiling ; on cooling the solution, the precipitate redissolves
within three hours.
Tests for Impurities.
Inorganic Matter. — I g. of citric acid should leave no appreciable
residue on ignition.
Calcium Citrate. — No precipitate should be produced on adding
ammonium oxalate solution to 20 c.c. of an aqueous solution of the
acid (i : 10) containing excess of ammonia.
Lead ; Copper ; Iron. — A solution of 5 g. of citric acid in 10 c.c.
of water, nearly neutralised with ammonia so that the solution only
reacts faintly acid (12 c.c. of sp. gr. 096), should remain unchanged on
treatment with sulphuretted hydrogen.
Sulphuric Acid. — 20 c.c. of an aqueous solution of citric acid (i : 10)
should give no turbidity with barium chloride solution.
Sugar ; Tartaric Acid; Oxalic Acid. — A mixture of i g. of citric acid
and 10 c.c. of sulphuric acid, prepared in a porcelain mortar previously
cleaned with sulphuric acid, when heated in a test tube in a boiling
water-bath for one hour, should not darken and at most only turn
yellow.
I g. of citric acid dissolved in 2 c.c. of water should not become
turbid on the addition of 10 drops of potassium acetate solution and
5 c.c. of alcohol, and on standing for two hours no crystalline precipitate^
should separate.^
Quantitative Estimation.
I g. of crystallised citric acid (with iHoO) requires 14-3 c.c. of N\i
potassium hydroxide for neutralisation. i c.c. of N\i potassium
hydroxide corresponds to 007003 g. of citric acid. Phenolphthalein is
used as indicator.
Cocaine Hydrochloride.
Ci,H,iO,N . HCl. Molec. wt. 339-65.
Cocaine hydrochloride forms colourless, prismatic crystals which
decompose on melting at 183^ It is readily soluble in water and in
alcohol. Applied to the tongue, solutions of cocaine hydrochloride
produce' temporary insensibility. On heating i g. of cocaine h}'dro-
chloride to about lOO^ for five to ten minutes with 10 c.c. of sulphuric
acid, and carefully mixing the resulting product with 20 c.c. of water,
^ For reactions for the detection of tartaric acid in citric acid, c/^ also -l/tvcX'j Reag.-Verz.y
1908, p. 302.
COCAINE 339
the smell of methyl benzoate may be recognised and a considerable
separation ot benzoic acid occurs. On treating an aqueous solution
of cocame hydrochloride with a few drops of nitric acid and silver
nitrate solution, a white precipitate of silver chloride is produced.^
Tests for Impurities.
Inorganic Matter.-Ou igniting 0-5 g. of cocaine hydrochloride not
more than 0-5 mg. of residue should remain.
Free Hydrochloric Acid.-An aqueous solution of cocaine hydro-
chloride should react neutral.
Cinnamyi Cocaine and Organic Impurities.— According to the British
Pharmacopoeia a solution containing not less than i per cent of
cocaine gives a copious red precipitate with an excess of a solution
ot potassium permanganate which should not change colour within
an hour. The German Pharmacopoeia prescribes the following test •—
A solution of o-i g. of cocaine hydrochloride in 5 c.c. of water and 3
drops of dilute sulphuric acid should assume a violet coloration on the
addition of 5 drops of potassium permanganate solution (i : 1000) In
the absence of dust, the coloration should show but little signs of fadin-
in the course of half an hour. "^
Perfectly pure cocaine hydrochloride conforms to the following
test:— On dissolving o-i g. of cocaine hydrochloride in 5 c.c. of water
and adding i drop of potassium permanganate solution (i : 1000) the
pink coloration should not fade within fifteen minutes. As a standard
for comparison, i drop of potassium permanganate is added to :; cc of
water.
It is of importance that the test tubes used for the above reactions
are scrupulously clean.
Foreign Alkaloids.-On adding 10 drops of 3 per cent, chromic acid
solution to an aqueous solution of cocaine hydrochloride (o-i : 10) the
addition of each drop produces a yellow precipitate which redissolves
immediately; on the addition of 2 c.c. of hydrochloric acid (sp gr
1-124) the precipitate is reformed. ^ i- & •
G. L. Schaefer^ has proposed the following test, based on the
relative greater solubility of cocaine chromate as compared with
that of the chromates of the other coca bases, in presence of
hydrochloric acid :— 0-05 g. of cocaine hydrochloride is dissolved in
20 C.C. of water, 5 c.c. of a 3 per cent, chromic acid solution and
5 cc. of 10 per cent, hydrochloric acid (at 15°) added; if the cocaine
hydrochloride is pure, the solution remains clear, and the more foreign
coca bases are present the greater is the turbidity produced. The
1 For identifying reactions, cf. Merck's Reag.-Verz., 1908, p. 29J.
2 pi,ar,n.J., 1899, 69 [1503]. 336; 1899, 63 [1517], 66; /. Soc. Chem. Ind., 1899, 18
532, 790. "' '
340 ORGANIC PREPARATIONS
value of this reaction has been adversely criticised by P. W. Squire^
and by E. Merck.-
MacLagaris Test. — o-i g. of cocaine hydrochloride is dissolved in
lOO c.c. of water, and o-2 c.c. of ammonia (sp. gr. 096) added ; on
vigorously scratching the sides of the glass vessel with a glass rod, a
flocculent crystalline precipitate is formed within ten minutes without
any milky turbidity being produced in the liquid ; the latter should
remain quite clear.^
This test is prescribed as follows by the British Pharmacopceia : —
o-i a-, of cocaine dissolved in 100 c.c, of water and 0-25 c.c. of a solution
of ammonia added, affords a clear solution from which a crystalline
precipitate should gradually separate on stirring.
The German Pharmacopoeia gives the following modification of this
test: — If a solution of o-i g. of cocaine hydrochloride in 80 c.c. of water
is carefully mixed, without shaking, with 2 c.c. of a mixture of i part
of ammonia (10 per cent.) and 9 parts of water, no turbidity should
become apparent within half an hour. On scratching the sides of the
(^lass vessel with a glass rod, the above-mentioned separation of crystals,
etc., should then take place.
Oro-anic Matter ; Sugar ; Foreign Alkaloids. — Cocaine hydrochloride
should produce colourless solutions when dissolved in nitric and in
sulphuric acids in the proportion of i -.10,
Water. — No appreciable loss in weight should take place on drying
cocaine hydrochloride at 100°. The British Pharmacopoeia prescribes
that the salt should not lose more than i per cent, of moisture when
dried for twenty minutes at 95''-6-ioo''.
Cocaine hydrochloride may be estimated volumetrically in alcoholic
solution, using Poirrier's blue as indicator, as described for quinine
hydrochloride (p. 381). i c.c. of N\^ potassium hydroxide corresponds
to 006793 g. of cocaine hydrochloride.
Coumarin.
yO — CO
CeH/ I . Molec. wt. 14605.
^CH = CH
Coumarin forms white, glistening, small, leafy crystals, and possesses
a characteristic smell. It; is sparingly soluble in cold water (about
I : 400), more readily in boiling water (about i : 45), and very soluble
1 Chem. and Drug., 1899, 54, 64 1.
2 Pharm.J., 1899, 62 [l5"]. 523 ; /• Soc. Chem. bid., 1899, 18, 713.
3 For further details of the MacLagan test, cf. Gunlher, I'/iarm. Zentralh., 1899, p. 186 ; E.
Merck, Pliarm. Zeit., 1899,44. 367;/. Soc. Chem. Ind., 1899, 18, 713; C. Boehringer, Chem.
aii'i Druji., 1899, 55, 59 ; Zimmer & Co., Pharm. Zeit., 1899, 66, $83 ; /. ^oc. Chem. /;/</., 1899,
18, 1055; B. H. Paul and A. J. Cownley, Pharm. J., 1899, 62 [15"]. 524-
COUMARIN. DEXTROSE 341
in alcohol and in ether; melting point 6f', boiling point 291°. On
fusing coumarin with potassium hydroxide, salicylic and acetic acids are
formed, which may be readily identified.
Tests for Impurities.
Vanillin. — No coloration should be produced on heating 0-2 g. of
coumarin with a mixture of 5 c.c. of phenol and 3 c.c. of sulphuric acid
at i6o°-i70° for several minutes; vanillin gives a blood-red or very
dark red coloration.^
Organic Impurities. — A colourless solution should be formed on
dissolving i g, of coumarin in 10 c.c. of sulphuric acid.
Inorganic Impurities. — On ignition, i g. of coumarin should not leave
more than 0-5 mg. of residue.
Acetanilide. — 0-2 g. of coumarin is boiled for one minute with 2 c.c.
of hydrochloric acid, and then 4 c.c. of phenol solution (i : 20) together
with a filtered solution of calcium hypochlorite added ; no violet
coloration should be produced. The latter would be formed in presence
of acetanilide, in which case the colour of the mixture would be changed
to indigo-blue on the further addition of ammonia. The acetanilide
may be most simply estimated by determining the nitrogen by
Kjeldahl's method, provided that no other substances containing
nitrogen are present.-
Dextrose.
QHiPc- Molec. wt. i8o-io.
CoHiPg+HoO. Molec. wt. 198-11.
Anhydrous dextrose consists of small, white, odourless prisms, joined
together to form warty masses, or of a white crystalline powder. It has
a sweet taste, the degree of sweetness being less than half that of cane
sugar. Dextrose containing water of crystallisation forms white,
granular, crystalline masses. The anhydrous substance melts at 146'^,
the hydrated at about 85°. The specific rotatory power of the anhydrous
dextrose is [a]D=52-5; that of the hydrated form [ajo =477. The
so-called anhydrous dextrose of commerce generally contains small
quantities of water, which lower the melting point. Dextrose is very
soluble in water, almost insoluble in cold alcohol, but more so in boiling
alcohol.
Dextrose reduces alkaline copper and bismuth solutions, ammoniacal
silver solution, and copper acetate solution on warming.^
1 Cf. Merck's Reag.-Verz,, 1908, p. 1 3 3.
2 For the detection, separation, and identification of coumarin and vanillin in commercial
extracts, cf. Z. anal. Chem., 190^, 43, 263.
' For reactions of dextrose, cf. Merck's Reag.-Verz., 1908, p. 294.
342 ORGANIC PREPARATIONS
Tests for Impvirities.
Inorganic Matter. — On ignition, 5 g. of dextrose should not leave
more than 0-5 mg. of residue.
SulpJuiric Acid. — An aqueous solution of dextrose (i : 10) should
give no reaction with barium chloride solution.
Hydrociiloric Acid. — No precipitate, but at most onl}' a faint
opalescence, should be shown on adding a few drops of nitric acid and
silver nitrate solution to an aqueous solution of dextrose (i : 10).
Cane Sugar.— A colourless solution should be produced on dissolving
I g. of dextrose in 10 c.c. of sulphuric acid at 15"; only a pale yellow
coloration should result on standing for a quarter of an hour.
Dextrin. — i g. of dextrose should dissolve completely in 20 c.c. of
boiling 90 per cent, alcohol without leaving any insoluble residue. An
aqueous solution of dextrose (i : 10) should not turn a reddish colour
on the addition of a very dilute iodine solution.
Quantitative Estimation.
The water in dextrose is determined by drying at 100° till constant.
Dextrin in impure dextrose is determined indirectly by estimating
the content of dextrose, of water, and of ash, and calculating the dextrin
by difference; or, the dextrose is determined before and after inversion,
and the dextrin calculated from the difference.
The content of dextrose may be arrived at by various methods : — -
1. By measuring the polarisation of the aqueous solution.^
2. From the specific gravity of the aqueous solution.-
3. By the reducing action on Fehling's solution, either using a
volumetric method or by weighing the cuprous oxide.
Details of these methods are described in the sections on " Sugar "
(pp. 554 et seq.) and " Brewing Materials and Beer" (pp. 824 et seg.).
The following volumetric method by E. Riegler^ is simple and
satisfactory.
This method is based on the estimation of the copper in a known
volume of Fehling's solution before and after the reduction by means
of dextrose, the copper being estimated iodometrically according to the
equation : —
2CUSO4+4KI = 2K.SO, + CuJ.,+ l2.
A copper solution is prepared (69-28 g. of crystallised copper
sulphate to the litre), as well as a solution of Rochellc salt (346 g. of
Rochelle salt and 100 g. of sodium hydroxide to the litre), the former
being standardised as follows : — 10 c.c. of the copper solution, 10 c.c. of
' Landolt, Ber., 1888, 21, 191 ; Z. anal. Chem., 1889, 28, 203.
2 Z. ana!. Chem.^ 1883, 22, 454.
' Z. anal. Chem., 1898, 37, 22 ; /. Soc. Chem, Ind., 1898, 17, 499.
DEXTROSE 343
the Rochelle salt solution, lOO c.c. of water, and 2 c.c. of pure con-
centrated sulphuric acid are well mixed in a 200 c.c. flask, 10 c.c. of a
10 per cent, aqueous solution of potassium iodide added, and the
contents of the flask well mixed. In the course of about ten minutes
starch solution is added and the free iodine titrated with iV/io sodium
thiosulphate, until the blue colour disappears and does not return on
standing for five minutes ; a return of the blue colour after standing- for
over five minutes is disregarded. Each cubic centimetre of thiosul-
phate solution corresponds to 0-00635 g. of copper. If the solutions
have been correctly prepared, 10 c.c. of the copper solution will require
27-8 c.c. of the thiosulphate solution, and the quantity of copper found
will be, therefore, 27-8 x 0-00635 =0-1765 g. If more or less than
27-8 c.c. be required, the volume found must be used as a factor in
place of 27-8,
To carry out the estimation, 10 c.c. of the copper solution, 10 c.c.
of Rochelle salt solution, and 30 c.c. of water are heated to boiling in a
200 c.c. beaker, and 10 c.c. of a solution of dextrose, not stronger
than I per cent, are run in. The mixture is kept boiling for some
time, after which the precipitate is allowed to settle, the solution filtered
(using the pump) through an asbestos filter, and the precipitate washed
with about 80 c.c. of water. The filtrate is washed out into a 200 c.c.
flask, 2 c.c. of sulphuric acid added, then 10 c.c. of potassium iodide
solution, and after standing for ten minutes starch solution is added
and the iodine titrated with thiosulphate solution as above.
If V represents the number of cubic centimetres of thiosulphate
solution used, then the quantity of copper reduced by the sugar is
= (27-8 — V) X 0-00635.
Diethyl Barbituric Acid. (Veronal.)
,C0— NH-
(C2H5).3C< >C0. Molec.wt. 184-12.
\C0— NH/
Diethyl barbituric acid or veronal is a white, crystalline powder with
a somewhat bitter taste, soluble in about 145 parts of cold or in 12
parts of boiling water. It is readily soluble in ether, acetone, ethyl
acetate, hot alcohol, and alkalis, but is only sparingly soluble in
chloroform and glacial acetic acid. The aqueous solution reacts faintly
acid with litmus paper. Melting point 191°. The addition of a few
drops of nitric acid and several drops of Millon's reagent to a solution
of 0-05 g. of veronal in 10 c.c. of water produces a white gelatinous
precipitate which redissolves on adding a large excess of the pre-
cipitant. Ammonia is evolved on boiling o-i g, of veronal with 5 c.c.
of potassium hydroxide solution.
344 ORGANIC PREPARATIONS
Tests for Impurities.
Hydrochloric and SulpJiuric Acids. — Neither barium nitrate nor
silver nitrate solution should produce a precipitate with a solution of
o-i g. of veronal in 20 c.c. of water.
Organic Impurities. — Veronal should dissolve in sulphuric acid to a
colourless solution. It should not become coloured on shaking with
nitric acid.
Inorganic Impurities. — o-i g. of veronal is placed on the lid of a
platinum crucible and heated on an asbestos plate. The preparation
should sublime, leaving only very little carbon behind. On ignition,
no appreciable residue should be left.
Veronal-Sodium.
C.,H. CO . NXa
\C<; /CO. Molec. wt. 206-II.
C.2H/ \CO.NH /
This is a white, crystalline powder with a bitter taste, and is verj'-
soluble in water (i : 5). The aqueous solution reacts alkaline. Mineral
acids as well as acetic acid produce a voluminous white precipitate
when added to a concentrated aqueous solution (i : 5).
Veronal-sodium may be titrated with A^/io hydrochloric acid, using
either methyl orange or Congo red as indicator.^
Ethyl Acetate.
CH3 . COOC2H5. Molec. wt. 88-06.
Ethyl acetate is a colourless, volatile liquid with a characteristic
refreshing smell. It is miscible in all proportions with alcohol, ether,
benzene, and chloroform, and with 17 parts of water.
Ethyl acetate, when quite pure and free from water and alcohol,
has a sp. gr. of 0-9254 at 0° compared with water at 4° (J. Wade and
R. W. Merriman ■-), and boils at yf. The pure commercial product,
which also is used in medicine, has a sp. gr, of 0-900-0-904 and boils
at 74''-78^ ; it contains traces of water and alcohol.
Tests for Impurities.
Inorganic and non-volatile Organic Matter. — No residue should be
left on evaporating 50 c.c. of ethyl acetate on the water-bath.
Fi-ee Acid {Acetic Acid). — A piece of blue litmus paper placed in
ethyl acetate should not be immediately reddened.
' For further details concerning veronal, cf. Pliartn. Zoitial/i., 1908, p. 104 1.
'^ J. Chcm. Soc.^ 1912, lOl, 2429.
ETHYL ACETATE 345
Ainyl Compounds and Ethyl Butyrate. — On pouring ethyl acetate
over filter paper and allowing it to evaporate at the ordinary tempera-
ture, it should not be possible to detect the smell of foreign esters after
the smell of the eth)'l acetate ceases to be noticeable.
Amyl Alcohol and Organic Impurities. — On pouring a few cubic
centimetres of ethyl acetate carefully on to sulphuric acid, no coloration
should be produced at the zone of contact of the two layers of liquid.
Water and Alcohol. — On thoroughly shaking 25 c.c. of ethyl acetate
with 25 c.c. of a saturated solution of calcium chloride for one minute,
no appreciable increase in the volume of the latter should take place.
Note. — On shaking ethyl acetate with water, the volume of the
latter increases from 2-2-5 c.c, owing to the water taking up some ethyl
acetate ; on the other hand, ethyl acetate also takes up water. The use
of a cold, saturated solution of calcium chloride allows of a better
estimation of the content of water and of alcohol being made, since the
latter are completely taken up by the calcium chloride solution. A
turbidity produced on dissolving in benzene will indicate if more than
a permissible quantity of water is present. i c.c. of ethyl acetate
should dissolve to a clear solution in 10 c.c. of benzene. Ethyl acetate
quite free from water will also dissolve to a clear solution in official
paraffin oil (liquid paraffin).
The content of alcohol is determined in the same manner as described
for ethyl butyrate (see p. 349).
Ethyl Alcohol.
C2H5 . OH. Molec. wt. 46-05.
Two kinds of ethyl alcohol come under consideration for technical
purposes : the so-called " Absolute Alcohol " and " Rectified Spirit " ;
from the latter, various mixtures with water are prepared, such as the
70 per cent, 60 per cent., 45 per cent., and 20 per cent, spirit of the
British Pharmacopoeia.
The qualitative examination of these varieties may be made in the
same manner, without reference to the differences in the content of
alcohol.
Absolute alcohol is a colourless, neutral liquid boiling at 7^"-^ ; the
specific gravity, according to the determinations of Mendeleff, is
0-79367 at 1574°- A good commercial product should contain not
less than 99-11 per cent, by weight of alcohol and have a sp. gr.
of not over 0-797. A guarantee of 100 per cent, can never be given,
since 100 per cent, alcohol is very hygroscopic.
Rectified spirit should contain at least 94-38 per cent, by weight, and
96-37 per cent, by volume of alcohol and have a sp. gr, not higher
than 0-81 1. The "Rectified Spirit" of the British Pharmacopoeia
346 ORGANIC PREPARATIONS
has a sp, gr. of 0S340 and contains 85-65 per cent, by weight of ethyl
alcohol.
Tests for Impurities.
Fusel Oil. — No turbidity and no smell foreign to alcohol should be
produced on mixing 10 c.c. of alcohol with 30 c.c. of water in an
Erlenmeyer flask. On rubbing a few drops of the sample between
the hands, no unpleasant smell (fusel oil) should be noticeable after the
evaporation of the alcohol. On the addition of 25-30 drops of a
I per cent, alcoholic solution of salicyl aldeh)-de and 20 c.c. of con-
centrated sulphuric acid to a mixture of 5 c.c. of alcohol and 5 c.c. of
water, and cooling the mixture, a lemon-yellow coloration is produced
if the alcohol be free from fusel oil. If only traces of fusel oil are
present, the solution will appear yellow by transmitted light and red
by reflected light. In no case should the colour be reddish or red.
If a mixture of 10 c.c. of alcohol and 02 c.c. of 1 5 per cent, potassium
hydroxide solution be evaporated down to i c.c. on the water-bath,
there should be no smell of fusel oil on adding excess of dilute
sulphuric acid.
Acetone. — On shaking a mixture of 2 c.c. of alcohol, 6 c.c. of baryta
water, and 6 drops of mercuric chloride solution (i : 20) for one minute
and filtering, the filtrate should not be darkened by the addition of
ammonium sulphide solution.
Aldehyde. — A mixture of 10 c.c. of alcohol, 10 c.c. of water, and 2 c.c.
of ammoniacal silver solution (prepared by mixing 10 c.c. of 5 per cent.-
silver nitrate solution with 5 c.c. of ammonia of sp. gr. 0-96), allowed to
stand in the dark at the ordinary temperature for fifteen hours, should
become neither coloured nor turbid.
Ftirfural{^Fjirfuraldehyde\ — A mixture of 10 c.c. of alcohol, 5 drops
of acetic acid (sp. gr. 1-040- 1-042), and i drop of aniline, as colourless
as possible, should not turn red in the course of one hour.
Molasses Spirit. — On pouring 5 c.c. of alcohol carefully over 5 c.c. of
concentrated sulphuric acid, no rose-coloured ring should be produced
at the point of contact of the two layers of liquid.
Metals atul Tannin. — No coloration should be produced on adding
either i c.c. of ammonia (sp. gr. 0-96) or 5 c.c. of sulphuretted hydrogen
water to 10 c.c. of alcohol.
Inorganic Matter. — No appreciable residue should remain on slowly
evaporating 50 c.c. of alcohol.
Methyl Alcohol. — If a negative result has been obtained when
testing for acetone, it may be taken for granted that the alcohol
contains no crude wood spirit.
For the independent detection of methyl alcohol in ethyl alcohol, a
number of methods have been proposed, based on the oxidation of the
ETHYL ALCOHOL 347
methyl alcohol to formaldehyde and the subsequent identification of the
latter. A critical summary of the various methods has been given by
A. Vorisek,^ who recommends oxidation with potassium bichromate
and sulphuric acid and testing the distillate obtained for formaldehyde
by the addition of ferric chloride and albumin solutions in presence of
concentrated sulphuric acid, when a sharply defined violet-coloured zone
is formed at the junction of the liquids.
Quantitative Estimation.
The content of alcohol is practically always determined by means
of the specific gravity, specially prepared Tables being employed of
which those of the Excise Authorities constitute the legal standard in
this country. A full description of this estimation is described under
the heading " Alcoholometry," in the section on " Alcohol, Potable
Spirits, and Liqueurs," this Vol., p. 709.
Should it be desired to carry out an estimation of ethyl alcohol by
a chemical method, that given by O. Blank and H. Finkenbeiner^ for
methyl alcohol is to be recommended, since it is also quite suitable for
the estimation of ethyl alcohol. An excess of A710 potassium
bichromate solution and sulphuric acid are added to the very dilute
aqueous solution of the alcohol, and after standing at the ordinary
temperature for some hours, potassium iodide is added and the mixture
titrated back with A710 sodium thiosulphate solution. The oxidation
takes place according to the equation : —
CH3.CH2OH + O2 = CH3.C00H + H,0.
A reliable method for the quantitative estimation of methyl alcohol
in ethyl alcohol, based on the oxidation of the former to carbon dioxide,
has been worked out by T, E. Thorpe and J. Holmes,^ (See p. 717.)
Ethyl Bromide.
CoHsBr. Molec. wt. 108-96.
Ethyl bromide is a clear, colourless, strongly refractive, ethereal
smelling liquid with a sp. gr. of I-453-I-457, and boiling at 38°-40°.
Perfectly pure ethyl bromide has a sp. gr. of 1-4735 and boils at sS'^-39'^.
Since the pure product readily turns yellow through decomposition,
about I per cent, of alcohol is added to render the commercial product
less liable to decomposition.
1 /. Soc. Chem. Ind., 1909, 28, 823. Cf. also C. Deniges, Bull. Soc. Chim., 1910, 7, 951 ; /.
Soc. Chem. Ind., 1910, 29, 1325, and Merck's Reag.-Verz., 1908, p. 297.
2 Ber., 1906, 39, 1326 ; J. Soc. Chem. Ind., 1906, 25, 500.
3 For estimating ether and benzene in alcohol, c/. H. Wolff, Chem. Zeit., 1910, 34, I193;
J. Soc. Chem. Ind., 1910, 29, 1403, and for estimating carbon bisulphide in alcohol, W. Schmitz-
Dumont, Chem. Zeit., 1897, 21, 487 and 510 ; /. Soc. Chem. Ind.^ 1897, 16, 829.
348 ORGANIC PREPARATIONS
Tests for Impurities.
Inorganic and non-volatile Organic Matter. — Not more than i mg.
of residue should remain on evaporating 20 c.c. of ethyl bromide on the
water-bath.
Pliosplionis Conipoujids. — No unpleasant garlic-like odour should be
recognisable on evaporating 5 c.c. of ethyl bromide in a small porcelain
dish.i
Hydrobroinic Acid. — Ethyl bromide should react neutral. On
shaking 10 c.c. with 10 c.c. of water for a few seconds, pouring off 5 c.c.
of the aqueous layer and adding 2 drops of A710 silver nitrate solution,
no turbidity should be produced within five minutes. The ethyl
bromide should not be shaken up directly with silver nitrate solution,
since silver bromide is always thus formed.
Aviyl Compounds, Ethylene didromide, Organic SulpJiur Compounds. —
10 c.c. of ethyl bromide are well shaken during one hour with 10 c.c. of
sulphuric acid in a stoppered glass cylinder previously rinsed out with
sulphuric acid. No yellow coloration of the sulphuric acid should be
produced.
EtJiyl Ether. — A possible content of ether is indicated by a too low
specific gravity. It is stated that commercial ethyl bromide may
contain up to 15 per cent, of ether.^
Ethyl Butyrate.
C3H, . COOC0H5. Molec. wt. 1 16- 10.
Eth}-1 butyrate is a colourless liquid, sparingly soluble in water but
readily so in alcohol, ether, benzene, chloroform, and petroleum spirit.
In the diluted state it possesses a pleasant smell and tastes of pine
apple. Its sp. gr. is 0-884, and it boils at 11 8'- 120''.
Tests for Impurities.
Inorganic aiid non-volatile Organic Matter. — 10 c.c. of eth}-l butyrate
should not leave more than 0-5 mg. of residue on evaporation.
Hyd7-ochloric and Sulphuric Acids. — On shaking 20 c.c. of eth\-l
butyrate with 10 c.c. of water, the separated water should show no
reaction with cither silver nitrate or barium chloride solutions. The
test cannot be made with litmus paper, since the water ahva}-s reacts
acid owing to liberated butyric acid.
Water. — Ethyl butyrate should dissolve without turbidity in ten
times its volume of benzene. Chemically pure ethyl butyrate, absolutely
free from water and alcohol, mixes also with petroleum spirit (boiling
1 Cf. Chem. Zeit. Rep., 1908, 32, 638. - Pharm, Zentialh., 35, 674.
ETHYL BUTYRATE 349
point 50°-75^) and official paraffin oil (liquid paraffin) to form quite
clear solutions.
Alcohol — On shaking 20 c.c. of ethyl butyrate with 20 c.c. of a
saturated solution of calcium chloride, and allowing the two liquids to
separate completely, no change in volume of the calcium chloride
solution should take place.
Quantitative Estimation.
Ethyl butyrate comes into commerce in alcoholic solution, the
product being known as " pine-apple oil." The content of the ester in
such products may be sufficiently accurately estimated by shaking with
a proportionately large volume of saturated calcium chloride solution.
The accurate estimation of the alcohol and of the ester, in either
concentrated or dilute commercial varieties, is carried out as follows : —
25 g. of the ester are heated with a solution of 22 g. of potassium
hydroxide in 40 c.c. of water in a 200-250 c.c. Jena glass flask fitted with
an upright condenser, until the saponification is complete. In the case of
products containing a high percentage of ester, complete saponification is
indicated by the original two layers of ester and of potassium hydroxide
disappearing to form one homogeneous straw-coloured solution. The
mixture is then further boiled for about half an hour. In the case of
products of low ester content {i.e., mixtures containing a little ester and
much alcohol), after the disappearance of the two layers of liquid, the
mixture is further boiled vigorously for one hour. The saponification
should be carried out over the free flame, or over a wire gauze. The con-
tents of the flask are then allowed to cool, about 60 c.c. of water washed
down the upright condenser into the flask, and 100 g. of the mixture
then distilled off, using an ordinary condenser and a condensation bulb
between the flask and condenser, and taking care that no alkali spirts over,
and that no alcohol is lost by evaporation. From the specific gravity of
the distillate its alcohol content can be calculated, and from this value
the alcohol content in the ester in percentage by weight. Having thus
determined the free alcohol together with the alcohol combined with the
butyric acid, the content of combined alcohol, from which the content
of pure ester may be calculated, is determined by saponifying a weighed
quantity of the ester with an excess of iV/2 potassium hydroxide, and
titrating back with A^/2 hydrochloric acid, using phenolphthalein as
indicator, i c.c. of N\2 potassium hydroxide corresponds to 0-05805 g.
of butyric ester, or to 0-04605 g. of combined alcohol.
The difference between the total alcohol and the combined alcohol
gives the quantity of free alcohol. All the necessary data may be,
therefore, obtained by making the above two estimations, from which
the content of pure ester, of alcohol, and of water are calculated.
350 ORGANIC PREPARATIONS
Ethyl Ether.
CoH- . O . CoH.. Molec. \vt. 74-08.
Ether is a colourless, mobile, and readily inflammable liquid, posses-
sing a characteristic smell. It boils at 34°-36°, and has a sp. gr. of 0720.
Ordinary commercial ether has a sp.gr. of 0725, owing to its containing
small quantities of water or of alcohol. Ether used for the quantitative
estimation of fat, in the analysis of alkaloids, and for anaesthetic
purposes, should have a sp. gr. of not more than 0720-0722. The
ether of the British Pharmacopoeia has a sp. gr. of 0735, and contains
not less than 92 per cent, by volume of pure ether.
Tests for Impurities.
Residue. — On allowing 20 c.c. of ether to evaporate spontaneously in
a glass dish, covered with an inverted funnel, the residue remaining on
the sides of the dish should have no smell, should not redden or bleach
blue litmus paper, and on warming on the water-bath should evaporate
completely, leaving no residue.
Water. — On shaking 20 c.c. of ether with i g. of dehydrated copper
sulphate, the latter should not acquire either a green or blue colour.
A method for the quantitative estimation of water in "wet" ether
based on the insolubility of cadmium iodide in anhydrous ether, has
been worked out by D. Tyrer.^
Hydrogen Peroxide, Ozone, Ethyl Peroxide. — On shaking 10 c.c. of
ether with i c.c. of potassium iodide solution (i : 10) in a full, closed,-
glass-stoppered vessel, in the dark, neither the potassium iodide solution
nor the ether should become coloured at the end of one hour.
A very sensitive reaction for peroxides is the following : — o-i g. of
pure, powdered vanadic acid is heated for a quarter of an hour on the
water-bath with 2 c.c. of concentrated sulphuric acid, and then 50 c.c. of
water added. This reagent has a yellow colour. On shaking 20-30 c.c.
of ether with 2 c.c. of this reagent, the smallest traces of peroxide
present will immediately turn the colour of the latter to brown or
reddish-brown.
Aldehyde and Vinyl Alcohol — On shaking 20 c.c. of ether for one
minute in a glass-stoppered cylinder with 5 c.c. of Nessler's reagent, no
reddish-brown precipitate, soon turning to black, should be produced.-
Acetone. — A mixture of 6 c.c. of baryta water and 6 drops of 5 per
cent, mercuric chloride solution are shaken for one minute with 20 c.c
of ether, and the aqueous solution separated and filtered. The latter
should show no dark coloration during ten minutes after the addition of
ammonium sulphide.
1 /. Chem. Soc. Proc, 1911, 27, I42 ; /. Soc. Chem. hid., I911, 30, 767.
2 Cf. Wobbe, Apolh. Zeit., 1903, p. 466.
ETHYL ETHER. FORMALDEHYDE 351
Sulphur Compounds. — On shaking 20 c.c. of ether with a drop of
mercury in a glass bottle for two minutes, the surface of the mercury
should show no change, and no black substance should be separated.
Alcohol — A test for alcohol is not necessary should the ether possess
the correct specific gravity ; a Table giving the specific gravities of
mixtures of alcohol and ether has been prepared by E. R. Squibb.^
According to Lieben, the presence of alcohol may be detected by the
iodoform reaction. The ether is shaken up with water, and the aqueous
solution warmed, after the addition of sodium hydroxide and iodine
solutions ; the formation of iodoform indicates the presence of alcohol.
Formaldehyde.
H . CHO Molec. wt. 3002.
Formaldehyde is a colourless liquid with an irritating smell, and is
miscible in all proportions with water and alcohol. The specific gravity
of the commercial product varies from i -08- 1-095 according to the
content of formaldehyde and of methyl alcohol, and the content of
formaldehyde varies fropri 30-40 per cent. The purest commercial
product is that used for medicinal purposes. The German Pharma-
copoeia gives the sp. gr. of i -079-1 -08 1 with about 35 per cent, of
formaldehyde. The specific gravity alone gives no reliable indication
as to the content of formaldehyde, since the commercial product always
contains some methyl alcohol which lowers the specific gravity. The
40 per cent, formaldehyde contains up to 20 per cent, of methyl
alcohol. In preparations containing less methyl alcohol, there is always
the possibility of paraformaldehyde separating out at somewhat low
temperatures.^
The methods for the estimation of methyl alcohol in formaldehyde
are fully described in the section on " Organic Dyes," Vol. IL, Part II.,
pp. 911 ^/ seq.
Formaldehyde reduces ammoniacal silver solution and Fehling's
solution and gives a deep red coloration with Schiff s reagent ; an
ammoniacal formaldehyde solution gives a white precipitate with
bromine water (hexamethylenetetramine bromide). On evaporating
formaldehyde on the water-bath a white amorphous mass (trioxy-
methylene) is left, which is insoluble in water, and which is completely
volatile on ignition. On making formaldehyde strongly alkaline with
ammonia, and heating the mixture on the water-bath, a white crystal-
line residue (hexamethylenetetramine) remains, which is readily soluble
in water. Other reactions that can be used for the quantitative deter-
1 Phartn. J., 1 884, p. 74 ; /. Soc. C/iem. Ind., 1884, 3, 53 1. Cf. also Z. anal. Chem., 1889,
26,97.
2 Cf. Merck's Jahresber., 1903, p. 79.
352 ORGANIC PREPARATIONS
mination of formaldehyde are described in the section on " Organic
Dyes," Vol. II., Part II., pp. 898 et seq.
Tests for Impurities.
Free Acid. — 10 c.c, of formaldehyde should not react acid after the
addition of 10 drops of N\\ potassium hydroxide. Formaldeh}-dc
sometimes contains up to o-2 per cent, of formic acid.
Hydrochloric Acid. — Formaldehj-de should, at most, only give a
slight opalescence on the addition of silver nitrate solution, and when
diluted with four times its volume of water should give no reaction
with this reagent.
Sulphuric Acid. — Formaldehyde should .show no reaction with
barium chloride solution.
Heavy Metals. — On the addition of sulphuretted hydrogen water,
formaldehyde should not be discoloured. Commercial products some-
times contain up to o-oi per cent, of cupric oxide, in which case the
above test will not be negative.
Inorganic Salts.— Not more than i mg. of residue should remain on
evaporating 10 c.c, of formaldehyde and igniting with free access of
air. The purest formaldehyde often contains minute traces of iron.
Quantitative Estimation.
The methods for the quantitative estimation of formaldehyde are
described in the section on "Organic Dyes," Vol. II., Part II., pp.
90 1 et seq.
Formic Acid.
n . COOH. Molec. wt. 4602.
Formic acid is a colourless liquid with an irritating smell. It has a
sp. gr. of 1-22 at 20 , boils at 100 -6, and melts at 8-6. It is miscible in
all proportions with water and alcohol. Sulphuric acid decomposes it
into carbon monoxide and water. On warming an aqueous solution of
formic acid (i : 10) with silver nitrate, metallic silver separates out;
warmed with mercuric chloride, mercurous chloride is precipitated ; and
on warming with yellow mercuric oxide, a colourless solution is first
formed from which, on further heating, carbon dioxide is evolved with
separation of metallic mercury.
Tests for Impurities.
Inorganic Matter. — Not more than 05 mg. of residue should be left
on evaporating 5 g. of formic acid.
Leady Copper, Iron. — Sulphuretted hydrogen water should produce
no change in a solution of formic acid (i : 20) rendered alkaline by
ammonia.
FORMIC ACID. GALLIC AClD 35^
Hydrochloric mid Oxalic Acids. — Neither silver nitrate solution at
the ordinary temperature nor calcium chloride solution, the latter being
added to a solution made alkaline with ammonia, should produce any
change in an aqueous solution of formic acid (i : 20).
Acetic Acid. — If i c.c. of formic acid is warmed on the water-bath
with 20 c.c. of water and 6 g. of yellow mercuric oxide, and frequently
shaken until no further evolution of gas takes place on filtering, the
filtrate should not react acid.
Acrolein^ Ally I Alcohol, Enipyreumatic Matter. — No irritating or
burning smell should be given off on saturating formic acid with excess
of sodium hydroxide solution.
Since formic acid comes into commerce in various degrees of
dilution, the content of formic acid should first be determined by
titration withiV/l sodium hydroxide solution, and the foregoing tests
then carried out with suitable quantities proportional to the degree
of dilution of the acid.
Quantitative Estimation.
Formic acid is estimated in aqueous solution by titration with N\i
sodium hydroxide, using 'phenolphthalein as indicator, i c.c. of iV/i
sodium hydroxide corresponds to 0-046016 g. of formic acid. Since
this simple titration gives no guarantee that only the formic acid
is estimated, it is better to use the method worked out by H. Franzen
and G. Greve, as described in the section on "Organic Dyes," Vol. II.,
Part II., p. 917. Other quantitative methods are described in the
same section.^
Gallic Acid.
C6H2(OH)3.COOH + H.p. Molec. wt. 18806.
Pure gallic acid comes into commerce as colourless or pale yellow
coloured needles or prisms, which possess an acid, astringent taste,
and which melt at 220", undergoing slow decomposition.
Gallic acid dissolves in 85 parts of water at 15° and in 3 parts
of boiling water, in 6 parts of alcohol and in 10 parts of glycerol.
It is only sparingly soluble in pure ether, but the solubility increases
with an increase in the proportion of alcohol contained in the ether used.
A bluish - black precipitate is produced on adding ferric chloride
to a solution of gallic acid. On standing in the air, an aqueous
solution of the acid, to which excess of alkali is added, turns reddish-
brown to black. Potassium cyanide colours the aqueous solution red.^
1 Cf. also A. F. Joseph, y. Soc. Chem. Ind., 191 1, 29, 11 89.
'^ For reactions distinguishing gallic from tannic acid, cf. Z. anal. Chem., 1889, 28, 103, 351 ;
1892, 31, 88 ; 1896, 35, 590; Fhartn, Zenlralh., 1899, p. 302 ; and Merck's Reag.-Veiz., 1908,
p. 294.
Ill z
354 ORGANIC PREPARATIONS
Tests for Impurities.
Inorganic Matter. — No residue should be left on igniting i g. of
gallic acid.
Sulphuric Acid. — Barium chloride solution should give no precipi-
tate when added to an aqueous solution of gallic acid (i : 50), acidified
with I c.c. of hydrochloric acid, and allowed to stand for one hour
at a temperature of 50 .
Water. — On drying at 100 till constant, gallic acid should not lose
more than 10 per cent, in weight.
Solubility in Water. — i g. of gallic acid should dissolve completely
in 20 c.c. of water, on warming ; the aqueous solution should be
colourless, or at most only have a faint yellowish coloration.
Quantitative Estimation.
The following method given by W. P. Dreaper ^ may be used : —
5 g. of the gallic acid to be examined are dissolved in i litre of water.
To 100 c.c. of this solution i g. of barium carbonate made up into
a thin paste with water is added (to combine with the free sulphuric
acid produced in the reaction) ; the mixture is then heated to 90' and
N\\ copper sulphate solution run in until copper can be detected in the
solution by means of potassium ferrocyanide. This end-point is shown by
a brown coloration being produced when a drop of the liquid is put
on to filter paper and a drop of potassium ferrocyanide solution allowed
to fall on to it. Having thus found how much copper sulphate solution
is required for the gallic and tannic acids together in 100 c.c. of the
above solution {i.e., for 0-5 g. of substance), the tannic acid is precipitated
out of 200 c.c. of the same solution by adding 28-6 c.c. of a 2 per cent,
solution of gelatin, saturating the mixture with common salt, adding
5 g. of barium sulphate and 10 c.c. of dilute sulphuric acid (i : 20), and
making up to 400 c.c. The mixture is well shaken, and the tannic
acid filtered off. The content of gallic acid in 200 c.c. of the filtrate
is determined by titrating with copper sulphate solution. The difference
between the two titrations gives the amount of tannic acid contained
in the gallic acid taken.
The copper sulphate solution is best standardised against pure gallic
acid and pure tannin. Gallic acid of sufficient purity for this purpose
is obtainable, and tannic acid of like purity is prepared by shaking
up pure tannin with ether until no reaction is obtained with potassium
cyanide, and then drying till constant. By this method, gallic and
tannic acids may be accurately estimated, either individually or together,
but in determining both together the result for tannic acid comes out
' J. Soc. Chem. I>id., 1893, 12, 412.
GELATIN 355
somewhat high, since the precipitation with gelatin solution carries
down some gallic acid with the tannic acid.
Gelatin.
The best commercial gelatin forms colourless, or almost colourless,
thin, transparent flakes of glassy lustre, which should be tasteless and
odourless.
Gelatin swells up in water, dissolving readily in hot water. The
hot solution should be clear or only slightly opalescent. On cooling a
solution of I g. of gelatin in lOO c.c. of water, it should solidify to a
jelly. Gelatin is insoluble in alcohol and in ether. Tannic acid solution
produces a flocculent precipitate when added to a dilute aqueous solution
of gelatin.^
Tests for Impurities.
Inorganic Matter. — Not more than o-2 g. of residue should remain
on igniting lo g. of gelatin. The cold, ignited residue is tested for
copper 2 by dissolving in 3 c.c. of hydrochloric acid and adding excess of
ammonia, when no blue c'oloration should be produced.
Free Acids. — According to J. Messner no commercial gelatins are
free from acid.^ In the best commercial varieties he found up to i
per cent, of free acid (calculated as sulphuric acid). Taking this figure
as an allowable maximum, products may be tested as follows : — Red
litmus paper should be turned blue after adding o-2 c.c. of iV/i potassium
hydroxide to a warm solution of i g. of gelatin in 100 c.c. of water.
Sulphurons Acid. — Good gelatin generally contains from o-oi-o-02
per cent, of sulphur dioxide.'* The quantitative estimation is some-
what lengthy, and the following test (given by the German Pharma-
copoeia) suffices : — 5 g. of gelatin are allowed to soak in 30 c.c. of
water in a wide-mouthed, 150 c.c. flask and then dissolved by gently
warming on the water-bath. 5 g. of phosphoric acid (25 per cent.) are
then added, the flask loosely closed by a cork, on the under side of which
is fastened a moistened piece of potassium iodide and starch paper, and
the contents heated on the water-bath, and frequently shaken round
with care. No temporary or permanent blue coloration of the paper
should take place within a quarter of an hour.
A method for the quantitative estimation of free and combined
sulphurous acid in gelatin has been recently described by R. W. Sindall
and W. Bacon.^
Water. — The water in gelatin is determined by drying at 105°. A
1 For identifying reactions for gelatin, cf. Liesegang, Pharm. Zeit., 1910, 55, 283.
2 QC W. B. Hart,/. Soc. Chetn. Ind., 1909, 28, 739. ^ Merck's Jahresber., 1900, p. 3r.
* Cf. W. Lange, Arb. Kais. gesundh. Ami, 1909, 32, 144 ; J. Soc. Chem. hid., 1909, 28, 995.
5 Analyst, 1914, 39, 20.
356 ORGANIC PREPARATIONS
good sample should not contain more than 20 per cent, of water; the
proportion in commercial gelatins usually varies from 11 to 14 percent.^
Guaiacol.
OH(i)
QH^( . Molec. \vt. 12406.
^OCH3(2)
Guaiacol is prepared cither as a clear, colourless, refractive, oily
liquid boiling at 205'', or in the form of colourless crystals which melt at
28^ It dissolves in about 60 parts of water, and is readih- soluble in
alcohol and in ether. The addition of one drop of a dilute solution of
ferric chloride to the aqueous solution produces a blue coloration which
immediately changes to reddish-brown, and when added to an alcoholic
solution, a coloration changing from green through blue to greenish-
brown is produced."-
Tests for Impurities.
A mixture of l vol. of guaiacol with 2 vols, of sodium h)'droxide
solution should be clear and should remain clear and colourless on
diluting with 10 vols, of water. A mixture of guaiacol with 2 vols, of
potassium hydro.xide solution should solidify to a white crystalline mass
in a short time. Guaiacol should dissolve to a colourless solution in
cold, concentrated sulphuric acid.
Guaiacol Carbonate.
C0(0 . C„H, . OCH3).. Molec. wt. 274- 1 1 2.
This is the most important pharmaceutical preparation obtained
from guaiacol. It is a white, almost odourless, crystalline powder. It
dissolves readily in chloroform and in hot alcohol, sparingly- in cold
alcohol and in ether, and is insoluble in water. It melts between 86°
and 88'. Guaiacol carbonate contains approximately 90 per cent, of
guaiacol. The latter is separated by saponifying 0-5 g. of guaiacol
carbonate with a mixture of 10 c.c. of alcohol and potassium hydroxide
solution. After evaporating off the alcohol, the residue is taken up with
water, acidified with dilute sulphuric acid, and the guaiacol extracted
with ether. On evaporating off the ether an oily residue smelling of
guaiacol is left, and which, when dissolved in alcohol, gives the character-
istic green coloration with ferric chloride.
If about 0-2 g. of guaiacol carbonate is boiled for from two to three
minutes with 10 c.c. of quite clear alcoholic potash (i g. potassium
hydroxide in 20 c.c. of absolute alcohol), a white crystalline precipitate
' Sind;ill and Bacon, loc. cil,
'^ For identifying reactions, cf. Merck's /\eag.-\'e>:., 1908, p. 295.
HEXAMETHYLENETETRAMINE 357
separates out, which, after washing with alcohol, evolves carbon dioxide
when treated with h)'drochloric acid.
Tests for Impurities.
Free Guaiacol. — A solution of 0-5 g. of guaiacol carbonate in 10 c.c.
of hot alcohol should not change litmus paper and should give no blue
or green coloration with ferric chloride.
Hydrochloric Acid. — On shaking i g. of guaiacol carbonate with
ro c.c. of water and filtering, the filtrate should give no reaction on
acidifying with nitric acid and adding silver nitrate solution.
Organic Impurities. — o-i g. of guaiacol carbonate should dissolve to
a colourless solution in i c.c. of sulphuric acid.
Inorganic Impurities. — Not more than 0-5 mg. of residue should be
left on igniting 05 g. of guaiacol carbonate.
Hexamethylenetetramine.
(CH.,)(.N^. Molec. wt. 140-14.
Hexamethylenetetramine is a colourless, crystalline powder which
volatilises on heating without melting. It dissolves in 1-5 parts of
water and in 10 parts of alcohol (of about 85 per cent, by weight).
The solutions react alkaline with litmus paper. On heating the aqueous
solution (i :20) with dilute sulphuric acid, formaldehyde, recognisable
by its smell, is given off On further warming, after the addition of
excess of sodium hydroxide solution, ammonia is evolved. Silver
nitrate solution produces a white precipitate with aqueous solutions of
hexamethylenetetramine (i : 20), which is soluble in excess of the
latter. A carmine-red coloration is produced on carefully heating a
mixture of o-i g. of hexamethylenetetramine with o-i g. of salicylic
acid and 5 c.c. of concentrated sulphuric acid.
Tests for Impiirities.
Heavy Metals and Sulphuric Acid. — No precipitate should be pro-
duced on adding either sulphuretted hydrogen water or barium nitrate
solution to an aqueous solution (i : 20).
Hydrochloric Acid. — On adding 5 c.c. of nitric acid and silver nitrate
solution to an aqueous solution (i : lOo), at most, only a faint opalescent
turbidity should be produced.
Ammonium Salts. Paraformaldehyde. — On heating an aqueous
solution (i : 20) to boiling with Nessler's reagent, neither a coloration
nor a turbidity should be produced.
hiorgajiic Impurities. — Not more than 0-5 mg. of residue should
remain on volatilising i g. of hexamethylenetetramine.
358 ORGANIC PREPARATIONS
Quantitative Estimation.
I g, of the preparation is evaporated to dryness on the water-bath
with 40 c.c. of iV/i sulphuric acid ; formaldehyde is formed whilst the
acid combines with the nitrogen to form ammonium sulphate. The
residue is taken up with water and further evaporated down until the
formaldehyde is completely driven off. It is then dissolved in lOO c.c.
of water, and the excess of sulphuric acid titrated back with Nji alkali,
using litmus as indicator. The difference between the number of cubic
centimetres of alkali used and the number of cubic centimetres of acid
taken in the first instance gives the number of cubic centimetres of
acid used up in the formation of ammonium sulphate in accordance with
the equation : —
(CH.,),N, + 6H,0 + 2H2SO, = 6CH204-2(NHJ,SO,.
I g. of hexamethylenetetramine corresponds, therefore, to 2874 c.c.
of N/i sulphuric acid.^
Hydroquinone (Quinol).
OH(i)
CgH/ . Molcc. wt. 11005.
^0H(4)
Hydroquinone forms colourless and odourless six-sided prisms
which melt at 169°, and at a higher temperature sublime undecomposed.
The sublimed hydroquinone forms monoclinic leaf)' crystals. It
dissolves in 17 parts of water at 15°, more readily in hot water, in
alcohol, and in ether. It is but sparingly soluble in cold benzene.
An aqueous solution reduces silver nitrate solution even at ordinary
temperatures, and Fehling's solution only on warming. A small
quantity of ferric chloride produces a temporary blue coloration which
disappears on adding more ferric chloride, when small, green, shin)',
crystalline leaves (quinhydrone) separate out. In contradistinction to
catechol and resorcinol, an aqueous solution of h)droquinone is not
precipitated by either lead acetate or by the basic acetate.
Tests for Impurities.
lnor{!;anic Matter. — Not more than 05 mg. of residue should remain
on heating i g. of hydroquinone.
Quinone. — The crystals of hydroquinone should be quite colourless.
Phenol. — Ferric chloride should not produce a permanent violet
coloration in an aqueous solution, and the aqueous solution should give
no smell of phenol on boiling.
Sulphuric Acid. — Barium chloride solution should produce no
precipitate with a cold, saturated, aqueous solution of hydroquinone.
' Base, Pharm. Zeil., 1907, 52, 851.
IODOFORM 359
Iodoform.
CHI3. Molec. wt. 39377.
Iodoform forms small hexagonal plates or leafy crystals of a lemon-
yellow colour, with a smell somewhat resembling that of saffron. It
melts at about 120°, and decomposes with separation of iodine at a
higher temperature. It is soluble in 10 parts of ether, in 25 parts of
absolute alcohol, in about 70 parts of 90 per cent, alcohol, and in
75 parts of glacial acetic acid ; it dissolves also in benzene, chloro-
form, petroleum spirit, and in carbon bisulphide. It is practically
insoluble in water,^
Tests for Impurities.
Inorganic Matter. — Not more than 0-5 mg. of residue should be left
on igniting i g. of iodoform.
Alkali Iodides and Chlorides. — On shaking up i g. of iodoform with
10 c.c. of water and filtering, the filtrate should give only an immediate
opalescence with silver nitrate solution.
Alkali Carbonates and Sulphates. — Barium chloride solution should
produce no precipitate when added to an aqueous filtrate prepared as
above.
Water. — Iodoform should dissolve to a clear solution in ten times
the quantity of petroleum spirit. It should, at most, not lose more than
I per cent, in weight when dried over sulphuric acid for twenty-four
hours.
Quantitative Estimation.
About I g. of powdered iodoform is heated in a glass flask in a
boiling water-bath, and frequently shaken during one hour with 100 c.c.
of iV/io silver nitrate solution. Any yellow precipitate adhering to the
sides of the flask is then washed down into the solution with as little
water as possible, and the whole kept gently boiling over a wire gauze,
using a small Bunsen burner, for half an hour. (This operation may
also be carried out with alcoholic solutions of iodoform and silver
nitrate.) On cooling, the solution is filtered into a 250 c.c. measuring
flask, and the precipitate and filter paper afterwards washed with water
until the flask is full up to the mark. The excess of silver nitrate is
determined in 50 c.c. of the filtrate by titrating either with A710 sodium
chloride solution, or with iV/io ammonium thiocyanate solution. The
number of cubic centimetres of sodium chloride solution or of ammonium
thiocyanate solution used, multiplied by 5 and subtracted from 100,
gives the number of cubic centimetres of silver nitrate solution decom-
^ For identifying reactions, cf. Merck's Rea^.-Verz., 1908, p. 296.
360 ORGANIC PREPARATIONS
posed by the quantity of iodoform taken. This figure, multiplied by
001312, gives the amount of iodoform in the original weighing taken,
and the percentage content is thus readily calculated. A good sample
should show a percentage of at least 99-5 of iodoform when analysed by
this method.
The method may be simplified by decomposing the iodoform with
silver nitrate directly in a 250 c.c. measuring flask, and after cool-
ing making up with water to the mark. When the precipitate has
settled, 50 c.c. of the clear solution are withdrawn and titrated as
above.
The following method of estimation is also to be recommended : —
I g. of iodoform is dissolved in 100 c.c. of a mixture of i part of
ether and 3 parts of alcohol, 10 c.c. of this solution transferred to a
beaker, a few drops of fuming nitric acid added, followed immediately
by 10 c.c. oi N/10 silver nitrate solution, and the mixture then carefully
heated on the water-bath until the smell of ether and of nitrous acid
has disappeared. When cold, 100 c.c. of water and about i c.c. of iron
alum solution are added, and the excess of silver nitrate titrated with
Nlio ammonium thiocyanate solution. Not more than 2-5 c.c. of the
latter should be required.^ In carrying out this method of estimation
care must be taken to add the silver nitrate solution before the nitrous
acid has converted the iodine into iodic acid, which would render the
analysis inaccurate.-
Lactic Acid.
CH3.CHOH.COOH. Molcc. wt. 9005.
Fermentation lactic acid is a clear, colourless or slightly yellow,
odourless, syrupy liquid, miscible in all proportions with water, alcohol,
and ether. It is insoluble in benzene, chloroform, and carbon
bisulphide. The official lactic acid of the British Pharmacopoiia
has a sp. gr. of i-2i and contains 75 per cent, of pure lactic acid.
Chemically pure lactic acid is an extremely hygroscopic crystal-
line mass, which melts at 18° and boils at Ii9°-I20" under 12 mm.
pressure. The 90 per cent, commercial product is the most important
technically.
The characteristic formation of crystalline zinc and calcium salts
is too long and tedious a test for general purposes. The following
test is therefore applied: — 3 c.c. of the acid are warmed with 10 c.c.
of potassium permanganate .solution (i : 1000), when the characteristic
smell of aldehyde is given off.^
* Utz, A/>ol/t. Zeit., 1906, p. 930. ^ Z. angnv. Chem.^ 1909, 22, 1059, 1090.
3 Cf. Merck's Reag,-Verz., 1908, p. 297.
LACTIC ACID 361
Tests for Impurities.
Inorganic Matter. — On strongly heating, lactic acid chars and finally
burns away, leaving a small residue which in no case should exceed
o-i per cent.
Copper, Lead, Zinc, Iron. — Sulphuretted hydrogen water should
give no reaction with a lo per cent, aqueous solution of lactic acid.
Calcium. — An aqueous solution (i : lo) should give no precipitate
with excess of ammonia and ammonium oxalate solution.
Sulphuric Acid and Chlorine Compounds. — Neither barium chloride
solution nor silver nitrate solution should produce a precipitate with
a I : lo solution of the acid.
Butyric and Acetic Acids. — No smell of fatty acids should be evolved
on gently warming lactic acid.
Tartaric and Oxalic Acids. — No turbidity should be produced on
mixing 5 c.c. of lactic acid with 100 c.c. of lime water.
Citric Acid. — The mixture with lime water should also not become
turbid on warming.
Sugar. — On carefully pouring 5 c.c. of lactic acid over 5 c.c. of
sulphuric acid in a test tube, the sulphuric acid should not assume a
brown coloration within half an hour. The temperature of the reaction
should not be allowed to rise above i^"", otherwise lactic acid, free from
sugar, will react and produce a darkening of the sulphuric acid. Sugar
may also be tested for by means of Fehling's solution, but unless care
be taken, the separation of a very small quantity of cuprous oxide
may be overlooked.
Glycerol — 5 g. of lactic acid are warmed with an excess of zinc
carbonate, and the mixture dried at 100°. On extracting the residue
with absolute alcohol and evaporating off the alcohol on the water-
bath, no sweet-tasting residue should remain,
Mannite, Grape Sugar, Cane Sugar, Glycerol. — On dropping i c.c.
of lactic acid into 2 c.c. of ether, no temporary or permanent turbidity
should be produced.^
Sarco-Lactic Acid. — A lO per cent, aqueous solution of lactic acid
should give no turbidity on the addition of copper sulphate solution.
Malic and Glycollic Acids. — No turbidity should be produced on
adding basic lead acetate to a 10 per cent, solution of lactic acid.
(The absence of sulphuric acid being taken for granted.)
Quantitative Estimation.
For the quantitative estimation, 10 g. of lactic acid are dissolved
in 1000 c.c. of water. 100 c.c. of this solution are warmed in a flask,
in a boiling water-bath, for ten minutes with 15 c.c. ofTV^r potassium
1 Cf. Pharm. Zentralh., 1892, p. 676.
362 ORGANIC PREPARATIONS
hydroxide, and then titrated with Nji hydrochloric acid, using phenol-
phthalein as indicator, i c.c. of Nji potassium hydroxide solution
corresponds to 009048 g. of lactic acid. The warming with potassium
hydroxide is necessary in order to convert any acid present as
anhydride into the acid (in the 75 per cent, acid a quantity of anhy-
dride is present, corresponding to about 15 per cent, of acid), otherwise
the titration would lead to an erroneous result. For this reason it is
not advisable to directly titrate a freshly made-up solution of lactic
acid with potassium hydroxide solution.
F. Ulzer and H. SeideP give the following method: — 10 g. of
lactic acid are dissolved in water and made up to i litre. 100 c.c. of
this solution are taken, and a concentrated solution of potassium
hydroxide added until the solution contains 3 g. of potassium hydroxide,
when a 5 per cent, potassium permanganate solution is added, with
shaking, until the colour of the solution changes from green to violet.
The solution is then heated to boiling, which should not discharge
the violet coloration, and, after cooling, hydrogen peroxide is added
until the coloration is discharged. The solution is then again boiled,
filtered, the filter paper washed, and the oxalic acid produced in the
reaction precipitated as calcium oxalate after acidifying with acetic
acid. The calcium oxalate is ignited and weighed as calcium oxide.
From the weight of calcium oxide, the corresponding quantity of oxalic
acid and of lactic acid may be calculated.
Methyl Alcohol (Wood Spirit).
CH3.OII. Molec. wt. 32-03.
Methyl alcohol is a clear, colourless liquid, possessing a characteristic
smell. It has a sp. gr. of 0798, boils at 65°-66°, and is miscible in all
proportions with water, alcohol, ether, and with fatty and essential oils.
Tests for Impurities.
Non-volatile Matter. — No appreciable residue should remain on
evaporating 30 c.c. of methyl alcohol on the water-bath.
Acetone and Ethyl Alcohol. — On shaking together 50 c.c. of 2N
sodium hydroxide solution and 5 c.c. of methyl alcohol in a cylinder,
then adding 25 c.c. of 2N iodine solution, and again shaking, there
should be no separation or smell of iodoform. G. Deniges- has
published a method for detecting traces of acetone, using mercuric
sulphate, by means of which he claims that 0003 per cent, of acetone
can be detected.
Evipyreuviatic Matter. — i c.c. of methyl alcohol should dissolve in
1 Monatsh., 1897, 18, 138 ; /. Chfm. Soc. Ahstr., 1897, 72, 389.
'^ Merck's Reag.-l'erz., 1 908, p. 56.
METHYL ALCOHOL 363
lo c.c. of water without turbidity. No coloration or only a faint yellow
coloration should be produced on adding 5 c.c. of concentrated sulphuric
acid gradually to 5 c.c. of methyl alcohol, the mixture being cooled
during the addition.
CiUoroforni. — No smell of isonitrile should be evolved on heating to
boiling 10 c.c. of methyl alcohol with a mixture of 3 drops of aniline
and 10 c.c. of alcoholic potash (10 per cent.).
Aldehyde. — On shaking 10 c.c. of methyl alcohol with 10 c.c. of
sodium hydroxide solution (i : 3), the mixture should remain colourless.
Substances oxidised by Permanganate. — The pink coloration pro-
duced by the addition of a drop of yV/io potassium permanganate
solution to 10 c.c. of methyl alcohol should not completely fade away
within ten minutes.
In addition to chemically pure methyl alcohol, other qualities come
on to the market which only partially satisfy the requirements given
above. The examination of wood naphtha is described in the section
on "Alcohol, Potable Spirits, and Liqueurs," p. 715.
Quantitative Estimation.
The estimation of methyl alcohol in mixtures of the alcohol and
water is effected by means of the specific gravity. A Table of the
specific gravities of such mixtures, giving the percentages of methyl
alcohol by weight, is included in the section on " Organic Dyes," Vol.
II., Part II., p. 894.
In other cases methyl alcohol is generally estimated by determining
the amount of methyl iodide produced from a known quantity of the
alcohol, a method due originally to Krell, which has been worked out by
M. Grodzky and G. Kramer.^ For this purpose 30 g. of amorphous
phosphorus are placed in a small 60 c.c. flask fitted with an upright
condenser, and after allowing 10 c.c. of methyl alcohol to drop in from
a small separating funnel, 10 c.c. of a solution of i part of iodine in i
part of hydriodic acid (sp. gr. 1-7) are added. After the solution has
digested for a short time, the contents of the flask are allowed to cool,
the flask connected up with an ordinary condenser, and the contents
distilled off on the water-bath, the distillate being collected in a
graduated glass cylinder containing some water. When the distillation
is ended, the condenser is washed out with water, the distillate
well shaken, and the number of cubic centimetres of separated methyl
iodide read off at 15".
The form of this method, as used for the estimation of methyl
alcohol in wood naphtha, is described on p. 716,
Quantitative Estimation in presence of Ethyl Alcohol. — For the
' Ber., 1874, 7, 1492.
364 ORGANIC PREPARATIONS
estimation of methyl alcohol, in presence of ethyl alcohol, the method of
T. E. Thorpe and J. Holmes,^ which depends upon the oxidation of the
methyl alcohol to carbon dioxide, is reliable and accurate. The
process is described in detail in the section on " Alcohol, Potable
Spirits, and Liqueurs," p. 717.
Estiuiation of Acetone. — G. Kramer's method for estimating acetone
in methyl alcohol has been described above as a method for the
quantitative estimation of acetone (p. 309).
For the estimation of acetone in methyl alcohol, i c.c. of the sample
is shaken in a stoppered measuring cylinder with 10 c.c. of 2N
sodium hydroxide solution, and 5 c.c. of 2N iodine solution added.
After standing for some time, 10 c.c. of ether are added, the mixture
again shaken, the volume of the separated ether layer read off, and an
aliquot part, about 5 c.c, withdrawn, allowed to evaporate on a clock-
glass, and the residual iodoform dried over sulphuric acid and weighed.
3-94 g. iodoform correspond to 0-58 g. of acetone.
The following volumetric modification of this method is due to
J. Messinger^: — 20 c.c. of potassium hydroxide solution (56 g. to the
litre) and i c.c. of methyl alcohol arc shaken up together in a 250 c.c,
stoppered flask, and 20-30 c.c. of A7s iodine solution run in from a
burette. The contents of the flask are shaken for about half a minute
until the liquid clears, when 20 c.c. of hydrochloric acid (sp. gr. 1-025)
and A710 sodium thiosulphate solution, in excess, are added. The
solution is then titrated back with A75 iodine solution, using starch
solution as indicator.
I mol. of acetone (58-048 g.) requires 3 mols. of iodine (761-52 g.)
for the formation of iodoform, in accordance with the equations : —
2CH.j.CO.CH., + 6I, + 6KOII = 2CH3. CO . Cl3+6KI+6H._,0.
2CH3.CO.CI3+2KOH = 2CHl3+2KC2H,0.,.
761-52:58-048 = I:A
1 = quantity of iodine, A = quantity of acetone
Hence, A = i . 5|:24^ _ 007623 1.
761-52
The quantity of acetone (in grams) in 100 c.c. of methyl alcohol is
therefore found by multiplying the quantity of iodine used up by
7-623. The percentage content by weight is calculated from the
specific gravity of the methyl alcohol.
The following method for the estimation of acetone in methyl
alcohol, due to S. J. M. Auld,^ is based on the formation of bromoform
and its subsequent saponification by alcoholic potassium hj-dro.xide.
The sample is diluted with water, so that the solution to be tested
' /. Chem. Soc, 1904, 85, l. - />V/., 1888, 21, 3366,
•' y. Soc. Chem. I ml., 1906, 25, 1 00.
METHYL ALCOHOL. MORPHINE 365
contains from o- 1-0-2 g. of acetone, and the latter placed in a flask
fitted with an upright condenser and dropping funnel. After adding
20-30 CO. of potassium hydroxide solution (10 per cent.), a solution of
bromine (200 g. bromine and 250 g. potassium bromide to a litre of
water) is added from the dropping funnel until the mixture has acquired
a faint yellow tinge. The whole is then warmed on the water-bath, at
about yo", the bromine solution being added, drop by drop, until a
slight coloration remains permanent. The excess of bromine is
removed by boiling for a short time with potassium hydroxide solution,
and the bromoform then distilled off. The condenser is washed down
with alcohol, and 50 c.c. of alcohol and sufficient potassium hydroxide
added to produce a distillate containing about 10 per cent, of potassium
hydroxide. The bromoform is then saponified by boiling for about
three-quarters of an hour, using a reflux condenser, and, when cold, the
contents of the flask are neutralised with nitric acid and made up to
500 c.c. with water. The solution is then titrated in the usual way
with Njio silver nitrate solution. 239-76 parts of bromine correspond
to 58-048 parts of acetone.
Morphine.
C17H19O3N . H,0. Molec. wt. 303-18.
Morphine crystallises in colourless needles or prisms which lose
their water of crystallisation at i io°-i20", and melt at about 230". It
is only very sparingly soluble in water (about i : 5000) and the aqueous
solution is laevorotatory ; it dissolves in lOO parts of 90 per cent, alcohol,
in 50 parts of absolute alcohol, in lOO parts of chloroform, and in 1200
parts of ether. It is practically insoluble in benzene.
It is examined in the same way as morphine hydrochloride. (Cf.
infra.)
The free base may be estimated volumetrically by treating with an
excess of Njio hydrochloric acid, and after adding water, ether, and
iodo-eosine as indicator, titrating back with Ayio potassium hydroxide.
I c.c. of iV/io hydrochloric acid corresponds to 0-02852 g. of anhydrous
morphine, or to 003032 g. of C^yH^gNOg. H.^O.
Morphine Hydrochloride.
Ci^H.gOaN . HCl . 3H,0. Molec. wt. 375-68.
Morphine hydrochloride crystallises in white, silky, non-efflorescent
needles, which generally come on to the market compressed into cubes.
It is soluble in 25 parts of water and in 50 parts of 90 per cent,
alcohol. From the cold, saturated solution the salt is partially thrown
366 ORGANIC PREPARATIONS
down on the addition of concentrated hydrochloric acid. A deep red
coloration is produced on heating a few small crystals for a quarter of
an hour in a water-bath with 5 drops of sulphuric acid, allowing to
cool, and then adding i drop of nitric acid. A mixture of o-i g. of
morphine hydrochloride and 0-4 g. of cane sugar, added to sulphuric
acid, colours the latter red ; the coloration is intensified by adding
bromine water. On moistening with nitric acid, morphine h)dro-
chloride becomes coloured red. A solution of morphine h)-drochloride
in sulphuric acid turns brown on the addition of basic bismuth nitrate.
Tests for Impurities.
Inorganic Impurities. — On heating, 03 g. of morphine hydrochloride
should burn away, leaving not more than 05 mg. of residue.
On igniting morphine, there always remains a visible, not insigni-
ficant residue, and it is only by weighing that it is possible to ascertain
with certainty whether it is negligible.
Free Hydrochloric Acid. — The aqueous solution should react neutral
with litmus paper.
Sugar and Organic Impurities. — Morphine hydrochloride should
dissolve in sulphuric acid, producing a colourless or, at most, a faint
pink-coloured solution.
Foreign Alkaloids. — On adding a drop of potassium carbonate
solution (1:3) to 5 c.c. of an aqueous solution of morphine hydro-
chloride (i : 30), a pure white, crystalline separation takes place "
immediately or in the course of a iow seconds, which should remain
colourless in contact with air, and on shaking up with chloro-
form the latter should not be reddened (apomorphine). Instead
of potassium carbonate, potassium bichromate may also be used,
which brings about an immediate oxidation. On shaking with
chloroform, the latter is immediately turned red if apomorphine
be present. The addition of a drop of ammonia to 5 c.c. of an
aqueous solution (i : 30) produces an immediate white, crystal-
line precipitate, which should dissolve readily in sodium hydroxide
solution, and slowly in ammonia or lime water, giving colourless
solutions. On shaking up the sodium hydroxide solution with
ether, the clear ethereal extract should yield no appreciable residue
on evaporation. (A residue points to the probable presence of
narcotine.)
Water. — On drying i g. of morphine hydrochloride at lOO' till
constant, at least 0856 g. of residue should remain.
The methods for the examination of the two most important
derivatives of morphine, viz., codeine and dionine, are appended.
CODEINE. DIONINE 367
Codeine (Methyl Morphine).
Ci7Hj70N(OH)(OCH3) + H.30. Molec. wt. 317-19.
Codeine forms colourless crystals which are soluble in 80 parts of
cold, and in 17 parts of boiling water. It is readily soluble in alcohol,
ether, and chloroform. On drying at 100^, it loses 5-68 per cent, in
weight. Anhydrous codeine melts at 153°. The free codeine base
may be estimated volumetrically in the same way as morphine
(P- 365). I c.c. of Njio hydrochloric acid corresponds to 0-03172 g. of
codeine +H2O.
The salt of codeine which finds the widest application is the
phosphate, Ci^Hi^ONCOHXOCHg). H3PO, + 2H20. Molec. wt. 433-234.
It crystallises in fine white needles, soluble in 3-5 parts of water, and
less soluble in alcohol. Its aqueous solution reddens litmus paper.
Codeine phosphate dissolves in sulphuric acid to a colourless solution,
sometimes exhibiting a transitory pale red coloration ; on adding a
drop of ferric chloride, the mixture turns blue on warming ; when cold,
a drop of nitric acid changes the blue coloration to a deep red
Tests for Impurities.
Sulphuric and Hydrochloric Acids. — An aqueous solution (1:20),
acidified with nitric acid, should show no change with silver nitrate
solution, and barium nitrate solution should produce no immediate
turbidity.
Morphine. — A solution of a small piece of potassium ferricyanide in
10 c.c. of water, to which is added a drop of ferric chloride, should not
be turned blue immediately on the addition of i c.c. of an aqueous
solution of codeine phosphate (i : 100).
Water. — Codeine phosphate should not lose more than 8-5 per cent,
in weight on drying at 100".
Quantitative Estimation.
This may be carried out by dissolving a weighed quantity of the
salt in water, making alkaline with sodium carbonate solution,
extracting with ether, and titrating the ethereal codeine solution
obtained with A^/io hydrochloric acid, using iodo-eosine as indicator.
Dionine (Ethyl Morphine Hydrochloride).
Ci7Hi80.3N(OC.,H5)HCl + 2H,0. Molec. wt. 385-69.
Dionine is a white, crystalline powder consisting of fine small
needles soluble in 12 parts of water and in 25 parts of alcohol (of
about 85 per cent, by weight). The solution in water reacts neutral
368 ORGANIC PREPARATIONS
with litmus paper. On adding a solution of iodine in potassium iodide
to the aqueous solution (i : lOO), a light brown precipitate is thrown
down, ooi g. of dionine dissolves in lo c.c. of sulphuric acid (sp. gr.
1-84) with evolution of hj'drochloric acid, a clear, colourless solution
resulting which, when warmed with a drop of ferric chloride solution,
first turns green, then deep blue, and on the further addition of
2-3 drops of nitric acid, the colour changes to deep red.
Tests for Impurities.
Codeine. — i or 2 drops of ammonia (10 per cent. NH3) added to a
solution of 01 g. of dionine in i c.c. of water, produces a white pre-
cipitate which is not dissolved on the further addition of 10-15 drops
of ammonia. (Under similar conditions codeine goes readilv into
solution.)
Morpliine. — A solution of a small crystal of potassium ferricyanide
in 10 c.c. of water, to which a drop of ferric chloride solution is added,
should not turn immediately blue, but should only very slowly develop
a bluish -green coloration on the addition of i c.c. of an aqueous
solution of dionine (i : 100). (Morphine gives an immediate deep blue
coloration.)
Inorganic Impurities. — Not more than 05 mg. of residue should
remain on igniting i g. of dionine.
Water. — On drying at 100 , dionine should not lose more than
9-5 per cent, in weight.
Quantitative Estimation.
The dionine (0-25 g.) is dissolved in 50 c.c. of absolute alcohol
in a glass-stoppered flask, and the solution titrated with iV/io potassium
hydroxide, using Poirrier's blue as indicator {cf. Quinine, p. 381). i c.c.
oi N/io potassium hydroxide corresponds to 00386 g. of dionine.
a-Naphthol.
Ci(,H. .OH. Molec. wt. 14406.
u-Naphthol crystallises in colourless needles possessing a phenol-
like smell. It melts at 97" and boils at 280". It is sparingly soluble
in water, but readily in alcohol, ether, benzene, and chloroform.
Qualitative Tests.
I. An aqueous .solution of a-naphthol gives a violet coloration with
calcium hypochlorite .solution, and also with a solution of iodine in
potassium iodide on the addition of an excess of sodium hydroxide
solution.
NAPHTHOL 369
2. Ammonia produces a blue fluorescence when added to an aqueous
solution.
3. An alcoholic solution (1:5) gives a violet coloration with ferric
chloride ; the coloration disappears on standing for some time.
4. On melting 0-5 g. of a-naphthol with 12 g. of chloral hydrate for
ten minutes in a boiling water-bath, the mass turns red, and dissolves in
alcohol, producing a red coloration.
5. If o-l g. of vanillin be dissolved in 2 c.c. of sulphuric acid, and
then o-i g. of a-naphthol added, a very stable red coloration is produced
after shaking for some time.^
Tests for Impurities.
Inorganic Acids. — On shaking i g. of a-naphthol with lOO c.c. of
water, the filtrate should not redden blue litmus paper.
Organic Impurities insoluble in Sodium Hydroxide. — i g. of a-naphthol
should dissolve completely to a clear solution in 5 c.c. of sodium hydroxide
solution of sp. gr. i- 168- 1-172 and 5 c.c. of water.
Inorganic Matter. — No appreciable residue should remain on ignit-
ing I g. of a-naphthol.
Quantitative Estimation.
The acidimetric method for the estimation of a-naphthol is described
in the section on " Organic Dyes," Vol. II., Part II., p. 882.
^-Naphthol.
C10H7 . OH. Molec. wt. 144-06.
/3-Naphthol forms colourless, glistening, odourless, rhombic crystals,
which melt at 128°, and boil at 285°-290° with slight decomposition.
Qualitative Tests.
1. Calcium hypochlorite solution gives a yellow coloration with an
aqueous solution of /3-naphthol ; the coloration disappears if a slight
excess of the reagent be added. /3-Naphthol gives no coloration with a
solution of iodine in potassium iodide containing excess of sodium
hydroxide.
2. Ammonia produces a violet fluorescence when added to an
aqueous solution.
3. An alcoholic solution (i : 5) gives a stable green coloration with
ferric chloride.
4. On melting 0-5 g. of /5-naphthol with 12 g. of chloral hydrate for
ten minutes in a boiling water-bath, the mass turns a deep blue, and
dissolves in alcohol, producing a blue coloration.
^ For other colour reactions, cf. Merck's Reag.-Verz., 1908, p. 297.
Ill 2 A
370 ORGANIC PREPARATIONS
5. If 01 g. of vanillin be dissolved in 2 c.c. of sulphuric acid, and
then o-i g. of /3-naphthol added, the solution turns a chlorophyll-green
colour.
Tests for Impurities.
a-Naphthol. — If i g. of /5-naphthol be dissolved in 100 c.c. of boiling
water, and the solution cooled and filtered, the filtrate should not show
a violet coloration on the addition of excess of calcium hypochlorite
solution. Other methods for the detection of a-naphthol, and for the
differentiation of the two isomers, are described in the section on
"Organic Dyes," Vol. II., Part II., pp. 881 et scq.
Naphthalene. — i g. of /3-naphthol should dissolve completely, leaving
no residue, in 50 c.c. of ammonium hydroxide (sp. gr. 0-96).
Organic Impurities. — The above ammoniacal solution should not
have a brownish colour, but should only be pale yellow.
Organic Acids. — On shaking i g. of ^^-naphthol with 100 c.c. of
water and filtering, the filtrate should not redden blue litmus paper.
Quantitative Estimation.
F. W. Kiister's method for the acidimetric estimation of ;8-naphthol
by means of its picric acid compound, is described in the section on
" Organic Dyes," Vol. II., Part 1 1., p. 882.
Oxalic Acid.
C.3H.O,. 2H,0. Molec. wt. 126-05.
Oxalic acid crystallises in colourless, monoclinic crystals, which should
show no signs of efflorescence. It dissolves in 10 parts of water at 15°,
in about 3 parts of boiling water, in 2-5 parts of alcohol at 15 , in i-8
parts of boiling alcohol, and in about 100 parts of ether. The hydratcd
acid heated in a capillary tube melts in its water of crystallisation at
98'; the anhydrous acid melts at 187°. On heating oxalic acid with
sulphuric acid, carbon monoxide and carbon dioxide are evolved.
Calcium chloride, added to an aqueous solution containing excess of
ammonia, produces a white precipitate, insoluble in acetic, but soluble
in hydrochloric acid.
Tests for Impurities.
Inorganic Matter. — No appreciable residue should remain on igniting
3 g. of oxalic acid.
Amvioniiim Compounds. — On treating 2-5 g. of oxalic acid with 5 g.
of potassium hydroxide dissolved in 30 c.c. of water, and then adding
OXALIC ACID. PARALDEHYDE 371
15 drops of Nessler's reagent to the solution, only a pale yellowish
coloration, and not a reddish-brown coloration should result.
Heavy Metals. — An aqueous solution (i : 10) should be perfectly
clear. 30 c.c. of this solution should show no reaction on the addition
of sulphuretted hydrogen water, or on the subsequent addition of
ammonia, till alkaline. •
Chlorides. — At most, only a faint opalescence should be produced
on adding silver nitrate solution to a solution of 5 g. of oxalic acid in
50 c.c. of water acidified with 15 c.c. of nitric acid.
Sulphuric Acid. — No turbidity or precipitate should be produced on
warming an aqueous solution (5 : 100), acidified with hydrochloric acid,
with barium chloride solution within fifteen hours.
Nitric Acid. — On carefully pouring a 10 per cent, solution of oxalic
acid on to 10 c.c. of a solution of diphenylamine in sulphuric acid, no
blue ring should be visible at the junction of the two layers of liquid.
Quantitative Estimation.
I g. of oxalic acid is dissolved in water and made up to 100 c.c,
25 c.c. of which are titrated hot with TV/S potassium hydroxide solution,
using phenolphthalein as indicator, i c.c. of A'/s potassium hydroxide
corresponds to 0-012605 g. of crystallised oxalic acid.
As an alternative method 25 c.c. of the above aqueous solution
(i : 100) are titrated with A710 potassium permanganate solution after
adding 6-8 c.c. of concentrated sulphuric acid, and warming to about 60°.
I c.c. of iV/io potassium permanganate = 0-0063025 g, of crystallised
oxalic acid.
A Table of the specific gravity of aqueous solutions of oxalic acid is
given in the section on "Organic Dyes," Vol. II., Part II., p. 898.
Paraldehyde.
(CH3COH)3. Molcc. wt. 132.10.
Paraldehyde is a clear, colourless liquid with a peculiar, not irritating
smell. It has a sp. gr. of 0-997-1-000, boils at 123°- 12 5° solidifies
below 10^, and melts at io°-5. According to W. Squire,^ absolutely
pure paraldehyde melts at 11^-7. Paraldehyde is readily soluble in
alcohol, ether, benzene, chloroform, and petroleum spirit; it dissolves
in 10 parts of water. A cold, saturated solution becomes turbid
on warming.
Tests for Impurities.
Inorganic Matter. — 20 c.c. of paraldehyde should volatilise completely
on hearing, leaving no residue.
' Chem. and Drug.^ 1890, 37, 852.
372 ORGANIC PREPARATIONS
Hydrochloric aud SuIpJiuric Acids. — Neither silver nitrate nor barium
nitrate solution should produce any precipitate in an aqueous solution
(i : lo) acidified with nitric acid.
Acetic and Valeric Acids. — lo c.c. of paraldehyde are dissolved in
50 c.c. of alcohol, and phenolphthalein added ; not more than 0-5 c.c.
of 7V/i potassium hydroxide should be required to produce the pink
coloration.
Alcohol. — The presence of alcohol is indicated by a too low specific
gravity, melting point, and boiling point. On shaking up 20 c.c. of
paraldeh}-de with 20 c.c. of a saturated solution of calcium chloride, the
volume of the latter should show no increase.
Water. — Paraldehyde should dissolve to a perfectly clear solution in
an equal volume of official paraffin oil (liquid paraffin).
Aldehyde. — On shaking up 10 c.c. of paraldehyde with 10 c.c. of 5
per cent, potassium hydroxide solution, the latter should show no yellow
or brown coloration within half an hour.
Valeraldehydc. — No disagreeable smelling residue should remain on
evaporating 10 c.c. of paraldeh)'de down on the water-bath.
Amy I Alcohol. — The aqueous solution (i : 10) should be perfectly
clear and contain no oily drops.
Phenacetine.
oaH,(i)
CgH/ . Molec. wt. 179-11.
^NH . COCH3(4)
Phenacetine forms colourless, odourless, and tasteless, small, leafy
crystals, which melt at 135°. It dissolves in 1400 parts of water at 15',
in 70 parts of boiling water, and in 16 parts of alcohol.
On boiling i g. of phenacetine with 10 c.c. of hydrochloric acid for
about a minute, diluting with 100 c.c. of water, allowing to cool and
filtering, the filtrate gradually assumes an intense red colour on adding
1-2 c.c. of chromic acid solution (3 : 100).^
Tests for Imptirities.
Inorganic Matter. — Not more than 0-5 mg. of residue should remain
on igniting 0-5 g. of phenacetine.
Orga7iic Impurities. — No brown coloration or carbonisation should
be produced on dissolving 0-5 g. of phenacetine in 10 c.c. of sulphuric
acid.
Acctanilide. — On heating 0-5 g. of phenacetine with 8 c.c. of water to
boiling, allowing to cool and filtering, the filtrate should show no
reaction on boiling with potassium nitrite and dilute nitric acid, and
' For identifying reactions for phenacetine, cf. Merck's Reag.-Verz., 1908, p. 298.
PHENACETINE 373
again boiling with nitric acid containing nitrous acid. According to
J. Schroeder,^ 2 per cent, of acetanilide may be thus detected by the
production of a red coloration.
On boiling 0-3 g. of phenacetine for about one minute with 3 c.c. of
25 per cent, hydrochloric acid, diluting with 30 c.c. of water and filtering,
10 drops of 3 per cent, chromic acid solution should produce a stable
ruby-red but not a green coloration.-
Phenol. — If o-i g. of phenacetine be dissolved in 10 c.c. of hot water,
the solution allowed to cool and then filtered, the filtrate should show
no turbidity on adding excess of bromine water.
Free Acids or Bases. — A 5 per cent, alcoholic solution of phenacetine
should give no reaction with either red or blue litmus paper.
Para-Phenetidene. — On stirring i g. of phenacetine into 5 g. of
molten chloral hydrate, a clear and colourless melt should result.
The mixture should not be heated in the steam - bath for longer
than two to three minutes, otherwise pure phenacetine turns a rose-
red colour. In the presence of^-phenetidene the melt becomes coloured
violet.^
As an alternative test, 0-5 g. of phenacetine is dissolved by warming
with 2 c.c. of alcohol, and 5 c.c. of iodine in potassium iodide solution
(0-05 iodine : 1000) added. The solidified mass of separated phena-
cetine is heated to boiling till dissolved. In the presence of traces
of /-phenetidene the solution turns rose-red. The colour is more
marked if the phenacetine be separated out a second time.*
Ortho- and Diamino-Conipounds. — It is not usually necessary to test
for these, since the commercial product is practically always free from
such compounds as impurities.^
Para-CJdoracetanilide. — An adulteration with this substance is
indicated by a low melting point. The chlorine may be detected by
igniting the phenacetine with calcium carbonate in a similar manner to
that by which benzoic acid is tested for chlorobenzoic acid^ (p. 321).
Quantitative Estimation.
A method for the quantitative estimation of phenacetine in mixtures
has been worked out by J. L. Turner and C. E. Vanderkleed.''
1 Z.anal. C/iem., 1889, 28, 376. - Union pharmac.^ 1905, p. 484.
3 Reuter, Phartn. Zeif., 36, 185 ; cf. also Pharm. Zentralh., 32, 313,
■* Goldmann, Pharm. Zeit.^ 36, 208.
* A method of testing for these compounds is given in Pharm. Zentralh., 31, 65, and 32, 313.
^ Cf. Sudd, Apoih. Zeit.^ 1906, p. 236 ; C. Mannich, Ber. Pharm., 1906, p. 57 ; /. Soc. Chem.
Ind., 1906, 25, 495.
' Amer.J. Pharm., April 1907 ; J. Soc. Chem. Ind., 1907, 26, 486.
374 ORGANIC PREPARATIONS
Phenyldimethyl pyrazolone (Antipyrine).
N(CH3).C— CH3
C6H5.N/ II . Molec. vvt. I88-I2.
\C0 CH
Antipyrine crystallises in colourless plates possessing a slightly
bitter taste. Melting point i io"'-i 12'. It dissolves in i part of water,
I '5 parts of chloroform, and in 80 parts of ether. A solution of tannic
acid added to an aqueous solution of antipyrine (i : 100) gives a
voluminous white precipitate. 2 drops of fuming nitric acid added to
2 c.c. of an aqueous solution produce a green coloration, and after
boiling, the addition of a further drop of the acid causes a red coloration.
A drop of ferric chloride solution added to 2 c.c. of an aqueous solution
(i : 1000) produces a deep red coloration, which changes to a bright
yellow on adding 10 drops of sulphuric acid.^
Tests for Impurities.
The aqueous solution of antipyrine (i : i) should be clear and
colourless. It should react neutral and remain unchanged on adding
sulphuretted hydrogen water. A solution of i g. of the preparation in
5 c.c. of water .should show no reaction on heating to boiling with 3
drops of silver nitrate solution. No appreciable residue should remain
on igniting o-i g. of antipyrine
Quantitative Estimation.^
This may be carried out by means of iodine either volumetrically,
the antipyrine being converted into the periodide of its hydriodide,
CiiHioN.iO. HI. I.,, and the excess of iodine being titrated back with
sodium thiosulphate, or gravimetrically by the method of the French
Codex, in which the antipyrine is precipitated and weighed as the
difficultly soluble iodo-antipyrine, which contains 70 per cent, of iodine.^
Phenylhydrazine.
CcH., . NH . NH,. Molec. wt. 10808.
Phenylhydrazine is a colourless or pale yellow, slightly refractive
liquid, which boils at 243°, and on cooling solidifies in monoclinic plates
which melt at 19". Phenylhydrazine forms a crystalline hydrate with
' For other identifj'ing reactions, cf. Merck's Reag.-Verz,^ 1908, p. 290; also G. Lander and
H. Winter, Analyst, 1 91 3, 38, 97.
2 Cf. C. Kippenberger, Z. anal. Chem., 1896, 35, 675 ; /. Soc. Chem. Ind., 1896, 15, 266. J.
Bougault,/. /'harm. Chim., 1900, II, 97 ; /. Soc. Chem. hid.., 1900, 19, 269.
^ Cf. C. Astre,/. Pharm. C/iim,, 1912, 6, 2ll ; /. Soc, Chem. /«</., 1912, 31, 898.
PHENYL HYDRAZINE 375
water (2CgH5.N2H3. +H2O), which melts at 25°. It is but sparingly
soluble in cold water, more so in hot, and very readily in alcohol and
ether. It reduces Fehling's solution in the cold. If an aqueous or
alcoholic solution of phenylhydrazine be heated for a short time
with a few drops of an aqueous solution of trimethylamine, and
then a few drops of a solution of sodium nitroprusside added, an
intense cherry - red coloration is produced. On warming 5 c.c. of
a solution of i g. of phenylhydrazine and 2 g. of sodium acetate
in 15 c.c. of water and 1-5 g. of hydrochloric acid (sp. gr. M24)
with 10 c.c. of grape sugar solution (i : 100) in a boiling water-
bath, fine yellow needles of phenyl glucosazone begin to separate in
about ten minutes ; an additional separation takes place on further
heating.
Tests for Impurities.
A clear solution should result on dissolving 2 g. of phenylhydrazine
in 20 c.c. of 5 per cent, acetic acid.
Quantitative Estimation.
A method for the quantitative estimation of phenylhydrazine has
been worked out by H. Causse.^ It is based on the reduction of arsenic
acid by means of phenylhydrazine to arsenious acid with formation of
nitrogen and phenol, according to the following equation : —
AsA+CfiHgNH.NHa = Ns + CeH^OH-f AsgOg+H.O.
The estimation is carried out as follows : — 0-2 g. of phenylhydrazine
and 60 C.C. of arsenic acid solution (125 g. of pure arsenic acid are dis-
solved by heating on the water-bath in 450 c.c. of water and 1 50 c.c, of
pure, concentrated hydrochloric acid ; when cold, the solution is filtered,
and made up to 1000 c.c. with glacial acetic acid) are gently heated in
a round-bottomed 500 c.c. flask, fitted with upright condenser, until the
evolution of gas has subsided ; the contents of the flask are then boiled
for about forty minutes. When cold, 200 c.c. of water are added, and
the solution made faintly alkaline (until phenolphthalein just turns
pink) with a solution of sodium hydroxide containing 200 g. of sodium
hydroxide to the litre. The solution is then made just acid with
hydrochloric acid, 60 c.c. of a cold, saturated solution of sodium
bicarbonate added, and the arsenious acid finally titrated with A710
iodine solution, i c.c. of the latter corresponds to 0-002702 g. of
p?ienylhydrazine.
1 Comptes rend.^ 1897, 125, 112 \ J. Soc, Chem. Ind., 1898, 17, 76.
376 ORGANIC PREPARATIONS
Phthalic Acid.
COOH(i)
CgH^/ . Molcc. wt. 166-05.
\COOH(2)
Phthalic acid crystalHses in small, colourless plates or prisms melting
at 213'' and soluble in 200 parts of water, 10 parts of alcohol, and 145
parts of ether; it is only very sparingly soluble in chloroform, and is
insoluble in benzene and in petroleum spirit. On heating to about 130°,
it is gradually converted into phthalic anhydride and water.
Phthalic Anhydride.
CO
QH / >0. Molec. wt. 148-032.
\co/
Phthalic anhydride crystallises in long, colourless needles which melt
at 128° and boil at 277°. It dissolves in boiling water forming phthalic
acid, and in alcohol, ether, benzene, and chloroform, whilst it is only
sparingly soluble in petroleum spirit. The anhydride commences to
. sublime below its melting point.
A dilute, aqueous solution of phthalic acid gives a white precipitate
(even at a dilution of i : 10,000) with lead acetate, the precipitate being
readily dissolved by nitric acid, but only soluble with difficulty in excess
of acetic acid. On melting phthalic anhydride with resorcinol in a test
tube, and dissolving the cold melt in alkali, the alkaline solution, when
poured into a large volume of water, produces a highly fluorescent
solution due to the formation of fluorescein.
Tests for Impurities.
Inorganic Matter. — Not more than 0-5 mg. of residue should be left
on igniting i g. of phthalic acid.
Hydrochloric Acid. — Only a faint opalescence should be produced on
adding silver nitrate solution to a solution of i g. of phthalic acid in
25 C.C. of boiling water.
Chlorine Componnds. — 0-5 g. of phthalic acid is mixed with i g. of
calcium carbonate free from chloride, rroistened with water, dried, and
ignited. On dissolving the ignited residue to a volume of 20 c.c. in
nitric acid and water, and adding silver nitrate solution, only a faint
opalescent turbidity should be produced.
Benzoic Acid. — i g. of phthalic acid is shaken up with 20 c.c. of
benzene and filtered. No residue should be left on evaporating the
filtrate. Since the anhydride is soluble in benzene it should first be
PHTHALIC ACID. PYROGALLOL 377
converted into the acid by dissolving in hot water, evaporating and
drying at loo^.
For technical purposes, e.g. in the colour industry, it suffices if the
anhydride melts at 128°, is soluble in benzene, and volatilises without
leaving any residue, Dichlorophthalic acid and tetrachlorophthalic acid,
used in the preparation of eosin dyes, melt at i83°-i85° and 250°
respectively, the latter formii.g an anhydride.
1 :3 Phthalic Acid (Isophthalic acid) crystallises in long, fine needles
which melt above 300", and dissolve in about 4000 parts of water, but
are more soluble in alcohol. It is insoluble in benzene, chloroform, and
petroleum spirit.
1 :4 Phthalic Acid (Terephthalic acid) crystallises in small, needle-
like crystals, which sublime on heating without melting. It is insoluble
in benzene and petroleum spirit, and but very sparingly soluble in
water, ether, and chloroform.
Quantitative Estimation.
I g. of phthalic acid or anhydride is dissolved in 20 c.c. of Nji
sodium hydroxide and 20 c.c. of water, and then titrated with Nji
hydrochloric acid, i c.c. of N/i sodium hydroxide, used in neutralisa-
tion, corresponds to 0-08302 g. of phthalic acid, or to 0-07402 g. of
phthalic anhydride.
Pyrogallol.
CoH3(OH)3 [1:2: 3]. Molec. wt. 126-05.
Pyrogallol crystallises in colourless, glistening needles or small
plates which melt at 131°. It dissolves in 1-7 parts of water, in 1-5 parts
of alcohol, in 1-5 parts of ether, and sparingly in benzene, chloroform,
and carbon bisulphide. The aqueous solution reacts faintly acid. An
aqueous solution is coloured blue by a freshly prepared solution
of ferrous sulphate, brownish-red by ferric chloride, and is blackened by
silver nitrate solution.^
Tests for Impurities.
Inorganic Matter. — No appreciable residue should be left on igniting
I g, of pyrogallol.
Gallic Acid. — 2 g. of pyrogallol should dissolve to a perfectly clear
solution in 5 c.c. of ether (sp. gr. 0-72). o-i per cent, of gallic acid
is thus readily detected, either a turbid solution being produced or a
small amount of crystalline residue remaining undissolved.
^ For identifying and colour reactions, cf. Merck's Reag.-Verz.^ 1908, p. 299.
378 ORGANIC PREPARATIONS
Quinine.
C20H24O2N2. Molec. \vt. 324-21.
Pure quinine comes into commerce chiefly as the hydrate
C.,oHo40.,N., + 3H.,0. It is a white, crystalline, bitter-tasting powder
which readily effloresces in the air, but which only loses its water
of crystallisation completely by prolonged drying at 100. The hydrate
melts at 57 .
Anhydrous quinine, obtained as fine, silky needles by crystallisation
from dilute alcohol, melts at 174-6. It is tested for purity in the same
manner as quinine sulphate, being first converted into the latter.
The free base may be estimated volumetrically, using lacmoid as
indicator, i c.c. of A710 hydrochloric acid corresponds to 0-03242 g.
of quinine (anhydrous), or to 0-03783 g. of quinine + 3H20.^
Quinine Sulphate.
(C2oH,,02N2)2 . H.,SO, + 8H.3O. Molec. wt. 890-64.
The sulphate forms fine white needles with a bitter taste, and
is soluble in 800 parts of water at 15", in 100 parts of alcohol, in 40
parts of glycerol, and is practically insoluble in chloroform and in
ether; it dissolves in 25 parts of boiling water and in 6 parts of boiling
alcohol.
A cold, saturated solution of quinine sulphate shows no fluorescence,
but does so on the addition of sulphuric acid. A green coloration is
produced on mixing 10 c.c. of an aqueous solution with 2 c.c. of chlorine
water and addins; excess of ammonia.-
't>
Tests for Impiirities.
Inorgmiic and Organic Matter. — Not more than 0-5 mg. of ash should
remain on igniting i g. of quinine sulphate. The salt should colour but
very slightly on moistening with nitric or with sulphuric acid. On
dissolving i g. of quinine sulphate in 7 c.c. of a mixture of 2 vols, of
chloroform and i vol. of absolute alcohol at 40'- 50^, a clear solution
should result, showing no turbidity on cooling.
Acid Quinine Sulphate. — The cold, saturated, aqueous solution should
react either neutral or faintly alkaline with litmus paper.
Quinine Hydrochloride. — The cold, saturated, aqueous solution should
remain unchanged on the addition of silver nitrate solution.
Salicylic Acid. — Ferric chloride solution should not produce a violet
coloration with a cold, saturated, aqueous solution.
1 Cf. Z. angew. Chem., 1903, 16, 449 and 468.
2 For identifying reactions, cf. Merck's Reag.-Verz., 1908, p. 291, and Z. angev). Chtm., 1903,
16, 477-
QUININE SULPHATE 379
Foreign allied Alkaloids. — A test of a general character for the
detection of other cirxhona alkaloids in quinine, known as the
"ammonia test," has been adopted by most of the pharmacopoeias,
other than the British. This test is based on a method originally
proposed by Kerner,^ and is carried out as follows : — 20 c.c. of water are
poured on to 2 g. of quinine sulphate completely effloresced at 40°-50°,
the mixture frequently shaken, and heated for half an hour in a water-
bath at 6o°-65°. It is then cooled to 15° and allowed to stand at this
temperature, with frequent shaking, for two hours, when it is poured on
to a dry piece of linen ; as much liquid as possible is squeezed out of
the solid matter, and the liquid so obtained filtered. Ammonia (at 15°
and of sp. gr. 0-96) is then gradually added to 5 c.c. of the filtrate at 15°
until the precipitate at first produced redissolves. The volume of
ammonia that should be required for this purpose varies according
to the different foreign pharmacopoeias ; in Germany, for example, it
is fixed at 4-0 c.c. F. Tutin,^ who has conducted a series of careful
tests on this reaction, found that the minimum amount of 10 per cent,
ammonia that will yield a clear solution at 15° with 5 c.c. of a solution
of pure quinine sulphate, saturated at 15°, is 4-4 c.c. ; he therefore con-
cludes that it is impossible to meet the requirements of the German
Pharmacopoeia, and regards a minimum of 6 c.c. as reasonable.
This test is also misleading, because any basicity of the salt will have
the same effect as impurities, and, further, the presence of small quantities
of inorganic salts influences the result. Tutin accordingly regards the
test as of value only in the case of normal quinine sulphate ; specific
tests for cinchonidine and cinchonine are, in his opinion, preferable to
the "ammonia test."
Cinchonidine and CincJionitie The following test, which depends
on the fact that both cinchonidine and cinchonine are less soluble
than quinine in ether, is prescribed by the British Pharmacopoeia : —
4 g. of quinine sulphate are dissolved in 120 c.c. of boiling water,
and the solution allowed to cool down with frequent stirring. The
separated quinine sulphate is then filtered off, the filtrate evaporated
down to 10 C.C., poured into a small, stoppered flask and shaken, when
cold, with 10 c.c. of ether and 5 c.c. of ammonia (sp. gr. 0-959). After
standing for twenty-four hours in a cool place, the separated crystals
of cinchonidine and of cinchonine together with some quinine are
collected on a weighed filter paper, washed with a little ether, and
dried at 100°. Their weight should not exceed o-i2 g. F. Tutin ^
states that the test is more delicate if ether of sp. gr. 0-720-0-722
(Aether purificatus) be used for the test instead of ether of sp. gr.
0735-'
' Arch. Pharm., i88l, l6, l86. 2 Pharm. J., 1909, 83, 600. ^ Ibid.
* Cf. B. H. Paul, Chem. and Drug., 1904, 65, 428, and D. Howard, ibid., 1904, 65, 475.
380 ORGANIC PREPARATIONS
The following alternative test can also be emplo}-ed : — o-y g. of
quinine sulphate is treated in a large test tube with 20 drops of dilute
hydrochloric acid and 7 c.c. of water, then 7 c.c. of crystallisable thio-
phene-free benzene added, and the mixture heated in a water-bath to
60° -70°. After adding 3 c.c. of ammonia, the mixture is well shaken,
poured into a small separating funnel, and the aqueous layer run off
after it has completely separated. The benzene solution is allowed to
stand for about half an hour to allow the quinine to crystallise out,
when it is filtered through a dry filter paper and the filtrate allowed to
stand for a further length of time for further crystallisation to take
place. If the quinine sulphate under examination contains i per cent,
of cinchonidine it is possible in three to four hours to recognise feathery
groups of small needles along with the quinine (rhombic crystals) which
has crystallised out ; it is advisable to use a lens to distinguish the two
forms of crystals. If more than i per cent, of cinchonidine be present,
the separation of the needles is more rapid and abundant (with 5 per
cent, in about half an hour), whilst with less than i per cent, the separa-
tion requires several days with slow evaporation of the solution. To
avoid error in conclusions, the crystals must be observed and recognised
in the liquid, since crystals are formed in the upper parts of the test
tube owing to the evaporation of the benzene.^
Quinidine. — The following test is that prescribed by the British
Pharmacopoeia : — i g. of quinine sulphate is dissolved in 30 c.c. of boiling
water, allowed to cool, and filtered. Potassium iodide solution is added
to the filtrate, and to avoid the separation of amorphous hydriodides a
little 90 per cent, alcohol is also added. Either no crystalline separa-
tion of quinidine hydriodide, or only a very small separation, should
take place. In the latter case the cr}'stals are collected on a small
filter paper, washed with a little water, dried, and weighed. The weight
corresponds approximately to the amount of quinidine sulphate in i g.
of quinine sulphate.
Water. — According to the British Pharmacopoeia, 2-5 g. of quinine
sulphate on drying at 100" should lose 0-38 g. of water. Details for this
estimation are given below under quinine hydrochloride.
Quinine Hydrochloride.
C20H24O2N2 . HCl-h2HoO. Molec. wt. 39671.
Next to the sulphate this is the most important and most used salt
of quinine. It crystallises in white needles frequently united together
in tufts, and dissolves in 34 parts of water at 15" and in 3 parts of
alcohol. Its solutions are not fluorescent.
* Wood and Barret, C/iem, News, 1883, 48, 3.
QUININE HYDROCHLORIDE 381
Tests for Impurities.
Inorganic Matter. — This test is the same as in the case of the
sulphate.
Acid Qiiinine Hydrochloride. — The same test as in the case of the
sulphate. (The solution of the commercial product generally reacts
faintly alkaline with litmus paper.)
Qimii?ie S^dphate. — Barium chloride solution should only produce a
very faint turbidity with an aqueous solution of the hydrochloride
(1:50).
Barium Chloride. — Sulphuric acid should show no reaction with an
aqueous solution (i : 50).
Water. — Quinine hydrochloride, on drying at 100°, should not lose
more than 9-1 per cent, in weight. The content of water of crystal-
lisation in quinine hydrochloride may be more quickly arrived at
volumetrically in the following manner: — To 100 c.c. of absolute
alcohol and a few drops of a i per cent, aqueous solution of Poirrier's
blue in a 150 c.c. glass-stoppered flask, N\i^ potassium hydroxide is
added, drop by drop, until the blue colour of the solution changes to
red, and until on shaking in the closed flask there is no return to the
blue colour, i g. of quinine hydrochloride is then added, which causes a
return of the blue colour. On adding 12 -6 c.c. of iV/5 potassium
hydroxide, the solution should not change to red if the preparation does
not contain more than 9 per cent, of water. If necessary, the titration
is continued until a red coloration is produced, in order to determine
how much the salt under examination has effloresced. After each
addition of potassium hydroxide the flask must be closed, otherwise
errors may arise through the action of the carbon dioxide in the air.
Poirrier's blue is a very sensitive indicator to acids, which makes it
possible to estimate the mineral acid combined with quinine by titration
with alkali in the same way as if it were a free acid.^ \
If I g. of quinine sulphate be used under the above conditions, a
turbid liquid is produced in which, however, the changes of colour may
be equally well recognised. When using a sulphate containing the
correct amount of water, the change of colour should not be produced
with less than 11 -2 c.c. of Ay 5 potassium hydroxide.
Foreign allied Alkaloids. — 2 g. of quinine hydrochloride are dissolved
in a porcelain dish in 20 c.c. of water at 60°, i g. of powdered non-
effloresced sodium sulphate added, and the mixture well ground up
together with a pestle. When cold, the dish is placed in water at 15°
and allowed to stand at this temperature for half an hour, when the
mixture is filtered through a dry 7 cm. filter paper, and 5 c.c. of the
filtrate tested by one of the methods given for the sulphate.
' Cf. Z. angew.-Chem., IQOSi 16,469.
382 ORGANIC PREPARATIONS
Other quinine salts are tested in a similar manner to the sulphate
or hydrochloride, and must be treated according to their acid or neutral
character, and the acid with which they are combined ; in case of
necessity they may be converted into the sulphate or hydrochloride.
Resorcinol.
OH(i)
QH/ . Molec. wt. 110-05.
^OH(3)
Resorcinol comes into commerce in either a crystallised or sublimed
form. It crystallises in colourless plates or prisms possessing a faint,
characteristic smell. It melts at iio'"-iii°, and boils at 276. It
dissolves in i part of water, 075 parts of alcohol (90 per cent.), readily
in ether and glycerol, and sparingly in benzene, chloroform, petroleum
spirit, and carbon bisulphide. The aqueous solution of resorcinol reacts
acid to litmus paper. On warming o-i g. of resorcinol carefully with
0-2 g. of tartaric acid and 20 drops of sulphuric acid, a deep carmine-red
solution results. The aqueous solution is coloured violet by ferric
chloride, and is precipitated by basic lead acetate, but not by the normal
lead acetate,^
Tests for Impurities.
Inorganic Matter. — No appreciable residue should remain on heating
i-o g. of resorcinol.
Free Acids. — Since resorcinol reacts acid, testing with litmus paper
as a test for free acids, such as salicylic acid, which was formerly usual,
is useless. Larger quantities of acid are, therefore, best detected
by titration with A71 alkali. If i g, of resorcinol be dissolved in 10 c.c.
of alcohol (about 85 per cent, by weight), and a few drops of lacmoid
solution added, a red-coloured solution is obtained, which should be
turned a violet-blue on the addition of i drop of A^/io potassium
hydroxide solution.
Di-Resorcinol. — This impurity is only found in sublimed resorcinol.
I g. of resorcinol should dissolve in 20 c.c. of water, giving a perfectly
clear solution.
Phenol. — It should not be possible to detect a smell of phenol on
warming the above aqueous solution.
Quantitative Estimation.
This is carried out in a similar manner to Koppeschaar's - method of
estimating phenol. The aqueous solution of resorcinol (1-2 per cent.)
^ For colour reactions, cf. Merck's Reag.-Verz., 1908, p. 299.
- C/. Vol. II., Part II., p. 823.
SACCHARIN 383
is treated with excess of standardised bromine water, or, better, with an
acidified solution of potassium bromide and bromate, the excess of
bromine being determined by titration with Nji sodium thiosulphate
after the addition of potassium iodide. Tribromoresorcinol is formed
in the reaction with bromine, which is difficultly soluble in water.^
Saccharin.
^&^/ ^NH (I :2). Molec. wt. 183-12.
\so/
Pure saccharin (ortho-benzoyl sulphone-imide) comes into commerce
as a white, odourless, crystalline powder. It is a strong acid which
decomposes acetates and forms well-defined salts. Saccharin melts
at 224°. It disolves in 400 parts of water, in 30 of alcohol, in 1900 of
benzene, and in 120 of ether, and is also readily soluble in ammonia
and in the hydroxides and carbonates of the alkalis. It crystallises
in small, rhombic leaves from water, in thick prisms from alcohol or
acetic acid, in monoclinic crystals from acetone, and in small, hexagonal
plates from ether. It sublihies in three-sided plates.
The term "gluside" is adopted in the British Pharmacopoeia for
saccharin. The sodium salt is known as " crystallose " ; it is readily
soluble in water, but only sparingly so in alcohol.
On evaporating saccharin down to dryness on the water-bath with
nitric acid and then adding, whilst hot, a few drops of water or of
50 per cent, alcohol and a small piece of potassium hydroxide, blue and
red streaks of colour are formed on rocking the dish.
Tests for Imptirities.
Inorganic Matter, — No appreciable residue should remain on
ignition. Pure saccharin gives but a very small quantity of ash ;
Langbein found the following percentages of ash in the following
brands : — Heyden 0-098 per cent, Fahlberg o-o6 per cent., Bayerl 0-063
per cent., and Monnet 0-04 per cent.^
Foreign Organic Matter. — Saccharin should not char on heating, and
should not give more than a wine-yellow coloration when dissolved in
twenty times its weight of sulphuric acid.
Chlorobenzoic Acid. — 0-5 g. of saccharin is moistened with water,
mixed with i g. of chloride-free calcium carbonate, and the mixture
dried and ignited. The ignited residue dissolved in water and nitric
acid and made up to 20 c.c. should give no turbidity of silver chloride
on adding silver nitrate solution.
' C/: C. M. Pence,/. Ind. Eng. Chem., 1911, 3, 820 ; /. Soc. C/iem. Ind., 1911, 30, 1369.
2 Z. angew. CJiem., 1896, 9, 494.
384 ORGANIC PREPARATIONS
Para-sulpJiauiido Benzoic Acid. — i g. of saccharin is shaken for a few
minutes with 70-80 g. of ether at 15, the undissolved residue collected
on a small filter paper and dried at lOo". The residue should not melt
above 224". The para-acid melts at 280 -283 , and raises the melting
point of the above residue, since it is almost insoluble in ether, and
becomes concentrated in the residue, practically all the saccharin being
dissolved.
Benzoic Acid afid Salicylic Acid. — i g. of saccharin is boiled with
20 c.c. of water, allowed to cool, and filtered. The filtrate should neither
be rendered turbid nor coloured violet by ferric chloride.
ATannitol. — 0-5 g. of saccharin is dissolved in 10 c.c. of water, and
5 c.c. of sodium carbonate solution (i : 5) and 10 c.c. of copper sulphate
solution (i : 10) added, the mixture shaken, and filtered after a few
minutes ; 5 c.c. of sodium hydroxide solution are then added to the
filtrate, whether the latter has become turbid subsequent to filtering or
not, and the solution heated to boiling. A colourless solution with a
brown precipitate should result. A blue solution points to the presence
of mannitol.
Quantitative Estimation.
Since the saccharin that comes into commerce contains varying
quantities of ortho-benzoyl sulphone-imide, it is best to estimate the
latter quantitatively. Commercially saccharin is always judged by
sweetness, a method of doubtful value, since the sensitiveness of indi-
viduals to the taste of sweetness does or may vary. Since the
sweetness depends on the content of sulphone-imide, and is influenced
by the content of the para-acid and other constituents which are not
sweet but on the other hand of unpleasant taste, a quantitative estima-
tion is really necessary in order to ascertain the purity of the
preparation, if the tests given above are insufficient.
The following procedure is given by R. Hefclmann : ^ — 10 g. of
saccharin are heated in a boiling water-bath for from four to five hours
with 100 c.c. of 73 per cent, sulphuric acid, with frequent shaking.
Saccharin is thus completely converted into the ammonium salt of
sulpho-benzoic acid, whilst the para-acid remains practically unchanged.
The decomposition takes place in two stages as follows : —
/CO. .COOH
CgH/ >NH + H.,0 - C,H /
^SO./ " \SO.,.NH.,
/COOH .COOH
CoH / +H,0 = C,H /
\SO2.NH., \SO,ONH,
' Pharm. Zenlralh.y 35, 105 ; cf. also Grtinhut, Z. anaL Chan., 1897, 36, 534.
SACCHARIN. SALICYLIC ACID 385
The mixture is then diluted with an equal volume of water, allowed
to cool, a small crystal of pure para-acid added, and then allowed to
stand for twelve hours. The para-acid thus separates out quantitatively
(only after standing for from two to three days if present in very small
quantities) ; it is collected in a Gooch crucible with a double perforated
bottom and asbestos filter, washed with small quantities of cold water
until the washings show no reaction for sulphuric acid, and then dried
at ioo° till constant. The weight of the para-acid obtained is somewhat
less than it should be, since it is very slightly soluble in water. The
error is so small, however, that it may be practically ignored. The
para-acid so obtained should melt between 270°-28o°.
The filtrate from the para-acid is made up to 500 c.c. in a graduated
flask, and 50 c.c. of the solution saturated with ignited magnesia and
distilled, the ammonia being collected in 7V/2 sulphuric acid. The
quantity of acid neutralised by the ammonia is found by titrating back
with NJ2 potassium hydroxide, and from it the nitrogen content in the
saccharin may be calculated, i per cent, of nitrogen corresponds to
13-04 per cent, of saccharin. The total nitrogen is determined by
boiling I g. of saccharin with 25 c.c. of concentrated sulphuric acid and
0-5 g. of mercury in a Kjeldahl flask for two hours, diluting the mixture
in a litre flask with 250 c.c. of water, and after adding excess of nitrogen-
free sodium or potassium hydroxide solution and about 3 g. of pure
zinc dust, the ammonia is distilled off by boiling for one hour and
collected in 20 c.c. of Nji sulphuric acid. The content of para-acid
may be arrived at from the difference between the two nitrogen
determinations.^
L. Griinhut^has called attention to the fact that many brands of
saccharin contain small quantities of ammonium compounds (he found
up to 0-046 per cent, of nitrogen as ammonia), and that allowance must
be made in such cases by quantitatively estimating the ammonium
compounds present.
H. Langbein ^ has shown that the content of the para-acid in
saccharin may be readily estimated from the heat of combustion, and
states that the results given by this method are very good.
Salicylic Acid.
OH(i)
CgH^/ . Molec. wt. 138-05.
\C00H(2)
Salicylic acid comes into commerce either as white, odourless needles
or as a powder. It melts at 1 56^-1 57^ dissolves in about 445 parts of
1 Hefelmann, Pharm. Zeit., 41, 379. '^ Loc. cil.
^ Z. angew. C/iem., 1 896, 9, 494.
Ill 2 B
386 ORGANIC PREPARATIONS
water at 15', in 15 parts of boiling water, in 2 parts of alcohol or ether,
and readily in acetone, chloroform, and carbon bisulphide. It is also
soluble in various salt solutions, such as ammonium acetate, ammonium
citrate, sodium phosphate, borax, etc., in the hydroxides and carbonates
of the alkalis, and in ammonium hydroxide, as well as in glycerol, and
in fatt}' and essential oils.
The aqueous solution of salicylic acid gives a permanent violet
coloration with ferric chloride and a green coloration with copper
sulphate. Free mineral acids or alkalis prevent or influence these
colour reactions.^
Tests for Impurities.
Inorganic Matter. — On heating, salicylic acid should volatilise, leaving
but a very small quantity of residue; the residue after ignition should
not amount to more than o-i per cent.
Hydrochloric Acid. — The alcoholic solution (i : lo) should show no
reaction on adding nitric acid and silver nitrate solution.
Foreign Orga?tic Alatter. — Salicylic acid should not char on heating.
I g. of salicylic acid should dissolve to a practically colourless solution
in 5 c.c. of sulphuric acid. On dissolving 0-5 g. in absolute alcohol
and evaporating off the latter, a perfectly colourless, crystalline mass
should remain. The crystals should show no yellow coloration at their
points.
Phenol and Salol. — In the absence of salol, 5 g. of salicylic acid
should dissolve to a perfectly colourless solution in ICXD c.c. of sodium
carbonate solution (i : 5). This solution is shaken up with 30 c.c. of
ether, the ether layer syphoned off, again shaken up with 30 c.c. of
water, and the ether then allowed to evaporate off on a clock-glass
without application of heat. Any residue should not smell of phenol.
It is dissolved in a few drops of alcohol and put on one side to evaporate
slowly, when salol will crystallise out and may be recognised by its
melting point, 42^-43^ In order to detect traces of phenol, 0-25 g. of
salicylic acid are rubbed up with 5 c.c. of water, 2 drops of a 2 per cent,
alcoholic solution of furfural added, and then 2-3 c.c. of concentrated
sulphuric acid slowly run in down the side of the vessel. Minute
quantities of phenol cause first a yellow, then a deep blue to violet-blue
coloration to be produced at the contact surface of the liquids.^
The methods for detecting the following possible impurities in
' For identifying reactions, cf. Merck's Reag.-Verz., 1908, p. 300 ; J. M'Crea, Analyst, igir,
36, 540; H. C. Sherman and A. Gross, y. /tut. Bng. CItem., IQUi 3i 492 ; yi Soc. Cliem. Jnd.,
1911.30,979; E. Barral, Bull. Soc. Cliim., 1912, II, 417 ;y. Soc. Chem. Ind., 1912, 31, 457.
For reactions to distinguish salicylic acid from phenol and resorcinol, cf. Z. anal. Chem., 1889,
28, 712, andy Soc. Chem. hid., 1908, 27, I131.
- Carletti, Pharm. Zeil., 1907, 52, 1013 ; 190S, 53, 192.
SALICYLIC ACID. SALOL 387
salicylic acid are lengthy and complicated ; reference is given to the
original publications : —
Cresotinic acids, p-hydroxy-benzoic acid, and Jiydroxy-phthalic acid}
Homologues of salicylic acid'^ and impurities in salicylic acid used Jor
physiological purposes?
Quantitative Estimation.
I g. of salicylic acid, dried at 50^-60', is dissolved in 90 per cent,
alcohol, and made up to 100 c.c. 10 c.c. of this solution is titrated to a
pink colour with iV/io potassium hydroxide, using phenolphthalein as
indicator, i c.c. of A710 potassium hydroxide corresponds to 0-01380 g.
of salicylic acid, or i g. of salicylic acid requires 72-4 c.c. of iV^/io
potassium hydroxide. If small differences are found in the titrations
and the qualitative examination has shown inorganic matter, phenol,
and salol to be absent, this points to a content of homologous acid or
of cresotinic acid, in which case they should be specially tested for.
According to J. Messinger and G. Vortmann,* salicylic acid may also
be estimated iodometrically even in presence of benzoic acid. This
method has also been studied by J. M. VVilkie.^
Salol.
OH(i)
CgH / . Molec. wt. 214-08.
\COOCeH,(2)
Salol, the phenyl ester of salicylic acid, crystallises in colourless,
rhombic plates, possessing a faint aromatic odour. It melts at 42°-43°,
dissolves in 10 parts of alcohol and 0-3 parts of ether, but is practically
insoluble in water.
The alcoholic solution of salol gives a violet coloration with ferric
chloride solution. If 0-5 g. of salol be dissolved in hot sodium hydroxide
solution and an excess of hydrochloric acid added, salicylic acid separates
out and the solution smells of phenol.
Tests for Impurities.
Free Acid. — On sprinkling powdered salol on blue litmus paper
moistened with water, the paper should not be reddened.
Salicylic Acid. — A solution of o-i g. of salol in 5 c.c. of ether is
poured over some 10 per cent, ferrous sulphate solution in a test tube.
If traces of salicylic acid be present, a violet ring is produced in a short
time at the contact surface of the two liquids.
Foreign Organic and Inorganic Matter, such as salicylic acid,
1 Z. anaK Chem., 1890, 29, 476. ^ Pharm. Zentra!>'i., 29, 635 ^ Ibid., 32, 92.
* Ber., 1890, 23, 2755 ; /. Soc. CAem. hid., 1890, 9, 1070.
^ J. Soc. Chem, hid., 1911, 30, 398.
388 ORGANIC PREPARATIONS
sodium phenate, sodium salicylate, sodium chloride, and sodium sulphate
or phosphate. Not more than 0-5 mg. of residue should remain on
igniting 0-5 g. of salol.
On shaking 2 g. of salol with 100 c.c. of water and filtering, the
filtrate should show no reaction with either dilute ferric chloride solution,
silver nitrate solution, or barium chloride solution.
Santonine.
CjjHjgOg. Molec. wt. 246-14.
Santonine crystallises in small, colourless, odourless, glistening,
rhombic plates, possessing a bitter taste and melting at 170°. It
dissolves in about 5000 parts of water at 15 , in 250 parts of boiling
water, in 44 parts of alcohol at 15", in 3 parts of boiling alcohol, in 4
parts of chloroform, in 125 parts of ether, in concentrated acids, in fatty
and essential oils, in the hydroxides and carbonates of the alkalis, and is
practically insoluble in petroleum spirit.
No coloration should be produced on shaking up o-i g. of santonine
with a cold mixture of 10 c.c. of sulphuric acid and 10 c.c, of water ; on
heating this mixture nearly to boiling and then adding several drops of
ferric chloride, a violet coloration is produced.^
Tests for Impurities.
Inorgatiic Matter. — Not more than 0-5 mg. of residue should remain
on igniting i g. of santonine.
Orga7iic Impurities. — Santonine should not be immediately coloured
on moistening with either sulphuric acid or with nitric acid.
Free Acids. — A hot solution of i g. of santonine in 10 c.c. of alcohol
should react neutral.
Citric acid, which is sometimes found in santonine as an adulterant,
is tested for as follows : — If by the foregoing test the presence of an
acid is indicated, then 0-2 g. of the sample are placed on a watch-glass
in a drying oven for a quarter of an hour, at a constant temperature
of 115'. If the santonine is adulterated with citric acid a completely
molten, yellow-coloured mass will result.-
Strychnine.
C21H22O2N2. Molec. wt. 334-20.
Strychnine comes on to the market as a white, crystalline powder or
in colourless, rhombic crystals which melt at 266'. It dissolves in 6600
parts of cold, and in 2500 parts of boiling water, in 160 parts of cold,
^ For identifying reactions, cf. Merck's Reag.-Verz., 1908, p. 3C0.
- Boll, cliim.fartn.y I908, p. 7.
STRYCHNINE 389
and in 12 parts of boiling 90 per cent, alcohol, in 6 parts of chloroform,
and sparingly in ether, benzene, amyl alcohol, and carbon bisulphide ; it
is practically insoluble in absolute ether and in absolute alcohol. It
chars on burning.^
The tests are the same as for strychnine nitrate.
Stiychnine Nitrate.
C21H00O.2N2. HNO3. Molec. vvt. 397-21.
Strychnine nitrate crystallises in colourless and odourless needles
possessing a very bitter taste. It dissolves in 90 parts of water, in 70
parts of 90 per cent alcohol, and is practically insoluble in ether,
chloroform, and carbon bisulphide.
On adding potassium bichromate solution to an aqueous solution of
strychnine nitrate, reddish -yellow crystals separate out, which, when
added to sulphuric acid, become transitorily coloured a blue-violet.
Tests for Impurities.
Inorganic Matter. — No residue should remain on igniting i g. of
strychnine nitrate.
Chloride and Sulphate. — The aqueous solution (i : 100) should show
no reaction with either silver nitrate or with barium chloride solution.
Brucine. — On being rubbed up with nitric acid, strychnine nitrate
should be coloured yellow but not red.
Organic hnpnrities. — Strychnine nitrate should dissolve to a colour-
less solution in sulphuric acid, and without charring.
Quantitative Estimation.
Strychnine nitrate may be estimated volumetrically under the con-
ditions given for quinine hydrochloride (p. 381). i c.c. of iV/5 potassium
hydroxide corresponds to 007944 g- of strychnine nitrate.
The free base may be estimated volumetrically in the same way
as morphine (p. 365), or also in alcoholic solution, using lacmoid
as indicator. 1 c.c. of A^io hydrochloric acid is = 0-03342 g. of
strychnine.
Sulphanilic Acid.
NH^CO
CgH/ +2H2O. Molec. wt. 209-17.
\S020H(4)
Sulphanilic acid crystallises in colourless, needle-like crystals, pos-
sessing no definite melting point, but which char on heating to 280''-
^ For identifying reactions, cf. Merck's Reag.-Verz., 1 908, p. 301.
390 ORGANIC PREPARATIONS
300'. It is only; sparingly soluble in cold water (in about 160 parts),
but more readily in hot water ; it is insoluble in alcohol, ether, and
benzene.
If a few small crystals of sulphanilic acid be dissolved in 50 c.c. of
water, and an equal quantity of a-naphthylamine sulphate added, the
addition of a drop. of an aqueous solution of sodium nitrate produces a
cherry-red coloration which quickly changes to yellowish - red with
separation of a brownish-red precipitate.
Tests for Impurities.
Inorganic Matter. — No appreciable residue should remain on igniting
i-o g. of sulphanilic acid.
Sulphjiric Acid (^Aniline Sulphate). — A solution of i g. of sulphanilic
acid in 25 c.c. of boiling water should show no change on adding a few
drops of barium chloride solution.
Hydrochloric Acid {^Aniline Hydrochloride). — On shaking up i g. of
sulphanilic acid with 20 c.c. of water and filtering, the filtrate should, at
most, only give a faint opalescence on adding a few drops of nitric acid
and silver nitrate solution.
Quantitative Estimation.
I g. of sulphanilic acid is dissolved in 10 c.c. of N\\ sodium
hydroxide and some water, and titrated with N\i hydrochloric acid,
using phenolphthalein as indicator, i c.c. of the A71 sodium hydroxide
used in neutralisation corresponds to 0-2092 g. of sulphanilic acid.
The titration of sulphanilic acid with sodium nitrite is more reliable ;
this, together with other methods of estimation, is described in the
section on "Organic Dyes," Vol. II., Part II., pp. 884-5. It is to be
borne in mind that sulphanilic acid efifloresces readily, and that, in
consequence, high results may be obtained.
Sulphonal.
"^C^ " " ". Molec. wt. 228-27.
CH3 SO2C2H5
Sulphonal crystallises in colourless, tasteless, and odourless prisms
which melt at 125'-! 26' and boil at about 300° with slight decomposi-
tion. It dissolves in 15 parts of boiling water and in 500 parts of
water at 15', in 2 parts of boiling alcohol and in 65 parts at 15', and
in about 135 parts of ether. The solutions of sulphonal react neutral.
On heating sulphonal with powdered charcoal, a smell of mercaptan is
evolved.
SULPHONAL. TANNIN 391
Tests for Impurities.
Inorganic Matter. — Not more than 0-5 mg. of residue should remain
on igniting 0-5 g. of sulphonal.
Fj'ce Acids. — Powdered sulphonal placed on to blue litmus paper
moistened with water should not redden the paper.
Sulphuric Acid and HydrocJiloric Acid. — i g. of sulphonal is dissolved
in 50 c.c. of boiling water, the solution allowed to cool and then filtered.
Barium chloride solution is added to one-half of the filtrate, and silver
nitrate solution to the other half. In neither case should a turbidity
or change be produced.
Foreign Organic Matter. — i g. of sulphonal should not become
coloured on pouring 10 c.c. of sulphuric acid over it.
Mercaptol {{QW^.fi{^Q..^^)^} and Oxidisable Matter. — No garlic-like
odour should be produced on boiling i g. of sulphonal with 50 c.c. of
water. After cooling and filtering this solution, 10 c.c. are taken and
one drop of potassium permanganate solution (i : 1000) added. The
colour of the permanganate should not be immediately discharged.
Note. — To detect sulphonal in trional and tetronal, use is made of
the differences in their' solubility in ether; 10 c.c. of ether at 15"
dissolve about 0-07 g. of sulphonal, 0-5 g. of trional, and i g. of tetronal.^
The undissolved residue is detected as sulphonal by its reactions and
melting point.
Tannin (Tannic Acid).
C14H10O9 + H.O. Molec. wt. 358-11.
Tannin comes into commerce as a yellow amorphous powder, or as
"crystalline tannin" or "needle tannin." It should possess only a faint
smell and should dissolve to form perfectly clear solutions in water and
in alcohol (about 85 per cent, by weight). It is soluble in i part of
water, 2 parts of alcohol, 8 parts of gl)cerol, and in ethyl acetate ; it
dissolves sparingly in ether (according to its content of alcohol), and is
practically insoluble in chloroform, petroleum spirit, benzene, and
carbon bisulphide. Alcoholic and aqueous solutions of tannin are
dextrorotatory.
The aqueous solution of tannic acid gives a blue-black precipitate
with ferric chloride, the precipitate dissolving on addition of sulphuric
acid. Dilute solutions only give a blue-black coloration. Tannin pre-
cipitates solutions of tartar emetic, alkaloids, albumin, and glue.-
Reactions distinguishing gallic from tannic acid are described under
gallic acid (p. 353).
1 E. GabuttiiT". Pharm. Ckim., 1907, 25. 183 ; /. Soc. Chem. hid., 1907, 26, 636.
"^ For identifying reactions of tannin, cf. Merck's Reag.-Verz., 1908, p. 294.
392 ORGANIC PREPARATIONS
Tests for Impvirities.
Inorgonic Matter {Zinc). — Not more than 5 mg. of residue should
remain on igniting 4 g. of tannin. The residue, when dissolved in 2 c.c.
of acetic acid and diluted with 8 c.c. of water, should give not more
than a faint opalescent turbidity on adding sulphuretted hydrogen
water.
Sugar and Dextrin. — On mixing 10 c.c. of a tannin solution (1:5)
with 10 c.c. of alcohol (about 85 per cent, by weight) the solution should
remain clear for half an hour; no turbidity should be produced on the
further addition of 5 c.c. of ether.
Gallic Acid. — Even the purest tannin contains traces of gallic acid,
which may be recognised by the red coloration produced on treating a
solution of tannin with potassium cyanide solution. Larger quantities
of gallic acid may be estimated by the method given under gallic acid
(P- 354)-
Water. — On drying i g. of tannin at 100 till constant, the loss of
weight should not exceed 12 per cent.
Quantitative Estimation.
The quantitative estimation of tannin may be carried out by the
methods described in the section on " Vegetable Tanning Materials,"
this Vol., pp. 452 et seq.
Theobromine.
C3H,(CH3)o0.3N,. Molec. wt. i8o-io.
Theobromine is a white, crystalline powder without smell, and
possessing a bitter taste. At about 290° most of it sublimes undecom-
posed, without previously melting. It dissolves in about 1600 parts of
cold, and in 150 parts of boiling water, in about 4000 parts of cold, and
400 parts of boiling absolute alcohol, and in 100 parts of boiling
chloroform. The aqueous solution reacts neutral. Theobromine
dissolves both in acids and in dilute alkalis.
On evaporating a solution of theobromine on the water-bath with
chlorine water, a reddish -yellow residue is obtained which becomes
coloured purple-red on adding a drop of ammonia. C. Gerard ^ gives
the following reaction for distinguishing theobromine from caffeine : —
I c.c. of a 10 per cent, silver nitrate solution is added to a mixture of
0-05 g. of theobromine, 3 c.c. of water, and 6 c.c. of sodium hydroxide
solution, and after heating to 60' the resulting clear solution is allowed
to cool ; when cold, the mixture solidifies to a transparent jelly.
Caffeine does not give this reaction.
ly. Pharm, Chim., 1906, 23, 476 ; /. C/iem. Soc. Abstr., 1906, 90, 507.
THEOBROMINE 393
Tests for Impurities.
Theobromine should dissolve to form colourless solutions in sulphuric
acid, in nitric acid, and in ammonia. The cold, saturated, aqueous
solution should not be precipitated by iodine solution.
Caffeine. — If o-i g. of theobromine be repeatedly shaken during one
hour with lo c.c. of chloroform and then filtered, 3 c.c. of the filtrate
should not leave more than o-ooi g. of residue when evaporated on
the water-bath.
Water and Inorganic Impurities. — i g. of theobromine should not
lose appreciably in weight on drying at 100'', and should volatilise on
heating without leaving an appreciable residue (0-5 mg.).
In medicine, in place of pure theobromine, the double salts
theobromine-sodium acetate, theobromine-sodium benzoate, and
theobromine-sodium salicylate are mostly used. These preparations,
of which the last-named is the most important, are very soluble in
water, but the solutions are rendered turbid by the action of the carbon
dioxide in the air, since acids cause a separation of free theobromine.
Theobromine-Sodium Salicylate.
This is a double salt of theobromine and sodium salicylate with
sodium hydroxide, having the composition : —
C7H7Na02N4 . HP . C6H,(OH)(COONa)
and containing approximately 45 per cent, of theobromine. It forms
a white, odourless powder, possessing a sweet, and at the same time
somewhat alkaline taste, and dissolves in its own weight of water. The
aqueous solution is alkaline to litmus paper, and gives a violet coloration
with ferric chloride solution. Hydrochloric acid precipitates salicylic
acid from the aqueous solution, and also after some time theobromine,
as a white precipitate which is completely redissolved by sodium
hydroxide, but not by ammonia.
Tests for Impurities.
Sodium Carbonate and Decomposition Products. — Theobromine-sodium
salicylate should dissolve in sulphuric acid without effervescence, and
to a colourless solution.
Caffeine. — On shaking up a solution of i g. of theobromine-sodium
salicylate in 10 c.c. of sodium hydroxide solution with 10 c.c. of
chloroform, not more than 0-005 g- o^ residue should remain on evapora-
tion of the chloroform extract.
Water. — The preparation should not lose more than 10 per cent.
in weight on drying for one hour at ioo\
394 ORGANIC PREPARATIONS
Quantitative Estimation.
Free Sodium Hydroxide. — If i g. of the anhydrous salt or a
correspondingly larger quantity of the hydrated salt be dissolved in
lOO c.c. of previously boiled water, the solution, after the addition of
a few drops of phenolphthalein, should not require more than 2-9 c.c.
of iV/i acid for neutralisation.
Combined Sodium Hydroxide. — i g. of the salt, dissolved in 400 c.c.
of water, should not require more than 2-9 c.c. of iV/i acid for
neutralisation, using methyl orange as indicator.
Sodium Salicylate. — i g. of the anhydrous salt is dissolved in water,
acidified with 3 c.c. of dilute sulphuric acid, and the salicylic acid
completely extracted with ether. The residue obtained on evaporation
of the ethereal extract, when dissolved in alcohol and some water,
should require 26-5-to 27-5 c.c. of iV/io sodium hydroxide for neutralisa-
tion, using phenolphthalein as indicator. This volume of iV/iO sodium
hydroxide corresponds to 42-44 per cent, of sodium salicylate.^
Theobromine. — The following method, due to E. Anneler,- yields
results which are accurate to within o-i per cent. : — i g. of theobromine-
sodium salicylate is dissolved in about 10 c.c. of water in a small
separating funnel, the theobromine and salicylic acid precipitated by
adding 3 c.c. of hydrochloric acid (10 per cent.), and after adding a drop
of phenolphthalein solution and concentrated barium hydroxide solution
(till red), the solution is extracted three times successively with a 20
per cent, solution of phenol in chloroform. The chloroform and phenol
are then evaporated off on the water - bath, when a residue of pure
theobromine is left, which is weighed.
The method described by O. Frey,^ in which the theobromine is
precipitated from an acid solution by means of ammonia, )-ields only
comparative results, as the separation of the theobromine is incomplete.
Thymol.
/CH3(i)
CgHg— 0H(3) . Molec. wt. 1 50- 1 1.
^C3H,(4)
Thymol forms colourless, hexagonal crystals which have a th}'me-
like smell and an aromatic taste. It melts at 50-51'', and boils at 228'-
230 . It sinks in water, since in the solid state it has a sp. gr.
of 1-028^ but is lighter than water when melted. Thymol dissolves
readily in alcohol, ether, chloroform, carbon bisulphide, and petroleum
spirit, as well as in sodium hydroxide solution ; it is only sparingly
' Cf. O. Frey, Z. d. Oesterr. Apoth.-Ver.^ 1909. 47. 433 ; J- Soc. Chem. ImL, 1909, 28, 1166.
2 Pharm. Zeit., 1910, 55, 205. 3 /^^ f,/
THYMOL. VANILLIN 395
soluble in water (i : iioo). On dissolving a small crystal of thymol
in hot potassium hydroxide solution and adding a few drops of
chloroform, the mixture assumes a violet coloration on shaking. If i g.
of thymol be dissolved in 4 g. of sulphuric acid, and this solution after
being gently warmed for five minutes be poured into 50 c.c. of water,
and then lead carbonate added in excess and the mixture allowed to
stand for half an hour at about 40^ with frequent shaking, on filtering,
the filtrate gives a violet coloration on the addition of ferric chloride.
Thymol turns a rose-red colour on heating with sulphuric acid to about
60^ and is converted into thymol sulphonic acid. A bluish -green
coloration is produced by dissolving a small crystal of thymol in i c.c.
of glacial acetic acid and then adding 6 drops of sulphuric acid and i
drop of nitric acid.^
Tests for Impurities.
Inorganic Matter.— ^o appreciable residue should remain on igniting
I g. of thymol.
Free Adds. — Neither an aqueous nor alcoholic solution of thymol
should redden blue litmus paper.
PJmiol. — On adding bromine water to the aqueous solution (i : 1000),
only a milky turbidity should be produced, and no crystalline precipi-
tate. The same solution should not give a violet coloration with ferric
chloride.
Quantitative Estimation.
J. Messinger and G. Vortmann 2 give the following method, which is
both rapid and convenient: — 2-5 g. of thymol are dissolved in 25 c.c. of
sodium hydroxide solution (sp. gr. 1-17), and the solution made up with
water to 250 c.c. 25 c.c. of this solution are transferred to a 250 c.c.
measuring flask, and 100 c.c. oS. N\io iodine solution added, whereby a
brownish -red precipitate is produced. After acidifying with dilute
sulphuric acid the flask is filled up to the mark, the contents filtered,
and the excess of iodine titrated with N\\o sodium thiosulphate. From
the number of cubic centimetres of iodine solution used, the quantity
of iodine used for i g. of thymol is calculated, and this figure, multi-
plied by 29-561, gives the percentage content of thymol.
Vanillin.
XOH(i)
CgHg— OCH3(3). Molec. wt. 15206.
^0H(4)
Artificially prepared vanillin is similar in all its properties to that
1 For other identifying reactions, cf. Merck's Reag.-Verz., 1908, p. 301.
- Ber., 1890, 23, 2753 ; / Soc. Cfiem. Ind., 1890, Q, 1070 ; J. prakt. Chevu, 1900, 61, 237 ;
J. Soc. Chem. Ind., 1900, 19, 568.
396 ORGANIC PREPARATIONS
obtained from the vanilla bean. It comes into commerce as colourless
or slightly yellow needles which possess a vanilla-like smell. It melts,
when quite pure, at 83," and boils at 285^ Vanillin dissolves in 100
parts of water at 15' and in 20 parts of boiling water, and readily in
alcohol, ether, chloroform, and carbon bisulphide. The cold, saturated,
aqueous solution gives a violet coloration with ferric chloride. A
brownish coloration is produced on warming this mixture, and fine
needles (dehydrodivanillin) separate out. A deep red coloration is
produced on adding 10-15 c.c of concentrated hydrochloric acid (sp. gr.
1-19) to a solution of o-i g. of vanillin and 0-2 g. of pyrogallol in 5 c.c.
of alcohol.^
Tests for Impiirities.
Inorganic Matter. — Not more than 0-5 mg. of residue should remain
on igniting i g. of vanillin.
Foreign Organic Matter {Sttgar, Tarry Substances). — o-i g. of
vanillin should dissolve in 20 c.c. of sulphuric acid to a pale yellow
solution ; no browning or charring should take place.
Coumarin may be readily detected in vanillin by fusing with potas-
sium hydroxide, salicylic acid and acetic acid being produced, which
may be easily identified ; vanillin yields protocatechuic acid.
\V. Hess and A. Prescott- detect coumarin by passing dry ammonia
gas through an ethereal solution of vanillin, whereby the aldehyde-
ammonia compound of vanillin is separated. On shaking with
ammonium hydroxide, all the vanillin is extracted from the ethereal
solution, whilst coumarin remains dissolved in the ether and may be
recognised in the dried residue remaining after evaporating off the
ether, by its melting point {^^'j"').
Acetanilide and Benzoic Acid, which may be present in commercial
vanillin as adulterants, may be detected by their identifying reactions.
Quantitative Estimation.
I g. of vanillin is dissolved in 25 c.c. of alcohol and 25 c.c. of alcoholic
NI2 potassium hydroxide, and the excess of alkali titrated back with
NI2 hydrochloric acid, using phenolphthalein as indicator. The number
of cubic centimetres of potassium hydroxide used, multiplied by 0-07603,
gives the content of vanillin.
The colorimetric method due to F. Moerk^ only gives approxi-
mate values; it is based on the bluish -green coloration produced
' For other colour reactions, of. Merck's Reag.-Verz., 1908, p. 302.
■•^ Pharm. Rev., 1899, I?. 7 '. /• ^°'^- C/iem. Ind., 1899, 18, 397 ; /• '^rner. Chem. Soc, 1899, 21,
256 ; /. Soc. Chem. Ind., 1899, 18, 525.
^ Z. anal. Chem., 1893, 32, 242 ; /. Soc. Chem. Ind., 1892, II, 637.
VANILLIN 397
by ferrous sulphate in a solution of vanillin to which bromine has been
added.^
Literature.
Merck, 'E.— Chemical Reagents, their Purity and Tests. English translation by H.
Schenck, 1908.
Merck, E. — Priifung der chemischen Reagenzien auf Reinheit, 2nd edition, 191 2.
Merck, E. — Reagenzien-Verzeichniss, 2nd edition, 1908.
^ Cf. VV. S. Hubbard, / bid. Eng. C/iem., 1912, 4, 669 ; J. Soc. C/iem. Ind., 1912, 31, 949, and
O. Folin and W. Denis,/. Ind. Eng. C/iem., 1912, 4, 670 ; /. Soc. C/iem. Ind.^ 1912, 31, 949.
INDIA-RUBBER AND RUBBER GOODS.
By F. Frank, Ph.D., and E. Marckwald, Ph.D., Berlin. English translation
revised by W. A. Caspari, Ph.D., B.Sc.
^.— CRUDE AND VULCANISED RUBBER.
India-rubber, or rubber for short, is the name given to the solid
matter which exists in aqueous suspension in the latex of various
plants, from which it is separated by chemical or mechanical methods.
Rubber-yielding plants belong chiefly to the botanical families of
Euphorbiacccv, AscUpiadecE, and Apocynaceis ; their habitat is South and
Central America, Africa, the Malay Peninsula, and the islands of the
Malay Archipelago. Whereas the bulk of crude rubber still comes
from wild trees, a very large quantity is now produced from plantations.
A great variety of crude rubbers is known to commerce, differing not
only in origin and external appearances, but also in physical and
chemical characteristics. The substance which is common to all of
them, and which makes rubber what it is, is the caoutchouc hydrocarbon.
This substance was named pol\'prene by C. O. Weber, and the name,
though based on assumptions which were subsequently refuted, is still
in use. Its chemical constitution has been shown by C. Harries^
to be that of a dimethyl-rj'^/(?-octadiene, on evidence derived not only
from the degradation of rubber, but also from its synthesis from
isoprene, first observed at a much earlier date by Tilden.- Isoprene has
been prepared synthetically by Euler,"^ and its constitution is well
known. The empirical formula of the rubber hydrocarbon is (C^oHig^.
The physical differences in rubbers of various origin may in all prob-
ability be accounted for by variations in molecular structure, and in
the degree of polymerisation. Apart from this, crude rubbers also
differ widely in the amount and nature of the foreign matter associated
with them, which may either have been derived from the latex, or may
have been added in the preparation, either through ignorance or by
^ Ber., 1905, 38, 1 195. ^ C/iem. Navs, 1882, 46, I20.
3 Ber., 1898, 30, 1989.
898
CRUDE RUBBER 399
way of adulteration. Again, ingredients not of the nature of rubber
may have been produced by decomposition of the rubber itself whilst
lying by, or during shipment. Whenever, then, the word "rubber" is
used in the sequel, it will be understood that this term covers a series of
substances which are closely related chemically, but need by no means
be identical.
The Examination of Crude Rubber.
The identification and valuation of crude rubbers, the market prices
of which cover a wide range, is carried out by practical experts with the
aid of such external properties as colour, odour, taste, springiness, shape,
and so forth.^ These criteria, valuable as they are, do not rank as
analytical methods, and are accordingly outside the scope of this
Section.
Crude rubbers always contain certain associated substances in pro-
portions which vary not only for the different sorts but also for different
samples of the same sort. These are, first and foremost, moisture,
together with organic and inorganic impurities, such as bark, leaves,
sand, pebbles, clay, soluble matter, proteids, etc. The cleansing process,
which is the first stage in rubber manufacture, eliminates the greater
part of these impurities, which are summed up under the heading of
" washing loss." To determine washing loss on a few grams of rubber
taken from bulk by the laboratory methods of desiccation, incineration,
etc., would be of no value, because the impurities are very irregularly
distributed, so that the accurate drawing of a minute sample is not
feasible. The small-scale determination of washing loss must be made
on a carefully drawn sample of at least 100-250 g., and must be con-
ducted similarly to the method adopted on the manufacturing scale ;
that is, by means of washing rollers. A laboratory washing mill
should follow, except as regards dimensions, the construction of a full-
scale mill.
Rubber thus cleansed is an amorphous, springy substance of sp. gr.
0-92-0-96, of a colour ranging from light yellow to dark brown,
almost black. Its most salient property is its elasticity, which is
not much affected by changes of temperature between +4' and +50'.
At low temperatures rubber becomes hard, at high temperatures
soft and sticky, and on returning to normal temperature it regains
its elasticity very slowly, or even fails to regain it completely.
Freshly cut surfaces of rubber, when gently pressed together, have
the property of adhering with a firmness equal to the cohesion of the
material itself.
^ See Henriques-Soskin, Gummi-Kalender, 1908 ; Marckwald and Frank, Herkommen und
Chemte des Kautschuks, 1904 ; and other technical literature.
400
INDIA-RUBBER AND RUBBER GOODS
Washed rubber contains, beside the rubber hydrocarbon, varying
amounts of organic oxygenated substances known generically as " rubber
resins," the chemical nature of which is not as yet cleared up. According
to the currently received view, a crude rubber is the more valuable the
less resin it contains ; it would be more correct to say that quality
depends not only on the amount, but even more on the nature of the
resins present. Rubber resins have the property, by which they are
distinguished from rubber proper, of being soluble in alcohols, acetone,
ethyl acetate, etc.
I. DETERMINATION OF RESIN, MOISTURE, AND ASH.
5 g. of washed and dried rubber are extracted with boiling acetone
in a Zuntz extractor, or other apparatus working on the same principle,
for five to eight hours. A modified form of
Zuntz extractor, devised by W. A. Caspari,
which has the advantage that there are no
cork connections, is shown in Fig. 51 ; the
water - cooled condenser (shown at the side)
slides into, and rests loosely on, the mouth of
the extractor.
To facilitate extraction, the sample should
be rolled into thin sheets, or cut into the
narrowest possible strips and spread on a
strip of muslin ; a second piece of muslin is
superposed, and the whole is rolled around a
glass rod (Fig. 52). The extract is distilled
on a water-bath and the flask containing the
residue dried at 95''- 100° till constant. The
increase in weight of the flask represents resin,
Si
^ Si
Si >^ Si Sii Si
Fio. 61.
Fio. 52.
generally so-called ; but a better term would be " acetone extract,"
since it may also contain a little depolymerised rubber. The residual
material is freed from acetone by drying at 7 5 '-80°. or at a lower
temperature in vacuo. The total loss thus sustained by the rubber,
minus the resin-content found, is taken as approximately representing
the moisture-content. Rubber of good quality does not, after drying,
adhere to the fabric.
The following Table shows the proportion of resin in some of the
CRUDE RUBBER
401
more important sorts of crude rubber, referred to washed and dried
material : —
Para (i-o-4-5)
Bolivian .
Rio Sheet
Colombian
Upper Congo (4-0-9.0)
Lower Congo
Lagos
Sierra Leone (4-o-7-o)
Red Kassai
Java
Borneo
Ceylon Plantation, Hevea
Plantation, Kickxia
Guayule .
Pontianak
. average
2-0
per <
))
3-1
1)
>)
8-3
))
>)
5-0
5)
))
£•5
))
u
4-5
■>■>
!»
4-5
))
• 1:
5-5
)>
)>
4-4
)1
'>
4-0
11
• ;;
IO-5
»
))
3-2
)>
))
7-5
))
))
i8-o
11
>)
85-0
11
In rubber manufacture the raw material is usually worked up
without any attempt at de-resinification. The determination of the
resin-content serves, therefore, mainly to indicate the proportion of
hydrocarbon in a crude rubber, and thus to give some idea of its
relative value.
An attempt to apply the properties of rubber resins to the identifica-
tion of the original rubber has been made by F. W. Hinrichsen and J.
Marcusson,^ who determined the optical rotation and the saponification
values of various resins. It appears that the resins of Para and Ceylon-
Para {Hevea) rubbers are optically inactive, whereas those of other
rubbers have specific rotations ranging from +10° to +50°. The
unsaponifiable portion of the resins is that which is responsible for the
rotation. As means to the positive identification of rubber sorts,
however, these properties, which are affected to some extent by the
treatment of the latex and other factors, cannot safely, so far as at
present studied, be relied upon.
Beside the determination of resin, it is desirable to carry out a direct
determination of moisture. For this purpose the rubber is dried in an
ordinary drying oven at 90°-95°, or in vacuo at a lower temperature.
The determination of ash and a qualitative examination of the same are
also of some value. For the method of incineration, see p. 419.
II. THE DIRECT DETERMINATION OF RUBBER.
Two methods for the direct determination of the rubber hydro-
carbon by means of derivatives have been proposed in recent years.
^ Z. angew. Chem., 1 910, 23, 49.
II
2 C
402 INDIA-RUBBER AND RUBBER GOODS
The one is based on the formation of a tetrabromide of dimethyl-r;rA;-
octadiene, which is scarcely if at all soluble in the usual rubber solvents.
The other depends upon the formation of a "nitrosite" (Harries) or
"nitrosate" (Alexander) which results from the action of nitrous fumes
upon rubber. The former derivative, when precipitated, is apt to
enclose any insoluble impurities which may be present ; nevertheless
Budde's form of the tetrabromide method is simple in execution and is
capable of giving good results. The nitrous derivatives have the
advantage that they can be isolated by means of their selective
solubilities; it matters little whether the procedure of Harries or that
of Alexander be followed, since very accurate results cannot be
obtained in either case without careful previous purification of the crude
rubber ; either method is sufficiently accurate, however, for an approxi-
mate direct determination of the rubber-content.
a. The Tetrabromide Method. (T. Budde.^)
The dry rubber is cut into small pieces, of which o- 15-0-2 g. is
soaked in 50 c.c. of carbon tetrachloride during twent}--four hours. To
the solution are added 50 c.c. of brominating reagent, which is made up
of 1000 c.c. of carbon tetrachloride, 6 c.c. of bromine, and i g. of iodine.
The mixture is allowrjd to stand, with occasional shaking, for six hours.
Half the bulk of alcohol is then added and well stirred or shaken in.
After standing overnight, the clear supernatant liquid is decanted
through an ash-free filter, the precipitate washed with a mixture of
two parts of tetrachloride to one of alcohol, and finally kneaded with
alcohol alone. The precipitate is then treated during three to four
hours with 30-40 c.c. of carbon bisulphide, and again thrown down
by the addition of 50 c.c. of petroleum spirit. The liquid is then
again filtered through the original filter and the precipitate washed
with alcohol. The filter with its solid contents is added to that
portion of the precipitate which has remained in the flask, 40 c.c.
of N/s silver nitrate solution and 20 c.c. of nitric acid (sp. gr. 1-40)
added, and the whole boiled briskly, a funnel being placed in the
mouth of the flask.
When all of the rubber bromide has been visibly converted into
yellow silver bromide, the liquid is cooled and the excess of nitrate is
titrated with iV/5 ammonium thiocyanate and iron alum by Volhard's
method. The amount of silver nitrate used up being thus known, and
thence the amount of bromine in the rubber tetrabromide, the rubber
itself is calculated by the equation : —
Bromine X 0-425 = rubber.
1 Cuinmi-Zeil., 1909, 24, 4 ; /. Soc. Chem. Ind., 1 909, 28, II40.
DETERMINATION OF RUBBER
403
b. Nitrosite Methods.
These methods are based on the fact that nitrous gases convert
rubber into pecuHar yellow derivatives having properties differing
radically from those of rubber itself; these were first described by
C. Harries.^ The nitrosite of rubber was first applied to analytical
purposes by G. Fendler- and by R. Dietrich.^ Definite analytical pro-
cedures were eventually worked out independently by Harries and by
Alexander. Although the nitrosites formed in the two methods are not
identical, they both give results which suffice for technical purposes.
The advantage which rubber nitrosite has over rubber bromide, in that
it can readily be purified by solution and reprecipitation, is counter-
Fio. 53.
balanced by the fact that the nitrosite is not easy to dry, and is far
more troublesome to prepare.
I. P. Alexander s Method!^ — For the evolution of nitrous gases a
500 c.c. flask is half filled with concentrated nitric acid (sp. gr. 1-40),
with the addition of four or five granular pieces of starch the size of
a pea, and gently warmed on the water-bath. As the evolution of gas
slackens, two or three more pieces of starch are added. The apparatus
is shown in Fig. 53. A is the flask, B a T-piece for the introduction
of starch, and C a drying-tower charged with vitreous phosphoric acid.
D, E, and F are the reaction vessels ; they are fitted with ground-in
1 Ber., 1901, 34, 2991 ; 1903, 36, 1937.
3 Pharm. Zeit., 1903, No. 78.
^ Gummi-ZeU., 1904, 18, 848.
* Z. angew, Chem,, 1907, 20, 1355.
404 INDIA-RUBBER AND RUBBER GOODS
stoppers, into which the tubulures are sealed (see Fig. 54). The joints
a, b, c, and d should be ground-in.
Each of the flasks D, E, and F contains a known weight, about
0-5 g., of acetone-extracted rubber, together with 50 c.c. of carbon tetra-
chloride. Nitrous gases are passed through until the last of the flasks
is saturated ; they are then disconnected
and allowed to stand overnight. The
supernatant liquid is now poured off", and
the residue dissolved in acetone and fil-
-^ -j tered, the filter being washed with acetone.
The solution is introduced in small quanti-
ties at a time, into a weighed flask similar
to the reaction vessels, and evaporated in
a current of hydrogen at a temperature
not exceeding 45^. The solid residue is
finally heated in the same way until the
weight is constant. The nitrosite is thus
obtained in the form of a brown vitreous mass. Frank and Marck-
wald, in conjunction with L. Weber, have found that in this form the
nitrosite retains acetone most tenaciously, so that drying to constant
weight is a very tedious operation. They therefore, after distilling off"
most of the acetone, add ether, and thus precipitate the nitrosite as
a powder which admits of easier drying. The ether, moreover, helps
to carry off" the acetone, and it is sometimes worth while to add repeated
portions of ether to the apparently dr}- powder in order to effect the
removal of the last traces of acetone.
The results are calculated according to the relation : —
I g. rubber = 2-107 S- Alexander's nitrosate.
II. C. Harries' ]\Iethod} — The apparatus for evolving nitrous gases
is the same as above, but they are prepared by heating arsenic trioxide
with nitric acid of sp. gr. 1-3. In the modification of Harries' original
method recently worked out by Korneck,- the determination is carried
out as follows : — A weighed quantity of rubber of 0-5- i-o g., which has
been purified by acetone-extraction, or by solution and re-precipitation,
is dissolved in 75 c.c. of benzene in a 200 c.c. beaker. Nitrous gases are
passed in for an hour or two until the benzene has become dark green,
the clotted precipitate being broken up from time to time. After
standing for a short time, the solvent is decanted off through a Gooch
crucible, and the precipitate is washed, covered with 75 c.c. of fresh
benzene, again treated with the gases, and allowed to stand for twenty-
four hours. The precipitate is then removed as far as possible from the
1 Ber., 1902, 35, 4429.
"^ Gummi-ZeiL, 1910, 25, 4, 42, 77 ; see also Gottlob, Z. angew. Chem., 1907, 20, 2213.
DETERMINATION OF RUBBER 405
beaker and transferred to the crucible ; the nitrosite in both vessels
is washed with petroleum spirit, and then with absolute ether. The
beaker and crucible are dried in vacuo for half an hour, and then to
constant weight in a drying oven at 80''. The contents of the beaker
are finally dissolved in 50 c.c. of warm acetone, which is poured on
to the crucible, and both are washed with acetone until free from
nitrosite, and are dried to constant weight. The combined net weight
of nitrosite thus found is calculated to rubber according to the
relation : —
I g. rubber =2- 1 25 g. Harries' nitrosite.
c. Schneider's Method.^
Frank and Marckwald adept the following procedure, which involves
some slight modifications of the original method. From 2-4 g. of
rubber are weighed out, allowed to swell in 30 c.c of chloroform, and
stirred up with a further quantity of 270 c.c. of chloroform. Dissolution
is effected by warming the mixture on the water-bath. Mechanical
impurities and certain rubber-like substances containing nitrogen and
oxygen remain undissolved ; the latter swell up greatly in the solvent
and are not always easily recognised as being insoluble. The solution
is filtered through fine silk gauze, and the residue is well washed, dried,
and weighed.- The filtrate, or an aliquot part, is warmed to 60" under
a reflux condenser, and alcohol is added, drop by drop, with constant
shaking. At first the precipitated matter redissolves ; as soon as there
is a slight permanent cloudiness, no more alcohol is added. On
standing, a considerable quantity of matter is precipitated in the form of
flakes ; this is collected on silk gauze, washed with alcohol, detached,
dried in hydrogen, and weighed. Schneider applies the term
a-caoutchouc to this fraction, which is held to be the most valuable
constituent of the rubber. To the filtrate 500 c.c. of alcohol
are added, which precipitates the second fraction, ,8-caoutchouc ; it
is collected and weighed as before. The liquid now remaining is
evaporated to dryness, and the residue is repeatedly boiled out with
absolute alcohol. By this means the resin is brought into solution, and
can be determined, whilst a final fraction, y-caoutchouc, remains
undissolved.
The first precipitate, a-caoutchouc. is by far the toughest and
best portion of the rubber ; ^-caoutchouc is rather weaker, and
y-caoutchouc is quite soft and sticky. Hence from the amount of
y-caoutchouc present, or, better, from the ratio of the three fractions,
some idea of the technical value of the rubber can be gained. It is
1 Gummi-Zeit., 1902, 16, 874.
2 Cf. D. Spence, Rep. Inst. Commercial Research in the Tropics^ Liverpool University, No. 1 3.
406 INDIA-RUBBER AND RUBBER GOODS
not known with certainty whether the insoluble nitrogenous substance
referred to above, which is counted as non-rubber, is really devoid of
value ; it is frequent!}- found to possess a high degree of toughness, so
that it ought probably not to be regarded as a detrimental constituent
unless present in abnormal amount.
d. G. Fendler's Method.^
The following procedure, which is somewhat similar to that of
Schneider, has been proposed by Fendlcr for the valuation of crude
rubber. About 3 g. of dry rubber are dissolved in 97 g. of benzene by
dint of swelling and shaking, and filtered through glass-wool, the residue
being well washed with benzene. This residue consists of the insoluble
nitrogenous matter mentioned above and a part of the mechanical
impurities, whilst the filtrate holds in solution rubber and resin.
An aliquot portion of the filtrate is poured into one and a half
times its weight of absolute alcohol, which is kept in agitation
during the addition. The rubber hydrocarbon is thus completely
precipitated, and is then collected upon glass-wool, dried, and
weighed. An error to which the method is subject lies in the tendency
of the rubber to carry down resin with it, for which reason it is
desirable to warm the solution and the alcohol to 50' or 60 before
mixing. The method yields good comparable results in experienced
hands if all proper precautions are observed.
e. D. Spence's Method.
After the crude rubber has been washed, a 10 g. sample of the air-
dried sheet is dehydrated to constant weight in a vacuum-exsiccator
over sulphuric acid. The loss in weight is added to total loss in
washing. From 4-6 g. of the dry sample are taken for acetone-
extraction in a Soxhlet or Zuntz tube, and the resin is weighed.
The extracted rubber is again dried to constancy in a vacuum-
exsiccator and the amount of rubber hydrocarbon contained determined
as follows : — A weighed quantity of about 1-5 g. is introduced into a 200
c.c. flask with about 100 c.c. of benzene, and is brought into solution by
frequent shaking. A homogeneous solution is generally obtained in a
few hours, but it sometimes happens that days are required to effect
this ; heat should on no account be applied, as no advantage is gained
thereby. .The solution is eventually made up to 200 c.c. with benzene.
An aliquot portion, say lOO c.c, is filtered through a dried and weighed
funnel fitted with a wad of glass-wool, which can usually be done in
about ten minutes. The filtrate thus obtained, of which the volume
1 Gummi-Zeit.y 1904, 19,41.
PROTEIN IN CRUDE RUBBER 407
must be accurately known, is evaporated in a weighed beaker, dried by
passing a rapid current of carbon dioxide through the hot beaker, and
weighed. This gives the amount of rubber hydrocarbon present, which
may be calculated as a percentage either of original or of washed
crude rubber.
In order to determine the insoluble impurities, the remainder of the
solution in the 200 c.c. flask is copiously diluted with benzene, and
filtered through the glass-wool filter previously used. The water
retained by the filter is washed with benzene and finally with alcohol,
dried, and weighed.
III. THE DETERMINATION OF PROTEIN IN CRUDE RUBBER.
The protein-content of a rubber is frequently of considerable
importance in relation to its value. So far as mechanical strength is
concerned, the presence of proteid matter is not necessarily a dis-
advantage ; in some kinds of rubber, e.g. that from Kickxia, the
"nerve" appears to increase with the amount of protein present On
the other hand, proteid impurities have a decided effect on the keeping
qualities of crude rubber ; when there is much protein and much
moisture, the putrefaction which the former is likely to undergo will
involve a marked deterioration of the rubber, and sometimes even its
complete ruin. In the above-described methods of analysis by solution,
the proteid matter, being insoluble in rubber solvents, remains in the
filtration-residue. Its detection and determination, however, are best
carried out on the original rubber {i.e. on the washed sheet). For the
determination Kjeldahl's method is employed, and it is usual to
calculate by means of the usual factor 6-25 in converting nitrogen into
proteid, although there is no direct evidence that this factor is strictly
applicable.
Vulcanised and Manufactured Rubber.
The rubber hydrocarbon readily combines with sulphur to form an
addition-product ; it is this which forms the basis of the great majority
of manufactured rubber goods. The process by which this combination
is brought about is known as "vulcanisation" or "curing"; there are
two very distinct methods of vulcanisation, the "hot" and the "cold."
According to the former, rubber is mixed with pulverulent sulphur and
heated to such a temperature, and for such a time, as will lead to the
result desired. Cold-curing consists in treating the surface of the
rubber with a solution of sulphur chloride (SgCU) at ordinary tempera-
tures, or exposing it to the vapours of sulphur chloride. Soft rubber
goods are so vulcanised that there is comparatively little sulphur
408 INDIA-RUBBER AND RUBBER GOODS
combined with the rubber ; that is, they are heated with a low percen-
tage of sulphur to 120-135°, or fo"" ^'^^Y short periods of time
to i70°-i8o . Vulcanised soft rubber possesses at least as much tensile
and shearing elasticity as raw rubber, and in addition it preserves these
properties from low temperatures up to the point at which the rubber
molecule begins to undergo decomposition. The properties of self-
adhesion and plasticity are no longer found in rubber which has been
vulcanised.
When rubber is mixed with a large quantity of sulphur and
cured for a long time, or at comparative!}- high temperatures, the
result is a quite distinct substance, ebonite : this is a horn-like solid
which has still a certain shearing elasticity, but no tensile elasticity
whatever.
Whilst raw rubber swells and dissolves in chloroform, carbon
bisulphide, benzene, petroleum naphtha, and other solvents, the
extent to which vulcanised rubber swells in these substances
diminishes as the degree of vulcanisation increases, and becomes
practically nil in the case of ebonite. Vulcanised rubber is remark-
ably inert towards chemical reagents ; with a few exceptions, there
is no reagent which attacks it, short of breaking down the rubber
molecule completely.
For soft rubber goods or ebonites made of rubber and sulphur and
nothing else, chemical analysis resolves itself into the determination of
resin, combined sulphur, and free sulphur, possibly also of ash.
Vulcanised rubber invariably contains some free sulphur over and
above that which is combined with the rubber hydrocarbon. Free
sulphur is soluble in boiling acetone, and is, therefore, extracted
together with the resin by the method referred to on p. 425. The
weight lost by the rubber on extraction represents resin plus free
sulphur; the sulphur-content of the original minus the sulphur-content
of the extracted material represents free sulphur. It should be noted
that the proportion of resin to hydrocarbon in a rubber is apt to
increase in the process of vulcanisation. For the determination of
sulphur as such, see p. 419.
Soft rubber contains from i to 10 per cent, of combined sulphur^
whilst ebonite contains 25-34 P^f cent. Manufactured rubbers contain-
ing intermediate percentages are also met wath.
In vulcanisation by the cold-cure process both sulphur and chlorine
enter into combination with the rubber h}-drocarbon. The reaction
takes place instantaneously, and rubber thus vulcanised does not
permit of the further penetration of sulphur chloride ; the cold cure can,
therefore, be applied only to articles which have received their final
shape, and of which only a thin superficial layer needs to be vulcanised.
The commonest type of cold-cured goods are so-called cut sheet, and
ACCESSORY MATERIALS 409
composite articles made therefrom ; this consists of sheet which is
pared by knives from solid blocks of rubber. In addition, calendered
sheet, proofed fabrics, and dipped goods lend themselves well to cold
curing. The original cut sheet can always be recognised by the
characteristic striae arising from the action of the knife-blades ;
nowadays these marks are often artificially produced on calendered
sheet by pressing the sheet on suitable fabrics, or, yet more simply, by
the use of engraved rollers.
Dipped goods are made from solutions of clean unwashed rubber ;
the method applies especially to transparent articles. It is also possible
to make seamless goods from mixtures of rubber solution with sulphur,
and to heat-cure them after evaporation of the solvent.
Methods of vulcanisation other than the hot and cold cures are not
in technical use. It is sometimes stated that certain metallic sulphides,
e.£^. those of antimony, alkalis, or lead, are vulcanising agents, but this
is a fallacy. In reality it is the free sulphur associated with these
sulphides which effects vulcanisation, the sulphides themselves acting
merely as filters, or pigments, or conductors of heat. It may well be,
however, that metallic sulphides play a part in vulcanisation as catalytic
agents;^ in many cases 'their presence seems indispensable to start the
reaction.
B. ACCESSORY MATERIALS OF THE RUBBER
INDUSTRY.
The principal raw material of the rubber industry has been dealt
with in the foregoing section ; numerous other substances are also used
in making rubber goods.
Manufactured rubber seldom takes the form of pure vulcanised
rubber without admixtures. This is mainly due to the fact that the
purpose to which manufactured rubber is applied mostly call for some-
thing quite different from unmixed vulcanised rubber ; filling materials
are, moreover, largely employed for the sake of cheapness, and some-
times also with a view to producing deception.
In interpreting analytical results, therefore, the object with which
the various ingredients have been added must be considered, and
whether this may be regarded as useful, indifferent, or positively
harmful, according to the nature of the case. The value and properties
of rubber goods are very widely affected according to the nature and
amount of the filling materials added.
Few substances belonging to the domain of inorganic and organic
chemistry have escaped the test of being incorporated in rubber
mixings. A limited but still fairly large number have survived for
1 Cf. Gummi-Zeit., 1 905, 19, 272.
410
INDIA-RUBBER AND RUBBER GOODS
normal or occasional use.
materials: —
The following are the more important filling
Aluminium (in powder).
Iron (in powder).
Zinc (in powder).
Brass (in powder).
Litharge.
Red Lead.
White Lead.
Lead Sulphide.
Lead Sulphate.
Lead Chromate.
Zinc Oxide.
Zinc Sulphide.
Barytes.
Inorganic Filling Materials.
Lithopone.
.A.ntimony Sulphide.
Kermes.
V'ermilion (Mercuric Sul-
phide).
Ferric Oxide.
Cadmium Sulphide.
Lime.
Chalk
Calcium Sulphide.
Calcium Sulphate, anhy-
drous.
Magnesia.
Magnesium Carbonate.
Magnesium-Aluminium Sili-
cates (Fossil meal, Kiesel-
guhr, Talite, Atmoid,
Florida Earth, Meer-
schaum, Asbestos, Talc).
Ultramarine.
Clay of various tints.
Mica.
Glass powder.
Pumice powder.
Calcium Sulphate, hydrated. Various inorganic pigments.
Organic Filling Materials.
White Substitute.
Brown Substitute.
Fatty Oils.
Lanoline.
Rosin (Colophony).
Various Resins.
Rubber Resin.
Resin Oils.
Vaseline.
Ceresin.
Paraffin.
Mineral Oils.
Beeswax.
Asphaltum (Bitumen).
Mineral Rubber (Acid-
pitches and products of
Mineral-pitches).
Coal-tar Pitch.
Resin Pitch.
Petroleum and Lignite
Pitch
Lampblack.
Graphite.
Earthy Lignite.
Starch.
Dextrin.
Potato meal.
Plant fibres (Cellulose).
Rubber Waste.
Reclaimed Rubber.
Viscose.
Organic Dyestuflfs.
In most cases a rubber mixing contains not one but several of these
ingredients, of which many are themselves of a composite character.
Consequently the analysis of rubber goods, and especially the correct
interpretation of analyses, is a matter of no small difficulty and requires
considerable experience.
Substitutes.
By far the most important organic filling materials are a class
of substances which owe their discovery and application solely to
the requirements of the rubber industry, and are technically known
under the name of " Substitute " (/'>. Factice, Gcr. Faktis). There are
two di.stinct kinds of substitute : white, and brown or black.
White Substitute is prepared by treating fatty oils, notably rape-
and cotton-seed oils, with sulphur chloride, and forms loose, spongy,
compressible aggregates or crumbs of a light yellow to white (rarely
light brown) colour. The finest qualities, which, from the origin of
SUBSTITUTES 411
their manufacture, still sometimes go by the name of French substitutes,
are made from castor oil. In recent times ready-dyed substitutes have
been brought on the market. These latter are made by adding a
soluble dyestuffto the oil before acting on it with sulphur chloride, in
the proportion of i to lOO or i to 300, according to the tinctorial power
of the dye.
The reaction which takes place when fatty oils are converted to
solid "substitute" is much the same as that by which rubber is
vulcanised with sulphur chloride. Chlorine and sulphur add themselves
directly, though the details of the reaction are not as yet understood, to
the glyceride molecule, or rather, to so much of the oil as represents
unsaturated glycerides. The solid products contain in general 6-8
per cent, of sulphur, together with an equivalent amount of chlorine
from which it follows that the absolute quantities of sulphur and chlorine
present are approximately equal. Saturated sulphur-chloride addition-
products are not soluble without decomposition in the ordinary organic
solvents ; but on treatment with alcoholic potassium or sodium
hydroxide they behave exactly like normal glycerides and go into
solution with formation of soaps soluble in water. In this process of
saponification the chlorine is liberated almost completely, whilst the
sulphur remains in combination with the fatty acid. Hence, by dissolv-
ing out a substitute by means of alcoholic potassium hydroxide and
determining the sulphur in the fatty acid so obtained, the sulphur
originally present in the substitute can be accurately ascertained. The
chlorine of white substitute is altogether somewhat loosely attached ;
thus, when rubber mixtures containing white substitute are subjected to
the heat-cure, a portion of the chlorine is liberated, probably as hydro-
chloric acid. White substitute, therefore, is not always a desirable
ingredient in heat-cured goods. If, for instance, such mixings are spread
on fabric and then heat-cured, the chlorine set free may act injuriously
on the strength of the fabric, or even rot it completely.
Brown Substitute contains no chlorine, apart from traces. There
are such preparations, however, as " mixed substitutes," which have
been first treated with an inadequate proportion of sulphur and then
finished off with sulphur chloride. Brown substitutes proper are made
by heating fatty oils, as such or "blown" {i.e. oxidised), with sulphur
alone to somewhat high temperatures ; they thus bear the same relation
to white substitutes as heat-cured to cold-cured rubber. They come into
the market in the form of brown to black, moderately elastic, slabs or
irregular blocks, or ground into crumby powder. Their sulphur-content
is very variable, ranging from 3 to 18 per cent. Though otherwise
insoluble, they are readily saponified with formation of sulphuretted
fatty acids. The substitutes of commerce do not always consist
exclusively of glyceride sulphides or chlorosulphides. They sometimes
412 INDIA-RUBBER AND RUBBER GOODS
contain inorganic admixtures, or paraffin wax or oil (as in so-called
" Para francais "), and usually a more or less considerable proportion of
unchanged or incompletely vulcanised fatty oil. Apart from their
application in connection with rubber, they are now used for making
pencil erasers and the like, consisting of nothing but substitute with
mineral fillers.
The chemical examination of substitutes is important. Substitutes
which have been insufficiently or negligently vulcanised, or those which
have been vulcanised from imperfectly boiled oils, may seriously impair
the keeping qualities of rubber goods in which they form an ingredient.
A good substitute should contain little or no free sulphur, and not more
than 3 per cent, of ash ; nor should it contain any considerable quantity
of mineral oil or paraffin wax, unless it be of the type in which a
definite admixture of this kind is known and allowed for. Thus the
"Para francais" type of brown substitute always contains 15-20 per
cent, of paraffin wax, and sometimes as much as 40 per cent. In
analysis, free sulphur, unchanged or incompletely vulcanised fatty oil,
and petroleum derivatives are separated by extraction with acetone,
and weighed together. Hydrocarbon oils and waxes are isolated, after
saponification, according to the method described in the Section on
" Lubricants," this Vol., p. 89. Total chlorine and sulphur in white sub-
stitute, and total sulphur in brown substitute, are determined in the
same way as in rubber goods {cf. mfra, p. 419). Chlorine and sulphur
may be determined in one and the same sample by adding a little
silver nitrate to the nitric acid with which the material is decomposed ;
any chlorine which might otherwise escape is thus retained from the
outset. The Carius method is not to be recommended.
To obtain a more complete knowledge of the nature of a substitute,
the saponifiable portion of the acetone-soluble matter may be assayed
for sulphur, and its iodine value may be determined, and also the
iodine value of the saponifiable portion of the residue from acetone
extraction.
The scheme of analysis is as follows : —
1. Extraction of 2-4 g. with acetone in a Soxhlet or Zuntz apparatus.
Both extract and residue are examined for unsaponifiable matter by
the Spitz and Honig method, and this, if present, is identified as far as
possible. In the isolated fatty acids combined sulphur is determined,
and, if desired, the iodine value.
2. Determination of total sulphur and chlorine.
3. Incineration and examination of the ash.
4. Determination of saponifiable and unsaponifiable matter in the
original material, and of sulphur, iodine value, and saponification value
in the saponifiable portion. In most cases this procedure replaces, and
is to be preferred to, that given under i.
ORGANIC ACCESSORIES 413
Definite standards for the valuation of substitutes cannot well be
set up. The following qualitative tests, supplemented by analyses 2
and 3, are useful for differentiating good substitutes from bad : —
a. On shaking with 20 parts of cold water, only the faintest acid
reaction with Congo red paper should be produced.
b. On digesting at 50^-60° for half an hour with 20 parts of 96 per
cent, alcohol, silver nitrate should give only a faint opalescence after an
hour or so. The alcoholic extract, after cooling, filtering, and evaporat-
ing, should leav'e a residue amounting to not more than 0-4 per cent, of
the substitute.
c. On heating for an hour to ioo°-i 10°, there should be no perceptible
change and no evolution of acid vapours. This applies more especially
to dry white substitutes.
d. On heating for one to four hours in a sealed tube to 150°, there
should be no evidence of pressure or of acid vapours when the cooled
tube is opened.
Other Organic Accessories.
Apart from substitutes, the chief organic filling materials are : —
Bitumen, tar, pitch, mineral oil, paraffin wax, ceresin, beeswax, fatty
oils (especially in admixture with reclaimed rubber), rosin oil, resin,
lanoline (rarely used), and the other substances enumerated on p. 410.
Details as to the examination of each of these are given in the
Sections concerned with the respective substances. The most important
condition for the applicability of pitchy, oily, and similar materials is
that they should be completely free from moisture. The following
special points may be noted : —
Bitumen. — In rubber mixings only bitumens of superior quality,
obtained from the mineral by liquation or extraction, should be
employed. The most suitable bitumens are those which have a
softening point (as determined by Kramer and Sarnow's method ; see
Section on " Coal Tar," Vol. II., Part II., p. 837) of not less than 30°-35°.
The comparatively rare varieties which soften about 50° and contain a
good deal of combined sulphur are particularly prized. Bitumens are
partially soluble in boiling acetone.
Pitch. — Coal-tar pitch is largely used in the manufacture of goloshes
and other goods, and is generally prepared on the spot by boiling down
tar. It usually has a softening point of 52° or over. In the boiling
down a certain amount of pulverulent carbon is produced, the total
quantity of which may amount to 15-35 P*^^ cent.; it is, therefore,
desirable that the original tar contain as little carbon as possible, and
that excessive local heating of the boiling-pans be avoided. For the
determination of pulverulent carbon, see Section on " Coal Tar," Vol. II.,
4U INDIA-llLBBER AND RUBBER GOODS
Part II., p. 759. When rubber goods containing pitch are analysed,
this carbon appears as lampblack, and cannot be distinguished from
intentionally added lampblack. A portion of the pitch is soluble in
acetone. From these facts it follows that an accurate determination
of pitch in rubber goods is impracticable. Approximate data can be
obtained by extraction with pyridine or with ethyl acetate.
Solvent Naphtha. — The benzene homologues derived from coal-tar
are much in use as rubber solvents. Only the most highly purified
naphthas are admissible in rubber manufacture ; they must not impart
the slightest odour to the rubber from which they have evaporated.
Methods of examining coal-tar naphthas are given in the Section on
"Coal Tar," Vol. II., Part II., pp. 779 ct seq. The varieties in common
use are the benzene, toluene, and xylene fractions. Of a solvent naphtha
not less than 95 per cent, should distil over up to 155'.^
Shale Spirit. — This solvent is prepared from the products of de-
structive distillation of bituminous shale, and generally begins to distil
at about 80° ; it should distil over completely below 140". Shale spirit
consists of benzene, paraffin hydrocarbons, and naphthene hydrocarbons
in varying proportions.
Petroleum Naphtha. — Paraffin hydrocarbons are used as rubber
solvents, and as diluents of sulphur chloride in the cold-cure; for the
latter purpose, however, they are not so good as benzene, and far less
effective than carbon bisulphide. In selecting the most suitable fraction,
it should be noted that very low boiling points involve much loss by
evaporation, and that such naphthas are relatively poor solvents for
rubber. On the other hand, heavy naphthas are even more to be
avoided, since they impart a tenacious odour to rubber goods, and are
liable to soften the rubber under the influence of heat. The most
useful petroleum naphthas are those of which 95 per cent, distils
between 100 and 140 .
Reclaimed Rubber. — An ingredient of manufactured rubber goods
which is now used in enormous quantities, is used-up rubber scrap
which, by various processes, has been rendered fit to be incorporated in
fresh mixings. The chemical examination of this article, which is not
easily valued by inspection, is of considerable importance.
In the first place the ash, or preferably the true mineral constituents,
should be determined both qualitatively and quantitatively. The
acetone extract should also be similarly examined. Reclaiming pro-
cesses convert the substitutes originally present into acetone-soluble
matter to a large extent. Free sulphur is rarcl}' present in appreciable
quantity, but, if it is, the sulphur-content should be accurately known.
The kind of reclaimed rubber which is prepared by plasticising ground
rubber waste with much mineral or rosin oil suffers in value by the
' For further details, cf. Gummi-Zeit,, 1903, 17, 793.
ORGANIC AND INORGANIC ACCESSORIES 415
presence of these additions, and by the fact that it contains a relatively
high proportion of ash to true rubber. It is frequently possible to
recognise the particular reclaiming process which has been applied, as
when the presence of alkali or of acid, or of certain solvents, is detected.
Generally speaking, the examination of reclaimed rubber is conducted
similarly to the analysis of rubber goods. In many cases the nitrosite
or tetrabromide method serves for determining the amount of true
rubber present. The acetone extract may contain, beside oils, resins,
etc., certain decomposition-products of rubber which somewhat resemble
paraffin hydrocarbons ; these may be recognised, quantitatively at least,
by the formation of insoluble bromides similar to rubber tetrabromide.
Organic Colouring Matters. — Of these the representatives are lake
pigments and those dyes which, being insoluble in water, but soluble in
oils or naphthas, are applicable to cold-cured goods. They should be
assayed for ash, and further examined qualitatively by the methods in
use for dyes ; the most trustworthy information is to be obtained by
spectroscopic methods.
Fabrics intended to be impregnated with rubber should be free
from sizing ; they should, moreover, be tested for the presence of copper,
which sometimes occui3 in dyed fabrics as a mordant, and has an
injurious effect on vulcanised rubber, especially on long standing. It
may also be necessary to determine the number of threads in unit area,
the weight per unit area, and the tensile strength. In balloon fabrics
the important points are proper mode of weaving and adequate protec-
tion of the exposed side, by means of pigments, from the sun's rays.
Inorganic Accessories.
Sulphur. — This, of all rubber accessories, is the one used in greatest
quantity. For the examination of sulphur, see Vol. I., Part I., p. 264.
The principal desiderata from the standpoint of the manufacture of
rubber are, freedom from moisture and acidity, and a high degree of
fineness.
Sulphur Chloride. — Uniformly good results in the cold-cure are
only to be obtained with very pure sulphur chloride. The presence of
dichloride, that is, excess of chlorine, produces a harsh, shrivelled surface
on the goods, whilst free sulphur, which is frequently present in
considerable quantity, causes the goods to "sulphur up." The latter
impurity is the less noxious of the two, and may be tolerated to the
extent of 3-5 per cent. The following method of analysis is prescribed
by Weber : —
From 20-30 g. of sulphur chloride are weighed by difTerence out of
a small stoppered bottle into a litre flask half filled with water. The
flask is stoppered and shaken until there are no more oily drops, and
416
INDIA-RL'BBER AND RUBBER GOODS
is then warmed for a short time on a water-bath. For every lo g. of
sulphur chloride i c.c. of nitric acid (sp. gr. 1-42) is added. The liquid
is cooled, made up to the mark, and filtered through a dry pleated
filter. The chlorine is determined either gravimetrically or volumetri-
cally in an aliquot portion of the filtrate. The excess of chlorine or of
sulphur present may be calculated from the content of chlorine.
Antimony Sulphide. — The red antimony pigment used in the
rubber industry always contains more or less free sulphur; even the
purest form obtainable contains about 8 per cent, as an inevitable
consequence of the method of manufacture. A wide variety of
antimony sulphides is supplied by the makers, differing in the content
of free sulphur {e.g. 8, 15, 20, 25, etc., per cent.) intentionally added;
these are commonly sold on a guarantee of a definite sulphur-content.
The ratio of combined sulphur to antimony in commercial sulphides is
apt to vary, as is shown in the subjoined analyses : —
A.
B.
C.
D.
LalKjrator>'
E. I'reparatioiis
(Heuriques).
SiOo
CuSO, ....
Frees . . . .
Sb
S combined with Sb .
2-85
15-45
17-10
44-03
19-97
3-38
8-55
61-28
27-57
0-60
6-55
11-06
53-54
27-91
1-56
14-33
24-00
41-53
18-30
40-06
40-30
19-09
8-10
58-24
33-47
8-80
58-84
32-36
Sb^S.,
Sb2S3. ....
16-54
47-46
21-84
67-01
43-18
38-27
13-64 20-45
45-19 38-94
66-66
25-05
58-14
33-06
Free sulphur is determined by extracting a weighed sample, dried
at 50°, in a Soxhlet tube with carbon bisulphide. The powder is
placed in a Schleicher and Schull paper thimble, which is weighed in a
stoppered weighing-bottle before and after extraction. The further
analysis may be carried out according to the following method, due to
F, Jacobsohn :^ —
For the estimation of the total sulphur, the substance is evaporated
in a dish with concentrated nitric acid ; the residue is cautiously treated
with fuming nitric acid, and again taken to dryness. After lixiviation
with hot water, the sulphur is determined as barium sulphate in the
usual manner.
Antimony is determined as the oxide, SbOo, together with any
other mineral matter present. This is done by oxidising the extracted
sulphide with fuming nitric acid, taking to dryness, and igniting.
The separation of antimony from other mineral constituents is
effected as follows: — The oxidised residue obtained as above is mixed
' C/tem. ZeiL, 1908, 32, 984 ; /. Soc, Chem. Ind., 1908, 27, 169.
INORGANIC ACCESSORIES 417
with ammonium chloride and again ignited. By this means the
antimony is volatilised away, whilst other mineral matter remains
unaffected. If there is any calcium present as antimoniate or sulphanti-
moniate, an error is thereby introduced, but this is generally very
small.
The more exact analytical separation is carried out by evaporating
the sulphide with hydrochloric acid, oxidising with a drop or two or
nitric acid, dissolving in dilute hydrochloric acid with a little tartaric
acid, filtering off the silica, and precipitating the antimony with sul-
phuretted hydrogen. The antimony sulphide is weighed and the
calcium determined in the filtrate as usual.
Vermilion. — This is the most brilliant of red rubber pigments, and
has the greatest covering power. It is met with in several shades,
but invariably consists of practically pure mercuric sulphide, unless
adulterated. Sometimes small quantities of insoluble aniline dyes are
added to enhance the colour. These may be isolated by extraction
with ether, and duly identified ; usually they are dyes of the azo- or
eosine series. Adulteration with aniline dyes, however, is very seldom
practised. It is well to test for soluble mercury salts, since rubber
goods pigmented with -vermilion are often used in contact with
beverages or foodstuffs.
Covering Power is determined by mixing a little of the material
with oil, spreading on a clean dry glass plate, and making comparative
tests.
The organic and inorganic compounding materials not dealt with
above call for no special comment. Methods of analysis in each case
will be found in other Sections. For the rubber industry, fineness of
division, dryness, and freedom from acidity are indispensable.
C. THE ANALYSIS OF RUBBER GOODS.
It will have been gathered from the foregoing that manufactured
rubber articles may be — and mostly are — composite substances of the
greatest complexity. The various non-rubber ingredients being
generally impure chemicals, or themselves of a composite nature, it is
seldom possible to estimate them accurately by analysis ; all that can
be done, in the first instance, is to determine the elements or simple
compounds present in the sample. Moreover, the variety of raw rubber
originally employed is hardly ever to be diagnosed with certainty from
the results of analysis. Hence the correct interpretation of a complex
analysis is largely a matter of experience, for which a scheme of
general applicability cannot be drawn up. Some general notes in this
connection are given in the last paragraph of this Section (p. 435).
Ill 2 D
418 INDIA-RUBBER AND RUBBER GOODS
Special Methods of Analysis.
I. Preparation of the Sample.
To counteract possible lack of homogeneity resulting from the
methods of manufacture, it is well to begin by taking a fairly large
quantity of material and preparing an average sample. This may best
be done by reducing the rubber to a state of powder.
Stiff rubber goods and ebonites can quite easily be powdered by
means of a rasp or file. The softer kinds of goods, e.g. sheeting and
tubing, can be similarly comminuted by tying them up in tight rolls
and applying the file at right angles to the axis. Unvulcanised goods,
cut sheet, and very thin sheeting or proofing cannot be treated in
this way ; in this case the material is kneaded or crumpled together,
and narrow strips are cut out in diagonal directions. The recom-
mendation is often made to reduce the material to crumb on a
small pair of rollers. This, however, is a questionable procedure, because
vulcanised rubber is apt to be altered, on mastication, b}- a partial
de-polymerisation of the rubber molecule, the consequence being that
its conditions of solubility and thence the analytical results, are more or
less affected.
A grinding apparatus, consisting of two solid grooved gun-metal
rollers, for the preparation of vulcanised rubber for analysis, has been
recently described by L. Archbutt.^
2. Desiccation.
The drying of rubber is an anal}-tical operation which recurs frequently
and calls for special care. The best method is to weigh the rubber in a
porcelain boat, place the boat, or several boats, in a glass tube heated
to 8o''-95 , and pass a continuous current of hydrogen or carbon dioxide
through the tube. In this way all danger of oxidation is avoided.
Drying can also be conducted in a vacuum oven, the precaution being
taken to allow the oven to cool down before opening ; this method
permits of working at low temperatures, but is not without its dis-
advantages. Drying in a current of coal gas is much practised, but is
not to be recommended, because rubber has a tendency to absorb
hydrocarbons out of the gas. The risk incurred in drying in an
ordinary oven at 90^-95" is that rubber, especially vulcanised goods with
much filling, invariably undergoes some slight oxidation in the process ;
nevertheless this method is much the simplest, and, in cautious and
experienced hands, gives quite acceptable results.
' Analyst, 1913, 38, 550.
ANALYSIS OF RUBBER GOODS 419
3. Incineration.
Formerly the chief weight was laid on the percentage of ash in all
rubber analyses. The ash, indeed, always corresponds approximately to
the sum of the mineral constituents present. There are, however, numer-
ous possible sources of error ; thus carbonates and sulphates may undergo
more or less decomposition, oxides may combine with sulphur, and
volatile metallic compounds may be driven off. The ash of filled
rubber goods, therefore, cannot be regarded as an accurate index of the
proportion of filling material. It should always be determined,
however, because it serves as a check on the inorganic part of the
analysis, and it may also be needed as an auxiliary factor in the
determination of substitute. To determine the ash, about 0-5 g. is
weighed into a flat porcelain dish of about 5 cm. diameter. The
dish is placed on a hole of 3-4 cm. diameter cut in a piece of metal
or asbestos sheet, and is gently heated in such a way that the
rubber substance fumes off without taking fire. If the rubber is allowed
to burn, there is always a considerable deposition of soot, which has
to be removed by vigorous ignition ; and not only is time thus lost, but
the ash may undergo further decomposition than is necessary. Care-
fully performed incinerations take from ten to twenty minutes, and can
be carried out at temperatures which leave most of the carbonate
present undecomposed. Finally, the ash is weighed, and may serve for
a qualitative analysis of the mineral matter.
When the rubber contains no fillers, the ash represents the mineral
impurities present in the original rubber ; these, even in well-washed
rubbers, always amount to several tenths of a per cent, and in some
varieties even to several per cent.
4. Total Sulphur.
Four methods for the estimation of sulphur are given of which the
one under {b) may be especially recommended. It demands more care
than Method {a), but saves a good deal of time.^ A method for the
estimation of free sulphur, which is contained in the acetone extract,
is described on p. 438.
lilethod (a). — About i g. of the comminuted sample is weighed into
a small lipped beaker and is treated with 15-20 c.c. of pure concentrated
nitric acid (sp. gr. 1-4). The beaker is covered with a perforated watch-
glass and slowly warmed on a water-bath. A brisk reaction, which
should not go so far as to cause spirting, takes place and la.sts for about
an hour. At the end of this time the contents of the beaker are
^ Methods (a) and (<5) are modified forms of Henriques' method, Z,anal, Chem.^ 1899, 12, 802.
420 INDIA-HL'BBER AND RUBBER GOODS
rinsed with strong acid into a small porcelain basin of about 5 cm.
diameter and evaporated to dryness, A short length of glass rod is
used from the beginning for pushing and stirring, and is eventually
allowed to remain in the dish. The substance is subjected to two
more evaporations with about 3 c.c. of nitric acid. When it has been
brought to a syrupy consistency, it is moistened with a few drops of
alcohol and mi.xed, whilst still warm, with about 5 g. of finely powdered
sodium carbonate and potassium nitrate in the proportion of 5 parts of
the former to 3 of the latter. The magma is covered with a layer of
the same mixture and is dried at I20'-I30'. Now follows the critical
stage of the analysis, namely, the fusion, in which very great care must
be exercised to avoid sudden decompositions having the character of
a mild explosion. The basin is supported about 5 cm. above a small
luminous Bunsen flame which is increased little by little, a second
similar basin being placed, mouth downwards, upon it. At first it may
be necessary from time to time to wipe away condensed moisture from
the covering basin. Should an explosive reaction presently take place,
the spatterings are taken up by the covering basin and are afterwards
fused in it by themselves. Under proper conditions, however, the mass
gradually turns brown at the edges and can then be heated with more
confidence, the brown matter which condenses on the cover being free
from sulphur. Finally, the contents of the basin are brought into
complete fusion, and are stirred with the glass rod mentioned above,
which is held in a pair of tongs. The fusion occupies from one and a
half to two and a half hours.
Special basins^ with a thin glaze inside only are supplied for this
fusion. In lixiviating, it is best not to cool down the melt completely,
but to add hot water whilst it is still warm. The basin having been
rinsed clean, the insoluble residue (mainly oxides and carbonates) is
filtered off and washed until the runnings no longer give a reaction for
sulphates.
In the clear filtrate there will be an appreciable quantity of silica
only if the rubber itself contains much siliceous matter; on this point a
qualitative examination of the ash will have supplied information. It
will then be necessary to acidify, take to dryness, redissolve, and filter.
The total sulphur is then precipitated and weighed in the usual way as
barium sulphate. There being an excess of nitrates present, it is
advisable to wash the precipitate with hot, dilute hydrochloric acid. In
the case of ebonites or soft goods heavily loaded with sulphides and
sulphates, an aliquot part of the filtrate, rather than the whole, should
be taken for precipitation.
The insoluble residue on the filter can be made use of for determin-
ing the mineral filling materials of the rubber, since it contains
1 Made by Haldenwanger & Co., Charlottenburg.
TOTAL SULPHUR 421
practically all of the metals concerned in the form of oxides or
carbonates. Negligible quantities of lead and calcium may go into
the filtrate, and sufficient antimony to be worth precipitating with
sulphuretted hydrogen in the final liquor filtered from the barium
sulphate. The insoluble residue is then treated with hydrochloric acid,
when only silica remains behind, and the resulting solution is subjected
to the usual course of quantitative analysis. The only metal which
cannot thus be determined is mercury, most of which escapes during
the fusion. Certain superior qualities of red rubber goods contain
vermilion ; in this case mercury must be determined by itself in a
separate portion of the sample. The same procedure may with
advantage be applied to antimony (cf. infra, p. 427).
Method {b). — About half a gram of comminuted rubber is weighed
directly into a small basin and allowed to stand for an hour with 2-3
c.c. of concentrated nitric acid. The basin is then placed on a cold
water-bath, which is gradually heated up; in this way a too violent
reaction between the rubber and the acid is avoided. The first portion
of acid having been evaporated, 5 c.c. of fuming nitric acid are added,
and from this point onwards operations are conducted exactly as under
Method {a).
Alethod {c). — The familiar Carius method, as adapted to rubber, is
carried out as follows: — From o-5-i-o g. of rubber are weighed into a
very small test tube and placed in a tube of special glass, into which
3-5 c.c. of fuming nitric acid have previously been poured. The open
end of the tube is then drawn out to a capillary in the usual way, and
sealed. By inclining the tube the acid is very gradually and cautiously
brought into contact with the rubber ; during this operation the tube
must be held in an iron mantle or well wrapped in cloths, since there is
some risk of explosion, especially with rubber of low vulcanisation or
containing substitute. After cooling down for an hour or so the
pressure is released and the tube re-sealed ; it is then heated to about
200° in a tube-furnace. The final product will consist not only of a
liquid but also of a solid sediment which may contain sulphates ; the
whole is, therefore, rinsed into a basin, evaporated, and fused with
potassium and sodium carbonates. The melt is dealt with as under
Method {a), and serves for the determination of the total sulphur and
of the mineral ingredients.
Method (d). — It has been proposed to use v. Konek's process, by
which the rubber is decomposed with sodium peroxide for the determina-
tion of sulphur in rubber. In some cases it is possible to determine the
sulphur, as sulphate, volumetrically by the method of J, D. Pennock
and D. A. Morton.^
1 /. Amer. Chem. Soc, 1903, 25, 1265 ; /. Soc, Chem. hid., 1904, 23, 131. For details of the
whole process, see Alexander, Gummi-Zeit,, 1904, 18, 729.
422 INDIA-RUBBER AND RUBBER GOODS
5. Chlorine.
Any chlorine present in rubber goods is practically always in
organic combination. To determine it, i g. of rubber is cautiously
fused with a mixture of sodium carbonate and potassium nitrate ; no
volatilisation of chlorine need be feared. The melt is dissolved in
water acidified with nitric acid, and the chlorine determined either
volumetrically or gravimetrically. The fusion-mixture should always
be tested, not only for chloride but also for chlorate.
In unvulcanised or heat-cured goods the presence of any appreciable
quantity of chlorine points to the presence of white substitute. The
latter generally contains from 6-8 per cent, of chlorine, so that its
approximate amount in the rubber may thus be calculated. In cold-
cured goods free from white substitute the chlorine is present as a
vulcanising agent, and forms part of the sulphur chloride taken up in
the cure. Should substitutes be present, it is necessary to separate
them by extraction with alcoholic potassium hydroxide, and so to
differentiate between the sulphur and chlorine belonging to the rubber
and the substitute respectively.
6. Sulphur Combined with Metals.
Sulphur may be present in inorganic combination in the form of Qr)
sulphides or (d) sulphates.
(a) SulpJmr in the form of S?ilp/ndes. — To determine sulphides, the
rubber is boiled with hydrochloric acid until sulphuretted hydrogen can
no longer be detected in the vapours. The rubber is then dried and
the contained sulphur determined. The difference between the sulphur
so found and the total sulphur gives the sulphide-sulphur. There is
seldom, however, any need to carry out this determination. Lead
sulphide, which is often present in rubber, will have rarely been added
as such, but is produced by the reaction of sulphur on litharge in
vulcanisation. Sulphur combined with antimony, in red rubber goods,
may be calculated from the antimony present on the approximately
correct assumption that the sulphide is SKS^ (see above, p. 416).
Similarly, sulphide-sulphur may be present as HgS (vermilion) or as
ZnS (in the form of lithopone).
{b) Sulphur in tJic form of Sulphates. — The only sulphates commonly
used as fillers are those of barium and calcium. If barium is present,
and if on boiling the rubber with dilute hydrochloric acid no barium
goes into solution, the metal is present wholly as the sulphate, and the
combined sulphur can be calculated from the barium. To determine
calcium sulphate, a weighed quantity of rubber is thoroughly boiled out
CARBONIC ACID. FILLING MATERIALS 423
with hydrochloric acid and the dissolved sulphate precipitated in the
usual manner. Any other sulphates present in small quantity will
have been formed in vulcanisation, or have been introduced by reclaimed
rubber.
7. Carbonic Acid.
Among the commonest inorganic fillers are carbonates, especially
those of calcium, and, in minor degree, those of lead, zinc, and magnesium.
The estimation of these carbonates, in presence of the corresponding
oxides, is effected by decomposing i g. of rubber with dilute phosphoric
or hydrochloric acid in any of the well-known forms of apparatus, and
determining the carbon dioxide liberated by loss. To prevent loss of
sulphuretted hydrogen evolved from sulphides, the rubber is in the first
instance moistened with copper sulphate solution to which 50 per cent,
of alcohol (to overcome surface tension) has been added. The method
can be employed only with material in the form of tolerably fine powder,
and is useless for unvulcanised rubber or for goods which are too soft to
be disintegrated to dust.
Generally speaking, the determination of sulphides (Method 6) and
of carbonates in the rubber itself is best circumvented by isolating the
mineral fillers as described below (Method 8), and carrying out these
determinations on the pulverulent material so obtained.
8. The Direct Isolation of Filling Materials.
(a) Frank and Marckwalcfs Method} — The rubber is comminuted
and submitted to acetone extraction. Of the dried residue i g. is placed
together with 30 c.c. of xylene in a wide test tube of thick glass with a
ground-in stopper. Four or six of these may be charged at once ; they
are set up in a metal stand and placed in an autoclave containing
xylene. There must be sufficient xylene in the autoclave to obviate
any risk of going to dryness ; it may with advantage be half filled.
The autoclave is closed and heated up in the course of an hour to a
pressure of 15 atmos. The pressure is then kept at 15-18 atmos. during
three or, to make sure, four hours. The autoclave is then allowed to
cool down, blown off, and opened. If the solid matter in the tubes has
settled and left the liquid clear, an equal volume of ether is added and
gently stirred in. If the liquid is turbid, 1-3 c.c. of absolute alcohol are
added, whereby a slight precipitation of rubber is brought about, and
the liquid is effectually cleared ; it is then diluted with ether as before.
The tubes are allowed to stand overnight. The solid matter is then
collected on a weighed filter and washed well with ether, which removes
1 Gummi-ZeiL, 1 908, 22, 134.
424 INDIA-RUBBER AND RUBBER GOODS
any precipitated rubber ; it is then dried and weighed. This solid
matter, which consists of inorganic fillers, carbon, fibres, and mechanical
impurities, should be a dry, impalpable powder ; lumps of rubber, if
present, are either removed by a suitable solvent or separated and
allowed for in the subsequent analytical operations. One portion is
taken for the determination of total sulphur. Another portion is
analysed as follows : — By warming with dilute, followed by concentrated,
hydrochloric acid, carbonates, sulphides, etc., are removed ; the residue
is re-weighed. The constituents soluble in acid may be determined in
the usual way. On igniting the insoluble residue, the loss gives the
carbon and other organic matter. The ignition-residue is dealt with
by the ordinary procedure of quantitative analysis. This separation
into acid-soluble, organic, and refractory constituents greatly facilitates
the interpretation of the anal\'tical data. Further portions of the
original material may be used for the determination of carbonic acid
and sulphide-sulphur.
It is to be noted that when red rubber goods containing vermilion
are to be dissolved by this method, the rubber and x}'lene must be
heated up in sealed tubes. If the tubes are open, mercury will escape
by volatilisation, and may cause serious damage to the autoclave.
(/^) F. Hiwichsen and ]\\ Manassc's Method} — The rubber is
brought into solution by heating at atmospheric pressure with
petroleum, a solvent originally proposed by Henriques.- i g. of the
acetone - extracted and dried material is placed in a lOO c.c. conical
flask, together with 25 c.c. of a petroleum fraction distilling between
230 and 260.' Frank and Marckwald^ suggest liquid paraffin of
sp. gr. 086. The flask is heated under a reflux condenser, by means
of an air-, paraffin-, or sand-bath, but not to ebullition of the solvent.
Some rubbers go into solution at 120-130", others require tempera-
tures of 180-200 ; fumes of white vapour are a sign of over-heating.
When, after an hour or two, no more undissolved rubber can be
observed, the flask is allowed to cool and the contents diluted with
petroleum spirit. The solid matter is separated, not by filtration,
but by the use of a centrifugal machine. After the flask has been
whirled for about half an hour at a speed of 1500 revolutions per
minute, the sediment will generally have settled so firmly that the
supernatant liquid can be simply poured off. Fresh petroleum spirit
is then added, boiled up with the solid matter, whirled and poured
off as before ; the operation is repeated once or twice. Finally, the
solid residue is dried at 105 and weighed. It is analysed as under
Method 8(«).
' C/ievi. Ziil., 1909, 33, 735 ; /. Soc. C/ieni. bid., 1909, 28, 843.
2 Cliem. Zeit., 1892, 16, 1624. •' Gummi-Zeit., 1909, 24, 213.
SUBSTITUTES
425
9. Extraction with Volatile Solvents.
The most common, though not the only, solvent currently employed
in rubber analysis is acetone. With a homogeneous solvent such as this
the best extractor to use is that of Zuntz, with a mixture, that of
Soxhlet ; modifications of both forms of apparatus have been designed
with special reference to rubber analysis (see p. 400). With solvents
of high boiling point (above 8o"-ioo°) it is
better to carry out the operation by simply
boiling under a reflux condenser rather than
with the aid of an extractor. The boiling-vessel
connected with the extractor may be either
a conical flask or the wide - m.outhed Soxhlet
flask. Several extractors may with advantage
be set up together on a stand such as that
shown in Fig. 55.
Pulverulent materials are placed in a filter-
paper thimble ; cuttings of sheet are rolled up
upon muslin, as described on p. 400. Extrac-
tion is continued for six to ten hours, and its
completion is gauged by taking a sample of
the solvent out of the extractor and evaporat-
ing. The liquid in the flask is then distilled
off and the residue dried and weighed.
ID. Determination of Substitutes.
As will be gathered from what was said
about substitutes on p. 411, these are deter-
mined by extraction with alcoholic potassium
hydroxide. About 5 g. of acetone-extracted material are boiled for four
hours under a reflux condenser with 25 c.c. of semi-normal alcoholic
potassium hydroxide. The liquid is poured off, the residue washed
out with boiling water until no alkaline reaction can be detected, and
then dried on a watch-glass or in a weighing bottle. The difference in
weight before and after extraction represents the saponifiable matter.
It is to be noted, however, that in this way something less than the
percentage of substitute originally incorporated will always be found,
because the previous extraction with acetone will have removed the
unvulcanised oily portion of the original substitute. On the other hand,
the difference in weight is itself liable to a plus error, owing to the
removal of some of the mineral matter (antimony sulphide, zinc oxide,
silica) by the alkaline liquors.
Fio. 55.
426
INDIA-RUBBER AND RUBBER GOODS
In the case of unvulcanised doughs the direct action of alcoholic
potassium hydroxide is inapplicable, since the material would be only
superficially attacked, and it is necessary to proceed as follows : —
5 g. of substance and 25 c.c. of benzene are warmed for an hour
under a reflux condenser on a water-bath and allowed to stand over-
night. By this time a thick solution will have been formed which
offers no resistance to the action of alcoholic alkali ; it is boiled for
four hours with 25 c.c. of semi-normal alcoholic potassium hydroxide
as above. Both the alcohol and benzene are then completely distilled
off, and the residue freed from substitute-soap, etc, by repeatedly
boiling out and kneading with hot water.
As an alternative to determining substitute by the loss of
weight of the rubber, the fatty acids of the substitute may be directly
isolated and weighed. For this purpose the alcoholic potassium
hydroxide solution is freed from solvent by evaporation, combined
with the aqueous washings, and acidified. The fatty acids are then
extracted with ether and weighed in the usual manner.
II. Resins Insoluble in Acetone.
A number of resins are in use as ebonite ingredients which cannot
be completely extracted by means of acetone, and are, indeed, very
resistant to organic solvents generally. C. O. Weber ^ proposes to deal
with these by an extraction with epichlorhydrin, following immediately
upon the acetone extraction. The following data as to solubility are
adduced by Weber : —
Acetone.
Epichlorhydrin.
Copal ....
Dammar ....
Mastic ....
Sandarac ....
Shellac ....
Partially soluble
>i
»)
Soluble
Insoluble
Soluble
11
Partially soluble
Soluble
12. Pitch and Bitumen.
A portion of these materials always goes into solution in the
acetone extraction. For detecting the presence of pitch, pyridine is a
useful solvent, but it attacks rubber ; for this and other reasons it
cannot be made use of with advantage for quantitative work. Generally
speaking, it is impossible to determine admixtures of this class with
any great accuracy. Sometimes ethyl acetate, following upon acetone,
^ TAe Chemistry of India Rubber, p. 260.
ANTIMONY AND MERCURY SULPHIDES 427
gives good results. In the absence of added lampblack, an indication
of the presence of coal-tar pitch, and an approximate estimation, is
afforded by the presence of pulverulent carbon in the rubber.
Carbon bisulphide has been proposed as a solvent by R. Becker.^
The acetone-extracted material is treated for one hour in a Zuntz
extractor with carbon bisulphide. Owing to its low boiling point, this
solvent is stated to take up no appreciable quantity of rubber, provided
the extraction be not unduly prolonged.
13. The Direct Determination of Antimony and Mercury Sulphides.
When it is desired to determine these pigments alone in a red
rubber or ebonite, it is best to destroy the rubber and other organic
matter by means of drastic reagents. This can be done by either of
the following methods'-: —
(a) Method of F. Frafik and K. Bij'kner? — Haifa gram of comminuted
rubber is put into a round-bottomed 100-150 c.c. flask together with
10 g. of ammonium persulphate, and 10 c.c. of fuming nitric acid are
added. These proportions, which have been worked out by experiment,
should be adhered to as far as possible. A vigorous reaction takes
place during a few minutes, whereupon the flask is heated on a sand-
bath. After fifteen to twenty minutes the evolution of gas will have
ceased. If now there remain particles of undecomposed organic matter,
2-3 g. of ammonium persulphate are gradually added during ten
minutes or so ; this quantity is certain to suffice. Any nitric acid
which may still be present is then boiled off; but excessive heating
should be avoided, since insoluble metallic compounds may thereby be
formed. The clear melt is allowed to cool until crystallisation sets in.
Before solidification has gone too far, 10 c.c. of hydrochloric acid (sp.
gr. I- 1 24) are added, and the solution is diluted with warm water.
The insoluble mineral matter is filtered off, the filtrate further diluted,
and the antimony and mercury are then precipitated by means of
sulphuretted hydrogen. In the ordinary way, the two sulphides, — in
case antimony and mercury are both present, — may be collected, washed
with carbon bisulphide, dried, and weighed together ; antimony is then
dissolved out with ammonium sulphide, and the residue is again treated
with carbon bisulphide, dried, and weighed. Should a greater degree
of accuracy be desired, the two metals must be separated by more
refined methods of quantitative analysis.
ih') Method of W. Schmitz} — In this method, which was primarily
1 Giimmi-Zeit., 1911, 25, 598.
■^ C/. also Rothe, Che77i. ZeiL, 1909, 33, 679.
' Chem. Zeit., 1910, 34, 49 ; J. Soc. Chem. Ind., 1910, 29, 224.
* Gummi-Zeit.^ 1911. 25, 1928 ; /. Soc. Chem. Ind., 1911, 30, 1223.
428 INDIA-RUBBER AND RUBBER GOODS
worked out for antimony alone, the organic matter is destroyed, as in
Kjeldahl's method for the estimation of nitrogen. From 2-4 g. of
comminuted rubber, together with 13-15 c.c. of concentrated sulphuric
acid for each gram, are placed in a long-necked, 300 c.c. flask ; a drop
of mercury weighing about o-i g. and a small piece of paraffin wax are
added, and the flask is heated on a sand-bath until the contents form
a homogeneous liquid and begin to lighten in colour. After cooling,
from 2-4 g. of potassium sulphate are introduced, and the heating is
continued to decolorisation. On adding water to the cooled liquid
most of the mercury is precipitated as a white powder. Tartaric acid
is then added and a gram or two of potassium metabisulphite (to
reduce the mercury) ; the liquid is copiously diluted, boiled till free
from sulphur dioxide, a little hydrochloric acid added, and then filtered.
The determination of the antimony ma\' be effected either gravimetri-
cally or volumetrically in the filtrate.
14. The Direct Determination of Rubber.
Man)' methods and modifications of methods for the determination
of rubber in vulcanised articles by the nitrosite or tetrabromide process
have been proposed. The two following methods are to be depended
upon so far as they go, but, at best, they yield only approximate results.
{a) P. Alexajider's Nitrosite Method} — Half a gram of comminuted
and acetone-extracted rubber is suspended in carbon tetrachloride, and
allowed to swell during some hours, or, better, overnight. It is then
treated with nitrous gases in the same manner, and with the same
apparatus, as for crude rubber (see above, p. 403). The nitrosite is
formed even more readily than from crude rubber. After standing
overnight in the liquid saturated with red gases, the fragments of
rubber will generally have been completely converted to a yellow
friable substance ; so long as residual cores of elastic substance can be
observed, the treatment with gas must be continued. The liquid is
then poured off, and the nitrosite is washed with the solvent and
roughly dried ; it is then dissolved in acetone, and the filtered solution
is concentrated. From this point onwards the procedure described on
p. 404 may be followed. Ether is added to precipitate the nitrosite.
Should there still be tarry matter or lampblack in suspension, a few
cubic centimetres of ether are first added to precipitate these impurities
without bringing down any nitrosite, and the solution is re-filtered and
treated with excess of ether. The whole liquid, including the solvents
and precipitate, is then evaporated, dried in a current of air or hydrogen,
and weighed. Finally, the sulphur contained in the nitrosite is deter-
1 Gummi-Zeil., 1907, 21, 653 ; /. Soc. Chem. IrtiL, 1907, 26, 538.
DIRECT DETERMINATION OF RUBBER 429
mined. The whole of the chemically combined sulphur is stated by
Alexander to remain in the nitrosite. The calculation to pure rubber
is effected by the relation : —
2-4 g. of sulphur-free nitrosite = i g. of rubber.
{b) S. Axelrod's Tetrabroinide Method} — i g. of rubber is brought into
solution by heating with loo c.c. of petroleum of high boiling point. This
will take two hours, or in some cases longer. Of the cooled liquid,
which must be well shaken, lo c.c, corresponding to o-i g. of material,
are taken up in a pipette, and 50 c.c. of Budde's bromine solution (see
p. 402) are added with constant agitation. After standing for three or
four hours the mixture is diluted with 100-150 c.c. of 96 per cent,
alcohol. The clear, supernatant liquid is poured off and the precipitate
is rinsed on to a filter and washed first with alcohol and carbon tetra-
chloride in equal parts, and lastly with alcohol alone.
The white precipitate of tetrabromide includes the mineral filling
materials of the rubber, and in addition contains a part of the sulphur
of vulcanisation. The proportion of sulphur thus retained varies with
the extent to which the rubber was vulcanised, but in no case amounts
to the total sulphur of vulcanisation.- With soft rubbers it can be
neglected without seriously affecting the determination of rubber ;
with rubbers of comparatively high vulcanisation it must be taken
into account. In order to allow for the mineral matter, the weighed
tetrabromide is incinerated with the addition of a drop or two of
sulphuric acid, as in sugar analysis ; by this means the errors intro-
duced by carbonates and bromides are to a large extent counteracted.
The net weight of tetrabromide finally obtained is multiplied by the
factor 0-314 to give pure rubber.
General Scheme of Analysis.
Special methods and individual determinations having been dealt
with in detail above, the course of analysis of rubber goods as a whole
may now be considered. The general principle followed is that, by means
of solvents or of purely chemical operations, the various constituents are
divided into groups, each of which receives further analytical treatment.
A clear view of the scheme or schemes of analysis based on this
principle is best given by means of Tables, four of which are appended.
Table I. illustrates an analytical procedure in accordance with the
more recent developments of rubber chemistry. It is applicable to all
classes of soft rubber goods, and also, except for the determination of
inorganic fillers, to ebonites.
Gummi-Zeit., 1907, 21, 1229 ; /. Soc. Ckcm. hid., 1907, 26, 1058.
2 W. A. Caspari, Le Caoutchouc et la Guttapercha, 191 1, 8, 5289.
430
INDIA-RUBBER AND RUBBER GOODS
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434 INDIA-RUBBER AND RUBBER GOODS
Table II. represents, with slight modifications, an older scheme for
the analysis of comparatively simple materials, due to C. O. Weber.'
It may be remarked that, according to the yet older scheme of Henriques,
the first operation is extraction with alcoholic potassium h)'droxide,
followed by extraction with acetone. This method, though not now
generally practised, has certain advantages in special cases, i\g:, for the
separation of paraffin wax, mineral oils, and certain resins.
Table III. is an expansion of Table II.- and applies to the more
complicated mixtures, such as goloshes, mechanicals, and goods of low
quality.
Table IV. is that given by Weber -"^ for the analysis of ebonites, with
the addition of treatment with alcoholic potassium hydroxide to dissolve
out substitutes. It is not often that substitutes as such are introduced
into ebonites, but substances of this nature are very commonly produced
in the ebonite in the course of vulcanisation. The inorganic filling
materials cannot be isolated, as in the case of soft rubbers, but must be
deduced from the composition of the ash and from the results of certain
operations conducted on the ebonite itself.
Notes and Comments on the System of Analysis in
Table I.
Group I. — The mode of extraction with acetone, and treatment of
the extract, have been described on p. 425. The residue must be com-
pletely dried before portions of it are weighed out for proceeding as
under (2) and (3). The extract can in many cases be returned as
" resin " or " acetone extract," any further analysis of it being dispensed
with ; as shown in column A, however, it may often be a very compli-
cated mixture. The separation of the ingredients can be effected, with
a moderate degree of accuracy, as follows : —
I. The extract is saponified and shaken out with petroleum spirit,
according to the method described in the Section on " Lubricants,"
this Volume, p. 89 ; most of the free sulphur remains as sulphide in
the alkaline solution. The petroleum spirit extract then contains
mineral oil, paraffin wax, decomposed rubber, the unsaponifiable
matter of resins, rosin oil, etc. These are dried and weighed in a
flat porcelain dish, the bulk of the solvent having previously been
distilled off. A few drops of concentrated sulphuric acid are then
added, and the dish is heated for some time on a water-bath. The
residue is mixed with a little fresh lime and animal charcoal, and
extracted with petroleum spirit. There will now be in solution only
' The Chemistry of India Rubber, p. 256. " Loc. cit., p. 255.
^ Loc. cii., p. 258.
GENERAL SCHEME OF ANALYSIS 435
mineral oil, vaseline, paraffin wax, and ceresin, and this extract is
again taken to dryness and weighed. A certain error due to loss
of material must obviously be expected. From the appearance and
consistency of the residue it will generally be possible to decide which
of the above substances it consists of If bitumen be present in the
rubber, it may contribute a little paraffin to this residue. The difference
between the total petroleum spirit extract and the purified residue
represents matter which is not indifferent to sulphuric acid, i.e., the un-
saponifiable matter of rubber and other resins, the acetone extract of
pitchy matter, etc. Any rosin (colophony) present in the rubber will
go into solution in the alkaline liquid, on saponification. The soap-
acids having been isolated, rosin is tested for by extracting with 60-70
per cent, alcohol, and submitting the extract to the Liebermann-
Storch colour - reaction for rosin oil (see "Oils, Fats, and Waxes,"
p. 130).
2, An alternative procedure for splitting up the acetone extract is
by means of alcohol. It is dealt with below (p. 438) in reference to
cable insulations.
Group 2. — A portion of the residue B is taken for the quantitative
determination of the substitutes, by the method described on page 425.
So much of the substitute as is insoluble in acetone is thus obtained in
solution, and its fatty acids can be isolated in the usual way. The fatty
acids of pure substitutes are completely soluble in 90 per cent, alcohol
at ordinary temperatures. They contain all, or nearly all, of the com-
bined sulphur of the substitute, which may be determined in them by
the nitrate-fusion method (see p. 419). This group further contains the
chlorine of white substitutes, and a considerable proportion of the
chlorine which is combined with rubber in cold-cured goods.
Residue D. — This contains all the rubber, all the sulphur of vulcan-
isation, some of the chlorine of vulcanisation, and all of the solid fillers,
except for what may have gone into solution {e.g. antimony) in alcoholic
potassium hydroxide. If it be desired to carry out a rubber determina-
tion by the nitrosite method, this is the material to use, because acetone-
soluble matter and substitutes — especially the latter — are apt to prove a
source of error in this method.
The remaining groups and operations call for no further explana-
tion, all necessary observations being included on pp. 426-429.
Interpretation and Statement of Analytical Results.
If a rubber analysis be conducted as described above, with the aim
of reconstructing the original mixing, it will be found that few of the
analytical results per se correspond directly to substances originally
4.3G
INDIA-RUBBER AND RUBBER GOODS
forming part of the mixing. The reasons for this are — firstl)', that
analysis can divide up the rubber only into chemical groups, and not
into raw materials ; and, secondly, that rubber mixings of any great
simplicity very seldom occur. Hence it may be regarded as sufficient
to state the group results as such, which is what C. O. Weber recom-
mended ; or, if further knowledge be desired, the groups themselves
must be subjected to further analysis. It is best, in the latter case, to
resolve the analx'tical results into groups according to the scheme of
Table I.
In this scheme it is especially column A and columns C and D of
Group 2 which may call for laborious analytical subdivision ; the
analysis, however, is much facilitated by previous experience. It would
be impossible to lay down general rules in small compass.
The subdivision of Group 3 is a comparatively straightforward
matter. It should be noted that the amount of rubber hydrocarbon in
the substance analysed is arrived at with a considerable degree of
accuracy, by difference, according to Group 3 ; in a general way, this is
quite as satisfactory as the direct determination of the rubber proper, if
not more so. To find the amount of crude (washed) rubber originally
incorporated, the rubber proper must be augmented by the rubber resin
present. The latter is comprised in column A ; to find its exact
amount may or may not be a simple matter, according to circum-
stances.
The direct determinations enumerated in Group 4 may be of
considerable value in elucidating the composition of a rubber. • In
regard to pitch and bitumen, it has already been stated that they are
not amenable to a direct determination of any precision.
The following scheme of statement, in which all percentages are
calculated upon the original material, may be found useful for analyses
of rubber goods : —
I.
Loss at 100°
.
... per cent,
2.
Acetone extract
.
... per cent.
Sulphur
Unsaponifiable matter
Saponifiablc matter .
... per cent.
... per cent.
... per cent.
3-
Substitute ....
• • •
... per cent.
4.
Sulphur
Chlorine
Mineral matter
The several constituents seriatim
... per cent.
... per cent.
... per cent.
... per cent.
5-
6.
7.
Insoluble organic matter .....
Sulphur of vulcanisation .....
Rubber proper (by difference or by direct determination)
... per cent.
... per cent.
... per cent.
100
CABLE INSULATIONS 437
The Examination of Cable Insulations, and Specifications
FOR THE SaME.I
No generally accepted standards of a chemical character for the
examination of rubber for cable insulations have been adopted in this
country. In Germany, the official Prussian Institute for the Testing
of Materials, in collaboration with a number of cable factories, has
recently proposed a series of analytical standards, qualitative and
quantitative, to be applied to the rubber coverings of standard electric
cables. The specifications, together with the analytical operations
involved, are as follows : —
Rubber for cable insulations is to be compounded thus : —
33-3 per cent, of rubber containing not more than 6 per cent, of
resin.
66-y per cent, of filling materials, including sulphur.
No organic filling material, except ceresin, or paraffin w^ax to a
maximum amount of 3 per cent, may be incorporated.
The specific gravity of the vulcanised rubber is to be at least 1-5.
The material to which tTie above rules are intended to apply is the
rubber insulation lying between wire and textile protection (tape,
braiding, etc.) in its final condition, i.e., after undergoing any changes
which vulcanisation in contact with impregnated fabrics may have
wrought in it.
The laboratory examination is to extend to the following points : —
1. Determination of specific gravity.
2. Qualitative tests for mineral oil, bitumen, etc.
3. Determination of acetone extract, in which are to be deter-
mined : —
a. Ceresin, or paraffin wax, and its content of sulphur.
b. Total sulphur.
4. Determination of filling materials.
5. Determination of matter soluble in semi - normal alcoholic
potassium hydroxide.
The insulation is to be rejected if it fails to come up to standard by
any one of the above chemical tests. Should the specific gravity be
less than 1-5, the chemical examination is to be proceeded with
notwithstandinsf,
t>'
Methods of Analysis to be employed.
Preparatioji of the Sample. — Not less than 30 g. of rubber stripped
from finished cables must be available for the tests. A length of cable
^ Cf. Elektrotech. Zeitsclu, 1909, 30, 1205.
438 INDIA-RUBBER AND RUBBER GOODS
which will furnish at least this quantity must therefore be supplied in
the first instance.
The rubber is comminuted by cutting into cubes of 0-5-1 mm. side
with a pair of scissors.
r. Specific Gravity. — The material must sink in a zinc chloride solu-
tion having a specific gravity of 1-49 at 15'.
2. Mineral Oil, Bitumen, etc. — On allowing the material to swell in
solvents such as xylene, carbon tetrachloride, pyridine, nitrobenzene,
the solution must show neither fluorescence nor dark coloration.
3. Extractiojt zvith Acetone. — Two portions each of 5 g. are extracted
with freshly distilled acetone for ten hours in a Soxhlet extractor pro-
tected from sunlight. The two extracts, each in its flask, are freed
from solvent by distillation and are dried to constant weight in an
oven at 100". One of the two extracts is dissolved by warming with
50 c.c. of absolute alcohol ; the solution is filtered, washed with 25 c.c.
of boiling absolute alcohol, and allowed to stand for an hour in a
freezing mixture at —4 to — 5 . The separated paraffin (with a little
sulphur) is filtered off and washed with 100 c.c. of alcohol (90 per cent,
by volume) similarly cooled. The filtrate is tested for paraffin by re-
cooling.
The contents of the filter are washed by means of alcohol, followed
by v/arm carbon bisulphide, into the original extraction-flask, where
they are freed from solvent, dried at 100", and weighed. This gives
the whole of the paraffin plus a little sulphur.
To determine the sulphur in the above, about 20 c.c. of concentrated
nitric acid (sp. gr. 1-48) are introduced into the flask and kept in gentle
ebullition for half an hour; 100 c.c. of water are added, and the cooled
solution is filtered. The filtrate is evaporated to dryness with a few
crystals of sodium chloride on the water-bath, and then again
evaporated with 5 c.c. of concentrated hydrochloric acid. The residue
is finally dissolved in 50-100 c.c. of water, and precipitated with barium
chloride as usual.
The contents of the second extraction flask are taken for the
determination of the total sulphur in the acetone extract. The
procedure is exactly as above.
Paraffin and sulphur being now known, the remainder on subtract-
ing from the total acetone extract may be regarded as rubber resin.
4. Filling Materials. — A weight of acetone-extracted rubber (dried at
5o''-6o°) corresponding to i g. of original material is placed in a weighed
100 c.c. conical flask with 20 c.c. of petroleum, boiling point 230^-260°
(or, if this fails, some other efficient solvent, e.g., liquid paraffin or
camphor oil), and heated under a reflux condenser until all the rubber
is dissolved. The cooled flask is nearly filled with petroleum spirit,
and the contents allowed to settle for twenty-four hours. A double-
CABLE INSULATIONS 439
bottomed Gooch crucible is prepared for filtration, dried, and weighed,
and the decanted liquid is poured through again and again till clear ;
the sediment is then added, and the whole is washed with hot benzene
until the filtrate is quite clear. After further washing with petroleum
spirit, alcohol, and ether, both the crucible and the conical flask are
dried at 105° and weighed.
In case a centrifugal machine is available, the filtration may be
replaced by repeated whirlings and decantations with fresh petroleum
spirit in the original flask; the latter is ultimately dried at 105° and
weighed.
By the above operations the total pulverulent filling materials,
including lampblack and fibre, are determined.
Filling materials, plus extracted sulphur, plus parafifin, taken
together, must not exceed 65-7 per cent. The remainder counts as
vulcanised rubber. To avoid the determination of the sulphur of
vulcanisation, its amount is assumed by convention to be i per cent.
upon the original material.
5. Constituents Soluble in NJ2 Alcoholic rotassiinn Hydroxide. — After
extraction with acetone, the rubber is dried at 5o°-6o°, transferred to a
100 c.c. conical flask, and boiled under a reflex condenser for four hours
with 50 c.c. of a semi-normal alcoholic solution of potassium hydroxide
upon a water-bath. The liquid is filtered and the residue is washed
with 100 C.C. of hot absolute alcohol followed by 50 c.c. of hot water.
The solution is evaporated to about 15 c.c, diluted with water to
100 c.c, and extracted with ether after acidification. The ethereal
extract is cautiously evaporated in a tared beaker, dried to constant
weight, and weighed.
As there is a certain small amount of matter soluble in alcoholic
potassium^ hydroxide even in pure rubber, the allowable limit in cable
insulations is taken as 0-5 per cent, calculated on the material itself.
Miscellaneous Notes on the Analysis of Rubber
AND OF Rubber Goods.
Coefficient of Vulcanisation is a term introduced by C. O. Weber
to express the extent to which a rubber has been vulcanised. It is
defined as the amount of rubber-combined sulphur per cent, of pure
rubber (not per cent, of rubber plus combined sulphur).
Analysis of Proofed Fabrics. — In order to determine the propor-
tion between rubber and fabric, the following method may be
employed : —
An area of 50 sq. cm. is weighed and boiled with cymene, or the
corresponding fraction of coal-tar naphtha. This solvent neither chars
440 INDIA-RUBBER AND RUBBER GOODS
the fabric nor decomposes any sizing which may be on it. When the
rubber has gone into solution, the fabric is washed with cymene and
then with alcohol, dried, and again weighed. It may then be further
examined for sizing, etc.
To ascertain the composition of the rubber spreading, the proofed
fabric may be dealt with as if it were solid rubber, by the ordinary
methods of rubber analysis.
Rubber Solutions. — A great variety of solutions and cements
containing rubber comes into trade for use in connection with tyres,
waterproof goods, footwear, etc. The solid matter of such compounds
is analysed in much the same way as ordinary manufactured rubber.
To determine the total solids, a weighed quantity of the compound is
dried in an oven to constant weight and re-weighed, the loss representing
volatile solvent. This solvent will generally be carbon bisulphide,
petroleum naphtha, or coal-tar hydrocarbons, or a mixture ; in order
to isolate and identify it, the method of R. Thai ^ may be followed. A
weighed quantity is kneaded in a porcelain basin with several portions
of 95 per cent, alcohol, which is poured into a measuring cylinder and
copiously diluted with saturated brine. After a time the rubber
solvents separate out as clear liquids ; their volume is read off, and by
taking the specific gravity their weight can also be determined. Boiling
points and other characteristic properties serve to identify the solvents.
Another simple way of separating solvents is to distil with steam ;
clear distillates which " break " readily without forming stable emulsions
are thus obtained, but it is often difficult to drive off the last portions
of solvent, except with an excessive amount of steam. Rubber solutfons
and cements are apt to contain foreign resins, gutta-percha, and balata.
Specific Gravity. — The determination of the specific gravity with
rubber and rubber goods is carried out by the usual methods. It
should be noted that rubber, even when finely divided, has a great
tendency to enclo.se air ; hence before weighing in a pyknometer, the
sample must be well boiled out. The specific gravity of rubbers lighter
than water is also best determined pyknometrically ; even though the
substance floats on the water, it can be taken in fragments large enough
not to obstruct the capillary of the pyknometer.
A simple and easy way of determining the specific gravity is by
flotation. The rubber is placed in a beaker of water, boiled out, and
allowed to cool. Either alcohol or some indifferent salt (a saturated
solution of zinc chloride may be used with advantage) is then added
until solution and rubber have the same specific gravity ; that of the
former is finally determined by any convenient method.
An apparatus based on this principle for determining specific gravity
has been devised by Minike.s.- It takes the form of a test tube
1 Chem, Zeit., 1898, 22, 737. '^ Gummi-Zeit., 1898, 12, 97.
EMPIRICAL TESTS 441
graduated in three sections ; the middle third is marked on the left
side with divisions 200- 1-45, counting upwards, whilst the upper third
is marked on the right side with divisions i- 50-1-00, counting down-
wards. For comparatively light articles, water is poured in to the
right-hand division i-oo, the sample introduced, and zinc chloride
solution (sp. gr. 2-00) added little by little, with constant shaking, until
the sample floats in the middle of the liquid ; the specific gravity is
then read off on the right-hand graduation. For heavier articles the
tube is charged up to the lowest mark, viz. 2-00, with zinc chloride
solution of sp. gr. 2-00, and water is added to equilibrium, the final
reading being taken on the left-hand side.
Microscopic Examination. — This mode of examination has come
more and more into vogue in recent times. The main obstacle has
always been the difficulty of obtaining suitable micro-sections ; a micro-
tome is indispensable, and freezing and other stiffening devices have
to be resorted to. It is now proposed to conduct the microscopic
examination by the aid of reflected light, which greatly simplifies the
examination. The thickness of the test-piece, under these conditions,
is of no importance ; all that is required is a smoothly cut upper
surface. Microscopes specially adapted for work by reflected light, with
incandescent gas or electric illumination, are supplied by the makers,
and are usually sent out with full directions for use.
D. EMPIRICAL TESTS APPLIED TO RUBBER GOODS.
There are numerous more or less cursory tests, both chemical and
physical, to which rubber goods may with advantage be subjected by
way of ascertaining whether they are likely to meet practical require-
ments. Such tests of course differ widely according to the class of
material concerned : to realise this it is only necessary to consider a
list of typical rubber articles, e.g.^ elastic thread, dolls, balls, steam-
packings, insulations, hose - piping, ebonite combs, accumulator cells,
etc. Whilst it would be impossible to enter into the more specialised
tests, some of the more important and generally applicable tests are
given below.
I. CHEMICAL TESTS.
I. Dilute Acids. — Specifications as to the resistance of rubber goods
to the action of dilute acids are frequently laid down. They are
especially significant in the case of packings and accumulator cells
or grids.
{a) Behaviour of Ebonite towards dilute Sulpliuric Acid. — The test may
be applied to whole pieces or (less commonly) to comminuted material
442 INDIA-RLBBER AND RUBBER GOODS
as follows: — 5 g. of plate or raspings are submerged in 25 c.c. of 20
per cent, sulphuric acid (sp. gr. 1-15), and kept at 50-70' in a covered
vessel for forty-eight hours. The ebonite is then washed well and dried
at 95-100'. The loss in weight should not exceed 4 per cent.
(/;) Resistance of Packhtgs to Acid. — A weighed ring or strip of
material suitable for the tensile test by one or other of the testing
machines referred to below (p. 445) is laid in 5 per cent, acetic acid, and
left to itself for seventy-two hours at the ordinary temperature. It is
then washed, dried, re-weighed, and subjected to the same tensile test
as the untreated material. A second sample is warmed with the same
acid to 6o°-70° during forty hours, and dealt with similarly. The test
is particularly valuable when its results can be compared with those
given by material of known quality. Other acids than acetic may also
be emplo}'cd, in proper dilution.
2. Alkalis.^ — The test is carried out precisely as that with acids.
The alkaline solution may afterwards be evaporated to a small volume,
acidified, and extracted with ether, the ethereal solution being then
evaporated. The fatty acids, if any, thus obtained afford information
as to oils or substitutes present in the rubber.
3. Alcoholic Alkali. — Extraction with alcoholic potash solution,
without previous acetone extraction, is frequently laid down in specifica-
tions. Resin, free sulphur, and substitute are thus extracted together.
The British Admiralty, which lays down a maximum loss of from 6 per
cent, upwards, according to the nature of the article, prescribes "boiling
for six hours in a finely-ground condition with a 6 per cent, solution
of alcoholic caustic potash."
4. Saline Solutions.'- — The material is subjected for a long time to
the action of a 10 per cent, solution of the salt. Tests with sea- water
also are sometimes prescribed.
5. Chlorine.^ — A compact piece of material is weighed and laid in
chlorine water ; the details of the test are the same as with acids.
6. Fatty and Mineral Oils. — A test-piece is immersed in oil and
kept for seventy-two hours at the ordinary temperature, or for forty
hours at 6o°-70 . The gain in weight is then determined and com-
parative tensile tests are made. A specification sometimes laid down for
cable insulations is that the gain in weight after four hours' treatment
with oil at 70° shall not exceed 3 per cent. Beside gain in weight,
increase of volume, which should also be as small as possible, may be
observed, e.g., by measuring the dimensions of test-pieces of rectangular
contour.
7. Resistance to Oxidation. — See below under 8 and 10.
' From the chapter on Rubber, by E. Herbst, in Post's Chemisch-Technische Analyse,
■ Ihid. 3 Ibid.
PHYSICAL AND MECHANICAL TESTS 443
II. PHYSICAL AND MECHANICAL TESTS.
8. Dry Heat Test. — The condition that rubber goods shall suffer
no loss in suppleness or elasticity under the action of tolerably high
temperatures is frequently insisted upon. The British Admiralty, for
instance, specifies for " Mechanicals " that they shall " endure a dry
heat-test of 270° F. (132° C.) for two hours without impairing their
quality." According to Lobry de Bruyn,^ the test is carried out by
placing 3 g. of material, cut into thin sheet, in an oven previously
brought to 135°, during two hours. After cooling, the rubber is
compared with untreated material, from which it should not differ
perceptibly.
9. Superheated Steam. — This, or a similar, test also occurs in
Admiralty specifications. According to Lobry de Bruyn, a piece of the
material is heated in a sealed tube, two-thirds filled with water, during
four hours to 170°; the rubber should then have undergone no
alteration.
10. Action of Light.- — A flat test-piece is fastened to a board, and
one half of it is protected by a sheet of thick cardboard. It is exposed
for a suitable period to direct sunlight. Rubbers sensitive to sunlight
have a more or less marked tendency to develop superficial cracks and
wrinkles under these conditions, owing to oxidation. The extent to
which the rubber has suffered may be gauged by comparing the
exposed with the unexposed half; over and above this, a standard
rubber should be exposed concurrently.
The following oxidation test independent of sunlight has been
proposed by VVolfenstein ^ and by C. O. Weber.* A sample is kept for
two days in 20 g. of acetone mixed with 60 c.c. of hydrogen peroxide
of 20 per cent, strength. After washing with a little acetone and water,
and drying, the surface of the sample is inspected. The gain in weight,
in comparison with a standard rubber, serves as a measure of the
tendency to oxidation.
11. Permeability. — The capacity of sheet rubber or proofed fabric
for retaining gases is of no small importance in aerial navigation.
Qualitative tests may be made by stretching the material over a drum
filled with hydrogen, coal-gas, air, or other gas under a slight plus
pressure ; the outer surface of the diaphragm having been painted with
soap solution, it is easy to observe if and where there are pinholes. To
make comparative quantitative tests, a drum covered and filled with gas
as above is weighed when freshly charged, and again after twenty-four
hours; from the change in buoyancy (assuming that a light gas,
^ From Post, Chemisch-technische Analyse, loc. cit. 2 /^/a'.
2 Ber., 1895, 28, 2665. * The Chemistry of India Rubber, p. 230.
444 INDIA-RUBBER AND RUBBER GOODS
preferably hydrogen, is taken), the permeability per unit of area and
per unit of time can be calculated.
12. Resistance to Pressure. — Compression tests may be, and
currentl)' are, carried out by a great variety of methods, mostly adapted
to special circumstances. In the elaborate series of mechanical tests
conducted by C. Heingerling and W. Pahl,^ sheets of rubber of about
I mm. thickness and 5 sq. cm. area were compressed for one minute
under a maximum load of 4900 kg., and the resulting deformations
were measured.
English railways prescribe compression tests for buffers, in which
the buffer is subjected by means of a h}-draulic press to loads of from
10-60 tons during specified periods ; the deformation is measured
immediatel)' upon releasing the pressure, and at intervals afterwards.
13. Percussion Test. — A cube of about i cm. is subjected to the
impact of a hammer-head of 2 kg. falling through 25 cm. The deforma-
tion undergone after, say, fifty blows have been delivered may be
measured, or percussion may be continued until cracks appear in the
rubber.
14. Insulation and Breakdown Voltage. — These highly important
tests are very extensively applied to cable insulations and other rubber
materials used in electrical engineering. They belong, not to the
analyst's, but to the electrician's province, and for details concerning
them treatises dealing with cables or electrotechnics generally should be
consulted.
15. Resiliency.'-' — A solid or hollow ball of rubber is dropped from a
given height on to a hard, even surface. Both the height of the first
rebound and the time taken to come to rest mav be measured, the
results being compared with those given by a standard rubber.
By another form of resiliency test, a steel ball is dropped on to a
thick plate of rubber and the rebound is measured.
16. Abrasion. — The general principle followed by machines designed
for abrasion tests consists in pressing the test-piece under known loads
against a rotating pulley or disc covered with emery-cloth or similar
material ; the abrasion undergone is compared with a standard. A
special variety of this test is that applied to tyres by way of simulating
road friction. In one patented machine the tyre is mounted on a
wheel and pressed against a rotating drum, the surface of which is
" paved " with rough concrete. The wheel is driven at high speed by
means of a motor, and causes the drum to rotate with it. The test may
be continued cither for definite periods of time or until rupture of the
tyre ensues.
17. Tensile Test. — This is on the whole the most valuable
1 Ver/i. Ver. Bef. GtwerhJI., 1891, p. 370.
^ From Post, Chevtisclu-technische Analyse^ loc. cit.
PHYSICAL AND MECHANICAL TESTS 445
mechanical test for defining the quality of a rubber. It is less empirical,
and represents a closer approach to fundamental reliability, than any
of the tests enumerated above, and its results can be expressed with
considerable quantitative precision. It must be understood, however,
that the science of the mechanical properties of rubber is as yet in a
very inchoate condition, not being nearly so far advanced as that of the
testing of metals, incomplete as that is. Results of tests are affected
very extensively according to laws which are not yet cleared up, by the
size and shape of the test-piece, the method of clamping, the rate of
extension, and other factors. Hence, on the one hand, comparable and
consistent quantitative data can only be obtained by using one definite
kind of machine and test-piece, and by carrying out the test with
rigorous uniformity. On the other hand, no generally accepted con-
ventions have been arrived at by which one specified method, as in
cement-testing, is adopted as standard. With these reservations, the
fact remains that comparative tensile tests are a very serviceable means
of differentiating one rubber from another, so far as mechanical pro-
perties are concerned.
The principal quantitative data afforded by the tensile test are: —
(i) breaking stress (usually expressed in kilograms per square centimetre),
(2) elongation at rupture (expressed as a percentage), and (3) modulus
of elasticity (Young's modulus). The latter is not a constant quantity
within limits, as in the case of steel, but must be stated with respect to
a given stress or elongation.
Numerous forms of testing machine have from time to time been
designed, and some of them have become current articles of commerce.
Within the limits imposed by the size, scope, and elaboration of the
machine, all those named below are capable of giving useful compara-
tive results. The two first are large, workmanlike constructions, and
can deal with loads of 100 kg. or over.
L. Schopper's ^ Machine is of the upright type, the power being
applied hydraulically, and stresses being measured by means of a
pendulum-lever working over a sextant (Fig. 56). This design, which
has long been in use in connection with the testing of paper and
fabrics, has been adapted to the exigencies of rubber largely by the
aid of the Royal Prussian Testing Institution. The test-pieces take
the shape of rings, which are stamped out of thick sheet with a
specially constructed press (Fig. 57); they are gripped by rollers, one
of which is kept in continuous rotation during the extension, whereby
the ring also is made to change its points of support continuously.
P. Breuil's^ Machme (Fig. 58) is a strong horizontal apparatus
^ Cf. Frank, Gummi-Zeit., 1908, 22, 6; Schidrowitz, India-Rubber Journal, March to May
1909 : Memmler and Schob, Mitt. L Matertalpriif, 1909, p. 4.
'^ Lt Caoutchouc et la Guttapercha, 1907, 4, 1061.
446
INDIA-RUBBER AND RUBBER GOODS
working with flat test-pieces held in grips of the ordinary vice pattern ;
power is applied by hand through a long screw and bevel-gear, and
stresses are read off on the dial of a spring balance. By the aid of
auxiliar)' appliances, the machine may also be used for tests by compres-
sion, by alternating stress, by abrasion, and at high or low temperatures.
^<
.^*!S=trv~
Fig. 56.
Fig. 57.
L. Delaloe's Machine is a small portable apparatus which was in
use for leather, fabrics, etc., before it was applied to rubber testiag.
The mechanical principle is the same as that of Breuil's machine.
A. Schivartz''^ Machine
embodies a new departure,
in that it is arranged to de-
termine, not the breaking
strength of the rubber, but
its behaviour under inter-
mediate strains and stresses.
It takes flat test-pieces of
slender dimensions ; stresses
and elongations are not
directly read off, but are con-
tinuously recorded graphic-
ally. Emphasis is more
especially laid on the " hy-
steresis-loops," registered on the diagram when a test-piece is stretched
to a point short of rupture, and then allowed to contract by virtue of
its own elasticity.
1 J. Insi. Eke. Eng., 1910, 44, 693.
Fio. 58.
GUTTA-PERCHA AND BALATA 447
Schopper's and BreuWs Machines are also fitted with accessory
gear, enabling stress-strain diagrams and hysteresis-loops to be
automatically recorded.
C. Beadle and H. P. Stevens' ^ UTachine measures the breaking
strength and elongation of ring-shaped test -pieces which are not
rotated. The test-rings are punched out of sheet as with the Schopper
machine, but are lighter and flatter. The disposition of the machine
is horizontal ; power is applied by water run from a tap into a
suspended bucket, and stresses are measured by weighing the bucket
and its contents.
i8. Bending Stress. — For ebonite, the tensile strength of which is
not so interesting as that of soft rubber, the most useful test is that by
bending. A bar or rod of ebonite is firmly clamped at one end in a
horizontal position, and weights are applied at the other end until
rupture ensues. The load and the angular displacement at rupture are
measured.
By the recently adopted specifications of the British Admiralty,^
the rod is not bent to rupture, but is loaded with a specified weight
and exposed to a temperature of 70" C. during two hours. At the end
of this time the point of support of the weight must not have sagged
more than a specified distance.
19. Washers for Bottle-stoppers may be subjected to the
following comparative test : — The washers are slipped on to stoppers
of the proper size, when they will be under slight strain, and exposed
for five days to direct, or for ten days to diffused sunlight. If after this
time a washer shows any cracks, wrinkles, indentation, or incipient
stickiness, it may be regarded as unfit for use.
Gutta-percha and Balata.
(a) Gutta-percha.
I. Gutta-percha is a gum which resembles india-rubber chemically,
but differs from it in mechanical consistency. It is coagulated from the
latex of a series of trees belonging to the family of Sapotacecs. The
old-established method of collecting gutta-percha involves the pre-
liminary felling of the tree ; latterly, however, much attention has been
given to replacing this ruinous procedure by methods of "milking" the
living tree. Gutta-percha trees are limited in their habitat to the
Malay Peninsula, Sumatra, Borneo, and the Philippines. In recent
times plants yielding gutta-percha have been discovered in the Soudan
and in German New Guinea.
Beside that which is derived from latex, a certain amount of gutta-
\J, Soc, Chem. Ind.y 1908, 28, nil. ^ India-Rubber Journal, 1913, 45, 1192.
448 INDIA-RUBBER AND RUBBER GOODS
percha comes into the market which is obtained from leaves and twigs,
either b>- extraction or by mechanical processes. This mode of pro-
duction has been more especially developed in the Dutch colonies.
The main points of difference between gutta-percha and india-
rubber are the following : — When heated to temperatures below 70",
gutta-percha becomes soft and plastic like wax. The cooled mass
retains any shape that may have been impressed on it. The elasticity
of gutta-percha is inconsiderable, and not to be compared with that of
rubber. On the other hand, gutta-percha has a much higher insulation
resistance than unvulcanised rubber.
The characteristic constituent of gutta-percha is a hydrocarbon, to
which the distinctive name "gutta" is sometimes applied. It is a
pol)-merised dimethyl-rj/f/(t7-octadiene (CjoHig),, isomeric with caoutchouc.
Whilst in its purely chemical relations gutta comports itself almost
exactly like caoutchouc, it differs notably in its behaviour towards
solvents.^ Gutta solutions arc far less viscid than rubber solutions, and,
unlike the latter, deposit pseudo-crystalline flakes on cooling, which
retain much solvent, but show no tendency to coalesce. Again, gutta
dissolves much less readily in ether than caoutchouc ; hence gutta
solutions can usually be precipitated by means of ether, which is not the
case with rubber solutions.
Gutta-percha resin has been an object of investigation from early
times, and has been empirically divided into two constituents, Albaiic
and Fluavil. It appears from the work of P. van Romburgh - that
gutta-percha resin consists, at any rate to a large extent, of esters
which on saponification yield cinnamic acid, and alcohols resembling
cholesterol.
Crude gutta-percha, as imported, contains moisture, dirt, gutta
proper, and oxygenated substances grouped under the heading of resin.
To render it fit for use industrial!}', it is washed like rubber between
rollers or in kneading machines. A further process of purification, so-
called "hardening," often applied to gutta-percha, consists in removing
the bulk of the resins by means of solvents.
2. TJie Examination of Gutta-percha. — This comprises the following
determinations : —
(i) Moisture.
(2) Ash.
(3) Mechanical impurities.
(4) Resin.
(5) Softening point.
(6) Electrical and mechanical tests.
(i) and (2), Moisture and As/i, are determined as in the case of
rubber.
1 C/. W. A. Caspari,/. Soc. Clum. Ind., 1905, 24, 1274. - Ber., 1904, 37, 344°-
GUTTA-PERCHA 449
(3) Determijiation of '' Dirt" — Owing to the difficulty of sampling
ordinary crude gutta-percha, there is not much to be gained by going
beyond the determination of mechanical impurities plus moisture in
the washing process. In order to determine dirt in washed or un-
washed gutta-percha on the laboratory scale, about i g. of material is
dissolved in chloroform, toluene, or the like ; the insoluble residue is
collected on a tared glass-wool ftlter, washed, dried, and weighed.
(4) Deter))iination of Resin. — The most important analytical datum
with regard to a gutta-percha is its resin-content, the determination of
which should never be omitted. The resin-contents — which vary within
wide limits — of many sorts of gutta-percha have been given by
E. Obach.^ To determine resin, the simplest method would be direct
extraction, as described for rubber under A (p. 400) ; but gutta-percha
does not lend itself well to this procedure, because by the melting of the
superficial layers access of solvent to the interior is rendered difficult or
impossible. The following method may be recommended-: — A gutta-
percha solution as obtained after the dirt has been separated (see
above), or an aliquot part of the same, is concentrated to a volume of
10-15 c.c. and poured, whilst^ still warm, into 75 c.c. of boiling acetone.
The flask is rinsed with a little of the same solvent. The mixture,
from which the gutta will have been instantly coagulated, is boiled for
ten minutes under a reflux condenser in order to redissolve any co-
precipitated resin. The clear liquid, containing all the resin, can then
be poured off; the firm coagulum of gutta hydrocarbon, on the other
hand, can be transferred to a tared glass-wool filter, washed, dried, and
weighed.
According to the method of Tromp de Haas, a gutta-percha solution
is evaporated in a wide-mouthed flask or conical beaker, so as to yield
a thin uniform film. The latter is repeatedly boiled out with acetone,
and the residual gutta hydrocarbon is dried and weighed without
transference.
A simple method for the determination of resin, which makes no
pretensions, however, to the highest accuracy, is described by E. Obach.
The principle consists in treating a weighed quantity of gutta-percha
with a definite volume of resin-solvent and eventually determining the
density of the solution so obtained. Obach's apparatus consists of two
upright stoppered cylinders communicating with one another by
narrower tubes. One cylinder is charged with gutta-percha, the other
with a measured volume of ether. The latter is driven by air-compres-
sion into contact with the gutta-percha, on which it is allowed to act for
some time. The solution is then sent back into the empty cylinder,
which contains a hydrometer and a thermometer, and its density is
1 Cantor Lectures on Gutta-percha, y. Soc. Arts, 1898.
'■* Frank and Marckwiild, Z. angevi. Che?n., 1902, 15, 40.
Ill 2 F
450 INDIA-RUBBER AND RUBBER GOODS
directly read off. In order to prevent loss of ether by evaporation, the
apparatus is mounted in a wooden box having panes of glass at the
front and back. Tables have been drawn up giving the relation
between the density of the solution and the percentage of resin in the
gutta-percha.
To determine the dirt and resin in gutta-percha, van Romburgh
proceeds as follows: — i g. of material is placed into a lOO c.c. measuring
flask with 8o c.c. of chloroform and heated for an hour on the water-
bath, with occasional shaking. When the whole has dissolved, the solu-
tion is cooled and made up to lOO c.c. It is then filtered through
cotton or glass wool (previously extracted), packed in a funnel, the stem
of which should be about 20 cm. long, with a 3 mm. bore ; the filtration
should be carried out expeditiously. The first 50 c.c. of clear filtrate
are poured into a weighed wide-mouthed conical flask of about 200 c.c.
capacity. The solvent is distilled off in such a way as to leave a
uniform film of substance ; this is dried, whilst standing in hot water, by
a current of carbon dioxide, allowed to cool, and weighed. The result
multiplied by two gives the weight of soluble matter, which, subtracted
from the original material, gives the mechanical impurities plus moisture.
The contents of the flask are next boiled out with three relays of
acetone. In boiling, and in pouring off the acetone, care must be taken
not to let the substance run together into a compact lump. The residue
is redissolved in chloroform and again evaporated to a film, and is then
again exhausted with boiling acetone. Penally, it is dried in carbon
dioxide and weighed. This gives the gutta proper, which is to be
multiplied by two as before.
(5) TJie Softening Point. — The following method is given by E. Obach.
Similarly shaped strips of the gutta-perchas to be compared, or of manu-
factured articles, are fastened to a frame, upon which they are held taut
by means of springs. The frame is immersed in a water-bath, which is
gradually heated up, and the apparatus is so arranged that an electric
bell is rung when each strip, by becoming soft, releases the spring to
which it is attached. When this takes place, the temperature of the
water is read. The time taken by a softened test-piece to regain its
hardness may also be determined.
(6) OtJicr Physical and Technical Tests are adapted as far as possible
to the conditions under which the material is to be used in practice. In
general, the methods are much the same as for rubber. Electrical
properties, such as insulation resistance, specific inductive capacity, and
breakdown voltage, arc of especial importance in the case of gutta-
percha, and call for careful measurement. Different sorts of gutta-
percha vary to a surprising extent in these respects. For details, the
monograph of Obach, referred to above, may be consulted.
BALATA 451
(6) Balata.
Balata is a substance very similar to gutta-percha. It is prepared
by coagulating the latex of certain trees belonging equally to the group
of SapotacccB^ notably Miuiusops Balata or Sapota JMiillcri. The chief
occurrences of Minmsops are in Jamaica, Trinidad, Venezuela, Guiana,
and the Amazon valley ; also to a minor extent in Africa.
The valuable constituent of balata is a hydrocarbon resembling
gutta-percha ; it is associated with a rather large proportion of resin.
The laboratory methods applicable to balata are precisely the same
as for gutta-percha. Unmixed balata is not employed for insulations,
owing to its comparatively low softening point. Balata is used in large
quantities in the manufacture of belting. It is also added to rubber
mixings which are required to vulcanise slowly, or in order to impart
increased resistance to wear to the vulcanised goods.
Literature.
Caspari, W. a. — India-Ruhber Laboratory Practice, 19 ! 4-
DiTMAR, R — Die Analyse des Kaiitschuks, 1909.
HiNRiCHSEN, F. W., and Memmler, K.—Dcr Kautschuk und seine Priifung^ 1910.
W'EBER, C. O. — The Chemistry of India Rubber, 1902.
VEGETAIiLE TANNING MATERIALS
liy the late Prof. C. COUNCLER, Ph.D., formerly Professor of Chemistry in the Royal
School of Forestry, Miinden. English translation revised by Prof. H. R.
Procter, M..Sc., late Director of the Leather Industries Laboratories, The
University, Leeds.
Preliminary Notes on the Estimation of Tannin.
Ill the quantitative estimation of tannin, pecuHar difficulties have
to be overcome. The majority of tanning substances are not yet
sufficiently well known to permit of their being separated and weighed
either in the free condition or in the form of characteristic compounds.
However, as commerce has demanded a quantitative determination of
" tanning value," numerous methods for the estimation of tannin have
been devised. None of them satisfy the claims of exact science, but
results which are adequate for practical purposes can be obtained if
"tannin" be defined as "that which tans," i.e., those organic substances
which are absorbed by hide from solution and which increase its dry
weight. In the majority of cases several different chemical compounds
are present, which are estimated under the general name of " Tannin "
or " Tanning substances." The Research Stations have, until now,
carried out the quantitative analysis either with the Loewenthal
method (improved by von Schroeder) or by means of a gravimetric
method. The tannin is brought into solution, and cither of the
following determinations is made before and after the removal of the
tannin by means of hide powder : —
A. The permanganate value in the cold (Loewenthal); or
B. The dry content (gravimetric methods) of a small quantity
of the solution. In both cases the tannin is calculated from the
difference.
Finally, the tannin content may be gauged roughly by ascertaining
the specific gravity in the cold of a portion of the aqueous solution
(hydrometer method) ; this process gives uncertain results, but
possesses a certain practical value.
It must also be noted that two chemists, using any one of these
methods, can only obtain concordant results if they work to the same
prescribed conditions. In 1883 most of the laboratories interested
4J2
ESTIMATION OF TANNIN 453
accepted a standard method of using the Loewenthal method, which
is frequently followed at the present day. A general gravimetric
method, which has been accepted by leather trades chemists, has been
laid down by the International Association of Leather Trades Chemists
(I.A.L.T.C.), first in 1897 in London, then in 1898 at Freiberg, which
also includes the estimation of moisture, and which is appended to this
Section.^
All such uniform methods working to pattern are empirical, and
will in course of time be improved ; the subjoined descriptions are
necessarily restricted to their present condition.
Hide Powder.
As a means of precipitation hide powder is of undoubted utility
in the best methods of tannin analysis. Even the Loewenthal-von
Schroeder method utilises the best possible hide powder; to a much
greater degree must this be the case with gravimetric processes. Hide
powder of the prescribed quality can be obtained from the German
Leather Industries Research Institute at Freiberg (Saxony).
The gravimetric method described in the fourth German edition of
this work, with which von Schroeder and the author obtained con-
cordant figures, cannot be generally adopted, as it demands too great
purity of the hide powder. Nowadays freshly chromed hide powder,
the preparation and chroming of which will be described later (p. 472),
is used both in the standard gravimetric method and in Procter and
Hirst's modification of the Loewenthal process. Unchromed hide
powder precipitates less " reducing non-tans'" than the chromed variet)-,
giving therefore more scientifically correct results ; yet the chromed
hide powder gives far more concordant results between different
analysts, while the gravimetric method only determines a small pro-
portion of the permanganate reducing non-tans.
A. Non-Gravimetric Methods of Tannin Analysis.
I. THE LOEWENTHAL METHOD, IMPROVED BY
VON SCHROEDER.
Principle. — The aqueous solution of the tannin is oxidised with a
permanganate solution of known activity, and from the amount of
permanganate solution required the amount of tannin is calculated.
Since the tannin solution generally also contains reducing substances
which are not tannins, the permanganate value {(X) of the original
solution is first obtained, and then {b) that of a similar volume of
^ C)^ H. R. Procter and H. G. Bennett, '' The Present Development of the Analysis of
Tanning Materiais,"_/'. Soc. Chem. Itid,, 1906, 25, 12C3 ; 1907, 26, 79.
454 VEGETABLE TANNING MATERIALS
solution which has been detannised by means of hide powder. The
difference 0?-/') gives the [)ermanganate value corresponding to the
original tannin present.
Reagents Required.
1. Pcrniangnnate Sohitiou. — lo g. of the purest potassium per-
manganate are dissolved in 6 litres of distilled water.
2. Indigo Solution. — 30 g. of solid sodium sulphindigotate are
brought in the air-dry condition into 3 litres of dilute sulphuric acid
(i : 5 by volume), 3 litres of distilled water are added and thoroughly
shaken up until complete solution is obtained ; then the whole is
filtered. In every titration 20 c.c. of this indigo solution are diluted
with \ of a litre of water; this will then reduce about 10-7 c.c. of the
permanganate solution.
3. Hide Powder. — Must be thoroughly white and quite woolly, and
must contain no materials extractable with cold water, which would
reduce permanganate solution. To make absolutely certain, it is
customary to do a blank experiment with 3 g. of hide powder.
4. The Purest Tannin. (See the Interpretation of the Titration,
P-455-)
The Method of Titration.
To the 4 litre of solution containing the indigo solution and tannin,
the permanganate is added from a stoppered Geissler burette.
(a) Drop Method. — According to Neubauer, the tap of the burette
is so turned that the permanganate solution drops slowly (i drop per
second) into the solution under titration ; whilst the addition is proceed-
ing the solution is vigorously stirred with a glass rod, until a bright
green colour is obtained. Then the tap is turned off and the
permanganate slowly added in single drops at considerable intervals,
and well stirred, and the procedure continued until the solution loses
its last trace of green and becomes pure yellow.
(6) The One Cubic Centimetre Method. — According to von
Schroeder, i c.c. of permanganate solution should be added at a time,
and the solution stirred vigorously for five to ten seconds. When the
solution has become light green in colour, only 2-3 drops are added at
a time, and this procedure continued until the liquid appears a pure
golden )'ellow.
The thick-walled beaker which contains the solution to be titrated
is placed on a white porcelain tile, in order that the end-point of the
reaction may be easily observed.
Over-titration should be strictly avoided, as titrating back is quite
METHOD OF ANALYSIS 455
impossible. In the carrying out of a tannin estimation, as good an
agreement must be obtained as in ordinary titrations.
The permanganate value is a function of several variables ; it is
especially dependent on the time, i.e. the rate at which the
permanganate is added to the indigo, and the rapidity of stirring.
If the "drop method" has been used to standardise a permanganate
solution, the same method must be used in performing an analysis with
that solution, using the figure thus obtained.
Interpretation of the Titer of the Permanganate Solution.
The purest possible commercial tannin is standardised in the
following manner : — 2 g., air-dried, are dissolved in i litre of distilled
water, and the permanganate value of 10 c.c. of this solution (with the
addition of indigo solution, whose reducing power is known, see above)
is obtained.
As ptire gallotannic acid cannot be obtained, Procter and Hirst ^
recommend the use of pure crystallised gallic acid, and have deter-
mined its value as compared with that of the gravimetric method for
most commercial tanning materials (see p. 459).
Further, the permanganate value after detannisation with hide
powder is obtained, 50 c.c. of tannin solution being used. This 50 c.c.
is placed in a tightly closed glass bottle with a glass stopper for
eighteen to twenty hours with 3 g. of hide powder, which has been
first soaked and then well squeezed out, shaking frequently ; it is then
filtered and 10 c.c. of the supernatant solution again titrated.
The permanganate value of the hide powder filtrate should not be
more than 10 per cent, of the total permanganate required. By drying
at 100° to constant weight, the moisture content can be estimated, from
which the total permanganate value (see p. 461) of the dry matter of
the tannin is calculated; the result so obtained, multiplied by 1-05,
gives the true titration value.
The reason for calculating the titration value to tannin instead of
to oxalic acid, etc., is that by this means the same effect due to the
rate of addition of the permanganate solution is obtained as with the
unknown tannin, which would not be the case with oxalic acid, oxalates,
ferrous sulphate, etc.
The Method of Tannin Analysis.
1. Preparation of the Tannin Solution.
{a) Extracts are dissolved in hot water, and filtered if required.
{b) Raw Tanning Materials (Barks, Fruits, Woods, etc.). — The
tannin is efficiently extracted by means of the Tharandt extraction
^ Collegium, 1909, p. 187.
456 VEGETABLE TANNING MATERIALS
apparatus (see below). The extracted liquor after cooling is made up
to I litre at room temperature, and if not absolutel>- clear, an aliquot
part is filtered.
The following quantities are used for an analysis : —
Per cent.
20 g. tanning material if containing probably . . . 5-10
10 g. tanning material if containing probably . . . 10-20
5 g. tanning material if containing higher percentage.
The materials richer in tannin (quebracho extract with 66 per
cent, and higher content, etc.) can be taken in smaller quantities,
eg- 3 g-
The sampling of tanning materials is somewhat difficult. The best
samples can be drawn from the well-ground and mixed material.
With bad sampling from the same parcel of oak-bark samples of 5
per cent, and 10 per cent, tannin content can be obtained. Of the
many publications on the most efficient means of sampling those of
F. Kathreincr are especially important (see p. 464 under C).
2. Titration of the Tannin Solution.
The tannin content of an aqueous solution is estimated by the
Loewenthal-von Schroeder method by titration of 10 c.c. of solution
(see p. 453) before and after treatment with hide powder (3 g. to 50 c.c.
solution, as in interpretation of the titration).
Thecontentof the tannin solution must be such that loc.c. of the same
reduce 4-10 c.c. of permanganate solution (neither more nor less, as
the tannin content is not absolutely proportional to the permanganate
value).
Extraction Apparatus.
Of the many forms of extraction apparatus that have been proposed
the Tharandt apparatus (bottle extractor) of von Schroeder and R.
Koch (Fig. 59) is one of the best. This consists of a wide - mouth
thick-walled 200 c.c. glass bottle, B, into which a layer of sea-sand is
poured to a depth of i inch, the latter having been previously
thoroughly extracted with hot hydrochloric acid and water, and then
well dried. The tanning material G to be extracted, already soaked
in water, is placed in the bottle B with more water, and the whole
closed with a tightly fitting double-bored rubber stopper.
Through one hole in the stopper passes a glass tube, H, bent twice
at right angles, with one end cut off sharply just below the stopper.
Through the other hole a similarly bent tube is passed, which reaches
EXTRACTION APPARATUS
457
right down to the bottom of the extraction vessel B, becoming wider at
the bottom (F). This latter tube is best made from a thistle funnel,
such as is used in the production of gases ; this is passed through the
hole in the stopper and then bent at right angles. The thistle top F
has a projecting curved edge, and is closed with a double layer of
gauze, so that while
fluids can pass through
from B to F, solid bodies
cannot. The lower end
of F reaches into the
sand. The extraction
apparatus, filled and
closed with the rubber
stopper carrying the
tube H and the funnel
F, is placed upon the
filter paper in the water-
bath E, which is sup-
ported by a tripod, E,
and the stopper pushed
tightly home. The tube
H is also filled with
water, and connected by
b through a rubber tube
to the pressure tube J,
which is filled with
water from the reservoir
A, the latter containing
at least 2 litres, a and
b are each fitted with a
double screw cock to
regulate or stop the flow
of water when required, though experts can dispense with the cock a.
The fall of water should be about 5 feet. The rubber tube at e is
also fitted with a double screw cock, which is now closed, and the
right angle delivery tube passed into the litre flask C.
This apparatus is suitable for the special estimation of easily and
difficultly soluble tans, without its being necessary to transfer the
material to any other apparatus. After the material has been subjected
to the water pressure for fifteen hours by opening the cocks at a
and b, while c is closed, it is only necessary to open the cock at c and
regulate the flow, to fill the litre vessel C to the mark in three hours.
This then contains the easily soluble tannin. The flow from c is then
stopped and a fresh litre flask placed in position, the water -bath
Fig. 59
458 VEGETABLE TANNING MATERIALS
heated to boiling by the flame D, and the difficultly soluble tannins
extracted.
If it be required to estimate the total tannin, the water-bath E is
heated from the beginning of the extraction. The first 5(X) c.c. are
extracted below 50', after which the temperature is rapidly raised to
boiling point. The Loewenthal method, as described, can be used on
solutions to solve many important commercial problems, and has rightly
been widely adopted.
Unfortunately, Loewenthal results are frequently confounded with
the gravimetric results. If the analysis of a pine bark gives 10 per
cent, of tannin by the Loewenthal method, this means that the tannin
extracted from this pine bark reduces as much permanganate (under
prescribed conditions) as if it contained 10 per cent, of tannin.
Nevertheless, the material may contain 17 per cent, gravimetrically, as
it has long been known that it was quite impossible to compare, for
example, sumac and pine bark by the Loewenthal process. It has
been thought that different samples of the same material might be
compared by means of the Loewenthal figures, but researches at
the Vienna Research Station^ have shown that even this view is
fallacious. In addition, the results of the Loewenthal and gravimetric
methods bear no constant relationship to one another, indeed the
differences between oak and pine vary greatly. The same facts have
been adduced by Zeumer.-
II. H. R. PROCTER AND S. HIRST'S MODIFICATION OF THE
LOEWENTHAL METHOD.^
This process has been largely adopted since it has been shown that
the comparison of the results of the Loewenthal and gravimetric
methods provides a good means of detecting the adulteration of tanning
extracts with sulphite cellulose liquors. Concentrated sulphite cellulose
liquor — often wrongly called " Fichtenholzextrakt " — only gives
extremely low percentages of tannin by the Loewenthal method, whilst,
as it contains a large quantity of substances absorbable by hide, the
results by the gravimetric method may be high.
Only a few small changes have been introduced to simplify the
process. Self-filling burettes are used for the permanganate and indigo
.solutions (see Fig. 60), and the titration is carried out in a large glass
jar of about i litre capacity, in which a small double-vaned stirrer,
turned by a water turbine or a motor, is suspended. For purposes of
comparison a similar beaker, containing a similar solution previously
1 G(?r/y<'r, 1887, p. 2. ^ Thara7tder/or5tliches Jahr buck, liZdy^t, I Jtl.
■' /. Soc. Chem. Ind., 1909, 28, 294.
PROCTER AND HIRST'S METHOD
459
titrated to the colour required, is placed alongside as a standard. The
titration can thus be carried out rapidly with absolutely concordant
results, and this method may be strongly recommended for the
systematic control of tan-
nery liquors. As tanning
materials are now almost
always bought and sold
on the analysis by the
Standard International
method, and as this in-
volves the removal of the
tannin with chromed hide
powder, the latter process
is also to be recommended
for use in this modifica-
tion of the Loewenthal
method. Formerly the
Loewenthal figures were
always calculated on pure
gallotannic acid, for which
Procter substitutes pure
recrystallised gallic acid,
which is easy to obtain, which is oxidised in the same way as tannin,
and I g. of which reduces the same amount of permanganate as 1-34 g.
of the purest gallotannic acid.
Solutions Required.
1. Pure air-dried gallic acid, o-i g. freshly dissolved in 100 c.c.
of water.
2. Purest indigo carmine, 5 g. per litre, plus 50 g. concentrated
sulphuric acid ; 25 c.c. indigo solution are taken for every titration.
I g. "indigo pure," B.A.S.F., dissolved in 25 c.c. concentrated sulphuric
acid, diluted to i litre, and mixed with another 25 c.c. of sulphuric acid,
can also be used. These two solutions keep well ; 25 c.c. of either are
oxidised by 25-30 c.c. of permanganate, in default of which a larger
or smaller quantity of indigo solution must be taken.
3. Permanganate solution, 0-5 g. per litre. This is prepared by
the suitable dilution of a 5-0 g. per litre solution immediately before
use, as very dilute solutions do not keep well.
Fio. GO.
The Method of Titration.
The tannin solution (liquor) must be so diluted that 5 c.c. of the
same do not reduce more than two-thirds of the quantity of
460 VEGETABLE TANNING MATERIALS
permanganate reduced by the original 25 c.c. of indigo solution ; the
contents of a 50 c.c. burette are therefore sufficient for a complete
titration. The stirring must be uniform, the addition of permanganate
also uniform and at such a rate that the drops can be counted, until the
colour of the solution becomes )'ello\vish-green. The permanganate is
then slowly added, drop by drop, until the pure yellow colour
is obtained. To ensure uniformity of work, the titration should be
carried out in a fixed time. The titration is effected more easily by
good artificial light behind matt glass than by daylight, as the dis-
appearance of the last trace of green is more accurately observed ;
but every analysis must be carried out under the same rigid condi-
tions, as otherwise the end-point can not be uniform. (See p. 472,
Standard Gravimetric Method ; section 7, " Detannisation.")
Tanning matter is calculated from the difference between the
permanganate required for the original and for the detannised liquor;
as dissolved salts and traces of hide substance have no appreciable
influence on the titration, the detannisation can be carried out more
easily than in the gravimetric method. The hide powder is only
chromed, squeezed, weighed, and the necessary water added (see
p. 472), the washing of the powder after chroming being unnecessary;
and when 20 g. of water have been added with the hide powder to a
100 c.c. solution, 6 c.c. of the detannised solution are calculated as
5 c.c.
Still simpler in use are Paessler's " weakly chromed " hide powder,^
or Kopecky's freshly air-dried shavings of chrome leather.- About
7 g. of the dry hide powder and some kaolin are added to 100 c.c. of
the diluted liquor, well mixed by hand-shaking, and then shaken for
ten to fifteen minutes in a machine. The moisture content of such a
quantity of hide powder is at the most i g., and can only produce
a maximum error of i per cent, of the total tannin in the diluted
solution, which, as the analysis is only for the purposes of comparison,
and as the error is constant, can be neglected. The detannised solu-
tion is filtered through filter paper until it is clear, and two separate
quantities of 5 c.c. are titrated in the presence of 25 c.c. of indigo
solution. If the work is being systematically carried out, the extent
of dilution for any particular solution will be known, otherwise a
preliminary trial on the undetannised liquor must be made, and in this
case it is better, at first, to dilute too much rather than too little.
The final result must, in this case, be divided by the number of cubic
centimetres of the original liquor which have been taken per litre, and
multiplied by looo.
It is unnecessary to dilute with distilled water, since equally accurate
^ Supplied by the Deutscher \'ersuchsanstalt fiir Lcier Industrie, Freiberg, Saxony.
2 Collegium, 1907, p. 105.
PROCTER AND HIRST'S METHOD 461
results can be obtained in practice with ordinary tap-water. It is a
doubtful point whether the liquor should be filtered before dilution,
after dilution, or not at all. In the last case the difficultly soluble
" reds," e.g. those of quebracho, or the catechin of gambler, are dissolved
in considerable quantities on dilution, and are estimated as tannin,
which cannot be entirely regarded as an error as, to a certain extent,
they are utilised in tanning, if the liquors are exhausted. It is un-
necessary for the purposes of detannisation to filter the liquor, but is
advisable that that part of the diluted solution which is to be titrated
directly should be passed through a good quantitative filter paper.
The Method of Analysis.
The systematic carrying out of the work is so arranged that the
liquors to be tested are brought first thing in the morning to the
laboratory and there sufficiently diluted. lOO c.c. of each of the diluted
liquors are each transferred to a shaking-bottle, the necessary hide
powder and kaolin added, and shaken by hand until well mixed.
Simultaneously a quantity of each of the diluted liquors is filtered to
remove any suspended matter. The shaking-bottles are then placed in
the shaking-machine for the requisite fifteen minutes, and the contents
afterwards filtered, whilst the titration of the other detannised solutions
is proceeded with.
For this latter purpose, lOO c.c. of the 5 g. per litre of permanganate
solution are diluted to i litre, care being taken to shake up sufficiently
to ensure uniform mixing. Then {a) two separate quantities of indigo
solution (25 c.c.) are titrated alone, and {b) the titrations repeated with
the addition of 5 c.c, of freshly prepared gallic acid solution (o-i g. to
100 c.c.) to each. The sum of the differences between {a) and {b) gives
the permanganate value of o-oi g. of gallic acid, which with the same
analyst and careful work practically remains the same from day to day
and need hardly be repeated every day. In the same way, 5 c.c, of the
diluted liquors and then 5 c.c. of the detannised liquors are titrated in
duplicate, to eliminate possible errors, and the sum of the two results
taken. If the figure for the detannised liquor be subtracted from that
of the original diluted liquor, the value of the 25 c.c. of indigo solution
in permanganate goes out on both sides, and the permanganate value
of the tannin contained in 10 c.c. of the diluted liquor is obtained.
The following proportion is thus found : — Permanganate required by
gallic acid is to permanganate required by liquor as i g. gallic acid
per litre is to the number of grams of tannin in i litre of liquor,
calculated as gallic acid. If instead of i g. per litre of gallic acid the
weight of the tannin corresponding to i g. of gallic acid is substituted,
the tannin content of the diluted liquor is obtained directly in grams
463
VEGETABLE TANNING MATERIALS
per litre, from which, by multiplication by the dilution factor, the
content of the original liquor may be calculated. Taking 1-34 instead
of i-o, the content calculated as gallotannic acid is obtained. From
about thirty analysis it has been found that the ratio of the gallic
acid percentage to the gravimetric percentage is, on the average,
I-0-I-76. The following Table gives the mean numbers for the most
important tanning materials determined by several analyses.
The numbers of the second series are reciprocals of the first,
I
A"
therefore in each case B
Table 40.
Tannin Equivalents of Gallic Acid (Procter and Hirst).
A. Tanniu, equivalent to 1 g. of gallic acid.
B. Gallic acid value
of 1 g. of the
respective tannin.
Chestnut wood and extract .
Oak wood ,,
Myrobalans „
Mimosa extract, Quebracho and ex-
tract, average ....
Larch bark .....
Hemlock bark ....
Hemlock extract ....
Pine bark * .
1-65
1-89
1-73
1-69
1-96
1-97
2-28
2-53
0-604
0-527
0-577
0-592
0-509
0-501
0-437
0-395
Mean of four fir wood tannins
2-18
0-460
Valonia extract
Valonia
Sumac ....
Oak bark
Mimosa bark
Mangrove bark
Cube gambier
1-80
1-58
1-53
1-47
1-71
1-88
1-46
1-78
0-553
0-632
0-650
0-680
0-583
0-529
0-682
0-559
Gallotanic acid ....
1-34
0-742
Sulphite cellulose liquors, "j I.
wrongly called " Fichten- -II. .
holz" extract . . Jill..
7-75
11-11
7-3
0-129
0-090
0-137
Average of I. to III.
8-72
0-119
♦ Pine bark tannin gives widely differing figures. See p. 458.
If it be desired to maintain a systematic control of the liquors of
a particular tannery or of a definite tanning material, this can be
obtained by combining the Loewenthal method with the Standard
gravimetric method (see p. 464), dependent on the difference between
ESTIMATION OF MOISTURE 463
" total solubles " and " non-tans." The content found by the gravi-
metric method in grams per litre, divided by the gallic acid value found
by the Loewenthal method, gives the required factor, i.e. the weight of
tanning matter which corresponds to i g. of gallic acid.
The use of the Loewenthal method on liquors has the advantage
ovfer gravimetric analysis not only in greater rapidity, but probably
also in greater accuracy on weak liquors, as it requires no definite
concentration. The figures given by Procter and Hirst show an excel-
lent agreement. This method is also preferable for the examination
of "spent" materials, as weak liquors can be analysed as accurately
as strong ones, the precaution being taken to use lo c.c. or more in
every titration. Care must be taken to use sufficient water to exhaust
the materials.
The gallic acid values of the different tannins are just as recognisable
and constant as the iodine or saponification values of fats, and can be
used as characteristic differences. An "oakwood extract," for example,
with a gallic acid value of over o-6 will really in all probability be a
chestnut wood extract. Above all, however, the extremely low gallic
acid value of concentrated sulphite cellulose liquors is of manifest
importance.
III. APPENDIX.
1. Estimation of Moisture. — From 2-3 g. of tanning material are
dried at ioo°-iio'' or, preferably, at 9S°-ioo'' in vacuo, to constant
weight, and the percentage of moisture calculated from the loss.
As tanning materials possess a varying proportion of moisture,
according to the season of the year, the humidity of the atmosphere,
etc., the moisture estimation belongs essentially to the analysis of the
tanning materials. In order to compare the results of two analysts on
the same material, the tannin figures must be reduced to the same
water content. The percentage of tannin calculated on a hundred
parts of the water-free material (dry weight) has often little value for
technical purposes. Many analysts calculate the percentage of tannin
to a " mean water content." According to the researches of von
Schroeder,^ the values of this latter for various tannins are as follows : —
Sumac, 12 per cent.; Oak-bark, 13 per cent.; Pine-bark, Mimosa-bark,
Valonia, and Quebracho-wood, 14-5 per cent; Algarobilla and Dividivi,
13-5 per cent. ; Rove, 15 per cent. ; Galls, 16-5 per cent. ; etc.
These calculated values are so important for the tanner that stress
must be laid on the fact that they are only approximate. It is, there-
fore best that figures for the moisture content, as found, should always
be given.
2. Estimation of Sugary Matters. — The tannin in the solution to be
1 Gerber Zeit., 1888, No. 61.
464 VEGETABLE TANNING MATERIALS
examined is precipitated with lead acetate, the lead removed with
potassium or sodium sulphate, the sugary matters estimated in the
filtrate as described in the Section on " Alcohol, Potable Spirits and
Liqueurs " (p. 739), and calculated as grape sugar.
B. The most recent Standard Gravimetric Method of
Tannin Analysis, according to the Regulations
framed at the conferences of the international
Association of Leather Trades Chemists.
(First, London, 1897 ; ninth, Brussels, 1908 ; tenth, Paris, 1910.)
Note. — These regulations have been for the greater part taken
verbatim from the reports of the conferences. Additions have only
been made where a word of explanation has seemed necessary. They
are commercially the universal standard in England, and largely so on
the Continent and in America, though some continental chemists still
use the older " filter-method " with Paessler's "lightly-chromed " powder,
which gives somewhat higher results ; in America the standard method
of the A.L.C.A. differs in some unimportant particulars.
\. RESOLUTIONS OF PREVIOUS CONFERENCES STILL IN FORCE.
I. Sampling the Bulk.
With fluid extracts at least 5 per cent, of the barrels must be
chosen, so that the numbers lie as far apart as possible in the series.
The two upper hoops and the lid are then removed from each of these,
and the contents thoroughly stirred up with a stirrer (best made of a
strong wooden rod, with a circular perforated disc at the end), care
being taken to remove all deposit adhering to the sides and bottom,
and to mix in thoroughly. All samples must be drawn in the presence
of a responsible person.
With Gambler and Non-fluid Extracts, the sample is drawn from
not less than 5 per cent, of the blocks, and in such a manner that seven
samples are taken from each block by means of a tube-punch which
completely perforates the latter. Kathreiner made such an instrument
out of brass, exactly like a cork-borer, about 36 cm. long and 3 cm. in
diameters ; the mass from the tube is forced out with a wooden plunger
into a flask or mortar made of heavy brass or wood, and well mixed. ^
Solid Extracts. — 5 per cent, of the bulk sample is drawn, a sufficient
quantity being taken from the exterior and interior parts to give the
requisite mean sample, and then broken up into small size. In the two
' For methods and exact description, see Proi-ier and Parker, I.A.L.T.C. First Conference,
London, 1897, p, 122 ; /. ^oc. Chem. Ind., 1898, 17, 6.
INTERNATIONAL xMETHOD OF ANALYSIS 465
last cases the sample must be mixed rapidly, and at once placed in an
air-tight box, sealed, and labelled.
With Valonia, Algarobilla, and all Other Tanning Materials which
contain dust or fibres, the sample must be taken as follows: — The
contents of at least 5 per cent, of the sacks are tipped on to a clean,
smooth floor so that they spread themselves over one another. From
several places in this heap samples are drawn perpendicular to and
reaching through to the floor, and these well mixed. Where this cannot
be done the sample must be taken from the mean of a sufficiently
large number of sacks. Whilst it is to be recommended that valonia
and most other materials should be sent for analysis in a ground
condition, it must be emphasised that dividivi and algarobilla should be
unground.
With uncut bark, and with other tanning materials in bundles, at
least 3 per cent, are sampled by cutting a section from the middle with
a saw or sharp axe. Good mixing and packing is also essential in this
case.
Samples which are to be submitted to more than one chemist must
be drawn as a single sample, well mixed, and the necessary divisions
made (not less than three), which are at once packed, sealed, and
labelled.
2. Preparation of the Sample for Analysis.
Fluid Extracts must again be thoroughly mixed before weighing
(the weighing should be carried out as quick as possible to avoid loss
of moisture). Especial care must be taken that the sediment which is
frequently deposited on the bottom of the sample bottle should be
uniformly mixed in with the rest. J. Paessler^ proceeds as follows in
order to avoid loss of moisture in accurate weighings : — A stoppered
weighing bottle or flask is first carefully weighed on an accurate
balance, and then again on a rough balance, weighing to o-i g. The
required weight is then placed in the scale, and the extract poured
quickly into the glass. This is then closed and weighed again on the
accurate balance. This process is accurate, but with practice no error
arises from weighing in the ordinary way. Thick extracts, which
cannot be mixed otherwise, may be warmed to 50° and stirred, but
must be cooled quickly before weighing. If this method has been
used it must be mentioned in the analytical report.
Solid Extracts must be coarsely powdered and thoroughly mixed.
Pasty Extracts must be rapidly mixed in a mortar, and the
necessary quantity weighed out as rapidly as possible, to avoid loss of
moisture.
1 Collegium^ 1904, P- 83 ; J. Soc. C/iem. Ind., 1904, 23, 458.
Ill 2 G
466 VEGETABLE TANNING MATERIALS
If Extracts be partly Dry and partly Moist, so that none of the
above methods can be applied, the sample must be weighed out and
dried at ordinar)- temperatures until it can be powdered. Then it is
again weighed, and the loss in weight calculated as moisture, and added
to that subsequently found by drying at ioo\
In cases, such as gambler, where it is impossible to mix the
constituents of the sample thoroughly by grinding, it is permitted to
dissolve the whole or a large proportion of the same in a small quantit}'
of hot water, and after thorough mixing, to weigh out a portion of the
strong solution for analysis.
With barks and other solid tanning materials the whole sample, or
not less than 250 g., must be ground so fine that it will pass through a
sieve of four strands per centimetre or sixteen perforations per square
centimetre. If materials, like many barks or dividivi, contain fibrous
portions which cannot be ground so fine, the ground sample must be
passed through a sieve ; the part remaining on the sieve and that
passed through are weighed separately, and the necessary quantities by
weight of each then united for analysis.
3. Preparation of the Infusion.
The strength of the tannin solution shall be such that 100 c.c. of
the same contain 0-35-0-45 g. of tanning matters.
The quantity of extract weighed out must be prescribed, so that in
the event of different chemists having the same materials to analyse,
they may work with solutions of the same concentration, subject to the
same intrinsic errors. Thus, generally speaking, with : —
Solid extracts, quantities within the limits . . • 5-7 S-
Pasty extracts of over i-2 sp. gr. within the limits , . 9-12 g.
Fluid extracts of over !• 15 sp. gr, within the limits . . 12-18 g.
Fluid extracts of under 1-15 sp. gr. within the limits . . 18-20 g,
must be taken. The above rules provide for and must ensure that
100 c.c. of the infusion contains 0-35-0-45 g. of tanning matters.
For barks and other raw vegetable tanning materials Paessler
recommends the following figures in order to obtain the requisite
concentration : — Algarobilla, 9 g. ; Canaigre, 18 g. ; Dividivi, 9 g. ; Oak-
bark, 36 g.; Oak-wood, 50 g.; Pine-bark, 32 g.; Garouille, i6g. ; Hemlock-
bark, 32 g.; Chestnut-wood, 45 g. ; Galls, I2g. ; Mimosa, I2g. ; Mangrove,
10 g. ; Myrobalans, 12 g.; Quebracho, 22 g. ; Rove and other Galls
generally, 12 g, ; Sumac, 16 g.; Valonia, 14 g. (Trillo, 10 g.) ; Willow-
bark, 36 g. ; Spent materials, 50 g.
SOLUTION OF EXTRACTS
467
Solution of Extracts.
A sufficient quantity is weighed into a covered basin or beaker,
and from thence completely washed with boiling water into a litre
flask. The litre flask is then filled to the mark with hot water ; if all
the extract is not yet dissolved, the flask is placed for a few minutes on
a boiling water-bath. After thoroughly shaking, the flask is rapidly
cooled to 17-5° (but not lower) in cold running water, or by other means,
filled to the mark, thoroughly mixed, and at once filtered, the latter
process being repeated until the filtrate is absolutely clear. The
filtration may be performed with Schleicher and Schuell's extra hard
filter paper. No. 605, diameter 17
cm. ; but, if possible, the Berkefeld
filter candle, introduced into tannin
analysis by Parker and Payne, should
be employed.
Whilst filter paper absorbs appre-
ciable quantities of tannin from
aqueous solution, the Berkefeld filter
candle does not. The latter can be
bought in various sizes, but those of
II cm. long by 3 cm. diameter are
most suitable. To free them from
iron compounds and other impurities
which would act upon the tannin
solution, the candles are boiled
with 10 per cent, hydrochloric acid,
thoroughly washed out, at first with
water containing hydrochloric acid.
o
D
Fig. 62.
Fig. 61,
then with pure water, and finally completely dried. The filter candles
are cylindrical, closed and rounded at one end, open at the other,
with a cylindrical cavity down the centre. After they have been
cleaned and dried, the open end of each is sealed tightly with shellac
and a rubber stopper, through which passes a glass tube, which pro-
jects a few millimetres into the cavity (Fig. 62) ; the glass tube is then
fitted into the stem of the funnel (see Fig. 61) by means of another
rubber stopper.
The whole is then fitted to a filter flask, which is connected to a
suction pump by means of pressure tubing. The solution can now be
468 VEGETABLE TANNING MATERIALS
filtered ; it is poured into the funnel and the flask strongly evacuated
(up to 40 mm.), when the pressure tubing is tightly closed by means of
a screw-cock, to avoid loss by continued evaporation. In about a
quarter of an hour, three-quarters to a half of the original litre of
solution can be filtered. The first 250 to 300 c.c. are rejected, then
about 500 c.c. are filtered, and quantities measured off for anal}-sis. As
the vacuum diminishes during filtration the loss by evaporation is lower
than in the earlier methods ; the funnel may be covered with a glass
plate to further reduce it. Strong solutions of quebracho extract
usually filter very slowl)', but the rate of filtration can be materially
increased by brushing the candle with a stiff brush (toothbrush), which
has been washed previously in a special portion of the solution.^ At
the end of the filtration the candles are removed from their funnels and
washed under the tap with the stiff brush described above. They are
then replaced in the funnels, and at least i litre of distilled water drawn
through ; after drying, the candles are again ready for use. The more
recent method is to use candles 1 1 cm. x 3 cm., and to fasten them by
means of an elastic band into a funnel-like continuation of the delivery
tube.- If candles which have previously been used for unsulphited
extracts are to be used for sulphited ones, they should be previously
washed with a sodium sulphite solution and then with water, to remove
phlobaphenes.
Extraction of Solid Tanning Materials (Barks, etc.).
A sufficient quantity is weighed out so as to provide a solution of
the prescribed strength {i.e. 0-35-0-45 g. of tanning matters per 100 c.c).
Not less than 500 c.c. of the extract must be obtained below 50°, after
which the temperature is rapidly raised to 100°. The extraction is
allowed to continue until the amount extracted is exactly i litre, and
should occupy at least three hours.
The Koch extractor (bottle-extractor, see p. 456) may be used ; the
standard flask into which the solution flows should not be cooled
during extraction.
Besides this extractor, the " syphon extractor," the so-called " beaker
method " of Procter,^ is much used by English chemists. The material
to be extracted is placed in a beaker of a capacity suitable for the bulk
of material to be extracted, in a water-bath. Close to the bottom of
this beaker a thistle funnel is suspended, the wider end of which is
covered with gauze. This is then covered with a 2 cm. layer of purified
sea-sand, above which is placed the tanning material.
The tube is bent twice at right angles, thus forming a syphon, the
^ Parker and Payne, Collegium, 1904, p. 261 ; /. Soc. Chem. fnd., 1904, 23, 648.
2 Collegium, 1905, p. 55. ^ /. Soc. Chem. Ind., 1892, II, 331.
SOLID TANNING MATERIALS 469
longer outer end of which is further lengthened with a glass tube.
This is fastened with a short piece of rubber tubing, to which is fitted
a screw-cock, for regulating the flow. The tanning material is then
covered with water, and allowed to soak overnight or for some hours.
The water-bath is then heated, and the syphon started by careful
suction ; 500 c.c. should come over before the temperature rises above
50°,^ and then the latter is rapidly raised to 100°. The extraction is
continued until the extract amounts to i litre, the whole process taking
at least three hours. If, in special cases, the extraction by Koch's or
Procter's method is incomplete with i litre, the second extract must be
examined separately and reported as " difficultly soluble matters."
Note. — The analysis report should include : —
1. Tanning substances absorbed by hide.
2. Soluble non-tans,
3. Insolubles.
4. Moisture.
The results of any further analysis which has been made must be
reported separately from the above.
Only those extracts containing less that 2 per cent, insolubles may
be described as "cold soluble."
II. MOST RECENT RESOLUTIONS OF THE INTERNATIONAL
CONFERENCES AT BRUSSELS (1908) AND PARIS (1910).
The Brussels Conference decided that the following "general
directions," sections i to 4, should represent the recommendations of
the International Commission on Tannin Analysis, but that the
members of the I.A.L.T.C. must be also bound by sections 5 to 8.
General Directions.-
Section i. — The solution for analysis must contain between 3-5 and
4-5 g. of tanning matter per litre, and solid materials must be extracted
so that the greater part of the tannin is removed at a temperature
not exceeding 50°, but if the Teas extractor (a metallic Soxhlet
apparatus much used in America) be used, the first portion of the
extract shall be removed from the influence of heat as soon as
possible.
Section 2. — The Total Solubles must be determined by the evapora-
tion of a measured quantity of the solution previously filtered till
^ (f the extraction is carried out from the commencement with water at 100°, the
maximum quantity of tannin is not dissolved ; part is destroyed, part is fixed by the extracted
material (Fiebing, Palmer and Hughes, Parker and Procter). In the examination of spent
materials, where it appears impossible to obtain the prescribed concentration under the rules of
the I.A.L.T.C, it is permitted to concentrate in vacuo to the required strength.
2 Collegium, 1908, p. 333.
470 VEGETABLE TANNING MATERIALS
optically clear both by reflected and transmitted light ; that is, a bright
object, such as an electric light filament, must be distinctly visible through
at least 5 c.c. thickness and a layer i cm. deep in a beaker placed in a
good light on black glass, or black glazed paper must appear dark and
free from opalescence when viewed from above. Any necessary mode
of filtration may be employed, but if such filtration causes any
appreciable loss when applied to a clear solution, a correction must
be determined and applied, as described in section 6. Filtration
shall take place between the temperature of 15' and 20'. Evaporation
to dryness shall take place between 98-5 and 100 in shallow, flat-
bottomed basins, which shall afterwards be dried until constant at the
same temperature, and allowed to cool before weighing for not less
than twenty minutes in air-tight desiccators over dry calcium chloride.
Section 3. — TJie Total Solids must be determined by drying a
weighed portion of the material, or a measured portion of its uniform
turbid solution, at a temperature between 98'- 5 and lOO' in shallow
flat-bottomed basins, which shall afterwards be dried till constant at
the same temperature, and cooled before weighing for not less than
twenty minutes in an air-tight desiccator over dry calcium chloride,
"Moisture" is the difference between 100 and the percentage of
"total solids"; and "insolubies" the difference between the "total
solids" and "total solubles."
Section 4. — Non-tannins. The solution must be detannised by
shaking with chromed hide powder till no turbidity or opalescence
can be produced in a clear solution by salted gelatin. The chromed
powder must be added in one quantity equal to 6o-6-5 g. of dry
hide per 100 c.c. of tanning solution, and must contain not less than 0-2
and not more than i per cent, of chromium reckoned on the dry weight,
and must be so washed that in a blank experiment with distilled water
not more than 5 mg. of solid residue shall be left on evaporation of
100 c.c. All water contained in the powder should be determined and
allowed for as water of dilution.^
THE FOLLOWING PARAGRAPHS GIVE THE DETAILED OFFICIAL
METHOD OF CARRYING OUT THE ANALYSIS ADOPTED BY
THE INTERNATIONAL ASSOCIATION OF LEATHER TRADES
CHEMISTS WHICH IS OBLIGATORY ON ALL MEMBERS.
Section 5. — Preparation of the Infusion. Such a quantity of material
shall be employed as will give a solution containing as nearly as
possible 4 g. of tanning matter per litre, and not less than 3-5 and not
' Anyone following sections 1-4 will be in very fair agreement with the I.A.L.T.C. method.
The reason for these "general directions" is to bring the .American and I.A.L.T.C. methods
into general accord (Procter).
GENERAL DIRECTIONS 471
more than 4-5 g. Liquid extracts shall be weighed in a basin or
beaker and washed with boiling distilled water into a litre flask, filled
to the mark with boiling water, and well mixed and rapidl)' cooled to
17^'S ; after which it shall be accurately made up to the mark, again
well mixed, and at once filtered. Sumac and myrobalans extracts
should be dissolved at a lower temperature.
Solid extracts shall be dissolved by stirring in a beaker with
successive quantities of boiling water, the dissolved portions being
poured into a litre flask, and the undissolved being allowed to settle
and treated with further portions of boiling water. After the whole of
the soluble matter is dissolved the solution is treated similarly to that
of a liquid extract.
Solid tanning materials must be sufficiently finely ground to pass
through a sieve of sixteen perforations per square centimetre (five wires
per centimetre), and then extracted in a Koch (p. 456) or Procter
(p. 468) apparatus with 500 c.c. of water at a temperature not exceeding
50°, and the extraction continued with boiling water till the filtrate
amounts to I litre. It is advisable to allow the material to soak for
some hours before commencing the percolation, which should occupy
not less than three hours, so as to extract the maximum of tannin.
Any soluble matter remaining in the material must be neglected, or
reported separately as " difficultly soluble" substances. The volume
of liquid in the flask must, after cooling, be accurately made up to
I litre.
Section 6. — Filtration. The infusion shall be filtered, repeatedly if
necessary, till optically clear both by reflected and transmitted light
(see sec. 2). With the Berkefeld filter candle or with Schleicher
and Schuell's 590 filter paper no correction for absorption is required, if
a sufficient quantity (250-300 c.c.) is rejected before withdrawing the
necessary quantities for evaporation ; the solution may be filtered
repeatedly in order to obtain a clear filtrate. If other methods
of filtration are employed, the necessary average correction must
be determined in the following way : — About 500 c.c. of the same or a
similar tanning solution are filtered perfectly clear, and after thorough
mixing 50 c.c. are evaporated, in order to estimate "total soluble"
No. I. A further portion is now filtered in exactly the manner for
which the correction is to be determined (the time of contact and the
volume rejected being kept as constant as possible). 50 c.c. of this
filtrate are evaporated, to determine "total soluble" No. 2. The
difference between Nos. i and 2 is the desired correction, which must be
added to the weight of the total solubles found in analysis. An
alternative method of determining the correction factor, which is quite
as accurate and frequently more convenient, consists in filtering a
portion of the tanning solution through a Berkefeld candle until
472 VEGETABLE TANNING MATERIALS
it is optically clear, which can generally be accomplished by rejecting
300-400 c.c. and returning the remaining filtrate repeatedly; simultan-
eously, 50 c.c. of the clear filtrate obtained by the method for which
correction is required are evaporated. The difference between the
weights of the residues is the required correction.
Note. — At least five determinations must be carried out in deter-
mining a mean correction. It will be found that this correction is
approximately constant for all materials, and using S. and S. 605 filter
paper, rejecting 150 c.c, the correction is about 5 mg. per 50 c.c. ; or if
2 g. of kaolin have been used, 7-5 mg. per 50 c.c. The kaolin must
have been carefully washed previously with 75 c.c. of the same liquor,
allowing to stand for fifteen minutes, and then pouring off. Paper 605
has a special absorption affinity for a yellow colouring matter, which is
frequentl)' found in sulphited extracts.
Section 7. — Detannisation. Hide powder shall be of a woolly
(fibrous) texture, thoroughly de-limed, preferably with hydrochloric
acid, and shall not require more than 5 c.c. or less than 2-5 c.c. of A710
sodium or potassium hydroxide to produce a permanent pink with
phenolphthalein on 6-5 g. of the dry powder suspended in water. If
the acidity does not fall within these limits, it must be corrected by
soaking the powder before chroming for twenty minutes in ten to twelve
times its weight of water to which the requisite calculated quantity of
standard alkali or acid has been added. The hide powder must not
swell in chroming to such an extent as to render difficult the necessary
squeezing to 70-75 per cent, of water, and must be sufficiently free
from soluble organic matter to render it possible in the ordinary
washing to reduce the total solubles in a blank experiment with distilled
water below 5 mg. per 100 c,c. The powder when sent out from the
makers shall not contain more than 14 per cent, of moisture, and shall
be sent out in air-tight tins.
The detannisation must be carried out in the following manner: —
The moisture of the air-dry powder is determined, and the quantity
equivalent to 6-5 g. actual dry hide powder is calculated, which will be
practically constant if the hide powder be kept in an air-tight vessel.
The requisite quantity of powder for the number of analyses to be
performed is weighed out and soaked in about ten times its weight of
distilled water. Very woolly powders require rather more than ten
times their weight. For each 100 g. of dry powder 2 g. of crystallised
chromic chloride (CrCl.{ + 6H.,0) (Kahlbaum) are dissolved in water
and made basic with o-8 g. of sodium carbonate, which is best
accomplished by adding 11-25 c.c. of a normal solution, thus making
the salt correspond to the formula, Cr.,Cl3(OH)3. This solution is
added to the powder, and the whole churned slowly for one hour. In
laboratories where many such anal)'ses are carried out, it is more
GENERAL DIRECTIONS 473
convenient to employ a lO per cent stock solution, made by dissolving
lOO g. of the chromic chloride in a little distilled water in a litre flask,
and very slowly adding a solution of 30 g. of anhydrous sodium
carbonate, with constant stirring, finally making up to the mark with
distilled water, and mixing well. Of this solution 20 c.c. are used for
100 g. of dry hide powder, or 1-3 c.c. for 6-5 g.
After soaking for one hour the powder is squeezed in clean linen
to free it as far as possible from the chroming solution, then washed
and squeezed repeatedly with distilled water until the addition of i
drop of 10 per cent, potassium chromate solution and 4 drops of A710
silver nitrate solution to 50 c.c. of the filtrate produces a brick-red
colour. Four to five squeezings are usually sufficient. Thus the 50
c.c. of filtrate cannot contain more than 0001 g. sodium chloride.
The water content of the powder is then reduced by pressure to
70-75 per cent., and the whole weighed. The quantity Q containing
6-5 g. dry powder is thus found, weighed out, and added immediately
to 100 c.c. of the unfiltered tannin infusion, along with 26-5— Q c.c.
of distilled water. The whole is then shaken for a quarter of
an hour in a stoppered rotating bottle, making not less than sixty
revolutions a minute. (It- can also be shaken by hand or any other
suitable means.) After shaking, the powder is pressed at once in
clean linen, and the solution filtered through a folded filter paper
sufficiently large to contain the whole filtrate, returning it till clear ;
60 c c. of the filtrate are then evaporated and calculated as 50 c.c, or
the residue of 50 c.c. is multiplied by i-2. The non-tannin filtrate
must give no opalescence with i drop of a solution containing i per
cent, of gelatin and 10 per cent, of sodium chloride.
I g. of kaolin, free from all soluble matter, must be used either by
mixing it with the hide powder in the shaking-bottle, or with the liquid
before filtration.
Section 8. — The analysis of used liquors and spent tans must be
carried out by the same methods as those used for fresh materials, the
liquors or infusions being diluted, or concentrated by boiling in vacuo,
or in a vessel so closed as to restrict the access of air, until the tanning
matter is, if possible, between 3-5 and 4-5 g. per litre, but in no case
beyond a concentration of 10 g. per litre of total solids, and the weight
of hide powder used shall not be varied from 6-5 g.
The result shall be reported as shown by the direct estimation, but
it is desirable that in addition efforts shall be made by determination
of acids in the original solution and in the non-tannin residues to
ascertain the amount of lactic and other non-volatile acids absorbed by
the hide powder, and hence returned as "tanning matters." In the
case of tans, it must be clearly stated in the report whether the calcula-
tion is on the sample with moisture as received, or upon some arbitrarily
474 VEGETABLE TANNING MATERIALS
assumed percentage of water ; and in that of liquors, whether the
percentage given refers to weight or to grams per loo c.c. ; and in both
cases the specific gravity shall be reported.
Section 9. — All evaporation shall be rapidly conducted at the
temperature of steam in shallow, flat-bottomed basins of not less than
6-5 cm. in diameter, to apparent dryness ; and shall be subsequently
dried between 98^^-5 and 100^ in a water or steam oven until of constant
weight, and shall afterwards be cooled in small air-tight desiccators
over dry calcium chloride for at least twenty minutes, and then weighed
rapidly. Not more than two basins shall be placed in one desiccator,
and the basins must not be wiped after removal from the desiccator.
All analyses sent out by members or associates of the I.A.L.T.C.
should be made in exact accordance with the preceding regulations,
and described as " Analysed according to the official method of the
I.A.L.T.C"; but if for any cause another method must be adopted,
the exact method used and the reasons for its employment must be
distinctly stated, such descriptions as "old official method" being
prohibited. Any copy or copies of reports of analysis, whether furnished
by the analyst or his client or agent, shall contain the entire matter,
both written and printed, of the original report.
All analyses reported must be the average result of duplicate
determinations, which must agree, in the case of liquid extracts, within
0-6 per cent., and of solid extracts, within 1-5 per cent., or the analysis
shall be repeated till such agreement is obtained, and it must be clearly
stated on the report that the results are the mean of such corresponding
determinations.
Literature.
Paessler, J. — Die Untersuchungsmethoden der pflanzlichen Gerbmaterialten, 1906.
Procter, H. R. — Leather Industries Laboratory Book of Analytical and Experi-
mental Methods, 2nd edition, 1908.
Procter, H. R. — Leather Chemists'' Pocket Book, 191 2.
Trotm.'\N, S. R. — Leather Trades Chemistry, 1908.
LEATHER
By Prof. J. Paessler, Ph.D., Director of the Research Station for the Leather
Industry, Freiberg, Saxony. English translation revised by Prof. H. R.
Procter, M.Sc, late Director of the Leather Industries Laboratories,
The University, Leeds.
The subject matter of this section comprises the examination of the
requisites and accessories of leather manufacture, in so far as they are
not dealt with in other sections, the methods of control employed in the
various processes concerned in the industry, and the methods of
examining the finished product, leather.
I. Accessories to the Processes Prior to Tanning.
Water.i — For the purposes of tanning this should be as free as
possible from the carbonates of the alkaline earths, which cause loss in
the extraction of tannin and must be regarded as of the greatest
importance, owing to their action on the ultimate weight and quality
of the finished leather. In this respect, however, their importance has
been greatly exaggerated, though their influence has not yet been
sufficiently mvestigated. The temperature of the water certainly
plays a far more important part than these dissolved mineral matters.
Generally speaking, it may be said that a water containing little
dissolved mineral matter is more suitable for tanning than one rich in
the same ; and further, that for the purposes of sole-leather tanning, it
is desirable to have a water of constant low temperature, while for
upper leather one with not too low a temperature is to be preferred.
Doubtless also the presence in the water of living organic matter, such
as bacteria and yeasts, and of unorganised ferments, the so-called
" enzymes," has a determining influence on the quality of the leather;
but on this point little or no research has been carried out.
Extremely hard water also acts deleteriously during the preliminary
treatment of hides and skins, in which the removal of hair is accom-
plished by liming or the use of sodium sulphide. Calcium carbonate is
precipitated through the hairs on to the grain, and is difficult to remove
in the subsequent deliming processes. These " water blasts " are
1 Cf. F. Simand, Gerber, 1 889, 15, 205.
475
47G LEATHER
particularly fatal to finer leathers which are to be dyed, and especially
to glace leather ; the damage is observable in the undyed leather as
rough dull patches, and in the dj-ed leather as lighter areas on which
the colour has taken irregularly.
It is difficult to use waters containing much organic matter in the
tannery, as they are generally rich in putrefactive organisms ; if, in the
absence of any other supply, such waters must be used, great care must
be taken, especially during the washing and soaking processes. The
danger lies in the fact that the putrefactive organisms may settle upon
the hide and attack it, and they are especially injurious to the grain.
These defects are observable in the finished article in the marking or
breaking of the grain, pock marks, pin holes, weak grain, etc.
Depilatories. — The following processes are used for unhairing : —
" Sweating," i.e., a carefully controlled putrefactive process, in which the
ammonia liberated probably acts as the depilatory ; " Liming," by
laying or suspending in a milk of lime; or "Lime paste," painted on
the flesh side. To strengthen the action of the lime liquor or paste, it
is frequently mixed with sodium sulphide, calcium sulphydrate, or
realgar (arsenic sulphide).
{a) Caustic Lime. — For this purpose a lime as rich as possible in
CaO, but containing little magnesia, alumina, or silicates, should be
used. For the estimation of the content of lime, see Vol. I., p. 4S3.
{b) Sodium Sulphide. — The commercial crystallised salt, Na.2S +
9H.,0 (32-5 per cent. Na.3S and 67-5 per cent, water), has a colour
varying from wine-yellow to dark brown or green ; most commercial
varieties are but little adulterated, though particles of carbon, sodiiim
sulphate, and thiosulphate are often present. Anhydrous varieties are
now, however, being sold which are generally less pure. The content of
sodium sulphide is determined by titration with an Njio ammoniacal
zinc sulphate solution, using cobalt paper or a lead salt as indicator
(spotting method) ; or, according to Simand, by titration of the solution
with Njz hydrochloric acid in the presence of phenolphthalein until the
red colour is permanently discharged. In this last case exactly half the
sodium which unites with the sulphur to form sodium sulphide is
estimated (Na.3S+ H.20 = NaHS + NaOH). If methyl-red, or orange,
or Congo red is used as indicator, the whole of the base is estimated.
A further alternative method is to titrate the sodium sulphide solution,
first directly, and then after precipitation with zinc sulphate, with an
iodine solution of known strength; the difference of iodine solution
required for the two titrations is calculated to sodium sulphide from the
equation, Na2S-+-l2 = 2NaI-f S.^ {Cf. also Vol. I., p. 437.)
{c) Calcium sulphide, Calcium sulphydrate. — These substances usually
1 J. Paessler, "Die Untersuchung der Schwefelnatriums." Cf. also F. Jean, Ann. Chun,
anal., 1897, 2, 34I ; /. Soc. Chem. Ind., 1897, 16, IO41.
DELIMIxNG AND SWELLING MATERL^LS 477
come into commerce as waste- or by-products of the Le Blanc soda
process, as, for example, " calcin," the so-called "liming compound."
The reactive principle of this material is a polysulphide, the method of
estimation of which is given in Vol. I., p. 437.
id) Arsetiic sulphide compounds : Yellow Arsenic {Orpiinenf), Red
Arsenic {Realgar). — These arsenic sulphide compounds are generally
mixtures of red and yellow arsenic. J. von Schroeder and W. Schmitz-
Dumont^ have shown that the activity of these compounds depends on
their double decomposition with lime to form calcium sulphydrate, and
the active principle is therefore sulphur. The estimation of the value
of arsenic sulphide compounds consequently comprises simply a deter-
mination of the sulphur, which can be carried out by any of the well-
known methods, such as oxidation with fuming nitric acid and
precipitation with barium sulphate. {Cf. Vol. I., p. 281.)
It is to be borne in mind, however, that it is only the sulphur that
is liberated as sulphuretted hydrogen by acids which acts directly on
the hide. (Procter.)
Deliming, Swelling, and Bating Materials.
To remove the lime from the hide and to prepare it for tanning
proper, as, for example, by swelling the pelt (the name given to the
unhaired hide ready for tanning) if intended for sole leather, inorganic
acids (sulphuric and hydrochloric) and organic acids (formic, acetic,
butyric, and lactic) are used, as well as so-called " bates," of which the
action is bacterial and fermentative, made with bran, dung, and similar
materials, and artificial bates (" Erodin " of Popp and Becker, " Oropon "
of Roehm, " Purgatol " of Eberle), depending on bacterial or enzyme
action.
The amount of acid available for deliming and swelling is deter-
mined by titration, and should be as free as possible from iron
compounds. In lactic acid, which is usually sold in 40 per cent,
solution, but more recently in 70 per cent, the amount of anhydride
which is always present must be taken into consideration.
This is estimated in the following manner: — 10 g. of the acid are
diluted with distilled water to 500 c.c. 50 c.c. of this solution are
poured into a porcelain basin and titrated with iV/2 alkali in the
presence of phenolphthalein to a permanent pink ; then, according to
the strength of the acid examined, 1-3 c.c. of N/2 alkali in excess are
added, boiled for a short time, and, after cooling, titrated back with N/2
acid until the red colour disappears. Besson - states that if the alkaline
solution be warmed or boiled a higher result is obtained, owing to the
action on other substances, and recommends that after the addition of
1 Dingl.polyi.J.^ 1896, 30O, 161 ; /. Soc. Chem. Ind., 1896, 15, 549.
2 Collegium^ 1910, p. 73 ; J. Soc. Chem. Ind., 1910, 29, 440.
478 LEATHER
the alkali the solution should be allowed to stand for ten minutes at
room temperature. From the total quantity of alkali added minus the
amount of acid required to titrate back, the " total lactic acid " (lactic
acid and anh\dride) can be calculated. From the amount of alkali
required for the first titration, the amount of " free lactic acid " (lactic
and anhydride) can be calculated.
These values are only accurate if the commercial lactic acid contains
no other free acids. As lactic acid is always produced by the action of
sulphuric acid on calcium lactate, a qualitative test for free sulphuric
acid is necessary, for which Eberhard recommends the following
procedure : — i part of the lactic acid is well shaken up with 5 parts
of 95 per cent, alcohol in a test tube. After standing for a quarter of
an hour 5-10 c.c. are filtered off, and to the clear solution a few drops
of calcium chloride solution, acidified with hydrochloric acid, are added.
In the presence of free sulphuric acid a turbidity soon appears. For
the quantitative estimation the total sulphuric acid (a), and the sulphuric
acid found in the residue on incinerating (d), and lastly, that present as
ammonium sulphate, must be determined. From the difference between
that estimated under (a) and that estimated under (d) and (c), the
amount of free sulphuric acid is found.
For the purposes of the tanner, lactic acid should be free from
hydrochloric and oxalic acids. The distillate should therefore give no
chlorine reaction, and no turbidity with calcium chloride solution.
The raw materials of the bran, dung, and artificial bates do not
admit of any commercial chemical tests.
II. Vegetable Tanning Materials and Tannin Infusions.
For the estimation of tannin, see the previous section, pp. 453 et seq.
To differentiate the infusions of the different tanning materials
certain characteristics may be employed. Infusions of barks have
generally a higher ash than those of woods, although these differences,
owing to the present frequent treatment of extracts with mineral salts,
are hardly reliable. The tanning contents found by the gravimetric
and the Loewenthal methods are in much closer accord with extracts
of woods than with those of barks. Conclusions may consequently be
drawn from determinations by both methods, although, owing to the
present treatment of extracts with chemicals, this is becoming daily
more uncertain. Quebracho wood extract, if it is pure and has under-
gone no other treatment, and when residual substances, such as
difficultly soluble matters, have been removed, can be recognised in
that in 100 parts of moisture-free extract there are 85-95 parts of
tanning substances, as determined by the gravimetric method. For
VEGETABLE TANNING MATERIALS 479
some years cold soluble quebracho extracts have been coming on to
the market, which by treatment with chemicals, generally with sulphites
or bi-sulphites, have been made completely soluble in water at ordinary
temperatures without residue ; such extracts may contain up to lo per
cent, of mineral matter. Sumac extract has a peculiar tea-like smell ;
chestnut-oak extract shows a fluorescence in the hide powder filtrate ;
mimosa bark extract in very dilute, clear, filtered solution, according to
Simand, gives with i drop of baryta water, when carefully allowed
to drop on to the surface, a greenish-blue precipitate which rapidly
becomes reddish-brown.
An addition of myrobalans extract to quebracho extract can be
detected by the Stiasny reaction^ with formaldehyde and hydrochloric
acid. For this test 50 c.c. of the quebracho extract solution of the
strength required for tannin analysis is boiled with 10 c.c. of dilute
hydrochloric acid and 10 c.c. of formaldehyde for about thirty minutes
under a reflux condenser. The quebracho extract is thus precipitated,
whilst the myrobalans tannin, if present in appreciable quantity, remains
in solution as pyrogallol tannin, and can be recognised in the filtrate
by the violet-coloured solution produced on the addition of sodium
acetate and a few drops of iron alum. For the differentiation of
tanning extracts, Philip recommends the ammonium sulphide reaction
proposed by Eitner and Meerkatz ^ for chestnut and oak wood extracts,
which Simand has also applied to. other tanning extracts. By dilution
with water the extract is brought to about 2 per cent, tannin content,
then 100 c.c. of this solution are boiled for a few minutes with the
addition of 0-5 g. of concentrated sulphuric acid. After cooling, 20 g,
of sodium chloride are added, and the solution filtered; 15 c.c, of
distilled water are mixed with 10 drops of yellow ammonium sulphide
in a test tube, and 1-5-2 c.c. of the filtrate added, well shaken up, and
allowed to settle. The precipitate of chestnut wood extract is at first
brownish, then reddish with a blue sheen ; with oak wood extract it is
yellowish-brown, and the supernatant solution Bordeaux red to orange.
In this test it is advisable to do a blank test simultaneously with a
really pure oak wood extract. Other extracts give the following
precipitates by this method : —
Oak bark, first yellowish, later fawn-brown.
Valonia, first yellowish-green, later chamois.
Galls, first yellowish, later reddish-brown.
Myrobalans, first greenish, remains unchanged.
Dividivi, bright greenish-yellow, remains unchanged.
Hemlock bark, after a long time yellowish-brown.
Mallet bark, yellowish-brown.
Mimosa bark, pink (reddish-white).
1 Cerber, 1905, 31, 186. 2 /^^^.^ 1885, n, 157.
480 LEATHER
No precipitate is formed with the following extracts: —
Quebracho wood, mangrove bark, pine bark, catechu, and gambier ;
pine bark occasionally gives a slight turbidity, and a few cold, soluble
quebracho extracts give a slight brownish precipitate.^
Faessler- has shown that colouring wool strips, which have been
printed with different metallic salts (the so-called garancine strips),
show recognisable differences with most tannins. If several such
strips be coloured in the same bath, mixtures of different tannins can
be frequently recognised, as one tannin acts more quickly on the strip
than another, and the strips show varying colour shades.^
III. Mineral Tanning Materials.
Of these only aluminium and chrome salts find practical application
in leather manufacture, the first in white or alum tanning, the latter in
chrome tanning,
{a) In Ahem Taiinmg, potash alum, soda alum, or aluminium
sulphate with common salt, are principally used. The tanning value
of these alumina salts, which should be as free as possible from iron, is
determined by estimating the contained Al^Og by the method described
in the section on "Aluminium Salts and Alumina," Vol. II., p. 6io.
iU) Chrome Taniiijig is accomplished either by means of chromium
salts (one-bath method) or by treatment with alkali chromates in acid
solution and the subsequent reduction of the chromic acid by means
of sodium thiosulphate (two-bath method). In the first case the reactive
principle is the basic chrome salts, which are best utilised when about
one-third basic, and which tan of themselves ; in the latter case they
are first produced in the reducing bath, and only then accomplish the
tanning of the hide fibre. For the production of the basic chromium
salts (usually the sulphate or chloride) either chromium hydroxide or
chrome alum may be used, or the concentrated chrome extracts speci-
ally prepared for the purpose may be employed. These latter, in
addition to basic chromium salts of inorganic or organic acids, usually
contain a greater or less quantity of foreign substances, such as alkali
salts, alumina salts, etc. The estimation of chromium salts and
chromates is described in the section on " Metals other than Iron,"
' For a careful study of the qualitative determination of tannins, see Stiasny and Wilkinson,
Collegium, igil.pp. 318 et se/j. Much advance in the qualitative detection and separation of
tannins has recently been made, and for the latest information the pages of recent issues of
Collegium must be consulted. Cf. also Leather Chemists' Pocket Boot, pp. 47 et seq,
- Collegium, 1906, p. 287.
"' Synthetic or artificial tannins, and especially Dr Stiasny's " Meradol D.,'* have attained
considerable commercial importance. They are mostly sulphonated condensation products of
phenols with formaldehyde. The waste liquor of julphite-cellulose manufacture is now largely
used as an adulterant or addition to extracts.
PRESERVED EGG YOLK 481
Vol. II., pp. 2^2 ct scq. The thi'osulphate estimation is carried out
iodometrically (see Vol. I., pp. 117 and 438).
IV. Other Tanning Materials and Accessories for
Leather Dressing.
Marine animal fats, especially fish oils, are utilised in chamois-
leather dressing, also egg yolk, common salt and flour with alum in
glace leather dressing, tallow in admixture with oils and mcellon
(degras or sod oil) in fat tannages used to stuff different kinds of
leather and increase their suppleness. For the latter purpose neats-
foot oil and bone oil are much used, whilst soap serves for the
preparation of soap pastes, fat liquors, etc.
Preserved Egg Yolk. — Egg yolks (hen or duck) recovered from
the albumin manufacture are preserved with common salt or boric acid
(also borax), or with both together (more recently also with fluorides),
and provide an important accessory in glace kid and chrome tannages.
An endeavour was made^ to dry out the &^^ yolks, but appears to
have been too costly or- unsatisfactory, as the preparation did not
remain long on the market. The value of preserved o.^^ yolk is usually
estimated by the moisture content, the egg-oil content, and the amount
of sodium chloride or other preservative present. The I.A.L.T.C. has
prescribed the following method for the examination of egg yolk : —
{a) Moisture. — From 10-20 g. are weighed out into a flat-bottomed
basin, together with a small glass rod and a little ignited sand,
thoroughly stirred at the ordinary temperature, and dried at loo^-ios"
to constant weight.
{U) Egg Oil ; Fat. — The residue from the moisture estimation is
broken up into small pieces, and extracted in a Soxhlet apparatus with
petroleum spirit boiling between 70°-75° until the petroleum spirit in
the extraction vessel becomes colourless ; then the residue is broken
up and again extracted. After the extraction is complete, the
petroleum spirit is distilled off from the previously weighed flask, and
the residue i^-g^ oil) dried for an hour at a ioo°-i05°. In the state-
ment of results the solvent used should be stated.
If the yolk contains free boric acid a certain proportion is extracted
by the solvent for the fats. To remove this the solution of the fat is
shaken out two or three times successively with distilled water at 30°
in a separating funnel, the aqueous solutions united, 20 c.c. of neutral
glycerol and a few drops of phenolphthalein added, and the solution
titrated with normal alkali (i c.c. normal alkali =0-0613 g. boric acid),
and the amount found subtracted from the amount of fat.
1 Gerber, 1875, I, No. 32.
Ill 2 H
482
LEATHER
(r) Sodium Chloride. — The residue from the fat extraction is freed
from petroleum spirit, placed in a funnel with a small asbestos filter,
which is fitted to a 250 c.c. flask, and lixiviated with hot water. An
aliquot part of the solution, which has been made up to 250 c.c, is
titrated with A^'io silver nitrate in the presence of potassium chromate.
{d) Total Ash. — 5 g. of &z<g yolk are dried in a platinum basin, and
the residue after the extraction carefully ignited at low red heat. If
the proportion of ash exceeds that of the sodium chloride content by
more than 1-5 per cent., borax and other mineral matters must be
tested for,
{e) Boric Acid and Borax. — These can be qualitatively recognised
by digesting the Q.g^ yolk with sulphuric acid, adding methyl or ethyl
alcohol, and obtaining the green-edged flame.
For the quantitative estimation, 5-10 g. of o.^^ yolk are made
alkaline with potassium hydroxide, dried, and the residue after
extraction ignited. The alkaline ash is dissolved in a small quantity
of hot water, rendered faintly acid with h}'drochloric acid, and boiled
for a few minutes under a reflux condenser to expel carbon dioxide.
After cooling, the solution is neutralised with normal alkali in the
presence of phenolphthalein, 20 c.c. of neutral glycerol added and
titrated to a permanent pink colour, which should not disappear on
the addition of more glycerol, i c.c. of normal alkali is equivalent to
0-0613 g- of boric acid. K. Windisch^ recommends the addition of
mannitol in the place of glycerol.
(/) Fluorides can be recognised by gently heating a not too small
amount of the ^^^ yolk with concentrated sulphuric acid in a platinum
crucible, and observing the etching produced on a glass plate placed
above.
Admixture of Other Oils.
The accurate recognition of other oils in o.^^ yolk presents great
difficulties. Vignon and Meunier- propose to determine the iodine
value, the unsaponifiable matter, and the total phosphoric acid in q^^
oil extracted with chloroform, and from these values to form conclu-
sions as to the addition of other oils. They have established the
following values for o.^^ oil : —
Hen-egg yolk.
Duck-egg yolk.
Iodine v.ilue
Unsaponifiable matter ,
Phosphoric acid (H3PO4)
48-7 to 54-8 (mean 52)
Per cent.
0-16 to 0-23
2-33
35-4 to 39-25 (mean 37-4)
Per cent.
2-43 to 2-85
1-91
^ Z. Unters. Nahr. u. Genussm., 1905, 9, 659.
- Collegium, 1904, p. 35.
ADMIXTURE OF OILS. TALLOW
483
That these values are not absolutely constant, the following figures
by Paessler show, which have also been obtained with egg oil extracted
with chloroform.
Hen-egg yolk.
Duck-egg yolk.
Iodine value
Unsaponifiable matter .
Phosphoric acid (H3PO4) .
42 to 48-1 (mean 45-9)
Per cent.
3-1 to 3-8 (mean 3-4)
3-7
54-2
Per cent.
6-2
3-1
To estimate the phosphoric acid 2 g. of egg oil are weighed into
a platinum crucible, 6 g. of an oxidising fusion mixture (consisting of
2-5 parts of sodium carbonate, 2-5 parts of potassium carbonate, and 5
parts of potassium nitrate) added, heated slowly over a Bunsen burner
until the whole of the carbon has disappeared, and the phosphoric
acid determined either volumetrically with uranium nitrate, or
gravimetrically.
The methods for the determination of the saponification, iodine and
acid values of oils are. described in the section on " Oils, Fats, and
Waxes," this Vol., pp. 1 14 et seq.
It is apparent from the above figures that any conclusions from the
values obtained must be drawn very cautiously.
The preserved egg yolk of commerce has approximately the follow-
ing constituents (mean and extreme values) : —
Preserved only with salt, or with
salt and boric acid.
Preserved only with boric acid.
Water.
Mineral matters .
Egg oil . , .
Albumins .
Sodium chloride .
Boric acid .
Mean per cent.
51-0
15-0
21-0
13-0
Extreme per cent.
47 to 54
12 „ 18
17 „ 25
9 „ 17
10 to 17
0 „ 2
Mean per cent.
50-0
2-0
30-0
18-0
Extreme per cent.
47 to 53
1-5 „ 2-5
27 „ 33
14 „ 22
1-5 to 3-5
100-00
100-00
13-5
•i-o
2 -5
Preserved egg yolk should have a clear orange-yellow colour, and
should be homogeneous ; the smell should be fresh and pleasant.
Tallow.^ — The examination and characteristics of tallow are
described in the section on " Oils, Fats, and Waxes," this Vol.,
p. 152. Tallow for the purposes of leather dressing should contain no
1 Cf. Schmitz-Dumont, Dingl. polyt. /., 1895, 296. 210, 233, 259; /. Soc. C/iem. Ind., 1895,
14, 815, 829.
484 LEATHER
free sulphuric acid. For stuffing upper leathers soft tallow is to be
preferred, as it is not so liable to form white incrustations on the
leather (these are due to high melting point palmitins and stearins).
For those kinds of leathers which are stuffed by immersion or drum-
ming in melted fats, such as belting and harness leather, a tallow with
a high melting point, such as sheep or pressed tallow, may be used.
Fish Tallow, a by-product of the oil recovery from fish (the fish
are chopped up into small pieces and pressed while hot ; the oil so
obtained deposits fish tallow at a low temperature), should contain
none or little of the gelatinous materials present during recovery. For
their estimation 20 g. are warmed with 150 c.c. of petroleum spirit,
filtered through a weighed and previously dried asbestos filter-tube,
the residue repeatedly washed, the tube dried and then weighed.
Frequently 6 per cent, and more of these non-fats are found. They
do not penetrate the leather, but remain on the surface as sticky
masses ; the smaller the quantity of these the more utilisable is the
fish tallow.
Fish Oils. — Fish oils provide in their original state or in oxidised
modified forms, such as mocllon and degras produced during chamois-
leather dressing or by special processes, the most important fatty
material of the leather industry. They serve, on the one hand, in
chamois-leather dressing as the tanning material proper ; on the other
hand, in curr}-ing as the most important stuffing material.
The following fish oils have mainly to be differentiated : —
1. Blubber Oils, from the blubber or entire bodies of the sea
mammalia : seal oil, whale oil, dolphin oil, porpoise oil.
2. Liver Oils, from the livers of fish : cod and shark oils.
3. Fisli Oils proper, obtained by pressing the entire fish : herring,
sardine (Japan), and menhaden fish oils.
The various oils are differentiated in commerce according to their
colour after recovery, viz. : — Pale brown and black.
It is extremely difficult to distinguish fish oils derived from different
sources. In the literature of the subject methods can indeed be found
by which the fish oils can be distinguished from one another and from
other oils by certain colour reactions which they give with sulphuric
acid, phosphoric acid, nitric acid, or sodium h}-droxide. More recent
researches by Holde^ and by Lewkowitsch - have shown that these
older methods arc not reliable. The latter has pointed out that every
coloration is characteristic not of the oils themselves but of their
impurities, and these can be removed by treatment, so that the pure
materials do not give the colour reactions ; consequently their value is
very small.
Shark oil is recognisable by its high percentage of fluid waxes, and
^ Mill. lech. Versuchsatislalt, Berlin, 1890, 8, 19. -J. Soc. Clicm. I mi., 1894, 23, 617.
FISH OILS 485
consequent high unsaponifiable value, which may be as high as 15 per
cent. The unsaponifiables are very imperfectly shaken out with
petroleum spirit, and ethyl ether should be used for the purpose.
According to V. Boegh ^ shark oil, or the addition of this oil to
others, can be recognised by the difficult solubility of its soaps, and he
describes the following method of examination : — 10 g. of the oil to be
tested are saponified in a flask with 50 c.c. of alcohol and 10 c.c. of a
solution of sodium hydroxide (362 g. NaOH per litre) on the water-bath
— with the addition of a reflux condenser if necessary — and after the
saponification is completed the solution is evaporated to dryness.
Boiling distilled water in a series of measured quantities is then added,
first 50 c.c. and then 5 c.c. at a time, whilst the flask is kept hot on
the water-bath and thoroughly well shaken, until it becomes obvious
that no more is dissolved ; the amount of water required is then noted.
If this is more than 70 cc, then it is to be concluded that the oil is
mixed with shark oil.
The density of fish oils at 15° varies from o-9r4-o-935, and the
refractive index (determined with Abbe's refractometer) from 1-471-
1-481 ; generally speaking, a high density is accompanied by a high
refractive index. The melting point of the fatty acids lies between 10°
and 38°, and if the fish oil has a high density its fatty acids have usually
a high melting point. The fatty acids of fish oils have ordinarily a
melting point above 30°. Fish oils always contain free fatty acids ;
usually the greater their quantity the darker is the oil.
According to Eitner two fish oils, light and heavy, are to be
distinguished in practice. Light fish oils are those of low specific
gravity which are fluid and usually light coloured ; by reason of their
low stuffing power they are also called " thin oils." They do not easily
combine with the leather fibre, but penetrate quickly and strike
through. In chamois dressing, which is dependent on the oxida-
tion of the fish oil and subsequent combination of the same with
the hide fibre, they act either quite inefficiently or not at all.
They show a great tendency to form a resinous incrustation on
leather stuffed with them. The heavy fish oils of high specific
gravity consist either of a light fluid fat, containing much dissolved
palmitin (herring or sardine oil), or more frequently of a thick, fluid,
fatty substance (liver oils), which, with the exception of shark liver
oil, are regarded as the most valuable variety used in tanning and
stuffing operations.^
As the differentiation of fish oils is so difficult, their investigation is
mostly limited to the determination of their suitability for a definite
^ Collegium, 1904, pp. 73 and 88.
'^ For the examinations of fish oils, fats, etc., see also the section on " Oils, Fats, and Waxes "
in this Vol., pp. 105 et seq.
486 LEATHER
process, and to tests for admixture of foreic^n matters, such as mineral
or rosin oil, etc.
The density and refractive index can be used as qualitative tests for
the presence of mineral and rosin oil in fish oil. Rosin oils, of which
only the denser need be considered, have a sp. gr. of o-gSo-o-gcjG, the
refractive index lies between I-532-I-552; with vaseline (petroleum)
oils these values are o-Sqo-o-qio and i-490-i-509 respectively. By the
addition of rosin oil the specific gravity and refractive index arc raised ;
vaseline oil lowers the specific gravity and raises the refractive index.
The adulteration of fish oils with rosin and vaseline oils is usually great,
so that their detection is easy. By determination of the specific gravity
and refractive index of an adulterated fish oil, the extent of the falsifica-
tion can be estimated within certain limits (10-15 per cent.), and a close
guess made as to the actual quantity added.
If it cannot be concluded with certainty that an oil has been
adulterated from a determination of its specific gravity and refractive
index, qualitative saponification tests must be made, which always give
some indication ; for this purpose, 10 g. offish oil are saponified with 3 g.
of sodium hydroxide in 5 c.c. of water and 40-50 c.c. of alcohol, under
a reflux condenser. The resulting soap is not completely soluble in
aqueous alcohol (1:15) if much of the adulterant has been added; if
little, the solution is tolerably clear, especially with petroleum oils.
The soap is decomposed with dilute hydrochloric or sulphuric acid,
and the fatty acid, etc., washed on a wet filter with hot water ; a portion
is then dissolved in 3 or 4 vols, of alcohol, in which it will dissolve
completely, if but little vaseline oil has been added (if much, it is
impossible to dissolve the whole in the given volumes of alcohol), and
made feebly alkaline with ammonia. A distinct turbidity appears if
the fish oil contains only a few per cent, of unsaponifiable matter, and
only a few particles are left or the solution remains clear if the oil is
pure. If the precipitated soap solution is diluted with an equal
quantity of water, the unsaponifiable oils appear after some time as
drops on the surface.
If it is desired to estimate the unsaponifiable matter quantitatively,
a weighed quantity of the oil (10 g.) is saponified in a flask fitted with
a reflux condenser with 5 g. of sodium hydroxide dissolved in a few
cubic centimetres of water and 50 c.c. of alcohol ; from half to one hour
is required with normal oils for the saponification, or one and a half to
two hours with difficultly saponifiable oils, while liquid waxes, such as
sperm oil, cannot be completely saponified in this way. The glycerine
soaps, after dilution with 50 c.c. of water, are poured into a separating
funnel, the flask washed with 100 c.c. of petroleum spirit (which should
contain no fraction boiling above 70'), and shaken thoroughly; the
shaking out is then proceeded with. The solution is shaken out three
FISH OILS 487
times successively with 75-100 c.c, which is amply sufficient. It is to
be recommended that in the first shaking out the fluids should only
be mixed with a gentle rotary motion, to avoid the formation of a
permanent emulsion. In spite of this, even with very careful shaking,
emulsions are liable to be formed ; these can, however, be rapidly broken
up by the addition of a few cubic centimetres of hot alcohol. The
petroleum spirit layer is separated, and, to remove dissolved soap, is
shaken up three times for five minutes each with a quantity of water
equal to about one-fifth of its volume ; the petroleum spirit is then
distilled off on the water-bath. The residue, the unsaponifiable matter,
is washed without loss by means of a small quantity of petroleum spirit
into a small weighed flask, and after removal of the solvent at 100"- 105°,
dried to constant weight, which should be completed within from half
to one hour. This method has been shown to be very satisfactory.
The following method also gives accurate results : — 10 g. of fish oil
are saponified as above, dissolved in water, the greater part of excess
of alkali neutralised with hydrochloric acid, and barium chloride,
calcium chloride, or lead acetate added in slight excess, the barium,
calcium, or lead soaps being precipitated in the cold. These are
drained upon a filter wijth the help of the pump, washed with dilute
cold alcohol (i : 20) and dried in a vacuum desiccator on blotting-paper.
The dried soaps, mixed with sand, are then extracted for six hours in a
Soxhlet extractor with chemically pure, water-free, freshly distilled
acetone, or petroleum spirit which should contain no fraction boiling
above 75°, After the solvent has been distilled off, the unsaponifiable
matter and a little water remain behind ; these are then dissolved in
a little petroleum spirit, and poured into a separating funnel ; the
subsequent procedure is then as usual.
The content of fish oils in oxidised fatty acids (Simand describes
these as " degras-former ") varies from o-i-6 per cent. Oils with a high
specific gravity and refractive index generally contain a correspondingly
large amount of hydroxy fatty acids. Old fish oils have, as a rule, a
high percentage of these acids. For the estimation of oxidised fatty
acids, see under " Degras " (p. 490).
The ash of a fish oil should be as free as possible from iron,i as
otherwise the leather treated with it is liable to be stained. Consider-
able quantities of iron are frequently present in the form of iron salts
of fatty acids ; these are not absorbed by the leather, and darken its
surface.
The addition of cotton-seed oil to fish oils causes, by reason of the
high melting point of its fatty acids (34°-38°), a corresponding raising
of the melting point of the fatty acids of the mixed oils ; and as fish
oils containing fatty acids with high melting point associated with
^ Cf. Simand, Gerber, 1890, 16, 205.
488 LEATHER
high specific gravity also show a considerable content of oxidised fatty
acids when not containing cotton-seed oil, it may be concluded, accord-
ing to Simand, that a high melting point of the fatty acids with a low
content of oxidised fatty acids and low specific gravity is due to the
presence of unoxidised cotton-seed oil. The chief adulterants for fish
oils, however, are always vaseline oils, and in considering possible
adulterants it is well to consult a current price-list.
The Greenland "Three Crown" fish oil is a mixture of different
sorts of oils, chiefly seal and shark oil, with occasionally whale oil. The
Swedish "Three Crown" fish oil is a mixture of various seal and fish
oils.
A fish oil, for use in leather stuffing, should not have too high an
iodine value, as it renders the leather liable to " spue" ^ as the result of
oxidation (see further under " Degras," p. 489). Fish oils with a high
iodine value lose their tendency to spue after prolonged boiling, there-
fore any oil with an iodine value of over 130 should be treated in this
manner.
Simand has pointed out that so-called Sea-Lion Oil consists of
rosin oils (the ordinary common varieties of sp. gr. 0-996) which have
been mixed with 10-30 per cent, of a very rich fish oil to produce the
characteristic smell.
Neat's-foot and Bone Oil. — Both these oils are much used in the
preparation of fat liquors for chrome leather, and must, therefore, be
free from solid fats to avoid spueing. In order to fulfil these conditions
completely, these oils must be "cold-stable," i.e., they must give no
deposit on standing at a low temperature. It is usually demanded "of
these oils that they should be cold-stable at minus 10 . H. Becker -
describes the following method of testing: — A test tube iS mm. wide
is filled with a sample of the oil to be tested, which has been dried by
means of calcium chloride and subsequent filtration through a dry filter
paper, A bored cork fitted with an accurate thermometer is placed in
the test tube so that the bulb is in the middle of the layer of oil. Then
this sample is placed, together with a similar undehydrated sample, in
a freezing mixture, which is at the guaranteed minimum temperature,
Neat's-foot oil passes this cold test if it remains completely fluid and
clear at the end of one hour,
Moellon and Degras. ^ — Originally these terms were only applied
to the product resulting from the oxidation of fish oil in chamois
dressing, which finds much application in the leather industry as a
stuffing mixture ; from good samples of this kind water should not be
^ To " spue," in this sense, is to produce on the leather resinous spots of oxidised oil. The
spueing referred to later as produced by neat's-foot and bone oil is merely a whitish deposit
caused by the crystallisation of hard fatty acids.
2 Collegium^ 1907, p. 393. ^ Cf. Collegium, 1906, p. 304.
MOELLON AND DEGRAS 489
deposited even after long standing. Moellon and degras contain water
(about 8-20 per cent.) and 5-20 per cent, of a substance (not containing
nitrogen, as Simand assumed) which is produced during chamois
dressing, and is characteristic of all these materials. F. Simand^
called this substance " degras-former," and F. Jean- "resinous matter"
or "degragene." W. Fahrion^ has proved that it consists simply of
oxidised fatty acids (in chamois dressing produced by the action of the
oxygen of the air on the unsaturated acids and their glycerides), and
describes it shortly as " oxy-acids." These oxidised acids and their
glycerides enable the fish oil to form emulsions with water in almost
all proportions ; this property is the conditional factor which enables
moellon and degras to penetrate the leather during stuffing and spread
easily and uniformly throughout. They are therefore absorbed as
watery emulsions of more or less strongly oxidised fish oil. They
emulsify the more easily the higher the proportion of contained
oxidised fatty acids, though according to Fahrion this is limited by
their increasing viscidity. If the oxidation of the fish oil in chamois
dressing proceeds too far {i.e. to a too high oxidised fatty acid content)
nitrogenous substances of a syrupy gelatinous nature also come out of
the pelt with the degras, which are only slowly and incompletely
absorbed by the leather. Good samples of moellon and degras produce
a certain "feel" in the leather which is described as "mellow."
Moellon and degras have essentially a lower iodine value than the
fish oil from which they have been derived. This is not only due to
the oxidation during chamois dressing, but also to a polymerisation of
the unsaturated fatty acids. This lowering of the iodine value is so far
of importance in that it opposes the tendency of the fish oil or its
products to oxidise in the leather and so cause spueing. According to
Fahrion the iodine value of a moellon or degras (calculated on the dry
weight) should not exceed 100.^
The oxidised fish oil is recovered from the treated chamois leather
either by moderately powerful pressure (when the resulting product is
described as " moellon " : French or pressure process), or by washing
out the leather with alkaline carbonates, thus converting the material
into a thin emulsion out of which the degras is recovered by treatment
with sulphuric acid (German process). Very frequently a combination
of both methods is used. The moellon is always more or less fluid ; the
degras is generally thicker owing to the presence of soaps (3-4 per
cent, on the water-free weight) and of leather fibres. In commerce
these differences are no longer strongly marked.
1 Gerher, 1890, 16, 243. 2 Monit. Scient., 1889, IS- 889.
3 Z. angew. C/iem., 1891, 4, 172 ; Chem, Zeit., 1893, 17, 524 ; 7; Soc. Chem. hid., 1891, 10,
557; 1893. 12, 937.
■* Cf. Fahrion, Che7n. Zeit,, 1891, 15, 1791 ; 1892, 16, 862 ; /. Soc. Chem. Ind., 1892, 11, 183.
490 LEATHER
Water hi Mocllon and D^gras. — For this determination, according to
Fahrion, 2-3 g. are weighed into a platinum crucible without a lid, and
the water boiled off at once by means of a small Bunsen flame, which is
carefully and repeatedly applied to the crucible and withdrawn. The
point at which all the water has disappeared is denoted by a low
crackling and a wisp of smoke, and with a little practice can be most
accurately observed. The moisture content varies with the sample, in
the French process from 8-20 per cent, and with degras from about
20-40 per cent. ; over 25 per cent, could not therefore be described as
normal.
AsJi. — The residue from the moisture estimation is carefull)- ashed
and the ash analysed. The quantit)' of ash in moellon made by the
pressure method is only a few looths of i per cent., but in degras up
to 3 per cent. The ash of moellon consists chiefly of lime, that of
degras, besides sulphates, contains calcium carbonate (from calcium
soaps) and sodium carbonate (from sodium soaps). Degras materials
should contain no iron oxide (derived from iron soaps).
Substances insoluble in Petroleum Spirit (Soaps, Leather Fibres,
Dirt, etc.). — 20 g. of dry degras are dissolved by gently warming in
150 c.c. of petroleum spirit, filtered through a weighed and previously
dried asbestos filter tube, the residue thoroughly washed with petroleum
spirit, dried and weighed. The latter consists chiefly of leather
fibres, dirt, and soaps. The mineral constituents must be determined
by speciall)- incinerating.
Unsaponifiable Matter. — The method of estimation has been
described in connection with fish oils (pp. 486).
Oxidised Fatty Acids (Fahrion). — This estimation depends upon the
fact that the free oxidised fatty acids are insoluble in petroleum spirit.
For the determination, 10 g. of degras are saponified with constant
stirring in a porcelain basin on the water-bath, by the addition of
about 7 g. of potassium hydroxide, which have been dissolved previously
in about 10 c.c. of water and 50 c.c. of alcohol. When the alcohol has
been completely driven off, the contents of the basin are dissolved in
about 100 c.c. of hot water, poured into a separating funnel, the soap
separated by the addition of a slight excess of dilute sulphuric acid
(i :4) or hydrochloric acid, and after cooling shaken out carefully for
five minutes with petroleum spirit, which should contain no fraction
boiling above 70". When, after several hours' standing, the petroleum
spirit has separated clear from the water, the latter is withdrawn from
below, when the oxidised fatty acids adhere to the walls of the vessel.
The petroleum spirit can then be poured from the upper opening of the
separating funnel, free from oxidised fatty acids. The latter are again
washed several times with small quantities of petroleum spirit (if
wool fat be present, which is mostly indicated by turbidity of the
MOl&LLON AND DEGRAS
491
solution), also with warm petroleum spirit with slight shaking (without
inserting the stopper) until all soluble fatty acids are removed. The
oxidised fatty acids are then dissolved in a little warm alcohol, and
the filtered solution evaporated in a weighed platinum basin on the
water-bath, and dried to constant weight at 105°. The soap solution
used for the estimation of unsaponifiable matter, after extraction, may
also be used for the determination of the oxidised fatty acids.
Mineral Acids. — If the degras shows a strongly acid reaction, 25 g.
are boiled with 200 c.c. of water, allowed to cool, the two layers separated
by means of a separating funnel, the nature of the acid (especially
sulphuric) determined in an aliquot part of the aqueous layer, and
another portion titrated with normal alkali.
Free Fatty Acids. — The acid value is determined as usual, and
calculated as oleic acid (taking into consideration the mineral acid if
present).
Fats and Oils. — The fatty acids in the petroleum spirit solution,
freed from unsaponifiable matter and oxidised fatty acids, are washed
with water to remove mineral acids, and the petroleum spirit distilled
off. The fatty acids so obtained can be examined further as to
saponification value, iodinfe value, melting point, solidifying point, etc.,
to obtain information as to the fats contained in the degras.
Density of Water-free Degras (Simand). — The degras is carefully
heated to 105° until the water has all been removed, the residue
after cooling treated with petroleum spirit, and the solution freed
from soaps by shaking with very dilute hydrochloric acid, which
is afterwards removed by washing with water. After distilling off
the petroleum spirit from the filtered solution the fats of the degras
remain behind. These are quite fluid at ordinary temperatures and
only a few samples deposit solid constituents after some time. The
specific gravity rapidly increases and the refractive index decreases
with the content of oxidised fatty acids. Simand gives the following
representative examples : —
Sp. gr.
Oxidised fatty
acids.
Refractive index.
Molting point of
fatty acids.
Ash.
1.
2,
3.
4.
0-9603
0-9749
0-9785
0-9915
Per cent.
16-65
18-53
18-39
23-83*
1-474
1-480
1-478
1-486
30°-5 to 31°
33° -5 „ 34°
34°-5 „ 35°
34°-0 „ 34°
Per cent.
0-078
0-025
0-062
0-019
* These numbers were obtained from a test in a Bohemian degras works, and are the highest that Simand
ever found.
The oils used in the manufacture of Nos. 2 and 4 had specific
gravities of 0-9269 and 0-9294 respectively^ and contained i-l8 per cent,
and 1-47 per cent, of oxidised fatty acids; the melting points of the
492 LEATHER
fatty acids were from Si^-Si'-S- Eitner has also conducted researches
on these lines.^
For a number of years artificial dcgras has been prepared by the
direct oxidation of fish oils (by blowing air into the warm oil, or some
other method of oxidation) and subsequent emulsification with water.
If these substances are prepared from good raw materials, and if they
are sufficiently oxidised and emulsified, they are just as valuable as
natural mocUon or dcgras. In addition, a large number of products
come into commerce, consisting of natural or artificial dcgras with the
addition of fish oil, tallow, palm and cocoa-nut oil, wool fat, vaseline,
mineral and rosin oils, colophonium, and other cheap fats.
An appreciable addition of tallow raises the melting point of the
fatty acids, and that of cocoa-nut oil or palm oil raises the saponifica-
tion value ; in normal dcgras both (calculated on the moisture-free
material) are about the same or very little higher than those of fish oil.
Vaseline, JMineral and Rosin Oils are estimated in the same way as
in fish oils (p. 486).
Wool Fat. — For tliis estimation 5-6 g. of dcgras are saponified as
above, the fatty acids extracted from the soap solution and treated
with ether. The ethereal solution is evaporated in a small weighed
flask, the residue boiled under a reflux condenser with one and a half
times its quantity of acetic anhydride for one to two hours, water added,
and then, to remove the acetic acid, boiled out several limes with water.
The whole is then dried and the acctylated fatty acids, the cholesteryl
acetate, etc., dissolved in fifteen times the quantity of alcohol (75^150
c.c.) on the steam-bath and again cooled. The difficultly soluble
cholesteryl acetate which is again almost completely precipitated on
cooling, is filtered off, again crystallised twice from fifteen times the
quantity of alcohol (to remove the vaseline oil as completely as
possible), and then dissolved in ether ; the ether is distilled off and
the residue weighed. Wool fat yields as a mean of ver}' variable values
(9- 59- 1 8-7 1 per cent.) 1405 per cent, of cholesteryl ester. If the weight
of the ester be multiplied by 7, a rough approximation as to the
proportion of wool fat present is obtained.
The presence of wool fat is recognisable, according to Simand,
by the shiny surface of the solidified fats, or if these do not solidify,
by the shiny non-crystalline surface of the fatty acids extracted after
saponification. By rubbing some of the oil on the surface of the hand
the characteristic smell of wool fat may be recognised.
For the estimation of Colopluviiuni (resin), the soap solution derived
from the determination of the unsaponifiable matter is decomposed with
hydrochloric acid and washed ; in this way the mixture of resinous and
fatty acids is obtained, in which the rosin acids are determined by
1 Gerber, 1893, 19, 243, 257.
OILS. SOAP. NITROGEN 493
Twitchell's method. This process depends on the conversion of the fatty
acids, by the action of hydrochloric acid gas on their alcohoHc solution
into their ethyl esters, whilst rosin acids remain unaffected by this treat-
ment. The method is described in the section on " Special Methods
of Analysis employed in the Oil and Fat Industries," this Vol., p. 195.
According to the regulations of the I.A.L.T.C., the examination of
the fats shall proceed according to the following general scheme : —
Moistures.
Mineral matters.
Substances insoluble in petroleum spirit, ash-free (non-fatty matters).
Substances soluble in petroleum spirit /""saponifiablc matter.
Isaponinable matter.
In degras and such materials the proportion of oxidised fatty acids
must be determined in addition to the other constituents.
Vaseline Oils and Mineral Oils,^ which are used in the leather
industry mainly as adulterants, should have a density of from o-SS-o-QO
at 1 5°. On cooling to low temperatures ( — 10°) for one to two hours they
should only become thick, and in no case should deposit any appreci-
able quantity of solid paraffins; they must be free from sulphuric acid,
which may be estimated by shaking out with warm water in the
presence of glass beads. Adulteration with rosin oils can be recognised
by the raising of the density and of the refractive index.
Soaps. — Soaps are used in the preparation of the soap stuffings
used in the dressing of upper-leathers, and especially in chrome tanning
for the preparation of fat-liquors, which are watery fat emulsions made
with the assistance of soap and alkali carbonates. A slight free alkali
content is not in this case disadvantageous, as the soaps come into
contact with the oils, which contain free fatty acids. To obviate
precipitation, etc., the soap should be as free as possible from solid
fatty acids, and should be prepared from non-drying oils, of which olive,
castor, and cold-tested neat's-foot oil are suitable. For the more com-
plete examination of soaps, see the section on " Special Methods
employed in the Oil and Fat Industries," this Vol., pp. 188 et seq.
V. Control of Working Conditions.
The Estimation of Nitrogen by the Kjehldahl method provides in
almost all stages of tanning a very valuable means of works control.
In the soaks, limes, and tan liquors the amount of dissolved hide
substance, and during tanning and in the finished leather the degree of
tannage, is in this way easily determined. According to the researches
of von Schroeder and Paessler, the hides which normally come into
consideration in leather manufacture, viz., ox, calf, horse, and pig,
have in the water-, ash-, and fat-free hide substance a constant nitrogen
' Cf. Simand, Gerber, 1890, 16, 193.
494 LEATHER
content of approximately 17-8 per cent. To estimate the amount of
hide substance, the quantity of nitrogen found must therefore be
multiplied by 5-62.
According to Paessler, the best method of carrying out the
Kjehldahl method is to disintegrate the material by the addition of
15 c.c. of concentrated sulphuric acid and 0-7 g. of mercury. For
further details of the method, see the section on " Artificial Manures,"
Vol. II., pp. 375 ct scq. According to the amount of the nitrogen
present, 0-5-1 g. of the material is taken for the determination. The
disintegration must be continued until the solution is absolutely
colourless. To accelerate the process, the use of sulphuric containing
200 g. per litre of phosphoric anhydride is to be recommended.
If it is required to estimate the nitrogen in liquids, it is necessary
before disintegration to evaporate to dryness with the addition of a
little sulphuric acid to fix the ammonia, and a little ferrous sulphate to
destroy nitric acid.
To test for Dissolved Albuminous Substances in Soak Waters or
Lime Liquors the method of A. Jolles ^ may be applied : — The filtered
liquor is treated with clear calcium chloride solution and then acidified,
when the albumins come down as a flocculent precipitate. These can
then be estimated quantitatively either gravimetrically or by the
Kjehldahl method. Eitncr- has proposed to substitute sodium hypo-
chlorite for calcium chloride. He differentiates the dissolved albuminous
materials in lime liquors as : —
{a) Soluble hide substance combined with lime.
{li) Lime-free soluble hide substance.
{c) Hydrolysed hide substance (Peptone).
By precipitation with carbonic acid (c/), with acetic acid {b), and with
hypochlorous acid (<:), fractions may be precipitated and separated.
E. Stiasny^ estimates the dissolved hide substance in soaks and
limes by a method which depends on the titration of equal quantities
of the liquor to be tested with and without the addition of formalde-
hyde ; the difference in the quantities required is taken as a measure of
the dissolved hide substance present. Sulphides, etc., must previously
be removed by the addition of iodine. This method has the advantage
of being rapidly executed, but the disadvantage that no absolute values
but only proportional figures are obtained.
The action, of the lime liquor depends upon its content in caustic
lime, ammonia (by decomposition of hide substance), sulphides and
enzymes. The estimation of the caustic alkali and ammonia can be
performed in one operation, in which the ammonia is distilled over
from the clear lime liquor into iV/io sulphuric acid and the excess of
1 Z. Anal Chem.^ 1890, 29, 406. 2 Gerber, 1895. 21, 157, 169.
^ Collegium^ 1908, p. 371 ; 1910, p. 181 ; /. Soc. Chem. Ind., 1908, 27, 1031 ; 1910,29, 771.
TAN LIQUORS
495
acid titrated back, whilst the residue left in the distillation flask is ti-
trated with iV/io acid in the presence of phenolphthalein, and the calcium
hydroxide thus estimated. This distillation should not be pushed too
far, as lime liberates ammonia from the organic matter always present.
Tan Liquors. — For the control of fresh liquors, such as tan liquors,
the barkometer is generally used in practice as a means of determining
their strength and maintaining their constancy. Old and used liquors,
as, for example, the suspender liquors, in which the hides commence the
process, cannot be dealt with in this way owing to the large non-tannin
content which completely vitiates the results. As barkometer, an
ordinary hydrometer, made either of glass or metal, is used, either with
arbitrary degrees or with the div^isions of some standard scale, e.^., such
that the distance between each pair of graduations corresponds to o-ooi
sp. gr. (25" barkometer = 1025 sp. gr.). These latter are described in
England and America as " Barkometer degrees," but Eitner calls them
" degrees Eitner." A definite conclusion as to the relative tannin
strength from the barkometer reading is only possible with fresh
liquors and those made from the same raw materials or mixtures;^
with used liquors a comparison is only possible if they have all had
similar treatment (as, for instance, in the successive pits of a series of
handlers or suspenders). With liquors from different tanneries and
different sets of handlers this is usually no longer permissible. Even
with fresh liquors from the same tanning materials the ratio of the tans
to the non-tans varies according to their origin and value, as is shown
by the following results obtained by Paessler.
100 c.c. liquor of sp. gr. 1-014= 14° barkometer, contain :—
Tans.
Non-tans.
R-
g-
Sumac ......
1-9
1-4
Pine bark
2-1
1-7
Dividivi
2-2
1-1
Oak bark
2-2
1-2
Oak wood extract .
2-3
1-4
Myrobalans ,
2-3
1-0
V^alonia ....
2-5
0-9
Trillo ....
2-5
0-8
Chestnut wood extract .
2-5
1-2
Knoppern ....
Gambier ....
2-5
2-6
0-8
1-0
Mimosa bark
2-9
0-6
Quebracho extract (cold soluble) .
Mangrove bark ....
3-1
3-4
0-6
0-5
Quebracho extract (ordinary)
Quebracho wood ....
3-8
3-9
0-3
0-3
1 C/. Paessler, Collegium, 1904, p. 116 ; /. Soc. Chem. Ind., 1904, 23, 553- While the indica-
tions of the barkometer are of little value as regards the total tannin present, they give pretty
accurate information of the loss during use, if readmgs are made before and after an operation.
496 LEATHER
It is obvious from this Table that a correct valuation of tan liquors
can only be made by the direct estimation of the tannin content.
Fresh Liquors, i.e. such as are obtained by the extraction of fresh
tanning materials with water, do not contain acids produced by
fermentation, and are examined in exactly the same manner as
extracts. The proportional quantities prescribed for the examination
of tanning materials and extracts require consideration.
Used T(xnning Liquors, i.e. those containing free acid due to
fermentation/ or the addition of organic or mineral acids, are in all
cases to be analysed by the I.A.L.T.C. official hide-powder shake
method, as the acids, which are partly taken up by the hide powder,
have a smaller effect on the results obtained by this method than on
those obtained by the filter method.
B. Weiss- recommends that the liquor should be examined by
gravimetric methods, but that the quantity of acid should be estimated
in the residues (total solids and non-tans) and allowed for in calculation,
acid-free total solids minus acid-free non-tans giving the actual tanning
substances. In this v/ay the estimation as tannin of acid absorbed by
the hide powder would be prevented.
Besides tans and non-tans, the total acid, the volatile acids, and the
non-volatile acids are also of importance and must be estimated. The
volatile acids derived from fermentation are, as Wladika^ has shown,
mostly acetic, and the non-volatile acids chiefly lactic ; but this varies
considerably in different yards and with different materials.
Acidity {Total Acids). — The following methods are in use for this
estimation : —
Proctet^s Method.^ — This simple method consists in running clear
standardised lime water from a burette into the clear filtered liquor
until a permanent cloudiness of calcium tannate is produced. If the
liquors are too dark they must be diluted. The carbonic acid, which is
present in most liquors which are not too old, is, of course, in so far as
it is not removed by shaking, partially estimated by this method.
It can, however, be removed before titration by adding common salt
and shaking vigorously.
Koch's Method;' improved by Paessler and Spanjer.*^ — In this method
25 c.c. of the clear, filtered liquor are measured into an Erlenmeyer
flask and precipitated with 25 c.c. of gelatin solution (5-6 g. purest
eelatin dissolved in 1 litre of hot water, and the solution filtered after
' Cf. F.Andreasch, Gerber, 1895-97, vols. 21-23 ; /. Soc. C/iem. Imt., 1896, 15,910 ; 1897, 16,
52, 248, 340> 620, 740, 925. 1025.
'■2 Cerber, 1895, 21, 63. ^ Il>id., 1890, 16, 3, 15. 28, 61.
* Proc. Newcastk-on-Tyne Clum. Soc, 27th March 1879.
6 Dingl. polyt. J., 1887, 264, 395 ; 265, 33 ; 267, 459. 5i3 ; 1888, 269.
6 Gerber Zeil., 1899,32, Nos. 76 and 77; 1900, Nos. 45, 50-53, and 55; Collegium, 1903,
p. ID ; /. Soc. Clum. hid., 1899, 18, 773, 927-
ACIDS. SPENT MATERIALS 497
cooling). The precipitate must come down quickly and thoroughly in
the flocculent form ; if this be not the case, a more dilute gelatin
solution must be used (with weak tan liquors a gelatin solution of
2 g. per litre usually suffices). The unfiltered solution is then titrated
with baryta water or lime water of known strength, and the end-point
recognised by spotting on litmus or azo-litmin paper. The acidity of
the gelatin solution must be determined and subtracted from the
alkali required. The total acidity is calculated as acetic acid per lOO
c.c. of liquor.
A. Hoppenstedt^ has recommended the precipitation of the tannin
with quinine solution, and the subsequent titration of the filtrate with
Njio alkali. According to C. Bennett and C. D. Wilkinson,- the method
is so full of difficulties as to be valueless.^
Estimation of Volatile and Non-volatile Adds. — For this estima-
tion, lOO c.c. of the liquor to be examined are distilled in steam with a
condenser attached, until there are 300 c.c. of distillate and the liquor
is reduced to about 20 c.c. The acidity of an aliquot portion of the
distillate is estimated by titration in the presence of phenolphthalein
and calculated as acetic acid. If the volatile acidity be subtracted
from the total acidity, the non-volatile is obtained and calculated as
lactic acid by multiplying by 1-5. The latter value can be determined
independently by cooling the residue in the distillation flask, making
up to 100 c.c, and determining the acidity of an aliquot portion in the
same manner as the total acidity, and calculating as lactic acid.
It is obvious that in such mixtures of weak acids and their salts,
the amount of acid estimated will largely depend on the indicator
used, and no useful comparison can be made between titrations made
with different indicators or under different conditions. (Procter.)
Spent Tanning Materials. — In order to determine the extent to
which tanning materials are exhausted, they arc examined after use as
to the tannin they still contain. To estimate this tannin the material
is dried, ground, and then examined exactly in the same way as fresh
materials, except that a greater weight is taken and that, after
extraction, the solution must be brought to the required strength. The
results are given on the air-dry weight of the material. In order to
compare the tannin residue in extracted materials with that in fresh,
the former must be recalculated to the original weight of the latter by
multiplying the tanning content by the percentage of insoluble matter
found in the original material, and dividing by the percentage of
insoluble matter found in the spent material, the insolubles being
1 Collegium, 1907, p. 77 ; /. Soc. Chem. /mi., 1907, 26, 331-
2/. Soc. Chem. Ind., 1907, 26, 1 186.
3 Cf. also Collegium, 1907, p. 77 ; 1910, pp. 298, 4c6, 410; 1911, pp. 150, 219, 225, 233,
432.
Ill 2 I
498 LEATHER
unaffected by the extraction. For further details, see section on
" Vegetable Tanning Materials," this Vol., pp. 45 8 ct scq.
VI. The Examination of Leather.
Sampling. — To obtain a true sample of a parcel, pieces must be cut
from the butt, bellies, and shoulders of each of several hides. The
single parts of the hide give essentially different results, by reason of
their different constitution and texture. The samples taken must be
cut up into small pieces and ground in a mill to a uniform woolly
powder. If, as in the case of heavily stuffed leathers, grinding is not
permissible, the leather must be cut up into the smallest possible pieces.
(a) Vegetable Tanned Leather.
Moisture. — For this estimation, 10 g. of the finely ground leather
are dried at loo^-ios" to constant weight. These results, if it is not
expressly stated otherwise, should be calculated, according to the
recommendations of von Schroeder,^ to the average water content,
which happens to be the )'early mean of that kind of leather. These
yearly means have been established by von Schroeder ; the average
water content of the unstuffed leathers (sole, light and inner-sole
leathers) is about iS per cent., and that of stuffed leathers (belting,
various kinds of harness leathers, upper leathers) is dependent on the
fatt)' content of the leather, and can be calculated according to the
following formula : —
vy^ _ 1800(100— F)
~ 8200+18 (100- F)'
where W is the average water content and F the fat content of the
dry leather. To judge the moisture of air-dry leather which has been
stored normally the following rule may be used: — If the average
moisture content of unstuffed vegetable tanned leather is taken as 18
per cent., then in the dry and warm season this will sink to 15-5 per
cent. ; in the moist, cold season it will rise as high as 20-5 per cent. ; so
that the variation in the course of the year is about ±2-5 per cent.
For stuffed leathers the average water content is dependent on the fat
content of the dry leather ; generally speaking, the variations throughout
the year are somewhat smaller, being about ± 2 per cent.
In leathers which have been dried at high temperatures, as in
the Austrian Tersen^ the moisture is generally slightly lower, as this
leather, even after lengthy storing, does not reach the water content of
other leathers.
1 DingLpolyLj., 1894, 293 ; /. Soc. Chem. Ind.^ 1895, 14, 587.
VEGETABLE TANNED LEATHER 499
Obviously the average moisture of a leather will vary widely with
the season, the climate, and the mode of drying. In England, 15
per cent, is nearer the average, as heat is almost always used. It is
necessary, therefore, to give the actual water found, even if a calculation
to 15 per cent, or to dry matter is added. (Procter.)
Estimation of Mineral Matter (Ash), — 10 g. of the leather are
carefully and completely incinerated at a low red heat in a platinum
basin ; the addition of ammonium nitrate is sometimes necessary. The
mineral content of a normal leather (on the air-dry weight) varies
between 0-25-1 -6 per cent., and with sweated leathers is naturally lower
than with limed leathers. A content greater than i-2 per cent, usually
signifies either bad workmanship in the cleansing processes (insufficient
deliming), or the use of tanning extracts rich in mineral matters
(sulphited extracts), or the addition of magnesia salts to the tan liquors
to accelerate tanning, or the treatment of the leather with mineral
matters (alumina, etc.) ; and one of over 2 per cent, usually signifies the
weighting of the leather therewith, though in sole leather a somewhat
higher limit must be allowed. In cases of weighting this limit is
usually appreciably overstepped, so that sometimes a mineral matter
content of over 20 per cent, is found. In such cases a qualitative
analysis of the ash will indicate the nature of the material, which can
then be confirmed by the quantitative estimation. Among mineral
weighting substances are the following : — Barium chloride, barium
sulphate (formed in leather by double decomposition or mechanically
applied), and less frequently, common salt, magnesium and sodium
sulphates, lead salts (nitrate or acetate).
Magnesium sulphate, and sometimes sodium sulphate, in conjunction
with glucose are among the commonest weighting materials in present
use, both for leather and textiles ; and it must be remembered that the
weight actually obtained is higher than that of the dry mineral ash by
the water of crystallisation. (Procter.)
Estimation of the Fat.— 20 g. of leather are extracted in a Soxhlet
apparatus for three to four hours with carbon bisulphide and the
quantity of fat then determined in the usual manner. The estimation
of fat must also be made on the unstuffed leathers, as these contain
natural fats, so-called skin-fats. The fatty content of unstuffed leathers
varies between o-2 and i-2 per cent. ; in light-sole leather, which is
usually lightly oiled (with linseed or fish oil), it sometimes rises to 3 per
cent. Sheep-skins have generally a high natural fatty content.
Estimation of the Loss on Washing (Auswaschverlust) and of
the content of Extractable Tans and Non-Tans. — Every vegetable
tanned leather contains a certain quantity of substances which can be
washed out by water at ordinary temperatures, and which are described
collectively as " loss on washing." For their estimation, 20 g. of the
500 LEATHER
powdered leather, freed from carbon bisulphide, are placed in a Koch
extractor (see under " Vegetable Tanning Materials," p. 456) with or
without a layer of sand ; after soaking in water for about twelve hours,
it is extracted at the ordinary temperature to a total volume of i litre
within one and a half to two hours, and the infusion filtered. Then
200 c.c. of this solution (derived from 4 g. of leather) are evaporated to
dryness in a platinum basin, and the residue dried to constant weight,
weighed, incinerated, and again weighed ; the total quantity of organic
soluble matter is thus obtained. Weighting with soluble mineral salts,
barium chloride, sodium chloride, etc., is also estimated by this means.
Methods and temperatures of extraction are at present somewhat
variable, and it is very desirable that some definite decision on the
point should be reached.
For the estimation of non-tans, 500 c.c. of the solution are evaporated
to 125 c.c, which still represents 10 g. leather, the tannin removed
therefrom by hide powder in the usual manner (see p. 472), and 50 c.c.
of the filtrate evaporated to dryness and the residue dried to constant
weight and weighed as non-tans; the residue is finall}' incinerated, and
the amount of organic non-tans so obtained. The tannin is obtained
by subtracting the ash-free non-tans from the ash-free loss on washings.
The organic " loss on washing " of the various kinds of leather
differs wide!}', and varies in normal unweighted leathers (air-dr)'), as
follows : —
Per cent.
In sole and light-sole leathers from . . 3 to 20
In belting leathers from . . . . 3 „ 10
In upper leathers . . . . . 3 „ 10
Leathers tanned in strong liquors give a high "loss on washing";
from this basis conclusions may frequently be drawn as to the nature of
the tannage which any piece of leather has undergone. The highest
" loss on washing " is found in North German sole leathers, English
light-sole leathers, and Austrian Knoppern- and Valonia-terzen. The
amount of tans and non-tans in the " washings " serves also for the
detection and estimation of weighting with organic materials, such as
sugar, glycerin, etc. (The weighting materials most frequently used
are glucose and the other starch sugars.) In unweighted leathers the
amount of the tans is at least as great as that of the non-tans, so
that if the latter exceeds the former weighting must be suspected, and
qualitative tests and a quantitative determination made. (For further
details ^ee the estimation of sugar, p. 502.)
Estimation of Hide Substance and Combined Tannin. — For this
determination use is made of the fact that hide substance contains
nitrogen while the other substances present do not. The percentage of
hide substance can therefore be calculated from the nitrogen content of
VEGETABLE TANNED LEATHER 501
the leather ; the quantity of combined tannin is then icx) minus the sum
of the other constituents, viz., water, mineral matters, fat, " washings,"
and hide substance.
According to von Schroeder and Paessler,^ the nitrogen content of
the moisture, ash, and fat-free hide has the following values : —
17-8 per cent, in cow (calf, kips), horse, and pig skins; i per cent.
nitrogen equivalent to 5-62 per cent, hide substance.
17-4 per cent, in goat, deer, and buck skins; i per cent, nitrogen
equivalent to 5-75 per cent, hide substance.
17-1 per cent, in sheep skins; i per cent, nitrogen equivalent to
5-85 per cent, hide substance.
The nitrogen estimation is carried out according to the Kjehldahl
method with o-6 g. of powdered leather (see p. 493).
The results of the analysis are arranged as follows ; —
Moisture.
Mineral matters.
Fat.
Organic "loss on washing "<
" I Non-tans.
T ..u 1 .. fTannin.
Leather substance < ,,. . ,
(.Hide substance.
To von Schroeder is also due the conceptions of " leather yield " (R)
and " degree of tannage " (D), which provide much information as to
extent and nature of the tannage, which is otherwise only obtainable
from the percentage figures.
The " leather yield " (R) of a leather represents the number of parts
of air-dry vegetable tanned leather which have been derived from ico
parts of hide substance.
Example : A leather in the dry condition contains 450 per cent, of
hide substance : —
R : 100 :: lOO : 45.
^, Ti 100 X 100 ^^^ ^
then, R = = 222-2.
45
The "degree of tannage" represents the number of parts of tannin
fixed by 100 parts of hide substance.
Example : A leather in the dry condition contains 45 per cent, of hide
substance and 30 per cent, of tannin (which cannot be washed out) : —
D : 100 :: 30 :45.
then, D = -^^^^30 ^ ^^.^^
45
According to von Schroeder and Paessler, D in most leathers is
essentially below 100, although with very thorough tannings with
^ Dingl.polyt.J., 1893, 287, Parts II, 12, 13 ; Collegium, 1905, p. 340.
502 LEATHER
strong liquors leathers are produced which reach and even exceed this
limit. Very much higher figures are reached by English sole-leather
tanners. (Procter.)
Estimation of Sugar. — The sugar content is only estimated when
the loss in washing is very considerable, and when the non-tans exceed
the tans to such an extent that weighting with sugar is suspected.
Small quantities' of sugars, derived from the tan liquors, can be found
in most leathers ; according to von Schroeder, the average sugar
content of unweighted leathers is about 025 per cent, and may rise as
high as 2-0 per cent.
Leather tanned largely with myrobalans may somewhat exceed
this figure. (Procter.)
In avowedly weighted leathers it maybe anything from 2-16 and
more per cent.
P'or the estimation of sugar the following solutions are required : —
r. Copper Sulphate Solution, containing 69-2 g, of purest copper
sulphate per litre.
2. An Alkaline Solution of Rochelle Salt, containing 346 g. of
Rochelle salt and 250 g. of potassium hydroxide per litre.
3. Lead Acetate. 300 g. of lead acetate are thoroughly ground up
with 100 g. of pure litharge and about 50 c.c. of water, and heated
on the water-bath until the paste has become white, further small
quantities of water being added if necessary. The mass is transferred
to a litre flask, cooled, filled up to the mark, and after standing for some
time, filtered.
4. Sodium Sulphate Solution. It is essential that this solution
should be of equivalent strength to the lead acetate solution.
To carry out the sugar estimation, 400 c.c. of the extracted solution
(derived from the "washings") arc evaporated to 100 c.c, which is
consequently equivalent to 8 g. of leather. These 100 c.c, are trans-
ferred to a dry vessel, the tannin precipitated with 15 c.c. of basic
lead acetate solution, and allowed to stand, with frequent shaking,
for fifteen minutes, and then filtered through a dry filter into a dry
flask (the filtrate must be free from tannin). To 50 c.c. of the filtrate
Q y Co
(representing —= yG^^y g. of leather) are added 5 c.c. of the sodium
sulphate solution, and the precipitate, after it has thoroughly settled,
filtered through a dry filter. Of this filtrate 40 c.c. (representing
^^-^^ — ^ = 2-645 g- o^ leather) are used for the sugar estimation as
55 ■
follows : — 30 c.c. of the copper sulphate solution, 30 c.c. of the alkaline
Rochelle salt solution, and 45 c.c. of distilled water are poured into a
200 c.c. beaker and heated over a small naked flame to boiling. The
beaker is then placed on a boiling water-bath ready to hand, and the
VEGETABLE TANNED LEATHER 503
40 c.c. of sugar solution added whilst stirring. The beaker is allowed
to remain on the water-bath for exactly thirty minutes after adding the
sugar solution. The precipitated copper oxide is filtered through a
weighed asbestos filter with the help of the pump, then washed with
warm water and, to promote rapid drying, with small quantities of
alcohol and ether. The filter is gently ignited for a short time to
remove traces of organic matter precipitated with the copper oxide,
and then reduced in a current of hydrogen, allowed to cool in the same,
and quickly weighed. The amount of glucose originally present can
be determined by multiplying the weight of copper found by 0-469. In
exact analyses the use of this latter factor is inadmissible, as it is
merely an average figure, and the quantity of sugar equal to the weight
of copper found should be obtained from the special Tables which have
been worked out for this purpose. (See Section on "Sugar," p. 557.)
The total volume of alkaline copper solution and the solutions
added to it should always be 145 c.c.
The above method determines glucose and allied substances but
not cane sugar, or the dextrinous matters found in commercial starch
sugars and molasses. Leather is never weighted with pure glucose,
owing to the expense of "such a method, but with commercial starch
sugars, starch syrup or molasses. To estimate these materials when
present in addition to starch sugar, the following method may be
employed : — 40 c.c. (representing 2-645 S- of leather) which have been
freed from tannin and lead, as mentioned above, are heated on a boiling
water-bath for half an hour with 10 c.c. of dilute sulphuric acid (i : 5) to
invert the cane sugar; after cooling, the solution is neutralised with
sodium hydroxide, made up to 100 c.c, and 50 c.c. of this solution
(representing 1-323 g. of leather) are submitted to a second sugar
estimation, which is carried out in exactly the same way as the first
with the same precautions as to half an hour's boiling. Of the amount
of copper obtained, one half (the other half being represented by the
previous estimation) represents the " invert sugar," the amount of which
can be found by multiplying this value by 0-95.
To assist in the judgment of many leathers, especially those which
have been limed or treated with sulphuric acid, it is in many cases of
interest to determine the contained sulphuric acid (SO3) and lime
(CaO), especially with a view of ascertaining whether the skin has been
properly delimed.
Estimation of Sulphuric Acid and of Lime. — For this determina-
tion 20-0 g. of the powdered leather are brought into a litre flask, with
750 c.c. of approximately i per cent, hydrochloric acid (30 c.c. of
hydrochloric acid of sp. gr. 1-125 ^i''*^ 7^0 c.c. of water), and allowed to
stand for twenty-four hours at 30''-40°. After cooling, the solution is
at once made up to i litre and filtered. For the sulphuric acid estima-
504 LEATHER
tion 250 c.c. of the filtrate are evaporated to dryness, the residue
moistened with 25 c.c. of 10 per cent, sodium carbonate solution (free
from sulphuric acid), evaporated to dryness, carefully incinerated,
and dissolved in just sufficient dilute hydrochloric acid to render the
liquid faintly acid. The estimation of the sulphate is then carried out
as usual.
For the estimation of the lime 500 c.c. of the filtrate are evaporated
to dryness, the residue incinerated and dissolved in dilute hydrochloric
acid. After precipitating the iron, etc., the calcium is determined in
the usual manner.
The sulphuric acid determined as above represents neither the
total content of the leather in SO3 nor the free sulphuric acid present.
In spite of this fact the figure so obtained is of value in judging a
leather by giving some idea as to the extent to which sulphuric
acid has been used in its manufacture. If it is required to know
the true sulphuric content, the estimation can best be carried out by
the Balland-Maljean method as improved by Paessler and Sluyter,^ and
by Arnoldi.-
This method has been much criticised, and has several sources of
error, but no unimpeachable method is known, or perhaps possible.
(Procter.)
According to this method the total sulphates and the combined
sulphates are determined in the leather, and the difference between
them is the free sulphuric acid. 5 g. of the leather are moistened with
a 10 per cent, sodium carbonate solution (free from sulphuric acid) and
a little potassium nitrate, and, after drying at a moderate temperature,
incinerated as completely as possible over a spirit lamp or, better still,
in an electric oven. Brunck recommends the use of cobalt oxide as an
oxygen carrier during incineration ; during the moistening of the
leather with the sodium carbonate solution, I-5-I-8 g. of cobalt oxide
are thoroughly mixed in with a clean platinum wire and then the above
method of procedure continued. The ash is dissolved by the addition
of a little bromine water, and the solution rendered faintly acid with
hydrochloric acid. The sulphuric acid is estimated in the filtrate by
the usual method (total sulphuric acid). A further 10 g. of leather are
incinerated as above, but without the addition of sodium carbonate,
and the sulphuric acid determined in the residue in the same manner
(combined sulphuric acid). The difference between the two values
cannot yet be taken as the free sulphuric acid ; it must be remembered
that in the estimation of total sulphates the amount of sulphur
originally contained in the hide substance has been included. Accord-
ing to Paessler and Sluyter, the error introduced in this manner with a
fat-free leather containing 18 per cent, water is about 01 4 per cent.
* Gerber Zeil., 1901, Xos. 66 and 69. ^ Collegium, 1908, p. 358,
VEGETABLE TANNED LEATHER 505
(reckoned as SO3), rising to 0-17 per cent, on the dry leather substance.
In order, therefore, to obtain the free sulphuric acid content, 0-14 per
cent, should be subtracted from the difference obtained (total sulphuric
acid minus combined sulphuric acid).
In this method it is of importance to know whether the leather
under examination contains aluminium, chromium, or iron sulphate.
If this should be the case, the material in the estimation of fixed
sulphuric acid should be ignited until the sulphuric acid contained in
these salts is completely removed ; in addition, an estimation of the
oxides of the elements must be carried out. The amount of sulphuric
acid necessary to combine with these bases must then be subtracted
from the amount of free sulphuric acid estimated as above.^
A. Wuensch"^ estimates the total sulphuric acid after disintegration
of the leather by means of fuming nitric acid.
According to L. Meunier,=^ appreciable quantities of sulphur are
volatilised in the Ball and -Mai jean method, as described above, which
would otherwise be estimated. He recommends that the leather should
be moistened before incineration with a 10 per cent, solution of
potassium hydroxide and sodium nitrate; o-20 per cent SO.j must then
be subtracted as the sulphiir due to the hide.
Meunier^ recommends that the incineration of the leather in the
estimation of sulphuric acid should take place in a Mahler bomb in an
atmosphere of oxygen under 30 atmospheres' pressure.
A simpler and more rapid method for the determination of
sulphuric acid is that of Procter and A. Searle.^ From 2-3 g. of the
leather are moistened in a platinum basin or crucible with 25 c.c.
of TVyio sodium carbonate solution, evaporated to dryness, and the
mixture thoroughly carbonised at a gentle heat ; the whole of the
organic sulphur is thus removed as volatile compounds. The residue
is pulverised with a glass rod, extracted with boiling water, the solution
filtered through a small ash-free filter paper, which is dried, returned to
the crucible, and the whole ignited till all, or nearly all, the carbon has
disappeared. The crucible is then allowed to cool, the ash treated with
25 c.c. of A710 hydrochloric acid to dissolve any calcium carbonate
present, the whole washed into a beaker with the filtrate of the charred
mass, methyl orange added, and the liquid titrated with 7\7io sodium
carbonate. The total volume of standard alkali used, both before and
after ignition, less the volume of standard acid employed, gives the
content of sulphuric acid.
^ Sulphuric acid may also be introduced by sulphonated tanning materials, sulphated
extracts, and sulphonated dyes, which will be estimated as if free. (Procter.)
^ Wissenschaft. tech. Beilage des Ledermarkts, 1 90 1, p. 1 4 1.
^ Collegium, 1906, p. 15.
■* Ibid., 1906, p. 296 ; J. Soc. Ghent, hid., 1906, 25, 913.
5 Leather Trades Review., 1901, 34, 19 ; J. Soc. Chem. Ind., 1901, 20, 287.
506 LEATHER
Estimation of the Specific Gravity. — A weighed strip of the
sample, 25-30 cm. long and 1-1-5 cm. wide, is placed in a glass tube,
which is graduated to 0-5 c.c. and filled to the mark with mercury, the
strip being pushed under the surface of the mercury with a needle in
such a way that the volume of the leather can be determined to 0-25 c.c.
by the amount of mercury it displaces. The specific gravity is then
calculated in the usual manner.
Another method, which must of necessity be used with all soft
leathers, consists in cutting an exactly square piece of the
leather, weighing, and measuring to o-oi mm. with an accurately
graduated micrometer with a vernier attachment, in all dimensions.
The volume is then calculated, and from this and the weight, the
specific gravit}'. If the leather is to be calculated to its mean percen-
tage of water, the moisture content of the leather must be determined
simultaneously.
Nature of the Tannage. — It is impossible to determine with any
certainty by means of chemical reactions with what tannins the leather
has been treated. The practical tests are dependent on external
characteristics, such as colour, cut, etc., but considerable advances have
recently been made by Stiasny and others.
According to Procter, the use of pine bark in tanning may be
detected by dipping the leather in a concentrated solution of stannous
chloride and hydrochloric acid, which takes a deep pinkish-red colour.
A few drops of the infusion of a leather tanned with valonia turn a
magnificent purple-red colour on the addition of a crystal of sodium
sulphite.
Tannin Penetration Test (Acetic Acid Test). — Every leather
should be tanned through as completely and as evenly as possible.
For the examination a piece of the leather is cut from the strongest part,
viz., the tail end of the butt, and the cross section closely examined.
A sensitive method of testing is the acetic acid test, the leather
being cut from the aforesaid part. This piece is then cut up into
smaller pieces, 1-5 mm. wide and about 4 cm. long, which can best be
accomplished by a machine specially constructed for this purpose, a
microtome leather cutter.^ These strips are placed for exacth* two
hours in 30 per cent, acetic acid (sp. gr. 1-0412). Leather which
is thoroughly tanned through does not change, swells very little,
colours the acetic acid brownish, and appears dark against the light,
or in full thickness brownish-red. Insufficiently tanned leather swells
greatly, and exhibits against the light transparent waxy yellow strips in
the middle.
Test of Strength. — Several appliances have been suggested for the
purpose of testing leathers as to breaking strain (important in belting
^ Supplied by Rlessner, Freiberg.
CHAMOIS LEATHER. CHROME LEATHER 507
and harness leathers), resistance to friction (sole leather) and to cracking
(upper leather). Only those for the estimation of the breaking strain,
which also serve for stretching tests, are used in practice. The same
appliances, as for textiles, ropes, metals, etc., can be used for this
purpose. Fecken-Kirfel in Aix-la-chapelle has a similar machine
specially for testing leather. Of two belting leathers with the same
breaking strain, the better is that with the less stretch. The breaking
strain for a good belting leather should be at least 3 kg. per square
millimetre. An increase in the content of the water or of the fat
generally raises the breaking strain.
It is very important that the pieces to be tested should always be
taken from the same places in the hide. Paessler ^ has carried out
extensive researches on this matter.
Water Absorption Test. — This test is of value in the examination
of sole leathers ; the better such a leather is the less water it should
absorb on immersion. To carry out the test a piece of leather of 20 g.
weight (the moisture content must be determined simultaneously on
another piece) is placed in a flat-bottomed basin and covered with
water ; after some time the piece is again weighed and again placed in
water, and the process continued until the maximum absorption of
water is obtained. By careful observation of the method given
any appreciable extraction which would affect the result can be
avoided. It is absolutely necessary that the water-absorption should
refer to a definite percentage of original water in the leather (according
to von Schroeder the best is one of 18 per cent.); only then are com-
parisons admissible.
(b) Chamois Leather.
Chamois leather- should have a soft and cloth-like feel, and a
certain amount of toughness.
(c) Chrome Leather.
For the last fifteen years leather tanned with chrome combinations
has been of great importance, especially for technical and fancy purposes,
where it finds innumerable uses.
Estimation of Moisture. — This is determined in 5 g. of the leather
in exactly the same manner as with vegetable tanned stock.
Estimation of Mineral Matter.— 2 g. of the leather are heated in a
platinum crucible until the organic material is completely incinerated
(as in the ash determination of vegetable tanned leather). The mineral
1 Collegium, 1909, p. 45 ; /. Soc. Chem. hid., 1509, 28, 615.
2 Cf. von Schroeder and Paessler, Dingl. polyt. /, 1895, 295, 9 ; /. Soc. Chem. Ind., 1895,
14. 759.
508 LEATHER
acids united with chromium, aluminium, and the iron oxides are not
estimated in this way, as they are driven off during the ignition.
Estimation of Chromic Oxide (Cr.O.).— The residue derived from
the ignition is thoroughl}- mixed in a platinum crucible with a mixture
of 60 parts of sodium carbonate, 20 parts of potassium carbonate, and
4 parts of potassium chlorate, and gently heated in the yellow flame of
a blow-pipe, then for fifteen to twenty minutes with the blast, adding
once or twice a small quantity of the above mixture. This mixture is
apt to attack the crucible. The ash can be completely oxidised by
intimately mixing with equal parts of magnesia and sodium carbonate,
and igniting for twenty minutes over a Mcker burner, with occasional
stirring. A mixture of sodium carbonate and sodium peroxide is also
efficient, and after acidification excess of h}drogen peroxide can be
removed by boiling. It is impossible to melt the contents sufficiently
in a porcelain crucible. The cooled melt is dissolved in hot water
and the solution filtered to remove insoluble constituents. The clear
filtrate, in which the chromium is present as chromate, is diluted with
water to 150 c.c, 5-10 c.c. of concentrated hydrochloric acid and 10 c.c.
of 10 per cent potassium iodide solution added, and the whole titrated
with thiosulphate solution (exactly as in the titration for the determina-
tion of the iodine value of fats), i g. of anhydrous thiosulphate corre-
sponds to 0-1603 g. CroO^.
Estimation of Alumina.— If the leather contains alumina, 3 g. are
treated with fusion mixture as above. The melt is dissolved in hot
water and the filtrate of this solution made up to 250 c.c. The chromic
acid in 100 c.c. of the latter is reduced by the addition of hydrochloric
acid and alcohol with continuous boiling, and the chromium and
aluminium oxides precipitated from this solution with ammonia and
treated in the usual manner, to be weighed finally as €^,03+ AI.3O3. In
a further 100 c.c. of the solution the chromium oxide is estimated, as
described above, by titration with A710 thiosulphate solution; the
amount of alumina (Al^Og) is calculated from the difference. The
oxides of chromium and aluminium are usually present in chrome
leather in the form of basic sulphates or chlorides.
Estimation of Sulphuric Acid (SO;) and of Alkalis.— For this
estimation 5 g. of leather, extracted with carbon bisulphide to remove
fat and sulphur, are dissolved in 50 cc. of fuming nitric acid. This
is accomplished at ordinar)' temperatures in twelve to twenty-four
hours, but this time may be greatly reduced by gently warming.
When the leather has in this way dissolved to form a green liquid, the
nitric acid is driven off by repeated evaporation with water. The
residue is dissolved in water, made up to 500 c.c. and, if necessary,
filtered. The sulphuric acid is determined in 200 c.c. of this solution
by precipitation in the usual manner with barium chloride. From
CHROME LEATHER 509
the amount of SO3 found, 0-005 per cent. SO3 must be subtracted
for every i per cent, of hide substance in the leather, as in this
method the sulphur of the hide substance is converted into sulphuric
acid.
The alkalis are determined in another 200 c.c. of the solution. For
this purpose the solution is evaporated to dryness, gently ignited to
destroy organic matter, and the residue extracted with a very dilute
solution of hydrochloric acid. From this solution chromic oxide,
alumina, iron, and calcium oxides are precipitated by ammonia and
ammonium carbonate; the filtrate is evaporated to dryness with the
addition of a few cubic centimetres of dilute sulphuric acid, and the
residue gently ignited to remove ammonium salts, etc. The alkalis
are then weighed as sulphates. If it is required to separate potassium
and sodium salts, which are both usually present in chrome leather, the
separation can be carried out in the usual manner.
Estimation of Chlorides. — 3-4 g. of the leather are soaked in 25
c.c. of a 10 per cent, sodium carbonate solution (free from chlorine),
dried, and then carefully incinerated, which is best accomplished
in a muffle furnace or an electric oven. The ash is completely
extracted with water and .the chloride in the filtrate or in an aliquot
part (the solution to be titrated must be exactly neutralised with nitric
acid) titrated with Njio silver nitrate solution, using a neutral potassium
chromate solution (not more than 3 drops of a 10 per cent, solution) as
indicator.
Estimation of Fat and Free Sulphur. — To estimate the fat, 20 g.
of the leather are extracted in exactly the same manner as vegetable
tanned leather with carbon bisulphide (free from free sulphur) ; from
this solution the solvent is distilled off, so that the fat remains behind
and can be weighed. If the leather contains free sulphur, which is
usually the case with two-bath leathers, but may also occur in those of
the one-bath, it goes over with the fat. In such cases the sulphur must
be estimated and subtracted from the fat. For this purpose the fat is
again dissolved in carbon bisulphide, the solution transferred without
loss to a platinum basin, the solvent completely evaporated off, and the
residue oxidised with red, fuming nitric acid. The resulting solution is
evaporated on the water-bath to remove the nitric acid, sodium carbonate
solution added, and the whole evaporated to dryness. The residue is
carefully ignited to free it from organic materials, extracted with dilute
hydrochloric acid and bromine water, and the sulphuric acid precipitated
in this solution in the usual manner with barium chloride. The quantity
of barium sulphate found is multiplied by 0-135 to give the original
quantity of sulphur.
Estimation of Hide Substance.— This is carried out in exactly the
same manner as with vegetable tanned leathers. Owing to the higher
510 LEATHER
content of chrome leather in hide substance, only 0-5 g. of leather
should be taken for the determination.
Literature.
Paessler, J. — Die Untersuchungsmethoden des lohgaren und des chromgaren Leders,
1904.
Procter, H. R. — Leather Industries Laboratory Book of Analytical and Experi-
mental Methods^ 2nd Edition, 1908.
Procter, H. R. — Leather Chemists' Pocket Book, 19 12.
Trotman, S. R. — Leather Trades Chemistry, 1908.
INK
By O. SCHLUTTIG, Manager of A. Leonhardi's Ink Works, Loschwitz, near Dresden.
English translation revised by C. Ainsworth Mitchell, B.A.
A. GENERAL SURVEY.
Ink may be defined as a liquid medium for producing writing or other
marks upon paper, textile fabrics, glass, metal, or other substances.
Since the raw materials employed in the manufacture of ink also
find an extended use in other branches of chemical industry, it is
unnecessary to describe here methods for their examination, and for this
purpose the reader may be, referred to other Sections of this work.
Moreover, in dealing with so many different kinds of products it is
only possible to give a general outline of the methods of manufacture — ■
the more so since many of the processes are jealously guarded as trade
secrets.
Before describing the methods of testing various inks, it is advisable
to make a general survey over the whole field, dealing chiefly with
those of commercial importance and only incidentally with products
which are little more than scientific toys.
Commercial inks may be classified into the following main groups,
some of which, as is obvious, overlap each other : —
1. Black writing inks, including iron-gall, logwood, and aniline inks.
2. Copying inks.
3. Coloured writing inks.
4. Drawing inks.
5. Printing and lithographic inks.
6. Ticket and stencilling inks.
7. Marking inks.
8. Typewriting inks.
9. Inks for metal, glass, and the like.
10. Sympathetic inks.
They may also be classified in accordance with the character of the
pigment, into : —
I. Inks with a pigment in suspension (e.^. printing inks, liquid
Indian inks, and marking inks).
511
512 INK
2. Inks with the pigment in solution, as in the case of writing,
copying, and most t)-ping inks.
Some inks, notably the modern " blue-black " inks, contain a
" provisional colouring matter," usually an aniline dyestuff, which is
introduced to render the writing sufficiently dark pending the forma-
tion of the final black pigment of iron tannate.
In the case of many of the inks included in the above classification,
the tests must be based upon their suitability for the special purposes
for which they are intended, rather than upon their agreeing with a
definite chemical formula, although in some instances the latter is by
no means negligible.
B. DESCRIPTION OF DIFFERENT CLASSES OF INK.
I. Black Writing Inks.
The earliest writing inks probably consisted of lamp black suspended
in an aqueous solution of glue, and were very similar to the liquid
Indian inks of to-day; and it was not until the Christian era was well
advanced that iron-gall inks gradually displaced the earlier carbon inks.
Even then, the inks were of a different character from the modern
iron-gall inks, since they were made to undergo more or less oxidation
before bottling, so as to produce a certain proportion of an insoluble
iron tannate, which, remaining suspended within the liquid, caused the
writing to appear black immediately.
About the beginning of the last century it was discovered that, as a
rule, unoxidiscd inks gave more permanent writing the formation of
the insoluble black iron tannate then taking place within the fibres
of the paper, instead of being deposited ready-formed upon the surface.
The older form of iron-gall ink, however, still met with a limited sale
under the name of "Japan ink," an example of which is given in the
subjoined Table (p. 517).
The provisional colouring matters which are added to prevent the
writing appearing too pale when first applied to the paper, include
indigo, alizarin, logwood, and aniline dyestuffs. Upon their nature
and proportion in relation to the other ingredients of the ink are based
methods of distinguishing between different inks in handwriting.
Normal Inks.
This is the name applied in Germany to such writing inks as
answer the requirements of the standards fixed by an Imperial Statute
of 1st August 1888 {Gnindstitze fiir anitlicJie Tintc)iprufji7ig).
Official Classification of Writing Inks. — According to these
standards, which arc based upon a quantitative determination of the
NORMAL INKS 513
gallotannic and gallic acids by the method described in Hinrichsen's
^^ Die Untersuchung von Eisengallicstintenl' and upon the methods
described in Schluttig and Neumann's " Die Eisengallustintenl^ writing
inks are officially classified in Germany into the two following classes: —
Class I. Iron -gall inks, which give black writing when dry, and
contain at least 30 g. of gallotannic and gallic acid (derived wholly from
galls) and 4 g. of metallic iron per litre.
Class II. Inks which give black writing, which when dried for eight
days cannot be removed by alcohol and water. The ink must also flow
freely and not be sticky when dry.
Inks of Class I. are suitable for documentary purposes ; those of
Class II. for writing where less permanency is required.
In Hinrichsen's method of determining gallotannic and gallic acids,
the ink is treated with hydrochloric acid and repeatedly shaken with
ethyl acetate in Rothe's extraction apparatus (see section on " Iron,"
Vol. II., p. 9). The united extracts are next shaken in a separating
funnel with successive portions of a semi-saturated solution of potassium
chloride in order to eliminate the iron, and are then evaporated in a
partial vacuum at a low temperature, and the residue dried for an hour
at 105°-! 10°, and dissolved in water. The solution is decomposed with
iodine solution and sodium bicarbonate and left for twenty-four hours
in a closed flask, after which the excess of iodine is titrated with
standard sodium thiosulphate solution. Good results are obtained if
the conditions are closely followed.
According to Schluttig and Neumann {loc. cit.) a "normal" ink
must comply with the following tests : —
1. It must be a clear liquid, capable of filtration and free from
suspended matter.
2. It must flow readily but not too rapidly from the pen, and must
be retained by a properly sized paper.
3. It must keep well in an ink-pot, not becoming mouldy or forming
a skin on the surface, and only gradually yield a slight deposit.
4. It must only give a slight varnish-like deposit on the pen.
5. It must not be too acid, so as to attack a pen too rapidly.
6. It must be free from unpleasant odour.
7. It must not pass through a paper of good quality.
8. It must give writing which is not sticky when dry.
(Speaking generally, coloured writing inks should also comply with
the foregoing conditions.)
In the case of "normal" inks of Class II. the following requirement
is also essential : —
9. It must give writing which is extremely dark after eight days,
and cannot be rendered illegible by twenty-four hours' treat-
ment with alcohol and water,
III 2K
514 INK
Inks of Class II. may have any desired composition, provided they
answer the foregoing requirements.
" Normal " inks of Class I., however, must also comply with the
following conditions : —
10. They must contain at least 6 g. of iron per litre.
11. They must contain sufficient gall substance to give writing
which dries within eight daj-s to an intense black, and then
after treatment for several days with water and alcohol, still
retains a certain degree of blackness.
Iron-gall inks of the present day contain : —
(i) The provisional colouring matter ; (2) gall substance extract
and iron salt, which by interaction yield the true pigment, which, unlike
the provisional colour, should not fade on exposure to light and air ;
(3) added substances, such as gum or mineral acid, to give " body " to the
ink or render it more stable. The provisional colours of " blue-black,"
" green-black," " violet-black " inks and the like are gradually masked
by the oxidised iron tannate ; and, provided the ink is of the right
composition, the writing eventually becomes black, while the temporary
pigment fades away.
The chemical cause of this after-darkening of ink is described in
several books on iron-gall inks, and for the present purpose it suffices
to say that the darkening is a function of the phenolic group in the
gallotannic or gallic acid. Phenolic substances free from nitrogen yield
with iron salts pronounced colorations more or less permanent on paper,
provided that they contain either two free hydroxyl groups in the ortho-
position, or a free hydroxyl and a free carboxyl group also in the ortho-
position towards each other.
Writing done with a good iron-gall ink ought to be completely
"fast" towards the action of air and light, and when dry and fully
developed should also resist the action of water. It has been found,
however, that the colorations given with iron salts by those phenols
which have only two free hydroxyl groups, or one hydroxyl and one
carboxyl group in the (?r///£?-position, are not sufficiently resistant to
water. Sufficient permanency against the action of air, light, and
water appears only to belong to the colorations given by those phenols
which contain three free adjoining hydroxyl groups, and do not contain
any disturbing groups, e.g. the nitro-group.
Hence the conclusion is justified that the characteristic tinctogenic
group in gallic and gallotannic acids is the association of three phenolic
hydroxy Is in the ort]io--^os\\\ox\. A proof that the hydrogen atom of
the hydroxyl group plays an active part in the reaction is afforded by
the fact that the capacity of a phenol to produce stable colorations with
iron salts is lost when the hydrogen atom is replaced by a radicle.
The hydrogen atoms of the benzene nucleus do not take any direct
NORMAL INKS 515
part in the reaction, since they may be entirely or partially replaced
without inhibition of the colour production. At the same time,
such substitution has considerable influence upon the shade of the
coloration. Thus the greater the acidity of the substituting radicle
and the larger the proportion of hydrogen replaced, the paler becomes
the colour.
The carboxyl group of gallic acid does not possess tinctogenic
properties, since the esters give more pronounced colorations than the
free gallic acid itself All substances that possess the same tinctogenic
atomic grouping as gallic and gallotannic acids (viz., three phenolic
hydroxyls in the ^r//^(3-position) may be described as "gall substances,"
while the term "gall contents" may be applied to the proportion of
such substances in an ink. In addition to gallic and gallotannic acids
the following substances may be included among the gall substances : —
Pyrogallol and all its derivatives, in which no substitution of the
hydrogen atom of the three hydroxyl groups has taken place {e.g.,
mono-, di-, and tribromop}rogallol), pyrogallol sulphonic acid, pyro-
gallol carboxylic acid, esters of gallic acid, mono- and dibromogallic
acids and their esters, haematoxylin, etc. A comparison of the intensity
of the colorations given by the different gall substances with iron salts
shows that the colours produced by tannin are among the palest, while
those given by gallic acid and its esters and by haematoxylin are much
darker. An ink which contains merely 4 g. of iron and 30 g. of gallo-
tannic acid does not give black but only grey writing.
Further experiments have also shown that the darker the colours of
the iron gall compounds the greater their " fastness " towards light.
This is a fact of great importance in judging the documentary value of
an ink.
Hence tannin (gallotannic acid) cannot be regarded as the sub-
stance which, beyond all others, is the most suitable for the production
of an ink of documentary value. Other compounds (and not only gallic
acid) would give far better results.
For these reasons it would be advisable to substitute the require-
ments of Condition 11 (p. 514) for the official German standard of
30 g. of gallotannic and gallic acids derived exclusively from galls.
Moreover, it is not possible to ascertain with certainty the origin of the
gall substances in an ink.
Provided an ink contain a sufficient proportion of iron and gall
substances, together with gum, mineral acid, etc., in suitably small
amounts, such ink will possess documentary value.
A good method of ascertaining the value of an ink for this purpose
is to make systematic comparative tests with the sample in question,
and with a standard ink containing a known sufficient quantity of gall
substances and of iron. These tests are described subsequently.
516 INK
New Prussian Regulations. — In the Prussian regulations of
22nd May 1912,^ inks are classified into (i) "documentary" and (2)
"writing inks," the latter being subdivided into (A) "iron-gall inks"
and (B) logwood and dyestuff inks.
(i) Documentary Ink is an iron-gall ink containing at least 27 g.
of anhydrous gallotannic and gallic acids, and not less than 4 g. or
more than 6 g. of iron per litre (ratio 4-5:1 and 675:1). It must
keep at least fourteen days in the inkpot without deposit, etc., must
flow readily, and yield writing which, after eight days' exposure, is not
affected by water, 85 per cent, alcohol, or 50 per cent, alcohol.
(2) Writhig Inks of class A must contain 18 g. of gallotannic
and gallic acids, with at least 2-6 g. but not more than 4 g. of
iron per litre (ratio 4-5: i and 6-75 : i). In other respects they must
answer to the same tests as documentary inks. The inks of Class B
are not officially examined.
The tannin is determined by the ethyl acetate method {supra, p. 513),
the residue being regarded as gallotannic and gallic acids, when
o-i g. thereof absorbs at least 05 g. of iodine,' when left for twenty-
four hours in contact with 25-50 c.c. of standard iodine solution (about
50 g. per litre) in the presence of 2 g. of sodium bicarbonate. If
less iodine is absorbed the ink is not suitable for official purposes.
For the determination of iron the residue left on evaporating 10 c.c.
of the ink is ignited, heated with 1-2 c.c. of hydrochloric acid (sp. gr.
1-124), the solution oxidised with 1-2 c.c. of chlorine water, evaporated
to dryness, the residue dissolved in about 0-5 c.c. of warm hydrochloric
acid, and the solution diluted with about 20 c.c. of water. About
I g. of potassium iodide is then added, and the separated iodine
immediately titrated with Njio thiosulphate solution, the liquid
being meanwhile heated to 55"^ to promote the further separation of
iodine.
The tests of the permanency of the writing are applied in com-
parison with Schluttig and Neumann's standard ink as described on
p. 520.
THE COMPOSITION OF ENGLISH INKS (C. A. Mitchell).
The standards enforced for writing ink in Germany have been
adopted by several other countries. Thus, in the state of Massachu-
setts, U.S.A., all ink used for official purposes must answer to these
requirements.-'
In Great Britain no official standard for ink is published, but tests
are made to see that the ink contains a sufficient quantity of gall
' Ilinrichsen, C7u-»i. Zeil., 1913, 37, 265.
- Infonnalion kindly communicated by Ur Bunnell Ua\ eiiport, Boilon, U.S.A.
ENGLISH INKS
517
substances and Iron, and that the writing done therewith is sufficiently
permanent. The quaHtative tests are similar to those used in Germany,
and are described below.
The increasing use of fountain pens has led to the sale of a
great deal of ink which flows freely from the pen, and drys to a good
black, but which certainly does not contain sufficient tannin (gall
substances) or iron to render the writing permanent against the action
of light and air. An example of an ink of this kind is given in the
subjoined Table.
The proportion of iron to gallotannic acid used by different English
manufacturers shows wide variations, and it would seem that few
attempts have been made to ascertain the correct proportions to assure
the greatest degree of permanency for the writing.
From experiments made by O. Schluttig and G. S. Neumann, and
by Mitchell,^ it appears probable that the insoluble tannate produced
when ink dries upon paper contains about 5-5 per cent, of iron, and
would thus correspond in composition with the iron tannate described
by VVittstein^ and by Schiff.^ It would therefore appear rational to
base the relative proportions of the ingredients of an ink upon the
amounts required to form- this compound, and to avoid any material
excess of either iron or gall substances.
An excess of the former certainly tends to cause the writing to turn
brown, but further work is required to ascertain the effect of an excess
of gallotannic or gallic acids upon the permanency of the writing.
For further details on this question the reader may be referred to
" Inks : Their Composition and Examination" by C. A. Mitchell and
T. C. Hepworth,
The wide variations in the amounts of the constituents of com-
mercial inks is shown in the following Table, which gives the composi-
tion of several of the best known inks, typical of those on the English
market.
Composition of Typical English Writing Inks.
Water.
Total solids.
Ash.
Iron.
Sp. gr.
Blue-black ink .
,, . . •
Japan ink , . . .
Logwood ink
,, ^ . . .
Fountain pen ink
Black (for documents)
Per cent.
96-26
95-54
97-86
95-16
97-52
92-16
Per cent.
3-74
4-46
2'-i'4
4-84
2-48
7-84
0-84
0-62
1-04
1-10
0-42
1-45
0-44
0-37
o'-'io
trace
0-18
0-54
1-021
1-022
1-015
1-014
1 Analyst, 1908, 33, 82. "" Jah'sber. d. Chem., 1848, 28, 221.
3 Ann. Chem, P/iarm., 1875, 175, 176.
518
INK
Other analyses will be found in the Table published by Mitchell,^
who in 1908 found that out of twenty-four commercial samples the
amount of solid matter ranged from i •89-7-94 per cent., the ash from
0-42-2-52 per cent., and the iron in the iron-gall inks from o-i8-i-09
per cent.
QUALITATIVE EXAMINATION OF WRITING INK.S.
The difficulties of forming an opinion upon the value of an ink are
frequently increased by the presence of various dyestuffs and combina-
tions of other substances, and in some cases it may be necessary to
isolate special ingredients by extraction with ether, chloroform, etc.
In any case it is advisable to apply tests to the coloured washes
given by the ink upon paper, and for this purpose the following "stripe"
method enables uniform results to be obtained.
c\m
<^
jS^^
<sy,
U
fe:
1^ h
3T12SS:
^
te
Schluttig's "Stripe" Method.
If the ink is made to flow from a small pipette across the surface of
a piece of paper stretched in a frame which is kept inclined at an angle
of 45°, broad bands or stripes of
colour are produced. The effects
of tests applied to these may be
followed much more readily than
when reagents are applied to the
writing itself.
The writing paper, which must
^ be of uniform quality, is stretched
by means of screws in an iron
frame, which is then fixed at the
proper angle.
The construction of this frame
"^
TT
"ST"
■^
Fio. 63.
is obvious from the diagram shown in Fig. 63.'- It is provided with
a channel at the bottom to catch the excess of ink, whilst the groove,
i\ is intended as a rest for the pipette, so that its point may always be
applied to the surface of the paper at the same angle. The pipette
delivers about 06 g. of ink, which produces a stripe about 6 mm. wide
and 270 mm. in length. Care must be taken to prevent the formation
of air bubbles.
Given parallel conditions, the breadth of the stripe and the amount
of ink it contains will depend upon the degree of fluidity and
adhesion of the ink to the paper. A point that ma}' be borne in mind
in the examination of copying inks is that the greater the copying
^ Analyst^ loc, cit., p. 8 1.
"^ The frame may be obtained from the Mechanische Institut of Oskar Leuner, Dresden.
WRITING INKS 519
power of an iron-gall ink the narrower the stripe. Inequalities and
sources of error due to this cause may be eliminated by diluting the
inks with equal quantities of distilled water.
In the absence of special apparatus comparable colour stripes may
be made upon sheets of Ikistol drawing board inclined at an angle
of 45".
Differential Reactions.
More or less separation of the constituents of an ink may be
effected by letting a drop fall upon thick filter paper, when, owing to
the different degrees of diffusion capacity, the resulting zones will con-
tain a liquid of different composition. Or strips of ordinary filter
paper may be immersed at one end in the ink, with the result that the
liquid as it rises will undergo some fractionation. Test reagents may
then be applied to the different zones. It is preferable to dilute
ordinary writing ink with an equal volume, and copying inks with
three or four times their amount of distilled water before applying this
method of fractionation.
In the case of iron-gall inks the outermost zone will be a light rust
colour, due to a basic ferric salt, and on treatment with solutions of
potassium bisulphate and potassium ferrocyanide will give the Prussian
blue reaction.
Inks prepared from extracts of Chinese or small Asiatic galls,
German oak-apples {Knoppern), dividivi, valonea, oak bark, chestnut
bark, and logwood, as the " gall substance," will show, after the lapse of
one or two days, an outer zone which is either of a light rust colour or
which is tinted with the provisional colouring matter in the ink.
The innermost zone will be blue black, and in the case of inks
prepared from galls or dividivi, will show a margin of characteristic
lines, which will be entirely lacking in the case of the inks from tan
barks or logwood.
Only in the case of sumach, and especially of myrobalans, does the
black tint of the iron-gall compound extend into the outermost zone,
so as to cause the latter to appear dark grey. Ink from myrobalans
shows, between the outer and inner zone, a blue-black line on which is
a light grey band, becoming black towards the middle. Both the
sharp black line and the light grey band are absent in the case of
sumach, and the uniform blue-black inner zone abuts directly upon the
yellowish-green outer zone.
With chrome logwood writing and logwood copying inks the outer
zone is either entirely absent, or, in the case of the latter, is light grey
and is free from iron. On the other hand, all logwood inks give a
characteristic red coloration with sulphuric acid or sodium bisulphate
solution.
520 INK
Similar spotting tests may be applied to the stripes obtained in the
"stripe" method. The presence of an iron-gall ink is indicated by the
gradual darkening of such stripe, while by the use of various reagents
information may be obtained with regard to other colouring matters
in the ink.
The reactions given by inks of different colour and black inks
containing provisional colouring matters are shown in the Tables on
PP- 529-531.
PRACTICAL TESTS OF WRITING INKS.
I. Determination of the Darkening Capacity.
The darkening capacity of the sample of the ink in question is
compared under parallel conditions with that of a standard iron-gall
ink prepared in the laboratory from the following ingredients : — Tannin
(puriss.), 23-4; gallic acid, 77 ; ferrous sulphate, 30-0; gum arable, lO-o;
hydrochloric acid, 2-5 ; and phenol, i-o g., in 1000 c.c. of water.
This ink is prepared by dissolving the tannin and gallic acid in
water heated to about 50°, adding the other ingredients, and diluting
the whole to i litre. After standing for at least four days in a
moderately warm place (io°-i5''), the clear supernatant liquid is
decanted from any slight deposit. Filtration is to be avoided, if
possible, owing to the fact that ordinary filter paper will absorb an
appreciable amount of tannin.
The standard ink thus obtained will have a faint bluish-grey tint,
and must be subsequently coloured so as to match any ink in question.
This is not a difficult matter in the case of " blue-black," " green-
black," etc., writing fluids, but the greatest care is required in preparing
the standard to match an ink that flows immediately black from the
pen. Such inks are usually coloured by the addition of relatively large
amounts of various pigments (usually coal-tar dyestuffs); the propor-
tion added, however, being limited by the injurious effect of an
excessive quantity upon the fluidity of the ink. But, since, for the
purposes of this test the ink is first diluted with an equal volume of
water {vide infra), it is rendered paler for the comparison. Moreover,
the "stripes" may be treated when dry with water and alcohol so as
to extract all soluble pigments, and leave behind only the insoluble
iron-gall compounds, the intensity of the colour of which may then be
readily observed and matched.
In the preparation of suitably coloured inks the following dyestuffs
may be used: — Bavarian blue, D.S.F; Nacarate Red S. (Aktienges.
Anilinfab., Berlin) ; Acid Green VBSPo, and Chestnut Brown
(Oehler).
Thus, for example, inks of medium colour may be obtained by
DARKENING CAPACITY
521
adding the following amounts of these dyestuffs to i litre of the
standard iron-gall ink :-
Blue-black.
Green-black.
Red-black.
Imicediato
black.
Blue dyestuff .
Green „
Red „ . .
Brown „
2-2
1-0
2-5
g.
2-5
g-
2-5
0-5
3-5
By increasing or reducing the quantities of these dyestuffs, or by
mixing the coloured inks together in suitable proportions, any shade
required may be matched.
In using the standard ink it should be borne in mind that it is not
intended to represent the best obtainable sample of ink, but only one
giving the lowest permissible limit for intensity and permanency of
writing.
The tannin for the standard iron-gall ink should be such as is
completely absorbed by hide powder in the usual method of estimation.
The amount of iron is increased from the 4 g. of the official German
standard to 6 g. ( = 30 g. of ferrous sulphate), and part of the gallotannic
acid is replaced by gallic acid in accordance with the equation : —
Owing to its sparing solubility, gallic acid cannot be added in
greater proportion than J-J g. per litre, with the object of causing a
more pronounced darkening of the writing.
In applying the darkening test about 15 c.c. of the ink under
examination are withdrawn by means of a pipette from the bottle, care
being taken not to disturb the contents. The bottle is then corked
again in such a way that it can be opened without shaking, and is
allowed to stand for three days in a moderately warm place (15°). In
the meantime an ink is prepared from the standard iron-gall ink to
match the sample previously withdrawn.
The two inks are then used in the preparation of stripes by the
"stripe" method, both undiluted, and after the addition of an equal
volume of water. The paper is left stretched in the frame until
completely dry, after which it is removed from the frame and left for
eight days exposed to the air and diffused daylight in a moderately
warm place, care being taken to protect it from dust or acid fumes.
The stripes produced by the undiluted ink afford information as to
the fluidity, penetrating capacity, and stickiness, while those given by
the diluted ink are used in the tests of darkening capacity.
Should the stripes from the sample diluted not appear as dark as
522 INK
those from the equally diluted standard ink, after the lapse of eight
days, the former may be rejected as unsatisfactory without the necessity
of applying further tests.
On the other hand, if the stripes from both inks appear of equal
intensity, the paper should be cut into strips about 3 cm. broad, at right
angles to the direction of the stripes. One of these strips is immersed
in distilled water, a second in 85 per cent, alcohol, and a third in 50 per
cent, alcohol. After two days they are withdrawn, dried at the ordinary
temperature, and the relative intensities of colour of the residual stripes
compared. The ink in question cannot be regarded as satisfactory,
unless the stripes on all three strips are as dark as those of the standard
ink.
The object of treating the strips with water and alcohol is to extract
all substances which remain soluble after drying, so that the residual
colour upon the paper affords a measure of the proportion of true gall-
substances in the ink. For, as has already been pointed out, it is
necessary to determine whether the darkening is due solely to sub-
stances which contain three neighbouring hydroxyl groups {i.e. true
" gall-substances "), or whether it is partially or wholly due to those
^;'///f-di hydroxy derivatives and ^;-/'//(;-hydroxycarbox}'lic acids which
also yield colorations with iron salts that may be fixed upon paper.
Experiments have shown that pyrocatechin (catechol) and protocate-
chuic acid will produce colorations which will resist the action of light
but not of water, whereas the colorations given by ^;Y//^-hydroxy-
carboxylic acids are neither fast to light nor to water. Hence the
water test affords a means of distinguishing between the two classes of
compounds.
Acidity (C. A. Mitchell). — At the same time the degree of resistance
offered by the colorations to water gives information as to the acidity
of an ink. The greater the proportion and the strength of the free
acid the more slowly does the writing darken. Any ink which, while
containing a sufficient proportion of gall-substances, is so acid that the
writing darkens insufficiently or too slowly, must be rejected.
Apart from its influence upon the writing, the acidity of an ink is
also of importance from the point of view of its action upon steel pens.
Several of the inks upon the English market give writing that darkens
quite satisfactorily, but at the same time have a very drastic action
upon pens. This high proportion of acid is not essential to the keeping
or penetrating properties of the ink, seeing that in the inks of other
manufacturers of equal repute a much lower acidity suffices.
The determination of the acidity of ink is not always an easy
matter owing to the fact that, even after very great dilution, the dark
colour of some inks prevents the change of colour of any indicator
being seen sharply.
ACIDITY. STABILITY 523
A method that has given good results in the case of very dark
samples, is to heat 5 c.c. of the ink beneath a reflux condenser with
10-20 c.c. of hydrogen peroxide solution until the liquid becomes nearly
colourless. At the same time 5 c.c. of a solution of i g. of ferrous
sulphate and 3 g. of gallotannic acid per 100 c.c. are heated with the
same amount of hydrogen peroxide solution. Both liquids are then
titrated with standard alkali solution with methyl orange as indicator,
and from the difference between the two results the amount of free acid
in the ink may be calculated.
Another practical test is to wash a steel pen with alcohol and ether
and determine its weight when dry. It is then immersed in 20 c.c. of
the ink in a closed flask, and left for a given period (say a week), after
which the pen is washed with water, alcohol, and ether, dried, and
again weighed.
Very pronounced differences may be observed in the behaviour of
different commercial inks in this test. In the case of one well-known
ink the loss in weight amounted to 5 per cent, of the original weight
of the pen ; in another, the loss was less than half that amount.
Sulphuric acid has a more corrosive action upon pens than hydro-
chloric acid, and preference should be given to an ink containing the
latter.
Proportion of Iron. — The amount of iron in an ink is determined
as described above (p. 516), or gravimetrically. If insufficient in
quantity the ink may be rejected without further examination as
unsuitable for documentary purposes. It has already been pointed
out, however, that there must be sufficient tannin to combine with all
the iron.
2. The Stability of the Ink.
A well-made matured ink should keep for at least a year in a closed
bottle without forming any deposit upon the sides, provided that it is
not cooled too much. An ink of good composition, however, will form
such deposits if sent into the trade without having been stored long
enough, or if it is left in a cold place. Hence, the stability tests should
always be applied to a clear filtered portion of the sample. A well-
matured ink ought to keep for at least six weeks when left in a dust-
free place in a flask with a neck 1-2 cm. in diameter, provided that its
volume is not less than 25 c.c, that it occupies at least half the capacity
of the flask, and that the height of the body of liquid is greater than
half its mean diameter.
The decomposition of iron-gall inks is the result of an oxidising
process, which proceeds more rapidly in open than in closed flasks,
and in the latter case only reaches a certain point. The greater the
surface of a given ink exposed to the air, the more rapidly does the
524 INK
oxidation take place. Hence, it c^oes without saying, than in compar-
ing the stability of different inks the conditions must be strictly
analogous.
The following method of applying this test may be recommended : —
About 50 c.c. of the ink, which has previously been left for three
days in a closed bottle kept in a cool place (io"'-i5°), are withdrawn
by means of a pipette, which is introduced into the middle of the
fluid immediately after uncorking the bottle. This sample is rapidly
filtered through the finest filter paper, precautions being taken to
prevent excessive contact with atmospheric oxygen. 25 c.c. of the
filtrate are then transferred to a cylindrical 500 c.c. flask with a flat
bottom, and having a height of 185 mm. and a maximum diameter
of 72 mm. The mouth of the flask is covered with a cap of filter
paper to prevent the access of dust, and the flask itself, containing
ink to the height of about 12 mm., is placed in diffused daylight in a
room at the ordinary temperature, where it will not encounter acid or
ammoniacal fumes.
If, before the lapse of fourteen days, films appear on the surface of
the liquid, or deposits are formed on the walls or bottom of the flask,
the ink must be rejected as unsatisfactory.
An ink which shows a deposit at the bottom of the sample bottle is
not necessarily to be condemned, since, as was pointed out above, this
may merely indicate insufficient storing. Further deposition, however,
in the test sample taken as described indicates not want of maturity-
but progressive decomposition.
The formation of a film upon the surface of the ink is especially
indicative of such decomposition, and any sample forming such a pellicle
should be rejected without further examination.
The deposits upon the walls of the flask never occur without a
simultaneous deposit at the bottom, or the formation of a film upon the
surface. They may be regarded as intermediate in character between
the two other kinds of deposit.
3. The Fluidity and Penetrating Capacity of the Ink and
Stickiness of the Writing.
The simplest way of judging of the fluidity of an ink is to try it with
a pen. But a rough test of its efflux velocity in running from a 50 c.c.
pipette with a narrow outlet will afford means for a numerical com-
parison with a standard ink under the same conditions.
The form of the stripes in the stripe test will also afford information
as to the fluidity. At the point where the pipette was applied to the
paper, the ink will have spread so as to form an oval stain. In the case
of most commercial writing inks this oval will show approximately the
IDENTIFICATION OF INKS 525
same form, and the stripes will have the same breadth ; and as a rule,
it is only the combined writing and copying inks that give stripes
somewhat narrower than those from ordinary writing inks.
When, however, the ink is too fluid, and flows too rapidly from the
pen, it will spread out over the paper with the result that the oval will
be larger in area, and the breadth of the stripe will contract from the
top downwards. The form and breadth of the stripes should therefore
be compared with those of the stripes from the standard ink.
Comparative tests are also made as to the degree of penetration of
both the standard ink and the sample with writing paper of good
quality. The writing should not appear on the other side of the paper.
In the same way the standard ink is used as the basis of comparison
in determining how long the writing remains sticky. Even in the case
of copying inks an actual stickiness should not be perceptible when the
writing is completely dry.
4. Identification of Different Inks.
In testing the identity of two given samples of ink, comparative
determinations may be made of their respective ingredients. As is
seen in the Table on p. 517 the inks made by different manufacturers
vary widely in composition.
Further proofs may be obtained by determining the specific gravity,
the stability and the viscosity of the respective inks, and by comparing
the behaviour of the " stripes " in the stripe test when tested with water,
alcohol, and different chemical reagents.
Their copying power may also be ascertained by pressing the paper
with the stripes for three minutes beneath moist copying paper folded
six times. The test should be made an hour after the stripes have been
made, and again after the lapse of one or two days.
5. Differentiation of Inks in Writing (C. A. Mitchell).
The methods of distinguishing between different inks in writing is
based upon the fact that manufacturers use varying proportions of iron
salt and galls, and add either a different provisional colouring matter or
different quantities thereof
If a particular ink is to be compared with a given piece of writing a
colour scale should be prepared from that ink, consisting of four washes
ranging from the faintest to the darkest possible tone, and, if practicable,
the paper should be left for about a week for the ink to undergo
oxidation.
The scale may then be compared under the microscope with the
526
INK
writing in question, and portions of equal intensity be submitted to
comparative tests.
The following reagents will be found useful for the purpose : —
(i) Hydrochloric acid, 5 per cent.
(2) Oxalic acid, 5 per cent.
(3) Stannous chloride, 10 per cent.
(4) Nascent hydrogen, 50 per cent, hydrochloric acid with zinc.
(5) Bromine, saturated aqueous solution.
(6) Bleaching powder, saturated solution.
(7) Titanous chloride, commercial solution.
(8) Potassium ferrocyanide, 5 per cent, solution acidified with
hydrochloric acid.
The colorations obtained should be compared under the microscope
after five minutes, and again, next day, when dry.
As examples of the differences to be observed in writing done with
various commercial inks, the following results may be quoted from
Mitchell's Table.i
Reactions of English Inks in Handwriting while Moist.
Ink.
HydrocUloric acid.
Oxalic acid.
Stannous chloride.
Nascent hydrogen.
L
II.
III.
IV.
V.
VI.
Green-blue
Grey
Deep violet
Bright blue
Deep blue
Red
Green-blue
Light grey
Red-violet
Bright blue
Deep blue
Pink violet
Blue-violet
Grey
Violet
Bright blue
\'iolet
Blue-black
Violet
Pale pink
X'iolet
Bright blue •
Violet-blue
Pink violet
Ink.
Bromine.
Bleaching powder.
Titanous chloride.
Acifiilied potassium
ferrocyanide.
I.
11.
III.
IV.
V.
VI.
Deep violet
Little action
Violet-black
Dark purple
Slight bleaching
Surface bleaching
Greenish
Slight bleaching
Yellow on violet
Slight bleaching
Surface bleaching
11
Dirty green
Light orange
Deep maroon
Green-grey
Nearly black
' Maroon
Green-blue
Green-black
Deep violet
Dark blue
Deep green-blue
Violet-black
It is possible, care being taken, to test characters of equal intensity, to
distinguish between v/riting that has been done several years, and that
which has been done comparatively recently with the same ink.
The more recently applied ink will react much more rapidly and
intensely, especially with acid reagents ; and in some instances a
reagent will cause pronounced smudging, which only gradually ceases
as the writing ages.
1 Analyst, igoS, 33, 84.
COPYING INKS 527
II. Copying Inks.
It is not always possible to make a sharp distinction between
writing and copying inks, since the former will generally yield one or
more copies for a short time after writing.
Commercial preparations sold under the name of " Writing and
Copying Inks" may be regarded as copying inks, provided they will
give a clear copy two days after writing. In other respects they should
comply with the requirements of a good writing ink.
In the case of inks not intended for copying purposes, the amounts
of pigments, ready formed and latent, are usually insufficient to give
copies without leaving the original writing too pale.
Hence the ingredients of copying inks must be concentrated in
proportion to the number of copies required. The statement frequently
found in the text-books that copying inks only differ from writing inks
in containing a larger proportion of hygroscopic and glutinous sub-
stances, such as sugar, dextrin, glycerine, gums and the like, is only
partially true.
In examining copying inks by the "stripe" test, the sample should
be diluted with three or four times its volume of water, the amount of
dilution depending upon the concentration of the ink. The results will
then be comparable with those given by writing inks diluted with an
equal quantity of water.
Tests should also be applied on the lines described under " Writing
Inks" to the residual writing, after the copies have been taken.
The copies should be sharp, should dry rapidly, and not remain
sticky. Otherwise the presence of too much hygroscopic matter in the
ink is indicated.
In testing the copying power the paper with the stripes is placed
beneath moistened copying paper (which is folded six or eight times),
and pressed for three minutes in a copying press.
Similar tests are made after the stripes have dried for twenty-four
and forty-eight hours, and the results will show the rate at which the
copying power of an ink diminishes as the writing dries.
III. Coloured Writing Inks (C. A. Mitchell).
In the earlier kinds of coloured writing inks, various metallic
pigments such as verdigris, or vegetable dyestuffs such as indigo,
logwood and madder, were used. Or, in some cases, animal products
such as the juice of the mollusc {jnurex) or cochineal were employed.
The discovery of the aniline dyestuffs, however, led to a gradual change
in the manufacture of coloured inks, and the older, and, in many cases
528 INK
more permanent pigments, are now only used to a limited extent, and
then usually in association with aniline dyestuffs.
The relative degree of permanency of the older pigments is shown
by the results of the experiments of Russell and Abney.^ The aniline
dyestuffs are, speaking generally, very fugitive, and cases are on record
where writing done with aniline inks has become illegible in six
months.
In some respects, however, they are more resistant to the action of
chemical agents than the black iron tannate formed in iron-gall inks.
On this fact depend some of the tests for distinguishing between black
inks containing different provisional pigments {cf. p. 529).
Among the aniline dyestuffs suitable for use as coloured writing
inks are the following products (BASF) : —
Red: eosin, erythrosin, and phloxin ; ponceau scarlet; cotton
scarlet.
Green : neptune green, SG ; light green, SF (yellowish) ; light green,
SF (bluish) ; diamond green, G and B.
Blue : indigo carmine ; soluble blue, T.
Violet : acid violet, 4 BL.
Yellow : fast yellow ; tartrazine.
Solutions containing from 1-5-3 P^^ cent, of these dyestuffs )'ield inks
which flow well, and are thus particularly suitable for stylographic pens.
Tests for Coloured Inks.
The following Tables show the reactions given by different groups of
typical coloured inks, and by iron-gall inks containing dyestuffs to give
the respective provisional colours. To apply the reactions the inks are
diluted in each case with an equal volume of water, and a series of stripes
prepared by the " stripe method." These are allowed to dry for at least
a day, exposed to pure air, and are then tested with a drop of the
respective reagents, the alterations in colour being recorded immediatel)',
and also after the lapse of twenty-four hours.
I. Blue and Blue-black Inks.
(i) Soluble Prussian blue, from 0-3 per cent.
(2) Sodium indigo-sulphonate, o-i percent.
(3) Bavarian blue, DSF, i-2 per cent.
(4) Methylene blue, 0-5 per cent.
(5) Blue-black ink (p. 520).
1 Report to Science and Art Depart., 1888.
TESTS FOR COLOURED INKS
529
Sodium hydroxide,
2-5 per cent.
Sulphuric aci<l,
5 per cent.
Oxalic acid,
1-5 percent.
Sodium carbonate,
5 per cent.
1. Immediately
After 24 hours .
2. Immediately .
After 24 houis .
3. Immediately
After 24 hours .
4. Immediately .
After 24 hours .
5. Immediately .
After 24 hours .
White
White, with yellow
edge
Yellow
White, with yellow-
edge
Brown
White, with yellow-
edge
Violet
Green-blue, with
green edge
Brown
))
Unchanged
Darker blue
Unchanged
White
Darker blue
))
Lighter blue
White, witli
green edge
Lighter blue
Grey-blue
Unchanged
Darker blue
Unchanged
White
Darker blue
>>
Lighter blue
Lighter blue
n
White
Lighter blue
Light grey-blue
Black-blue
Light yellow, with
green edge
Light blue
Green-blue
Brown-blue
Brown
Sodium bisulphate,
5 per cent.
Sodium sulphite,
5 per cent.
Potassium oxalate,
5 per cent.
Stannous chloride,
5 per cent.
+Hydrochloric acid,
5 per cent.
1. Immediately .
After 24 hours .
2. Immediately .
After 24 hours .
3. Immediately
After 24 hours .
4. Immediately
After 24 hours .
5. Immediately
After 24 houis .
Unchanged
Darker blue
Unchanged
White -
Darker blue
Lighter blue
1)
Light blue
))
Violet blue
White to light
grey
Lighter blue
White
n
Lighter blue
Light blue
Red-grey
Brown
Light grey
White
Unchanged
Light blue-grey
Unchanged
Light blue-green
Lighter blue
Light blue
Unchanged
Brown
Unchanged
White
Unchanged
Darker blue
White
Light blue
Grey-blue with
green edge
II. Green and Green-black Inks.
Ammonia solution,
5 per cent.
Sodium hydroxide,
2-5 per cent.
Sodium carbonate,
5 per cent.
Sodium sulphite,
5 per cent.
6. Immediately .
After 24 hours .
7. Immediately .
After 24 hours .
8. Immediately
After 24 hours .
White
Light green
Light green
Green-brown
u
While
White, with yellow
edge
Light green
White, with yellow-
edge
Brown
11
Lighter green
White
Lighter green
Light green
Brown-green
Brown
White
1)
Light green
Pale green
Grey-green
Brown
Borax,
5 per cent.
Nitric acid,
5 per cent.
Sulphuric acid,
5 per cent.
6. Immediately
After 24 hours .
7. Immediately
After 24 hours .
8. Immediately
After 24 hours .
Light green
White
Unchanged
Lighter green
Grey-brown
Brown
Light green
White, with grey edge
Light yellow-green
White, with grey-green edge
Light blue-green
Grey-bl'-e
Light green
White
Light yellow-green
White, with yellow edge
Light blue-green
Green-blue
III
2 L
530
INK
(6) Acid green, i-2 per cent.
(7) Malachite green, 0-2 per cent.
(8) Typical green-black ink (p. 521).
III. Red and Red-black Inks.
(9) Nacarate, S, 0-5 per cent.
(10) Fuchsine, F, o-2 per cent.
(11) Eosin, A, 1-5 per cent.
(12) Carmine, 1-65 per cent. + ammonia 07 percent.
(13) Typical red-black ink.
Sodium hydroxide,
Sulphuric acid,
Oxalic acid solution, 1
2*5 per cent.
1-5 per cent.
1-5 percent.
9. Immediately .
Yellow-ofrey
Unchanged
Unchanged
After 24 hours .
White, with grej'-red edge
Grey-red
Light grey-red
10. Immediately .
Light red
Light grey
Unchanged
After 2i hours .
Pale red
AVhite
Light blue-grey
11. Immediately .
Yellow red
Light yellow
Yellow
After 24 hours .
White, with orange-red
«)
»»
12. Immediately .
Red-grey
Unchanged
Unchanged
After 24 hours .
White, with dark red edge
Brown-red
13. Immediately .
Grey-red
Liglit red
Light red
After 24 hours .
Brown
>i
n
Sodium carbonate solution,
Sodium bisulphate,
Stannous chloride and
5 per cent.
5 per cent.
hydrochloric acid.
9. Immediately .
Red-grey
Unchanged
Unchanged
After 24 hours .
)i
Light red
Bright grey, with violet edge
10. Immediately .
Unchanged
Red-grey
White
After 24 hours .
Light blue-grey
White, with dark green edge
11. Immediately .
Yellow-red
Yellow
Light yellow
After 24 hours .
i»
))
n
12. Immediately .
Red-grey
Unchanged
Unchanged
.After 24 hours .
n
13. Immediately .
Brown
Light red
Light red
After 24 hours .
n
II
White, with red edge
IV. Violet and Bro-wn Inks.
(14) Methyl violet, 0-3 per cent.
(15) Chrome logwood ink, containing 2 per cent, logwood extract,
0-3 per cent, of potassium chromate, and 2 per cent, of sodium
carbonate.
(16) Tungsten ink, containing 4-5 per cent, of logwood extract, 1-56
per cent, of sodium tungstate, 0-4 per cent, of tartaric acid, and
0-03 per cent, of salicylic acid.
(17) Logwood copying ink, containing 8 per cent, of logwood
extract, 2 per cent, of aluminium sulphate, 0-5 per cent, of
TESTS FOR COLOURED INKS
531
oxalic acid, 4 per cent, of ammonium oxalate, i per cent, of
glucose, 0-5 per cent, of potassium bichromate, and 0-15 per
cent, of salicylic acid. Dries violet-black.
(18) Alizarin, 2-5 per cent, and ammonia solution, i-o per cent.
Dries brown.
Ammonia solution,
5 per cent.
Sodium hydroxide,
2-5 per cent.
Sulphuric acid,
6 per cent.
Sodium sulphite,
5 per cent.
14. Immediately .
After 24 hours .
15. Immediately .
After 24 hours .
16. Immediately .
After 24 hours .
17. Immediately .
After 24 hours .
18. Immediately .
After 24 hours .
Unchanged
Light violet
Unchanged
»i
Red-blue
Violet-black
Blue
Violet-black
Dark red
Violet
Light grey
Light yellow
Grey-yellow
Grey-violet
Grey-yellow, with
brown edge
Brown, with blue
edge
Grey-yellow, with
brown edge
Blue, with red edge
Light brown, with
dark edge
Light green
Yellow-grey
Grey-red
Grey-red, with
dark red edge
Red-violet
Dark red
Yellow-red
1)
Light yellow
Light violet
Unchanged
Light grey
Light yellow
»f
Grey-?iolet
Light grey
Violet
Dark red
-
Borax,
5 per cent.
Copper sulphate,
5 per cent.
Stannous chloride and
hydrochloric acid.
14. Immediately .
After 24 hours.
15. Immediately .
After 24 hours .
16. Immediately .
After 24 hours .
17. Immediately .
After 24 hours .
18. Immediately .
After 24 hours.
Unchanged
Lighter violet
Unchanged
Light grey
)»
))
Blue
Light violet
Red-brown
Dark red
Unchanged
Violet
Unchanged
11
Blue-black
Dark grey-blue
Blue-black
Brown
»»
Light grey-blue
White, with green edge
Grey-violet
Light grey-red, with dark red edge
Red-violet
Dark red
Red-violet
Dark red
Yellow
V. Black Inks.
Sodium
hydroxide,
Sodium
carbonate,
Sulphuric
acid,
Sodium
sulphite,
stannous
2-5 per cent.
26 per cent.
5 per cent.
5 per cent.
19. Immediately .
Brown-red
Grey-violet
Dark blue
Yello'vish red
Dark blue
After 24 hours .
Red-grey, with
dark red edge.
Grey-red
Dark blue, with
violet edge
Light brown
II
20. Immediately .
Light grey
Violet-grey
^ ^'■^X
Violet-grey
Blue-grey
After 24 hours .
))
jt
Grey-blue
II
11
21. Immediately .
Brown
Brown
)»
Brown-violet
II
After 24 hours .
}f
)»
1)
Brown
Grey-blue
22. Immediately .
Green-blue
Bluish-green
Light grey
Unchanged
Grey-yellow
After 24 hours .
Yellow-grey
i»
Light yellow-
Brown
II
23. Immediately .
Unchanged
Unchanged
grey
Unchanged
Unchanged
Unchanged
After 24 hours.
))
>i
))
II
11
III
2 L2
532 INK
(19) Black ink containing i-2 per cent, of Bavarian blue, 0-3 per
cent, of acid green, 1-5 per cent, of chestnut brown. Flows
blue-black and dries grey-black.
(20) Xigrosine ink, containing 125 per cent, of nigrosine.
(21) Typical iron-gall ink.
(22) Vanadium ink containing 10 per cent, of tannin, and 0-4 per
cent, of ammonium vanadate. Dries grey-green.
(23) Carbon ink containing 10 per cent, of lampblack, 6-5 per cent,
of shellac, and 6-5 per cent, of borax.
None of the foregoing inks resisted the action of sodium hypo-
chlorite, with the exception of No. 23, the pigment of which consisted
of lampblack. All the others were immediately bleached.
The reagents mentioned in the preceding Tables have only been
selected as illustrative examples. Obviously many others might be
used, and in special cases prove more characteristic.
IV. Drawing Inks (C. A. Mitchell).
The inks specially prepared for the use of artists include solid and
liquid preparations of Indian Ink and of sepia, and the so-called black
and coloured " waterproof inks."
Indian Inks.
These consist of the finest lampblack thoroughly incorporated with
glue, and preserved by the addition of an antiseptic aromatic oil. The
quality depends chiefly upon the fineness of 'division of the lampblack
and the thoroughness of its incorporation with glue, and considerable
differences may be observed between different commercial samples in
this respect.
The following Table shows the composition of four kinds of Indian
ink arranged in descending order according to their quality and
price : —
Indian inks.
Water.
Carbon in
insoluble residue.
Nitrogen in
residue.
Nitrogen in
original ink.
Ash.
I.
II.
III.
IV.
Per cent.
8-16
7-20
9-93
9-40
Per cent.
53-90
52-53
49-64
57-04
Per cent.
0-0
Per cent.
7-74
4-87
7-26
6-84
Per cent.
4-08
3-69
4-96
4-01
DRAWING INKS 533
The practical tests to be applied to solid Indian ink include
estimations of its solubility, covering power, and blackness of pigment.
For this purpose, o-i g. of the sample is powdered, and mixed
with 10 C.C. of cold water, and a note taken of the time required to
colour the liquid.
The rate of sedimentation of the carbon after complete incorporation
of the ink and water should also be observed.
In testing the tinctorial value, either the liquid inks may be applied
in successive washes with a pelt brush to Whatman paper pinned upon
a slanting board, or Schluttig's stripe method may be used.
In the case of cheaper grades of ink, the washes will be found to be
paler and to show coarse particles of carbon which produce streaks,
while more washes are required to obtain opacity.
The liquid preparations upon the market are prepared from the
broken, unsaleable fragments of the solid sticks. They may be
examined by similar methods.
Sepia.
The pigment known as sepia is obtained from the "ink-sac" of the
cuttlefish, Sepia officinalis, and other species of Cephalopoda. The dried
ink-sacs are powdered and extracted with boiling sodium hydroxide
solution and the pigment precipitated with hydrochloric acid, and
washed and dried at a low temperature. It is sold in the powdered
condition, or incorporated with a binding material into cakes.
It contains an amorphous acid, termed sepiaic acidy which contains
12-3 per cent, of nitrogen.
Some of the commercial samples of sepia contain a certain propor-
tion of lampblack. The proportion of the latter may be estimated by
treating the powdered sample with boiling water and examining the
insoluble residue. In the case of pure sepia it will contain a large
proportion of nitrogen, and will leave over 3 per cent, of ash on ignition.
Lampblack preparations, on the other hand, give an insoluble residue
consisting of nearly pure carbon, and containing only traces of nitrogen
and mineral matter.
In comparing different samples of sepia attention should be given
to its covering power and to the intensity of the pigment, as described
under " Indian Inks."
Sepia, though commonly looked upon as a permanent pigment, has
been shown by experiments of Russell and Abney ^ to fade materially
after long exposure to light and air.
' Loc. cit.
534 INK
Waterproof Inks.
These consist of lampblack or pigments of various colours
dissolved or suspended in a liquid medium, such as an alcoholic solution
of a resin, which on evaporation leaves an insoluble deposit which is not
affected by water.
In examining these the various tests described above may be
applied, and in addition to these the behaviour of the dried ink on
paper towards water must also be observed.
V. Printing Inks (C. A. Mitchell).
Printing inks consist essentially of an insoluble pigment, such as
lampblack, Prussian blue, etc., incorporated with boiled linseed oil, or
other rapidly drying vegetable oil.
Their composition is of subsidiary importance to their behaviour in
practice, and in examining them practical tests should be made of their
covering power, drying capacity, and the intensity of the dried pigment.
In the case of some of the more delicate tints aniline dyestuffs
incorporated with inert substances, such as china clay, transparent
alumina, etc., are employed, and these are characterised by their lack of
permanency on exposure to light and air.
The so-called " double-tone " inks consist of selected mixtures of
pigments of secondary and tertiary colours, and a half-tone block
printed with one of these products will give the effect of two printings,
provided there is sufficient contrast between the light and dark portions.
VI. Ticket and Stencilling Inks (C. A. Mitchell).
The special properties required in this class of inks are rapid drying
capacity and sufficient consistency not to smudge readily.
Many of the stencilling inks contain nigrosine in a suitably
thickened medium, and are quite permanent enough for marking
packing cases, and the like. In fact they resist the action of acid or
acid fumes better than any iron-gall ink, though they smudge on
contact with alkali.
Other inks consist of a basis of shellac and borax, with a suitable
addition of lampblack or ultramarine.
The ticket inks are frequently solutions of aniline dyestuffs with
additions to give " body " and to increase the rate of drying.
In other cases a mixture of lampblack, asphaltum, Venice turpentine,
and turpentine oil is used for this purpose.
A rapidly drying ink used for rubber stamps was found to consist
MARKING INKS
536
of 1-38 per cent, of aniline dyestufif (a mixture of methyl violet and
methylene blue) dissolved in dilute alcohol (60 per cent), and contain-
ing 15 per cent, of glycerol and 8 per cent, of phenol.
The general methods of examining these inks have been described
above.
VII. Marking Inks (C. A. Mitchell).
The juices of various plants have long been used in different parts
of the world to produce permanent marks upon textile materials. For
example, different species of RJms yield a juice which turns black on
exposure to the air, while from the fruits oi Anacardiuvi 07'icntale, "the
Indian marking nut," an ink is prepared which produces an intense
and lasting stain. Natural inks of this kind are employed as varnishes,
and also enter into the composition of certain commercial marking inks.
Of the chemical preparations, those having as their basis a solution
of a silver salt in a readily reducible form are the most widely used.
Many of them consist of a solution of silver tartrate in dilute ammonium
hydroxide, with the addition of a gum to thicken the liquid, and a small
amount of some vegetable colouring matter. On applying heat to the
writing done with such ink, the silver is reduced upon the fibres in the
form of a very stable insoluble black oxide.
Numerous additions to silver marking inks have been patented
during the last fifty years, but not many of these appear to have been
commercially successful, although a small proportion of platinum is still
found in certain preparations.
The following analysis shows the percentage composition of a typical
sample of good marking ink : —
Water.
Free ammonia.
Mineral
matter.
Silver.
Combined
tartaric acid.
Gums.
Platinum.
76-93
4-87
12-30
9-98
6-83
3-94
0-26
Next to silver preparations in commercial importance come the
aniline marking inks, which are usually sold in the form of two liquids
to be kept separate until just before use. By the interaction of these,
aniline black is deposited in an insoluble form upon the fibres of the
fabrics, and produces very permanent marks. One of the portions of
such an ink may consist of a solution of aniline hydrochloride, while the
other may contain copper chloride, sodium chlorate, and ammonium
chloride in suitable proportions.
Similar preparations for the production of indigo blue by the inter-
action of two ingredients have also been put upon the market.
536 INK
For further particulars of the composition of these and other marking
inks reference may be made to Mitchell and Hepworth's " /;/Xx"
The Examination of Marking Inks.
The composition of a marking ink is of less importance than its
behaviour in practice, and in examining a sample systematic tests
should be made to ascertain to what extent it answers to the following
requirements : —
1. It is essential that it shall not injure the fibres of a fabric. In
the case of certain aniline inks the effect of dry heat prior to washing is
to render the marked places very brittle.
The addition of certain metallic oxides to an ink is also likely to
affect the fibres in such a way that if they subsequently come into
contact with a bleaching solution they will readily be disintegrated.^
2. When applied to the fabric, and gently heated or otherwise
developed, the ink must yield marks of full blackness.
3. The marks must not fade on exposure to light or air, or when
washed with soap and water and sodium carbonate. They should also
offer a fair amount of resistance to the action of an acidified solution of
bleaching powder, which they may be liable to encounter in many
laundries.
4. The ink should flow with sufficient ease from a pen and yet not
be fluid enough to " run " upon the fabric.
5. It should keep well in a closed vessel in the dark and not yield
an excessive amount of deposit.
VIII. Typing Inks (C. A. Mitchell).
These consist of a soluble pigment such as methyl violet, dissolved
in a mixture of water and glycerol.
There are also black typing inks upon the market which, containing
carbon, offer great resistance to the action of acids, alkalis, and
bleaching solution.
The practical tests should include trials of the suitability of the ink
for its special purpose, and of the permanency of the typed document.
The aniline typing inks are readily smudged by water and are not
permanent when exposed to the action of light and air.
IX. Inks for Writing on Metals, Glass, Etc. (C. A. Mitchell).
Inks for metals usually contain a particular ingredient that will act
upon the metal in question. Thus, an ink for writing on zinc labels
1 Of. Higgins,/. Soc. Cliem. hid., 1911, 30, 1296.
SYMPATHETIC INKS
537
contains potassium chlorate and copper sulphate dissolved in water
and thickened with gum.
A black ink for writing on metal surfaces in general consists of
copal resin, turpentine oil, and lampblack, or vermilion.
Inks for writing upon glass are frequently nothing more than dilute
solutions of hydrofluoric acid.
Others consist of a basis of turpentine oil, shellac, and Venice
turpentine, with lampblack or other insoluble pigment.
The methods of examining these and similar preparations must
obviously include tests as to their suitability for the purpose in question,
and of the permanency of the writing.
X. Sympathetic Inks (C. A. Mitchell).
Although sympathetic inks are in many cases merely curiosities,
they yet may have some commercial importance owing to the fact that
their use has been claimed in numerous patents. For example, a
process has been devised for detecting any tampering with an envelope
by means of steam, the two colourless ingredients of the ink being kept
apart by a layer of dextrin.
The following Table includes some of the more common substances
used as sympathetic inks, and shows the treatment required to render
the writing visible.
Colour.
Ink.
Treatment with
Black or brown -\
Lead acetate
Mercuric chloride
Tannin
Silver salt
A soluble sulphide
Stannous ch oride
A soluble iron salt
Action of light
Blue
Starch
Cobalt nitrate
Iron sulphate
Iodine
Oxalic acid
Potassium ferrocyanide
Yellow . . J
Copper chloride
Basic lead acetate
Antimony chloride
Action of heat
Hydriodic acid
Tannin
Green . . {
Cobalt chloride, with a nickel salt
Potassium arsenate
Action of heat
Copper nitrate
Purple .
Gold chloride
Stannous chloride
Golden .
Sodium gold chloride !
Oxalic acid (10 per cent.)
followed by heat
538 INK
Literature
Allen, A. H. — Commercial Organic Analysis^ vol. v., 191 1. Article: "Ink," by
P. H. Walker.
HiNRiCHSEN, F. W. — Die Untersuchurii^ von Eisengallusiinten, 1909.
Jametel, M. — LEncre de Chine, 1882,
Lehner, S. — Ink Manufacture, 1902.
Mitchell, C. A., and Hepworth, T. C. — Inks: Their Composition and Manu-
facture, 1904.
SCHLUTTIG, O., and Neumann, G. S. — Die Eisengallustinten. Grundlagen zu
ihrer Beurteilung, 1890.
Seymour, A. — Modem Printing Inks, 1910.
END OF PART I.
PRINTED BY
OLIVER AND BOYD
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Lunge, Georg
161
Technical methods of
186?
chemical analysis
1908
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