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SHALE OILS AND TARS

AND THEIR PRODUCTS

DR. W. SCHEITHAUER

TRANSLATED FROM THE GERMAN
BY

CHAS. SALTER

WITH SEVENTY ILLUSTRATIONS AND FOUR DIAGRAMS

LONDON
SCOTT, GREENWOOD & SON

8 BROADWAY, LUDGATE, B.C.

1913

[ The sole rights of translation into English remain with Scott, Greenwood & Son]

D. VAN KOSTRAND COMPANY

NEW YORK

AUTHOR'S PREFACE.

THE present work is intended to depict the production and
utilization of the distillation tars constituting the basis of
several important industries. The chief of these are : The
Scottish Shale Oil Industry and the Saxon-Thuringian Mineral
Oil Industry, the latter forming a branch of the lignite mining
industry of Central Germany. In addition, the production and
utilization of distillation-tar is practised at Messel, near Darm-
stadt, Germany ; and the author desires to express his cordial
thanks to Dr. Spiegel, the manager of the last-named works,
for the detailed description furnished by him on the methods,
etc., employed there.

Bituminous tar is also subjected to dry distillation, to a
smaller extent, in the south of France and in Australia, the
apparatus and processes employed being adopted from the
Scottish industry.

A full description is given of the apparatus of the German
and Scottish industries, and of the methods of applying same,
the author being engaged in the Saxon-Thuringian industry
and having a personal knowledge of Scottish practice, apart
from the abundant literature at his disposal.

Owing to increased official duties, the author regrets to
have been prevented from completing the work himself; but

iii

273388

IV AUTHOK S PEEFACE

he has had the advantage of obtaining as a collaborator Dr. E.
Grafe, whose scientific researches are well known in industrial
circles, and who, in addition to writing the whole of Chapters
x. and xi., prepared Chapter ix. with the exception of the
historical section. For this collaboration the author again
tenders his best thanks.

THE AUTHOR

WALDAU, NEAR OSTERFELD (HALLE), 1911.

TRANSLATOR'S PREFACE.

IN the German original the chief products of the distillation of
both Shale. and Lignite are classed as "Tar," and though, in
the case of Shale this is not strictly correct, it has been consid-
ered desirable to retain this nomenclature to some extent in
the translation, it being understood that the term " shale tar"
is synonymous with " Crude oil ".

CHAS. SALTEK.

LONDON, JANUARY, 1913.

CONTENTS.

CHAPTER I.

PAGE

HISTORY OF THE SHALE AND LIGNITE-TAB INDUSTRY . 1-7

CHAPTER II.
THE BITUMINOUS RAW MATERIALS.

Occurrence . . . . . M 8

Origin 4 10

Properties and Composition .12

Working . . . • , 15

Utilization . . . . . .17

CHAPTER III.
THE PRODUCTION OF DISTILLATION TAR.

A. The Dry-Distillation Process 20

B. The Winning of Lignite Tar . . . . . . . .21

The Retort 21

The Work of the Retort ^.27

The Condensing Plant 28

The Dry-distillation Process .29

The Distillation Plant . 33

C. The Messel Tar Industry 36

The Retorts . 36

The Work of the Retort 39

The Treatment of the Distillation Vapours 40

D. The Recovery of Shale Tar in Scotland 41

The Retorts . . 41

The Work of the Retort 50

The Condensing Plant 50

The Distillation Process . : V ' . . . 50

The Distillation Plant . 51

VI CONTENTS

CHAPTER IV.
THE DISTILLATION PRODUCTS.

PAGE

A. The Tar 52

Lignite Tar . . . " . 52

Shale Tar (Crude Oil) . . 53

Value of Distillation Tars . . . . ' . . \ . . 53

E. The Tar Water (Ammonia Liquor) . . 53

Lignite Tar Water . . . . 54

Shale Tar Water . ... . . . . . . .56

C. Gas . .... . .57

D. The Distillation Residues . . ... . . . .61

CHAPTER V.
THE DISTILLATION OF THE TAB AND TAR OILS.

A. The Distillation Process ... • -•.'• 64

B. Tar Distilling in the Saxon- Thuringian Industry . . • 7 • ''__ *-. 65

The Distilling Apparatus . . . 65

The Distillation Process . . . ;•;••'"• -. ... 69
The Distillation Plant . . . ..'... . . .74

The Distillation Products . . .*w ., 76

The Retorts 79

Products obtained by the Distjllation of Lignite Tar (Diagrams I

and II) . . 78, 79

C. The Messel Distillation Process . ".*•/ .- „ . . .80

Apparatus for and Method of Distillation . . . . .80

The Distillation Products . . . ' . .- . . . . 80

D. The Distillation Process in the Scottish Industry 81

Apparatus for and Method of Distillation . . . .81

Distillation Plant . ... .... '. . . . 83

The Distillation Products 83

Products obtained by the Distillation of Shale Tar (Crude Oil) (Dia-
gram III) . . . . 84

Products obtained by the Distillation of Shale Tar (Crude Oil) by

Classification of the various Oils (Diagram IV) .... 84

CHAPTER VI.
I. CHEMICAL TREATMENT OF THE TAR AND ITS DISTILLATES.

A. The Refining Process 86

B. The Refining Process in the Saxon-Thuringian Industry .... 87

The Agitator 87

The Refining Process . . • . -. . ' . 88

The Chemical Treatment of the Tar . 88

Refining the Tar Products . 89

Treating the Oils before Delivery . .90

The Agitator House . . 92

C. Refining Process in the Messel Industry 92

CONTENTS Vll

PAGE

D. Refining Process in the Scottish Industry 93

Methods 93

Chemical Treatment of the Tar Products 93

II. THE UTILIZATION OP THE REFINERY WASTE.

Uses and Treatment . .. V ' . 94

Recovering the Chemicals . . . .- * . . ,. . ^ . 95

CHAPTER VII.
THE MANUFACTURE OF PARAFFIN.

A. The Manufacture of Paraffin in the Saxon-Thuringian Industry . . 98

The Crystallization Process . . .."'. . - . .„. .:;.., ... . : ::. . . . 98

The Pressing Process . . • . V' • . . . •'.''. . . 100

The Press Plant . '• '. '•• . • '. . ' ? ' . ' . . ':\ :. . 105

The Steam Jet Treatment . ;•- -.- : ' ; '- -. .. ; .' '. 106

Decolorizing the Paraffin . . . . ' 107

B. Manufacture of Paraffin in the Messel Industry 108

Crystallization . , ...._% 108

The Pressing Process . . . -. 108

C. Paraffin Manufacture in the Scottish Industry 109

Crystallization •* • . . . 109

The Sweating Process . . . . . . . . . 109

Decolorizing the Paraffin 112

CHAPTER VIII.
PRODUCTS FURNISHED BY SHALE OIL AND LIGNITE TAR.

A. Products Obtained in the Saxon-Thuringian Industry .... 113

Quantitative Yield .' . . .% 113

The Oils - - . v .. . « 113

The By-Products 119

The Paraffin . . 120

B. The Products of the Messel Industry 122

Yield Obtained from the Tar .122

The Oils . 122

The Paraffin 122

C. The Products of the Scottish Industry . . . ' . . . .122

Yield from the Crude Oil 122

The Oils . . . . . • 122

The By-Products . . .... . . . . .123

The Paraffin . . 123

viii CONTENTS

CHAPTER IX.

CANDLEMAKING.

PAGE

Historical 125

The Raw Materials 127

(a) The Candle Material 127

(b) The Wick.- 130

The Manufacture . . .132

(a) The Moulding Process 132

(6) Finishing . . . .136

(d) Working up Candle Waste .137

CHAPTER X.
CHEMICAL COMPOSITION OP THE TABS AND THEIR DISTILLATES.

A. Lignite Tar 138

Constituents of Lignite Tar (Table) . . . . ,( . . 144-145

B. Shale Tar (Crude Oil) , . .146

CHAPTER XI.
THE LABORATORY WORK.

Testing the Raw Materials - . i . , . 147

Testing the Tars and other Distillation Products . . . . , . . 151

Testing the Tar Oils » . 154

Testing the Reagents used for Refining the Oils and Paraffin . . . 157

Testing the Paraffin 158

Tests Applied in Candle Works . . . • . . . , . " . 159

Testing the By-Products of Tar Distillation . ,. . . . . . 163

CHAPTER XII.
STATISTICS.

A. The Saxon-Thuringian Industry . ' . . . . . . ,. 16&

B. Statistics of the Scottish Shale Industry . ,^ 174

INDEX 177-185

CHAPTEE I.
HISTORY OF THE SHALE AND LIGNITE-TAR INDUSTRY..

WOOD was the first material to be subjected to dry distillation, andL
furnished the earliest known distillation tar, the composition of which
was described by Boyle in his " Chemista scepticus " (1661). As long
ago as the seventeenth century tar was recovered from the dry distilla-
tion of pine on a manufacturing scale in heavily timbered countries*
like Norway and Sweden.

At the same period coal was also put through a process of dry"
distillation. A patent (19 August, 1681) was taken out in England by
Becher for the recovery of pitch and tar from coal ; and this inventor
was the first to produce coke l in addition to coal-tar. Coal is also
known to have been subjected to dry,distillation in Germany about
the middle of the eighteenth century ; but this application of coal did
not attain any general importance until illuminating gas began to be
made from that material early in the last century, and the employment
of coal as a raw material for dye-stuffs became known towards the
'fifties — two great achievements of man's talent for investigation.

Neither of these kinds of tar, however, comes within the scope of
the present work, both of them being by-products, whereas the other
distillation products constitute valuable main products. At the pres-
ent time tar is obtained as the main product of dry distillation by dis-
tilling bituminous lignite and bituminous shale. The distillation tar
obtained from peat is also only, a by-product.

Lignite tar was known, as the result of distillation experiments on
a small scale, about the end of the eighteenth century, Kriinitz 2
having mentioned in 1788 that rock oil could be obtained from Langen-
bogen "earth coal" (meaning lignite) by distillation. For several de-
cades, however, no useful application was discovered for this tar,
though it was occasionally used medicinally.

The discovery of paraffin in 1830 was of the greatest importance
for the utilization of distillation tars ; and consequently the name of
the discoverer of this substance, Carl von Eeichenbach, is closely con-
nected with the history and development of the shale and lignite-

1 This is the correct spelling. " Coak " is first mentioned in Plot's " History
of Staffordshire". According to Erdmann, coke is derived from coquere (to-
cook).

'JE. Erdmann, " Chemie der Braunkohle " (" Chemistry of Lignite"), p. 9..

2 ;\ ; /; :"• *'*/. ; « SHALE OILS AND TAES

tar industry. Carl, Baron von Eeichenbach, was born at Stuttgart on
12 February, 1788, studied at Tubingen, and became manager of
Count Salm's mines and factories at Blansko in Moravia. He died at
Leipzig on 19 January, 1869.

Although other workers, like I. N. Fuchs and A. Buchner, had
previously prepared paraffin, Von Eeichenbach was the first to investi-
gate this substance and to describe its chemical and physical pro-
perties }l and from his statement that " a wick impregnated with it burns
like a fine wax candle, and without smell " it is evident that he even
recognized the great economic importance of paraffin as a candle ma-
terial. Von Eeichenbach gave the new substance the name " paraffin "
(parum affinis) on account of its remarkable insensitiveness to re-
agents. In 1830 he isolated paraffin with a melting-point of 43-75° C.
from wood tar; and, by fractional distillation, he also produced a
volatile oil which he named " eupion," and which apparently corre-
sponds to lignite-tar benzol. The experiments he conducted in a highly
conscientious manner were lauded by the greatest contemporary
chemists. Liebig referred to them in 1833, 2 and one of his pupils,
Ettling, analysed the creosote prepared by Von Eeichenbach, whilst
Gay-Lussac ascertained the chemical composition of paraffin, which
lie fixed as 85*2 per cent C. and 15*0 per cent H.3

Stimulated by the publication of Von Eeichenbach's work on wood
tar, Laurent 4 conducted experiments on the dry distillation of bitumin-
ous shale from Autun (in the south of France), and induced Selligue
to work up the resulting tar. The latter, in conjunction with De la
Haye, then produced tar from this shale on a manufacturing scale, and
iworked it up into light oils, lamp oil, heavy oil, and paraffin (" mineral
wax ") which products were shown by them at the Paris Industrial
Exhibition of 1839. 5 Other distilleries and works for treating this raw
material were established later, and the industry is still in existence
in the south of France. The various producers there recently amalga-
mated to form the Societe Lyonnaise des Schistes Bitumineux du Bassin
d'Autun.6

Early in the last century peat began to be used as a raw material
for dry distillation ; and in the 'forties, Eunge, of Oranienburg, made
candles of the paraffin recovered from peat tar. His distillation pro-
cess, however, was not adapted for use on a large scale, the first to
invent such a process being Eees Eeece7 (1849), who carried out ex-
periments in collaboration with Robert Kane, and took out a patent

li( Journ. f. Chem. u. Phys." (" Schweigger-Seidel "), 69, 436 (18SO) ; 61, 273

2Liebig's " Annalen," 6, 202 ; 8, 216.

3 Poggendorf's " Annalen," 24, 179.

4 " Chemical Technology," Vol. II, "Lighting," p. 213.

8 Hermann "On the Paris Industrial Exhibition," 183G ("Industrie Ausstel-
lung zu Paris"), p. 147.

(iE. Erdmann, I.e. p. 13.

7 Oppler, " Handbuch der Fabrikation Mineralischer Oele " (" Handbook of
Mineral Oil Manufacture "), p. 6.

HISTOEY OF THE SHALE AND LIGNITE-TAR INDUSTRY

for the manufacture of paraffin from peat. A tar-distillation plant was
put down at Kildare (Ireland), and the tar was worked up ; and other
works, using the same process, were also erected for utilizing the ex-
tensive Irish peat mosses.

In the 'fifties the new industry continued to grow in Austria and
Germany ; but it was not found possible to work at a profit in all
cases, and so this method of recovering tar soon fell into desuetude.

Early in the 'nineties, Ziegler restarted the distillation of tar from
the peat of the extensive mosses in the Oldenburg district, using fur-
naces l similar to those employed in the Saxon-Thuringian industry.
Nevertheless the venture proved unprofitable, and had to be aban-
doned, as a failure, in a few years' time.2

The reason was that, as already mentioned, peat cannot be regarded
as a raw material for distillation tar, it being necessary here to use as
main products what are considered by-products in the actual shale-
tar industry. The peat-distilling plants are really coking plants ; and
the utilization of peat was undertaken, from this point of view, at
Ludwigshof (tJckermiinde district), at the close of the last century.
Peat has also been treated by the Ziegler process in Eussia.3

After distillation experiments had been conducted in various coun-
tries with all kinds of raw materials, James Young took up the work
in Scotland. Just as Von Eeichenbach's discovery forms a landmark
in the history of the distillation tars, so must Young's entrance into
this industry be regarded as the second outstanding achievement.
The possibility of recovering tar from bituminous shales and coal by
distillation had long been known in Scotland, and a number of small
distilling plants had been set up from time to time, but had only a
brief existence and were of little importance. It was Young who suc-
ceeded in creating a large industry in the production and treatment of
shale tar in Scotland. The founder of the Saxon-Thuringian industry,
whose name forms the third landmark in this historical development,
will be referred to later. James Young 4 was born at Glasgow in
1811, and was a pupil of Thomas Graham. On the suggestion of
Lyon Playfair, he built in 1848 a refinery for treating the petroleum
obtained from a colliery at Alfreton. Lamp oil, lubricating oil, and
small quantities of paraffin were recovered, and the latter was even
made into candles. At the end of two years the supply of oil ceased,
and Young sought about^for some other raw material for the distilla-
tion process. Numerous specimens of English and Scottish coal were
tried, without success, before he discovered, in the Boghead coal from
Torbanehill, a material which furnished the desired distillation pro-
ducts. Young's process of dry distillation at a low temperature was

^'Zeits. angew. Chemie," 1893, 524.

>JF. Fischer, " Kraftgas" (" Power Gas"), p. 194.

3Conf. Heber On the Industrial Utilization of Peat, " Braunkohle," 8,
pp. 744 et seq.

4 D. R. Steuart, " The Shale Oil Industry of Scotland " (" Economic Geology,"
Vol. Ill, No. 7), p. 575.

4 SHALE OILS AND TABS

patented in England and America ; and in conjunction with Meldrum
and Binney he set up distillation plant at Bathgate in 1850.

During the next ten years a number of distilleries and refineries
were established in various American coast towns, to treat imported
Boghead coal by Young's process, distilling the tar and oils and re-
fining the latter with sulphuric acid and caustic soda. At the same
time distillation plants were erected in Canada, to treat the Albertite
oil shales mined there ; and in 1860, the Lucesco Co. had ten large
rotary distilling furnaces in operation.1 However, from the year
1859 onward, the discovery of abundant supplies of petroleum in
America led to the gradual closing down of the dry-distillation plants,
since distillation tar could not, of course, compete with the new raw
material. On the other hand, owing to the well-known adaptability
of the American, the redistillation and refining plant was modified to
adapt it for treating crude petroleum. This, as shown by Engler,2
explains tbe possibility of the rapid production of lamp oil on the
large scale in America, and also why the largest petroleum refineries
in that country are situated in the chief ports on the Atlantic coast.
The American petroleum industry mounted on the shoulders of the
distillation-tar industry, and — as Steuart rightly says in his previously
mentioned work — James Young may claim to be the father, not only
of the Scottish shale-oil industry, but also of the great American
petroleum industry.

It is quite erroneous to assume, with Miiller,3 that Young's patents
retarded or even injured the development of the shale-tar industry ;
and in fact the services he rendered that industry are proved by its
extremely rapid growth in both Scotland and America. Von Eeichen-
bach,4 whose happy lot as an inventor it was to see his predictions on
the importance or paraffin brilliantly fulfilled, took Young's part
warmly when the latter's patents were contested, and ungrudgingly
recognized Young's services in having raised the shale-tar industry to
a high position.

For about twelve years Boghead coal was distilled in Scotland ;
and then, early in the 'sixties, another well-adapted raw material was1
discovered in bituminous shales. Owing to the local consumption
and the extensive export trade, the deposits of Boghead were almost
exhausted ; but a large number of new works were established to work
the shale seams situated between Edinburgh and Glasgow. After
having garnered the rich fruits of his labours, James Young died, full
of honours, in May, 1883.

The names of Beilby, Henderson, and Steuart may be mentioned
among the technical workers who contributed to the prosperity of the
highly developed Scottish shale-oil industry. Many novel forms of

*E. Grafe, " Braunkohle," 9, p. 424.

2 W. Scheithauer, " Die Fabrikation der Mineraloele " (" The Manufacture
of Mineral Oils "), p. 5.

3 " Zeits. f. Paraffin-, Mineralol- u. Braunkohlenteerindustrie," 1876, p. 42.

4 " Journ. f. prakt. Chemie," 63, 64.

HISTORY OF THE SHALE AND LIGNITE-TAB INDUSTRY 5

apparatus for the distillation of shale and the refining of paraffin are
connected with the name of Henderson, the manager of the Broxburn
Oil Co., Ltd. The author cherishes in grateful remembrance the
cordial reception accorded to himself and friends at Broxburn in 1909,
where they were welcomed, as " German colleagues," by Henderson.

The majority of the numerous works established in the 'Course of
years for the distillation of shale were, however, shut down after a
brief existence. At the beginning of the 'seventies there were still fifty-
one in operation, but a few years later the number had fallen to thirty.
At present shale tar is recovered and worked up by six companies,
further particulars of which will be found in Chapter XII.

Scottish Boghead coal was exported to Germany as well as to
America, and was distilled, on the island of Wilhelmsburg near Ham-
burg, by Noblee & Co., in a works established by a Frenchman of that
name and which had employed Wemyss coal as raw material from 1847
onward for several years. The tar was distilled, and lamp oil and
paraffin were obtained therefrom. The works were subsequently re-
moved to Harburg. A plant for distilling Boghead coal was also
established in 1850 at Ludwigshafen.

At the end of the 'forties, dry-distillation plants were established
in the Ehineland for treating the local coal. The first plant was
built by a French firm, the Societe £es Schistes Bitumineux, and
treated Siegburg coal under the management of H. Vohl ; but the
business was soon transferred to Wisemann & Co. Another works,
the Augustenhiitte, managed in the first place by P. Wagemann, dis-
tilled local lignite at Beuel, near Bonn, on a large scale, the tar being
worked up into lamp oil, heavy oils, and paraffin. Both the workers
mentioned, whose names are repeatedly encountered in* the literature
of the subject, conducted numerous and sometimes costly experiments
for the purpose of improving the distillation apparatus. Vertical re-
torts were tried and experiments made with distillation in vacuo, in
order to make the business profitable. Nevertheless these works —
which moreover were treating an unsuitable raw material— proved un-
able to withstand the onslaught of the newer lamp oils from petroleum,
more especially as the works themselves were damaged by outbreaks
of fire ; and consequently they soon had to be shut down.

Instigated by the press l reports on the great success of the distil-
lation-tar industry in other countries, Scotland in particular, and by
the suggestions on the importance of this industry to the Province of
Saxony, with its extensive deposits of lignite, dry-distillation plants
were started in the middle of the 'fifties in the classic region of the
German distillation-tar industry, namely the lignite district of central
Germany. Without any analytical examination of the raw material —
any kind of lignite being regarded as suitable — small plants were set
up in evej so many places ; but most of these works, destined from
the outset to failure, only lingered on for a few years. Some of them

dialler & Uhle, " Die Natur," 1854, No. 21.

6 SHALE OILS AND TABS

lacked sufficient capital and experienced management. It was not
until a number of pharmacists, such as Grotowsky, Sc-hliephacke, and
B. Hiibner, who, in this instance as in other branches of German
chemical industry, acted as the pioneer of the chemist — took up the
matter from the technical standpoint, that a commencement was made
with the -systematic examination and selection of the raw material.
At the same time a considerable amount of capital was introduced
into the industry by the establishment of two large concerns, partially
the result of the amalgamation of the lignite properties of a number of
small owners. The oldest firm is the Sachsisch-Thuringische Aktien-
gesellschaft fur Braunkohlenverwertung, which was founded in 1885
and built the Gerstewitz mineral oil and paraffin works. Dr.
Schwarz was the first manager, and was succeeded by Dr. Schliephacke.
Shortly after (in 1857) the Werschen-Weissenfelser Braunkohlen-
Aktiengesellschaf t 1 was established, which first confined its operations
to dry distillation, and afterwards (early in 1870) started the Kopsen
mineral oil and paraffin works.

Thus order and tranquillity were finally introduced into this new
industry, and gave promise of a successful issue to the enterprises es-
tablished on a sure foundation.

In 1858, Carol Adolf Eiebeck — who was previously engaged in the
mining department of the first-named company — set up his first plant
for dry distillation, and soon afterwards built the Webau mineral oil
and paraffin works. His name forms the third landmark in the in-
dustry, in which he played — so far as Germany is concerned — a part
corresponding to that of James Young in the Scottish industry.
Owing to their high spirit of enterprise, broad views, and great energy,
they both succeeded in raising their respective industries to a high
position. Riebeck, the son of a miner, was born at Harzgerode on 27
September, 1821, and in 1835 began to work in the mine, rising step
by step until in 1852 he became mine inspector to the Sachsisch-
Thiiringische Co.

With untiring energy Riebeck enlarged his plant, opened up new
mines, built new distilleries, enlarged the Webau works, and founded
two other mineral oil works at Reussen and Oberroblingen-on-See ; so
that, before long, his works exceeded those of any other undertaking
in size.

Among the older technical workers, an important part in the in-
dustry was played by Rolle, who was manager of the Gerstewitz works
and laboured zealously between 1857 and 1860 to improve the process
of dry distillation. He succeeded in replacing the horizontal retorts
by a vertical pattern, the importance of which change will be discussed
later on. Rolle's successor was Vogt, who was followed by Wernecke,

1Gruhl and Mahler, who were already connected with the industry, were as-
sociated in the foundation of this company with Reinhold Sfceckner, who estab-
lished the banking business bearing his name at Halle-on-Saale, which important
concern has ever since been closely connected with the lignite industry of central
Germany.

HISTORY OF THE SHALE AND LIGNITE-TAR INDUSTRY 7

the first to utilize the gases from the retorts for heating purposes, and
assisted in a most praiseworthy manner to place this most valuable im-
provement in the heating of the retorts at the disposal of others.

After the death of Riebeck in 1883, his various works were taken
over by a share company, the A Riebecksche Montanwerke, Halle.
The three mineral oil works were under the management of Krey,,
whose name is well known in connection with the industry. He intro-
duced distillation in vacuo, and patented the process of distillation under
pressure ; and he also succeeded in carrying out Rolle's idea of utiliz-
ing the gaseous products of the distillation processes for the produc-
tion of power.

In 1873 the Waldauer Braunkohlen-Industrie-Aktiengesellschaft
was founded, with Schliephacke as works manager until 1898 ; and
in 1883 the Zeitzer Paraffin & Solarolfabrik was established at Halle
by the amalgamation of two concerns. The first manager of this com-
pany was Krug, who had successfully managed various mineral oil
works in the same industry for a number of years previously.

Full particulars of the dry-distillation works and factories in exis-
tence at the present time will be found in Chapter XII.

Already in the 'sixties, the dry distillation of (Lias) shale had been
carried out at Reutlingen in Wiirttemberg, as described fully by
Dorn.

In Australia, tar has been recovered from the dry distillation of bi-
tuminous shale, and worked up into further products, ever since 1875.

Mention may be made, in conclusion, of the youngest branch of
the German distillation-tar industry, namely the treatment of bitumin-
ous coal in the works at Messel, near Darmstadt, where the working
of the extensive deposits of this raw material was begun in 1885. The
conversion of the mined material into paraffin and mineral oils is carried
on in a large factory erected at the Messel mine.

This deposit was known as far back as the early 'sixties, but the
coal was left unutilized. This is easily explained by the fact that this,
coal embodies the defects of other bituminous mineral treasures, its
high percentage of moisture recalling ordinary lignite, whilst, in common
with bituminous shales, it has a high ash content. Nevertheless, the
accessibility of the material — which lies under a covering only about
13 ft. deep at most — and the known great thickness of the deposit
(about 480 ft.), formed a sufficient inducement to try and overcome
the difficulties in the way of treating the material.

CHAPTEE II.

THE BITUMINOUS HAW MATERIALS.
OCCURRENCE.

THE chief deposits of bituminous lignite are situated in the province
of Saxony, namely in the Halle mining district between the towns of
Weissenfels and Zeitz, and in the vicinity of Halle, Aschersleben, and
Eisleben. In addition to the bituminous material the seams contain
still larger quantities of lignite poor in bitumen. The other extensive
lignite deposits in central and northern Germany and also in the
Bhine district contain no bituminous material or only in such small
proportions that it would not pay to work. The lignite l is deposited
in shallow basins of varying dimensions, and the thickness of the
seams under the cover rock fluctuates considerably. The bituminous
material is surrounded by irregularly deposited strata of non-bitumi-
nous lignite — a condition resulting from its origin. An approximate
indication of a lignite deposit is afforded by Fig. 1 in which I repre-
sents the cover rock, consisting of : —

(a) Surface soil .

(6) Loam ....

(d) Sand ....
\e) Sand with a layer of gravel
(/)Clay . / . .

IJft.

6J „

50 ,,

9* »

83£ ft.

II is the lignite deposit, in which the strata g, i, and I represent the
non-bituminous material, whilst h, k, and m are the bituminous beds.
The total thickness is 30 ft. and 18 ft. respectively, or 48 ft. in all.
Ill is the floor of clay.

The lignite deposits are interspersed with different minerals, those
most frequently observed, in addition to aluminite and gypsum, being
pyrites, marcasite, and occasionally pure silica ; all thoroughly per-
meated with carbon, and only recognizable by their weight and when
burned. Mergelkalk, clay ironstone, alunite, and very rarely sulphur,
phosphorite, and vivianite, are also found.

The precise characterization of the deposits of bituminous lignite

1Conf. Klein, "Die Deutsche Braunkohlenindustrie " ("The German Lignite
Industry"), I, Section 4.

(8)

THE BITUMINOUS EAW MATEEIALS

at Messel is given in Klein's previously cited work on the German

lignite industry, in which the chief geo- ^

logical features are set forth by Dr.

Steuer. Messel lignite is a mixture of

bituminous clay and lignite, the organic

constituents of which are chemically

combined with the mineral matters. The

deposit is a completely isolated one and

appears to be unique in character, so far

as Germany is concerned.

The superficial area of the deposit is
about 240 acres, and the workings will
not extend below the first 80 ft. for a
very considerable time. The lignite is in
beds of varying thickness and containing
varying quantities of fuel. The strata
overlap like the layers of an onion, and
the whole deposit is of hemispherical
form, embedded in an ancient depression
of the surrounding formations. Conse-
quently, a great variety of product, both
in qualities and properties, is obtained
in working.

The bituminous shales of Scotland,1
like the German lignite deposits, are re-
stricted to a small area in the vicinity of
Edinburgh, about five to eight miles in

FIG. 1. — Lignite deposit;
typical section.

width, extending from the northern shores of the Firth of Forth in
a southerly direction for a distance of about sixty miles. It stretches
through the counties of West Lothian and Midlothian as far as the
Pentland Hills. In addition to this main deposit there are other
small basins of shale, for instance in Fife.

The shale beds are 2000 to 4000 ft. below the surface, and vary in
thickness between 6 ft. and 14 ft. They are embedded between cal-
careous sandstone strata, and the most important seams are those of
Fells, Brdxburn, Dunnet, Barracks, and Pumpherston. The working
of these deposits was undertaken in the order given above. Formerly
the largest quantity of shale treated was that from the Fells and Brox-
burn deposits, but at present the Pumpherston and Dunnet seams
supply an equal amount.

The main deposits of bituminous shale in France 2 occur in the
basins of Autun (Saone-et-Loire) and Buxieres-les-Mines (Allier), and
cover an area of about 45,000 acres. There are two distinct seams,
the lower one having an average thickness of 7 to 8 ft., and the upper
one about 40 in.

1 " Memoirs of the Geological Survey, Scotland," " The Oil Shales of the
Lothians " (Glasgow).

- M. G. Chesneau, " Annales des Mines," 1893 (IX), Vol. Ill, 621 pp. ct seq.

10 SHALE OILS AND TABS

A material analogous to bituminous shale, and utilized for the pro-
duction of tar by dry distillation, is also found in New South Wales,1
in addition to which other deposits of bituminous shale have been identi-
fied in Victoria, South Australia, and West Australia. The largest of
these extends over a large area to the west of Sydney, and contains
seams of varying thickness, from a few inches to 6J ft.

Other deposits of bituminous shales occur in French West Africa
and Canada (New Brunswick) in which latter country such shale was
distilled for tar in the past. Specimens of Canadian shale have re-
cently been tried in Scotland, and gave thoroughly satisfactory results,
so that there is some prospect of the industry being revived.

OBIGIX.

According to the recent investigations of Potonie and his pupils,
the old theory, which obtained for a number of years on the origin of
bituminous lignite, as enunciated by Von Fritsch,2 is no longer tenable.
Von Fritsch put forward as a general hypothesis that lignites were not
formed in situ, but were silted up together, the non-bituminous lignite
representing the peatified trees of the tertiary period, and the bitu-
minous lignite the rosin and wax of that vegetation. The silting of
the individual peatified layers at different times may explain the variable
position of the two grades of lignite in the seams, when it is re-
membered that the lighter raw material of the bituminous lignite
would always collect on the top. Potonie and Heinold,3 however, have
advanced a very different hypothesis to explain the deposition of both
kinds, and one that cannot be dismissed as without justification.

The brothers Benhardt found, at the Toma River in the sultanate of
Witu (East Africa), a substance resembling pyropissit, which is the
purest type of bituminous lignite. This material and its origin were
investigated by Heinold, who classed it as pyropissit. Hubner 4 had
previously ascertained pyropissit to represent the transformation pro-
duct of vegetable matter very rich in fat and rosin. Heinold confirmed
this result by his own researches, and demonstrated — on the basis of
the determinations of Heer and Friedrich — that the flora of the bitu-
minous-lignite districts of the tertiary period contained an abundance
of suitable plants and trees for the production of pyropissit. According
to Friedrich, these genera are all still to be found in the monsoon dis-
tricts of India. 5.

The formation of pyropissit, bituminous lignite, and therefore lig-
nite in general, took place in the following manner : —

In the tertiary period, the lignite districts were occupied by extensive

1 " Journ. Soc. Chem. Ind.," 24, pp. 966 et seq.

2 " Verhandlungen des 4 Allgemeinen Deutschen Bergmannstages zu Halle,"
1889 (" Proceedings of the 4th German Mining Diet," Halle, 1889), Scheithauer
(I.e.)

' Braunkohle," a, pp. 357 et seq.

4 " Inaugural Dissertation on the Origin of Bituminous Lignite," Halle, 1903.

5 " Braunkohle," 4, 361.

THE BITUMINOUS KAW MATEKIALS 11

swamps and bogs with a luxuriant subtropical flora. In the absence of
oxygen, the dead plants and trees submerged in the swamps became con-
verted into peat, in the same manner as can even now be observed in
peat mosses.1 The successive generations of new trees and plants
growing in the mosses underwent the same transformation in their
turn, until finally the swamps and mosses became choked up with
more or less peatified material. A gradual accumulation of sand or
clay over this stratum of peat formed the first stage of the formation
of cover rock, protected the material from rotting away entirely, and
established the conditions of formation of a deposit of lignite. This
applies to non-bituminous lignite, whereas the conditions must have
been different in the case of the bituminous type. Potonie and Hein-
old assume that the bituminous-lignite districts were also gradually
peatified lakes with a clay bottom, the water level, however, having
been subject to extensive fluctuations by alternate droughts and rainy
seasons. As already indicated, the submerged vegetable matters would
be converted into peat ; but this fate could not befall the portions lying
dry and exposed to the action of atmospheric oxygen. Of these
portions, the cellulose would be entirely decomposed into water and
carbon dioxide, whilst the fats and wax resins remained intact. In
this way pure pyropissit was formed. If the periods of drought and
submergence alternated too quickly for fll the organic matter to suffer
complete decomposition, a mixture of pyropissit and coal was formed,
such as is found in the bituminous lignite deposits now worked. The
same thing would occur at the points of transition between the forma-
tion of peat and pyropissit, owing to incomplete decomposition through
restricted access of oxygen.

The alternating and variable stratification of the bituminous and
non-bituminous lignites in the individual deposits can now be readily
explained. The alternations of drought and submergence resulted in
the formation of the two kinds in succession and in unequal quantities.
The only point that is peculiar is that this phenomenon of the alternate
peatification and complete destruction of the tertiary vegetable
materials should have been confined to such a limited area as that
represented by the bituminous lignite deposits ; for the bituminous
character of other lignitic deposits is evidence that plants rich in rosin
and wax were also concerned in their formation.

It is necessary to assume that the bulk of the bituminous lignite
was of autochthonic origin, although allochthoaic action may also have
contributed to a minor extent, since the occurrence of silting was by
no means impossible in the tertiary period. In fact, according to
Potonie, ^ transpositions of lignite also occurred here and there during
the diluvial period, which is shown by the presence of northern
flints in the open-cast workings between Streckau and Gaumnitz,

1 Weber, "Die Entstehung der Moore" ("The Origin of Peat Mosses"),
" Zeits. Angew. Chemie," 1905, 1649.
2 " Braunkohle," 3, 270.

12 SHALE OILS AND TAKS

where the lignite deposit has been extensively folded by ice pressure
and is interspersed with glacier drift.

Generally speaking, it may be taken for granted that the lignites
belong to the tertiary system, and the bituminous kinds in particular
to the Lower Oligocene.1

The bituminous shales were formed in a similar manner to the
bituminous lignites, except that in their case the bituminous material
was furnished by the remains of animals as well as plants. The shales
must be regarded as having been deposited in a perfectly quiescent
sea.2 The imprints of marine animals on the Scottish shales indicate
that these shales were deposited in deep water, probably in a quiet
bay abundantly populated with animal life, and therefore with a
luxuriant flora. The remains of dead animals and plants were carried
down with the mineral deposits from the sea water, and in their decay
furnished bitumen. From the highly varying thickness of the bitu-
minous shales, the bitumen content of which alone makes it profitable
to work, it would appear that a large number of marine animals
perished on certain occasions, probably as the result of volcanic out-
breaks, the Scottish shale deposits having been shown to belong to the
volcanic region.

Although Potonie 3 regards such catastrophes as subordinate phe-
nomena in the formation of ooze rocks, he nevertheless does not rule
them out altogether.

As the same author has shown,4 the raw material of the Australian
industry, the bitumen of the kerosene shale, is of vegetable origin and
owes its formation to the oleaginous algae, being a fucoidal coal and
not a true shale.

The concomitant fossils in Messel bituminous coal indicate a joint
animal and vegetable origin.5

PROPERTIES AND COMPOSITION.

The bituminous and non-bituminous lignites won from the seams,
are raised to the surface, and in this condition contain 50 to 60 per
cent of moisture and are very difficult to differentiate except by an
expert. The freshly raised bituminous lignite forms a plastic and
occasionally greasy mass of brownish black colour ; but when dried
is yellow to light brown, with an earthy fracture and dull lustre which
changes to a greasy sheen under the action of rubbing against a
smooth surface. The non-bituminous variety becomes black or light
brown in colour when dried, and its specific gravity is 1/2 to 1*4, as com-
pared with 0-9 to I'l for the bituminous lignite. In contrast to the
former, this latter melts on ignition, and burns with a very smoky
flame.

JE. Erdmann ("Classification of Lignites") " Braunkohle," 6, 394.
'J Carl Dora, " Der Liasschiefer " (" The Lias Shales"), p. 9.

3 " Zur Frage nach den Urmaterialien der Petroleum " (" Origin of Petro-
leum"), p. 355.

4 Ibid. p. 357. 5 According to Dr. Spiegel.

THE BITUMINOUS RAW MATERIALS

This property is exhibited in a special degree by the purest variety,
namely pyropissit, the deposits of which, however, are now completely
exhausted, though it is occasionally found interspersed in small
quantities throughout the seams of lignite.

The most important constituent of bituminous lignite is the bitu-
men,1 which determines its value. The formation of this bitumen has
already been discussed. The bulk of the bitumen contained in lignite
can be extracted by means of solvents,2 like benzol, toluol, ether, ace-
tone, alcohols, carbon disulphide, and carbon tetrachloride.3 The
amount and character of the bitumen recovered in this way depends on
the solvent used. This method of extraction forms the basis of the
technical utilization of bituminous lignite in the preparation of mineral
wax, which will be dealt with later. The purest type of this lignite,,
pyropissit, naturally contains the highest proportion of bitumen.

Numerous analyses have been made of pyropissit, including those
by Schwarz and E. Eiebeck,4 and the more recent researches by
Kramer and Spilker,5 Hiibner,0 and Erdmann.7 Kramer and Spilker,
in addition to sulphur, detected the presence of high-molecular mon-
acid esters and the free acids of same, but no glycerides or polyvalent
car boxy lie acids could be found. Hiibner found two ketones, with the
composition C16H32O and C12H24O and a humic acid containing 8'39
per cent of sulphur. Grafe 8 could only find a far smaller amount of
sulphur (1-68 to 4*9 per cent) in the huimc acids isolated from bitumin-
ous lignite, thus showing that the sulphur content varies considerably
according to the original material.

E. Erdmann 9 analysed pyropissit, bituminous lignite, and the non-
bituminous kind. The results are given in the following table : —

No.

Kind.

Origin.

0(N)
(diffce.).

S
(volatile).

Ash.

Pyropissit.

Kopsen, nr. Weis-

senfels.

71-12

11-63

9-43

0-10

7-72

Bituminous lignite.

Waldau, nr. Oster-

feld.

64-83

7-62

19-18

0-48

7-89

Earthy, non-bitu- |

Waldau, ar. Oster-

minous lignite.

feld.

62-15

6-42

22-11

0-46

8-86

Greppin.

58-36

4-88

23-95

1-41

11-40

On being subjected to dry distillation in the moist condition as

1 Scheithauer (" Lignite Bitumen "), " Braunkohle," 3> 97.

2 Griiffe (" Bitumen and Retinite "), " Braunkohle," 6, 217.
3"Chem. Eng.," 1910, 12, 15.

4 Scheithauer, " Die Fabrikation der Mineralole" ("Manufacture of Mineral
Oils"), p. 18.

5 ' Berichte," 1902, 12, 15.

11 ' Inaugural Dissertation," Halle, 1908.

7 ' Die Cheniie der Braunkohle" ("Chemistry of Lignite"), p. 66 et seq.

8 ' Braunkohle," 3, 242.

9 ' Die Chemie der Braunkohle," p. 72.

SHALE OILS AND TABS

raised from the pit (about 50 per cent of moisture), Nos. 1 to 3 gave the
following yield : —

Tar1
Coke
Gas

32-61

10-33

7-06

18-73
20-83
10-42

8-88 per cent 2
28-88
12-24

The sulphur content of bituminous lignite varies, and is seldom
below 1 per cent in the lignite as raised.

Pyropissit contains only small traces of plant remains, such as
pollen and cell tissue, but in point of ash content it differs little from
bituminous lignite. The ash is partly attributable to the inorganic
constituents of the plants from which the lignite was formed, and in
part to matter deposited from the water of the swamps. The gypsum
and ferruginous matters in the water that subsequently permeated the
lignite deposits, have also contributed to the ash content.

The following basic constituents have been found in lignite ash :
oxides of iron, aluminium, and calcium, and to a smaller extent, of
magnesium, potassium, sodium, and (occasionally) manganese, with
traces of strontium. The acids present include silica, sulphuric acid,
sulphurous acid (with thio-sulphuric acid occasionally in the flue ash),
sulphuretted hydrogen, carbon dioxide, traces of hydrochloric acid,
and (occasionally) phosphoric acid.

As a fertilizer, the ash of lignite has no particular value, though
it loosens the soil in an advantageous manner. The following analysis
of a lignite ash is given by E. Erdmann : —

Calcium sulphide .

Iron sulphide .

Calcium sulphite .

Calcium thiosulphate

Potassium sulphate

Magnesium sulphate

Calcium sulphate

Calcium hydroxide

Lime, combined with carbon c acid anc

Ferric oxide and alumina

Carbon ....

Silica ....

Carbon monoxide and water

silica

0-46 per

1-38

1-12

1-27

1-26

7-65
26-68
15-13
11-85

9-70

1-66
17-79

4-96

100-91

cent.

Messel coal is lumpy and of a semi-clayey character, cuts some-
thing like Dutch cheese, is blackish- green in colour, and exhibits a
conchoid fracture when dry. When exposed to the action of frost and
afterwards thawed out again, it splits up into innumerable sheets as
thin as paper, from which one may conclude that, on account of its
high geological antiquity, and had the contained water been forced out
by pressure, it might have furnished a bituminous shale. The mois-

1 These are laboratory results. On the large scale the yield would be about
60 per cent.

2 As a rule, the yield from non-bituminous lignite is smaller, and is found in
the laboratory to be about 6 to 8 per cent.

THE BITUMINOUS EAW MATEEIALS

ture content runs up to 45 per cent, and the ash averages 30 per cent.
As it thus contains only 25 per cent of combustible matter, its calorific
value is correspondingly low and would not pay the cost of carriage for
heating purposes.

When subjected to dry distillation in the laboratory, an average
sample furnishes : moisture 44 per cent, water of decomposition 6 per
cent, crude oil (lignite tar) 7 '8 per cent, coky residue 36 per cent, gas
6-2 per cent. The water of decomposition contains a considerable
amount of volatile and fixed ammonia salts, together with pyrocatechin
and its homologues. The fixed ammonia salts are combinations of a
whole series of fatty acids. The residual coke contains on the average
21 per cent of carbon, but its ash content is attributable to clay rich
in ferric oxide.

Scottish bituminous shale, or oil shale, is black, brown, or even
grey in colour, the richest in bitumen being the darkest. It is sticky
and of low flexibility, can be scraped, and exhibits a conchoid fracture.
The structure is decidedly foliaceous, especially after distillation. The
specific gravity varies between 1-713 and 1-877. In contrast to bi-
tuminous lignite, the bitumen cannot be even partially extracted by
solvents.1 The average yield from good shale on distillation is : —

Water .
Tar .
Residue

2-68 per cent.
24-31 „
73-00

the last named being composed of 12'5 per cent of carbon and 6O5
per cent of ash. The spent shale from the new-pattern retorts con-
tains far less carbon than that from the older types, namely only
about 3 to 4 per cent as compared with as much as 18 per cent of
carbon in some cases. According to Redwood 2 the residue con-
sists of : —

Carbon

Silica

Ferric oxide

Alumina

Lime

Magnesia

Sulphur

3-61 per cent.
56-49
12-81
22-72

1-77

0-95

1-15

The shales distilled in the south of France give an average yield
of 5 to 6 per cent of tar.

The Australian shale, on the other hand, yields up to 60 per
cent of tar, but this is poor in paraffin.

WOKKING.3

The extent and position of a lignite deposit having been proved by
numerous borings, the method of developing and working depends

:D. R. Steuart, "The Shale Oil Industry of Scotland," p. 5S7.

2" Mineral Oils and their By-products. "

3Vollert, " Der Braunkohlenbergbau im Oberbergamtsberzirk Halle," etc.
("Lignite Mining in the Halle District"), pp. 149 et seq.; Klein, "Die Deutsche
Braunkohleindustrie " (" The German Lignite Industry ") II.

16 SHALE OILS AND TARS

on the relative thickness of deposit and cover rock. ]f this proportion
be 1 : 1 or less, the deposit is worked on the open-cast system, the
cover rock being removed by hand or machinery. Since efficient steam
navvies have been available, the open-cast system is adopted even
where the said proportion rises to 1 : 1^ or even 1 : 2, provided the-
thickness of the deposit is not very small. It is merely a question of
calculation.

The lignite is mostly raised from these open-cast workings by haul-
age inclines operated by chains or ropes ; and only by shaft winding
in workings of no great extent.

Shaft mining is practised when the thickness of the cover rock ex-
ceeds that of the deposit considerably, as shown in Fig. 1. Most of
the bituminous lignite deposits supplying material for dry distillation,
with the exception of a few open-cast workings, are worked in this way,
whereas open-cast is the rule in the Lausitz and Rhenish lignite
districts.

The shafts sunk down to the deposit are for the purpose of winding
and ventilation. The process is a difficult one, especially where quick-
sand strata have to be traversed ; and forms the chief task in develop-
ing a deposit. In the bituminous lignite district, the shafts are rarely
more than 66 yds. in depth, though a few reach 82 yds. or more.

From the bottom of the shaft, main haulage roads (double roads
with two lines of tracks for the pit tubs) are driven transversely through
the deposit in various directions. These roads branch off at right angles
into single-track branch roads, at certain, intervals (depending on local
conditions), these secondary roads running right out to the boundary.
The lignite is won by hewing down the upper part of the seam for a
height of about 13 ft. at the end of the branch roads, and keeping the
opened space clear by means of props and timbers. When the worked-
out space measures 20 to 30 sq. yds. in area, the timbers are withdrawn
and the cover rock is allowed to cave in (subsidence working). The
adjoining pillars of lignite are worked in a similar manner, until the
whole of the lignite has been won. As the deposits are generally
thicker than the 13 ft. mentioned, the fallen roof is allowed to lie and
consolidate for some time, after which the lower lift of the seam is
worked in precisely the same way as the upper one. In some cases
there are even as many as three or four lifts, since many seams are 13 to
18 yds. thick ; and indeed, thicknesses of 80 yds. or more are not un-
common in deposits worked on the open-cast system.

The haulage tubs used in both open-cast and shaft mining are of
wood or sheet iron and hold about 13 to 16 bushels, less frequently 19 to
22 bushels. For short distances these tubs are run by hand labour, end-
less-chain or wire-rope mechanical haulage being employed for longer
distances. In shaft winding, an engine drives a cylindrical rope drum
by means of pinion gearing. Suspended from the rope are the cages
in which the full tubs are raised to the surface and the empties lowered
into the pit again.

Where the distance from the pit to the classifying plant is small the

THE BITUMINOUS EAW MATEKIALS 17

lignite is transported in the tubs or else by belt conveyors, aerial rope-
ways being used for longer distances.

In order to separate the bituminous coal from the non-bituminous,
samples of the lignite obtained during the trial borings must be analysed,
so that the hewers may know whereabouts the bituminous material is
to be found. Assistance in this respect is also afforded by certain
practical knacks, which, however, cannot replace chemical analysis and
control ; and it is important that, so far as is possible, only bituminous
lignite should be sent to the distillation plant.

At Messel, the coal is won by open-cast working, with haulage
roads underneath, the tubs running down by gravitation and being
raised by a system of chain haulage. The haulage devices and ex-
tensive classifying plant are operated in part by shafting driven by-
small gas engines, and in part by electromotors deriving current from*
a central power house served by large gas engines.

The shale beds in Scotland not only vary considerably in thickness,,
but are also situated at different depths, and contain a number of seams.-

Before beginning to work, the position of the shale seam must be^
accurately ascertained by borings. The cores obtained are tested for
the suitability of the material for dry-distillation. The beds are worked! *
either by means of vertical shafts, or else, if the seams pitch, from
adits driven from the surface down to the seam and serving as rope-
haulage roads. The deposit is opened ^p by driving cross headings,
in which the shale is won by blasting so as to bring it down in the
largest lamps possible. For this purpose gunpowder is used, dynamite
being only employed occasionally in damp places. The shot firing
is performed in accordance with well-defined governmental regulations.

The shale is hauled by means of tubs and a ropeway to the distil-
ling plant.

UTILIZATION.

In considering the utilization of bituminous lignite, it is desirable
also to treat briefly that of the other grade of lignite, which contains
only small quantities of bitumen. This non- bituminous or burning
coal is used solely for heating purposes, and is either sold in the con-
dition of " through-and-through " coal, i.e. exactly as it comes from the
mine, or else separated, by screening, into small and large. The large
is again graded for sale, whilst the small is made up into compressed
blocks, shaped like bricks, and prepared by subjecting the moist smalls
to a pressure of 5 to 7 atmospheres in a press. The manufacture is
carried on during the summer, because the finished blocks have to be
dried in the air, and artificial drying machines have not yet proved
altogether satisfactory. These blocks are sold for domestic heating
purposes in the vicinity of the works, being too crumbly to stand any
long carriage by rail.

The production of lignite briquettes forms the main application of
non-bituminous lignite, and one that is increasing every year. These.

1 " The Oil Shales of the Lothians."

18 SHALE OILS AND TABS

briquettes are made by crushing the freshly mined lignite to the size
of peas, followed by drying until the moisture content has been reduced
to 12 or 16 per cent, whereupon the mass is subjected to a pressure of
1200 to 1500 atmospheres, the heat of which operation softens the con-
tained bitumen and binds the particles of lignite to a solid mass. Con-
trary to the practice in making briquettes of ordinary coal, no binding
medium is added. It is evident that this application of the lignite is
due entirely to the bitumen it contains.1

Owing to its high bitumen content the bituminous lignite is un-
suitable for fuel or for the manufacture of briquettes, since in the former
case a portion of the molten fuel would drop through the grate, corrod-
ing the firebars and having only a low-heating effect, whilst in the
second contingency, experience has shown that the briquettes crumble
and fall to pieces in the fire.

For some decades bituminous lignite has been used as a material
for the dry-distillation process ; which process, and the working up of
the resulting lignite tar into mineral oils and paraffin, constitute the
sphere of the Saxon-Thuringian mineral oil industry and will be de-
scribed in subsequent chapters.

A second application of bituminous lignite consists in the recovery
<of its bituminous contents, these being separated from the carbonaceous
portions by the aid of solvents. The possibility of such separation
had long been made known by laboratory experiments ; and the pre-
viously mentioned investigations of pyropissit were based thereon.
The first to recover this bitumen on a manufacturing scale was Von
Boyen, who took out a patent for his process ; '2 and at the present
.time crude bitumen is extracted from bituminous lignite in about six
different works. As a rule the lignite is crushed (but not to dust) and
dried before being extracted ; 3 the only process in which the bitumen
is treated in the damp state in which it is raised from the mine being
that of Frank and Ziegler (" wet extraction "). Benzol is generally used
as the solvent.

The extracted lignite still contains enough bitumen to enable it to
be briquetted ; 4 and it also finds application in fuel.

The crude bitumen thus obtained is usually termed " mineral
wax," although Von Boyen wished to apply this term to the refined
product prepared by subjecting the crude bitumen to repeated distilla-
tions with superheated steam. The crude bitumen is black, whereas
the refined product has a wax-yellow colour. Various methods, some
of them patented, have been introduced for lightening the colour of
the crude bitumen without altering its composition ; a result that
would be of considerable value in connection with its employment and
utilization. So far as the author is aware, however, none of these
methods has been attended with practical or economic success.

1 Scheithauer (" Lignite Bitumen"), " Braunkohle," 3, 101.

2" Zcits. Angew. Chemie," 1901, 1110; Ger. Pat. 101, 373 ; 116, 453.

:i Grafe, " Braunkohle," 6, 219.

J Scheithauer, " Braunkohle," 3, 101.

THE BITUMINOUS RAW MATERIALS 19

Bitumen is of little use as a material for candles ; but on the other
hand it forms in many cases a substitute for Carnauba wax, which it
also resembles in its chemical properties. It is also used as an insu-
lating material, in the preparation of shoe polishes and varnishes, and
as a raw material for phonograph cylinders.

The sale of mineral wax is naturally but small, and there is little
prospect of any considerable increase in the output, which at present
amounts to about 400 to 500 tons per annum.

Since the best grades of bituminous lignite are already exhausted,
and a good quality raw material alone is suitable for the production
of bitumen, the further development of the industry is also restricted
on this account.

At the Messel works, the coal raised is all worked up in the dry-
distillation plant. At one time the output was graded, but now the
whole of the coal is sent to the distillation plant. The yield of tar
varied between 4 and 14 per cent when the grades were distilled
separately ; but that from the through-and-through coal averages about
7-J per cent. Only very small quantities of bitumen can be extracted
from this coal.

The Scottish bituminous shale also is used exclusively as a >raw
material for dry distillation, it being, as already mentioned, impossible
to recover the bitumen by extraction. ^ If the term bitumen were re-
stricted to such constituents as can be extracted from the bituminous
raw materials by solvents, then Messel coal and Scottish oil shale
would have to be excluded from that category. As the author has
previously explained elsewhere,1 the best comprehensive definition of
" bitumen " is the substances which furnish tar when subjected to dry
distillation. The circumstance that cellulose also must be included if
we pursue this theory further, as was done by Brdmann,'2 is no objec-
tion, when it is remembered that part of the tar from lignite is formed
from the ligneous matter. When cellulose is allowed to rot, it decom-
poses in the same manner as in dry distillation, the carbon and hydro-
gen being dissipated as carbon dioxide and water vapour, leaving only
the raw material of tar — bitumen — behind.

The French and Australian shales are chiefly used for the prod ac-
tion of tar, though in the latter country the richest shale is also used
as an adjunct to coal in the manufacture of gas,3 and a portion of the
output is even exported abroad.

1 " Braunkohle," 3, 101.

2 " Die Chemie der Braunkohle " (" The Chemistry of Lignite "), p. 77.
s "The Petroleum Gazette," 1908, No. 4, p. 5.

CHAPTEE III.

THE PRODUCTION OF DISTILLATION TAR.
A. THE DRY-DISTILLATION PROCESS.

To obtain tar from the bitumen of the raw material, the latter must be
distilled. Appliances of highly divergent character have been used for
this purpose at different times ; but the object kept in view in all cases
has been to prevent the decomposition of the bitumen from proceeding
further than was necessary to furnish tar as the main product, and to
obviate the formation of decomposition products of tar.

The most important point is the heating of the retorts ; and experi-
ments must be made to ascertain the most suitable temperature for
ensuring the proper distillation of a raw material in a given apparatus.
If the temperature be too high, the tar vapours are decomposed, more
gas is liberated, and a.portion of the solid hydrocarbons will be converted
into volatile substances rich in aromatic compounds, like benzol and its
homologues, naphthalene, etc. The gases contain an abundance of
free hydrogen and light hydrocarbons. If the distillation temperature
be too low, the bitumen is not completely decomposed, but is carried
over with the tar. The liquid and solid distillation products are then free
from aromatic hydrocarbons, and consist solely of hydrocarbons of the
fatty series, the higher homologues of methane and ethane, whilst the
gases consist mainly of heavy hydrocarbons, like ethylene and acetylene.
Moreover, the residue is far richer in carbon than in the former case.
A properly selected temperature just decomposes the bitumen, without
splitting up the tar any further ; but, of course, this ideal cannot be
uniformly attained in practice. Nevertheless, endeavours should be
made to realize it as completely as possible.

It is also important that the distillation process should be con-
ducted in such a manner that all parts of the raw material are exposed
to a uniform heat in the several stages of the operation. The retort
and the fire for heating same must be so constructed and arranged that
the material is heated gently at first, the temperature being raised
gradually, and finally becoming sufficiently high to decompose the
final traces of the bitumen and convert them into tar. These con-
ditions are thoroughly fulfilled in the modern patterns of retort.

In contrast to the practice in Scotland, the distillation of the raw
material in the Saxon-Thuringian industry is effected without the use
of steam. Towards the end of the 'sixties, Eamdohr tried to employ
steam as an auxiliary in the dry distillation of lignite, using it first

(20)

THE PRODUCTION OF DISTILLATION TAB

in the horizontal retort and afterwards in the vertical pattern.1 The
method, however, did not succeed in practice, and was only used
experimentally for a short time. Eamdohr termed the resulting pro-
duct "steam tar," and it differed essentially from that obtained by
the ordinary dry-distillation process, inasmuch as it contained con-
siderable quantities of bitumen which was protected from decomposing
by the steam, whereas it is the decomposition products that are desired
in this tar.

As already mentioned, steam is used in the Scottish shale industry,
the apparatus being constructed accordingly. This treatment is ne-
cessary, because ammonia is recovered from the aqueous distillate. A
full description will be given later.

In the Scottish industry the process must be conducted in such
a manner that a high yield of ammonia, as well as tar, is obtained
from the shale ; and this result is most completely achieved with
the newest retorts.2

After the distillation process has been completed at a low tem-
perature, steam is allowed to act at a high temperature on the spent
shale.3 This causes the carbon of the shale . to be converted into a
mixture of carbon monoxide and carbon dioxide, whilst the resulting
hydrogen unites with the nitrogen of the shale to form ammonia.

B. THE WINNING OF LIGNITE TAB.

The Betort.

The earliest kind of retort used in the Saxon-Thuringian industry was
horizontal, in the form of a /^^ of cast iron. This pattern was used by

FIG. 2. — Oval horizontal retort.

Vohl and Wagemann,4 who combined sixteen in pairs to form a battery
of retorts. Other shapes, small and low, rectangular and round, were
also occasionally employed.

144 Deutsche Industrie Zeitung," 1878, 322 ; Ger. Pat. 2232.

2 See pp. 44 et seq.

:J"The Oil Shales of the Lothiaus," p. 169.

4Dingler's " Polytechn. Journ.," 135, 138; 139, 216.

22 SHALE OILS AND TABS

B. Hiibner l and Unger 2 selected the oval form of horizontal retort,
which was found the most suitable as best able to resist the adverse
effects of unequal heating, so that this pattern gradually displaced the
others, and held the field until the introduction of the vertical retort.
A longitudinal and cross section of this pattern are shown in Figs. 2
and 3. Its dimensions were : length 8 to 10
ft., width 27^ to 31^ in., height, 14| in., and
thickness of metal (cast-iron) 1 to 1^ in. The
one end a of the retort is closed by the cover b
fastened with bar and wedge, whilst the other
end is fitted with a connection leading to the
FIG. 3.— Cross section of pjpe c for carrying off the tar vapours. The re-
ceiver is represented by d, and the flues by z z.

A large number of such retorts — usually 10 to 12 — were united to
form a battery, heated from the one fire. The retorts were charged by
throwing or pushing in the raw material, so as to cover the bottom of
the retorts with a uniform layer about 4 in. thick. Non-bituminous
lignite was burned on a flat grate, the consumption of fuel being 80 to
100 per cent, by volume, of the material in the charge. The distillation
was complete in about eight hours, and the residual coke was raked out
of the retorts, these being then recharged. The process was therefore
intermittent, not continuous.

This disadvantage was felt, even in the early days of the industry,
and attempts were made to afford a remedy. Thus, Perutz3 con-
structed a horizontal retort designed for continuous working ; but this
and other horizontal retorts for achieving the same object failed in
practice, because, on the one hand, distillation was incomplete, and on
the other the high specific gravity of the tar lowered the quality.

The first vertical retorts constructed for the production of tar were
of the shaft pattern.4 Owing, however, to the extensive decomposition
obtained, the resulting tar was unsuitable for further treatment.
Unger 5 considerably improved the construction of this retort by pro-
viding it with an external heating apparatus, so that the tar vapours
were no longer brought into contact with the fire gases. His retort
worked continuously, fresh quantities of the charge descending from a
charging hopper at the top in proportion as coke was drawn away from
the bottom. The Perutz 6 retort was allied to this pattern.

The arrangement of these vertical retorts, however, was not adapted
to ensure satisfactory distillation of the charge ; but a thoroughly
suitable pattern, already praised in the first chapter, was constructed
by Eolle in 1858, and, with a few minor alterations, is still exclusively

1 Dingler's " Polyteclm. Journ ," 146, 211.

2 Ibid. 150,130.

3"Die Industrie der Mineralole" ("The Mineral Oil Industry"), p. 12J.

4Oppler, " Handbuch der Fabrikation Mineralischer Oele " ("Handbook of
the Manufacture of Mineral Oils"), pp. 87 et seq. ; Wagemann, " Dingler's Poly-
techn. Jour.," 140, 461.

5 Wagemann, "Dingler's Polytechn. Journ.," 150, 130.

6 " Die Industrie der Mineralole " (" The Mineral Oil Industry ") pp. 144 et seq.

THE PKODUCTION OF DISTILLATION TAB

used in the province of Sa&ony, having displaced the horizontal re-
torts in virtue of its advantages. It works continuously, and is more
easily attended to than the horizontal pattern, less labour being also

FIG. 4. — Rolle retort.

required. The output per unit time is five times as great as that of the
horizontal pattern, and a higher yield of better quality tar is obtained.
At first the (cast-iron) retorts were small, being only 3 ft. in diameter
and 12J ft. high ; but the dimensions were afterwards increased, the
iron cylinder being surrounded by a thin jacket of firebrick, on ac-

SHALE OILS AND TAES

count of the rapid wear and tear. Soon after, Eolle proceeded to
build the whole cylinder of firebrick, and increase the dimensions
all round, and at present the retorts measure 19 to 23 ft. in height
(rarely 26 ft.) and 5 to 6 ft. in diameter. A Eolle retort is illustrated
in Fig. 4. A is the firebrick cylinder, B the flues, also enclosed in a
firebrick casting C. Inside the cylinder D is a series of superimposed
bevelled iron rings, strung at regular intervals on an iron rod a. In
•section these rings resemble louvres.

The cylinder is built of tongued and grooved firebricks, as shown in
Pig. 5, the bricks being 4£ ins. high, 4 ins. thick, and 12 to 16 ins.
long, with a longitudinal tongue 1 by J- in. The
bricks are rubbed together to make them fit
closely in laying, and the small spaces in the
joints are filled \vith a mortar which cements
them firmly together. Various approved
recipes are used for the mortar, consisting of
•clay, finely ground sand, and ground firebrick or pottery clay, the mix-
ture being stirred up with molasses and syrup. As a rule the joints of
the firebrick cylinder run in superimposed horizontal circles ; but Schlie-
pack (Ger. Pat. 35,180), in building the retorts of the Waldau works,
arranged the bricks in such a manner that the joints described a con-
tinuous spiral course from the beginning to the end of the cylinder.

FIG. 5.

Bricks of Rolle
retort.

FIG.

5. — Cast-iron bell rings, Rolle
retort.

FIG. 7. — Cast-iron plain rings, Rolle
retort.

At the base of the cylinder is laid a ring of slightly tapering bricks,
rising gradually to the height of a grooved brick, from which point on-
ward the ordinary bricks are used, the top of the cylinder being com-
pleted by a similar ring of tapering bricks of gradually diminishing size.
This system, which has also been adopted in other places, offers the
advantage of a closer bonding of the bricks than when each ring is
complete in itself, the cylinder forming a complete whole and re-
maining impermeable to the gases for a long time. To increase this
property, which depends largely on the use of good brick material,

THE PKODUCTION OF DISTILLATION TAE

the bricks are glazed on the inside ; but this glaze soon cracks, and
no longer keeps the cylinder gas-tight unless good materials have been
used.

FIG. 8. — Iron cone of Eolle retort.

The cast-iron bell rings filling the interior of the cylinder are in
part provided with cross stays which join the whole at the centre into
a ring traversed by the iron bar. One of these rings is shown in Fig. 6,

FIG. 9. — Cone and bell of Rolle retort.

whilst the plain rings are illustrated in Fig. 7. The whole series
consists of about twenty-eight plain rings and six with stays ; and the
rings themselves are arranged that the upper ones rest on the rims of
those below by means of lugs (k in Figs. 6 and 7). In this way, a small
cylindrical chamber R is formed inside the firebrick cylinder, and com-

26 SHALE OILS AND TABS

municates with the surrounding chamber E by means of the apertures
formed between the rings. This chamber E is the distillation chamber,
which receives the charge of material, and is 3 to 4 in. wide. The fire-
brick cylinder terminates below in an iron cone D, to which is attached
a cylindrical iron box F having a capacity of 3^ to 7 cub. ft. and fitted at
the top with a slide which closes it against the cone, whilst a similar
slide d' at the bottom enables the box to be emptied.

As shown in Figs. 8 and 9, the iron cone rests with its edge a on
the brickwork and is bricked in. In some works the cone is built up
of firebrick, as shown in Fig. 8, and carries an internal firebrick pillar

FIG. 10. — Iron cap for retort rings.

F supported by a cross K. This arrangement reduces the free space
for the spent charge and causes the latter to slide down into the box B
in a more uniform manner than in iron cones.

Inside the cone A (Fig. 9) a bell B is suspended at/, forming a
support for the series of rings and the rod a, and carrying at c the pipe
b which leads to the receiver. The series of rings is covered by an
iron cap (Fig. 10), through which passes the discharge pipe b', joining
the second pipe issuing from the lower portion of the retort b. Below
the mouth of the first pipe, and about one-third down the retort, is a
bell ring covered by an iron plate, which thus divides the series of rings

FIG. 11. — Section of bricked retort.

into two zones. In other plants the first delivery pipe for the distilla-
tion products is also led downward inside the retort itself, as shown in
Fig. 8.

As a rule the lower portion of the firebrick cylinder is surrounded
with a firebrick jacket in order to protect it from the heat, this protec-
tion being especially necessary since the general introduction of gas
firing. For the purpose of forming the flues, the firebrick cylinder is
surrounded, at a distance of about 8 in., with one of similar construc-
tion (rings of firebricks). The intervening space, which narrows by
1-J- to 2| in. towards the top, constitutes the flue for the fire gases, which
are guided by baffles of taper firebrick. At the top of this flue the
gases enter a passage which conducts them to the chimney stack.

Fig. 11 represents a portion of the section of a bricked retort, in

THE PRODUCTION OF DISTILLATION TAR 27

which a indicates the joint feathers, b the bricks of the jacket, c the
flue cover plates, and d the bricks of the outer wall of the retort.
The intermediate space z forms the flue. The retort is enclosed in
an outer shell of baked brick. Heat is generated on the grate r (Fig.
4) with coal, which, however, must only be regarded as an auxiliary
fuel, the principal heat being furnished by the gases produced in the
distillation process, as will be described more fully later.

The firebrick used in building these retorts must satisfy two re-
quirements, namely that it is inert towards the encrusted flue ash from
the lignite fuel, and is able to withstand high temperatures without
fusing.

The flue ash of the non-bituminous lignite fuel l is basic, and the
material for the firebrick must be basic too. If acid material were
used, the basic silicate of the ash would combine with the acid silicate
of the firebrick to form a double silicate, and would become encrusted
on the hot bricks. In cleaning out the flues, this encrustation would
break off, tearing with it a portion of the brickwork and seriously
damaging the retort. The most suitable bricks are those composed of
pure aluminium silicate, these being able to offer the greatest resistance
to heat on account of their high melting-point.

Mention is deserved by F. A. Schulz's patent (Ger. Pat. 6832) for
replacing the iron bell rings by those of clay, viz. two-thirds ground
firebrick and one-third stoneware body. *These were said to be cheaper
and easier to clean, but they did not answer in practice, and therefore
the patent has not found technical application.2

Eotary retorts were formerly tried without success ; and recently,
Grafe 3 described a similar type invented by Gebr. Barnewitz, of Dresden
(Ger. Pat. 156,952), with which he recommends that experiments should
be tried in the lignite tar industry. So far, however, as the author is
aware, this has not yet be done.

The Work of the Retort,

The retort is charged from the top, and when working properly,
the lignite lies in the distillation chamber between the fiiebrick cylinder
and the central rings, a further quantity being piled up to a height of
20 in. above the cover ring, so as to close the top of the retort. The
hot gases from the grate traverse the flues and heat the retort. In the
upper section of the retort the operation is chiefly one of dehydration
of the damp charge, the liberated steam passing into the interior of the
series of rings, and escaping through the delivery pipe, b' (Fig. 4). At
certain intervals the spent charge is drawn off from the cone A (Fig. 9)
into the box F, by opening the slide d\ and in the same proportion
a fresh quantity of charging material descends into the distillation

1 Schliepacke, " Uber die Befeuerung der Schwelzylinder " ("Firing the Ke-
tort"). " Jahresber. des Technil.ervereins," 1890-1.

2W. Scheithauer, " Die Fabrikation der Mineralole'' (" The Manufacture of
Mineral Oils"), pp. 41 et seq.

:{ " Braunkohle," 8, 515.

28 SHALE OILS AND TAES

chamber. The dehydrated charge sinks through progressively hotter
zones in the retort, until it reaches the cone in a spent condition.
Fresh portions of material must be piled on to the cover ring, to keep
the top of the retort always closed.

In the same way as the steam and probably also a portion of the
tar vapours are led away through the upper delivery pipe, the distilla-
tion products liberated in the lower portion of the retort pass off through
the pipe b. These two pipes unite and discharge at G into the receiver,
to which is attached an exhaust fan, or Koerting injector, to force the
vapours on towards the condenser. If necessary, communication be-
tween the retort and the receiver can be cut off by means of a throttle
valve.

The Condensing Plant.

The condensing plant is charged with the task of condensing the
distillation products, so far as the same consist of vapours, and not
permanent gases. In the Saxon industry the condensing plant is
composed of a number of horizontal and vertical wrought-iron tubes of
thin metal, the tubes being riveted, or else welded by the oxyhydrogen
flame. Experience shows that a retort 5 to 6 ft. in diameter requires a
condensing surface of 860 to 1070 sq. ft. The tubular system com-
mences with wide tubes, communicating with narrower ones, these in
turn leading to very narrow tubes. When the large tubes measure 36,
31, and 28 in. in diameter, the intermediate tubes will be 20, 16, and
12 in. and the final tubes only 1 in. in diameter.

The cooling effect is produced solely by the external air ; and it is
important that the vapours should pass through as long a track of
tubing as possible. It has been found that if the vapours are artificially
cooled (with water) in a short condenser to the same temperature as
is attained in the atmospheric condenser, they still contain condensable
constituents, whereas these are almost entirely absent when air is used.
The most important point in the condensing process is the gradual
cooling, which can only be attained with a long condenser, cooled by
air. These conditions were thoroughly investigated at the time the
practice of using the distillation gases for heating purposes was intro-
duced (see Chapter XIV). Recently, Grafe l has again convincingly
demonstrated that air cooling is fully adequate for the condensation
of the vapours, only about 0'7 per cent of condensable hydrocarbons
being left at the conclusion of the process.

It will easily be understood that attempts were made at an early
period in the history of the industry to substitute water cooling for air
cooling, on account of the large space and heavy initial outlay required
for the latter.2 For the reasons given above, these endeavours proved
unfavourable, and the old, proved system was retained. Of late years,
water-cooled condenser plants have again been erected in order— ac-

1 " Braunkohle," 1905, 388.

.? O. Burg, " Polytechn. Centralhalle," 1858, 641 ; B. Hiibner, " Dingler's Poly-
techn. Journ." 146, 215.

THE PRODUCTION OF DISTILLATION TAB 29

cording to Grafe 1 — to save space and capital outlay. The amount of
cooling water required for these plants is at least ten times as great as
that of the products of condensation.

The exhaust devices consist either of fans or Koerting injectors,
the former being preferable owing to the defects of the latter, which
consume far more steam than a fan, whilst the steam they introduce
into the vapours retards condensation, the steam itself having also to
be condensed.

The injector also accelerates the flow of the vapours, with unfavour-
able results, especially in the summer ; and emulsions of tar- and water
vapours, resulting in loss of tar, are formed — all of which drawbacks
are obviated by the use of fans.

The heavy, less volatile vapours, paraffin and heavy hydrocarbons,
are condensed in the first section of the condensing plant, where the
tubes are mostly horizontal, whilst the oily constituents — low in paraffin
— are deposited in the vertical tubes.

Formerly these two condensates — paraffin tar and oil tar — were
occasionally separated, each being worked up by itself. This method,
however, has failed to make any headway, it being far preferable, for
technical reasons, to work up the tars together.

The tar from the condenser collects in a vessel where it is separated
from the accompanying water which is $un off, the tar being transported
to the mineral oil works.

The Dry -distillation Process.

Up to the end of the 'eighties, the retorts were heated exclusively
with mon- bituminous lignite burned on flat grates, as shown in Fig. 4,
in which r is the grate, the ash falling down into H and being dis-
charged therefrom by opening the slide.

Attempts to supersede flat grates by step grates or semi-gas firing,'2
proved unsatisfactory, the principal object, namely a saving of solid fuel,
not being achieved. As far back as the early 'sixties, Eolle began to ex-
periment with the distillation gases for heating the retorts ; but did not
succeed in making this system work reliably on the large scale. He
was unable to obviate the risk of explosion, and moreover obtained a
lower yield of tar than with the older system. Another substantial
hindrance to the success of his experiments was the lack of a fireproof
material (brickwork) for this mode of heating. After firebrick became
available for this purpose, Wernecke took up Eolle's experiments again,
at Gerstewitz in 1887 ; and at the same time Ziegler carried on heating
trials with distillation gases at Nachterstedt. Thanks to Wernecke's
publications on this matter, other works successfully applied gas for
this purpose ; and now the system is in use at practically all the works
in the province of Saxony.

1 Grafe, " Die Braunkohlenteer-Industrie " (" Lignite Tar Industry "), p. 27.

2 Schliephacke. " fiber die Befeuetung der Schwelzylinder " ("Firing the
Retort" ), " Jahresber. desTechniker-Vereinsdersachs.-thiir. Mineralolindustrie,"
1890-1.

30 SHALE OILS AND TAES

In general, the arrangements are such that the gas is drawn from
the end tubes of the condenser by means of a Koerting injector and
delivered to a cooler, where any tar vapours still retained are deposited.
As already explained, when the condensing surface is sufficiently large,
the gas contains only very small quantities of condensable matters,
and on this account the gas cooler is omitted in some works. As
shown in Fig. • 4, the gas is then conducted through the pipe e to the
retort, and is fed to the grate r through lateral chambers s provided
with slits. In some works the gas is admitted to the second or third
flue as well.

To counteract any explosions that may occur, and to prevent them
from extending back to the condenser plant, an automatic closing de-
vice is provided in some works between the fire and the condensing
plant. For this purpose Grafe l recommends a sufficiently weighted
explosion valve, as shown in Fig. 12. The valve B pivots at a, and is

forced upward by the explosion, so as
to allow the pressure to escape into
the outer air. Experience proves,
however, that a device of this kind is
unnecessary, the Koerting injector
which delivers the gases to the fire

constituting a reliable stop and pre-

£_ £ \ venting an explosion from striking

FIG. l2.-Explosion valve. bfk to *he condenser. Care must

(i = Gas main ) ° course be taken to keep the injector

always in good working order.

In general, the method of heating is not exclusively by gas, lignite
being burned on a flat grate ; and it is only in a few cases that gas fir-
ing is used by itself. As already mentioned, the firebrick now avail-
able is capable of withstanding the effects of gas firing for a considerable
time.

The introduction of gas firing has brought great benefits to the in-
dustry in comparison with the old, flat-grate system. In the first
place there is a very considerable saving in solid fuel, only 15 to 10 per
cent (or even less) — referred to the volume of the charge — being now
required against 35 to 40 per cent formerly. The cost of labour (stoking)
has been reduced to about one-half, one man being able to look after
20 to 24 retorts. Most important of all, the output of the retorts has
been increased by 20 to 30 per cent.

No hard and fast rules can be laid down with regard to the manner
of heating the retorts. The temperature in the flues, from above
downward, has been determined as 400 to 600° C. ; and, when the re-
torts are working properly, the distilled vapours should have a tem-
perature of 120 to 150° C. on issuing from the retort. The way in which
the heating is conducted is mostly a question of experience, and depends
on- the character of the raw material, the underlying principle being to

1 " Die Braunkohlenteerindustrie" (" Lignite Tar Industry"), p. 22.

THE PRODUCTION OF DISTILLATION TAB 31

obtain a favourable yield of tar and a usable coke that will find a
ready sale.

The retorts are charged with the bituminous lignite as it comes
from the mine. If the same be too large, it must be crushed, or large
individual lumps must be broken by hand. Occasionally, small iron
rollers are used for crushing. It is not advisable for the lumps to be
larger than 1-J to 2£ in. in diameter.

If the material be too damp, it must be dried, which is effected on
the charging platform of the retort house. The moisture content
should not be less than 30 per cent or more than 60 per cent, since
beyond these limits the material is difficult to work in the retorts — in
the former event the bitumen is over-decomposed, being no longer
protected by the liberated water vapour, whilst in the other case the
charge bakes in the retort and will not descend freely. About 150 to
75 bus. of average material can be distilled in a retort of ordinary size
in twenty-four hours, though sometimes the quantity is larger. With
very high retorts and inferior material, up to 280 bus. can be dis-
tilled in a day. As a general rule, the better qualities of material

a
FIG. 13. — Coke box. FIG. 14. — Coke box.

must be distilled more slowly than the inferior kinds, and therefore
the quantity treated in unit time is smaller.

Before gas heating was introduced, the coke was drawn from the
cone into the iron box about eighteen to twenty-four times in the twenty-
four hours ; but now this can be done thirty to forty times and even more,
much depending, of course, on the adaptability of the material for dis-
tillation. In Figs. 13 and 14, A represents the cone and B the iron box.
When the upper slide C is drawn, the coke slides down to B, where
it is left to cool until the next "draw," whereupon it falls — on the
lower slide D being opened — from B into the receptacle. In the early
days of the* industry numerous accidents were caused by opening the
two slides at once, a large quantity of glowing coke falling out of the
retort before one of the slides could be pushed in again, so that out-
breaks of fire occurred and human life was endangered. To make the
working of the slides independent of the operator, automatic slides
have been constructed, e.g. by Grotowsky and Vogt ; and the use of
such slides has been prescribed by the trade guilds for some years
past. The arrangement of the Vogt slide is shown in Figs. 13 and 14.
The guides for the two slides, C and D, are provided with openings a,
in which works an iron bar B fitted with a handle b. Similar- open-
ings are provided in the draw-bars operating the slides. The rod E is
provided with strengthening rings c near the two ends, and is of such

32 SHALE OILS AND TABS

a length that it fills the one opening a completely, but only extends
as far as the slide in the other opening. The handle b can be turned
so as to rest on the support d provided on B, this being the case
when both slides are closed and only the lower one can be opened (as
shown in Fig. 14). In this position the upper slide cannot be opened,
being prevented by E in a. If now the lower slide D be closed, the
handle lifted away from d, and E be allowed to descend, then E locks
the lower slide, and only the upper one can be opened. This position
is shown in Fig. 13.

The coke falls from B either into trucks or pit tubs, and is still at
a temperature of 360 to 400° C. Complete cooling, "quenching," is
effected with water, for which operation various devices are used.
Formerly the coke was quenched by simply dropping it into a brick
tank filled with water. As flames are given off during this operation,
the coke quencher must be placed at some distance from the distilling
plant, and means must be provided to prevent the men from falling
into the tank when the latter is full of hot coke, accidents having
occurred from that cause, so that the quenching tank must be sur-
rounded by railings or covered over with netting.

These drawbacks, together with the by no means inappreciable loss
of coke, in the form of dust, are obviated by the newer quenching de-
vices. The regulations issued by the Mining Police on 12 October,
1904, prescribe the adoption of measures to prevent outbursts of flame
in coke quenching, and the scattering of glowing coke. The usual
method at present is to quench the coke in the trucks or pit tubs into
which it falls from the retorts — either by sluicing them with water, or
immersing them or drawing them through tanks filled.with that liquid.1

In some works the coke quenching devices are suitably combined
with those for loading the coke into railway trucks.

Attempts 2 made to cool the coke out of contact with air and with-
out water, have proved unsuccessful. On the one hand the coke takes
a long time to cool down, and on the other — a very important con-
sideration— the resulting coke makes very inferior fuel.

The distillation process is continuous, work being carried on both
Sundays and weekdays ; and the only time the retorts are stopped is
when they need repair. The retorts are cleaned out at regular inter-
vals, which vary in different works, according to the material treated
and the method of working — 5, 9, or 12 months. Cleaning must be
done whenever the retorts show signs of not working properly. »

The bell rings and walls of the retort and cone get encrusted with
half-burnt lignite, resinified tar, and impurities, such as sand or clay, in
the charge ; and the resulting irregularities of the surface prevent the
charge from descending uniformly when the coke is drawn, leaving it

1 According to Ger. Pat. 27,723 (A. Mann, Nuremberg) the coke is placed
in perforated receptacles, which are then submerged in water. At the Dieskau
works, water is passed through a perforated pipe traversing the coke truck.
" Braunkohle," 2, 393.

2 " Braunkohle," 4, 600.

THE PRODUCTION OF DISTILLATION TAB 33

jammed at the rough places. Cavities form in the charge and be-
come filled with vapours, which may give rise to an explosion and
interrupt the working of the retort.

The retorts are either cleaned out singly, or else several are stopped
at the same time for this purpose. The retorts stopped for cleaning
must be disconnected from the common receiver by tightly closing the
throttle valve.

To cool down a retort the fire is drawn and the suction fan kept
running, the coke being drawn and further quantities of charge added
until the retort is cool. At this stage the bell rings are lifted out of
the retort by means of lifting tackle, and thoroughly cleaned. The
retort is also cleaned out ; and when a whole group of retorts is
stopped for cleaning, the delivery pipes and receivers, condensing plant
and gas main are all thoroughly examined and cleaned. Any necessary
repairs to the brickwork are also effected, and the grates are put in
order. If the retorts are cleaned singly, they will be ready for work
again in five to eight days ; but in the case of a battery the stoppage
lasts for three weeks.

No difficulty is encountered in replacing the rings and heating up
the retort again. As a rule the half -spent charge, which was drawn
on cooling down the retort, is fed in for the first charge on restarting.
The distillation gas is led into the firebox as soon as it is sufficiently
free from admixed air to burn at all. Tfte coke cannot be regarded as
marketable until the work has resumed its normal course.

The only important difficulties in working the retorts arise when
the charge sticks and will not descend uniformly. One instance of
this kind has just been discussed ; and another may occur when the
charge is too damp, the material then baking together and leaving
cavities for the accumulation of vapour. The occurrence of such ir-
regularities can be detected by watching the descent of the heaped
charge at the top when the coke is drawn. It should slip down uni-
formly all round the distillation chamber, and if it does not, it must be
assisted by means of long or short irons pushed down into the chamber
.to remove the obstruction. Care should be taken to see that the
•charge sinks down evenly all round, each time coke is drawn.

The yield of tar from the charge varies according to the percentage
of bitumen in the latter. At the present time the average is about
2-J to 5 Ib. per bus. (50 to 60 Ib.) of charge ; but in former years, when
there was an abundance of richer material available, it was consider-
ably higher.

The Distillation Plant.

As a rule the retorts are grouped in batteries of ten to twelve, each
battery having a common condensing plant and an exhaust apparatus.
The retorts in a battery are arranged in a row and are lagged with a
mixture of clay and molasses to prevent loss of heat by radiation.

Either one or two batteries are set up in line, with a safety wall

SHALE OILS AND TABS

THE 'PRODUCTION OF DISTILLATION TAB

dividing them, or else in two parallel rows — in both cases under
cover. The two-row system was first introduced by Rolle, and sub-
sequently adopted by Riebeck. The building is of strong construction
and roofed with mill-board, though some retort houses are provided
with corrugated iron roofs. The interior must be thoroughly well
ventilated.

Fig. 15 gives a plan and horizontal section of a distillation plant
with the retort batteries arranged in line ; whilst \Fig. 16 is a vertical
section of the same plant. Here, a represents the retorts, b the fires,

FIG. 16. — Dry-distillation plant. Vertical section.

c the stoker's platform (7 to 10 ft. wide), and t the chimney stack. The
retort vapours draw off through the exhaust pipe d to the receiver
e (which is common to each set of four retorts), and thence through
/ to the collector g. From this point they are delivered by the ex-
haust fan h to the horizontal condenser plant i, i, and then to the
vertical condensers m, m. x is the steam engine driving the fan ;
but is now replaced in some works by an electromotor. The tar con-
densed in the horizontal tubes flows into the collector &, and thence
to the tank n where the tar from the vertical condensers collects.

3,6 SHALE OILS AND TABS

The gas escaping from the end tubes of this condenser is forced by
means of a Koerting injector to the fire, or else is utilized as power
gas.

B (Fig. 16) is the charging platform, to which the lignite is de-
livered by an aerial ropeway or, in this instance, in pit tubs. The
fuel for the grates is sent down to the stoker's platform through the
hopper S.

The plant, buildings, and fireproofing arrangements must be carried
out in accordance with regulations issued by the Mining Police for the
Halle district (1 April, 1906), the prescriptions of which are fully satis-
fied by the newer plants.

The capital expenditure on a retort and the corresponding condens-
ing plant amounts to £500 to £600.

No definite particulars can be given as to the working life of the
retorts. It is important that the best materials should be used in their
construction, and that necessary current repairs should be effected.
The retorts may last twelve to fifteen years or longer.

C. THE MESSEL TAR INDUSTRY.
The Retorts.

As already mentioned, MesseL coal is high in both ash and
moisture, and also differs from the lignite distilled in the Saxon-Thur-
ingian industry by its lumpy character and lack of extractable bitumen.
Hence, unlike Thuringian lignite, the decomposition of the bitumen
has not to be attempted in working up this material. Dry distillation
destroys the combination of the organic substances with the mineral
matters, gaseous, aqueous, and easily refined oily distillation products
being formed.

The utilization of Messel coal is carried on by the Gewerkschaft
Messel at the Messel mine near Darmstadt, in extensive works which
are without parallel, so far as the distillation plant is concerned, this
being adapted to suit the peculiarities of the raw material.

The retorts used in Saxony will not work satisfactorily with open
tops unless the charge contains enough pulverulent material to pre-
vent the access of air from outside. One of these retorts was tried at
Messel, but did not work unless the coal was finely crushed; the
cost of this operation having therefore to be taken into consideration.
Moreover, since the lumpy character of the coal enables dry distillation
to be carried on in a current of steam, which, as is known, prevents
decomposition .from being pushed too far, the system of working was
arranged on these lines from the outset. At one time the material
was dried in a special stove (Ger. Pat. 48,413) in which the moisture
content was reduced from 44 per cent to about 6 per cent, the dried
material being then distilled in a current of steam in vertical retorts,
which, by means of an easily operated Morton valve, could be emptied

THE PRODUCTION OF DISTILLATION TAR 37

into generators underneath, where the still lumpy residue (coke) was
gasified, the resulting gas serving to heat the retorts. Hence there
was no marketable coke as in the Saxon-Thuringian industry, all that
remained being ash. To carry out this older process, a portion of the
coal had to be burned, in order to dry that for the charge ; whilst a
further portion was consumed in raising large quantities of steam for
the distillation process. The moisture in the coal was dissipated from
the drying stoves into the air, whilst steam was being generated in the
adjoining boilers. Even at an early date it seemed advisable to try
and balance these opposing factors and to replace the boiler steam by
the moisture from the stoves, for the distillation process. Moreover,
the nitrogen content in the residual coke afforded the possibility of re-
covering ammonia therefrom by the Hubert Grouven process (Ger.
Pats. 2709 (1878); 13,718 (1880); 17,002 (1880); 18,051 (1881)).
Though this process had not proved successful in the peat industry
with which its inventor was connected, it became the foundation of the
Mond-gas process l and also the saviour of the Scottish shale oil in-
dustry. Unhappily, too little recognition has hitherto been accorded
to Grouven's priority in this connexion, and his premature death pre-
vented him from asserting his claims in person.

The Grouven process is based on the fact that by gasifying nitro-
genous coke in presence of a large excess of steam, water gas is formed,
and the nitrogen appears among the products of gasification as am-
monia which is recoverable in the form of ammonia salts. However,
since Messel coal must in any case be freed from a large quantity of
moisture before it could be subjected to dry distillation, it furnished a
large supply of steam without expense, provided this steam could be
generated from the coal in the <-losed chamber required for the dis-
tillation process, and be afterwards utilized for the production of water
gas. Furthermore, since the waste heat from the retorts is sufficient
to convert large quantities of water into steam, it seemed feasible to
generate the necessary steam from the damp coal by means of that
heat. The water-gas process in turn furnishes enough waste heat for
the dry-distillation process. The problem of combining these pur-
poses was tackled by the Gewerkschaft Messel in many costly experi-
ments, extending over a number of years and finally resulting in the
elaboration of a new process which has now superseded the older one
at the Messel works.

The process forms the subject of German Patent 200,602, of 23
May, 1906. The principle employed is illustrated by Figs. 17 and
18 (the latter showing the lateral elevation of the blower G, G),
which are taken from the Patent Specification. E represents the
retorts, the lower portion of which is made of firebrick; and, a, 6,
c, show the three stages of charging, whilst d is the common out-
let for the water gas and the distillation vapours. F and G serve to
maintain the circulation of steam through the stage c of charging

1 See Fischer, "Kraftgas" (" Power Gas "), p. 142.

38 SHALE OILS AND TABS

(Fig. 18). A, B, and C are the heating chambers, connected together

FIG. 18. — Blower.

FIG. 17. — Messel retort.

by o, o, o, and each corresponding to one stage ; whilst s represents
the supply pipes for the heating gas.

THE PRODUCTION OF DISTILLATION TAR 39

The Work of the Retort.

The working process is divided into three stages, namely, the drying
of the coal, in connection with the generation of steam ; the distillation
of the dried material ; and the gasification of the residual coke with
the steam generated in the first stage. The three stages are effected
in the same retort, and in succession from above downward. The
charging and discharging proceed continuously. No special mechanical
devices are used to separate the various stages, this being satisfactorily
accomplished by the manner in which the steam circulation is main-
tained. In correspondence with the three stages inside the retort, the
external heating of same is effected in three zones, namely a zone
of maximum temperature for the production of water gas, in the
lowermost portion of the retort, a, a ; a middle zone, b, b, in which
the distillation temperature prevails ; and the upper zone, c, c, which
is devoted to the generation of steam, i.e. the drying of the charge.
The heating chambers A, B, and C, are comparatively spacious ; but,
nevertheless, the only communication between them is by means of
openings, o, o, of such small diameter as to preclude any convection of
the heating gases from one chamber, or zone, to another ; whi'st only
so much ascends from one space to another as is requisite for the
amount of fumes generated at the aqrtual draught. Owing to the
roominess of the chambers, the convection therein is ample, and in
each zone there is attained a uniform temperature which differs con-
siderably from that of the preceding zone. Large quantities of heat
are naturally required to expel the high percentage of moisture in the
coal, and consequently the fumes must enter the steam-generating
chamber at a very intense heat. As a matter of fact the temperature
is so high that the operation would not stop at the expulsion of
moisture, but would also affect the distillation of the dried material,
were it not that care is taken to keep the temperature down to below
that required for distillation, in the upper charging stage, by maintain-
ing a very brisk circulation of steam in this stage. This steam, at a
temperature of slightly above 100° C., enters at the hottest part and,
itself becoming superheated, carries the excess of heat away to the
place where the newly introduced coal, with all its original percentage
of moisture, is situated. The circulation is produced by means of a
powerful fan mounted on the retort, and is so efficacious that the
steam remains free from any dry-distillation products and can be led
away for the production of water gas without causing any decomposi-
tion of valuable constituents. On the 'other hand the utilization of
the heat is so complete that the fumes escape into the chimney at a
temperature of only 200° C.

The steam, which has greatly increased in quantity through the
moisture absorbed during the circulation, is forced by a small blower
into the bottom end of the retorts and ascends therein, forming water
gas as it rises. The retorts are heated by the very large quantity of
mixed water gas and distillation gas formed, amounting to over 500

40 SHALE OILS AND TABS

cub. ft. per cwt. of coal in the charge, after all the condensable and
extractable constituents in the gas have been removed. Even after
the requirements of the retorts have been satisfied, there remains a
considerable excess of gas, which is led away to the power station and
utilized for steam raising there. The calorific value of the gas is very
high, and, after elimination of the circa 20 per cent of carbon dioxide
present, it is admirably adapted for incandescent lighting. The distil-
lation vapours and water gas are drawn off through a common exhaust
pipe about one-third of the way up the retort. The mixture is first
freed from particles of water vapour, and then passed in succession
through the ammonia-recovery plant, the condenser plant and oil
washery, to a gasholder, for delivery to the several centres of con-
sumption. The portion destined for the gas engines is passed through
purifiers charged with the usual ferric-hydroxide purifying mass, for
the purpose of eliminating the contained sulphuretted hydrogen.

The plant for treating the vapours before they reach the gasholder
will be more fully described later. The following points in connection
with the raw material may be mentioned here : the coal coming from
the pit is crushed in a breaker and separated from dust and slack on
special screens, since these finer portions would present an excessive
resistance to the passage of steam in the retorts. The dust and slack
are utilized in other ways by the aid of special appliances. Screens of
perforated sheet iron were formerly used, but were afterwards dis-
carded because they are liable to become obstructed in consequence
of the clayey nature of the material, especially in wet weather. At
present all the screens used are provided with rotary knives projecting
through the slits and keeping the latter clear of obstructions. The
coal, reduced to lumps between a hen's egg and a goose egg in size,
and classified, is transported by means of ordinary conveyors to the
charging hopper of each retort. The retorts are emptied by means of
a suitable discharging device which is set in operation for a short time
every half hour. The discharged residue can be a perfectly pure ash,
which is grey in colour — in contrast with the red ash furnished when
the coal is burned in a grate — but turns red on calcination. In prac-
tice, however, this complete incineration is unnecessary, more gas
being already produced than is required ; and therefore, in the absence
of any means of utilizing the surplus gas for the present, the residue
is withdrawn with a carbon content of about 8 per cent and removed
to the spoil heap.

Twenty-four retorts of small sectional dimensions constitute a bat-
tery, capable of treating 26 tons in twenty-four hours. Charging and
discharging proceed continuously.

The Treatment of the Distillation Vapours.

(a) Recovery of Ammonia. — The gaseous mixture from the retort,
after being freed from water vapour, is scrubbed with dilute sulphuric
acid in towers of the Glover type, to remove the ammonia from the

THE PRODUCTION OF DISTILLATION TAB 41

still hot gases.. The resulting ammoniacal solution is evaporated by
the heat contained in the vapours, i.e. the liquid is used to cool down
the hot gases. The sulphate of ammonia obtained on evaporating the
solution is centrifugalized, dried, and sold.

(b) Condensation. — The partially cooled mixture of gas and vapour
is further subjected to the cooling action of water, the latter being
evaporated in the process. This water is the water of condensation,
which was previously cooled in cooling towers and is cooled again
after being rewarmed. The resulting water of condensation serves as
cooling water and is maintained in circulation through the tubular
condensers and the cooling towers, which are of similar construction
to the recooling plants of condensing engines. In this way the effluent
water is reduced to a minimum, and the surplus is got rid of by using
it to quench the hot residues on the spoil heap. Finally, the vapours
are cooled with water from the pit mains, and are passed onward to the

(c) Oil Washer y. — This is similar to the corresponding apparatus
for the recovery of benzol in coking plants, and therefore needs no
further description here. The highly volatile oil ('•' naphtha " or
" photogen ") thus recovered is pale in colour and forms about 8 per
cent of the total crude oil produced. If it be left in the gas it increases
the heating value of the latter ; but since the gas has no marketable
value and is already present in excels, considerable importance is
attached to the oil washery.

(d) The Exhaust Fans. — These are of the high-pressure type and
are coupled direct to electromotors. Particular importance is attached
throughout the whole plant to minimizing the resistance offered to the
passage of the mixture of gas and vapour, since power is thus saved and
the use of expensive valveless gas pumps can be dispensed with.

D. THE EECOVERY OP SHALE TAR IN SCOTLAND.

The Retorts.

Horizontal retorts were originally used in the Scottish industry
also, until eventually, as in the Saxon -Thuringian industry, the vertical
pattern came into general favour.1

These horizontal retorts were of oval, rectangular, or ^ > section,
made of cast iron, and closed at one end by an iron door, whilst the
other end was provided with a delivery pipe for conveying the liberated
vapours to the condenser plant. As the retorts were charged and
emptied through the door, the operation was, naturally, intermittent.

In order to remedy this drawback, the vertical retort was soon
adopted, a number of which were already in use at the end of the
'sixties. The older retorts of this type were narrow, oval, or circular
cast-iron pipes, surrounded with brickwork. Charging was effected
through a hopper at the top, whilst the spent shale was let out at the
bottom and fell into a trough filled with water which, at the same time,

1 " Journ. Soc. Chem. Ind.," 1897, pp. 876 et seq.

SHALE OILS AND TABS

acted as a seal. One of these retorts is shown in Fig. 19, a being the
iron pipe forming the distillation chamber, b the charging hopper, and
c the outlet into the water trough. The distillation vapours escaped
through e to the condenser.

In addition to the advantage of continuous working, the vertical
retorts gave a yield of tar 25 to 30 per cent higher than the horizontal
pattern. Coal fires were used for heating the retorts, but the grates
were so large that the iron suffered extensive corrosion and the retorts
became useless in six to nine months.

Young conducted exhaustive experiments with a view to modifying
the distillation process and to obtain a tar richer in paraffin, the far-
reaching decomposition in the old process being effected at the expense
of the paraffin content. At the end of the 'sixties he built retorts of in-

FIG. 19. — Old Scottish retort.

FIG. 20.— Young's first retort.

creased diameter and lowered the distillation temperature to low red
heat. This type of retort is illustrated in Fig. 20. In contrast to the
old retorts, the vapours are led off, not at the top, but underneath at e,
and the retort (a] is jacketed. Early in the next decade Young began
to use the spent shale, instead of coal, for heating, this material con-
taining sufficient carbon to furnish the requisite amount of heat.
Another type of retort constructed by him was distinguished by the
ingenious device through which the spent shale fell into the grate. The
device, however, was too delicate to be suitable for being operated by
workmen with hundreds of retorts to look after. By means of this
device, however, Young was able to prove that the necessary distilla-
tion temperature could be attained from spent shale.

A retort which worked better in practice was that constructed in
1873 by N. M. Henderson and shown in Fig. 21. The retorts A, A are
charged from the truck C, and the spent shale falls down through the

THE PEODUCTION OF DISTILLATION TAR

rotary closing device a to the fire-box B, which is closed by b when
the retort is in work. The vapours escape through the pipes /, / (which
can be shut off from the retorts by g) to the condensing plant, whence
the permanent gases are led through c into the fire. The ashes fall
through d into D, and the fire gases pass away through e, e.

The first set of these retorts was installed at the Oakbank Works
in 1874, and remained in use until 1886, when the retorts were re-
placed by an improved pattern after working well for twelve years.
Plant containing Henderson's retorts was also set up at Broxburn in

FIG. 21. — Henderson retort (1873).

1878, and proved so successful in dealing with the shale there as to
contribute largely to the prosperity of the Broxburn Oil Co. at that
period.

Utilizing the success of Young and Henderson, the shale distillers
who were still using the old vertical retorts reconstructed the heating
arrangements in order to burn the spent shale, thus reducing the dis-
tillation temperature considerably. The tar obtained was of far better
quality and richer in paraffin than hitherto, whilst at the same time the
working costs were reduced.

No success attended the attempts made at Oakbank to increase the

SHALE OILS AND TABS

sectional dimensions of the retorts and heat a number from a common
furnace ; and the Henderson pattern remained the best until 1881. It
was exclusively used at Broxburn, Burntisland, and Linlithgow, where-
as at Addiewell, Uphall, Dalmeny, and Oakbank the old and recon-
structed retorts continued to be employed.

Up till that time the yield of tar was regarded as the most important
feature of the distillation process, ammonia recovery being merely a
side issue ; but 'Beilby and Young began to investigate the possibility
of increasing the output of ammonia from the shale. With this object
they elaborated a new process and constructed suitable retorts for
carrying it out, the idea being to subject the shale to an increased
temperature in the retort itself, after the bulk of the bitumen had been
removed, and thus recover the ammonia. The chief objection to this new

FIG. 22. — Pentland retort.

process was the possibility of an adverse influence on the quality of
the tar, the decomposing effect of high temperatures on that important
product being already known. This anxiety, however, proved un-
founded, an excellent tar being obtained. The new retorts consisted
of an upper portion of cast iron, where the shale was distilled at a low
temperature, and from whence it then descended into the lower fire-
brick portion of the retort. Here the temperature was far higher than
in the upper portion, and steam was admitted, a high yield of ammonia
being obtained (by the process already sketched on p. 21), together
with a larger amount of gas.

The distilling process was more dim cult to supervise with this type
of retort, there being two different temperatures to watch and regulate.
The first retorts were set up at Oakbank in 1881 and worked well, the
output of ammonia being doubled and the tar containing more paraffin
than that from other retorts. The only drawback was the close super-

THE PRODUCTION OF DISTILLATION TAR

vision required, and the grave results that followed any negligence in
this respect. For example, if the lower portion of the retorts grew so
hot as to fuse the shale, they got choked up. These drawbacks in-
duced Young to make remedial alterations and he constructed retorts
of the type illustrated in Fig. 22, and known as the Pentland or Young
and Beilby retort, of considerably larger dimensions and with a bent
pipe c for discharging the spent shale, this form giving increased ac-
cessibility. To facilitate supervision, the fire grate was replaced by a
gas producer. Like the earlier Beilby pattern, the upper portion a of
the new retort was of cast iron, the lower b being of firebrick. The
yield of tar and ammonia was thoroughly satisfactory. Attempts were

FIG. 23. — Firebrick Pentland retort.

next made to improve this type of retort still further, both in point of
arrangement and working, the cast iron in the upper part being super-
seded by firebrick on account of the difficulty experienced in getting a
proper gas-tight joint between the two materials. These wholly fire-
brick retorts, however, only worked for a short time, since, in the words
of Beilby : " the joints between the bricks began to leak and the walls
of the retorts cracked ". It thus appears that a construction which
was found to answer well in Saxon Thuringia was unsatisfactory in
Scotland, owing to the nature of the raw material and above all to the
essentially modified distillation process. In 1885 the Hermand Oil Co.
set up distilling plant containing Pentland retorts of increased height,
each retort being provided with a separate charging hopper instead of
being charged in pairs. The extra height of the retorts proved bene-

SHALE OILS AND TARS

ficial ; but the renewed attempt to construct the retorts solely of fire-
brick (Fig. 23) failed once more, and the idea of modifying the well-tried
system already in use was abandoned. The interruption experienced
in the old Pentland retorts through the discharge passage becoming
blocked with fused shale, was occasionally encountered in this case
too ; but, owing to the improvements made in this direction in the
newer systems of retort, it has now disappeared.

One of these patterns was designed by Henderson, and is illustrated

FIG. 24. — Henderson (improved Pentland) retort.

in Fig. 24. l The shape is copied from the Pentland retort, the diameter
being elongated, the upper portion a constructed of iron, and the
lower b of firebrick. The joint between the two is very carefully
made, so that any leakage there seems impossible. The retort is 27-^-
ft. high, and the temperature in the upper zone is maintained at 400°
C.," whilst that in the lower zone is 700° C. To prevent the shale from
caking together and obstructing the retort, the shale itself is kept in
continuous motion by a toothed roller i at the bottom of the retort which
is made to revolve slowly. By this means the spent shale is discharged

1 " Journ. Soc. Chem. Ind.," 1897, 983.

THE PEODUCTION OF DISTILLATION TAE

from the retort and falls down into the iron box d, whence it is run
down into trucks. The distillation vapours escape through the ex-
haust e to the receiver /. This system presents important advantages.
Since the spent shale is discharged continuously, instead of inter-
mittently, the retorts are easy to work and require little attention.
From the charging hopper, which holds enough shale for eighteen hours'
working, fresh quantities of charge slip down into the retort in propor-
tion as spent shale is discharged below. As the author has himself
seen, this pattern of furnace is the only one used at Broxburn. There
a battery of eighty-eight retorts distils 160 tons of shale in the twenty-

FIG. 25. — Device for discharging spent shale.

four hours ; and only four men are required to look after the whole
during the day shift, whilst two are sufficient in the night shift,
the retorts being then charged from the hoppers exclusively. The
yield of ammonia is still better than that from the other retorts, and
the recovered tar is of good quality.

Another type of retort, built for and achieving the same purpose, is
that of Crichton of Philipstown. In general it is similar to the Brox-
burn retorts, except for slight modifications in detail and firing. To
discharge the spent shale by mechanical means, a device, illustrated
in Figs. 25 and 26, is provided at the bottom of the retort, consisting
of two shafts, a and 6, and a set of arms, c, c, to each. These arms

SHALE OILS AND TARS

slope downward (Fig. 25) at a relative angle of 45°, fitting closely
together and thus closing the bottom of the retort. The spent shale
is not discharged continuously, but intermittently by imparting a rotary
motion to the shafts, thus causing the arms to open and allowing the
shale to fall into the underlying iron box K. This is done every six
hours. As with the Broxburn retorts, the heating is effected by
the distillation gas assisted, in case of need, by gas from a separate
producer.

The retorts constructed by Bryson and set up at the Pumpherston
works are very closely allied to the two just mentioned (see Fig. 27).
The retort is of circular cross section, and is of larger dimensions than
any other in the Scottish industry, being 26| ft. high and 3 ft. in dia-
meter. The distillation chamber will hold 160 cub. ft. of shale, in
comparison with 106 cub. ft. in the Broxburn retorts, and 25 cub. ft. in
the old vertical retorts.

FIG. 26. — Device for discharging spent shale (plan).

The upper portion a is of cast iron, and the lower b of firebrick.
The charging hopper will hold enough shale to last for twenty-four
hours. The spent shale falls down into an iron box d which sur-
rounds both retorts. As shown in Fig. 28, which is a section through
the two retorts along the line A to B, the spent shale is discharged
mechanically. At the bottom of each retort is an iron table t, the
plate e of which closes the retort and supports the spent shale.
'Through the middle of the table passes a steel shaft to which is secured
an upwardly bent arm i corresponding to the circumference of the
plate. On the shaft being rotated, this arm sweeps the plate and
ejects the spent shale thereon into the box d whence it is removed
from time to time. During the distillation process the shaft rotates
slowly, and the iron arm discharges the shale continuously, whilst
fresh material falls down out of the charging hopper. Five tons of
shale are treated per diem. The Pumpherston retorts are heated with

THE PRODUCTION OF DISTILLATION TAK

FIG. 28. — Bryson retort.
(Section A-B.)

FIG. 27.— Bryson retort. Elevation.

50 SHALE OILS AND TAES

distillation gas exclusively, as at Broxburn. The number of retorts at
work is 208 and satisfactory results are obtained.

This type of retort is perhaps the most perfect that has been used
in the Scottish industry, having the highest capacity and smallest
working costs.

In concluding this section it is desirable to compare the develop-
ment of the retorts in the two large distillation-tar industries. Whereas
in the German industry, apart from the utilization of the gases, there
has been no appreciable alteration in the arrangement of the retorts
since the days of Eolle, it is only about fifteen years ago that the
Scottish industry improved its retorts to their present state of perfec-
tion. The reason for this was in the difficult nature of the Scottish
raw material and the different method of carrying out the distillation
process.

The Work of the Retort.

The method of working the retorts has been described in treat-
ing of the various patterns. Common to all is the method of charging
through a hopper at the top, and discharging at the bottom, this latter
operation being — as already described — performed intermittently, by
mechanical devices, in the newer types.

The distillation vapours are now generally led away at the head of
the retort instead of at the bottom as in the old Henderson pattern.

The Condensing Plant.

The vapours are drawn out of the retorts and into the condensing
plant by exhaust fans. The condenser consists of a system of cast-iron
tubes the diameter of which, in large plants, commences with 2 ft. and
decreases to 18 in. In other works, smaller diameters (about 4 in.) are
used, according to the number of retorts employed.

Air is used as the cooling medium. The last constituent to be
condensed, the benzol, is separated beforehand from the tar proper
in another apparatus. The condensation products are collected in
tanks, where the tar separates from the water.

The Distillation Process.

Before the shale coming from the mine is distilled it is put through
a breaker and reduced to lumps about -J to f in. in diameter. Formerly
this was done by hand, with long-handled hammers. The broken
shale drops from the breaker into small trucks in which it is hauled
along an inclined plane, by means of a wire rope or a chain, to the
retorts.

The method of charging and emptying the retorts has already been
described in dealing with the various types, being intimately connected
with their structural arrangement.

At present the retorts are heated by the distillation gases, with
producer gas as an auxiliary fuel, whilst in the older retorts the spent
shale is still utilized for this purpose.

THE PEODUCTION OF DISTILLATION TAR 51

In the course of years the cost of the distillation process has been
considerably reduced. At the present time the quantity of material
treated in unit time is larger, and a higher yield of tar and ammonia
is obtained. The estimate of the Broxburn Oil Co. for the cost of dis-
tillation, including the raw material, per 22 gal. of tar produced at
different periods, is as follows : —

In 1897 : 3s. 6d. (new type of retort).

„ 1879: 4s. 6d. (Henderson retort).

„ 1877 : 6s. 3d. (vertical retort).

„ 1876 : 8s. Od. (horizontal retort).

With the newest retorts of the Pumpherston Co., 5 tons of shale
are distilled in twenty-four hours, whilst 4^- tons are treated at Brox-
burn, in each retort. The yield of tar varies with the raw material
and the type of retort, 1 cwt. of shale furnishing about 8 to 10 Ib. of tar.

In contrast to the Saxon-Thuringian industry, the distillation resi-
due is worthless, and is tipped on to spoil heaps, which have attained'
to the dimensions of respectable hills in the vicinity of the larger
works. Since the shale is still very hot when tipped, these heaps
smoke and disengage malodorous gases.

The Distillation Plant.

In the Scottish industry the distillation plants are generally much
more extensive than in Saxon Thuringia, and heavy capital expenditure
has been incurred. The plants are mostly in the centre of the shale
area and in the vicinity of the mines.

To round off the subject, a brief account may be given of the retorts
used in other shale industries.

In the south of France, retorts similar to shaft furnaces (such as
those formerly used at Keutlingen, Wurttemberg, for distilling the
local Lias shale) were employed at first, being afterwards replaced by
vertical retorts, constructed and equipped like stills. With this type
of plant, however, it was found impossible to distil the shale at a
profit.

After exhaustive investigations and reports, attempts are now being
made to benefit by the progress made in the Scottish industry and to
carry on the process on similar lines.

The Autun shale furnishes 7 to 8 per cent and that of Bruxieres 5 to
7 per cent of tar (crude oil) with a specific gravity of about 0-900.1

In Australia use is made of retorts similar to those employed in
Scotland.

1 " Genie Civil," 1908, 54, 136, et seq.

CHAPTEE IV.
THE DISTILLATION PRODUCTS.

FOUR different products are obtained from the dry distillation of
bituminous raw materials, namely : tar, consisting of liquid and solid
hydrocarbons ; tar water, containing ammonia and the organic com-
pounds of same ; gas, the gaseous products that do not condense at
the ordinary temperature and pressure ; and residue, i.e. the remains
of the raw material after the bitumen has been expelled therefrom.

A. THE TAB.

Distillation tar forms the main product of the dry distillation, and
the quantity and properties of this product decide whether a given
bituminous raw material can be profitably treated. From this point
of view — as stated on p. 1 — peat tar and wood tar cannot be re-
garded as distillation tars in the strict sense of the term, since these,
like coal tar, occur as by-products of the distillation of the correspond-
ing raw materials, whereas distillation tars form intentional main
products, and are always subjected to further treatment by distillation,
their employment as tar being out of the question.

Distillation tars consist of liquid and solid hydrocarbons of the
fatty series, associated with small quantities of aromatic, acid, and basic
(nitrogenous) substances. Oxygen compounds (alcohols and esters),
sulphur compounds, and aldehydes have also been detected in the tars.
Further details on this point will be found in Chapter X.

Lignite Tar.

The tar is yellow-brown or dark brown in colour, and has the con-
sistence of butter, at the ordinary temperature. In the melted condi-
tion it has a dark green lustre, and in some cases smells strongly of
sulphuretted hydrogen. The specific gravity, which is usually deter-
mined at 44° C. (111° F.), varies between 0*850 and 0-910. In former
days, when better raw material was available, the specific gravity of
the tar was lower, rarely exceeding 0-880. The melting-point lies
between 25° and 35° C. (or higher) ; the constituents boil at 80° to 400°,
the bulk distilling over between 250° and 350°.

Messel tar (crude oil) is greenish-brown in colour, with the con-
sistence of ointment, and a specific gravity of 0*855 to 0-860.

(52)

THE DISTILLATION PRODUCTS 53

Shale Tar (Crude Oil).

The Scottish shale tar is brown-red in colour, with a dark green
fluorescence. The specific gravity of the tar now produced is O860.
to 0-900 and over. The melting-point varies between 20° and 30° C.,
and the boiling-point of the fractions is on a par with lignite tar. The
nitrogen content is higher than that of the latter, and amounts to
1-16 to 1-45 per cent.1

The shale tar produced in the south of France '2 is a black, fluor-
escent liquid smelling like garlic. The specific gravity is 0-870 to
0-910.

Value of Distillation Tars*

The value of the tar depends, on the one hand, on the value of
the manufactured products obtained therefrom, namely mineral oil and
paraffin, and on the other on its content of acid and basic constit-
uents. These substances have to be isolated from the tar and (chiefly) its
distillates in order to form marketable goods ; and for this purpose an
outlay is incurred in labour and the cost of chemicals.

The higher the market value of the manufactured products from
distillation tar, and the lower its content of acid and basic substances,
the greater its value. Since, however, the market prices in question,
and especially those of the paraffin, are^liable to considerable fluctua-
tion, no definite pecuniary value can be fixed for the tar.

Apart from these circumstances the conditional value of lignite tar
has declined of late years, owing to the inferior quality of the raw
material, which in turn finds expression in the properties of the tar.
The specific gravity is higher than formerly, tars of specific gravity
0-820 to 0*850 being no longer obtainable. On the other hand the
melting-point has declined, a circumstance pointing to a smaller con-
tent of paraffin.

A contrast is afforded by the Scottish shale tar, which has improved
in quality of late years, owing, as already mentioned, to the superior
product furnished by the new type of retorts. The percentage of
paraffin especially has increased, as is indicated by the lower specific
gravity and the higher melting-point.

The cost of production and working up the tar have decreased all
round of late years, thanks to the improvement introduced into the
arrangement of the retorts, and to the simplification of the working
processes, whereby labour has been economized — the most essential
feature of all modifications of such processes.

B. THE TAB WATER (AMMONIA LIQUOR).

Whereas in the Saxon industry, this product is of little value, it
forms a highly important item in other distillation -tar industries ; and

1 Beilby, " Journ. Soc. Chem. Ind." 1891, 126.

2F. Miron, " Oesterr. Zeits. Berg- u. Hiittenwesen," 1S97, 45, 80.

3 See also Chapter XI.

54 SHALE OILS AND TABS

we have already seen that special stress has been laid on increasing its
content of ammonia by modifying the distillation process.

Lignite Tar Water.

About 40 to 50 per cent of the charge of bituminous lignite is re-
covered in the form of tar water ; and the proportion is still higher,
for reasons already given, when a Koerting injector is used for draw-
ing off the distillation vapours to the condensers.

The tar water has a faintly alkaline reaction. In the fresh state
it is yellow in colour, but soon acquires a reddish tinge on standing,
and finally turns red. The specific gravity is 1'02 (2° to 3° B.). The
ammonia content varies between 0*03 and 0'07 per cent, and depends
on the amount of nitroge i in the lignite.

Many attempts have been made to recover ammonia from the tar
water ; but the exhaustive researches of Grotowsky, Krey, and the pupils
of the latter unanimously demonstrated that the percentage of ammonia
is too small to make its recovery as sulphate profitable.

For some years this tar water has been used as a fertilizer, and the
systematic experiments carried out by Scheele l on a large farm proved
its suitability for that purpose. Strube 2 also has given numerical data on
the manurial value of tar water, on the basis of exhaustive experiments ;
and these favourable results have been confirmed by the experimental
station of the Halle chamber of agriculture.3

Nevertheless, in comparison with other commercial nitrogenous
fertilizers, the value of this tar water is too small to bear the cost of
transport or even of production ; and it is supplied by the distillers to
neighbouring farmers gratis.

In general the tar water is a troublesome burden to the lignite tar
works, since only a very small proportion can be disposed of in the
above mauner, and, furthermore, the water cannot in its original con-
dition be discharged as effluent into a watercourse, but must first be
purified, so far as this is at all possible. Rosenthal 4 has shown that
chemical purification is out of the question, the water containing
ammonia aldehydes, ketones, methyl alcohol, and acetonitrile.5 The
same worker also detected the presence of various organic acids, such
as acetic acid, propionic acid, butyric acid, valeriamc acid, and also of
pyrocatechin.6

The only way to purify this tar water is by mechanical treatment —
aeration and filtration ; " after which, and suitably diluted, it may be
turned into the river. Another method of utilization consists in turn-
ing it on to the spoil heaps, where it quenches the hot ashes, the bulk
of the water being then absorbed by the mass, whilst another small
portion filters through and is purified during the process. In fact, the

1 " Braunkohle," 4, 469 et seq. a " Zeits. angew. Chemie," 1904, 1787.

:J Report for 1908, p. 71. 4 Report, 1 December, 1903.

5 Rosenthal, " Zeits. angew. Chemie," 1901, p. 665. 6 Ibid. 1903, 221.

7 Report of the Royal Chemio-technical Experimental Institute, Berlin, 25
March, 1904.

THE DISTILLATION PRODUCTS

same degree of purification can be attained in this way as by the use
of costly aerating and filtering plant.

Tar water is also used for damping the lignite fuel for the retorts, and
for quenching the ashes from the grates. In many places, too, large
collecting tanks have been constructed for evaporating the tar water.

Proposals to use tar water as boiler-feed water, or even for quench-
ing coke, have had to be abandoned for obvious reasons connected with
its composition and penetrating smell.

The tar water obtained from Messel coal comprises two portions :
the small quantity already condensed previous to treating the vapours

FIG. 29.— Tower still.

with acid (p. 40) ; and the larger amount deposited subsequent to the
acid treatment. The latter is, naturally, free from ammonia, whilst
the former contains the non-volatile ammonia salts and soluble distilla-
tion products such as compounds of ammonia with fatty acids, to-
gether with pyrocatechin and its homologues ; and this portion is
subjected to further treatment. First of all, the ammonia is liberated
by the addition of alkali, and is expelled in a column apparatus, the
pyrocatechin a ad its homologues being then precipitated from the
alkaline liquor by lead sulphate, whilst the residual fatty-acid salts are
recovered by concentration. The pyrocatechin in the lead precipitate
is recovered by treating it with sulphuric acid, concentrating the solu-
tion, extracting the concentrate with ether, and recrystallizing the ether

SHALE OILS AND TARS

residue from benzol. The larger non-ammoniacal portion of the tar
water is employed as stated on p. 41, under b (condensation).

The sulphate of ammonia recovered from the tar water is char-
acterized by the entire absence of any excess of acid and cyanides, and
enjoys a good reputation as a fertilizer.

Shale Tar Water.

Until 1865, the tar water produced in the Scottish industry was
likewise regarded as a troublesome burden, and was discharged into
water-courses. This liquor forms about three-quarters of the total dis-

FIG. 30. — Henderson ammonia still.

tillate. It has the specific gravity 1*03 (4° B.) and, in addition to
ammonia, contains pyridin and other organic bases. Robert Bell 1 of
Broxburn was the first to treat the tar water for the recovery of sulphate
of ammonia. The apparatus now used is, in general, the same as in
large gasworks. The best results are obtained by the processes of Beil-
by 2 and Henderson.3

According to the Beilby process, the tar water is raised to boiling-
point by direct steam in a tower still (Fig. 29) to expel the ammonia.
Whilst the steam is admitted at the bottom through a, the tar water
enters at the top through b, and is forced to describe a zig-zag course

1 Redwood, " Mineral Oils and their By-products ".

2"Chem. Technology,'' 2, 221.

:JD. R. Steuart, " The Oil Shales of the Lothians," Part III, p. 174.

THE DISTILLATION PRODUCTS 57

by the baffles, c, d, c, d, flowing from the centre of the convex baffle
plate c. to wards the rim, where it descends through the holes o, o' on
to the concave plate d, and through the central hole m of this on to
another convex plate c, and so on, until it finally reaches the bottom
of the still, after being brought into intimate contact with the steam
entering through a.

In the Henderson apparatus, illustrated in Fig. 30, a smaller quan-
tity of steam is required. The tar water flows through a number of
trays, connected together bv gutters, as indicated by the arrows in the
figure. The transverse compartments (usually ten in number) of the
column are separated by specially arranged partitions. The steam is
compelled to force its way into the water under pressure, and thus
expel the ammonia.

The ammoniacal vapours are conducted into a vessel charged with
sulphuric acid (cracker box), this acid being, usually, the waste re-
covered from the mixing process. The resulting solution of sulphate
is concentrated, the sulphate of ammonia crystallizing out. Such of
the ammoniacal vapours as have not been absorbed in the above
vessel are passed into a second one, in which they are brought into
contact with sulphuric acid of specific gravity 1*4, which ensures
complete conversion into sulphate of ammonia; and this product
separates out. The sulphuric acid is diluted with sulphate mother
liquor, and occasionally waste acid.

The large crystals of sulphate first produced are dried by spreading
them out in a warm room, whilst the smaller crystals afterwards
formed are dried in centrifugal machines.

In order to obtain the purest sulphate of ammonia and a high
yield, milk of lime is added in the concentrating pans to decompose
the other nitrogenous compounds present and transform them into am-
monia. The commercial article is only technical sulphate of ammonia,1
but is suffic.ently pure for use as a fertilizer. In some works, the
mother liquors from the ammonia recovery process are concentrated
in vacuum pans for further treatment.

The ammonia liquor furnishes 11 to 13^ Ib. of sulphate of ammonia
person of shale.

The utilization of the ammoniacal liquor is of the greatest impor-
tance to the Scottish shale oil industry ; and if this product were not
recovered, the d'stillaticn of shale would be altogether unprofitable at
many of the works.

C. GAS.

The gas contains the bodies that have not condensed in the con-
densers. Its composition varies with the nature of the raw material
and depends on the condition of the retorts and condensers. If these
be air-tight and prevent the access of any air beyond that introduced
with the charge into the retorts, the gas will have a maximum heating

1 Mills, '• Destructive Distillation," p. 20.

58 SHALE OILS AND TABS

power and minimum of nitrogen content. The higher the latter, the
lower the value of the gas, and a large proportion of nitrogen indicates
the existence of leaks admitting air into the apparatus. By means of
carefully conducted experiments, Griife l demonstrated that the carbon
dioxide and hydrogen in the gas from the distillation of lignite in Saxon
Thuringia mainly originate in the true coal substance of the raw ma-
terial, whilst the bitumen in the latter forms the originating substance
for the formation of carbon monoxide and methane homologues. These
methane homologues are decomposition products and should be present
in merely small amount if the distillation process be properly conducted,
a high content of these bodies indicating an excessive retort temperature
or unduly dry lignite. The steam in the retort protects the tar vapours
from decomposition. If a lignite containing 50 per cent of water be
used, 1 bus. of which yields 4 Ib. of tar, there will be present in the
retort about 80 per cent of steam, 19 per cent of gas, and 2 per cent of
tar vapours.

According to Krey, 2 cwt. of lignite will yield 420 to 475 cub. ft. of
gas. In the case of Scottish shale, Henderson gives the yield on gas per
2 cwt. of material, as 1000 cub. ft., and Bryson - as 1270 cub. ft. from
the modern retorts, whereas the older pattern only furnished about
475 cub. ft. These high values are due, on the one hand, to the
almost anhydrous raw material of the Scottish industry, and on the
other hand to the circumstance that, in the present distillation process,
the decomposition of the total carbonaceous matter in the distillation
residue is secured.

The average composition of the gas from the Saxon -Thuringian
retorts is : —

Carbon dioxide . ', -.- . ' '. . 10 — 20 per cent.

Oxygen . . . . .. . . . - O'l— 3

Heavy hydrocarbons . . ;•,,.' . 1 — 2

Carbon monoxide . . . .. ^ %- . . 5 — 15

Methane. / '. '. ' ;r . ^ . , . 10—25

Hydrogen . . . . ', , . -••»;• . . 10—30

Nitrogen. . ... ', '.. ;.-»/ ..•>. . 10—30

Sulphuretted hydrogen . ;, . ...... . . 1 — 3

Grafe 3 ascertained the following composition, in which the high
content of nitrogen and oxygen naturally depresses the remaining
values. This large proportion of air is attributed to a leaky condens-
ing plant : —

Carbon dioxide . . . , ' . . ' 8-9 percent.

Oxygen . . ..." . . Y . '-. ,. 8'3

Heavy hydrocarbons . . : . . . 0'7

Carbon monoxide . . , . . . 6-2

Methane. . . . ' „.-.'. ,,-.( .• . , 6-4

Hydrogen . . , . .-..'•' . . 17'4

Nitrogen. . .' ^ v ••' v •• 48'°

Sulphuretted hydrogen . . . . ' . ' 0*45

Hydrocarbon vapours . . . • * T'' . O'l

3 " Braunkohle," Vol. IV, p. 383.

-" Journ. Soc. Chem. Ind.," 1897, p. 983.

:i" Braunkohle," Vol. IV, p. 382.

THE DISTILLATION PRODUCTS 59

The calorific value of the gas obtained in the Saxon-Thuringian
industry naturally fluctuates with the composition, and amounts to
2000 to 3000 cal.

The gas obtained from the new retorts used in the Scottish industry 1
has the following composition : —

Carbon dioxide 22-08 per cent.

Oxygen . - . 1-18

Heavy hydrocarbons . . . ' ^ • 1'38

Carbon monoxide . . ... . _. . 9-77

Methane . . . . . . .... 3-70

Hydrogen . . . ... . 55'56

Nitrogen • . .. . 6-33

The remarkable feature in this case is the high proportion of
hydrogen as compared with the gas obtained in the German industry.
This is certainly due to the action of the steam on the carbon of the
spent shale. The heating value of this gas is calculated as 2300 cal.,
and is lower on the average than the German gas, owing to the larger
percentage of moisture.

An analysis, by J. Macadam,2 of the gas obtained from the old re-
torts, shows a different composition, with lower percentage of hydrogen,
viz, : —

Carbon dioxide ... -. . 15-40 per cent.

Carbon monoxide . . ... . 10'72 ,,

Methane , ». " i. 4-02 „

Hydrogen 34-53 ,,

Nitrogen ' 35-33

In both industries the gas is rarely used for lighting, but regularly
for heating purposes in the retorts. This point has been fully dis-
cussed in the preceding chapter.

For some years, too, this gas has been employed for generating
power in the Saxon-Thuringian industry. Eolle carried out the first
experiments in this direction in the 'eighties, but without attaining any
satisfactory result. The experiments were afterwards resumed by
Krey, who, after prolonged exhaustive preliminary investigations,
succeeded in making the gas useful as a source of power for industrial
purposes. His endeavours were greatly assisted by the extensive im-
provements in gas-engine construction. At the present time, a number
of motors, of 100 to 150 h.p., are driven by this gas for generating electric
current for lighting and power.3

Previous to its application for the above purpose, the gas is freed
from sulphuretted hydrogen in the same way as coal gas, and collected
in a gas holder to compensate the fluctuating production. In the
motor it is ignited by a magneto-electric device. On account of the
contained air already alluded to, the gas is not readily inflammable.

1 " Journ. Soc. Chem. Ind.," 1897, p. 983.
2" Journ. of Gas Lighting," 1893, 2, 399.

3Gliickauf, 1901,410, Polyphase-current Plant at the Ottilie Kupferhammer
Mine ; A. Riebecksche Montanwerke, " Braunkohle," 1, 95.

60 SHALE OILS AND TARS

The gas consumption in the motor amounts to 35 to 47 cub. ft. per
h.p.-hour, and the volume produced by a retort in the same period is
about 600 cub. ft., or about 14,000 cub. ft. in twenty-four hours, from
the consumption of 95 to 110 bus. of lignite.

Numerous investigations have been made by Krey and his pupils
into the chemical utilization of the gas, and the problem has been
completely elucidated.1 There is little prospect, however, of this utiliza-
tion being practised on a manufacturing scale, the market prices of the
products rendering the operation unprofitable at present. The sulphur
of the sulphuretted hydrogen can be converted into sulphuric acid ;
and if this were generally done, a sufficient amount of acid to supply
the demand for refining the oil would be produced. The carbon
dioxHe can be employed to decompose the soda tar, the sulphuretted
hydrogen being also suitable for the same purpose.2 Krey also suc-
ceeded in transforming the carbon monoxide of the gas into formic
acid.

The hydrocarbon vapours in the gas can be recovered by scrubbing
with tar oils. This treatment, though not employed in the Saxon-
Thuringian industry is practised both at Messel and in Scotland.
There the gas from the condensers is delivered by an exhaust fan into
a coke tower (partially filled with gas coke), into the top of which
vaseline oil is introduced through a pipe, and, falling on to a distributor,
runs down in thin streams on to and between the layers of coke.
The gas enters at the bottom of the tower and issues at the top, having
been deprived of its hydrocarbon vapours. It is next passed through
a receiver filled with water, to collect any contained particles of oil
and absorb the ammonia ; after which it is turned to account for heat-
ing purposes. The benzine is expelled from the vaseline oil by blow-
ing the latter with steam, the oil itself being used over again as an
absorbent.

A more recent practice in some works is to employ wooden lattice-
work instead of coke, for distributing the scrubbing oil in the towers.

Golem an used another device for recovering the hydrocarbon
vapours from the distillation gases, namely compressing the latter
under a pressure of 6 to 7 atmospheres, accompanied by cooling down to
-5° to -10° C., which ensured the deposition of the condensable contitu-
ents.

This method, however, was only in use for a short time, being soon
abandoned on account of the expense ; and at present the light benzine
is generally recovered by the absorption method. This benzine has
the specific gravity 0'700 to 0-715.

This method of recovery is impracticable in the Saxon-Thuringian
industry, owing to the small amount of hydrocarbon vapours in the gas.
As already mentioned, these vapours are formed as decomposition pro-
ducts in distillation, and their presence in larger amount in the gas

1W. Scheithauer, "Die Fabrikation der Mineralole" ("Manufacture of
Mineral Oils "), pp. 90-91 ; Grafe, " Braunkohle," 4, 385.
2 E. Erdmann, Ger. Pat. 132,265.

THE DISTILLATION PKODUCTS 61

from the Scottish retorts is explained by the higher working tempera-
ture in these latter.

At Messel, the distillation gas is utilized in the following manner :
The largest portion (70 to 80 per cent) is employed, without purifica-
tion, for heating the retorts. Another portion serves the column ap-
paratus of the oil scrubbers (see p. 41), and still another portion is used
ior-iuising-sleam in the boilers.

The remainder of the gas (about 20 per cent) is employed for driv-
ing gas engines, after having been freed from sulphuretted hydrogen.
The Messel Co. recognized, from the first, the importance of the gas
engine, and made use of it as a source of motive power. This works
was undoubtedly the first to utilize the impure, infei ior gas for generat-
ing power, and led the way to the general application of waste gas for
driving engines. The first small waste-gas engine was set up in 1886,
and was afterwards followed by a large number of larger ones, so that
at the present time the gas-engine power at the works is about 1500
h.p., though, in contrast to the earlier practice, the gas is now freed
from sulphur before reaching the engines.

Plant for eliminating carbon dioxide irom the gas, in view of apply-
ing the latter for lighting purposes, is in course of construction. The
gas differs from coal gas by the feature, common to all dry-distillation
gases, that its carburation is due to the presence of vapours of readily
volatile hydrocarbons of the fatty series ; and when freed trom carbon
dioxide — of which it contains up to 30 per cent — it furnishes an illu-
minating gas which burns with a very bright flame at ordinary tem-
perature.

D. THE DISTILLATION EESIDUES.

We have seen that, in the Scottish industry, the watery liquor
forms an important source of income, whereas it is worthless in the
Saxon-Thuringian industry. In the case of the distillation residues,
however, the conditions are reversed. In Scotland the spent shale,
after having done good service in increasing the percentage of ammonia
in the watery liquor, is of no value ; but in the Saxon-Thuringian in-
dustry, on the contrary, the coky residue is as important as the am-
moniacal liquor in the Scottish process. In fact, when the prices of
tar products are low, many distilleries would be working without profit,
were it not for the income derived from the coke.

This coke is of granular character, and is sold in the condition in
which it occurs after quenching, namely with about 20 per cent of
moisture. The ash content, which depends on the raw material, is
about 15 to 25 per cent (when the moisture is 20 per cent), apart from
which it consists of pure carbon. Consequently its calorific power is
high, varying between 6000 and 7000 cal, according to the percentage
of ash.1 The granular character is regarded as an important feature,
since, if too dusty, its value as a heating agent is impaired.

1 " Braunkohle," 5, 783.

SHALE OILS AND TABS

It is only since about the middle of the 'seventies that the coke has
found general application for heating, having previously been removed
direct from the retorts and tipped on to spoil heaps, where it continued
to burn away for the most part, the remainder being used for road
mending. Heaps of this kind are still to be found on the sites of
abandoned works.

FIG. 31. — Lignite-coke cookery stoves.

The coke is burned in special stoves, one of which, of a simple
character, is shown in Fig. 31. The coke is placed under the grid a
where it burns slowly, the cooking utensils being heated on the grid.
A stove with two stages is illustrated in Fig. 32. The food is cooked

on the grid in the lower compartment,
and is warmed on a plate in the upper
one. The draught in the stove is re-
gulated by means of a damper k, and
the ash is collected in the ash box a.1

The stoves are mounted at a con-
venient height on a brick foundation or
iron trestles. They require little atten-
tion ; the fire burns uniformly, and will
keep alight for any length of time (e.g.
all night) if occasionally replenished with
coke. The ashes are removed at inter-
vals. These stoves are suitable for
small households, especially for cooking,
but also find employment in large agri-
cultural establishments, cabinetmakers' shops (for boiling glue and
drying glued articles), and for heating workshops. They are, how-
ever, restricted to certain districts, chiefly in the towns of Magdeburg,
Brunswick, Dessau, Leipzig, and the vicinity, whereas they are rarely
found in the lignite districts, other fuel being cheap there. On the
other hand,, they are gaining ground in other parts of Germany, and
are readily purchased as soon as their advantages are realized.

The bulk of the coke is sold as fuel, only a small proportion being
used for other purposes. Coke with a low percentage of ash, and
deep black in colour, such as is furnished by lignite poor in bitumen,

1 Stoves with improved side and top heat have recently been introduced by
the Hannoversche Grudeofenfabrik Hermann Tanzer, G.m.b.H., Hanover.

PIG. 32. — Two-stage coke stove.

THE DISTILLATION PRODUCTS 63

is ground fine and used in the preparation of black pigments (Frank-
furt black). In metallurgy, the coke is used as a reducing agent for
zinc.1 It also makes a good filtering medium, and is used as such for
drinking water and in purifying effluent waters, for which purpose it
is superior to ordinary coke (Ger. Pat. 150,362). It may also be used
for eliminating iron from water, having, like other porous forms of
carbon, the property of precipitating the iron.

To a small extent, too, this coke is used in making compressed
block fuel - which product has been successfully used for some years in
heating passenger carriages on secondary railways. The coke being
devoid of bitumen must be mixed with a dextrinous binding medium
before pressing.

So long as this coke continues to find a suffisient outlet in its original
form, there is no need to consider the suggestion that it should be made
into briquettes on a large scale, or mixed with lignite for the production
of block fuel or briquettes.3

At Messel, the distillation residue is unutilized, except for such por-
tion as is in demand by makers of stove polishes. Its application in
the retorts has already been mentioned. It is sold to the stove polish
makers in a perfectly dry condition, and, owing to the high percentage
of mineral matters, it does not give rise to dust explosions.

The mineral residues obtained in the Messel industry are divided
into a lo )se, slatey ash of extremely porou% structure, and a hard, porous
clinker. The first named is mixed with lime to make artificial bricks,
which are similar in. appearance and use to those made from Rhenish
sand. The clinker is of two different qualities : the one, produced in
the boiler fire-boxes, is not very firm, and is largely used in making
concrete ceilings, whilst the other, though of lower specific gravity and
very spongy character, is much harder and of greater tensile strength.
This grade is formed by the sintering together of the carbonaceous
residues on the spoil heaps. When cold, the mass is quarried out in
blocks, several cubic yards in dimensions, and broken down into small
lumps, which are used for building purposes, especially where capacity
to resist moisture and frost is required.

1 " Freibergs Berg and Salinenwesen," p. 315.

2 The annual production is about 60 tons.

:i" Zeits. f. d. Paraffin-, Mineralol- u. Braunkohlenindustrie," 1875, 34.

CHAPTEE V.

THE DISTILLATION OF THE TAR AND TAR OILS.

As already mentioned, the dry-distillation tars are passed on to the
mineral oil and paraffin plant after having been freed from water, as
far as possible, in the collecting tanks at the distillery plant. They
are run out of the tank cars into large iron or cement tanks, in which
an average quality product is thus collected. Owing to the fact that
the tar solidifies at ordinary temperature, it has to be conveyed through
pipes that are heated by steam. The operations in this plant are
classed under three heads : (1) distillation, (2) chemical treatment of
the tar and distillates, and (3) the production of paraffin, which divi-
sions will now be dealt with in the order named.

A. THE DISTILLATION PROCESS.

Three systems of distillation are practised : under ordinary atmos-
pheric pressure, in a partial vacuum, and by steam ; in addition to which,
mention must be made of continuous distillation and distillation under
pressure.

The object of each of these processes is to decompose the raw material
into its fractions of different boiling-points and its paraffin, by the ap-
plication of heat and by condensing the resulting vapours. In distilla-
tion at ordinary atmospheric pressure, the decomposition of the raw
material is accompanied by the formation of a cokey residue (retort
coke), the decomposition being more extensive than when the opera-
tion is carried on in a partial vacuum. In this latter case the distilla-
tion temperature is lower on account of the diminished pressure, and
the resulting vapours are less exposed to decomposition. In steam
distillation the same effect is obtained by the introduction of steam r
which envelops the distillation vapours and protects them from decom-
posing.

These methods of distillation are carried on by distilling-off the
charge in the still, and collecting the various constituents of the raw
material in succession in a condensing plant. If the apparatus be
arranged in such a manner that fresh quantities of the charge are in-
troduced without intermission, and that the individual fractions are
condensed and drawn off simultaneously at different parts of the cool-
ing plant, we then have continuous distillation.

The process of distillation under pressure consists in decomposing

(64)

THE DISTILLATION OF THE TAB AND TAR OILS

the vapours of heavy oils under a given pressure — a process which
must not be confounded with "cracking," i.e. the decomposing of the
oil vapours by superheating.

Details of the processes will be found with the description of the
various forms of apparatus.

B. TAR DISTILLING IN THE SAXON-THUBINGIAN INDUSTRY.
The Distilling Apparatus.

The apparatus consists of the stills or retorts, and the condensers
in which the condenser worms are housed. Similar appliances are
used in the distillation of coal-tar and the spirit industry.

The retorts are generally of cast iron, and more rarely of wrought
iron, but the cast-steel retorts used experimentally by Krey did not
prove satisfactory. As a rule the retort, when filled to two-thirds its

PIG. 33.— The retort.

FIG. 34.— The retort
(front view).

capacity, holds 450 to 550 gal. of tar or oil. Cast-iron retorts of larger
size than this are not used, and those of wrought iron are only found
in a few works. The shape of the retort can be seen from Figs. 33 and
34, the dimensions being about : height, 5 ft., width, 5-£ ft. at the top.
The cast-iron cover B is bolted on to the flange of the retort A, and
a tight joint is established. The cover has a spout C about 20 in,
long, and of oval section, for the discharge of the vapours. In the
centre of the cover is a manhole D 20 to 24 in. across, which is closed
by a bow and wedges when the apparatus is in operation.

The retorts are bricked round in various ways, the object in all
cases being the same, namely to utilize the heat as fully as possible
whilst protecting the retort — and the bottom of same in particular —
from direct contact with the fire. The portion of the brickwork most
exposed to heat is built of firebrick, to make it more durable. The
flames pass from the grate F towards E under the retort, and after
being divided by the partition Z are broken up by a bridge forming
eight slits a, a. These slits are widened in the rearward direction, so

SHALE OILS AND TARS

as to enable the flame to spread evenly. The bottom of the retort is
protected from the direct impact of the fire by a shield G mounted

FIG. 35. — Retort for partial vacuum distillation.

on the partition, the hot gases issuing from the slits then flowing

round this shield on their way to the
bottom and upper portion H of the
retort.

The above-described apparatus is
used when, as is frequently the case,
the distillation is conducted under
ordinary atmospheric pressure. If,
on the other hand, a partial vacuum
is used in distillation, a retort of the
type shown in Fig. 35 is employed.
This retort A is of the same shape, but
is provided at the bottom with a 3-in.
opening, fitted with an external flange
on to which is screwed a pipe L con-
nected with a main by way of a tap
H. The pipe L is protected from the
fire by a fire-brick cylinder. The
brickwork of this retort is arranged
on the same principles as already de-
scribed ; and the flames draw from
the grate F through slits to the retort. Brick ribs, built into the wall,
support the retort ; and the hot gases, after bathing the walls, pass

FIG. 36.— Distillate receiver.

THE DISTILLATION OF THE TAB AND TAB OILS

away through a flue J to the main flue V, and thence to the smoke
stack. E is a safety valve attached to the retort, and blowing off when
the pressure exceeds about 7£ Ib. per sq. inch.

« * The spout C of the retort is connected with the condenser worm
K, as shown in Fig. 36. K is about 27 yd. long and is made of leaden
or iron piping. With the latter material, the coil is formed of either
coiled gas-piping or else of cast-iron tubes— semi-circular segments
with flanges. The worm is situated in an iron cooling tank G, and is
cooled with water introduced at the bottom of the tank and removed
at the top. In the drawing, ~Rk represents the intake pipe and B'fc' the
delivery pipe. The cooling surface, per retort, is about 85 to 95 sq. ft.
When distillation is effected at atmospheric pressure, the oil con-
densing in the worm flows, as shown in Fig. 37, into a small vessel H

FIG. 37.

FIG. 38. — Distillate receiver.

serving as a gas trap, from which it is conveyed through adjustable
funnels into pipes leading to the various collecting tanks. The un-
condensed gases escape through the delivery pipe r into the outer air,
or else are collected in a gasholder for further use.

For distillation in partial vacuo, the apparatus is provided with a
suction device, acting at the end of the condenser worm (receiver), and
reducing the pressure inside the retort. For this purpose either a
Koerting injector or an air pump is employed, both of which forms have
been found suitable. The apparatus used for this method of distillation
in different works are all the same in principle though varying in char-
acter. The form shown in Figs. 36 and 38 is that used at the Webau
works of the A. Eiebecksche Montanwerke. At the end of the con-
denser worm K is mounted an elongated casting provided with a glass
window P and closed by means of a 4-way tap O communicating with
the receivers, M and M', through lateral tubes. Each receiver has a

SHALE OILS AND TAES

capacity of 33 gal. To the upper end of the casting N is screwed a
pipe r leading to a Koerting injector which sets up a partial vacuum
in the retort and alternately in the receivers (via the tubes, e and e').
A mercury vacuum gauge V, connected with the retort by a narrow
tube, indicates the extent of the vacuum produced. The main tap O is
also connected with a smaller 4- way tap o, controlling the communica-
tion between the receivers and the injector. When this communica-
tion is closed the receiver is open to the air. If, for instance, the
lever h of the tap O be turned in the position shown in Fig. 38, then
the receiver M is closed with reference to the casting N, whilst its de-
livery pipe is opened and is placed in communication with the outer

FIG. 39. — Distillate receiver for lignite tar.

FIG. 40. — Distillate receiver for
lignite tar.

air by way of the tube e. The distillate runs out of M through the
pipe I to the funnel T and into the pipe L. At the same time the re-
ceiver M' on the other hand is placed in communication with the
casting N, and through e' with the injector. The distillate from the
condenser worm runs away to M'.

By means of the window P one can' see when either of the re-
ceivers is full ; and the lever h has then merely to be turned over,
to divert the distillate into the other receiver, and empty the full one.

Owing to the tendency of a portion of the distillate to congeal in
the narrow casting N, the above apparatus is less suited for the dis-
tillation of lignite tar and the oils rich in paraffin than it is for the
oils. When lignite tar is being treated, the casting N is omitted, and
the distillate is led direct into the receiver, as shown in Figs. 39 and 40.

THE DISTILLATION OF THE TAE AND TAR OILS 69

In this case the condensing coil K terminates in a 3-way tap W,
the other two branches of which are connected with the two receivers
MM, provided with a T-piece and taps c,i. The Koerting injector
draws at c through the pipe r, and communication with the outer
air is established through i. The receivers are used alternately as in
the preceding arrangement. In the one a partial vacuum is set up
and the distillate flows through the opened connecting tap, whilst the
distillate flows out of the other by way of b when c has been opened
and the tap communicating with the condenser has been closed. At
the upper rim of each receiver is a gauge glass a which shows when
the vessel is full.

The gases drawn off by the injector are led through a cooler, where
they are freed from accompanying water vapour. This done, they are
conducted away for utilization — as described later — or allowed to
escape into the open air.

To facilitate the more accurate separation of the individual frac-
tions of distillate, in the case of the more volatile tar oils, the retorts are
provided with superimposed column apparatus, 3 to 6 ft. high, similar to
those used in the rectification of spirits, and fitted internally with per-
forated trays.

The Distillation Process.

In distillation at ordinary pressure, tke retort is charged with tar
or oil through a pipe introduced through the manhole. The terminal
length of this pipe is adapted to swivel on the main pipe, so that it can
be turned round and serve two retorts in succession. In the main
supply pipe, the material is either moved forward by the action of
compressed air from a storage vessel, or else pumped, unless — which
is the simplest plan — it descends from a high-level tank by gravitation.
The retorts are charged to two-thirds their total capacity.

If the tar has been subjected to chemical treatment before distil-
lation, about i to ^ per cent of slaked lime is added to the charge. In
some works, solid caustic soda (J to -J- per cent) or soda lye, is added to
the oils before distillation. At one time, other adjuncts, such as man-
ganese oxide or bleaching powder, were used. The object of adding
these agents is to combine the sulphuretted nitrogen liberated, and also
to lessen the percentage of creosote in the distillates.1 As a matter of
fact, the amount of creosote is slightly reduced, and the smell of the
distillate is somewhat improved ; but the sulphur content is left
untouched.

As a rule the retorts are distilled to dryness, that is to say until a solid
residue of coke is left. More rarely, only three-quarters of the charge
is distilled over, the residue in a number of retorts being transferred,
when cold, to a special retort and there distilled to dryness. Though
this latter method preserves the retorts, it is too troublesome, and is
therefore seldom employed.

1 Krug, " Hiibners Zeits. f. d. Paraffin-, Mineralol- u. Braunkohlenindustrie,^
1878, 32.

70 SHALE OILS AND TARS

When distillation is completed, the coke is removed from the cold
retorts, by the aid of broad iron tools and shovels introduced through
the manhole. Between successive distillations the condenser is cleaned
by a blast of steam introduced about the middle of the spout.

A charge of 2 to 2-| tons of tar or oil usually takes about nineteen
hours to distil, and consumes on the average 27-^ bus. of lignite for
heating the retort. Each retort is filled afresh daily, and distillation
is completed by the evening, so that no night shift is worked. One
stoker will serve eight to ten retorts, and a distiller, who sees to the
progress of the distillation and the bestowal of the distillates, has to
supervise fourteen to sixteen retorts.

The first vacuum still apparatus in the lignite-tar industry was
used by Krug, though Wagemann * had made experiments in this
direction in the early days of the industry. Krey employed the
method on a larger scale, by equipping the three mineral oil works of
the A. Eiebecksche Montanwerke for vacuum distillation in 1884,
and elaborated a system which led on the one hand to the abolition of
cleaning out each retort, and on the other enabled each retort to work
three charges (with a night shift) in twenty-four hours. The only
retorts to be cleaned out regularly were those receiving the residues
from the other retorts. It is evident that this method of working —
which was already employed in the coal-tar and stearine industries —
can be operated with a far smaller number of retorts than the others.

The closed retorts are charged by a charging pipe S (Fig. 35)
passing through the cover ; and at the same time the Koerting injector
acts at the other end of the system, in order to accelerate the charging
process. Ten retorts can be charged in as many minutes. Measure-
ing devices inserted through the retort cover enable the height of the
charge to be ascertained.

During distillation the injector is regulated so that, at the com-
mencement, the reduction in pressure is very slight, it being advisable
to allow the first distillate to undergo a certain amount of decomposi-
tion. The vacuum is then gradually increased, and, as soon as the
distillate containing paraffin begins to come over, the vacuum is raised
to 16 to 20 in. mercury gauge. In this way decomposition of this valu-
able constituent is prevented. The desired three-fourths of the charge
will have distilled over in six to seven hours ; and the residue, after
being allowed to cool down for about an hour and a half, is drawn off
from the retort by opening the tap H. The residues are collected in
an iron tank or cemented pit, and are afterwards distilled to dryness
in special retorts unprovided with any draw-off cocks, the coke being
removed in the usual manner.

The main retorts are refilled and started again ; and fifteen to six-
teen charges can be worked in a week, night shifts included. At the
end of two to three weeks, the retorts are opened to clean out the
small quantities of coke and soot that have accumulated.

1 Dingier, 139, 43.

THE DISTILLATION OF THE TAR AND TAB OILS 71

The consumption of fuel, including the heating of the residue re-
torts, amounts to 22 to 25 bus. of lignite per 2 tons of raw material ;
and the number of hands required is the same as in the other method.

Distillation in a partial vacuum has many advantages over the
ordinary-pressure method. There is a saving in fuel, the operation
being continuous — except for short periods of interruption — all through
the week, so that the capacity of the apparatus is fully utilized. New
plants should preferably be equipped for vacuum distillation, though
in the case of small works, treating about 5000 tons of tar per annum,
there is no pressing necessity for remodelling the existing plant, since,
when carried out with care, the old method presents, for these small
plants, advantages that compensate those of vacuum distillation, from
the economic standpoint.

The steam-distillation process is also employed in the Saxon-
Thuringian industry. During the process the steam is either admitted
into the upper part of the retort, above the charge, so as to protect the
vapours from decomposition and accelerate their passage to the con-
denser ; or else — the more frequent practice — is led down to the
bottom of the vessel and allowed to ascend through the charge. If
necessary, the steam is superheated in advance, especially when no
high-pressure steam is available. The steam-distillation process,
however, is usually restricted in application to two special contin-
gencies, namely, on the one hand to raismg the flashing point of the oil
by expelling the more volatile fractions, and on the other to distilling
oils of low specific gravity. In such cases the direct heating of the
retorts is dispensed with, and a closed steam coil is fitted. Gilled
pipes, connected with steam traps, are preferably used on account
of their larger heating surface. The oil is heated by the steam pipe,
and at the same time superheated steam is introduced into the bottom
of the retort.

In rare cases, steam distillation is employed as an auxiliary to
vacuum distillation.

Continuous distillation has only been introduced in the Saxon-
Thuringian industry within the last few years. It is true that for
several years in the 'eighties, C. A. Biebeck employed a French con-
tinuous process l for working up the light crude oil constituting the
first fraction from the distillation of tar ; but the results were so little
satisfactory that the process — which was really suitable only for
petroleum distillation — was abandoned.

In 1907, E. Wernecke, manager of the Sachsisch-thuringische A.
G. fiir Braunkohlenverwertung, took out a patent 2 for a continuous-
distillation apparatus, which i^ illustrated in Fig. 41. Here A is the
conical still, fitted at the top with a hood B, and at the bottom with

1 Soheithauer, " Die Fabrikation der Mineralole " (" Manufacture of Mineral
Oils"), p. 115.

aGer. Pat. 201,372. Continuous still with direct heat and internal pockets
for the charge. The apparatus is made by the Deutsche Industrie-Maschinen
G.m.b.H., Magdeburg.

SHALE OILS AND TARS

a cylindrical attachment C. From the grate / the hot gases flow
through flues e, e. The raw material is introduced through the charg-
ing pipe a, after traversing a preliminary heater. Pockets t, t com-
posed of well-fitting iron rings, are provided to receive the charge,
which overflows from each ring on to the one below. When all the
pockets have been filled, which will be the case when the raw material
begins to run out through the draw- off pipe d, the heating is com-
menced. The neck b of the hood B forms the upper exit for the
gases and vapours of the lighter fractions, whilst the vapours of the
heavier constituents escape through c, which carries a wire-gauze core
and shield D adapted to be raised or lowered with relation to the

FIG. 41. — Continuous distillation apparatus.

pipe c. The residue is drawn off through d. All the discharge pipes
are connected with condensers. Since the distilled vapours do not
come in contact with the heated walls of the still, they are protected
from decomposition. Distillation proceeds in a partial vacuum, pro-
duced by means of an air pump.

The still can be run for some considerable time without having to
be cleaned out ; and this operation is easily performed, the pockets
bein^ removable.

Young was the first to recover lamp oils from heavy mineral oils
by distillation under pressure.1 For example, he obtained 54*2 per
cent of lamp oil from an oil of specific gravity 0'902, and 48'4 per cent
from one of specific gravity 0-918. Independently of these experiments,

1 " Chem. News," 1869, 182.

THE DISTILLATION OF THE TAR AND TAR OILS

which had remained unknown, or had been forgotten in Germany,
Krey succeeded, after numerous attempts, in converting the heavy
vaseline oils from lignite tar into lamp oils, in 1887. The impetus to
these researches was given by the fact that, at the time, the market

was overburdened with these heavy oils, which were difficult to dispose
of. Krey protected his method of pressure distillation by patent (Ger.
Pat. 37,72s).1

The essential feature of the process consists in decomposing the
vapours of heavy oils under a definite pressure, in a smaller pattern of
the ordinary retort, combined with a cooler. A valve interposed be-

1 " Jahresber. des Techniker-Vereins d. sachsisch-thiiringischen Mineralolin-
dustrie," 1887.

SHALE OILS AND TARS

tween these two vessels enables the liberated vapours to pass to the
cooler only so long as the prescribed pressure is maintained, the valve
being adjusted to the desired working pressure. One and the same

heavy oil, distilled at a pres-
sure of 6 atmospheres, will
furnish a lamp oil of lower
specific gravity than if distilled
under a pressure of 2 atmos-
pheres. The heavier the pres-
sure, the larger the volume of
gas disengaged, and the more
extensive the decomposition of
the charge. The pressure dis-
tillate always contains large
quantities of dissolved gas,
which must be expelled by
means of an air blast before
the oil is subjected to chemical
treatment.

The continued fall in the
price of the lamp oil (solar oil)
from year to year, until it has
approximately reached that of
the heavy vaseline oil. has pre-
vented the method from being
applied on an extensive scale.
By the aid of pressure distilla-
tion, Engler demonstrated the
animal origin of petroleum, a
perfect lamp oil having been
produced from low grade waste
materials, such as stearine
pitch and petroleum residues.

It should also be mentioned
that, simultaneously with Krey,
Bentre l obtained a patent in
America for converting heavy
oils into light fractions by dis-
tillation ; and the same process
was patented in 1889 by Dewar
and Eedwood.2 In this case air or carbon dioxide is forced into the
still, and the operation is carried on under that pressure.

The Distillation Plant.

A number of stills, about 6 to 15, are united to a battery by being
mounted in the same brickwork setting, and provided with a common

" Chem. Technologie," pp. 205 et

2 Ger. Pat. 53,552.

THE DISTILLATION OF THE TAE AND TAB OILS 75

platform for the stoker and distiller. One large battery or several
smaller sets may be housed in a roofed-in building. In contrast to
the arrangements in the Scottish industry, all the buildings in the
Saxon-Thuringian industry are walled-in and provided with roofs of
millboard or corrugated iron — more rarely of brick. As a rule the
stoker's platform is isolated from that of the distiller in a fireproof
manner. An up-to-date distillation plant is illustrated in Figs. 42, 43,
and 44, which represent a portion of the plant at the Webau works . of
the A. Eiebecksche Montanwerke. Fig. 42 is a plan, Fig. 43 shows
the distiller's platform, and Fig. 44 a cross section through the build-

FIG. 44. — Cross- section through distillation plant building.

ing. A is the retort, B the spout or neck of same, C the condenser,
F the intermediate casting, and D,D are the receivers into which the
distillate flows and to which the Koerting injectors are connected by
means of the pipe E. C is the cooling device for the injector, whence
the gases are forced by the pump P to the gas tank K, and thence to the
gasholder. E, E are the stills for treating the residue, which flows into
them, from the main stills, through a pipe situated in the vault G. M
is the brickwork setting of the stills ; H is the stoker's platform, which
is .separated from the upper part of the stills in a fireproof manner by
means of the corrugated iron roof with clay lagging W. An iron
stairway leads from the distiller's platform to W. The flue gases

76 SHALE OILS AND TARS

escape through V to the smoke stack S. Sufficient ventilation is pro-
vided for the room by suitable roof construction.

The Distillation Products.

The products resulting from the distillation of lignite tar are crude
oil and A-paraffin mass (or hard-paraffin mass), and the separation of
these two members ensues as soon as the distillate solidifies by con-
tact with ice or with a cooled object, such as iron plate. The final
portion of the paraffin mass is of greasy character and red colour ; it is
collected separately, and is known as red product. In some works,
however, a small quantity of a substance termed paraffin grease is
separated previously to the red product. Coke is left behind in the
still, and permanent gases are given off during the distillation process,
especially towards the end.

Lignite tar of medium specific gravity (O870 to O880) furnishes on
distillation : —

* Small quantities of water.
33 per cent of crude oil.
60 , paraffin mass.

grease.

red product,
coke.

permanent gas.
The water is valueless.

The crude oil has about the same specific gravity as the original
tar, and is dark brown in colour. It boils between 100° and 350° C.

The A-paraffin mass is subjected to chemical treatment, unless the
tar was so treated previous to distillation. It is then cooled down
in a special chamber, for the separation of the paraffin, and pressed,
yielding under this treatment 15 to 20 per cent of hard paraffin scale
and A-filter oil.

The paraffin grease contains but little paraffin, and this is non-
crystalline in character. The grease is sold as such.

The red product also contains little paraffin. Like the paraffin
grease it chiefly represents decomposition products. It is returned to
the tar for redistillation, and, so far as experience goes, without in-
creasing the amount of red product obtained in the succeeding distil-
lation.

The coke is utilized as fuel, though when the distillation is carried
on without adjuncts, it finds employment for electrical purposes, but
must first be freed from final traces of contained hydrocarbons by
calcination. The heating value of the coke is 8000 to 8500 cal.

The permanent gases were formerly used for lighting and heating,
when collected at all.1 A few years back, however, Krey turned this
gas (like that from the dry-distillation process) to account far generat-
ing power in gas engines ; and several engines, operated in this manner,
are running. Before use, it must be freed from sulphuretted hydro-

1 " Braunkohle," 5, 561.

THE DISTILLATION OF THE TAR AND TAR OILS 77

gen in the customary manner. The heating value of the gas averages
7000 to 8000 cal. ; and the consumption per h.p. hour amounts to 12
to 18 cub. ft. It is preferred to use only the gas liberated during the
distillation of the oils containing paraffin (paraffin mass), trira other
distillation gases being far inferior in heating value.

According-toXirarfe,1 the gas has the following composition : —

Hydrocarbon vapours 3*0 per cent.

Sulphuretted hydrogen . . .... 3'2

Carbon dioxide . . . ^ . 2'4

Heavy hydrocarbons . . . . . . 6*8

Oxygen . . . . . . . . . . | . 3-4

Carbon monoxide . * - . . .• . 1/9

Hydrogen . . ...(.,'. . . . 4-9

Methane . -. ;» . . . . . 28 '5

Ethane '. .','.'•• . . . . 32-2

Nitrogen . . » ' -'L remainder.

The following Diagrams I and II represent the products obtained
by the distillation of lignite tar. They differ in certain points of detail,
such as the nomenclature and separation of the individual sub-frac-
tions, but are both based on the fundamental idea of separating oil as
free as possible from paraffin from the paraffin masses, and concentrat-
ing the recoverable paraffin as much as possible in these masses. At
the same time an improvement in the colour and smell of the com-
mercial oil products is sought to be attained by the distillation process.

The crude oil, after being put through a chemical treatment, is
separated by distillation into one or two oil fractions and a paraffin
mass. The separation of the oil and mass takes place as soon as the
distillate is congealed by ice. As shown in Diagram II, two oil frac-
tions, separated according to their density, are obtained from specifi-
cally light tars, before the mass. The lighter oils furnish lignite-tar
benzine, solar oil, and pale vaseline oil.

Since the distillation according to Diagram I is simpler than the
other, it will be used as the basis of the following description.

The B-paramn mass is soft, and is rendered available for use
either by the employment of refrigerating machinery, or by crystalliza-
tion in the winter. This treatment will be described in the chapter on
Paraffin Manufacture.

The crude solar oil has the specific gravity 0*830 to 0*840 and is
light brown in colour. As a rule it is subjected to chemical treatment
before distillation. In the still it is separated into lignite-tar benzine,
solar oil, pale vaseline oil, and solar paraffin mass.

The benzine has the specific gravity 0*790 to 0*810, a flashing
point of 25° to 35° C. and a boiling-point between 100° and 200° C. The
colour is faintly yellow. It is used up in the works as a scrubbing oil
in the manufacture of paraffin ; but is generally separated beforehand
into several fractions by redistillation assisted by steam.

The solar oil and pale vaseline oils (cleaning oil, yellow oil) form
commercial products, and are dealt with fully in Chapter VIII.

1 " Die Braunkohlenteer-Industrie," p. 52.

SHALE OILS AND TABS

On pressing, the solar-paraffin mass furnishes solar-paraffin scale
and gas oil, which is also a marketable product.

The A-paraffin mass yields in addition to A-paraffin scale, an A-
filter oil, which is occasionally treated chemically previous to distilla-
tion. As a rule this oil is not distilled to dryness, but only until about
5 per cent of residue is left. The distillate consists of crude oil (which
is united with that from the tars) and B-paraffin mass, which is worked
up along with that from the crude oil. < OThe residue is a tar, resemb-
ling coal-tar in appearance, and sold as " goudron ".

The B-filter oil obtained in working up the B-paraffin mass to B-
scale is decomposed by distillation into a red oil (gas oil) as free as
possible from paraffin, and into C-paraffin mass. The red oil is a
commercial article, and the C-paraffin mass is worked up, after cool-

CRUDE OIL

CRUDE. SOLAR O/

Cot<£

PARAFFIN MASS 8 FILTER OIL A A. SCALE

SOLAR OIL YELLOW OIL SOLAR PARAFFIN MASS" CRUDE OIL PARAFFIN MASS B

( f>AL£ VASeU»£ OIL ) - — »

SOLAR SCALE ?AT O/L FlL TER O/L B

PARAFFIN MASS C.

FILTER OIL C. C. SCALE

(HIMY VAS£LIN£ OIL )

DIAGRAM I. — Products obtained by the distillation of lignite tar.

ing, for C-paraffin scale, C-filter oil being obtained in the process.
This oil, which should contain only a minimum quantity of recoverable
paraffin, is sold as heavy vaseline oil, O900 to 0-920.

Diagram II shows that A-paraffin mass is sometimes called hard-
paraffin mass, and the B- and C-paraffin masses are also known as
second-grade and third-grade masses. The A-filter oil is termed heavy
crude oil. Eeference has already been made to the variations in nom-
enclature and definition.

In the recovery of the individual fractions, the condition of the
market has also to be borne in mind, according as the non-paraffin
oils are destined for purposes making special requirements in respect
of specific gravity, flashing point, colour, and smell.

The distillation of the press oils remains to be considered. As will
be seen from the subsequent description of the process of manufactur-

THE DISTILLATION OF THE TAR AND TAR OILS

ing paraffin, these oils consist of the light lignite-tar oils used for scrub-
bing, and of the mineral oils adhering to the crude paraffin and whose
elimination is the object of pressing. The benzine is recovered from
the press oils either by distillation with the aid of steam, the residual
paraffin mass being afterwards cooled, or else the press oil is cooled
direct. The oil obtained from the press oils in the pressing process
is separated by distillation into benzine, or crude solar oil, and a
paraffin mass.

The Retorts.

It has already been stated that small cast-iron retorts are used in
most works. When distillation is conducted to dryness, at ordinary
atmospheric pressure, these retorts are worn out in about six to eight

COKS

LIGHT CRUDE PHOWC.EN PALEVASELINE SOLAR PARAFFIN MASS HARD SCAL

BENVNE SOLAR OIL PALE PARAFFIN SOLAX'/AJ '£f»OE SOLAR ^ NO. GRADE TAR
OIL SCALE* OIL PHOTOGENJI. OIL I. PARAFFIN MASS

(CLEANING ou..r£it.o» OIL ) |_ ---^^z===:=:"r' ""~""-7>-t^/

PALE PARAFFIN OIL SOLAR PARAFFIN MASS ZND. GRADE PARAFFIN MASS

GRADE SCALE

GAS OIL /'ALE 3RD. GRADE MASS

DARK 3RD. GRADE MASS

GAS OIL ZNO GRADE~SCALE HEAVY VASELINE OIL
DIAGRAM II. — Products obtained by the distillation of lignite tar.

months ; but with vacuum distillation, the only retorts subjected to ex-
tensive wear are those in which the residues are distilled, whereas the
others have a much longer working life, the tar retorts lasting six to eight
years and the oil retorts more than ten years. All cast-iron retorts,
even when carefully selected, are liable to crack after a certain time,
if they have been strongly heated, such cracking, however, being found
by experience to be due to cooling and not to heating. Consequently,
particular attention must be bestowed on this point.

It is impracticable to stop up the cracks, or to close them by elec-
trical welding, the only way to repair them being to cover them with
patches of cast iron 1 to 1| in. thick, applied to the outside of the
cleaned retort and well cemented. If this operation be carefully per-
formed and the retort mounted so that the patch is not in direct con-
tact with the fire, it will not break again at the same place, and the

80 SHALE OILS AND TAKS

patch will stick on well. For every 100 Ib. of tar worked up into
marketable products, Grafe l calculates the wear of the retort to amount
to 0'4 Ib. when vacuum distillation is employed, whilst for distilla-
tion at ordinary pressure a smaller allowance — about 0'3 Ib. — will
suffice.

The retorts discarded as no longer suitable for the distillation of
tar and oil, can still be used for distilling the waste products, acid
i-esins.

C. THE MESSEL DISTILLATION PBOCESS.
Apparatus for and Method of Distillation.

The distillation tar or crude oil is freed from water as much as
possible and is pumped into high-level tanks, in the usual manner,
from whence it is drawn off into the stills, which are made in two
parts and are large enough to hold a charge of 1600 to 1700 gal.
Distillation is conducted in a partial vacuum and is facilitated by the
action of stirrers. The thick residue is drawn off into retorts in which
it is distilled to a cokey residue. These retorts alone need to be cooled
down considerably for the purpose of entering them and removing the
incrusted contents, the other stills being worked continuously. Tubular
condensers, each provided with two receivers, are used. The partial
vacuum is maintained by means of slide-valve air pumps, fitted with
mercury gauges for measuring the vacuum produced. The stills and
retorts are chiefly heated by burning the acid and alkali tar from the
mixing plant.

The Distillation Products.

The distillates from the residue retorts are united with the tars and
decomposed into a light and a heavy fraction, the former amounting
to 16 per cent and the latter to 76 per cent. After chemical treatment,
the first fraction is redistilled, and furnishes, on the one hand, naphtha
and crude lamp oil, and on the other, gas oil. The heavy fraction re-
presents paraffin mass, and after chemical treatment is redistilled.
This process yields a small proportion of light oil, which is used direct
as gas oil.

There is no separation of the heavy portion into soft and hard
paraffin masses, the two being collected together and crystallized by
cooling. The cooled mass is filtered in a press, and the press oil is
collected, cooled down to - 2° C. and filtered again. The last filtrate is
either used direct for gas oil, or occasionally worked up into lubricating
oil. The lamp oil is treated to bring the colour and smell to a high
state of perfection ; but in spite of its low density (0-800) has such a
high viscosity and low capillarity when burned in lamps that it cannot
nowadays compete with ordinary petroleum.

1 Grafe, "Die Braunkohlenteer-Industrie " (" Lignite-tar Industry"), p. 56.

THE DISTILLATION OF THE TAB AND TAR QJ&fr y(j $J,«3

:!•;-
D. THE DISTILLATION PROCESS IN THE SCOTTISH INDUSTRY. '8i;if>

Apparatus for and Method of Distillation.. ...•--.- .,o (Oj .,...,

Atone time the Scottish shale tar, or crude oil, was 'distiH^cf^jri1
retorts similar to those used in the Saxon-Thuringian in<fust^ffi;ne
other oils being distilled in large stills with a capacity of 's$8w
cub. ft.1 In both cases the distillation was assisted by steam, and.
several fractions were subjected to chemical treatment.

At the present time, however, the Henderson 2 continuous proceMk ^
of distillation is generally employed for the tar. The apparatus was
patented in 1885.3 A still in the shape of a boiler with corrugated
bottom, and holding about 10 tons, is connected with two* similar stills
arranged at the side and in turn connected by means of pipes with a
row of six small coking stills of the form illustrated in Fig. 45. The
upper part A of the coking still is of
steel, and the lower part B of cast iron.
The tar is distilled in the three large
stills, the residue being distilled to dry-
ness in the six small stills, of which
two only are working at a time. The
tar is passed through a preliminary
heater — which is heated by the effluent
vapours from the stills, and therefore
also acts as a condenser — and fed into
the middle still. Here the light fraction
(naphtha) is distilled off. The heating
of this still is regulated in such a
manner that only the aforesaid light
fraction is eliminated from the con-
tinuously fed tar, whilst the heavier
fractions of the tar flow continuously

along the rear wall of the still into the two lateral stills. These are
more strongly heated and expel the second fraction (green oil) con-
tinuously. The residue from these second stills is led to the coking
stills and distilled to dryness, the distillate being united to the green
oil.

The distillation process is continuous, commencing in the middle
still — in which the tar feed pipe dips into the charge — and is continued
in the two lateral stills, which are fed through a pipe opening only a
short distance above the bottom of the middle still.

The coking stills require cleaning out after each charge, for which
reason three pairs of these stills are provided, as mentioned above.

By carefully maintaining uniform heating temperatures, the pro-

lSee Scheithauer, "Die Fabrikation der Mineralole" ("Manufacture of
Mineral Oil"), p. 118.

2 Steuart, "Economic Geology," 3, No. 7 ; " The Shale Oil Industry of Scot-
land," p. 584.

3 "Chemical Technology," 2; " Lighting," pp. 221 et seq.

FIG. 45. — Small coking still.

82 SHALE OILS AND TARS

cess yields distillates of constant composition, and is very economical
in comparison with the older distillation processes. The operation is
assisted by steam.

Each still is provided with a separate condenser for the distilled
vapours.

As a rule, the stills employed for the various kinds of oil are very
similar to, or identical with, those used for the crude oil. One of these,
patented by Henderson in 1883, is shown in Fig. 46. It consists of
three horizontal stills, A, B, and G, about 33 ft. long and 8^ ft. wide.
At the bottom of each still is a draw-off pipe a, the feed pipe b being
arranged at the same end wall. Whereas, however, a is attached to"
the still wall by means of a flange, the pipe b passes through this
wall and right through to near the other end of the still, so that the
oil enters and leaves the still at widely separated points. The oil to
be distilled is fed into A, where the lightest fraction is distilled off;
after which it flows through b into B, where the second fraction is

FIG. 46. — Horizontal stills with retort.

expelled, the third fraction being driven off in C, and the residue dis-
tilled to dryness in the retort D. The process is therefore the same
continuous distillation as already described in the case of tar. The
oil flowing continuously into A is warmed by the escaping distillation
vapours in the condenser, which, in the case of each still, consists of a
pipe about 66 yd. long and 4 in. in diameter.

Young and Beilby l have devised a somewhat different apparatus
for continuous distillation. A large horizontal still is divided by cross
partitions into a number of intercommunicating compartments tra-
versed by the oil. The heating of the several compartments being
different, only a certain fraction is distilled off in each and collected
separately in a condensing device. In the first compartment, where
the fresh oil is admitted, the lightest oil is vaporized, the remaining
portions flowing into the second compartment where the secon^ frac-
tion is distilled off, and so forth.

This form of apparatus is used for the lighter oils, whereas the
heavier oils, e.g. blue oil, are distilled in retorts such as shown in
Fig. 47.

»" Chemical Technology," 2 ("Lighting"), p. 227.

THE DISTILLATION OF THE TAR AND TAR OILS 83

All the distillations are effected by the aid of steam ; and about 20
per cent of condensed water is
obtained in the case of the
heavy oils.

Distillation Plant.

As already stated, the dis-
tillation plant is of the simplest
character. The battery of stills,
containing a -large number of
apparatus, has neither walls nor
roof ; and even the boiler-house
(if it may be so called) consists
merely of the brick-mounted
boilers without any other pro-
tection. Though this system
may be justified by the mildness
of the climate, it seems — in
view of the heavy rainfall in FlG- 47.-Retort for heavy oils.

Scotland — to rest more on tradition than convenience.

The Distillation Products.

Diagram III illustrates the course of distillation as. practised at>
Broxburn, one of the largest Scottish works. The shale tar is decom-
posed into two main fractions, naphtha and green oil.

The naphtha, on distillation after chemical treatment, furnishes-
two light oils, of specific gravity O730 and 0*740, the residue being
united with the green oil.

The green oil is chemically treated, and is then separated by distil-
lation into three fractions : light oil, heavy burning oil, and hard-
paraffin mass. After chemical treatment, the light oil is distilled and
yields naphtha, lamp oils of specific gravity, 0*785, 0-800 and 0-810,
and a soft-paraffin mass. The heavy burning oil, forming the second
fraction from the green oil, is chemically treated and distilled into
burning oil (united with the light oil previous to distillation), soft-
paraffin mass and hard-paraffin mass.

The soft-paralfin mass is united with that from the light oil, and on
further treatment yields soft-paraffin scale and gas oil (specific gravity,
0-850).

The hard-paraifin mass is also sent to the paraffin works for treat-
ment, under which it furnishes hard-paraffin scale (which will be dealt
with later) and blue oil. This latter is chemically treated and distilled,
yielding two lubricating-oil fractions. Both are sent to the paraffin
department and furnish soft-paraffin scale and lubricating oils of
specific gravity 0-865 and 0-885.

In other works the oils, which are classified according to colour as

SHALE OILS AND TAES

well as the purpose for which they are intended (lamp oil, gas oil,
lubricating oil), are partly known by different names. The scheme of
distillation (Diagram IV) is also simpler.

SHALE

N APT HA

NAPTHA 0.730. NAPTHA 0.74Q. RESIDUE L/GHTO/L HEAVY BURNING HARD PARAFFIN RETORT Co«£

SOFT PARAFFIN
MASS*- . .

HARD PARAFFIN BLUE OIL HARD PARAFFIN
MASS ^^ SCALE

NAPTHA LAMPO/L LAMP OIL LAMP O/L
Ores Oaoo O.a/q^.

PARAFFIN LUBU'ICTM&O/L
QA

LUBRICATING OIL

6 AS O/L SOFT PARAFFIN SCALE LUBRICATING SOFT SCALE LUBRICATING SOFT SCALE

0.850 0/LO.S6S OlL 0.885

DIAGRAM III. — Distillation of shale tar (crude oil) as practised at Broxburn.

5 Eetort coke and retort gas are other products of the distillation
process. The coke which represents about 3 per cent of the tar, is a
valuable article, and is used for making black pigments and for electri-
cal purposes.

4
SHALE TAR

*COK£

NAPTHA LAMP O/L MEDIUM O/L

LAMP O/L

6 AS O/L
0.850

HARB SCALE GREEN O/L
BmTO/L

SOFT SCALE LUBRICATING OIL

DIAGRAM IV. — Distillation of shale tar (crude oil) by classification of the

various oils.

The retort gas is used for lighting l and heating, and, according to

1 The small town of Broxburn is lighted with retort gas from the Broxburn
Oil Co.'s works.

THE DISTILLATION OF THE TAE AND TAB OILS 85

Beilby,1 has the following composition : —

Heavy hydrocarbons 14-5 per cent.

Methane and homologues .... 59-0 „

Ethane 26-5

Hydrogen traces.

No carbon dioxide, carbon monoxide, or oxygen has been detected.

In the condensing apparatus, the retort gas deposits a light ben-
zine, which, during the last few years, has found employment as 'motor
spirit.

1 Humphrys, " The Chemistry of Illuminating Gas," p. 172.

CHAPTER VI.

I. CHEMICAL TREATMENT OF THE TAR AND ITS DISTILLATES.

THE chemical treatment of the tar and its distillates is termed refining,
and is performed in agitators.

A. THE REFINING PROCESS.

Distillation separates the several fractions of the tar, and effects
their purification, with an improvement of the colour and smell, retort
coke and retort gas being produced. A further purification of the dis-
tillates is effected by chemical treatment with sulphuric acid and
caustic soda, which remove substances which either have an unfavour-
able influence on the colour and smell or lessen the suitability of the
oils for use. These substances mainly consist of basic and acid con-
stituents and of dark-coloured heavy hydrocarbons.

The sulphuric acid for the preliminary treatment is of specific
gravity To3 (50° B.), a stronger acid (specific gravity T84 or 66° B.)
being used for the treatment proper. Concentrated or fuming acid is
not used, experiments having demonstrated its unsuitability for treat-
ing heavy tar oils, though it can be advantageously employed in re-
fining petroleum. The acid is obtained in tank cars — rarely in glass
carboys.

The caustic soda has the specific gravity 1-36 to 1-38 (38° to 40° B.),
and is prepared in the works by dissolving drum soda in water.

Other chemical reagents, such as hydrochloric acid and nitric acid,1
and other methods of refining, have been tried from time to time and
recommended in the literature, but have not found practical applica-
tion.'2

The preliminary acidification with dilute sulphuric acid eliminates
any residual traces of water, and a portion of the basic constituents,
such as pyridin bases, which are soluble in dilute acid. The stronger
acid (66° B.) then used extracts from the oils all the basic substances
and a portion of the unsaturated hydrocarbons which give the oil a
dark colour by oxidation and resinification. The treatment also pro-
duces oxidation, revealed by the strong smell of sulphur dioxide, whilst
polymerisation and substitution can also be observed. The chemical

1 Austrian Patent No. 10,253, 1901.

2W. Scheithauer, "Die Fabrikation der Mineralole " ("Manufacture of
Mineral Oils "), pp. 139-40.

(86)

CHEMICAL TREATMENT OF TAB AND ITS DISTILLATES 87

processes which go on during the sulphuric acid treatment are difficult
to follow and have not yet been fully elucidated.1 In order to prevent
excessive decomposition, the acid is allowed to act in the cold, unless
other conditions are rendered necessary by the products (paraffin mass
or tar) under treatment. The acid resins, resulting from the sulphuric
acid treatment, settle down to the bottom of the agitator and are re-
moved, which done, the oil is washed with water, to remove the last
traces of free acid, and is treated with caustic soda. The tar itself is
never mixed with alkali, but only its distillates. The actual alkali
treatment is preceded by a preliminary alkalinification, a small quan-
tity of lye or regenerated lye being added to neutralize the traces of
acid and absorb the particles of water, this lye also, of course, dissolv-
ing acid bodies present. The subsequent treatment with larger quan-
tities of caustic soda extracts the acid bodies : homologues of phenol,
etc., known by the generic name of creosote,2 which impart a disagree-
able smell to the oil and, like the unsaturated hydrocarbons cause the
colour to darken afterwards. According to Grafe,3 the solvent capa-
city of these substances towards paraffin also adversely affects the yield
of that constituent. The product of the reaction is known as soda tar.
This treatment is usually succeeded by washing with water, to remove
the traces of alkali.

The two reagents are now used in the order given above, whereas
it was formerly the practice to employ the alkali first, and then the acid.
The consequences of the two chemical actions were regarded as imma-
terial, which is erroneous. On the one hand these tar oils contain
substances which are soluble both in sulphuric acid and caustic soda,
and it is advisable to allow the cheaper reagent, the sulphuric acid, to act
on them. On the other hand the product of the reaction with soda is
more easily washed out with water, and is also less soluble in the oils
themselves than are the products of the acid reaction, so that secondary
decompositions are more easily avoided in the subsequent distillation
of the treated oils.

B. THE REFINING PROCESS IN THE SAXON-THUBINGIAN INDUSTRY.

The Agitator.

The agitators or mixers generally used consist of cylindrical vessels
with conical bottom, varying in dimensions according to the amount
of oil to be treated, and holding from 1100 to 4400 gal. Vessels of
different shapes 4 were formerly used, mostly of wood ; but these have
now been entirely superseded by iron vessels, lined with sheet lead
about o ae-fifth of an inch thick. This lining is necessary to protect
the walls of the vessel from the action of the acid, especially the dilute

1 Compare Palui, " Chemiker Zeitung," 1900, 969.

2Tne name relates to its disinfectant action, and is derived from creas (flesh)
and sozo (I preserve).

3 Grafe, " Die Braunkohlenteer-Industrie " ("Lignite-tar Industry"), p. 59.

4 Scheithauer, " Die Fabrikation der Mineralole," p. 131.

SHALE OILS AND TABS

form. The purest lead should be used, this being least corroded by
the sulphuric acid.1

The agitator is usually covered by a lid, provided with an observa-
tion flap ; and in many works the vessel is fitted with a pipe for con-
veying the liberated gases into the outer air without allowing them to
escape into the room.

In the early days of the industry, the oil and chemicals were
mixed together by means of wooden paddles worked by hand ; but
these were afterwards replaced by mechanically operated stirrers ; 2 and
for some years past, the mixing has been effected by blowing air into
the oil and chemicals in the agitator. The duration of the process
being short, the chemical action of the air may be disregarded.

Fig-. 48 represents. an agitator A. The charge of oil is introduced
through the pipe a, and the acid, alkali, and
^ &rf~ water separately through the pipes b, c, d re-

^^^~a TrfC^ spectively. The air is blown in through a
leaden pipe e which extends to the bottom of
' the vessel. The products of reaction and the
washing water are drawn off through the tap
G, whilst the treated oil is removed through
the tap F.

If, as already mentioned, the material
under treatment has to be warmed previous to
chemical treatment, this is effected either by
means of an internal lead coil or by a steam
jacket.

The Refining Process.
Formerly the chemicals were transported
FIG, 48.— The agitator ^y hand (buckets and hoists), but at the pre-
sent time they are introduced mechanically by

the aid of pipes. A suitable arrangement for this purpose will be
described under the heading of " The. Eefinery ".

The Chemical Treatment of the Tar.

In some works the lignite tar is still subjected to treatment with
sulphuric acid previous to distillation. This method was first intro-
duced by B. Hiibner,3 and has many advantages over that in which
the crude tar is distilled. In distillation, tar that has been treated
with sulphuric acid disengages less noxious gases, the retort coke is re-
duced by about 50 per cent, and the loss of gas is considerably smaller
than when the crude tar is distilled ; whilst at the same time the re-
torts suffer less injury, because less heat is needed for distillation.
The creosote content of the distillates is smaller, and with certain tars

' Lunge and Schmidt, " Zeitschr. f. angew. Chemie," 1892, pp. 642 and 664.

2Scheithauer, I.e. p. 131 et seq.

:f " Berichte d. Deutsch. Chem. Ge*.," 1868, p. 133.

CHEMICAL TREATMENT OF TAR AND ITS DISTILLATES 89

an appreciably higher yield of paraffin is obtained. Some practical
authorities, however, hold the opposite view, and believe more paraffin
can be recovered when the tar is distilled crude. This divergence of
opinion is probably due to the fact that only tars free from bitumen
should be treated with sulphuric acid. If, however, the tar contain
bitumen, this substance dissolves to a large extent in the acid, so that
some of the paraffin formers are destroyed, the loss of paraffin being
thereby explained. It is not difficult to regulate the dry distillation
in such a manner that the tar is obtained free from bitumen without
suffering any considerable decomposition.

If the tar be distilled crude, the paraffin masses must be refined —
an operation entailing great care — and, in particular, a thorough final
washing is essential to prevent corrosion of the filter and press cloths.
The crystallization of the paraffin is better when the mass is allowed
to crystallize without refining after distillation.

The tar is freed from water by treating it with J per cent of sul-
phuric acid of 50° B. strength, or 1 to 2 per cent of recovered acid,1
and is then treated with 3 to 4 per cent of acid of 66° B. strength for
a quarter to half an hour. The tar is next left alone for three to four
hours, to allow the reaction products to settle .down, whereupon the
acid resin is drawn off. Hot water is now cprayed over the surface,
and milk of lime is mixed in for about a quartci of an hour, to neutral-
ize the residual acid, the tar being ready for distillation after the lime-
water and deposite.1 sediment have been drawn off. This washing
process requires great skill and care, owing to the tendency to form
emulsions which result in loss of tar.

From the above it follows that the practice of treating the tar with
sulphuric acid previous to distillation is now still justifiable ; though
where distillation in a partial vacuum is practised there may be im-
portant reasons for giving preference to the other process.

Refining the Tar Products.

The proportion of sulphuric acid used in the chemical treatment of
the tar products depends on the character of the raw material and
varies in different works. The point to be kept in mind is to obtain a
marketable product in respect of colour and smelL As a rule 2 to 5
per cent is taken, or 6 per cent at the most. If more than 3 per cent
be employed, the main acid treatment is divided into two separate
stages. As in the case of oil refining, the products of the reaction are
left for some time to settle down. After drawing off the acid resins,
two successive washings are given with water, the mixture in each case
being agitated for a quarter to half an hour and left to settle about two
hours. In order to accelerate and complete the neutralization of the
acid, the water is sometimes given a small addition of sodium carbon-
ate, caustic soda, caustic baryta, or, as in treating the tar, caustic lime.

"''Recovered acid is that recovered in the works from the spent acid from pre-
vious operations. . '

90 SHALE OILS AND TARS

The acid process is followed by treatment with caustic soda. After
a preliminary treatment with about -^ per cent of caustic soda lye, the pro-
ducts of this reaction are drawn off at the end of about an hour. Then
follows the main treatment which is really one of " leaching," since
the whole of the creosote, for example, must be eliminated from the oil.
The amount of alkali used must be calculated so as to secure this re-
sult. The accuracy of the treatment is easily checked, by experiment-
ing with a small quantity of material in a test tube, and the requisite
additional amount of alkali determined. The quantity varies between
4 and 8 per cent of caustic soda in different works. As a rule 3 to 4
per cent is used at a time and mixed for half an hour, the whole being
then left to settle down for three to four hours, and the oil afterwards
distilled either direct or (as is done in some works) after washing
out the surplus alkali with water.

The loss resulting from the chemical treatment (waste in refining)
varies, of course, in different works. It depends on the character of
the oil, and particularly on the percentage of creosote.

Assuming that the tar has been acidified, the following tar products
of those mentioned in Diagram I are subjected to chemical treatment.
The A-filter oil (2 to 4 per cent of sulphuric acid, 66° B.) the crude oil
(3 to 4 per cent of acid), the crude solar oil (1 to 2 per cent of acid),
and if necessary the lignite tar benzine (1 to 2 per cent of acid). In
all cases the agitation lasts a quarter to half an hour, the time de-
pending on the quantity of oil in the agitator. All the oils are freed
from creosote before being distilled.

When the tar is distilled crude, then, according to Diagram II, the
following products will be chemically refined : the light crude oil (with
3 to 6 per cent of sulphuric acid, 66° B.), the hard-paraffin mass (3 to
6 per cent), the light crude photogen (4 to 5 per cent) and the benzine
(2 to 3 per cent of acid). In this case also the- creosote is completely
extracted from the products in question by treatment with caustic soda
lye of 38° B. strength..

Treating the Oils before Delivery.

Of the commercial oils, only the paler kinds are treated chemically
before being sent out ; and this is done in only a few works.

Solar oil is treated with small quantities of sulphuric acid and then
washed with dilute caustic soda, or sodium carbonate solution. In
other works it is treated for about two hours with a mixture of -£ per
cent of caustic soda and ^ per cent of spirit, to improve the smell.

The light vaseline oils, cleaning oil, and yellow oil, as also the gas
oil are treated, if necessary, with 1 to 3 per cent of sulphuric acid and
then with caustic soda lye, also wiih dilute sodium carbonate or sodium
silicate l solution, the last named being found very useful for pale
yellow oils.

In contrast to the practice adopted in the case of intermediate pro-

1 Recommended by J. Zahler, ".Chem. Ztg.," 1897, pp. 853 and 899.

CHEMICAL TEEATMENT OF TAB AND ITS DISTILLATES 91

ducts, the refining of the finished or commercial products is usually
carried on in two separate vessels for the two reagents ; the oil being
pumped into another agitator after being washed at the end of the acid
treatment.

Sun- bleaching, in order to improve the colour of commercial oils,
is not practised on a manufacturing scale, being too cumbrous and
tedious ; but it is always efficacious.

In order to obtain good, marketable products, the chemical refining
of lignite tar and its distillates entails an average consumption of 6 to 7
per cent of sulphuric acid and 0'8 to 1/3 per cent of caustic soda, cal-
culated on the weight of the raw material. The amounts will not
be smaller except in the case of tars of such good quality as is now
rarely produced.

FIG. 49. — Plan of agitator house.

If, as occasionally happens, it is de -sired to destroy the bluish-green
fluorescence of the vaseline oils before admitting them into commerce,
they are mixed for some time with O25 to 0'5 per cent of nitro-naphtha-
lene. On being left at rest, the nitro-naphthalene sinks to the bottom
and can easily be separated from the oil.

It should also be mentioned that pyridin bases were formerly re-
covered from the first tar distillate (crude oil) by treatment with sul-
phuric acid of 30° B. strength. The acid resins were separated from
the sulphuric solution by settling and filtration through retort coke,
and the solution was then decomposed with dilute caustic soda, the
bases being dried and fractionated by distillation. They were sold for
purifying anthracene and denaturing spirit. For some years, how-
ever, their preparation has been abandoned since they were unable
to comply with the stringent requirements — in respect of boiling-
point and solubility in water— to be fulfilled by bases employed for
denaturing.

SHALE OILS AND TABS

The Agitator House.

Figs. 49 and 50 illustrate a plan and longitudinal section of an
agitator house. A, A are the agitators, mounted on a brick foundation
and shaped like the one shown in Fig. 48. B is the air pump which
forces air in through the pipe e. C is the sulphuric acid tank, from
which it is drawn in suitable quantity to the agitators through the pipe
b, whilst D represented the caustic soda tank connected with the
agitators by the pipe c. The acid is forced into C from a pressure tank
E by compressed air, and the caustic soda solution is forced by similar
means from the pressure tank F, after being prepared in the vessel S.
The products of the reactions are drawn off through G and delivered
through pipes g, h to tanks H, J, K, where they are collected for
further treatment. A stage E, E, resting on pillars, runs alongside
the agitators. L, M, N, O, P are oil- storage tanks, and T, T are pres-
sure tanks.

FIG. 50. — Longitudinal section of agitator house.

Most agitator houses are arranged on these lines, their dimensions
and those of the vessels used varying according to the quantity of oils l
to be treated, and therefore the amount of tar at disposal.

Whilst corrugated sheet iron has advantageously replaced mill-
board as a roofing material for industrial buildings, it cannot be used
for agitator houses as the metal would be rapidly corroded by the sul-
phurous acid given off and condensed.

C. EEFINING PROCESS IN THE MESSEL INDUSTRY.
The distillation tar (crude oil) is not chemically refined, but the
first fraction of distillate is mixed successively with 2 per cent of sul-
phuric acid and 3 per cent of caustic soda. The crude mass is treated
in the same way. The deposited acid resins are washed with water
and burned to heat the stills. The agitators lor the acid treatment
are lined with lead.

'Krey, " Journ. f. Gasbel.," 1890, p. 408.

CHEMICAL TREATMENT OF TAR AND ITS DISTILLATES 93

D. EEFINING PROCESS IN THE SCOTTISH INDUSTRY.
Methods.

Sulphuric acid (66° B.) and caustic soda are also used for the
chemical refining of the oils in the Scottish industry ; and with few
exceptions — in contrast to former practice — these reagents are used in
the order given. The sulphuric acid is required to be of high purity
and free from arsenic and selenium. The large works, like those at
Broxburn, produce their own sulphuric acid in a special department.

Whereas in the Saxon-Thuringian industry it is the general rule
to carry out all the refining processes in the same vessel, a separate
agitator is used for each process in the Scottish works. Two wrought-
iron vessels, mounted one above the other, are employed, the sulphuric
acid treatment being performed in the upper one and the caustic soda
treatment in the lower one.

At one time the agitation was affected solely by means of stirring
mechanism built into the agitators ; but now most works — like those
in Saxon Thuringia — use compressed-air agitators. Stirrers are only
used for treating the light oils, such as naphtha, in order to avoid the
losses that would arise from blowing-in air.

The tar is never chemically refined, being itself produced by steam
distillation and therefore containing largfc quantities of undecomposed
bitumen, which has to be transformed into hydrocarbons by distilla-
tion, and would dissolve in the sulphuric acid.

Chemical Treatment of the Tar Products.

The tar distillate ("green oil " of Diagram I) is mixed with 3 to 4
per cent of sulphuric acid for a quarter to half an hour, the reaction
product being drawn off at the end of three to four hours. In some
works, as in the Saxon-Thuringian industry, this operation is preceded
by 'a treatment with sulphuric acid of 34° B. strength, or else with
acid previously used for refining oil. After the sulphuric acid process
the oil is run into the lower agitator, where the acid is neutralized with
dilute caustic soda of 38° B. strength (about -£ per cent). When the
product of this reaction has settled down it is drawn off, and the oil
is then mixed with 2 to 3 per cent of caustic soda lye (38° B.) for half
an hour. The mixture is left as long as possible — three to six hours
or occasionally over night — and the soda tar is removed.

The light oil furnished by distilling the green oil, is mixed for a
quarter to half an hour with 2£ to 3£ per cent of sulphuric acid
(66° B.) after a preliminary acidification. The acid resins are removed
at the end of two hours, the acid being neutralized with dilute caustic
soda in another agitator, and the oil treated with 2| to 3| per cent of
caustic soda (38° B.) for a quarter to half an hour. After leaving to
settle for two to three hours, the soda tar is drawn off.

In addition to the above, the following oils mentioned in Diagram I
are treated with varying quantities of sulphuric acid and freed from

94 SHALE OILS AND TABS

creosote by treatment with caustic soda : naphtha, heavy burning oil,
burning oil, and blue oil.

In some works chemical treatment is applied to other oils and also
to the paraffin mass (" heavy oil ").

Most works treat the oils before sending them out, the lamp oils
and lubricating oils in particular. The oil is mixed for a short time
with a small percentage of sulphuric acid, and washed with dilute
caustic soda (3° to 5° B.) or sodium carbonate solution after the removal
of the acid resins.

II. THE UTILIZATION OF THE REFINERY WASTE.
USES AND TREATMENT.

The acid resins are like coal-tar in appearance and have a pene-
trating sulphurous smell. At some works in Saxon Thuringia instead
of treating the acid resins and soda tar separately, the two products are
mixed, whereupon the creosote and resins are thrown down and a
solution of sodium sulphate is formed.

It is preferable to decompose the acid resins separately by boiling
them with steam admitted into the bottom of the vessel, the resins
separating out on the surface of an impure dilute sulphuric acid. This
waste acid or recovered acid, has the density 30° to 40° B., is of a.
brown colour and, after being completely freed from resins, is used
either in the preliminary acid treatment in refining or for decomposing
the soda tar. It also finds employment in manure works l and may
— as was formerly the case in many works — be used in the prepara-
tion of salts of iron and zinc, which metals it dissolves. When em-
ployed for decomposing the soda tar, it furnishes Glauber salt, which
is purified by recrystallization, in some works, and put on the market.

The resins are distilled in retorts similar in shape and mounting to
those already described. The vacuum process is not employed, but
generally superheated steam is blown in at the bottom of the retort.
The distillation furnishes an oil, creosote oil of specific gravity 0'94U to
0-980 and soluble to the extent of 50 to 70 per cent in caustic soda.
It smells strongly of sulphuretted hydrogen. As a rule the distillation
is not continued to dryness, a tarry residue (" goudron ") being left ;
or asphaltum, if more oil be expelled. In some works this residue is
expelled from the retorts by compressed air, and in others is drawn off
or ladled out by suitable means.

In many of the works in Saxon Thuringia, the resins are used for
heating the stills and boilers as in Scotland and at Messel, for which
purpose they are burned in steam atomizing burners (Forsunka). The
heating value is about 8000 cal. The resulting sulphurous acid doe&
not seem to have any corrosive effect on the iron.

The soda tar is a thick black liquid. It is used for impregnating
Colliery timbers after the excess of caustic soda present has been neu-
tralized preferably by adding crude creosote in excess.

J See " Zeitschr. f. angew. Chemie," 1900, p. 1033. .

CHEMICAL TREATMENT OF TAR AND ITS DISTILLATES 95

One method of utilizing this soda tar is by using it in a diluted state
(4° to 5° B.) in place of caustic soda for purifying boiler-feed water.
A neutral oil which collects on the surface of the mixture during dilu-
tion must be removed. One hundred gallons of this aqueous liquor
are equivalent in effect to 22 to 25 Ib. of caustic soda. The steam
from the boiler water purified in this way smells slightly of creosote
and must not be used for chemical purposes.

Another method for utilizing this soda tar forms the subject of
Ger. Pat. 166,411, by the Warschen-Weissenfelser-Braunkohlen A.
G., Halle. The material, either in its crude state or after dilution
with water (1 : 5) is used for dissociating vegetable substances of all
kinds, such as straw and wood for paper-making, the resulting cellulose
being very flexible whilst exceedingly strong and tough. Whether this
process will make any great headway in the paper industry remains
to be seen.

The soda tar is decomposed by acids, crude creosote being deposited.
Either recovered acid or, preferably, carbonic acid is used for this pur-
pose, the last named being produced in the works by passing air over
gas coke or retort coke. Flue gases or retort gases may also be used,
Holand employing the gases from the retort stills, which gases are
thereby freed from carbon dioxide and sulphuretted hydrogen.

In the Scottish industry the acid resins are washed with hot water,
and the dilute acid thus recovered is used for the preparation of sulphate
of ammonia in the shale-distilling process. The precipitated resins are
mixed with the soda tar and are carefully separated from the resulting
sodium sulphate. As already mentioned, the purified resins and creo-
sote are burned in the Forsunka burners, for the purpose of heating
the stills and burners.

Recovering the Chemicals.

In spite of numerous attempts, no one has yet succeeded in re-
covering the spent chemicals from the tar-oil refining processes in
such condition that they are fit for use over again. On this account,
the waste products of the reactions are, as already mentioned, worked
up into by-products in order to reduce the outlay on chemicals.

A large number of patents1 have been taken out for processes
claiming either to recover the sulphuric acid from the acid resins or
to work up the waste acid to hydrochloric acid and nitric acid. None
of them, however, fulfils the requirements of practice, the recovered
acid being either too impure for technical use, or else the process is
too costly to work at a profit. For these reasons it is unnecessary to
go into these processes in detail.

The best way is to utilize the acid resins in the manner already
described, since, according to the experiments already performed

1 See Scheithauer, " Die Fabrication der Mineralole," pp. 149 et seq. ; Hein-
rici, " Zeitschr. f. angew. Chemie," 1898, p. 525 ; Wischin, ibid. 1900, p. 507 ; G.
Stolzenwald's Ger. Pat. 212,000 ; " Petroleum," Vol. IV, p. 1238 ; " Chem.-Ztg.
Rep.," 1910, 13.

96 SHALE OILS AND TAES

there seems no possibility of ever recovering pure sulphuric acid in
a profitable manner from the acid resins in question.

Caustic soda being more expensive than sulphuric acid, it becomes
correspondingly more important to recover the spent alkali or to manu-
facture a by-product of suitable value from the soda tar.

The spent alkali from refining the light oils, being capable of tak-
ing up more creosote, can be used in the preliminary alkali treatment.

The decomposition of the spent alkali has already been dealt with.
If carbonic acid be used for this purpose, the resulting sodium car-
bonate can be causticized, as is done in some works. The caustic
soda recovered in this way is of a brown colour due to organic ad-
mixtures, has the specific gravity T30 (30° B.) and can be advantage-
ously used in the preliminary stage of refining.

The spent alkali, after being separated from accompanying oil by
dilution with water, may also be distilled in the ordinary retorts, saw-
dust or tan bark being added to prevent frothing over. As a rule dis-
tillation is carried to dryness, creosote oil being obtained as distillate.
The residue is calcined in shaft furnaces to burn off the carbon, and the
crude sodium carbonate may be purified by redissolving and recrystal-
lization. This was practised by Krey, who placed ground soda crystals
on the market for a number of years. On the other hand the crude
salt can be lixiviated and then causticized with quick lime in the or-
dinary way.

CHAPTER VII.
THE MANUFACTURE OF PARAFFIN.

PARAFFIN, the most valuable constituent of the distillation tars, can be
recovered from same in a crystalline form, the separation from the ad-
herent oils being easier, and therefore the paraffin purer in proportion
as the crystals are more definite. In order to obtain this result, certain
rules must be followed. Either the tars or oils containing paraffin
must be distilled without the aid of steam, or else the amount of steam
admitted must be restricted as far as possible. Otherwise the paraffin
crystals will be small, difficult to purify, and will give a larger proportion
of loss than when the crystals are large and well defined. For the
same reason the vacuum must not be too feigh in the case of vacuum
distillation. The paraffin masses must be left at rest for complete
crystallization, since any disturbance of the crystallizing process retards
the deposition of the paraffin and the formation of crystals.

As may be gathered from the diagrams already given, the paraffin
is gradually extracted from the tar. Thus, in the Saxon-Thuringian
industry, hard paraffin alone is obtained from the first paraftin-bearing
distillate, the A-paraffin mass, the soft paraffin being obtained subse-
quently from the soft-paraffin masses furnished by the different follow-
ing distillations. Hence the hard-paraffin masses are allowed to
crystallize out at a higher temperature than the soft-paraffin masses.
This method of procedure furnishes a good, hard paraffin ; and' the
soft paraffins also are obtained in purer condition, being recrystallized
by the distillations needed for concentrating the paraffin solutions, and
therefore separating out in the desired form of large flakes on cooling.
Numerous experiments have been made during a long period, to.
try and obtain paraffin direct from distillation tars without distillation.
Eolle l patented a process with this object ; and Anschiitz 2 carried out
exhaustive experiments in the same direction at the Kopsen works.
In both cases the paraffin scale obtained was dark in colour and very
difficult to refine, so that this method had to be abandoned. Pauli 3
and Singer 4 took out patents for a similar method based on the well-

1 Schliephacke, " Zeitschr. f. die Paraffin-, Mineralol- und Braunkohlenteer-
Industrie," 1876, p. 34.

2 Grotowsky, " Jahresber. d. Technikervereins d. sachs.-thiir. Mineralolin-
dustrie," 1889.

3 Ger. Pat., 123,101. 4 Ger. Pat., 140,546.

(97) 7

98 SHALE OILS AND TARS

known insolubility of paraffin in alcohol, the resins, creosote, and oils
contained in the tar being soluble in that liquid. No experienced
practical man, however, would dream of even trying this method on a
manufacturing scale.

Greater probability of success is possessed by methods aiming at
the isolation of the paraffin from the paraffin masses — in which it is
present in a purer condition than in the tar — by other means than
cooling and crystallization. Although all endeavours of this kind have
proved unsuccessful hitherto, it is not impossible that a method may
ultimately be found that will enable the solid hydrocarbons to be
separated, on a technical scale, frjom the liquid members in the joint
solution. Wagemann l proposed to throw down the paraffin from
solution in oil by means of certain gases. Krey and his pupils de-
monstrated, by c ireful experiments, the impracticability of separating
paraffin from oils by dialysis.

Gases have been separated from mixtures by the aid of centrifugal
force,'2 and though no successful results have yet been obtained in the
case of liquids, there is, nevertheless, a possibility of being able, by this
means, to separate a mixture of bodies which are in the same condition
of aggregation, but differing in density and other properties.

We will now proceed to describe the methods in current use for re-
covering paraffin from distillation tars.

A. THE MANUFACTURE OF PARAFFIN IN THE SAXON -THURINGIAN

INDUSTRY.

The Crystallization Process.

Vessels of different dimensions and differently arranged crystalliz-
ing plants are used for the crystallization of the paraffin masses in the
various works. The larger the tank the longer the time required for
cooling down the mass in order to give complete separation of the
paraffin crystals.

The A- (hard-) paraffin mass is generally placed to crystallize in
small vessels holding about 6^ to 11 gal. In some works these vessels
taper towards the bottom, whilst in others they are prismatic ; and
some works again use larger vessels holding up to 22 gal. Water
is chiefly used for cooling the smaller vessels, but those of larger size
are exclusively cooled by air. As a rule, the small vessels are placed
in compartments in a cooling cellar where they are surrounded by
well-water. If the works are connected with a mine, pit water is
used ; otherwise the requisite cooling water is raised by a pumping
plant, which also supplies the condensers of the distillation plant.
The large vessels are set up in cool, well-ventilated rooms.

After distillation or chemical refining, the paraffin mass, at a tem-
perature of 50° to 70° C., is delivered through pipes to the crystallizing
vessels, into which it is fed by suitable devices which , ensure rapid

1 Dingler's " Polytechn. Journ.," 139, p. 303.
2" Journ. f. Gasbel.," 1904, p. 943.

THE MANUFACTUBE OF PARAFFIN 99

working and protect the operatives from being inconvenienced by the
vapours. Air cooling is also applied in the first stage of cooling the
small vessels, in order to favour the development of the crystals by a
gradual reduction in the temperature. The next stage is to admit to
the compartment water that has already been used for cooling in
other compartments and has therefore become warmer, this in turn
being replaced by cold water. In the large, air-cooled vessels, where,
the cooling proceeds slowly, the position of the crystals is complete in
ten to fifteen days, and the mass is " ripe " for further treatment. In
the small vessels, the A-paraffin mass takes only four to six days to
•crystallize out. The above figures vary, within narrow limits, accord-
ing to the time of year, being rather less in winter and more in
summer. It is bad policy to cool the hard-paraffin mass too far,
because at this stage the hard-paraffin scale alone is desired, the soft
scale being left uncrystallized. As a rule the mass is worked at a
temperature of 15° to 18° C.

The soft-paraffin masses are either crystallized in large vessels,
holding 550 to 1100 gal., by the natural cold of the winter season,,
•or else are cooled down in the same small vessels as used for the
hard-paraffin mass, by the aid of refrigerating machinery.

In the former case, the soft-paraffin masses are accumulated in the
crystallization tanks during the warmer months of the year ; during
the colder season a gradual crystallization of the paraffin scale takes
place; and in the winter the mass is subjected to further treatment.
The oil obtained in this way is regarded as technically free from par-
affin, and indeed contains such a small proportion of paraffin— which
moreover is of the consistence of ointment — that the recovery of the
latter would be unprofitable. The conditions essential to successful
working are : sufficient storage accommodation for the paraffin masses,
and the provision of crystallization sheds that are fully exposed to the
winter cold in all parts. The crystallization tanks must be large
enough to hold quantities equal to about one-third of the total amount
of tar treated during the year ; and the buildings in which these tanks
are housed must be of slight construction with lowered walls so that
the cold wind can be admitted and warm air excluded, according to
requirements.

When refrigerating machinery is used, the cooling liquid generally
consists of brine reduced to a low temperature, the soft-paraffin
masses being treated continuously, as soon as produced.

Ammonia absorption machines were formerly employed for the
production of artificial cold, but the ammonia compression machine
is now generally used as being of higher efficiency, and enabling the
paraffin masses to be delivered to the filter press at temperatures
of - 10° C. and under. The possibility of producing much lower tem-
peratures than could previously be attained has simplified matters con-
siderably, since on the one hand far more dilute solutions of paraffin
in oil can be crystallized, and on the other the resulting oil is so
•completely freed from paraffin that, except in the hot summer months,

100 SHALE OILS AND TABS

it can be sent out at once. These two circumstances have also short-
ened the distillation processes. In some works, the artificial refri-
geration system has enabled the winter crystallization process to be
entirely dispensed with for some years past. <

In the ordinary process in small vessels, the soft; mass is cooled
with water for several days and then reduced to crystallization tem-
perature by means of very cold brine.

In some works the process is carried on with vessels of a different
character. Wernecke (Ger. Pat. 92,241) allows the paraffin mass to
solidify in cooling cells built into a cooling tank, the cooling agent con-
sisting of brine cooled in a refrigerating machine. When the mass has
set firm, it is ejected from the cells by pneumatic pressure into a con-
veyor device which transports the paraffin cakes for further treatment
in the filter press as usual. The cost of repairs and the labour bill will
determine the utility of this system.

It is impossible to decide generally whether the winter crystalli-
zation or refrigerating machine method is the best for treating soft-
paraffin masses, so much depending on a number of factors. Points to
be considered are : the quantity of tar to be treated, the extent of the
existing plant for winter crystallization, and the destination of the
finished soft-paraffin scale. In the case of larger works in which the
bulk of the soft paraffin is worked up, on the premises, into composite
candles, the refrigerating-machine method is undoubtedly indicated.
Works of medium size, treating about 5000 to 6000 tons of tar per
annum, equipped with an extensive plant for winter crystallization and
obliged to turn out the finished soft paraffin in good condition for sale,
are able to work satisfactorily with the winter crystallization method.

For reasons previously given it is an erroneous practice to use the
refrigerating plant for hard-paraffin masses, by adding ice to the cool-
ing water in order to obtain a very low temperature.

The Pressing Process.

The work is divided into three stages, viz. pressing in the filter
press, in the vertical hydraulic press, and in the horizontal hydraulic
press.

The cooled and crystallized A-paraffin mass is ejected or removed
from the crystallization vessels by suitable means, and fed to the filter
press.

In the case of the soft-paraffin masses, when the winter crystalliza-
tion method is practised, the bulk of the oil from some of these masses
is left in the bottom of the crystallization vessels, and a portion of the
paraffin is thus recovered in a crude form without needing to be filtered.
Other masses of this class are more difficult to treat, the mass being
pumped or ladled out of the vessels and conveyed in tubs on a rail
or overhead runway.

The paraffin masses are first crushed in a mechanical crusher (Fig.
51), the mass tipped into the hopper A being crushed by the rotary
arms B and dropped into the collector C, from which receptacle the

THE MANUFACTURE'. OF V

101

pulpy mass is drawn by a pump and delivered to the filter press, where
the crystals of paraffin are separated from the oil.

At the present time, filter presses l alone are used for this opera-
tion, though formerly centrifugal separators, like those in the sugar
industry, or aspirators, were employed. Centrifuges are only suitable
for masses in which the crystals are large ; and aspirators cannot com-
pete with filter presses for work on a large scale.

It is worthy of note that the appliances for treating the paraffin
masses were mostly derived from the sugar industry which flourished
in the Province of Saxony contemporaneously with the mineral oil in-
dustry ; and even now, many upright presses originating from the sugar
industry are still in use.

Attempts made to treat the strongly cooled paraffin mass direct in
the hydraulic press without previously being put through the filter

FIG. 51. — Mechanical
crusher.

FIG. 52. — Filter press.

press had to be abandoned on account of the great waste incurred';
and this method is unsuitable owing to the relatively low paraffin con-
tent of the masses.

The construction of the filter press is explained by Fig 52. The
press is built entirely of iron, the frame A supporting the fixed head
B, which is connected with the frame C (mounted on two uprights) by
means of a couple of iron rods e. These rods ^

act as guides for the movable press head D and
the filter plates EE, which rest on the rods
by means of lugs and are removable. Fig. 53
illustrates a filter plate, of which fifteen to twenty
are inserted in the press. By means of a crank
wheel and screw spindle S the filter plates are
presssd together between the heads. In the centre
of the filter plates, the edges of which make a series of perfectly tight
joints, is an orifice F about 2 in. wide, so that these orifices, in conjunc-
tion with that in the fixed head, form a passage into which the paraffin

1 Eisenlohr and Busch, " Filterpressen " (" Filter Presses "), " Zeitschr. f.
angew. Chemie," 1907, pp. 1393 et seq.

FIG. 53.-Filter

102

OILS AND TABS

mass from the crusher is forced by the pump. The plates are recessed
internally about three-fifths of an inch on each side, and a piece of per-
forated sheet metal is screwed over each recess. Each filter plate is also
^provided with a delivery channel, adapted to be closed by a tap G.
Over each filter plate is stretched a canvas filter cloth, secured externally
so as to be easily detachable ; and when worn out can be replaced by
a new one without interrupting the work for more than a short time.
When the plates have been pressed up together, the filter press can
be started. The paraffin pulp is pumped into the channel formed by
the apertures F. The oil, forced through the press cloths, runs into
the delivery channels of the plates, and through the opened taps G into
the gutter H, whilst the paraffin scale is retained between the filter
cloths on adjacent plates and fills up the hollow spaces formed by the
recesses. The oil in the gutter H is drawn off further. The pump
feeds each filter press until the latter is full, whereupon the feed is
stopped by the valve V and the mass diverted to another filter pressr
two or three of which are usually connected with a common feed main.
This main is provided with a safety valve, set to lift at a pressure of 2 to
3 atmospheres and thus indicating when a filter press is full. The filled
press is emptied by releasing the screw spindle S and separating the
plates, the paraffin cakes being scraped from the cloths with wooden
knives. A filter press will furnish about 1^ cwt. of scale at each
filling.

The press cakes, still contain about 26 to 30 per cent of oil, and are
transferred, for the removal of this oil, to the vertical hydraulic press,
where they are subjected to a pressure of 100 to 150 atmospheres.
Fig. 54 shows a vertical press, about 6| ft. high. -The upper press
head A is supported by four columns ; and the
plunger, carrying an iron plate C, is guided by the
lower press head B. The paraffin scale is packed
in press cloths, 32 to 38 in. square, preferably
made of wool on the inner side and flax on the
outside. A charge of scale from one filter press
will fill about ten such cloths, which are folded over
to a square of 15 to 22 in. and superimposed on
the plate C., each being covered by a slightly
warmed plate of sheet iron. When the press is
filled, the water is turned on and raises the plate
and its load (guided by the four corner pillars),
pressing the same against the upper head. The
FIG. 54.— Vertical pressure is gradually increased, and the cakes are
hydraulic press. allowed to remain under full pressure for a short
time. The oil is forced out, runs away and is united with the runnings
from the filter press.

The 1£ cwt. of scale from the filter press will furnish about 120 Ib,
of crude paraffin.

The several kinds of paraffin mass yield the following weights of
crude paraffin : —

THE MANUFACTURE OF PARAFFIN 103

A-paraffin mass 15-20 per cent, melting-point 50-55° C.

B- „ „ 10-15 „ „ 40-45° C.

C- „ „ 10-15 „ „ 38-42° C.

Solar- „ „ 15-20 „ „ 35-40° C.

The oils running from the filter presses and vertical hydraulic press
are united, and are worked up in the manner indicated in Diagrams I
and II.

In the earlier years many attempts were made at refining the crude
paraffin, by treating it with sulphuric acid in the manner employed for
refining ozokerite, whilst other chemicals, such as chlorine and sodium
sulphide, were also tried. All these methods, however, were displaced
by the mechanical process of washing the paraffin with light lignite-tar
oils. Even the attempts made to introduce the sweating process for
this paraffin proved unsuccessful, though it answers admirably in the
Scottish shale industry (as will be described later) where it is the sole

FIG. 55. — Horizontal hydraulic press.

method now in use. With lignite-tar paraffin, on the other hand, the
final product is always dark in colour, owing to the presence of high-
molecular hydrocarbons. The Scottish paraffin differs essentially in
structure (fibre-crystal line) from that of the Saxon-Thuringian in-
dustry, and it is probably to this circumstance that their divergent
behaviour under the sweating process is to be attributed.

The paraffin scale from the vertical press still contains 10 to 15 per
cent of oil, which cannot be got rid of by pressure. For this reason,
as already mentioned, the scale is washed by melting it by direct
steam heat, in a vessel containing 10 to 12 per cent of benzine (light
lignite-tar oil) of specific gravity 0*780 to 0-815, the two being mixed
together and poured into water, whereupon the paraffin solidifies to a
perfectly uniform mass. The layer of paraffin, about 1 in. thick, is
cut into cakes and pressed in the horizontal hydraulic press, a lateral
elevation of which is shown in Fig. 55. In build and method of

104 SHALE OILS AND TABS

operation this press is similar to the upright one. The press head S
moves between four iron rails A A, on the upper pair of which the
press cloths are suspended by means of iron rods. These cloths are
closed at the bottom only, and an iron plate of equal size is interposed
between each pair. According to size, the presses will hold 30 to 60
press cloths. As in the vertical press, the pressure is produced by a
hydraulic pumping plant and attains 200 to 250 atmospheres. By
opening the valve V, the press head and charge are forced against the
fixed head B, and the charge is left under maximum pressure for a
short time, thus forcing out the contained oil, which collects in a
gutter underneath the press and is led away. The oil is known as
hard or soft oil, according to the class of paraffin.

To empty the press, the exhaust valve Vo is opened, the plunger S
being drawn back by the weight P into its original position. In some
works the pressure is supplied by an accumulator with a constant
working pressure of 25 atmospheres and connected with the press
by means of the valve V. The accumulator is of the same type
as those used in cement works.

In order to prevent the bursting of the cylinder casting C by ex-
cessive pressure, safety valves are attached to the hydraulic pumping
plant; and in^some works special safety appliances for the same
purpose are arranged in the pressure pipe.1

When the scale is pressed in the horizontal press, the light lignite-
tar oil carries away with it the heavy oil adhering to the scale. This
press oil, which is very rich in paraffin, runs" down into a gutter
under the press. The scale from the first pressing is remelted, mixed
with benzine in the same manner as the crude paraffin, cooled over
water and pressed again. If a first-class commercial article is de-
sired, the paraffin from the second pressing is pressed a third time ;
but, as a rule, only two pressings are given. At each successive
melting of the paraffin, benzine of lower specific gravity is used, so
that, finally, the lightest grade of all is employed. Occasionally, the oil
draining from the second and third pressings in the horizontal press
is used, in place of benzine, for dissolving the paraffin scale.

In most works the presses are run both summer and winter with-
out being warmed, and it is only seldom that heat is applied by means
of steam pipes arranged near the presses. It is not the practice to
use proper warm presses, such as are employed for pressing stearine,
anthracene, etc.

The process of washing with benzine is attended with the drawback
that, in many cases and especially with solt paraffin, a faint smell of
the washing agent remains, in spite of careful after-treatment (blowing).
Nevertheless, all attempts made to replace benzine by some other
washing agent have failed up to the present. Olein, amyl alcohol, and
other alcohols, and also carbon disulphide have all been tried ; but the
high price formed a deterrent on the one hand, and on the other their

< l Scheithauer, " Die Fabrication der Mineralole," pp. 164 et seg.

THE MANUFACTURE OF PARAFFIN

105

application was found to be impracticable on a manufacturing scale.
Amyl alcohol is put out of court by its smell, which produces head-
ache ; and carbon disulphide by its high fire risk. Further attempts
were made to discover a washing agent capable of reacting chemically ;
and the pyridin bases used in refining anthracene are found suitable
for this purpose, furnishing a beautifully white paraffin, which is
rendered perfectly inodorous by treatment with sulphuric acid of specific

FIG. 56. — Longitudinal section of press plant.

gravity 1*26,, this treatment readily eliminating the bases left behind in
pressing. Unfortunately, the penetrating and disagreeable smell of
the reagent precludes the application of this method in practice, though
there would be no objection on the score ^>f cost.

The experiments made to destroy the colour of semi-refined paraffiri
by chemical bleaching also proved a failure, the reagents used having
either an injurious influence (ozone, chlorine) or being quite inert (sul-
phurous acid).

FIG. 57. — Cross section of press plant.

The Press Plant.

The press plant of the Webau works, Weissenfels (A. Riebecksche
Montanwerke), is shown as a longitudinal section, cross section, and
plan respectively in Figs. 56, 57, and 58. A A are the filter presses,
B B the upright and C C the horizontal presses. The oil draining
from A and B is collected into a pressure tank D, whence it is conveyed
further by steam. The crude paraffin is melted in the other vessels E
and mixed with benzine. These vessels are connected with the con-
denser J in which the benzine that is vaporized in E is condensed.
The benzine is stored in the iron tank F. The coolers K K, which

106

SHALE OILS AND TABS

are set in cement, are charged with water on to which the paraffin is
poured out of E. The press oil collects in the pressure tank G, from
which it is ejected by steam for further treatment. The finished
paraffin is melted in the vessels E'E' and run off into the pressure
tanks G'G".

The outlay for press cloths of various kinds is a not unimportant
item of expense in the manufacture of paraffin, and amounts to about
4^d. per cwt. of the finished article.

The Steam Jet Treatment.

The process of purification by pressing frees the paraffin from oils
and makes it white in colour. Nevertheless it still contains in solution
small traces, about 0'2 to 0'5 per cent, of the benzine used for washing,
which cannot be got rid of by pressing, and imparts its own Character-

FIG. 58. — Plan of press plant.

istic smell to the paraffin. These traces of benzine are eliminated by
treating the paraffin with a jet of steam.

For this purpose the paraffin is placed in vessels, which differ in
various works, being retorts in some cases and cylindrical vessels in
others. Here the paraffin is warmed by steam, and is subjected to the
action of a jet of steam admitted at the bottom of the vessel. This
steam carries away with it the traces of benzine vapours, which also
contain a certain amount of paraffin and are preferably condensed in a
suitable apparatus, the condensed product being returned to the manu-
facturing process. In some works the whole operation is carried on in
a partial vacuum produced by a Koerting aspirator. The steam- jet treat-
ment is continued for thirty to forty-eight hours, within which period
hard paraffin can be rendered perfectly inodorous, though this condi-
tion is more difficult to attain in the case of soft paraffin. In the heat-
ing process preceding the a 1 mission of the steam jet, the paraffin must

THE MANUFACTUEE OF PAEAFFIN 107

be raised to a temperature that precludes condensation of the steam.
During the steam -jet treatment itself the temperature must not exceed
140° C. but must be kept between 130° and 140°, since otherwise the
paraffin would suffer decomposition. It is therefore inadvisable to
employ strongly superheated steam, or steam at a pressure exceeding;
4 atmospheres.

Decolorizing the Paraffin.

After the paraffin has been rendered inodorous by steaming, its
colour is still of a faint greenish-yellow tinge, not pure white, and must
be rectified by treatment with decolorizing agents. For this purpose
animal charcoal was formerly used, but nowadays ferrocyanide residues-
and similar preparations are applied with success. In some works the
decoloration was occasionally effected with clay,1 but this has been
abandoned. Quite a number of bleaching agents have been and are
still recommended ; but each manufacturer must ascertain by experi-
ment the agent which will give the best results. Experience indicates
that the decoloration of paraffin is best effected by a mixture of pure
carbon and silicates. The process is a purely mechanical one, and is
based on surface attraction.

The decolorizing powder must be thoroughly dried at a temperature
of 100° to 110° C. previous to use, in order to make it perfectly anhy-
drous. This operation is carried on in ottens of various kinds, derived
from other industries.

The decolorizing process entails the consumption of 1 to 2 per cent
of the dry powder, there being, as a rule, no advantage in using any
larger quantity. In some instances it is found preferable to divide the
powder and perform the operation in two stages. When the powder
has been added to the melted paraffin, the two must be intimately
mixed together by means of mechanical or hand-operated stirrers, in a-
vessel heated to 70° or 80° C. by steam. For many reasons it is inadvis-
able to use air as the mixing agent. The mixing is continued for about
half an hour, whereupon the mixture is allowed to rest, the decolorizing
agent settling down to the bottom. The paraffin is then separated
from the adjunct by filtering through paper. At one time very simple
appliances were used for this purpose, but most works now employ
filter presses, similar to those already described for paraffin scale, and
kept warm by the aid of steam.

The spent powder contains large quantities of paraffin, which must
be recovered. This is done by extracting it with benzine in apparatus
which differ in almost every works. There does not seem arty neces-
sity for describing them in detail here.2 They accomplish the desired
object, the powder issuing perfectly free from paraffin. The once-used
decolorizing powder is weakened to such an extent that it cannot be
employed even a second time, nor can it be regenerated by calcination.

1 Vehrigs, " Dingier," 270, p. 182.

51 See also " Zeitschr. f. angew. Chemie," 1899; Allen & Holde's Ger. Pat.
106,119.

108 SHALE OILS AND TABS

B. MANUFACTURE OF PARAFFIN IN THE MESSEL INDUSTRY.

Crystallization.

The paraffin mass is cooled and brought to crystallize in two stages.

Stage 1. The plant used for this purpose occupies only one- tenth
the space required in the Saxon-Thuringian industry. The cylindrical
cooling vessels are provided with automatic charging and discharging
devices. To keep the vessels clean and accelerate cooling, a number
of scrapers are caused to move vertically over the cooling walls. These
scrapers do not stir up the mass at all, but merely allow the detached
scrapings to slip down slowly to the centre of the vessel. The oils con-
tained in the paraffin are not thin like those in the Saxon-Thuringian in-
dustry, but viscous ; and even quiescent cooling does not give the same
large crystals as those obtained in that industry. This drawback has
been taken into consideration at Messel and counteracted in the sub-
sequent treatment of the paraffin scale. The first cooling is effected
successively with air and cooling water, down to a temperature of
about 15° C., at which temperature the mass is filtered for the recovery
of hard scale.

Stage 2. The filtrate is subjected to a second cooling, in cold
chambers, large jacketed cooling tanks being employed. The jacket
spaces are traversed by cold brine from a refrigerating plant. The
tanks are filled with the filtrate from stage 1, and the walls are scraped
clean by rotary horizontal scrappers working at a very slow speed, which
again do not stir up the mass at all. The buttery cooled mass is de-
livered in a continuous strand towards the centre by the scrapers, and
contributes to the solidification of the mass there. At the same time
the more fusible paraffin is redissolved, the crystals of the harder scale
continuing to grow. As soon as the temperature has fallen to - 3° C.
throughout the tank, the mass — which does not require any breaking up
— is transferred to filter-presses in the same chamber. By this means
the temperature of the filtrate is kept down to - 1° C., so that it carries
away only very small traces of paraffin.

The Pressing Process.

The filter cakes obtained in both cooling stages are freed from the
slight residual traces of contained oil in vertical hydraulic presses, and
removed for further treatment. The hard scale from the first stage
melts at about 54° to 57° C., and the soft scale from the second stage
at 46° to 48° C.

The further treatment of Messel scale is effected in two ways. In
the one method a doubly refined product is obtained by remelting with
benzine (photogen) and subsequent pressing, as in the Thuringian in-
dustry, whilst the other treatment, by sweating, furnishes a product
corresponding to semi-refined American paraffin. The sc>vle intended
for double refining is treated in advance with small quantities of acid
and alkali, then distilled in vacuo with a current of steam, further re-
fined by romelting, and finally decolorized, the colourless paraffin being

THE MANUFACTURE OF PARAFFIN 109

moulded into cakes. Candlemaking is not practised at Messel. The
sweating process is similar to that adopted in other places and need
not be more fully described.

C. PARAFFIN MANUFACTURE IN THE SCOTTISH INDUSTRY.

Cry 8 tallization .

The crystallization process is the same as in the Saxon-Thuringian
industry. The hard-paraffin mass is cooled by air in shallow vessels,
and the soft masses are cooled with brine reduced to a low tem-
perature in a refrigerating machine. At one time small apparatus,1
in which the operation was effected quickly, were used for crystallizing
the soft paraffin. The usual practice was to dip a drum into the
cooled mass, and scrape off the paraffin pulp setting on the surface of
the drum. At present, appliances are used which obviate the draw-
backs of the old method and enable the crystals to develop better, the
cooling being more gradual. This paraffin pulp is more easily filtered
than if interspersed with small undeveloped crystals.

Henderson's cooling apparatus 2 consists of a jacketed vessel, di-
vided into small compartments by partitions, each of which forms a
jacket and, like the main jacket, is traversed by a cool solution of cal-
cium chloride. The paraffin crystals attach themselves to the parti-
tions, from which they are removed by slowly revolving scrapers.
New crystals are continually deposited and scraped off, and the pulp
collects at the bottom, falling into a channel from which it is moved by
a worm conveyer into a pipe connected with a pump, which forces the
pulp into the filter press. Large quantities of paraffin mass can be
cooled down in such a vessel ; but as the mass is not left at rest to crys-
tallize, except for a short time, the crystals are not so well developed as
in the Beilby cooling apparatus. In this latter the soft-paraffin mass is
cooled slowly in a series of rectangular cells by the aid of a refrigerat-
ing machine for four days, whereby large crystals are formed. The
cooled mass is led away at the bottom of the apparatus and delivered
to the filter press.

In some paraffin works the paraffin mass is led through pipes
which are strongly cooled by the direct evaporation of ammonia in the
cooler. The rapid cooling, however, causes the paraffin to deposit in
imperfectly formed crystals, which are difficult to separate from the oil.

The filter presses are generally larger than those used in the
Saxon-Thuringian industry, but accomplish the same purpose.

The Sweating Process.

The scale from the filter presses is packed in linen cloths and
treated in hydraulic presses, crude paraffin being obtained. In some
works the scale obtained from the press is refined direct. At one time
the refining of the crude paraffin was performed in the same manner

1 Scheithauer, " Die Fabrication der Mineralole," pp. 176 et seq.

2 " Chemical Technology," 2 (" Lighting "), pp. 135 et seq.

110 SHALE OILS AND TABS

as in the Saxon-Thuringian industry, being melted, repeatedly mixed
with shale benzine, and pressed, this treatment being followed by
•steaming and bleaching. This treatment", however, has for some
years now been abandoned in almost all cases, being replaced by the
sweating process, which in turn has been successively modified and
Improved. A few of the most widely extended methods will now be
described in order of time, leaving out of consideration such imperfect
experimental methods as were only used temporarily.

The crude paraffin, a mixture of hard and soft scale, is melted and
allowed to set in the form of cakes. These cakes are transferred to
the sweating house, where they are laid on stretched cloths. The
temperature of the room is maintained, by the aid of steam heating
apparatus, at a constant level, 3° C. below the melting-point of the
•crude paraffin. The brownish-red oil, accompanied by the paraffin of
low melting-point, drains out of the cakes into a gutter underneath the
band of cloth, and is returned to the manufacturing process. The
sweating process usually takes three to five days,1 and is repeated, but
only rarely more than once. The residual paraffin is in a refined con-
dition, being free from the oily and odorous constituents, and is de-
colorized by treatment with decolorizing powder.

Tervet and Allison's sweating process requires a cooling house and
a sweating house, each of which is divided into three sections, so that
three grades of paraffin can be treated at the same time. Each section
•of the cooling house holds twenty enamelled cast-iron pans traversed
by a light canvas belt. The pans are filled with melted paraffin, which
solidifies gradually. A number of racks carrying corrugated steel
trays, corresponding in number and size with the cooling pans, are
arranged in the sweating house, which is maintained at the desired
temperature by steam heating apparatus. After being cooled down in
the cooling house, the paraffin in the form of cakes is transferred on
the canvas belt, which is operated by a hand winch, to the sweating
house. Here it breaks to pieces in passing over the corrugated trays,
and the oil and paraffin of low melting-point drain away into a gutter,
whilst the residual paraffin is removed, by mechanical means, to a
melting vessel outside the sweating house.

Another sweating process, simpler than those already described,
was devised by M. Henderson.2 The sweating house, which is 56 ft.
long, 16-£ ft. wide, and 10 ft. high, is fitted with iron stands supporting
troughs which are provided with double bottoms, the upper one being
formed of fine-mesh wire gauze. These troughs, which are 23 ft. long
and 6 in. deep, are filled with sufficient cold water to cover the false
bottom, on to which the paraffin (previously melted outside the room)
is run until the troughs are quite full. The wide doors of the room
are thrown open, and fans are set running. When the paraffin has
solidified, the water is drained off, and the paraffin cakes rest on the

1 A full description of the Pyhala sweating process is given in " Petroleum,"
4, p. 1393, and " Braunkohle," 8, p. 421.
2 " Oil Shales of the Lothians," p. 179.

THE MANUFACTUEE OF PABAFFIN

111

gauze. The room is converted into a sweating house by closing it
tightly and starting the steam-heating apparatus.; whereupon the
paraffin sweats, the drainings running away through the gauze to the
bottom of the troughs, and being carried away. When the sweating

FIG. 59. — Sweating apparatus.

is completed and the drainings are removed, the temperature of the
room is heightened, so that the refined paraffin also can be melted and
removed in the liquid condition. If insufficiently refined by this first
treatment, the paraffin is put through the sweating process again.

The newest sweating apparatus patented by M. Henderson is il-
lustrated in Fig. 59. Instead of troughs, the paraffin is placed in deep

112 SHALE OILS AND TABS

upright cells A of circular section and containing a wire-gauze
covered cylinder b. The bottom a of each cell is also of wire gauze.
The inner gauze cylinder is intended to act like a wick and facilitate
the draining away of the oil during the sweating process, which is
conducted in the manner already described. B (Fig. 59) represents a
longitudinal section of the sweating cells, and C shows their internal
arrangement. The cells are filled by a pipe c, and emptied through d.
Heating pipes are shown at e.

According to the report of the Broxburn management, this appara-
tus is of much higher capacity than the older type, the paraffin solidi-
fying much quicker and the sweating process taking less time.

Originally, the melted paraffin was intended to be cooled in the
cells by means of air alone, but the scope of the Patent was subse-
quently extended by suspending the cells in a vessel of water, and
thus cooling them.1

In spite of repeated sweatings, the resulting paraffin is sometimes
yellow in colour and cannot be whitened by this means.

The drainings, a mixture of oil and soft paraffin, are usually
sweated (of course at a lower temperature) for the recovery of the soft
paraffin.

Decolorizing the Paraffin.

After the sweating process the paraffin (all grades) is treated with
decolorizing powder in the same manner as in the Saxon-Thuringian
industry. Various types of filter are used for the mixture of paraffin
and powder, that of Young, for instance, consisting of a stea in -jack-
eted vessel containing a wire gauze cylinder faced with flannel and
filter paper.

1 So far as the author is aware, the wet sweating process now used in several
paraffin works in Galicia, is not employed in Scotland. In this process the
cooling water remains in the cells during the sweating process. The cells having
porous walls, the sweated oil collects on the water (which flows continuously)
and is removed with same and separated therefrom. Reference may also be
made to the Wiesner combined pressing and sweating process used at Mahr-
Schonberg (" Petroleum," 5, p. 636.)

IPI CHAPTER VIII.

PRODUCTS FUBNISHED BY SHALE OIL AND LIGNITE TAB.

A. PRODUCTS OBTAINED IN THE SAXON-THUBINGIAN INDUSTEY.
Quantitative Yield.

THE lignite tar now treated gives the following average yield of pro-
ducts : —

Light lignite tar oil (bei
Solar oil . . . ' " "-.»
Pale vaseline oil .
Gas oil .

izine

)

• 2—3 per
2- 3
10—12
30-35
10—15
8—12
3— 6
4— 6
20—25

cent.

». :

f '

Heavy vaseline oil
Hard paraffin ; %. : - ,
Soft paraffin .
By-products . .
Water, gas, and loss

The Oils.

The oils, rendered marketable by distillation and refining, are run
into open iron tanks holding 10 to 30 tons, where they are left to settle,
in order that any residual water may separate out and the oils may be-
come clear and transparent, free from any turbidity. The tanks for
the heavy oils are fitted with a heating device consisting of coiled or
gilled pipes, laid in the bottom of the tank and heated by steam. A
steam trap is provided in each case.

When the demand for oils fails to keep pace with the production^
considerable stocks of some grades are occasionally accumulated, and
for this reason each works must be equipped with ample storage ac-
commodation. At one time, rammed concrete or bricked pits faced
with cement were used for this purpose, but are now seldom employed,
iron vessels being the rule. The dimensions vary considerably,1 but
the shape is generally cylindrical. Unless embedded in a bricked pit,,
the tank is mounted on a foundation consisting either of brickwork or
sand, covered with a layer of asphalt. In addition to cylindrical tanks,,
several constructed in accordance with Intze's Patent 2 (Fig. 60) have
been erected by the A. Eiebecksche Montanwerke. The top and bottom
sections of this tank are conical, and the centre is traversed by a cylin-

1 Probably the largest tank of this kind is that at the Beussen works of the
A. Biebecksche Montanwerke, its capacity being 770,000 gal.
2Ger. Pat. 24,951, " Journ. f. Gasbel.," 1884, p. 705.

(113) 8

114

SHALE OILS AND TABS

drical shaft a fitted with a ladder. The whole is mounted on an
annular foundation, thus leaving the bottom visible ; and the space
underneath the tank bottom can also be utilized. One advantage of
this type of construction is the relative cheapness and compactness of
the annular foundation, another being that the entire surface is open
to inspection so that leaks can be readily detected.

The oil is racked into casks either direct from the large storage tanks
or from the small iron tank ; but of late years, tank cars have grown

FIG. 60. — Cylindrical tank — Intze patent.

in favour in place of casks, so that now only about 20 to 25 per cent
of the oil sold by the Halle Syndicate is sent out in the latter.
« The casks consist of American barrels that have already been used
for the conveyance of petroleum. Before being filled, the barrels are
thoroughly cleaned out by swilling and steaming ; and in some works
they are also relined with glue. They are, however, getting scarce,
and sell at high prices when in good condition, the reason for the
scarcity being that the American oil companies now send out very few
casks, most of the oil being exported in tank steamers.

PRODUCTS FURNISHED BY SHALE OIL AND LIGNITE TAR 115

Glass carboys holding about 11 gal. are no longer used, as for-
merly, for the conveyance of the oils.

Particulars will now be given of the properties and uses of the oils
produced.

The light lignite-tar oil, or benzine, has the specific gravity 0*780
to 0*810, contains traces of creosote and flashes at 25° to 30° C. or
higher. Analysis by distillation yields 20 per cent of fractions boiling
between 120° and 150° C. (boiling commences at 100° to 120° C.), 80 to
100 per cent of the oil distilling over up to 200° C. ; colour, water-
white with blue fluorescence. This oil is consumed on the premises
for refining paraffin, but at one time it was sold as a lamp oil under
the name " Photogen ".

Solar oil has the specific gravity 0*825 to 0*830. It is usually free
from creosote, and flashes at 45° to 50° C. Colour same as that of the
benzine, but with a slight tinge of yellow. Analysis by distillation :
•commencement of ebullition 150° to 170° C. ; fractions up to 200° C.,
40 to 50 per cent ; up to 250° C., 80 to 90' per cent, the remainder
boiling up to 250° to 270° C. Viscosity (Engler) 1*05 to 1*10. This oil
was formerly used solely in lamps, but now replaces petroleum as
motor oil. The high flashing-point is worthy of being borne in mind
.as affording increased security against fire during storage.

When used as lamp oil, solar oil needs ^a different class of burner
to that for ordinary petroleum, since, on account of its higher percen-
tage of carbon, it requires an abundant supply of air to keep the flame
.from smoking.1 Its good illuminating properties have been demon-
strated analytically by Grotowsky and others.2

The production of solar oil is small in comparison to what it was
in the earlier days of the industry ; but the output finds a market for
the purposes stated.

Solar oil can also be used for other purposes instead of petroleum.
It makes very good lampblack, and is employed to kill the "fly"
infesting grape vines.

Pale vaseline oil is a generic term applied to the commercial varie-
ties known as : yellow oil, red oil, and cleaning oil. The specific gravity
of cleaning oil is 0*848 to 0*850, that of yellow oil being 0*860 to 0*870 and
that of red oil 0*870 to 0*880, the colour being pale yellow, straw yellow,
and red respectively. Creosote content 0*1 to 1 per cent. According to
the analysis by distillation, these oils contain little or no constituents
boiling under 200° C., the red oil in particular. The commencement of
ebullition is generally at 200° to 210° C., 20 to 70 per cent passing over up
to 250° and 90 to 100 per cent below 300° C. The viscosity, as de-
termined in the Engler viscosimeter for lubricating oils, varies between
1-2 and 1*5, and the flashing-point is between 90° and 110° C. These
oils solidify at - 10° to - 15° C., and — the red oil in particular — contain
small quantities (^ to J per cent) of irrecoverable paraffin in solution.
In contrast to solar oil, they are free from naphthalene.

1 Scheithauer, «* Die Fabrikation der Mineralole," p. 186.

2 " Zeitschr. f . Berg.-Hiitten-u. Salinenwesen," 24.

116 SHALE OILS AND TABS

As its name implies, cleaning oil is used for cleaning ; it is also
occasionally employed as a solvent in extraction processes, but rarely as
gas oil. The heavier, yellow, and red oils find application in the pre-
paration of better quality wagon greases, and sometimes for mixing
with petroleum lubricating oils ; their chief use, however, being in the
production of oil gas. They have also found employment, to a limited
extent, for denaturing rock salt instead of petroleum.

The dark vaseline oil, or gas oil has the specific gravity 0*880 to 0'900,
and is of a red-brown colour with blue fluorescence. It contains 1 to 2
per cent of creosote, and has a viscosity of 1*5 to 2*5. Distillation analy-
sis ; commencement of ebullition 200° to 300° C. ; fractions passing over
up to 250°, 5 to 15 per cent ; up to 300°, 40 to 60 per cent. The flashing-
point is between 100° and 120° C. and the setting point zero to - 5° C.
Calorific power 10,500 to 10,800 cal. As its name indicates, gas oil forms
the raw material for the production of oil gas by methods which have
already been fully described by the present author elsewhere.1 All
that need now be mentioned is that this dark vaseline oil has been used for
the said purpose for a number of years, and that it fulfils all the require-
ments of a good gas oil. The yield of gas is about 875 to 975 cub. ft.
per cwt. of oil, and the illuminating power of the gas is 12 to 16
Hefner units. A suitable apparatus is an essential condition to the
production of oil gas, and careful management of same is also required,
experience showing that the fulfilment of these conditions prevents
failures due to insufficient yield, etc., which are sometimes errone-
ously ascribed to the raw material. As is well known, the chief em-
ployment of oil gas is for lighting railway carriages. Now that the
use of an admixture of acetylene has been abandoned on most railways
in favour of oil gas and incandescent burners, it is no longer necessary
to produce gas of high illuminating power, and a higher yield can
be obtained. Exhaustive experiments on this point were carried out
by Walter Hempel.2

For a number of years gas oil has been successfully used for carbur-
etting water gas. About 25 Ib. of oil are needed per 1000 cub. ft. of gas
with the usual illuminating power of sixteen candles.

Water gas,3 as is known, is made by passing steam over glowing
coke, and consists essentially of carbon monoxide and hydrogen. It
is rendered luminous by an addition of oil gas. The water gas is made
in a cylindrical iron producer, lined with firebrick ; and the gas is con-
veyed from the producer to the carburettor, where an accurately
measured quantity of oil is injected in the form of spray. The carbur-
ettor is a vessel similar to the producer, and is filled with firebricks set
crosswise one above another. Consequently the gas, striking against
these bricks on its way through the apparatus, is obliged to change its

1 Scheithauer, " Die Fabrikation der Mineralole " (Brunswick, 1895, Chapter
12 ; " Die Braunkohlenteerprodukte und das Oelgas " (Hanover, 1906), Chapter 8.

2 A Report on the Production of Oil Gas from Gas Oil, " Verhandhmgen des
Vereins zur Beforderung des Gewerbefleisses," 1903, 39.

3 Ferd. Fischer, " Kraftgas," pp. 81 et seq.

PKODUCTS FURNISHED BY SHALE OIL AND LIGNITE TAR 117

direction constantly, and the oil is vaporized by contact with the
glowing bricks. The gas, laden with oil vapours, then passes to the
superheater, the arrangement of which is similar to that of the car-
burettor, and which like the latter is raised to a uniform cherry red
heat during the gas-making process. In the superheater the oil
vapours are transformed into oil gas ; and the carburetted water gas is
then passed through the washer and scrubber, and thence to the
condenser, whence, freed from tar, and cooled, it is led to the
gasholder.1

The preparation of carburetted water gas presents many advantages
over the manufacture of coal gas, the prime cost of the plant, for ex-
ample, being only about two-fifths that of coal gas plant of equal
capacity. The floor space occupied is only about one-third that of
coal gas plant — a highly important feature in the case of large towns.
The plant is very easily started and can be worked with a small num-
ber of hands —which is also important in the event of a strike. More-
over, the water gas plant is the indicated consumer of gasworks coke,
the latter establishments being therefore enabled to regulate the price of
their coke. At present the chief purpose for which water gas plants
are erected is to supplement existing coal gas plants : for example
at Bremen, Hamburg, Magdeburg, Flensburg, Koenigsberg, Charlotten-
burg, and other towns.

Another important use of dark vaseline oil is as fuel for Diesel
motors,2 which differ essentially from the other motors consuming
mineral oils, such as petroleum, solar oil, and benzine. These motors
are of the internal combustion type, the liquid fuel being vaporized,
mixed with air, and the mixture ignited by an incandescent tube or
electrical igniter. In the Diesel motor on the other hand, the fuel —
consisting of oils of higher boiling-point than either petroleum or solar
oil — burns spontaneously.

The Diesel motor is single-acting and of the 4-cycle type. The
piston stroke draws in air, which is compressed during the return
stroke, the liquid, but finely sprayed, fuel, being then forced into the
strongly compressed and therefore hot air. The mixture burns and
the products of combustion propel the piston forward quietly but with
great force. This movement of the piston is transmitted through a
connecting rod to the crank shaft, and thence by a belt or direct
coupling. The following return stroke of the piston expels the pro-
ducts of combustion. It should be noted that, during the first stroke
— that is to say, before the fuel burns in the glowing air — the motor
works as an air engine. On this account it is provided with two com-
pressed-air cylinders for use in starting it for the first time, after which
the motor produces its own supply of compressed air by means of an

1 An exhaustive description of the manufacture of carburetted water gas by
the Humphreys process is given in a pamphlet issued by Julius Pintsch, Berlin,
the well-kno$ra makers of* this type of gas plants.

2 " Braunkohle," 3 p. 539 ; " Zeitschr. f. Dampfkessel u. Maschinenbetrieb,"
1907, No. 20.

118 SHALE OILS AND TABS

attached air pump, which also forces into the cylinder the oil fed bjr
another pump.

Over 1000 Diesel motors, ranging in capacity from 8 to 400 h.p.,
and driven by gas oil from distillation tars or by petroleum, are already
in use.

A motor (the Trinkler motor) similar in principle to the Diesel
motor is constructed by Gebriider Koerting, A.G. of Koertingsdorf near
Hanover ; but is of the horizontal l type and is equipped with an in-
jector which works without valves or any special pressure vessel. A.
number of these motors are also in use.

Apart from the low working costs, these oil motors present manifest
and great advantages over other prime movers, and in particular — so-
far as other oil motors are concerned — the fact that the fuel used has
a low fire risk, the ignition point of the gas oil used being, as already
stated, about 190° C. and over.

Gas oil is also used in making cart grease and for steam raising
purposes, having a calorific power of 10,800 cal. The heavy vaseline
oil obtained from lignite tar is also suitable for the same purposes.
This oil has the specific gravity 0'905 to 0 920, contains 1 to 3 per
cent of creosote, and has a viscosity of 2'0 to 2'66. It flashes at 115°
to 125° C. and is dark brown in colour with a greenish fluorescence.
Distillation analysis gives the following data : commencement of ebulli-
tion 220° to 250° C. ; percentage distilling over up to 250°, 5 to 10 per-
cent ; up to 300°, 10 to 20 per cent.

It was largely used for steam-raising purposes by the German
navy in the middle of the " 'nineties ". The prices, however, which
it fetches for this purpose are so low that makers prefer to sell it
for other uses when possible. The use of oil fuel per se is attended
with great advantages.2 Petroleum residue (masut) has been em-
ployed in this way for several decades in Eussia, for steamships and
locomotives, and is of special importance for naval work, the calorific
power that can be stored in the form of oil being double that of coal
of equal volume and weight, so that space and cost of transport are
saved. Other advantages of oil fuel are the absence of smoke and
ash, the considerable saving in stokers' wages, and the great cleanli-
ness that can be maintained in the stokehold. The oil is atomized by
a steam jet (forsunka burner) before ignition.

A small quantity of oil — Fat Oil — red or brown in colour, and!
similar in density and constitution to the heavy vaseline oils, is also
obtained from distillation tars. It is sold either in the crude state, or
after a process of chemical refining, the latter quality being of a yellow
colour, free from creosote, and of specific gravity 0'890 to 0*905.
This fat oil is used in making fine lubricants, and occasionally as gas
oil.

All the vaseline oils, and fat oil as well, can be used for making

1 The Maschinenfabrik Augsburg-Niirnberg has recently introduced a hori-
zontal pattern of Diesel motor.

2 Exhaustively described in the " Petroleum Review," 20, No. 450, p. 275.

PKODTTCTS FURNISHED BY SHALE OIL AND LIGNITE TAB 119

lamp-black, but their employment for this purpose is far smaller than
was formerly the case.

Several works manufacture from the heavy vaseline oils a lubricat-
ing oil which occasionally sells freely at good prices. It is, however,
inferior to the lubricating oils from petroleum, having a much higher
specific gravity and lower viscosity, its capacity to stand low tempera-
tures being also inferior to that of the petroleum lubricating oils.

All the vaseline oils above specific gravity 0*880 still contain small
quantities of paraffin, increasing in amount with the specific gravity.
This paraffin, however, does not separate out until the oil is cooled to
a very low temperature, and is, moreover, not crystalline but of the
consistence of ointment. It must, as a rule, be regarded as non-re-
coverable.

The By-products.

The creosote oil (specific gravity 0*940 to 0*980) contains 40 to 60
per cent of creosote, and the greater portion of it is soluble in sulphuric
acid of 66° B. strength. The distillation analysis gives the following
results : commencement of ebullition 150° to 170° C. ; fractions pass-
ing over up to 200°, 5 to 10 per cent ; up to 250°, 30 to 40 per cent ; up
to 300°, 60 to 70 per cent.

Creosote oil is used as a disinfectant, and occasionally for impreg-
nating timber. For the former purpose it is equal in value to the oils
from coal-tar. Its objectionable smell is due to the presence of sulphur
compounds. The oil may also be employed for making lampblack and
for steam raising.

The paraffin grease is used as an adjunct in the preparation of
asphaltum products and lubricants, but is not met with largely as a
commercial article.

The soda-tar, which in the undiluted condition contains nearly
50 per cent of creosote, is used in lignite mining as an impregnating
material for the pit timbers, for which purpose the low flashing-point
of creosote oil renders the latter unsuitable. The creosoting process
is carried on in closed tanks, and has been fully described by Vollert.1

The creosote contains up to 30 per cent of water, but only a little
oil, and is almost completely soluble in caustic soda of 38° B. strength.
It is sold in this condition, and is either used as a disinfectant or else
sent for purification.

The asphaltum, lignite pitch, is usually sold in loose blocks, or
more rarely in open casks and metal drums, or broken in pieces and
packed in bags. It is brittle, has a conchoidal fracture and a shiny,
deep-black appearance. It softens at 60° to 70° C. and melts at 90° to
100° or over. It is used for mixing with natural asphalt, and when
dissolved in oil of turpentine, benzine or benzol, may be employed in
the preparation of lacquer varnishes.

The "goudron" is also black, but is softer -than the asphaltum,

.* " Der Braunkohlenbergbau im Oberbergamtsbezirk Halle a. S.," pp. 161 et
seq. (" Lignite Mining in the Halle Distiict").

120 SHALE OILS AND TABS

being of about the same consistence as soft bread. It can be kneaded
between the fingers. Two kinds of this goudron are known in com-
merce : the one obtained by the distillation of oils is much softer than
that from refinery waste, and is therefore higher in price. A softer
variety, with a larger oil content, is known as oil goudron.

Goudron is put on the market in closed casks and is mixed with
paving asphalt and wood cement, as also as an insulating material
for building purposes.

The employment of the retort coke has already been described
(p. 76).

Up to the present it has been found impracticable to manufacture
pure tar acids on a large scale, and the prospects in this direction are
slight.

On the other hand, the recovery of purified nitrogenous bases has
been successfully carried on in several works (see p. 91), an impetus
being given by the employment of the pyridin bases for denaturing
spirit, in accordance with the German Law of 24 June, 1887. Owing,
however, to their low content of pyridin — the series of bases com-
mencing essentially with the two picolins — these bases from lignite
tar proved incapable of satisfying the subsequent, more strigent re-
quirements, and they very soon lost this market. Their uses in other
respects being very restricted— for instance in the purification of anthra-
cene according to Ger. Pat. 42,053 — the manufacture of these bases
never attained any great extent in the mineral oil industry. The only
commercial articles of any importance were the products boiling at
200° C. and between 200° and 250° ; and the far more preponderating
bases of higer boiling-point have not yet even been isolated.

The Paraffin.

The solid hydrocarbons, of the fatty series, recovered from distilla-
tion tars are known, commercially and technically, as paraffin.

Paraffin is the most valuable of the commercial products of the in-
dustry, and its proportion largely influences the value of the distilla-
tion tar. In its refined condition the paraffin from the lignite tar is
colourless, of crystalline structure and translucent with a bluish tinge.
It is not milky, but transparent, and is therefore regarded with favour
in commerce.1 It feels dry, not greasy. The harder kinds are reson-
ant and lustrous, the softer grades dull in both respects. Paraffin is
soluble in lignite-tar oils, benzol, chloroform, ether, carbon disulphide,
and carbon tetrachloride, as also in all volatile and fatty oils. It is
only partially soluble in amyl alcohol and hot ethyl alcohol, and quite
insoluble in the latter when cold. In the melted condition it is miscible
with spermaceti, wax, stearine, resins, and animal and vegetable fats.

Paraffin is capable of resisting acids and bases to a certain extent ;
but though unattacked by hydrofluoric acid is susceptible to the action
of nitric acid and chromic acid.

1 " Chem. Ztg.," 1906, 61.

PRODUCTS FURNISHED BY SHALE OIL AND LIGNITE TAR 121

The melting-point of the paraffin manufactured at the present time
varies between 35° and 62° C., though at one time still softer grades,
melting as low as 27°, were produced. Grades melting below 50° C.
are classed as soft paraffin, and those of higher melting-point as hard
paraffin.

Paraffin ignites at 160° to 165° C. and volatilizes at 350° to 400°.
The specific gravity rises with the melting-point, being, at 20° C.,
0-883 for the grade melting at 45°, 0-908 for that melting at 51°, and
0-915 for that melting at 58° C. According to Bolley, the specific heat
of paraffin is 0*683. It is a non-conductor of heat and electricity ; and,
according to Edison, its insulation resistance amounts to 110 megohm-
centimetres. Though, under the influence of Bontgen rays, air becomes
a conductor of electricity, this is not the case with paraffin.

For sale, hard paraffin is cast in dished moulds holding about 2£
Ib. These moulds float on the surface of the cooling water, and are
immersed as soon as the surface of the paraffin has set to such a de-
gree as to be impermeable to water. Owing to the difficulty of detach-
ing soft paraffin from the moulds, this grade is not cast, but is allowed
to cool, in a layer about 1J in. thick, on the surface of the cooling
water, and is then cut up into cakes of suitable size.

Paraffin of low melting-point (35° to 40° C.) is also sold in the crude
form as scale, and is used mainly in the manufacture of matches, the
annual consumption for impregnating match sticks being 800 to 1000
tons. The extent of this industry may be gathered from the fact that the
paraffin used is equivalent to only 5 to 8 per cent of the total weight of the
output. The crude paraffin is broken up in simple cmsrretfs'or-centri-
fugal mills, from which it is delivered, as a white powder, into casks, in
which it is rammed down.

The chief use of paraffin is for moulding candles, a process which
will be fully described in the next chapter. Candle factories are at-
tached to several of the mineral oil and paraffin works in the Saxon-
Thuringian industry. Statistics showing the extent of this branch of
manufacture will be found in Chapter XII.

Paraffin also finds employment in various other ways. It is used
for impregnating paper, linen, and leather ; as a dressing for textile
fabrics, and for finishing turned articles of animal and vegetable fibre.
It forms a valuable insulator, and is used as a substitute for oil baths
in chemical laboratories. In the pharmaceutical industry it serves as
a binding medium for ointments, and for sealing vessels. In the toy-
making industry it is used to make the waxy covering on dolls' heads ;
for feeding lamps in glass-blowing works, and for cooling baths in the
production of hardened glass. The interior of vessels, casks, etc., is
coated with paraffin, to prevent the contents from tasting of the wood.
Paraffin is also used as an impregnating material in breweries.1 Of
late it has become the custom to employ a bath of melted paraffin to
impart a permanent brown colour to sword scabbards by dipping the
red-hot steel in same.

1 " Chem. Centralbl.," 1908, No. 6.

122

SHALE OILS AND TARS

B. THE PEODUCTS OF THE MESSEL INDUSTRY.

Yield obtained from the Tar.
The distillation tar (cru.de oil) produced at Messel yields : —

Naphtha

Gas oil

Crude paraffin ....

Gas, coke, and loss in refining .

4-0 per cent.
63-0

7-5 „
25-5

The Oils.

The 'oils coming under consideration are : gas oil, motor spirit,
cleaning oil, fat oil, spindle oil, and lubricating oil.

As mentioned on p. 36, in the distillation of Messel coal it is not
necessary to take into account the destruction of the bitumen which
impedes the refining of the crude oil. The dry-distillation process can
be carried on in a current of steam so as to afford extensive protection
to the purely fatty character of the oils. As a result of this circum-
stance, Messel gas oil is distinguished by high gasification value. Its
specific gravity is low, ranging between 0'865 and 0'872.

The motor spirit has the specific gravity 0'800, and is extensively
used in petroleum engines.

Cleaning oil consists of tjie fractions with specific gravity 0*825 and
0-835.

The fat oil has the specific gravity 0'860. The lubricating oil has
the specific gravity 0'090 to 0'892, and is used for light machinery.

The Paraffin.

The paraffin is distinguished by its waxy character and very small
crystalline structure, and is not pulverulent.

There is no need to discuss more closely a number of smaller pro-
ducts such as tumenol, pyrocatechin, etc.

C. THE PRODUCTS OF THE SCOTTISH INDUSTRY.

Yield from the Crude Oil.
At present, the crude oil furnishes : —

3 — 5 per cent.

20—25

15—20

7—9

3—5

2—3

25—30

Naphtha „ .
Lamp oil
Medium oil (gas oil)
Lubricating oil

Hard paraffin ., v
Soft paraffin .
By-products .
Water, gas, and loss

The Oils.

In order to finish off the oils intended for sale, they are put into
shallow wrought-iron tanks, about 13 ft. long, 40 in. wide, and 2
ft. deep. - Steam coils are arranged underneath these tanks, but must
not be laid on the bottom of same, since the oils would be darkened
in colour if brought into contact with hot surfaces. The oil is kept at

PRODUCTS FURNISHED BY SHALE OIL AND LIGNITE TAR

a temperature of 35° to 40° C. (95° to 104° F.) until clarified, whereupori
it is run into barrels through a tap provided some distance above the
bottom of the tank. The water separating out from the oil is drawn
off through a tap at the bottom. Automatic apparatus is used for filling
the barrels.

Several grades of benzine are put on the market, the lightest
(specific gravity 0*600 to 0*690) being used for the production of
air-gas and as motor spirit. The ordinary naphtha (specific gravity
0*725 to 0-745) is burned in special lamps for lighting workshops,
yards, etc. This benzine also finds employment as a solvent of
various substances such as fats, gum, resin, etc. All the benzines are
colourless and have low boiling-points.

The oils of specific gravity 0-785 to 0-830 are used as lamp oils in
lamps of various patterns.1 The. oils are colourless, the heavier kinds
alone having a yellowish tinge. The flashing-point is 52° to 53° C.
(125-^° to 127£° F.), and the oils are therefore very safe.

The lightest oil — water-white oil — of specific gravity 0*785 is used
for continuous lighting in buoys and lightships ; and is also employed
as motor spirit. Another light oil — lighthouse oil — is used, as its
name implies, as an illuminant for lighthouses.

The medium oils, corresponding to tlie light and dark vaseline oils
of the Saxon-Thuringian industry, are yellow to dark red in colour
and have the specific gravity 0*840 to 0-870. The flashing-point is
above 68° C. (155° F.). The more volatile members are used as
cleaning oil, but their chief employment is as gas oil for producing oil
gas. Like the same oils of the Saxon-Thuringian industry, they may
be used for carburetting water gas, as motor oils and for steam
raising.2 The grades known as " Intermediate I and II," and also'
the "blue oil," belong to this group.

Lubricating oils of specific gravity 0*865 to 0*910 are made.
They are yellow or dark in colour, and may be regarded as lubricants
of medium quality. They are sold both pure, and mixed with vege-
table or animal oils.

The By-products.

Paraffin grease is recovered in some works by distilling the tar or
heavy oils, as in the Saxon-Thuringian industry, and is used in making
cart grease.

The uses of the waste products of the refining process have already
been described (p. 94). The mixture of acid resins and soda-tar is
clarified by boiling, and is then used for impregnating timber, for mixing
with asphaltum, and for painting ironwork.

The Paraffin.

Owing to the method of preparation, the paraffin is somewhat dif-
ferent in character from that obtained in the Saxon-Thuringian industry.

1 Fully described in " Chemical Technology," pp. 243 et seq.
aAs might be expected, the tests carried out in the English Navy proved
satisfactory. Grafe, " Die Schottische Schieferteerindustrie " ; " Petroleum," 6, 79.

124 SHALE OILS AND TABS

The melting-point varies between 43° and 59° C. (117° to 138° P.),
small quantities of a softer grade (melting-point 100° F.) being also
produced. The paraffin has no decidedly crystalline structure, is not
translucent, and does not exhibit the bluish tinge. It is sticky and can
be drawn out if slightly warmed (" drawn paraffin "). \ •

It is chiefly used for making moulded candles ; but, owing to its
properties as described, is difficult to detach from the moulds — a point
that has to be taken into consideration. In other respects it is suitable
for the same purposes as the product of the Saxon-Thuringian industry.
The soft paraffins are employed either in making matches or as an
illuminant for miners' and ships' lamps.

CHAPTEE IX.

CANDLEMAKING.

HISTORICAL.

PROBABLY in no other branch of industrial life has such great progress
been made in the course of time, or such great contrasts presented
between formerly and now, as in the lighting industry. One stage in
the history of this branch is formed by the candle, which has been
developed from a primitive type to the perfectly burning illuminant now
produced in numerous forms.

The earliest primitive illuminant was the camp fire, built up of logs.
Later on, when man abandoned his nomadic habits, settled down
and built huts, the camp fire was replaced by that on the domestic
hearth, round which the family gathered in the evenings, as described
by Homer,1 who also spoke of the discomfort caused by the smoke.
Apart from the fire, the torch was used, as the only portable light ;
and the torch sconces are also described by the same Greek poet.
The earliest torches were made of pine splinters; and subsequently
bundles of twigs or vine stalks, soaked with fat or pitch, were used for
the same purpose. Indoors, these smoky torches were replaced by
animal fat moulded in hollowed stones or shells, moss or the pith of
rushes being used as wick, in the same manner as practised among the
Aleutians and Esquimaux at the present day.

These torches and simple lamps were afterwards superseded by
candles, which at first consisted of strands of hemp or vegetable pith
soaked in tallow, but later on were made by pulling or dipping.2

The candle sconces were of various kinds : wood, clay, bronze, or
lead. A candleholder found in Crete and dating from the Mycenean
epoch, has a protecting plate like some old church candlesticks still in
use, the candle being stuck on a pointed spike. If wanted for use out-
of-doors, the candles were put in earthenware lanterns, provided with
lateral openings which were probably covered over with pig's bladder.
Lanterns of this pattern have been found in many places in Greece.
The first mention of glass panes is met with about 400 A.D. in Isidorus,8
though they were probably in use at an earlier period.

1 " Odyssey," 6, pp. 305-310.

2 See later in this chapter, and also Scheithauer, " Die Fabrikation der Min-
eralole," p. 243.

3 "Isidorus," 20, 10, 7; " Journ. f. Gasbel.," 1907, 1128.

(125)

126 SHALE OILS AND TAES

No great progress was made in illumination during the Middle Ages.
Pine torches were used in the country and candles in the towns, the
rich having wax candles, and other classes those of tallow or lard.
Church lighting was the cause of the great extension of the wax candle
industry.

The enormous consumption of candles for church purposes may
be gathered from the records which state that, previous to the Eeforma-
tion, 25,750 Ib. of wax candles were burned every year in the principal
church at Wittenberg, and that the Church of St. John Lateran l had
174 candelabra holding 8730 candles, which were lit on all festivals ;
and all of these must have been wax candles, the regulations being
very strict on this point (" Nulla lumina nisi cera adhibeantur . . .
cera ex apibus parata"). This great consumption of candles gave rise
to a very flourishing candle industry, which, however, was conducted
with very primitive appliances. In addition to the drawing process,
the moulding of candles was also known,2 especially for the production
of wax candles. The candles were thickened progressively by casting
fresh wax round them as they cooled. The large thick candles were
made by rolling out the wax and then lapping and rolling it round
the wick. Moulds of a simple character were also used occasionally.
The moulding process has been in use since the middle of the fifteenth
century, the candles being of fallow at first and subsequently of wax.
The Wax Chandlers' Company was established in England in 1484
for making wax candles.3

The candle industry exerted an influence on artistic handicrafts in-
asmuch as candelabra, some of them of high artistic value, were made.
Marvellous specimens of this work have been preserved, for example
the candelabra, from the time of Bishop Hezilon (1044-1055) in the
cathedral at Hildesheim, and that of the Emperor Frederick Barbar-
ossa in Aachen cathedral.

From the seventeenth century onward, pine- splint torches began
to go out of use, whilst torch and candle lighting increased in favour ;
and at the present time, pine-splint torches are only used in remote
mountain valleys, as described by Eosegger. Candle wicks were first
made of twisted tow, and afterwards of cotton ; and the wick remained
sticking up in the middle of the candle, the combustion being slower
than that of the candle material, so that they had to be " snuffed " at in-
tervals, with snuffers, in order to keep the light burning brightly.

Goethe expressed his discontent with the trouble produced by this
operation by lines, which, freely rendered, run as follows : —

What better proof of an inventor's might

Than candles make, sans snuffers, to burn bright.

It was not until the introduction of plaited wicks, impregnated
with chemicals, that a uniform flame which would burn without

1 " Journ. f. Gasbel.," 1908, 347.

2 Scheithauer, " Die Fabrikation der Mineralole," pp. 243-4.
3 " Chemical Technology," p. 69.

CANDLEMAKING 127

snuffing could be obtained, wicks of this kind curling over and burn-
ing at the edge of the flame with the same regularity as the material
of the candle. This advantage, however, was confined to candles
made of wax, spermaceti and stearine— introduced by Chevreul in-
1820 — the tallow candles with plaited wicks still continuing to burn
askew and gutter owing to the low melting-point of the tallow.
;; Up to the 'thirties of the last century, candlemaking continued to
be a home industry, except for a few small factories ; and it was not
until later that the first large candle works — that of De Milly, at Paris
• — was founded on the instigation of Chevreul. About the same time
paraffin was discovered by Eeichenbach, who recognized it as an im-
portant material for candlemaking. In this branch its use has in-
creased beyond any other material, including the ceresine obtained,
especially in Austria, by refining ozokerite. Before technical improve-
ments had enabled pure white paraffin to be produced, it was usually
mixed with wax or stearine, the mixture being coloured and made into
candles ; but early in the 'sixties it was found practicable to dispense
with these adjuncts and use paraffin in the uncoloured condition.

At the outset, soft paraffin was used for moulding candles in the
Saxon- Thuringian industry, as is still done for inferior grades of candles
in the Scottish industry. Moreover, a tjiinner kind of candle was
made at first, this naturally tending to bend and run. These circum-
stances which constituted a serious error were to blame for the paraffin
candle being estimated below its deserts in . its original homeland.
Through the instigation of C. A. Eiebeck, however, hard paraffin alone
has been used for candlemaking since the end of the 'sixties. T^he
high importance of candlemaking to the mineral oil industry of Saxon
Thuringia can be gathered from the statistics given in Chapter XII.

Apart from the good raw materials, stearine and paraffin, the im-
proved wicks and careful preparation have contributed to furnish satis-
factorily burning candles such as are now put on the market by the
industry in question. Paraffin and composite candles, made from im-
ported paraffin, are also produced by a number of small makers in
other parts of Germany.

The Haw Materials.

(a) The Candle Material. — The larger proportion of the paraffin
produced in the lignite-tar industry is marketed, not as such, but in the
form of candles ; and for most of the works, the manufacture of candles
is merely a means for providing an outlet for the raw material, paraffin.
It is not every kind of paraffin that is suitable for making into candles
in the condition in which it is produced. On the one hand, the paraffin
candle must be of sufficiently high melting-point to keep it from bending
in the warm ; and it is only a portion of the total paraffin made that
has the requisite melting-point of over 53° C. (127-J0 F.) for that purpose.
A considerable proportion melts at a lower temperature, and must be
mixed with either a harder paraffin or a considerable amount of stearine
to give it a suitable degree of firmness. The candles made from this

128 SHALE OILS AND TABS

latter material are known as " composite " candles, for which a par-
affin of lower melting-point (about 48° to 52° C.) can be used — or even
lower when the percentage of stearine is large.

Soft paraffin, as already mentioned, can have its melting-point
raised by an addition of hard paraffin ; and the melting-point of the
mixture can be calculated from the quantities and melting-points of
the components taken. Thus, for instance, a mixture of equal parts
of paraffins melting at 55° and 49° C. respectively, will have the melt-
ing-point 52°. Candles of perfectly pure paraffin are seldom put on
the market, owing to the tendency of the pure material to stick in the
moulds when cold. This defect can be remedied by the addition of J
to 2 per cent of stearine. Only when cooling water of very low tem-
perature is available, can paraffin candles be made without any stear-
ine or with less than the proportion mentioned above.

Petroleum paraffins, which are now produced in large quantities
in the manufacture of lubricating oils, are also used in candlemaking.
These paraffins, however, are far more liable than lignite-tar paraffin
to bend in the warm ; and in order to obtain the same degree of firm-
ness, it is necessary either to use a paraffin of higher melting-point, or
else increase the proportion of stearine.

The commercial varieties of paraffin candles have about the follow-
ing melting-points : —

1. Paraffin candles melting at 52° to 53° C. (125£° to 127|° F.)
'.>. Brilliant candles „ „ 53° to 54° C. (127£° to 129$° F.)

3. Crystal candles „ „ above 54° C.

4. Composite candles, made of paraffin melting at about 50° C. (122° F.).

Paraffin candles are more transparent in appearance than com-
posite candles, which are more milk-white, like pure stearine candles.

Some of the candles are also coloured, especially those intended
for export or for Christmas trees.

The material next in importance, though not produced in the in-
dustry itself, is stearine, a mixture of stearic acid, palmitic acid, and a
little oleic acid, prepared by the dissociation of fats. The fats, con-
sisting of fatty acids and glycerine, are decomposed into their com-
ponents by a saponification process which need not be detailed, the
fatty acids being then purified by pressure and distillation, and the
more solid constituents, stearic acid and palmitic acid, are put on the
market as stearine. A certain proportion of oleic acid, which is liquid,
ig always present and lowers the melting-point of the stearine. Only
the better qualities, melting at about 50° to 55° C. (122° to 131° F.),
are used for making paraffin and composite candles. The grades with
low melting-points are high in oleic acid, and vice versa, many of the
most fusible containing 25 to 30 per cent of oleic acid, whereas the firmer
kinds have only 2 to 3 per cent. In addition to lowering the melting-
point and softening the stearine, oleic acid has the defect of readily
turning rancid and imparting an unpleasant smell to the candles, es-
pecially during storage. Moreover, in consequence of its avidity for
oxygen (being an unsaturated compound), it has a bleaching effect on

CANDLEMAKING

129

any colouring matters added to the candles. For these reasons, 'the
selection of suitable stearine, low in oleic acid, is a most important
point in controlling the raw materials.

The ilium nating power of a candle is greater in proportion as it con-
tains more paraffin and less stearine, since the oxygen in this stearine
constitutes nothing but ballast and is of no value to the ^Ruminating
power.. Weight for weight, paraffin candles give about half as much
again light as stearine candles, composite candles occupying an in-
termediate position according to the proportion of stearine they con-
tain.

It should also be mentioned that mixtures of stearine and paraffin
h ive always a lower meiting-point than their components, the reduc-
tion following Eaoult's law of congelation in a fairly regular manner,
as has been shown by the author1 (Fig. 61). The maximum reduc-
tion is about 6° to 9° C., accord-
ing to the kind of stearine and
paraffin used ; and is produced
when the materials are mixed in
approximately equal amounts.
In spite of this low melting-
point, however, mixtures of
stearine and paraffin are always
better able to stand the in-
fluence of warmth than pure
paraffin. This is the true reason
for adding stearine, the white-
ness of colour being merely a
secondary consideration. Mis-
conception exists on this point
in some quarters, the colour

ss~

£4'
S3'
52'

SO'
43"
4S°
47'

46"
45"
44°

A3°

\-J

Stearin WO 90 80 7O 60 SO 4O 3O 2O JO O

O 1O 20 30 40 SO 60 70 SO 90 1OO Paraffin

FIG. 61.

being regarded as the principal thing, and attempts being made to
obtain whiteness by replacing the expensive stearine by cheaper sub-
stitutes or such (though this is little needed) as make the material
white and opaque. Substances that have been proposed for this
purpose include : alcohol, /?-naphthol, vaseline oil, and a whole series
of other organic products. All of them, however, have certain
defects, apart from the main drawback that they do not make the
candles any firmer. Thus, alcohol evaporates during storage, /3-naph-
thol has a strong smell and causes the candles to become discoloured
after a short time, whilst vaseline oil makes the candles feel greasy
and stains the packing material. Eecently, it has also been proposed
to employ refined mineral wax or the anilide or amide of stearic acid
as substitutes for stearine, for, whilst these substances are dearer than
stearine itself, only a very small quantity is needed to whiten the
candles. This was considered a useful move as it falsifies certain
melting-point tests based on the cloudy or opaque appearance of the

1 Grafe, " Braunkohle," 1904, No. 9, p. 111.

130 SHALE OILS AND TABS

material on solidification, and mikes the melting-point seem higher
than it really is. The reason for this fictitious appearance is that the
added materials crystallize out when the paraffin cools, and produce
the impression that the whole mass has solidified : whereas, in reality,
the apparently solid mass is in a pulp until just above the melting-
point of the paraffin, and the latter can still be forced out by pressure.
The author l carefully investigated the matter some years back, and at
the present time, candles made of such materials are rarely found in
commerce.

(b) The Wick. — A well-made wick is an important feature in
candles. The wicks used at present are almost exclusively made of
plaited cotton yarn, though wicks of artificial silk or twisted paper-
have been tried experimentally, but abandoned as unsuitable. The
weight of the wick should always bear a certain relation to that of the
candle ; if too thin, the wick is unable to absorb the melting material
of the candle and the latter begins to run, whilst if the wick be too
thick the flame smokes. The right proportion is about O35 to 0'45
per cent of the weight of the candle. The number of threads in the
wick is not particularly important, for a wick plaited from a few
strands of coarse yarn may burn just as well as one made of a number
of slender threads, provided its weight be proportionate to that of the
candle. Wicks of round section are now rarely met with, the general
shape being flat and containing three to four strands, each consisting
of several threads. The advantage of flat wicks is that they bend over
in burning and are consumed at the edge of the flame, the former
troublesome snuffing being thus rendered superfluous.

The yarn composing the wicks may be either bleached or grey, the
former being generally used for thin or transparent (paraffin) candles,
the colour of which would be rendered unsightly by grey wicks ; but
these latter may be employed for composite or stearine candles. The
wick cannot be used direct for candlemaking in the form in which it
comes from the plaiting machine. In some cases the threads are too
tightly twisted, and in many instances the fresh wicks bend over more
rapidly than when they project from the edge of the flame, curling up
in a spiral and causing the candle to smoke and gutter. Experience
shows that such wicks answer quite well when they have been kept
for some time before use, the threads having lost their tension. More-
over, every wick has to be prepared by treating it with chemicals,
such as ammonium phosphate, ammonium sulphate, boric acid, sal
ammoniac, calcium chloride, saltpetre, borax, ammonium nitrate, etc.

It is a good plan to treat the wicks with about -£ per cent of sul-
phuric acid at first, then immersing them in a 1 to 2 per cent solution
of the chemical agent, with which they are boiled for some time, and
are finally centrifugalized, or pressed, and dried. The object of the
preparatory treatment is as follows : —

The ammonium salts prevent the wick from burning away too

1 " Chem.-Ztg.," 1904, No. 95.

CANDLEMAKING- 131

quickly ; and as the wick is consumed, the residual phosphoric acid
and boric acid fuse together into a bead, which takes up the small
amount of ash left by the wick, and prevents this from falling into the
hollow at the top of the candle. If this were not done, the ash
would form a crust on the wick and act as an auxiliary wick, absorbing
the candle material too freely and causing the candle to gutter or
smoke. One defect of the wick is that, when the candle is first lighted,
it takes some time to burn down far enough to reach the candle
material, and on this account a fresh candle always takes a certain
time to light up properly. Attempts have been made to remedy this
defect, in some cases by slightly widening the bore in the plunger of
the candle machine, so that the end of the wick could be surrounded
by a thin film of candle material ; or, as in English Patent No. 3438
of 1905, by dipping the wick end in a solution of celluloid, which in-
creases the inflammability of the wick. In practice, however, this in-
vention does not seem to have made headway.

The prepared and dried wicks are wound into balls or on rollers, any
defects in manufacture being then detected and remediedT The balls
or rolls are stored in a dry place, the wick yarn being fairly hygroscopic
and capable of absorbing over 5 per cent of moisture from the air
— a circumstance that, naturally, has n$ favourable influence on the
burning qualities of the wick.

(c) The Colouring Matters. — In addition to the actual candle ma-
terials, paraffin, stearine, and wick, various colouring matters, mostly
organic, are employed. Formerly, use was also made of inorganic
pigment, such as Schweinfurt green, vermilion, chrome yellow, and
others. Of these inorganic pigments, verdigris (copper acetate) alone
is still used to some extent ; but even this is mostly replaced by aniline
dyes. The presence of verdigris is revealed by the coppery tinge of the
end of the burnt wick, as can often be seen in Christmas tree candles.

Formerly, in addition to inorganic pigments, organic colouring
matters of vegetable origin were employed ; but these also have been
replaced by the more suitable aniline dyestuffs. Most of the organic
colouring matters belong to the triphenylmethane series and the phtha-
leins, for example : victoria blue, methyl violet, brilliant green, and
malachite green, rhodamine 6G and rhodamine 6B. Quinolin yellow,
which is very fast to light, is generally used for yellow. The chief
property required of the colouring matter is that it shall be fast to
light and not become discoloured during storage, this latter point being
if anything more important than the former, since the candles are not
exposed to direct sunlight except in rare instances, whereas on the
other hand it not infrequently happens that they have to be stored
for a year or more, and in these circumstances it is highly essential
that the colour should not fade more than slightly if at all. Bleaching
in storage is not always the fault of the colouring matters, but in many
cases is also due to the character of the stearine used, such as is rich in
oleic acid being, as already mentioned, specially harmful in this respect.
Green is the colour most liable to fade, and the one that needs most

132 SHALE OILS AND TABS

care in the selection of the colouring matter and stearine. The evil
cannot, however, be prevented entirely. For these reasons, a stearine
of high melting-point and low oleic acid content, and whose pro-
perties have been tested beforehand, is preferably used for green
candles. Some commercial makes of coloured candles are not
coloured right through, but have a white core surrounded by a
coloured shell. These are made by dipping white candles into a bath
of coloured candle material and taking them out again quickly. The
transfer pictures and other decorations with which many candles are
embellished are applied after the candles have been moulded.

The quantity of colouring matter generally used for staining the
candle material is small, amounting to only a few parts per thousand.
The dye-stuffs are either dissolved in stearine and added to the paraffin
— since pure paraffin has a very small direct solvent capacity for these
substances (e.g. Soudan red) — or else an alcoholic, or similar solution
of the colouring matters is stirred into- the stearine, and then into the
paraffin. Even these small quantities of colouring matter, however,
are sufficient to affect the burning of the candles, plain candles always
burning better than coloured ones. Attempts have also been made to
perfume candles, by means of scents with an agreeable smell or such
as give off disinfectant vapours when the candles are burning. Candles
of this kind, however, are mrely met with — at all events they are not
made on a large scale in any of the large works.

The Manufacture.

(a) The Moulding Process. — The course of operations in candle-
making will now be briefly described. Formerly, when candles were
chiefly made of wax and tallow, they were produced by dipping the
wick repeatedly into the candle material, which was allowed to set
after each immersion, thus gradually accumulating a number of layers
round the wick until the required thickness and length were attained.
When, however, the introduction of the new materials, stearine and
paraffin, raised candlemaking to a large industry, this method of pro-
cedure proved no longer sufficient. At first the candles were cast in
sheet -iron moulds, which were in turn replaced by cast moulds of fusible
metal. These moulds were used singly at first, each being provided
with a charging funnel ; but improvements in the plant led to the as-
semblage of a number of separate moulds in a frame, provided with a
charging hopper or trough and fitted with a special device for ejecting
the candles. A machine of this kind is represented diagrammatically, in
Fig. 62. The mould is traversed by a plunger, mounted on a tubular
carrier. When the plunger is at its lowest position, it closes the mould,
so that the liquid candle material can be poured in.

The material is then cooled down to setting point by the action of
water, and when the candles are set, the plunger is forced upward,
pushing the candle before it, the latter being gripped by the clamps at
the top of the machines, as shown in the figure. The plunger being then
lowered 'again, the mould is ready for another pouring.

CANDLEMAKING

133

iff/

The wicks are housed in a box under the machine and containing
the rollers or tins for the balls. Each wick is
passed through the plunger carrier and through
a bore in the plunger, the now of candle material
through the latter being prevented by a rubber
washer. This rubber is sufficiently elastic to
allow the wick to slide past it, whilst pressing
tightly enough against the wall of the bore to pre-
vent the passage of any candle material.

The candle from the previous pouring, being
held overhead by the clamp, keeps the wick truly
centred in the mould — a point of some import-
ance to the proper burning of the candle. The
forcing up of the plunger takes some considerable
power, and since a candle machine contains 100
to 400 moulds, the power must be applied by
step-down gearing or by a worm.

The moulds themselves are made of a mixture
of tin and lead, containing a little bismuth and
antimony, and are cast on a highly polished man-
drel, so that their interior surface maj^be per-
fectly smooth. It is of importance that the alloy
should not be attacked by the candle material,
since moulds that are rough inside make the
candles very difficult to eject. Attempts have
been made to introduce other materials for the
moulds, such as glass, and more recently of
porcelain. Unfortunately, moulds of this kind,
though . they are perfectly smooth inside and turn
out fine candles with a shining surface, cannot be
made so uniform in size as to be fitted into the
usual candle machine without forcing ; and they
also taper sometimes towards the upper end so
that the candles cannot be ejected. The intro-
duction of such moulds of uniform measurements
would be a great improvement, if it were possible,
since porcelain is naturally endowed with a high
power of resisting chemical agencies. On the
other hand, metal moulds have the advantage
that they can be melted down and made up again
when worn out, whereas worn or broken procelain
moulds are almost useless. In a new type of
candle machine, the moulds are not supported
directly by the machine, but are inserted into brass
or copper tubes in same, thus saving material,
labour, and cooling water.

The moulding of candles in the machine is

FIG. 62.— Caudle
Machine.

(Kl = Clamp. Ke =
Candle. A = Top.
F = Mould. K =
Cooling water. Ko
= Plunger. G =
Rubber washer.
Kol = Plunger car-
rier. B = Movable
rail for plunger car-
riers. D == Wick.)

carried on in the following manner : the paraffin produced in the tar

134 SHALE OILS AND TABS

works is sent in a liquid form to the candle works, whilst bought paraffin,
which is in the solid state, has to be melted. This is performed nearly
always by direct steam in wooden vats, the condensed water being drawn
off brfore the paraffin is poured into the moulds. Keceptacles in which
materials containing stearine are kept for any length of time are made
partly of earthenware and partly of tin, these being found to wear best ;
but as a general rule the prolonged storage of such material in the
molten condition is avoided, owing to its liability to discoloration.

Before pouring, the material has to be clarified by the addition of
a little oxalic acid or aluminium sulphate. The object of this treat-
ment is to remove salts of lime (originating in the water) which would
otherwise combine with the stearine and affect the burning of the
candles. With such salts aluminium sulphate forms a precipitate of
very finely divided alumina, which carries any mechanical impurities
down with it. The salts formed by the reaction are drawn off along
with the water.

The moulder fills a can (fitted with one or two spouts) with the
candle material, and takes it to the machine, though some works have
successfully adopted the practice of feeding the molten material direct
to the machine through pipes. This is chiefly done with candle
material low in stearine ; but it would also pay to experiment in the
same way with material that is rich in stearine, in which case it would
be necessary to use pipes capable of standing the action of stearic acid,
namely a suitable ceramic material or resistant metal. To prevent the
candle material from solidifying in the pipes, the latter are adapted to-
be heated, the simplest way being to enclose them in a leaden or copper
steam jacket pipe. Before the candle material is poured into the
machine, it is stirred up again, to prevent the heavier stearine from
accumulating at the bottom of the can — that is to say if it is only
added to the paraffin just before use, since, once thoroughly incorpor-
ated, the two cannot separate, the mixture being then comparable to a
solution.

Before pouring the material into the machine, the latter must be
warmed up by admitting steam into the jacket surrounding the moulds.
If this were not done, but the candle material were poured into the
cold machine, it would begin to set at once against the cold sides of the
moulds, and consequently, any air bubbles carried into the moulds,
would be prevented from escaping, and the candles would have an
unsightly pitted appearance. In all cases rather more candle material
must be poured in than is required to fill the moulds, so that a layer
nearly an inch deep remains in the trough. This is necessary for
the following reasons : —

In its liquid state the candle material is specifically much lighter
than when solid, and therefore contracts, in setting, to an extent that
has been ascertained by the author to amount to about 11 to 14 per
cent. If only just enough material to fill the moulds were poured in,
cavities would be formed in the interior of the candles, and might even
render them useless ; but when an excess of material is present in the

CANDLEMAKING 135

trough, it can run down into the moulds under the force of suction ex-
erted by the candles in setting. When the machine has been charged,
warm water, from a previous operation, is run through the jackets to
start cooling down the moulds, the complete cooling being afterwards
effected with cold water. In a quarter to three-quarters of an hour,
according to the thickness of the candles, the material will be cool
enough for the ejection of the candles from the moulds.

The wicks of the candles still left from the previous operation in
the clamps or sleeves are cut off with a triangular knife, the clamps
are tilted up and the candles removed. After clearing out the surplus
material in the feed trough, the clamps are lowered, and the candles are
ejected from the moulds by winding up the plunger rail, the candles
coming within the sphere of action of the clamps.

By turning an eccentric lever, the clamps are caused to grip the
candles firmly, being lined with plush in order to prevent the candles
from being crushed by the pressure. The plunger rail is lowered to
bring the plungers back into their lowest position, thus tightening and
centring the wicks, the upper ends of which are, as it were, anchored
in the candles held by the clamps. This done, the machine is ready
for pouring again.

According to the size of the machine^ 100 to 400 candles are pro-
duced at each pouring ; and in America, for instance, machines turning
out 800 candles at a time have been made. Such large machines may
be suitable where labour is dear, but otherwise they cannot be recom-
mended, being difficult to supervise and awkward to get at in the event
of repairs, such as the replacement of moulds, plungers, plunger rails, etc.
It is not feasible to group all sizes of moulds so as to permit of machine
moulding, large altar candles, for instance, being preferably mouldeo
singly, otherwise the machines would be too gigantic. Machines of
this kind have been constructed, but are so large as to extend through
nearly two stories in the factory.

Special attention should be bestowed on thorough cooling. It has
been found that, with protracted cooling, candle material rich in stearine
is liable to segregation, the portions cooling first containing more
stearine than the rest. Moreover, when proper cooling is provided,
the candles are more easily ejected from the moulds, the finish being
then higher and the requisite motive power less. Many works suffer
considerably from the great difficulty experienced in procuring sufficient
cooling water; and for this reason, refrigerating machinery has been
successfully installed for artificially cooling the water. Otherwise it is
necessary, in the summer months, to increase the proportion of stearine,
as the paraffin candles stick obstinately in the machine — and this, of
course, means increased cost of production, owing to the difference in
price between the two materials. If even this remedy fails, the candles
must either be tapped individually with a wooden mallet, to loosen
them in the moulds, or else, if this does not answer, they must be
melted out by admitt ng steam to the jackets. In this latter event, the
next batch will be wasted, since the wicks will be out of centre. An

136

SHALE OILS AND TAES

important point in facilitating the ejection of the candles from the
moulds is the careful regulation of the pouring temperature, which
should be between 65° and 75° C. (150° to 165° R). In some works,
one special tally mould (making a candle with some special mark, such
as a ring at the base) is provided on each machine. Each tally re-
presents a pouring, and the total number handed in at the close of the
day's work shows how many candles have been made, the payment
being based on piece-work.

Various shapes of candle are made, some being plain, others
fluted ; and in addition there is the self-fitting pattern, with a taper
base enabling the candle to fit better into the holder. This type of
candle is more popular in England than in Germany. Sizes are still
more varied than shapes, ranging from 2 Ib. each to about 150 to the
Ib. ; but very small sizes are made by cutting longer candles into short
lengths.

(b) Finishing.— On leaving the machine the candles are not ready
for sending out, but have to be finished. In the first place the base is
butted, i.e. trimmed off level with a knife. This is necessary because, in
ejecting the candles from the machine, the wicks are forced out of
centre at the base while the candles are still soft, thus spoiling the
appearance. This lowest extremity has to be trimmed off, a larger
quantity being sometimes removed at the same time, namely when a
definite weight of candle is 'required and no suitable moulds for pro-
ducing it are available. Sometimes as much as half the candle has
to be cut away, which of course is very wasteful, both in labour and
material, since the colour of the latter is always impaired by remelting.
The butting process is effected by hand or machine. The candles are
placed in a kind of trough, the lower end of which is provided with
an adjustable board, set according to the length of candle desired ; and
all the ends projecting from the trough are then cut off by a sharp
knife with a sliding cut. Endeavours have been made to perform the
butting process in the moulding machine, by pushing up the plungers
so that the portion of candle to be removed protrudes from the top
edge of the mould. Numerous devices and cutters have been tried for
this purpose, but without any complete practical success, the cutters
always breaking small pieces out of the. edge of the candles, owing to
the cut not being sufficiently oblique. Thick candles are tapered a
little by trimming them at the base, so that they will fit in the holders,
better. This is done with a high-speed rotary cutter, similar to a
pencil-sharpening machine, and either driven by an engine or coupled
direct to the shaft of an electromotor. As a rule, paraffin and com-
posite candles do not require polishing to increase their gloss ; but in
many works stearine candles are polished by passing them through
mechanically operated woollen cloths. Candles are sometimes, though
rarely provided with a stamped impression, to indicate that they be-
long to a certain owner, and thus prevent theft. Such impression is
produced by pressing the candle against a steam-heater! brass block,
bearing the name either engraved or in relief. Under this treatment a

CANDLEMAKING- 137

certain quantity of the candle material is melted away, and the weight
is reduced in comparison with the unstamped candles.

(c) Packing the Candles. — The next stage is packing in cardboard
cases, of which there are three sizes, weighing respectively about 9,
13J, and 18 oz. gross, to contain -J, f, and 1 Ib. net. The candles are
wrapped in tissue paper and placed in the boxes, which are labelled
with pictures (for Christmas candles, etc.), some fancy name for the
candles, or the name of the maker or retailer. In some cases the
candles are put direct into wooden cases without any wrapper. The
cardboard boxes are either made by female labour or purchased ready
made.

The wooden cases are frequently made in the works by mechanical
appliances, including circular saws and nailing machines, and printing
machines for impressing the quality marks on the box ends. For over-
sea transport or long distances inland, the contents of the cases are
first wrapped in oiled cloth, the outside of the case being strengthened
with hoop iron.

(d) Working up Candle Waste. — In most candle works there is a
department for working up the manufacturing waste, such as candle
material that has been spilled on the floor or left in the storage and
melting vessels ; material that has beei% kept too long, etc. These
are treated separately from the butt trimmings and the cleanings from
the trough of the candle machine, both of which are simply melted
down and used again, being nearly as colourless and good as the pure
material. The other scraps first named are melted down and boiled
with a little acid, the mechanical impurities they contain settling
down more readily in consequence of this treatment. The treated
mass is brownish in colour, due to dirt, colouring matters nnd salts of
iron resulting from the contact of the candle material with the iron
fittings of the machines or iron floor plates in the works. Next follows
boiling with caustic soda, which , removes the stearine, the resulting
soap carrying with it most of the colouring ingredients, whilst the
majority of the organic dye-stuffs are destroyed by this treatment. The
residue, consisting of pure paraffin, has always a yellowish cast, mainly
because the very permanent quinolin yellow has not been eliminated ;
but after being treated with animal charcoal, in the same manner as
crude paraffin, it is sufficiently decolorized to be used over again for
candlemaking. The stearine soap from the soda treatment is decom-
posed with sulphuric acid and deposits a brown stearine, containing a
little paraffin and suitable for many purposes of the chemical industry.
The quantity is not very large, being only about 0*1 per cent of the
weight of candles produced, so that its disposal does not present any
difficulties.

CHAPTEK X.

CHEMICAL COMPOSITION OF THE TARS AND THEIR DISTILLATES.

A. LIGNITE TAR.

LIGNITE tar is formed during the dry distillation of lignite, various
constituents of the latter being concerned in the process of formation,
such as the cellulose left during the incomplete carbonization of the
coal, the humic acids and the bitumen or mineral wax. All three
components have been investigated in connection with the part they
play in the formation of the tar ; and it has been found that the most
valuable constituents of the tar, namely the paraffin and other satu-
rated hydrocarbons, are mainly furnished by the mineral wax. Acid
bodies of phenol character are chiefly formed from the products of the
transformation of cellulose to coal, whilst the humic acids furnish sub-
stances of varying characteristics, chief among which, apparently, are
the so-called neutral bodies. Whether and to what extent the ash
constituents of the lignite have any effect on the quality of the tar has
not yet been decided, though from the results of laboratory experiments it
may be regarded as probable that the alkaline earth constituents (salts ?)
of the ash abstract carbon dioxide from the acids of the mineral wax and
the humic acids. Thus, for example, when pure mineral wax is distilled
by itself it furnishes an entirely different product from that obtained by
distilling the same wax in presence of a little lime. In the former case
the distillate still contains an appreciable quantity of acid products,
and gelatinizes to a stiff pulp when treated with alkalis ; whereas the
distillate obtained when lime is used remains liquid and is almost en-
tirely free from acid products.

A subordinate part is played by the nitrogenous constituents in the
tar, which only contains about -J to -J per cent of same. It would be
an advantage if the small amount of nitrogen (about O3 per cent) in
lignite could be more completely utilized for the production of techni-
cally valuable products, such as ammonia, or pyridin bases for instance.
According to the researches of Wohman, only about 10 per cent of the
nitrogen contained in lignite is at present found again in the tar, an-
other 12 per cent being in the tar water, 66 per cent in the coke, and
12 per cent in the gas.

(138)

COMPOSITION OF THE TABS AND THEIE DISTILLATES 139

The percentage proportion of these distillation products in lignite
tar depends both on the kind of coal and the method of carrying out
the distillation. The higher the retort temperature, the richer will the
tar be in carbon and the poorer in hydrogen, that is to say the richer
in unsaturated hydrocarbons and aromatic compounds, and the greater
the proportion passing away in the gases.

So far as the saturated hydrocarbons are concerned, the products
of distillation contain an unbroken series of them, from methane up
to the highest members of the methane series, containing thirty and
more carbon atoms in the molecule. The lower members of the
series are chiefly found in the retort gas, and the higher ones — about
from hexane onward — in the tar. By subjecting the retort gas to very
low temperatures, the vaporous hydrocarbons — commencing approxi-
mately with propane — can be condensed, and then isolated, to some
extent, by fractional vaporization. To obtain the saturated hydro-
carbons of lignite tar, the basic constituents are first eliminated by
agitation with dilute acid, the phenols being next removed by the aid
of alkali, and finally the unsaturated compounds by repeated agitation
with concentrated sulphuric acid. This latter treatment, however, is
not altogether free from objection, because, on the one hand, a certain
portion of the unsaturated compounds an<j also of the aromatic hydro-
carbons escape the reaction, whilst on the other hand, the saturated
hydrocarbons are attacked in the warm. This is evident from the fact
that sulphur dioxide is liberated, which product can only arise through
the oxidation of hydrogen, the temperature being insufficient for the
oxidation of carbon, and there being no corresponding liberation of
carbon dioxide. The acid treatment is followed by a thorough washing
with water and dilute carbonate of soda solution, the residual liquid
being warmed along with picric acid to remove the greater portion of
the aromatic hydrocarbons which escaped the sulphuric acid treatment.
The lower members of the remaining hydrocarbons form a colourless
liquid of not unpleasant smell, whilst the higher members form a
transparent white mass, known under the generic name of paraffin, and
consisting in reality of a mixture of various paraffins. The solid par-
affin comprises the hydrocarbons containing seventeen to thirty-two
atoms of carbon. The unsaturated hydrocarbons in lignite tar belong to
various series, including the ethylene and acetylene series, and probably
others still poorer in hydrogen. Up to the present no one has suc-
ceeded in isolating these bodies in a pure state. It is, however, pos-
sible to recover the products obtained on agitating the tar distillates
with sulphuric acid, by diluting the spent acid with water and boiling
it repeatedly. This treatment gives a black liquid, smelling of pepper-
mint and capable of being refined by iractionation ; but it must not be
assumed that we have here to deal with the unsaturated hydrocarbons
in the original form in which they were present in the lignite tar, since
both oxidation and polymerization have been set up by the sulphuric
acid. At all events, the hydrocarbons recovered in this way are jn the

140 SHALE OILS AND TABS

highest degree unsaturated, this being indicated by their energetic re-
action with sulphuric acid, their high iodine value (extending above
100) and their powerful reaction with potassium permanganate, in
presence of which substance they become strongly heated, the mass
even spurting out of the test vessel. The oxidation is accompanied by
the formation of acids which, however, have not yet been more closely
investigated. When liberated by treating their salts with an acid,
they give off a repulsive smell, recalling capronic, caprylic, or capric
acid.

The refined paraffin itself is not entirely free from unsaturated
hydrocarbons, as is evident from the fact that it always exhibits an
iodine value, though but a low one (about 2 to 5 according to the de-
gree to which the paraffin has been refined). As a rule a tar will be
so much the better in quality in proportion as the content of unsatur-
ated hydrocarbons is lower ; and for some purposes their presence is
injurious. Thus, for example, the lignite-tar oils that are rich in un-
saturated compounds and poor in hydrogen, burn with a much smokier
flame than the petroleum oils which are rich in hydrogen ; and at the
same time they require a particularly abundant supply of air to the
burner.

The unsaturated hydrocarbons are also of little value in the pro-
duction of oil gas, since they, furnish much tar and little gas ; and also
on account of their low hydrogen content. They are less troublesome
for use in motors, the only drawback being that their low hydrogen
content lessens the calorific power of the oil. Whether they are in-
jurious in paraffin has not yet been ascertained ; and it is even open to
surmise that the high stability of the lignite-tar paraffins in comparison
with the petroleum paraffins is due in part to the unsaturated hydro-
carbons. As shown by the experiments of Sabatier and Senderens,
and more recently Erdmann, the unsaturated hydrocarbons can be
constrained to "combine with hydrogen and become saturated. This
transformation is accomplished by passing the vaporized hydrocarbons,
in association with hydrogen, over a contact substance, e.g. finely
divided nickel. It would be highly useful if this method could be em-
ployed to improve the lignite-tar products on a technical scale ; but
the prospects of success do not appear very high at present, chiefly be-
cause the sulphur products — which will be referred to later — invalidate
the activity of the contact substance within a short time.

Aromatic hydrocarbons also are present in lignite tar. They origin-
ate chiefly in secondary decompositions of hydrocarbons of the fatty
series through contact with the hot lining and iron fittings of the re-
torts. The amount of these, however, is relatively small, the chief re-
presentative being naphthalene, which is principally found in the most
volatile fractions of the lignite tar, e.g. the solar oil, in which it occurs
to the extent of about 1 to 2 per cent. It is isolated by warming the
oil along with picric acid, and allowing the resulting picrate to crys-
tallize out in the cold. The crystals are aspirated, and washed with

COMPOSITION OF THE TABS AND THEIK DISTILLATES 141

volatile benzine (from petroleum) the dried precipitate being transferred
to a flask and heated to boiling along with a little dilute caustic soda,
whereupon the naphthalene distils over and deposits in the condenser
tube. The naphthalene, although it does not affect the burning of the
oil, makes itself unpleasantly apparent in many of the uses to which
the oil is put. Thus, in employing lignite-tar oil for washing hydro-
chloric acid gas in order to eliminate the compounds of chlorine with
arsenic, it has been found that the apparatus occasionally becomes
choked up with hexachlorbenzol, formed by the chlorination and de-
composition of the naphthalene, the chloride of arsenic apparently
acting as a carrier of chlorine. Other aromatic hydrocarbons, such as
benzol derivatives, have only been discovered in small proportions in
lignite tar. Larger quantities of complex aromatic hydrocarbons are
formed towards the end of the tar-distilling process. Solid red-brown
masses are deposited in the condenser worm, these consisting chiefly
of picene and chrysene. It must, however, be assumed that these sub-
stances were not originally present in the tar, but have been formed by
the decomposition of the tar vapours through contact with the heated
sides of the retort. The picene can be recovered in a comparatively
pure state by washing the crude picene with benzine and then recrys-
tallizing it from pyridin or cumol. It^eparates out in the form of
white crystals melting at about 340° C. Up to the present no use has
been found for this substance. . ...

In addition to the true aromatic hydrocarbons, the tar contains
hydromatic hydrocarbons, similar to the naphthenes obtained from
Russian petroleum ; but the quantity is small. One series of aro-
matic hydrocarbons is present to a large extent (10 to 15 per cent)
in lignite tar,, namely the phenols, which, however, are undesirable
since they have to be got rid of at considerable expense for chemicals
(caustic soda). They are of high specific gravity and on this account
their presence in tars rich in creosote is easily detected. To effect
their isolation the tar or tar distillate is agitated with dilute caustic
soda, the solution being drawn off and extracted repeatedly with
benzine or ether until the solvent drains away almost colourless.
The object of this treatment is to remove the so-called neutral oils
(see later) which are partially soluble in the soda tar. The purified
soda tar is next decomposed with dilute sulphuric or hydrochloric
acid, the deposited creosotes being drawn off, dried by heating above
100° C., and then fractionated. They consist mainly of creosotes. The
initial member of the phenol series, viz. carbolic acid, is only present
to a small extent in the tar, from which it was isolated by Eosenthal.
The recovered creosotes are impure, containing still a considerable
proportion of sulphuric-acid compounds of an acid character. Whether
the sulphur here takes the place of oxygen, or in what way it enters
the molecule, has not yet been ascertained. In any event the content
of sulphur compounds cannot be small, since the sulphur content alone
is about 1 to 2 per cent, indicating from 5 to 10 per cent of such

142 SHALE OILS AND TABS

compounds. Moreover, the sulphur cannot be eliminated by treating
the creosote with reagents ordinarily capable of dissociating sulphur
from combination, the creosotes being still found to contain sulphur
after repeated distillations over litharge. These sulphur compounds
are probably the cause of the disagreeable smell which has hitherto
prevented the lignite-tar creosotes from being used for medicinal
purposes. When freshly distilled, the creosotes form a colourless, highly
refractive oil, but they soon become dark coloured on exposure to the
air. They seem also to contain polyvalent phenols, derivatives of
which, guaiacol for instance, have already been identified therein.
The occurrence of phenols is also probable, since they have like-
wise been isolated from the tar water. Thus, pyrocatechin can be
obtained by treating the tar water — especially when concentrated —
with lead acetate ; and Rosenthal has recovered large quantities in this
way. The origin of the creosotes of high boiling-point (up to 400° C.)
in this tar has not yet been ascertained. When freshly distilled, they
form dark-brown viscous oils.

As already mentioned, a portion of the nitrogen in the tar is dis-
tilled over, some of it also appearing as ammonia in the tar water.
The nitrogenous constituents of the tar consist chiefly of pyridin and
its homologues. Pyridin is readily soluble in water, and ifc therefore
appears both in the tar water and in the tar, the amount of pyridin
bases in the latter being about J per cent. These bases were formerly
recovered in practice, and were employed for purifying anthracene and
denaturing spirit. The regulations in respect of such denaturing bases
have, however, been made more stringent, almost complete volatility
at 140° C., and solubility in water, being insisted upon ; but since the
bases recovered from lignite tar have a higher boiling-point, and are
only partially soluble in water, their recover}^ has been abandoned, and
they are allowed to escape, as sulphates, in the effluent.

Quinolin has also been isolated from the -tar, together with aniline,
but in merely insignificant quantities. Nitriles are also present, and
are revealed by the circumstance that when many of the oils are dis-
tilled over caustic soda, ammonia is given off from the decomposition
of nitriles, in spite of the oils having been previously acidified so that
no free ammonia can be present.

Larger quantities of bases are found in other distillation tars, for
example in those of the Scottish industry, which are obtained from the
more nitrogenous shales. These bases also belong, for the most part,
to the lower members of the pyridin series, and pass into the ammonia
liquor in consequence of their solubility in water. These pyridin bases
are to be recovered on a manufacturing scale in the industry in ques-
tion.

The sulphur compounds play an important, though undesired, part
in lignite tar. They originate in the organic sulphur compounds in
the lignite, both the mineral wax, the humic acids, and the cellulose
.substance containing sulphur. The double sulphide of iron (Markasite)

COMPOSITION OF THE TABS AND THEIR DISTILLATES 143

frequently present in coal is not to blame for this sulphur, since even
coal with ash practically free from iron will yield tars containing
sulphur. The proportion of sulphur in the tar is about £ to 1^ per
cent, and in spite of the numerous methods proposed, it has not yet
been found practical to eliminate it in practice. Thus, treating the tar
with concentrated (and even fuming) sulphuric acid, aluminium
chloride, copper sulphate, and sodium has been proposed, but none of
these methods has found practical application.

The quantity of the sulphur compounds cannot be small, since the
sulphur forms only a fraction in the molecule of such compounds and
amounts to at least 5 per cent. Only a few such compounds have
been actually isolated.

The best known of the sulphur compounds is sulphuretted hydro-
gen, the presence of which is apparent both in the retort gases and in
those from the distillation of the tar. Carbon disulphide is found in
the first runnings of the tar, but the amount is only small, as is
also that of the thiophene, the presence of which was detected by
Brdmann. On agitation with mercuric chloride solution, the tar oils
give a white precipitate, indicating the presence of mercaptans, to
which is no doubt due the bad smell of the lignite tar and its distilla-
tion products.

On agitating the tar with concentrated caustic soda, as is practised
for removing the creosotes, another class of substances pass into solu-
tion, namely the so-called neutral oils, the nature of which is still un-
known. They are isolated by allowing the soda tar (obtained by acting
on the tar oils, with caustic soda of 38° density) to stand for several
days, the deposited oil being syphoned off so long as it continues to
settle down. The soda tar is then diluted with a large quantity of
water, whereupon it separates into two layers : an upper one of oil,
and a lower one consisting of dissolved creosote tar. The oil is re-
moved, agitated several times with dilute soda lye, and then fractionated.
This treatment furnishes a strongly refractive oil, of high specific
gravity, peculiar smell, and darkening quickly in the air. The oil con-
tains oxygen and also sulphur, but is not soluble in alkali and therefore
cannot be an acid or a phenol. It reacts powerfully with oxidizing
agents, especially permanganate, with formation of acids the nature of
which has already been described. Possibly we have here to do with
ketones, but up to the present this product has not been closely in-
vestigated. The presence of oxygen is indicated by the low calorific
value of the oil, which is below 10,000 cal.

According to Erdmann,1 the following substances are contained in
lignite tar : —

1 " Die Chemie der Braunkohle " (" Chemistry of Lignite "), pp. 92 et seq.

144

SHALE OILS AND TABS

CONSTITUENTS OF LIGNITE TAR.
1. Hydrocarbons of the Paraffin Series.

Formula.

Melting-point

°C.

Boiling-point
(760 mm.).

Heptane * . . . ; .

C7H16

98°

Normal Nonane2 . » •

—51°

149,5°

Normal Decane3

C10Ha2

—30 to 32°

173°

Undecane 3 . . . .

CnH<,4

—26,5°

194,5°

Heptadecane4 . '.,•'. . ' .

C17H36

22,5°

303°

Octadecane4 . . .. - . . '

^18^38

28°

307°

Nonadecane4 . . . . ,

C19H4b

32°

330°

at 15 mm.

Eicosane4 . . . .:

C20H42

36,7°

205°

Heneicosane4 . . .

C21H44

40,4°

215°

Docosane4 . " .

^22^46

44,4°

224,5°

Tricosane4

47,7°

234°

2. Hydrocarbons of tlie Ethylene Series.
Decylene5 .... . . . J C10H20 |

3. Aromatic Hydrocarbons.

Benzol6 * .
Toluol7

C6H6
C6H,(CH3)
C6H4(CH3)2
C6H3(CH3)3
Ci0H8
C18H12
C22H14

L'16±118

in Small Qua

6,4°
—93°
—54 to— 53°

80°
250°
350°
117°

ntity.14

80,4°
111°
139,2°
163°
218°
448°
518 bis 520*
300 bis 303°

m-Xylol 8 .

Mesitylene 9
Naphthalene10. . . ...
Chrysene u
Picene12

Hydrocarbon 13
4. Naphthenes

1 Rosenthal, " Zeitschr. f. angew. Chemie," 1893, 109.

"Heusler, "Berichte d. Deutsch. chem. Ges.," 25, 1665 [1892]; Oehler,
" Zeitschr. f. angew. Chemie," 1899, 561.

3 Oehler " Zeitschr. f. angew. Chemie," 1899, 561.

4 Krafft, " Berichte," 21, 2256 [1888] ; 29, 1323 [1896].
5Heusler, "Berichte," 28, 500 [1895].

6Heusler, "Berichte," 25, 1672 [1892]; Rosenthal, "Zeitschr. f. angew.
Chemie," 1893, 108 ; Krey, ibid. 109.

7 Heusler, " Berichte," 25, 1673 [1892] ; Oehler, " Zeitschr. f. angew. Chemie,"
1899, 561.

8 Heusler, " Berichte," 25, 1674 [1892] ; Oehler, " Zeitschr. f. angew. Chemie,"
1899, 561.

9 Heusler, " Berichte," 25, 1674.

1(> Heusler, " Berichte," 25, 1677 ; Oehler, " Zeitschr. f. angew. Chemie," 1899,.

562.

11 Adler, " Berichte," 12, 1889 [1879].

12 Burg, "Berichte," 13, 1834 [1880]; Boyen, " Chem.-Ztg.," 1889, 29, 64, 93..

13 Oehler, " Zeitschr. f. angew. Chemie," 1899, 563.

14 Heusler, " Berichte," 28, 488 [1895].

COMPOSITION OF THE TABS AND THEIR DISTILLATES 145

5. Bases.

Formula.

Boiling-
point. V

Pyridin1

C5H5N
C5H4(CH3)N

114,5° I
129°

£-Picolin3
rPicolin4
6-Dimethylpyridin 5 (Lutidin)
3^ 4-Dimethylpyridin6 . . . : r". '
2, 4-Dimethylpyridin 7 . . . / .
2, 5-Dimethylpyridin 7 . . . ~ ,
2, 4, '7-Trimethylpyridin 8 (Collidin) . . f'
•Quinolin9 . . . ... . .
Anilin10 . •- . '. .'.' . ". '... •.

C5H4(CH3)N
C5H4(CH3)N
C5H3(CH3)2N
C5H3(CH3)2N
C5H3(CH3)2N
C5H3(CH3)2N
C5H2(CH3)3N
CqH7N
CfiH-(NH2)

143 to 144°
ca. 145°
142 to 144°
162 to 164°,
150°
154°
170 to 171°
238°
184,5°

Nitriles11 .

6. Oxygen Compounds.

Phenol i3
o-Cresol14
m-Cresol14
p-Cresol14
Guaiacol 15
•Creosol 16

Carbon disulphide 17 .
Thiophene18 . ; ' >.'

ss of Acetone12 ....

C6H5(OH)
C6H4(CH3)OH
CfiH4 CH^OH

180 to 180, 5°
190,8°
202,8°

C6H4(CH3)OH

201,8°

OH C6H4 . OCH3

205,1°

CH»0 . CRH,(CHS)OH

221 to 222°

7. Sulphur Compounds.

CS2
C4H4S

46°

84°

1 Bosenthal, " Jahresbericht des Techniker-Vereins der sachs.-thiir. Miner-
.alolindustrie," 1890-91, 7 ; " Chem.-Ztg.," 14, 870.

2 Krey, " Berichte," 28, 106 [1895] ; Frese, " Zeitschr. f. angew. Chemie,"
1903, 12 ; Rosenthal, Ibid., 1903, 221 ; Ihlder, Ibid., 1904, 524.

:j Krey, " Berichte," 28, 106 ; Ihlder, " Braunkohle," 3, 59, [1904].

4 Ihlder, " Braunkohle," 3, 60 [1904].

5 Ihlder, " Braunkohle " 3, 59 [1904].

8 Ihlder, " Zeitschr. f. angew. Chemie," 1904, 1670.

7 Ihlder, "Braunkohle," 3, 60 [1904]; "Zeitschr. f. angew. Chemie," 1904,
524.

8 Krey, "Berichte," 28, 106 [1895]; Ihlder, "Braunkohle," 3, 61 [1904];
" Zeitschr. f. angew. Chemie," 1904, 525.

9 Dobner, " Berichte," 28, 106 [1895].

10 Oehler, " Zeitschr. f. angew. Chemie," 1899, 562.

11 Heusler, " Berichte," 28, 488 [1895].

12 Heusler, " Berichte," 28, 496 [1895].

13 Rosenthal, " Jahresbericht des Techniker-Vereins der sachs.-thiir. Miner-
.alolindustrie," 1890-91, 6 ; " Zeitschr. f. angew. Chemie," 1892, 402.

14 Riehm, Ger. Pat. Nr. 53,307.

15 Vehrigs, see Scheithauer, "Fabrikation der Mineralole," 1895, 222.

16 v. Boyen, " Chem.-Ztg.," 1889, 357.

17 Rosenthal, " Zeitschr. f. angew. Chemie," 1893, 109.

18 Heusler, " Berichte," 28, 493 [1895].

146 SHALE OILS AND TABS

B. SHALE TAR (CRUDE OIL).

Scottish shale tar is of approximately the same composition as
lignite tar, except that — as already mentioned — its content of nitro-
genous bodies is higher. The tar consists of saturated and unsatur-
ated hydrocarbons, and also contains aromatic compounds and small
quantities of naphthenes.

Aromatic hydrocarbons 1 were seldom present in the tars produced
in the old retorts used in the 'seventies, the retort temperature being
low. On the other hand the tars from the modern retorts, in which
decompositions are set up by the high temperatures used, always con-
tain benzols. Thus, for example, Broxburn naphtha (sp. gr. 0*735)
has been found to contain, in the fraction boiling between 130° and
165° F., 2'6 per cent of benzol; and in that boiling between 212°
and 221° F., 2'5 per cent, of toluol. Naphthalene, methyl-tetra-
methylene, pentamethylene, and hexamethylene have been obtained
in varying quantities from the corresponding tar fractions.2 Picene and
chrysene have also been detected.3 Phenols and cresols are likewise
constituents of shale.4

In addition, pyridin and quinolin bases are present. Eobinson and
Goodwin5 have identified the quinolin bases, and Garret and Smythe 6
the members of the pyridin series. Naphtha contains 1£ per cent of
pyridin bases. Sulphur compounds, detected by their odour of garlic,
are also present in shale tar.

F. Heusler7 found, in the fractions below 131° F., from Scottish
shale tar : 42 per cent of paraffin, 10 per cent of naphthalene, 7' 3 per
cent of aromatic hydrocarbons, and 39 per cent of olefmes.

1 " The Oil Shales of the Lothians," p. 184.
2B. Steuart, " J. Soc. Chem. Ind.," 19, 986.
3 " The Oil Shales of the Lothians," p. 183.

4T. Gray investigated the phenols in naphtha, " Journ. Soc. Chem. Ind.," 21,.
845.

5 Trans. Roy. Soc. Edin., 28, 561 ; 29, 265 and 273.

6 Trans. Chern. Soc., 1902, 1903.

7 " The Oil Shales of the Lothians," p. 185.

CHAPTEE XI.
THE LABORATORY WORK.

BEFORE the economic situation rendered the intensive utilization of
all the products compulsory, laboratory work in the distillation- tar
industry was neglected ; but at the present time it has grown into an
essential feature.

Almost every works in which distillation tars are treated, is fitted
with a well-equipped laboratory which has to discharge a variety
of functions. One of its tasks is to improve the quality and quantity
of the tar by selecting suitable raw material ; another being to check
the intermediate and final products made in the works, so as to ensure
uniform quality and satisfy the requirenients of customers. Finally,
by selecting the reagents to be purchased, the buying department is
assisted.

An essential portion of the laboratory work is to devise new pro-
cesses, since competition obliges the manufacturer to simplify his-
methods of working either by saving expense in labour and material
or by improving the final products. In this connection, of course, no
definite rules can be laid down, since the problems to be solved are
not uniform in character, and the whole work lies more within the
sphere of invention. In the main, however, the problems to be solved
are : —

Increasing the yield of tar by protecting the bitumen during the
distillation process.

Simplifying the treatment of the tar, avoiding the use of expensive
chemicals wherever possible.

Refining the paraffin cheaply and at the same time improving the
quality.

It is easier to lay down instructions for the work of the laboratory,
in which the operations are practically the same, day after day. For
the most part the checking of the raw materials and final products
is in the hands of skilled laboratory assistants, of course under the
supervision of a chemist.

TESTING THE RAW MATERIALS.

The first point to be considered is the testing of the raw materials :
the bituminous lignite and the fire coal. Perhaps even more import-
ant than the actual testing is the sampling, it being particularly difn-

(147)

148

SHALE OILS AND TAES

cult to obtain a true representative sample in view of the fluctuating
composition of the material, and the large quantities involved. The
best method is to take a shovelful from the middle and side of a track
load when being unloaded, this being repeated with as many trucks
as possible, and the samples thus obtained mixed together. The 1
to 2 cwt. of sample material is crushed small, arranged in a square
heap, and divided into quarters by two diagonal lines (see Fig. 63).
Two of the opposite triangular portions are
then mixed together, arranged in a square and
quartered as before and the series of operations
being repeated until there are only 100 to 200
grm. of the sample left. This is packed in a
tightly closed tin and sent to the laboratory.
Glass jars or tins may be used; but .there is
no need to solder the latter up, especially if
the laboratory is not very far away. If one
FIG. 63. wishes to be extra cautious a strip of rubber

or the like may be secured round the edge of the cover.

In the laboratory the sample is reduced to powder and tested to
determine the water and ash content, behaviour under dry distillation,
the calorific value, distillation products, and percentage of bitumen.
Any one or more of these may of course be omitted, according to local
circumstances.

The percentage of water is determined by heating 10 grm. of the
•sample in a drying oven, at a temperature of 105° to 110° C. until the
weight is constant. For very accurate determinations this drying
should be performed in vacuo or in a current of inert gas, e.g. carbon
dioxide, since lignite oxidises readily in the air and gives off carbon
dioxide in addition to absorbing oxygen.

The most important estimation in the case of the bituminous lignite
is the yield of tar. The apparatus used for this purpose is sketched
in Fig. 64, and consists of a retort holding about 200 c.c. and a glass

receiver into which the neck
of the retort fits by means
of a cork traversed by a
small tube for the escape of
the gases liberated during
distillation. The retort must
be of refractory glass or it
would fuse at the high tem-
perature used ; and it is
preferably sheltered from
external cooling influences

FIG. 64. — Apparatus for estimating the yield

of tar from bituminous lignite.
(G = Gas effluent. K = Cork. V = Receiver.)

by a jacket and cover of
sheet metal or asbestos. The
receiver is immersed in water

to cause the fullest possible condensation of the tar vapours, a very small
loss making a considerable difference in view of the minute quantities

THE LABORATORY WOEK. 149

used. About 20 to 50 grm. of the bituminous lignite in its natural con-
dition of moisture are placed in the retort, the neck of the vessel being
carefully cleaned out after charging. The retort is heated up by a small,
smoky flame at the start, the heat being increased after half an hour ;
and after maintaining the maximum of heat for one hour, the flame is
finally lowered again. The whole treatment lasts four to six hours,
more rapid working being undesirable since it lessens the yield of tar
and increases the losses due to the production of gas.

Eetort and receiver are weighed before the distillation, to ascer-
tain : —

Weight of empty retort,

„ „ retort charged with lignite,
„ „ empty receiver,
„ ,, receiver after distillation,
„ retorts „ „

When distillation is completed the contents of the receiver will be
found to consist of two 'strata — water and tar. Should any tar remain
in the neck of the retort, it is rendered fluid by warming it with the
lamp, and is transferred to the receiver. It being difficult to separate
the drops of tar from the water, the following method is pursued :
after the receiver and contents have beep weighed it is filled nearly
to the top with hot water, which causes the tar to melt and run to-
gether ; whereupon the whole is placed in a vessel with cold water or
ice, thus causing the liquid tar to solidify as a cake. This cake is taken
out, dried with filter paper and weighed.

The difference between the tars of the retort and the weight of the
retort after distillation, gives the yield of coke. The amount of the
tar water is found by subtracting the weight of the cake of tar and
that of the empty receiver from the weight of the receiver after the
distillation. Finally, any difference remaining between the original
weight of substance and the sum of the coke, tar, and tar water, re-
presents the loss by gasification. The values obtained by analysis can-
not* be directly applied to work conducted on the large scale, owing to
the far higher losses by decomposition sustained in the latter case, the
retorts being far more leaky than a glass still and allowing tar vapours
to escape outwards and air inwards. In both contingencies there is a
loss, due to the combustion of the tar vapours, amounting to 30 to 4:0
per cent, so that only about 60 to 70 per cent of the tar is actually re-
covered in practice.

( If for any reason dry lignite comes forward for distillation, the
results obtained must be referred to the same material in the condition
of moisture in which it leaves the pit, namely with a content of about
50 to 55 per cent of moisture.

Seeing that the practical yield differs from that in the laboratory
by reason of the greater losses sustained in the former case, there is no
object in subjecting the tar recovered in the glass receiver to analysis
—which would, moreover, be difficult in view of the small quantity
available.

150

SHALE OILS AND TABS

If it be desired to test the tar as well, a larger trial distillation must
foe performed with the raw material (lignite or shale) so as to obtain
:at least 100 grm. of tar. Even this tar, however, is not comparable
with that produced in the works, though more nearly approximating
thereto than is the tar obtained in glass retorts.

The tar water may also be examined, this being advisable when
one is employing some new material in which a high percentage of
nitrogen is suspected. The water is tested to see whether it has an
acid or alkaline reaction. Geologically recent materials like peat and
some lignites yield acid tar waters in consequence of decomposition of
the cellulose ; whereas older materials, old lignite (brown coal),
coal and bituminous shale yield alkaline tar waters. The test is of
course merely qualitative. If it be desired to ascertain the percentage
of nitrogen precisely, in order to form an opinion on the probable yield
of ammonsa, the nitrogen determination must be performed directly
with the raw material, preferably by the Kjeldahl method.

Information on the quality of bituminous lignite is also afforded by
the determination of the bitumen content ; sines the higher the per-
centage of bitumen, the better the yield and quality of the tar, as a
rule. The term bitumen here applies to the substances that can be ex-
tracted from lignite by solvents. What is
stated here in respect of lignite is not, how-
ever, unconditionally applicable to bitumi-
nous shales, since Scottish shale though
yielding 20 to 50 per cent of tar does not
contain any constituents that will dissolve
in organic solvents.

The determination of bitumen in lignite
is preferably effected with dry material,
since the solvents — benzol especially — used
for extraction will permeate the dry material
more easily. Any extraction apparatus
may be used, such as that of Soxhlet, or
the one constructed by Grafe (Fig. 65).
Ten grm. of the dried substance are placed
in a filter paper cylinder and covered with
cotton wool, the reflux condenser being
arranged so that the condensed solvent
trickles down through the cartridge. The
extraction flask is charged with 100 to 200
c.c. of benzol, a few small stones or irag-
ments of earthenware being put in to pre-
vent bumping while boiling The benzol
is then raised to boiling point and retained
at that temperature for two hours, where-
upon the contents of the flask — now stained
brown by the dissolved bitumen — are poured into a weighed dish, which
is heated on the water bath to expel the solvent. The final traces are
very difficult to eliminate, and it is therefore advisable to heat the

FIG. 65. — Grafe's extraction
apparatus for the deter-
mination of bitumen in
lignite.

(B = Reflux condenser.)

THE LABORATORY WORK 151

dish up to about 150° C. over the bare flame previous to weighing,
the dish and contents being weighed after cooling. Good lignite
contains about 10 to 20 per cent of bitumen, referred to the dry sub-
stance. The determination of bitumen is particularly important in
the case of lignites intended for the extraction of that substance, a
process that is now being carried on in a number of works specially
erected for the purpose. The bitumen is a blackish brown, brittle
mass melting at 80° to 85° C. (176° to 185° R), and extensively used
for the manufacture of phonograph cylinders and shoe polishes. The
testing of bitumen will be dealt with later.

TESTING THE TABS AND OTHER DISTILLATION PRODUCTS.

The chief object in testing the tar is to ascertain how much paraffin
it contains, this latter being the most valuable constituent. An ap-
proximate idea can be gathered from the specific gravity and the
solidification point. As a rule, the lighter the tar the higher the
paraffin content, and vice versa. The specific gravity, however, is in-
creased not only by relative absence of paraffin, but also by the pre-
sence of creosote — a constituent of low value and difficult to get rid of.
In this respect also, specifically light tars are to be preferred.

The specific gravity determinations must be effected in the warm,
the tar being solid at the ordinary temperature. The tars now
treated have the specific gravity 0'880 to 0-900, though these limits are
occasionally exceeded to a slight extent in either direction. As already
mentioned, a high solidification point of the tar is a sign that it is rich
in paraffin ; but the indication is not infallible, many producer tars,
for instance, containing still undecomposed bitumen and consequently
exhibiting a high specific gravity though their paraffin content is low.
Good lignite tar solidifies at 20° to 30° C. (68° to 86° R).

The only way to obtain a correct view of the quality of a tar is
by distillation, followed by the chemical examination of the products.
About 300 grm. of tar are distilled in a glass flask or small metal
retort, the tar being warmed gently at first, particularly if it contains
water, since it is then liable to froth over. The products are collected
in tared glass beakers. If the tar vapours be condensed by the aid of
water, care must be taken either to stop the supply of water when
paraffin appears in the distillate, or else to use warmed water at this
stage, since otherwise the condenser will get choked up with solid
paraffin. Distillation is conducted at such a rate that 3 to 4 drops
issue from the condenser per second. When1 a drop of the distillate
solidifies on being brought into contact with a lump of ice, paraffin is
indicated and the receiver is changed. The first distillate that does
not contain paraffin is known as crude oil. Sufficient of the paraffin
distillate is driven over to make, in association with the crude oil, 93
per cent of the original tar, the residue being classed as " red product "
and coke.

When the tar is very crude, and especially if it contain solid im-
purities such as coal dust, the distillate will not reach the 93 per cent

154 SHALE OILS AND TABS

The ash content is ascertained by incinerating 1 grm. of the coke
in a crucible. Over-violent incandescence should be avoided, since
otherwise a portion of the carbonic acid in the carbonates of the ash
may be driven off and the results brought down below the truth.

The calorific power can be tested by direct combustion of the coke
in the bomb calorimeter, or else calculated with a fair amount of accur-
acy by the formula : —

8140 (100 - q - w) - 600 w
100

in which a represents the ash content, and w the percentage of moist-
ure in the coke, since when properly made this coke is practically
nothing but carbon and ash constituents, the water having been intro-
duced in the quenching process.

If the coke should burn badly, the reason may be ascertained by
determining the saline matter it contains. Coke containing salt burns
badly, owing to the fact that the particles of salt are fused by the heat
and form a kind of glaze over the coke, which is thus prevented from
burning. The salt is already present in the lignite, and little can be
done to counteract the evil, the best remedy being to leach the coke
with water.

The retort gas, most of. which is utilized for heating the retorts,
can be tested for its calorific value in the Junker calorimeter or the
small portable calorimeter constructed by the author ; l or the same
may be calculated, by the usual formulae, from the analytical com-
position of the gas. When the gas is required for driving gas engines,
the percentage of sulphuretted hydrogen must also be determined —
qualitatively with lead-acetate paper after the gas has been purified,
and quantitatively by titrating the crude gas with iodine solution and
thiosulphate.

The tar water contains about O'l per cent of nitrogen, the amount
being ascertained by acidifying a large volume of the liquid, con-
centrating this down to small bulk and treating it with caustic soda to
liberate the ammonia, which is collected in normal hydrochloric acid.
The quantity of the ammonia is found by titrating the acid back with
normal alkali.^

TESTING THE TAR OILS.

In the course of working up the distillation tars, the various distil-
lation products, the reagents, etc., used, such as sulphuric acid, caustic
soda, and animal charcoal, and the paraffin produced, all have to be
tested.

With regard to the examination of the oils and paraffin masses,
reference may be made to what has already been given in connection
with testing the tar, at least so far as the most important determinations —

aDr. E. Grafe, " Laboratoriumsl'uch fur die Braunkohlenteerindustrie "
(" Laboratory Book for the Lignite-tar Industry"), p. 49.
2 I.e. p. 54.

THE LABORATORY WORK

155

creosote and paraffin — are concerned. In the case of the oils, the specific
gravity, fractional analysis, flashing-point, viscosity, solidifying-point,
sulphur content, and calorific value have to be determined.

The specific gravity is determined by means of the araeometers
used in the mineral oil industry. It should be remembered that the
specific gravity of the oils is lower in the warm, and therefore all deter-
minations should be carried out at a standard temperature (15° or 20°
C. according to specification), or calculated thereto, an allowance of 6
to 8 units in the fourth decimal place being made for each 1° C.

The fractional analysis is performed in the Bngler apparatus as
generally employed in the petroleum industry. 100 c.c. are taken for
the analysis, and the fractions are measured at intervals of 50° C. The
distillation should be carried on at such a rate that 1 to 2 drops of dis-
tillate fall from the end of the condenser per second. The operation
is not continued beyond 300° C., as decomposition then sets in. In the
case of oils containing paraffin, the temperature at which paraffin makes
its appearance is determined by placing a drop of the distillate on ice.
If this solidification point be above 300° C., the thermometer is first
taken out of the flask, which is then closed with the simple cork
only.

The flashing-point is determined intone of the usual forms of test-
ing apparatus, the Abel tester being used for oils of low flashing-point,
and the Pensky apparatus, or a porcelain basin, for the oils of high
flashing-point.

It is also necessary to test the viscosity of the oils. This is not
important in itself, all the lignite-tar oils being too fluid to be suitable
for direct use as lubricating oils ; but some of the
higher fractions are employed for mixing with such
oils. The chief object of the test is to prevent oils
with a viscosity exceeding 2'6 from being sent out,
owing to the higher rate of freight charged on Ger-
man railways. The Engler viscosimeter is generally
used ; and its method of application needs no special
mention here. In the Scottish shale-oil industry, the
Redwood viscosimeter is used.

The solidificat:on point is determined by immers-
ing a thermometer in a sample of oil contained in a
test glass, which in turn is placed in a refrigerating
mixture, from which it is taken at intervals and tilted
to see whether the oil is still fluid. This test is
chiefly applied to the oils intended to be mixed with
lubricating oils, for which purpose an unduly high soli-
dification point is undesirable. These oils generally
solidify at - 5° to - 10° C.

The sulphur content is ascertained by burning the oil in a flask
charged with oxygen, the products of combustion being absorbed by a
solution of sodium peroxide (Fig. 68). The determination is chiefly of
informative value, because sulphur plays a certain part in the lignite

FIG. 68.— Flask

for ascertaining

the sulphur

content.

154 SHALE OILS AND TABS

The calorific power can be tested by direct combustion of the coke
in the bomb calorimeter, or else calculated with a fair amount of accur-
acy by the formula : —

8140 (100 - a - w) - 600 w
100

The retort gas, most of. which is utilized for heating the retorts,
can be tested for it's calorific value in the Junker calorimeter or the
small portable calorimeter constructed by the author ; l or the same
may be calculated, by the usual formulae, from the analytical com-
position of the gas. When the gas is required for driving gas engines,
the percentage of sulphuretted hydrogen must also be determined —
qualitatively with lead-acetate paper after the gas has been purified,
and quantitatively by titrating the crude gas with iodine solution and
thiosulphate.

TESTING THE TAR OILS.

In the course of working up the distillation tars, the various distil-
lation products, the reagents, «tc., used, such as sulphuric acid, caustic
soda, and animal charcoal, and the paraffin produced, all have to be
tested.

JDr. E. Grafe, " Laboratoriumsl-uch fur die Braunkohlenteerindustrie "
(" Laboratory Book for the Lignite-tar Industry"), p. 49.
2 I.e. p. 54.

THE LABORATORY WORK

155

The specific gravity is determined by means of the araeometers
used in the mineral oil industry. It should be remembered "that the
specific gravity of the oils is lower in the warm, and therefore all deter-
minations should be carried out at a standard temperature (15° or 20°
C. according to specification), or calculated thereto, an allowance of 6
to 8 units in the fourth decimal place being made for each 1° C.

The fractional analysis is performed in the Engler apparatus as
generally employed in the petroleum industry. 100 c.c. are taken for
the analysis, and the fractions are measured at intervals of 50° C. The
distillation should be carried on at such a rate that 1 to 2 drops of dis-
tillate fall from the end of the condenser per second. The operation
is not continued beyond 300° C., as decomposition then seta in. In the
case of oils containing paraffin, the temperature at which paraffin makes
its appearance is determined by placing a drop of the distillate on ice.
If this solidification point be above 300° C., the thermometer is first
taken out of the flask, which is then closed with the simple cork
only.

FIG. 68.— Flask

for ascertaining

the sulphur

content.

156 SHALE" OILS AND TABS

tars, which part cannot be influenced in the course of manufacture;
As a rule, oils low in sulphur are preferred for gas oils, there being
then less trouble in refining; but, on the other hand, the sulphur-
content of the oils is practically immaterial so far as the gas is con-
cerned, since nearly all the sulphur products either pass into the tar or
are removed in the refinery. The method of determining the sulphur
content is described in detail in Grafe's book on laboratory work in
the lignite-tar industry (p. 6).1 Lignite tars contain about 0'5 to 1*5 per
cent of sulphur in the form of organic compounds.

The "calorific value of the oils is an important feature, since it deter-
mines their suitability for use in the Diesel engine. Some information
is also afforded as to their utility as gas oils, those rich in hydrogen hav-
ing a higher calorific value than such as are low in that constituent ;
and, according to modern views, such oils are better adapted for the
production of oil gas and for carburetting water gas. Nevertheless,
this property does not increase in strict proportion to the hydrogen*
content. A distinction must be drawn between maximum and mini-
mum heating value, the former being also known as the combustion
value. This maximum value is based on the combustion of the oil,
with simultaneous condensation of the water of combustion derived
from the hydrogen content of the oil. The minimum heating value is
based on the combustion of the oil, without condensation of the water
of combustion ; so that the two values differ by the heat of evaporation
of the water of combustion. This difference amounts to about 7 per
cent of the heat of combustion. The oils at present manufactured
have a calorific value of 9800 to 10,000 calories, and a heat of com-
bustion of 10,400 to 10,700 cal. Oils rich in oxygen, such as the
creosote oils, do not attain these values, the heat of combustion being
only about 9000 cal.

The examination of the paraffin masses is generally confined to the
determination of the percentages of creosote and paraffin. The method
in both cases has already been described in connection with testing the
tar. An important point is the testing of the paraffin scale obtained
by crystallizing and pressing the paraffin masses, this product being
examined for its melting-point, paraffin content, percentage of water
and dirt, and its suitability for refining.

The melting-point is determined either by the capillary-tube or
rotary-thermometer methods already described ; though, for very ac-
curate testing, use is made of the Shukoff method described under the'
section on candlemaking. The paraffin content is ascertained by the
Zaloziecki or Holde method (also previously described), except that,
owing to the high percentage of paraffin, only 1 to 2 grm. of substance
are taken.

The percentage of water - is determined either by heating the par-
affin direct to about 150° C. in a flask, and then ascertaining the loss in

1 See also, " Zeit. angew. Chemie," 1904, 610.

2 The Scottish methods of testing paraffin scale are fully described in the
author's \vork on " Mineral Oils ".

THE LABORATORY WORK 157

weight ; or else by allowing the melted paraffin to settle down for some
time and then solidify, the cake of paraffin being lifted and the deposited
water taken up with a tared filter paper and determined by weighing.
To ascertain the percentage of dirt,1 the paraffin cake from the pre-
ceding test is remelted and filtered through a dry, tared filter, the ad-
herent paraffin being finally washed off with hot benzol, and the filter
weighed. When purchased scale of unknown properties is in question,
•a test must also be applied to see how it behaves in refining. The
material is melted, treated with 15 per cent of benzine (such as is used
in refining paraffin), and poured on to water, as small slabs, which are
then wrapped in filter paper and filter cloth and pressed in a screw-
down press. The pressed cakes are remelted, again mixed with ben-
zine and treated as before. After the third repetition, the paraffin is
freed from superfluous benzine by a jet of steam, and then treated with 2
per cent of decolorizing powder. After repeated filtration through filter
paper, the refined material is moulded into slabs and compared with
the paraffin usually made in the works. The yield of finished paraffin
from crude scale treated in the above manner is about 60 to 75 per
cent according to the melting-point of the material.

TESTING THE REAGENTS USED FOR REFINING THE OILS AND
PARAFFIN.

Sulphuric acid and caustic soda are used in refining the oils. The
caustic soda lye is prepared on the premises, drum soda being dis-
solved by the aid of steam. The strength of the sulphuric acid is
tested by titration, or, more simply, by a specific gravity instrument.
As a rule the arsenic in the acid does no harm and need not be speci-
ally estimated, unless the acid is to be used for other purposes, such as
in soldering the leaden linings of agitators, etc. This welding process
is performed with oxyhydrogen gas, and if the hydrogen for this
purpose be generated from sulphuric acid and zinc, cases of arsenical
poisoning (arseniuretted hydrogen) are always to be expected. Several
cases of this kind have been attended with fatal results in this in-
dustry, and attention is therefore once again drawn to the fact that
the sulphuric acid used should be free from arsenic ; or the gas should
be purchased in cylinders.

Another important point is that the sulphuric acid should be as
free as possible from nitrous compounds, or it will be liable to corrode
and destroy the leaden lining of the agitators.

The caustic soda is tested for its percentage purity. As a rule the
manufacturers give a guarantee of the minimum percentage of free
hydroxide, expressed in terms of carbonate of soda. Thus, a 125 per
cent caustic soda means a soda which, if entirely converted into car-
bonate, would yield 125 per cent of that substance. This method of
calculating is, however, useless in connection with the mineral oil
industry, since the carbonate of soda has no action at all, being incap-
able of entering into combination with creosotes. Hence, in testing

1 " Die Fabrikation der Mineralole," pp. 206 et seq.

158 SHALE OILS AND TABS

the caustic soda, the carbonate is precipitated by treating the normal
solution of 40 grm. of caustic soda in 1 litre of water with 50 c.c. of
^a 10 per cent solution of barium chloride, the liquid being then made
up to 1 litre and titrated with normal hydrochloric acid. Under this
test, caustic soda designated as 125 per cent is generally found to
contain 92 to 94 per cent of free hydroxide.

Benzine and decolorizing powder are used in refining paraffin.
The benzine is usually produced on the premises ; and, like the other
oils is tested for boiling and flashing-points. The former is an impor-
tant factor, as indicating whether the benzine can be easily eliminated
from the paraffin by a jet of steam. A sample of benzine containing
a large proportion of constituents of high boiling-point is either dis-
carded for the purpose in view, or else is separated into high and low
boiling fractions, since otherwise the paraffin cannot be obtained in a
transparent and inodorous condition. An excessively low flashing-
point must also be avoided, as increasing the fire risk in the pressing
and melting processes. As a rule the fire risk of the benzine used for
refining paraffin is not particularly high, the flashing-point being be-
tween 20° and 30° C. (68° and 86° R).

The decolorizing powder usually consists of the residues from the
manufacture of potassium ferrocyanide, and similar agents. The
amount used is between 0'5 and 2 per cent of the weight of paraffin.
Of late a large number of mineral decolorizing agents have also been
placed on the market, and are also employed in the petroleum indus-
try, such as the silicates and hydrosilicates of aluminium and magnesium
(fullers' earth). The test applied is a practical one, partially refined,
but not yet decolorized paraffin being intimately mixed with about 2
per cent of the material on the steam bath for a quarter of an hour, then
filtered and cast into slabs, which are compared with those obtained
in the works. The test, however, is not yet at an end, the slabs being
left exposed to the light for several days because some of these decolor-
ants of the fullers' earth class give a decolorized product which,
though excellent in appearance for the moment, is not fast to light,
but soon turns yellow or brown. For this reason the test for perman-
ence of decoloration should never be omitted. The spent powder,
whether a sample or that used in the works, should always be examined
for the amount of paraffin it has retained, which must be recovered
by a special process. The smaller the quantity of paraffin so retained
the better, other circumstances being equal.

The test is performed in the following manner : 1 to 5 grm. of the
spent powder are weighed out and treated in the extraction apparatus
with a solvent of low boiling-point (e.g. ether, chloroform, carbon tetra-
chloride, or benzol), the extract being poured into a tared basin and the
solvent expelled.

TESTING THE PARAFFIN.

The paraffin produced in the works is, to a large extent, made up
into candles in factories attached to the premises, some portion, how-

THE LABOBATOEY WORK 159

ever, being sold. The tests applied relate to the colour, fastness to
light, and the smell, for which, of course, no special method can be
given, especially since experience plays a large part in appraising the
article by these characteristics.

Apart from these, the principal test is that" for the melting-point.
At one time it was even more important than at present, paraffin then
being sold on the basis of melting-point only, the price increasing or di-
minishing by approximately 6d. per Ib. (1 mark per kilo.) for each dif-
ference of 1° C. in the melting-point above or below a fixed standard.
As a general rule, it may still be considered that, other conditions be-
ing equal, a paraffin of high melting-point is worth more than one with
a low melting-point. The methods 1 of determining the melting-point
are too many to be enumerated here, and it will be sufficient to mention
the one considered to be the best, and which is the most largely used
in the paraffin industry, namely the Shukoff method, recommended
by the Association for Testing Materials. This method is performed
by placing 20 to 30 grm. of paraffin in a jacketed, and preferably
evacuated, vessel (Fig. 69), a thermometer graduated to one-fifth of a
degree being inserted. When the temperature has fallen to
about 3° to 5° C. above the anticipated melting-point, the
vessel is shaken up well until the contents become turbid,
whereupon it is left to stand, the point^tt which the mercury
filament in the thermometer remains stationary being the
melting-point or solidification point of the paraffin. The
rotary thermometer and capillary tube methods already de-
scribed for the determination of melting-point may also be
used as giving rapid, though less accurate results.

It is superfluous to apply any special test for ascertaining
the amount of heavy oils present in paraffin, their presence
being already indicated by lack of transparence (appearance
of cloudy and milky flakes), the smell and low fastness to
light. A direct determination, based on the difference in the
paraffin determination by the Holde or Zaloziecki method
does not give precise results, especially- when the paraffin is
of low melting-point, soft paraffins being always partially
soluble in the precipitants. Provided a sample of paraffin
exhibits sufficient transparence, permanence in colour, and
absence of smell, it may be regarded as free .from oil, especi-
ally when it does not exude oil and produce greasy patches FIG. 69. —
on the wrapper, etc., during prolonged storage. MeoiUt8"

tester for

TESTS APPLIED IN CANDLE WOBKS. paraffin.

In the candle works the raw materials, paraffin, stearine, wick, and
colouring matters, have first of all to be tested. A good deal of the
preceding section has been devoted to the testing of paraffin, and all
that now remains is the test for stability. For this, the melting-point

1 Scheithauer, " Der Fabrikation der Mineralole," pp. 208 et seq.

160 SHALE OILS AND TABS

alone is no criterion, though it may be held as a general rule that the
-stability increases with the melting-point. Nevertheless, commercial
brands of paraffin, though of high melting-point, occasionally fail to
exhibit commensurate stability, the reason being that such paraffin
-consists of hydrocarbons of widely divergent melting-points, a condition
which is found by experience to lessen the resistance to bending, a pro-

• perty that subsequently becomes unpleasantly manifest in the candles.

• The test for stability consists in pouring the paraffin into moulds of the
size of candle to be made (generally § -to f in. thick and 8 to 10 in.

• long), and after leaving them to cool down to uniform temperature for
; some time, fastening the candle in a horizontal position by a clamp at

the base. In this position the test candle is exposed for an hour to a
constant room temperature of 25° C. (77° F.). If it bends appreciably,
the paraffin is unsuitable for being made into candles by itself, and must
' either be rendered suitable by mixing with it some harder paraffin, or
else made up into composite candles with stearine.

Before using a batch of paraffin (especially a purchased article of
unknown properties) for making candles, a sample candle is moulded
and burned. Certain kinds of paraffin are found to burn badly, either
.guttering or smoking ; but in many cases the blame must be laid, not
on the paraffin alone, but on the combination with a certain wick.
Por example, a paraffin which burns badly as a paraffin candle, may
TDurn excellently in admixture with others or as composite candles the
wicks of which have been prepared in a different manner.

An important auxiliary in candlemaking is stearine, large quantities
of which are used; on the one hand for making composite candles
(which contain 25 to 33 per cent of this substance), and on the other
as an adjunct (0'5 to 2 per cent) to paraffin candles to facilitate de-
taching the candles from the moulds. The stearine is not manufactured
in lignite-tar works, but is purchased from the makers. The price
being about double that of paraffin, special attention should be devoted to
testing and valuing the material. There are two commercial varieties
of stearine, one being produced by saponification, and the other by
distillation. The former is of superior colour and smell, as well as
in fastness to light, and is therefore of higher value. It contains less
oleic acid than distilled stearine.

The melting-point of stearine is tested in the same manner as that
of paraffin, by the Shukoff method. The lower the melting-point the
higher the oleic acid content, though the determination of the melting-
point does not give more than approximate information in this par-
ticular.

The exact percentage of oleic acid is determined by the iodine value

(Hiibl or Wijs method, the latter being the quicker). The perform-

, ance of these methods may be considered as too well known to require

. description here. Multiplying the iodine value with I'll gives the

percentage of oleic acid present in the stearine. Specimens rich in

oleic acid are not looked on with favour for making composite candles,

owing to the strong smell, which becomes more decided on storage.

THE LABORATORY WORK 16J

Moreover, the colouring matters used in the candles fade more quickly
when the amount of oleic acid is large. In the case of each new parcel
of stearine, the precaution of making specimen candles and testing
their burning qualities should on no account be omitted. Experience
has shown that some kinds of stearine leave behind, in burning, a long
skeleton in the wick, and this skeleton gradually extends down into the
meniscus of the candle, acting like a second wick and causing it to
gutter. The reason of this is that, owing to defects in manufacture or
other causes, the stearine contains small quantities of lime, the pres-
ence of which can be detected by incinerating a large sample of the
stearine. This, however, is a troublesome operation, and the practical
method of testing the burning properties is simpler.

The candle wicks are purchased, though some works make them
on the premises. In this case also, the practical test, by burning, is
simpler and more decisive than analytical examination. Sometimes
the question to be decided is whether a wick has been already prepared
or not. In such case, about 8 to 12 in. of the wick are suspended from
a needle, and a light is applied to the lower end, the wick being rapidly
consumed. If it leaves merely a thin grey filament of ash, it has not
been prepared, but if the residue is fairly thick, and black in colour, it
may be assumed that the preparatory treatment has already been
applied. &

The last of the auxiliaries used in candlemaking is the colouring
matter. At the present time organic colouring matters are used almost
exclusively, though copper acetate is occasionally employed for green
candles. The colouring matters are tested for their purity and fastness
to light.

So far as purity is concerned, no apprehensions need exist on this
point if the dye-stuffs have been purchased from makers of good repute.
Occasionally, however, injurious admixtures are present, these originat-
ing in the manufacturing process and not being added for the purpose
of adulteration. They are mostly inorganic salts, such as sodium
chloride and sulphate, which have been used in salting out the dye-
stuffs from solution. They may act adversely in two ways : if the
dye-stuffs are added to the candle material direct, the salts interfere
with the burning, the wicks being very sensitive to even small quantities
of certain salts ; on the other hand, if the dye-stuffs are first dissolved,
the salts cause a stubborn retention of colouring matter in the residue.
Some commercial dye-stuffs again contain large quantities of dextrin,
added in order to reduce the colour to a certain strength. Dye-stuffs
of this kind are naturally unsuitable for candlemaking. The percent-
age content of salts and dextrin is determined by extraction with
alcohol or other suitable solvent, in an extraction apparatus, and by
weighing the residue from this treatment.

The fastness to light is determined by colouring sample candles to
the desired depth of shade and wrapping one half of the candle in
opaque paper, the whole being then exposed to the light for several
days or weeks. The uncovered portion will then be found to have

162 SHALE OILS AND TARS

faded more or less, and comparison with the protected moiety will show
how far the colouring matter is permanent.

The laboratory has also to discharge the further task of checking
operations in the moulding shop, the chief being to test the melting-
point of the finished candles, their burning properties and the stearine
content. Owing to its high price, the amount of stearine is kept down
as low as possible, though in composite candles this economy must
not be pushed too far or the candles will be transparent. The stearic
acid is determined by titration, 10 grm. of. the candle material being
melted with 50 to 100 c.c. of hot alcohol and titrated with alcoholic
alkali, standardized so that 1 c.c. exactly corresponds to 0-1 grm. of
stearine. If 10 grm. of material have been taken, the volume of
alkali consumed will directly represent the percentage content of
stearine. This standardized alkali contains 21 '2 mg. of caustic
potash per 1 c.c. The solution is prepared by dissolving 25 to 30
grm. of caustic potash in 50 c.c. of water, and making it up to 1 litre
with 96 per cent alcohol. One grm. of the finely shredded stearine is
weighed out on the chemical balance, and titrated with the alkali in
presence of phenolphthalein until a red coloration is observed. If
9'7 c.c. of alkali are consumed, then 970 c.c. must be diluted to 1 litre
in order to obtain the requisite strength. In testing candles of other
makes it is occasionally desirable to make a further investigation of
the stearine and paraffin, and also to ascertain the amount of light
furnished by a given weight of candle material. This is done in the
following manner : —

Ten grm. of the candle material are melted along with 25 c.c. of
96 per cent alcohol and 25 c.c. of water, and titrated to determine the
stearine content, a few extra c.c. of alkali being added and the whole
left to cool. The paraffin collects on the surface and solidifies, and is
removed and washed in water. The residual red-tinged solution is
diluted with water, then supersaturated with hydrochloric acid, and
the deposited stearine is filtered off, repeatedly washed with water, re-
melted and weighed. Its melting-point and iodine value can then be
determined.

As a rule the origin of the paraffin has to be identified. The method
adopted is to melt about 1 grm. of the paraffin along with about 1 c.c.
of concentrated sulphuric acid, in a test glass, on the water bath.
Under this treatment, petroleum paraffin will generally remain colour-
less, only a slight discoloration being produced in the acid at most,
whereas lignite-tar paraffins turn yellow or brown.

To ascertain the quantity of light furnished by a given weight of
candle material, a weighed portion of candle is lighted in the dark room,
and the intensity of the light is compared about every ten minutes
with a Hefner lamp or standard candle. At the end of one or two
hours the quantity of candle material consumed is ascertained by
weighing the remainder, and the intensity of illumination is calculated
to 1 grm. of material.

Latterly, various stearine substitutes have been proposed for addi-

THE LABOEATOKY WOEK 163

tion to the paraffin ; but these, although producing the milk-white
appearance of the composite candle, do not possess the increased
stability in the warm forming the superiority of the composite over
the paraffin candle. These adjuncts are, spirit, B-naphthol, and vase-
line oil.

Candles made with the addition of spirit gradually part with that in-
gredient during storage, and become transparent again, on the outside
at least. The amount of such volatile adjunct can be exactly deter-
mined by melting a small quantity of the candle material in a tared
test glass and reweighing it after passing a current of dry air through
it for several minutes. If the loss in weight exceeds 1 per cent, the
presence of a volatile adjunct may be suspected, and the nature of
same can be ascertained by a separate test, in which the volatile sub-
stance is condensed by the application of a low temperature.

The presence of B-naphthol is revealed, on the one hand, by the
fruity-ether smell, and on the other, an exact determination can be
made by shaking up the material with a little dilute alkali and adding
one drop of a solution of diazochlorbenzol, a red coloration being pro-
duced, or a red precipitate if the amount of B-naphthol is large.

Vaseline oil is revealed by the greasy feel of the candles and the
grease marks on the wrappers. This adjunct is hardly employed in
practice, though it has been proposed on account of the well-known
milky appearance of paraffin which contains oil.

TESTING THE BY-PRODUCTS OF TAR DISTILLATION.

The by-products in question consist of creosote oil, goudron, and
asphaltum.

Creosote oil is tested for creosote, this being its most impor-
tant constituent, at least for many purposes, such as impregnating
timber. No accurate results can be obtained by shaking up the oil
with concentrated soda lye, the neutral oils in creosote oil being soluble
to a large extent in that reagent. On this account, caustic soda of 12°
strength is used, being renewed until no further decrease in volume
takes place. The difference between the initial and final quantities of
oil corresponds to the creosote content.

The goudron is a black mass of about the consistence of dough.
It should dissolve completely on extraction with benzol. The melting-
point is determined by the method of Kramer and Sarnow, in which
-5 grm. of mercury are placed in a glass tube about 5 to 6 mm. in
diameter (Fig. 70), the lower end of which is then sealed up with a
layer of goudron about 5 mm. high. This small apparatus is warmed
in a water bath, the temperature of which is raised gradually. The
temperature at which the column of mercury breaks through the
goudron is the melting-point or softening point of the latter.

The same method is also applied in determining the melting-point
of the asphaltum — the hard, glossy black residue from the distillation
of the acid resins, the production of which has already been described
in the technical portion of the present work. This asphaltum should,

164

SHALE OILS AND TAES

for the most part at least, be soluble in benzol, though its solubility
in this solvent is no measure of its solubility
in oil of turpentine, benzine, etc., which
varies considerably. Of course no guarantees
of quality can be given for a waste product
of this kind, and it is therefore preferably
dealt with by sample, in so far as solubility
is concerned, this being the plan adopted by
the varnish maker for instance.

A comparatively new commercial pro-
duct of the lignite-tar industry is lignite
bitumen or mineral wax. The melting-point
of this substance is determined by the method
of Kramer and Sarnow. Other values to be
determined are : the solubility in benzol (this
should be as high as possible), the acid and
ether values l — by titrating 1 grm. of the finely
powdered material with alcoholic caustic
potash, in the known manner, after having
been boiled with alcohol — and the ash con-
tent. In many cases it is important to test
the ash for the presence of adjuncts, such
as alkalis, heavy spar, baryta, which have
been detected in many instances. Such test,
however, only becomes necessary when the
ash content considerably exceeds 1 per cent,
in which case the assumption of extraneous

FIG. 70.

Melting point tester for
goudron.

adjuncts becomes justifiable. For some purposes, e.g. the production
of refined mineral wax, it is also important to ascertain the percentage
of resinous constituents in the crude wax. This can be effected by
shaking up 1 grm. of the very finely powdered mineral wax with two
successive portions of ether (5 c.c.), and concentrating the filtrate.
Another way is to extract 5 grm. of the finely powdered wax twice
with 50 to 100 c.c. of hot alcohol, allowing the extract to cool, filter-
ing off the deposited wax and concentrating the yellow or brown
extract. The lower the proportion of such resinous bodies, the more
valuable the wax, under otherwise equal conditions, for the production
of refined mineral wax.

This brief sketch of the work to be done in the laboratories of the
distillation- tar industry, is of course merely a summary of the general
current operations. In many cases the methods of examination de-
scribed have to be amplified by special investigations, which, however,
cannot be gone into here owing to lack of space. A full description of
the laboratory work in this industry has been given by Grafe in his
previously mentioned work on the subject.

1 Grafe, " Laboratoriumsbuch fur die Braunkohlenteerindustrie," p. 152.

CHAPTER XII.

STATISTICS.
A. THE SAXON- THUBINGI AN INDUSTRY.

THE economical development of the Saxon-Thuringian lignite-tar
industiy has had an exceedingly chequered history, the output and
prices being high at one time and depressed at another. The circum-
stances influencing the business career of the industry will now be
described.

When the industry first commenced, about the middle of the last
century, a number of unqualified persons ventured on the production
and treatment of lignite tar, in the expectation of making large
profits with little trouble. They were Destitute of any technical know-
ledge in the "choice of raw material, or in respect of the apparatus
required, the result being numerous cases of severe disillusion and the
failure of many small enterprises ; whereas others, possessing the re-
quisite technical knowledge, worked at a profit in consequence of their
skill in selecting the right material and appliances. The abundant
supply of bituminous lignite was in many cases of far better quality than
is now obtainable at all ; and the cost of refining the products was
small, there being no competition and therefore no high requirements
in respect of quality. Hence the production and treatment of the tar
were an easier matter than is now the case.

The practice now iu force, of combining the raising of the lignite
and the distillation of same under one management, was soon adopted.
The mine owners erected distilling plant and built refineries for the oil
and paraffin produced therein.

The prices obtained for the products were high in comparison with
those now ruling, as is evident from the following comparison of the
rates in 1858 and at the present day : —

Then. Now.

100 km. (2 cwt.) of lamp oil (solar oil) 54- 57 mk. (shillings) 13 mk.

paraffin (m.p. 53° C.) 270 „ „ 53 „

„ „ lignite tar . . 30- 35 „ „ 3- 5 „

This initial and troublous period of the industry was soon replaced
by an era of more uniform and quiet development;. In contrast to the
present day, lamp oil and not paraffin was the main product. This
oil found a ready sale, which was stimulated, early in the 'sixties, by

(165)

166 SHALE OILS AND TABS

the growing importation of American petroleum ; but the latter soon
became a powerful competitor of the indigenous oil and set the market
price of same. At that period the heavier lignite-tar oils found appli-
cation as gas oils, the demand for which increased year by year ; and
the considerable extension of oil gas as an illuminant was of great im-
portance to the industry during the 'sixties. This convenient illuminant
was employed in industrial establishments, small towns adopted it,
and most important of all, the German railways took up this form of
lighting. Since that time the Saxon-Thuringian industry has been
chiefly an oil producer, and has maintained a lively interest in matters
relating to oil gas.

At the end of the 'sixties, the richer bituminous lignites were so far
worked out that the poorer kinds had to be resorted to in order to keep
the existing plant going. The poorer material, however, no longer
yielded the same amount of products, the quantity of lamp oil de-
creased, and that of gas oil increased, finding a ready sale. To re-
duce the loss sustained over the most valuable products — lamp oil and
paraffin — through the fall in prices, improvements in the manufacturing
processes were introduced. The upright retort of Eolle, first success-
fully used at Gerstewitz, found wider application elsewhere. Grotow-
sky and Schliephacke introduced improvements in the distillation and
refining processes, by means of which the cost of production was
lessened.

The prices of the commercial products had fallen in 1869 to : —

30 mk. (shillings) per 100 km. (2 cwt.) of lamp oil.

120 ,, „ „ „ „ „ „ paraffin.

15- 19 „ „ „ „ „ „ „ lignite tar.

all of which are very high in comparison with those now ruling. The
tar output amounted to 37,500 tons.

In 1868 the mineral-oil works entered into closer association for
the protection of their joint interests, and founded the Verein fur
Mineralolindustrie, which, under the direction of Krey, is still discharg-
ing its useful functions. From the early 'sixties, the paraffin was
worked up in candle factories, associated in many places with the
mineral-oil works. The chief centres of consumption for paraffin
candles in Germany are in the east and south. At the end of the
same decade, the production of composite and Christmas-tree candles
was added to the paraffin-candle industry.

At the beginning of the 'seventies, by which time the Kolle retort
had come into general use and low-grade lignite was being worked,
the industry placed a new product on the market, namely coke, which
had hitherto been regarded as a troublesome waste product — which it
really was in the days of the horizontal retort and rich lignite. Now,
however, it became an important article of commerce, forming a valu-
able fuel for the poorer classes of the population. Its economic im-
portance to the industry grew from year to year ; and at the present
day, owing to the low prices of lignite-tar products, many, and indeed

STATISTICS 167

most of the works, would be run at a loss if they were not able to dis-
pose of the coke to advantage. The output of this retort coke is now
about 400,000 to 420,000 tons per annum.

Up to 1870 the lignite of the Saxon-Thuringian industry was
chiefly utilized by chemical preparation (dry distillation) only. Small
quantities of lignite had been used as fuel, and another portion was
made into briquettes by hand and dried, being sold as peat bricks for
domestic fuel. It was not until the middle of the 'sixties that greater
attention began to be devoted to the mechanical treatment of lignite,
and, after years of experiment, the Hertel-Schmelzer wet press was
found to solve the problem of turning out wet-pressed briquettes on a
manufacturing scale by machinery.

Attempts were also made in the early 'seventies to make lignite
briquettes with a binding medium, the manufacture of this product
being taken up at about that time by Eiebeck, subsequent to the ex-
periments conducted by the Sachsisch-Thuringische A. G. fur Braun-
kohlenverwertung at its Von der Heydt mine near Halle. The energy
and activity of Eiebeck were the cause of the rapid development of the
mechanical preparation of lignite to such an extent that the quantity
of material treated in this way soon exceeded that consumed for the
production of tar. From that time onward, the works combined their
distillation and mineral-oil plant with* extensive factories for the pro-
duction of wet-pressed blocks and briquettes. The growth of the
trade in these fuels was accompanied by an increased use of crude
lignite, this development being closely associated with that of other
industries, such, for example, as the sugar and potash industries ; and
in this way compensation was established for the progressive decrease
in the returns from the mineral-oil industry.

Attempts were made to counteract the continued fall in prices in
this latter industry by improved technical methods. The output of tar
was increased, and the cost therefore lowered. The expensive animal
charcoal was replaced by cheaper decolorizing powders, and the large
works introduced artificial cooling, by refrigerating machinery, for
treating soft-paraffin masses. The former importance of solar oil had
well-nigh vanished, its use as a lamp oil being insignificant in com-
parison with petroleum. In order to protect it against this powerful
competitor, an import duty of 6 mk. per 100 km. (3s. per cwt.) was
imposed on American petroleum in 1879, but without effect, the price of
petroleum continuing to decrease, and with it the value of solar oil.
Then the heavier oils, the gas oils, which had become the chief product
su tiered severely under the competition of foreign oils ; and the exten-
sion of the above import duty to these and all other oils in 1885 was
of considerable importance to the home industry. The duty on lubri-
cating oils was raised to 10 mk. per 100 km. (5s. per cwt.), and a
similar duty was laid on imported paraffin and all other solid illumin-
ants (stearine, spermaceti, etc.), which urgently needed protection
against foreign competition.

In order to maintain their position in the gas-oil market, the mineral-

168 SHALE OILS AND TARS

oil works in 1885 formed a sales Syndicate, the Verkaufssyndikat fur
Paraffinole in Halle a/S., an organization which subsequently embraced
all lignite-tar oils, and is still in existence to the great benefit of the
industry.

At the same time, another association, the Deutsche Braunkohlen-
Industrie Verein, was founded to represent the economic interests of
lignite mining. Its activity was of great value to the industry, and
its labours in connection with the questions of railway rates and legis-
lation are worthy of special praise. In 1901 an employers' association
was formed among the members, and is now affiliated to the head
association in Berlin.

The 'eighties witnessed the commencement of social-political legisla-
tion in Germany, beginning with the law of workmen's insurance
against sickness (1883), which was followed by the accident insurance
law and the laws relating to old age and invalidity insurance. Sick
funds and workmen's co-operative insurance associations have been
established at the various works in the lignite and mineral-oil industries.
During the second half of the same decade, gas oils found a ready
sale ; but, as a contrast, the early 'nineties were again unfavourable to
the industry owing to the general economic depression. The economic
position of the consumers of gas oil, namely the spinning, weaving, and
sugar-refining industry, naturally reacts at all times on the mineral-
oil industry. In the middle of the 'nineties, however, business improved
once more, and the oils found buyers, even though at reduced prices.

With the commencement of the new century, the market for oils
fluctuated considerably, and stocks increased from year to year. This
state of things however, was succeeded by a period of active demand
extending to the present day, the oil-producing industry being now a
close corporation. The influence of new methods of application — such
as the carburetting of water gas and the introduction of the Diesel
engine — may be gathered from the statistical Table No. IV.

The new commercial treaties, which came into force on 1 March,
1906, reduced the import duty on oils for these two purposes from 6 mk.
to 3 mk. per 100 km. (Is. 6d. per cwt.), and the duty on soft paraffin
from 10 mk. to 8 mk.' (4s. per cwt.), in spite of the endeavours of the
industry to prevent any such reduction and to obtain an increase on
the duty on paraffin.

In casting a final glance backward over the commercial career of
the Saxon- Thuringian mineral-oil industry, the first thing noticeable is
the continued retrogression in the price of its products. Apart from
slight fluctuations, it is only since the beginning of the 'nineties that
the prices of oil have remained stationary, the level being such, how-
ever, that no reduction is possible without rendering the business unpro-
fitable. Paraffin prices fluctuate continuously, and depend entirely on
the rates fixed by American and Galician producers.

The same state of things prevails in the candle market, the prices
being regulated by both these of paraffin and stearine (including
stearine candles). In the abseace of a candle syndicate, underselling

STATISTICS 169

and keen competition are rife on the part of the numerous German
candlemakers who use imported paraffin. At present the market for
paraffin and paraffin candles is in a very depressed condition ; and as
B. Leupold (Halle) rightly says in his report on the state of the market
in the Saxon-Thuringian mineral-oil industry : " One may scan the re-
cords of the past forty to forty-two years in vain to discover such a de-
preciation in our paraffin and candles ".

As set forth in Table I, the output of lignite tar has been free from
any important fluctuations, and amounts to 60,000 tons per annum.
There is, however, no expectation of any increase in this branch of
the lignite industry of Central Germany. As already mentioned, the
owners of the distilling and mineral-oil plants have, for several de-
cades, associated the mechanical treatment of lignite with the chemical
branch, and are going ahead in this direction, with the idea of balanc-
ing the fluctuating returns from the older branch by the solid benefits
obtainable from the new departure. This was accomplished up to a
few years ago, the extension of the briquetting works keeping pace
with the demand for this fuel ; but now so many new works of this
kind have been established in all parts of Central Germany, that even
the second support of the industry, though believed to be so strong,
threatens to become a broken reed.

The graphical diagrams on following pages show the development
of the industry during the past twenty years : —

Diagram V illustrates the tar output treated in the mineral-oil
works.

Diagram VI shows the production of paraffin oil, which naturally
coincides nearly with V.

Diagram VII shows the decline in the most valuable product of
the industry, namely paraffin. The curve will be seen to have quite
a different course than that in V since 1902, the tar worked having a
much lower percentage of paraffin than formerly, being itself derived
from inferior raw material.

Diagram VIII gives the prices for lignite tar.

Diagram IX gives the prices of gas oil. In neither case are the
fluctuations so extensive as those shown in

Diagram X, representing the paraffin prices. (These, according to
commercial usage, represent the value in marks, based on the melting-
point of the paraffin.)

Diagram XI gives the candle prices, which, like those of the par-
affin, fluctuate extensively.

170

SHALE OILS AND TARS

66 000 r

1890

1900

190!

66000 r

64000.

/ N

64000.

62000.

— —

— — •

r->

1 \

62000.

60000,

•P--

\ >

.SQflOU.

58000,

\ /

56000.

1890

1900

V
06

909

S6QOP.

DIAGRAM V. — Tar output, metric tons.

38000 t

1890

1900

Ofi

Oft

1909

36000.

3600^ ,

34000,

34 000 JL

32000,

32000.,

/~*

\ ,

90WO,

30000.

28000,

28000.

26000.

24000.

890

900

Ofi

DIAGRAM VI. — Paraffin oil output, metric tons.

86000

1890

lyuo

1 90S

86000.

84000

-~s

84000

82000

\ s

80000

1 \

78000

76000

74000

72000

70000

70000 ,

68000

1890

1900

909

DIAGRAM VII.— Production of paraffin, 100 kilos.

7
50

7
13

7
15

1
n

7
KO

5
65

•i

^^_

— v,

890

!»00

909

DIAGRAM VIII. — Price of lignite tar.

STATISTICS

171

MIc

ffa

10
75

Yi
75

11
75

10
25

10
15

9
75

9
25

9
75

10
75

10
50

10
15

13
40

13
25

— \

— S

-^*.

s^_

.,/

1890

<J8

1900

1909

DIAGRAM IX. — Price of gas oil.

DIAGRAM X. — Price of paraffin.

M 93 94 9& D5 !« QR 99 1900 01 02 03 I 04 06 'JG V~> 08 1909

DIAGRAM XI. — Price of paraffin candles.

172

SHALE OILS AND TABS

Additional statistical data are given in the subjoined tables :-
I. Lignite Distilleries in 1909.

Lignite Consumed

No.

Name.

No of
Re-

As Fuel

For Distil-
ling.

Tar
pro-
duced.

No. of

torts.

Metric

Hands.

Hectolitres.

Tons.

(Ihectol. = 2|bus.)

A. Riebecksche Montanwerke,

•

Akt.-Ges., Halle a. S. .

469

1,505,615

6,398,340

22,769.

367

Sachsisch Thiiringische Aktien-

gesellschaft fiir Braunkohlen-

verwertung, Halle a. S.

144

760,190

2,287,445

10,151

132

Werschen-Weissenfelser Braun-

kohlen - Aktiengesellschaft,

Halle a. S

132

653,445

1,583,383

5,239

Zeitzer Paraffin- u. Solarolfab-

rik? Halle a, S.

313,565

1,064,495

4,497

Waldauer Braunkohlen-Indus-

trie-Akt.-Ges., Waldau .

334,309

1,086,040

4,946

Konsol. Haliesche Pfanner-

schaft, Halle a. S. . . ' .

109,295

667,730

3,055

Bruckdorf - Nietlebener Berg-

bauverein, Halle a. S.

75,950

571,249

3,108

Hugo Carlson, Wildschutz

165,595

811,090

2,332

Bunge & Corte, G. m. b. H.,

Halle a. S

136,119

297,110

1,070

Braunkohlengrube Concordia,

Gewerkschaft, Nachterstedt .

403,470

1,042,700

3,967

II2

Naumburger Braunkohlen-Ak-

tiengesellschaft, Naumburg .

145,645

491,575

1,226

1173

4,603,198

16,301,157

62,360

949

The capital invested in these works represents an aggregate of over
£2,000,000.

II. Output of Eetort Coke.

At the present time the output of this coke amounts to 400,000 to
420,000 tons per annum.

The gradual increase in the consumption is apparent from the fol
ing list : —

In 1883 the deliveries amounted to about 130,000 tons.
1884 „ 250,000 „

1893
1898
1900
1902
1905
1909

267,000
326,000
352,000
380,000
405,000
420,000

1 These works were acquired by the Riebeck Co. (I) in 1910.
*Ibid. (1911).

STATISTICS

173

III. Mineral Oil and Paraffin Works in 1909.

No.

Name.

Works.

Tar Treated.
Metric Tons.

Lignite
Fuel
Consumed.
Hectol.

No. of
Hands.

A. Riebecksche Montan-

werke, A. G., Halle. .

Webau

12,050

930,595

495

Sachsisch-Thiiringische

Reussen

6780

186,910

A. G. f. Braunkohlen-

Oberoblingen

4984

184,880

verwertung, Halle.

Gerstewitz

10,283

470,525

161

Zeitzer Paraffin- u.

Solarolfabrik, Halle .

Aue and Dollnitz

9516

533,192

122

Werschen-Weissenfelser

Braunkohlen A. G.,

Halle

Kopsen

5427

247,205

126

and

285 tons

briquettes

Waldauer Braunkohlen-

Industrie A. G., Halle

Waldau

4992

287,922

Bruckdorf-Nietlebener

Bergbauverein, Halle

Nietleben

4027

64,883

Bunge & Corte, G. m. b.

H., Halle .

Oberoblingen

1070

62,090

Dorstewitz-Rattmans-

dorfer Braunkohlen-

Ind. Ges., Halle.

Rattmannsdorf

1633

100,038

Hugo Carlson, Wild-

schiitz

Wildschiitz

2332

19,020

63,048

3,078,260

1253

The aggregate capital invested in these works is about £400,000.
TV. Consumption of Syndicate Oils for Various Purposes.

About 15,000 tons of gas oil are used every year in the production
of oil gas for lighting railway carriages ; and of this quantity over two-
thirds, namely 11,000 tons, are supplied by the Verkaufs-Syndikat fur
Paraffinole. A further 6000 to 7000 tons are sold for gasmaking in
factories, gasworks, etc., the Syndicate furnishing about 5000 tons. The
figures in this connexion show a decline of late years, having been 7200
tons in 1895, 7000 tons in 1900, and 6300 tons in 1903.

The consumption of lignite-tar oils for making cart grease fluctuates,
being now about 1200 tons per annum, against 700 to 800 tons in
earlier years.

Since 1898, mineral oil has been in demand for carburetting water
gas, though it was not until 1901 that the consumption attained note-
worthy dimensions, being then about 1800 tons. From that date the
demand has grown extensively, and now exceeds 20,000 tonsr About
10 to 15 per cent of this trade is conducted through the Syndicate.
] and 2 See notes to preceding Table.

174 SHALE OILS AND TABS

The consumption of mineral oils as a source of motive power in the
Diesel engine has only become noticeable since 1903, from which time,
however, it has largely increased, the quantity now exceeding 15,000
tons a year, about one-third of which passes through the hands of the
Syndicate.

; ? Like the production, the sales of solar oil — now only about 1500
tons per annum — has fallen from year to year, having been 4080 tons
in 1898 and 2320 tons in 1901.

It should also be mentioned that the manufacture of lamp-black
from oil gas has been entirely given up, though at one time about 1500
tons of gas oil were consumed annually for that purpose. The manu-
facturers, however, could not meet the competition of the cheap
American lamp-black from natural gas, and were therefore obliged to
give up the business.

V. Candle Statistics.

The production of the five candle works in this industry amounts
to about 8000 tons of paraffin and composite candles per annum.
About three-fourths of the output is produced by the Riebeck Co.,
and the remainder by the Werschen-Weissenfels Co. and Waldau Co.
Candle factories are attached to the works at Webau, Oberoblingen,
Gerstewitz, Kopsen, and Waldau (Table III).

It may be of interest to append the German imports and exports
of the above products for 1909 and 1910.

Exports. Imports.

1909. 1910. 1909. 1910.

1. Gas oil for engines or for

carburetting water gas . 30,165 30,368 tons

2. Paraffin, crude or refined . 1086 883 15,105 17,047 „

3. Candles of all kinds . „ 783 979 221 205 „

B. STATISTICS OF THE SCOTTISH SHALE INDUSTBY.

The retort has played a far more important part in the develop-
ment of the Scottish shale industry than in that of Saxon Thuringia ;
for, whereas in the latter case the alterations in the retorts have been
merely slight since the 'seventies, new types have been constantly in-
troduced in Scotland down to within the past decade. The chief
reason for this is, as already mentioned, the important role of the
retort coke in the lignite-tar industry, which coke is obtained of excel-
lent quality in the Eolle retort, so that there has been no inducement
to modify the apparatus. The case is different in the Scottish in-
dustry, where the production of sulphate of ammonia takes corres-
ponding rank to retort coke in Germany. At one time the tar water
was thrown away, but since 1865 has been utilized for the recovery of
sulphate of ammonia ; and, as a rule, the modifications in the retorts
have been due to attempts to increase the yield of ammonia. The ap-
paratus now in use are of a thoroughly satisfactory character.

STATISTICS 175

The properties of the raw material (shale) have not changed very
much since the commencement of the industry ; and the cost of
raising the shale has also remained fairly stationary. Beilby l esti-
mates the cost of raising shale, of quality similar to that of the
Broxburn bed, as 5s. Id. per ton (1 ton yielding 30 gal. of tar).
The cost of raising the inferior shale from the deeper Dunnet, Barr-
wacks, and Pumpherston seams is estimated at 4s. Id. per ton.

Keeping down the cost of raising the raw material is at all times an
important factor in the success of distillation works ; and in this respect
the Saxon- Thuringian industry has an advantage over the Scottish in-
dustry inasmuch as only the smaller portion of the material raised is
used for distilling, the remainder being put through mechanical treat-
ment. This extensive output from the mines enables the cost per unit
to be reduced, thus furnishing the distilling plant with cheap raw
material.

The Scottish industry, however, has succeeded in lowering the cost
of distilling and manufacturing from year to year by the continuous in-
troduction of improved methods and appliances. One example will
illustrate this clearly.

At the end of the 'sixties, the raw material for the distilling plant
cost 5s. Id. per ton, and the expense of distilling and refining the tar
from same amounted to 5s. 7^d. per torn. With the high prices then
ruling, the profit on the products obtained from 1 ton of shale was
9s. 8|d. On the basis of the present low prices, and assuming the cost
of production to have remained the same, there would be a loss of
4s. 3jd. ^

Subsequently, however, the cost of dry distillation was reduced
considerably, being 2s. 7d. per ton of shale in 1882, and 2s. 0|d. in
1897. At the same time the expense of distilling and refining the tar
products was reduced to 3s. 7d. in 1882 and Is. 11-Jd. in 1897 ; so that
in the former year the profit per ton of shale amounted to 3s. lO^d., and
in the latter year to 2s.

As in the German industry, the selling prices of the chief commercial
products have fallen continuously, and are very low at present ; and
only the old-established works, which shared in the period of prosperity
and have accumulated large reserves, have been able to distribute
dividends.

The output of shale increased from 1,000,000 tons in 1880, to over
2,250,000 tons in 1890, and now exceeds 2,500,000 tons. There has
been a growth in the amount of tar subjected to further treatment, the
quantity at present being about 250,000 tons per annum, or more than
four times the weight of lignite tar treated in the German industry.
» The sulphate of ammonia produced amounts to 50,000 to 60,000
tons per annum.

The output of commercial products is about :—

1 " Journ. Soc. Chem. Ind.," 1897, pp. 876 et seq.

176 SHALE OILS AND TABS

Naphtha 2,376,000 gal.

Illuminating oils of all kinds . . . .16 200,000 ,,

Gas oils 38,600 tons.

Lubricating oils 40,600 „

Paraffin 22,800 „

Retort coke 5000 „

The difficulties with which this industry has had to contend may be
gathered from the fact that, out of 117 works which have been estab-
lished at one time or another, only six are still in operation, the others
having succumbed to unfavourable circumstances. The six concerns
are : Broxburn Oil Co., Dalmeny Oil Co., Oakbank Oil Co., Pum-
pherston Mineral Oil Co., Tarbrax Oil Co., and Young's Paraffin Co.

The number of retorts in work exceeds 1500. Four of the com-
panies have mineral oil and paraffin works, and two have candle fac-
tories attached to the premises. The industry employs 8300 hands,
of whom 3380 are miners ; and the aggregate wages' bill amounts to
about £700,000.

[THE END.]

INDEX.

Accumulator for hydraulic press, 104.

Agitator house, description of, 92.

Agitators, description of, 87.

Alkali-
Amount used in refining tar products,

90.
Recovery of the spent, 96.

Alkalinification, 87.

American petroleum, influence of, 167.

Ammonia —

Determination of, 154.

Liquor, 53.

Recovery apparatus, 56.

— of, 40.

— of, from Messel tar, 37.
Sulphate of, from Messel tar, 56.

— of, from shale tar, 56.
Ammoniacal vapours, treatment of,

57.
Ammonium salts, influence of, on wicks,

130.
Analysis of —

Gas from shale-tar retorts, 85.

Gases from tar distilling, 77.

Lignite, 148.

- ash, 14.

Pyropissit, 13.

Retort gas, 58.

Shale ash, 15.

Tars, 151.
Aniline dyes, use of, in candle-making,

131.

— from tar, 142.
Apparatus for —

Continuous distillation, 71.

Tar distilling, 65.

The Messel distillation process, 80.
Aromatic hydrocarbons in lignite tar,

140.

Arsenic in acid, effect of, 157.
Ash, determination of, 154.
Asphaltum —

Properties and uses of, 119.

Tests of, 163.

Aspirator, description of, 153.
Australian bitumen, 12.'

Barrels for oil storage, preparation of,

114.
Baryta, use of, in refining tar products,

89.

Batterv of retorts, 33, 40.
Beilby's retort, 44.

— tar water apparatus, 56.
Benzine —

As washing agent for paraffin, 104.

From shale-tar distillation, 85.

Obtained in the Scottish industry, 123

Properties and treatment of, 77.

uses of, 115.

Tests of, 158.
Bitumen —

Australian, 12.

Definition of, 19.

Determination of, 150.

Separation of, 18.

Solvents of, 13.

Uses of, 19.

Bituminous coal, distillation of, in Ger-
many, 7.

— lignite, estimation of tar yield from,

148.

origin of, 10.

testing of, 147.

— material, deposits of, 8.
separation of, 17.

— shales, deposits of, 9.

origin of, 12.

Bleaching agents used for paraffin, 107.

— paraffin, method of, 107.

— sun, 91.
Blue oil, 82.

Bricked retort, section of, 26.
Bricks for Rolle retort, 24.
Brine, use of, 99.
Briquettes from lignite, 167.

— manufacture of, 17.
Bryson's retort, 48.

(177)

178

SHALE OILS AND TABS

Calorific power, determination of, 154.

— value of coke, 61.

of distillation gas, 40.

of gas oil, 116.

of gases from tar distilling, 77.

of oils, 156.

of retort gas, 59.

significance of the, 156.

waste gases, 40.

Candle-making, history of, 125.

— market, economic conditions of the,

169.

— production, statistics of, 174.

— waste, working up, 137.

— wicks, tests of, 161.
Candles —

Colouring of, 131.

Composite, 128.

Cutting, 136.

Dipping, 332.

Early manufacture of, 3.

— use of, 127

Finishing processes for, 136.

Manufacture of, 125.

Moulding, 132-4.

Polishing, 136.

Raw material for, 127.

Sizes and shapes of, 136.

Tests of, 159.
Carbolic acid, 141.

Carbon disulphide in lignite tar, 143.
Carburetted water gas, advantages of,

117.
Carburetting water gas, 116.

influence of, 168.

Caustic soda —

For refining, 86.

Tests of. 157.

Use of, in refining tar products, 89.
Cellulose, decomposition • of, 11, 19.
Centrifugal separators, 101.
Charging retorts, 70.

treatment of material for, 31.

Chemical bleaching of paraffin, 105.

— treatment, tar products to be dealt

with, by, 90.

of distillates, 64.

of tar, 88.

of wicks, 130.

Clarifying candles, process of, 134.
Cleaning condenser in tar distillation,
70.

— oil, properties and uses of, 116.
treatment of, 90.

— - retorts, 32.

Coal, dry distillation of, 1.

— testing of, 148.
Coke-
Amount of, in lignite, 14.

Coke-
As a purifier, 63.
Calorific value of, 61.
Cooling methods of, 32.
Effect of salt on, 154.
Estimation of, 149.
Extraction of, from retorts, 31.
For heating purposes, 62.
From lignite tar, uses of, 76.

— retorts, properties of, 61.

— shale tar, 84.

Influence of, on the oil industry, 166.

Output of, 173.

Kesidue from Messel coal, 37.

Tests of, 153.

Used for pigments, 63.
Coking stills for shale tar, cleaning, 81.
Colouring matters for candles, 131.

tests of, 161. ; ;

Condensers, 50.

— used in tar distilling, 67.
Condensing plant for lignite tar, 28.
Cone and bell for Bolle retort, 25.
Constituents of lignite tar, 144.

— of shale tar, 146.

Consumption of fuel in tar distilling,

71.
Continuous distillation, apparatus for,

71.

— process of distillation, of shale tar,

81.

— working retorts for lignite tar, 22.
Coolers, 23.

Cooling processes in candle manufac-
ture, 135.

— towers, 41.

" Cracking," 65.
Creosote, 87.

— determination of, 152.
Creosote oil —

Properties and uses of, 119.

Tests of, 163.
Creosotes from lignite tar —

Properties of, 142.

Sulphur compoundsvof, 141.
Crichton's retort, 47.
Crude paraffin, early methods of refining,
103.

press plant for, 105.

Crude oil, 81.

analysis of, 152.

composition of, 146.

from lignite tar, properties of, 76.

properties of, 53.

treatment of, 77.

yield from, in the Scottish in-
dustry, 122.

Crusher for paraffin masses, 100.
Crystallization of paraffin, 97, 98.

in the Messel industry, 108.

in Scottish industry, 109.

INDEX

179

Decolorizing agents, tests of, 158.

— of paraffin, agents used in, 107.

— paraffin in the Scottish industry, 112.
Decomposition of —

Paraffin, prevention of, 70.

Shale tar, 83.
Dialysis of paraffin, 98.
Diesel motor —

Action of the, 117.

Influence of the, 168.

— motors, oil for, 117.
Distillates from tar, 138.
Distillation—

At atmospheric pressure, plant used
in, 67.

Description of process of, 69.

Gas, calorific value of, 40.

In partial vacuo, advantages of, 71.

plant used in, 67.

Methods of, 64.

Plant, used in, 33, 67.

Plants, introduction of, into Ger-
many, 5.

Products from the Messel process, 80.

— testing the, 151.

Steam, see steam distillation.

Tar, value of, 53.

Yield and cost of, of shale tar, 51.
Dry distillation —

Process of, 29.

Of tar, 20.

Of coal, 1.
Duty on oil, 167.

Dye-stuffs in candle-making, properties
of, 161.

Early methods of refining crude paraffin,

104.

Eupion, 2.
Exhausters, 28.
Exhaust fans, 41.
Explosions, prevention of, 30.

Fat oil, properties and uses of, 118.
Filter press, for paraffin, 100.
Finishing processes for candles, 136.
Firebricks for retort building, 27.
Flat wicks, advantage of, 130.
Fractional analysis, 155.
Frankfurt black, 63.
Fuller's earth, use of, 158.

Gas, amount of, in lignite, 14.
— engines for waste gases, 61.

Gas, from retorts as illuminating gas,

61.
properties of, 58.

— oil, 78.

consumption of, 173.

from shale tar, 84.

price of, diagram showing, 171.

properties and uses of, 116.

treatment of, 90.

Gases from shale tar distillation, analysis

of, 85.

Gay-Lussac's analysis of paraffin, 2.
Geological features of deposits, 9, 12.
Glauber salt, formation of, 94.
" Goudron,1' 94.
Goudron, 7H, 119.

— tests of, 163.
Green oil —

Chemical treatment of, in the Scottish

industry, 93.
Treatment of, 83.

Grouven's process of ammonia recovery,
37.

Hard paraffin mass from shale tar, 83.
Heating of candle material, 134.

Ibf mixers, 88.
Heating of retorts, 29.
Heavy burning oil from shale tar, 83.

— oil of the Scottish industry, 94.
Henderson's retort, 42, 46.

— tar water apparatus, 57.
Horizontal hydraulic press, 103.
Hydraulic press for paraffin, 100, 102.
Hydrocarbons —

Aromatic, in lignite tar, 140, 141.
Composition of, 139.
Condensation of heavy, 29.
In lignite tar, 139.
Of the paraffin series, 144.
Production of saturated, 139.
Reactions of, 140.
Unsaturated, indications of, 140.
— properties of, 140.

Illuminating power of candles, 129.
— value of candle material, determina-
tion of, 162.
Isolation of paraffin, 98.

Laboratory, functions of the, 147.

— work of the, 147.
Lamp oil—

From the Messel distillation, 80.

— shale tar, 84.

Solar oil used as, 115.

180

SHALE OILS AND TABS

Lamp oils, recovery of, by distillation,

72.

Leaching, 90.

Lead for mixer linings, 87.
Light lignite-tar oil, properties and uses

of, 115.

— oil, from shale tar, 83.
Lignite-
Ash, analysis of, 14.

Bitumen, tests of, 164.

Briquettes, 167.

Deposits of, 8.

Distilleries, list of, in 1909, 172.

Method of working deposits of, 15.

Mining, Federation of, in Germany,
168.

Pitch, properties and uses of, 119.

Tar, yield of, in Saxon Thuringian
industry, 113.

— distillation of, 68.

— formation of, 138.

— industry, development of, 169.

— oils, consumption of, 173.

— output of, 169.

— price of, diagram showing, 170.

— substances contained in, 144.

— water, 54.
Lignites —

Composition of, 12.

Properties and analysis of, 12.
Lime, use of, in refining tar products, 89.
Lubricating oils, 119.
from shale tar, 83.

Melting-point —

Determination of, 156.

Of paraffin, 121.

determination of, 153, 159.

points of paraffin candles, 1^:8.

Messel coal-
Coke from, 37.

Extraction of tar from, 36.

Method of working, 17.

Properties of, 14.
- distillation process, apparatus for

the, 80.
Mineral oil —

Consumption of, 174.

Works, list of, 173.

— Federation of, in Germany, 166.
Mineral wax, 18.

distillation of, 138.

tests of, 164.

Mixers, description of, 87.
Moisture, determination of, 153, 156.
Motor spirit, 85.

obtained in the Messel industry,

122.
Scottish industry 123.

Moulding candles, 132.

— machine for candles, method of

operating, 134.
Moulds for candles —

Materials used in, 133.

Method of working, 132.

Naphtha —

Obtained in the Scottish industry, 123.

Output of, 176.

Properties and treatment of, 83.
Naphthalene —

Decomposition of, 141.

Formation of, 140.

Naphthol in candles, detection of, 163.
Neutral oils, treatment of, 143.
Nitriles from tar, 142.
Nitrogenous constituents of tar, 142.

in tar, 138.

Non-bituminous coal, use of, 17..

Oil-
Blue, 82.

Crude, see Crude oil.

Fat, 118.

For Diesel motors, 117.

Fuel for steam raising, 118.

Gas, 116.

— lighting, adoption of, by German
railways, 166.

Green, 83, 93.

Heavy, 83, 94.

Lamp, 72, 80, 84, 115.

Mineral, consumption of, 173.

Shale, properties and yield of, 15.

Shales, distillation of, in America, 4.

Tar from lignite, 29.

Washery, 41.

Washing, 87.
Oils-
Lubricating, 83, 119.

Obtained in the Messel industry, 122.

Saxon - Thuringian industry,

113.

the Scottish industry, 122.

Treatment of, in the Scottish industry,

94.
Oleic acid, properties of, 128.

tests of, 160.

Origin of bituminous lignite, 10.
shales, 12.

Packing candles, 137.
Paraffin candles, price of, diagram show-
ing, 171.

INDEX

181

Paraffin— '
Analysis of, 2.
Bleaching, 107.
Chief uses of, 121.
Composition of, 2.
Condensation of, 29.
Crystallization of, 89.
Detection of, in distillate, 151.
Determination of heavy oils in, 159.
Dirt in, determination of, 157.
Discovery of, 1.
Dialysis of, 98.

Effect of mixture with stearine, 129.
Filtering, 100.
For candles, tests of, 160.
From wood tar, 2.
Grease, properties of, 76.
and uses of, 119.

— treatment of, in Scottish industry,

123.

Hard, 83.
In the Saxon-Thuringian industry,

97, 98.

In tar, determination of, 152.
Manufacture of, 97.
Mass, treatment of, 76.

— yield of crude petroleum from, 102.
Melting-point of, 12, 153, 159.
Obtained in the Messel industry, 122.
Scottish industry, 123.

Oil output, diagram of, 170.

Press for, 100, 102.

Price of, diagram showing, 171.

Properties and uses of, 120.

Scale sweating process described, 109.

— dissolving, 104.

— treatment of, 103.
Solvents for, 120.
Tar from lignite, 29.
Tests of, 15S.

Treatment of, after refining, 98.

— of, in Messel industry, 108.

— of, in the Scottish industry, 109.
Works, list of, 173.

Yield of crude, 102.
•Peat, dry distillation of, 2.
Petroleum paraffins, use of, in candle

making, 128.
Phenols, existence of, in tar, 141.

— isolation of, 141.
Photogen, 115.

Picene, formation and properties of, 141.
Plant used for distilling shale tar, 83.

in the distillation of tar, 74.

Polishing candles, 136.
Potassium ferrocyanide use of, 158.
Pouring candle material, conditions of,

134.
Pressing paraffin in the Messel industry,

108.

— paraffin, method of work in, 100.

Press oils, distillation and properties of,
78.

— plant for paraffin, 105.
Production of paraffin, 64.
diagram of, 17

Products obtained from lignite tar dis-
tilling, 77.

— of distillation, 52.

of lignite tar, 76.

of shale tar, 83.

— of Saxon-Thuringian industry, 113.

— of the Messel industry, 122.

Scottish industry, 122.

Properties of crude oil, 53.

— of lignite tar, 52.

— of retort gas, 58.

— of shale tar, 53.

Purification of paraffin with steam, 106.

— of tar water from lignite, 54.
Pyridin bases, uses of, 120.
recovery of, 91.

— properties and uses of, 142.
Pyrocatechin, formation of, 142.
Pyropissit, analysis of, 13.

— composition of, 10.

Quinolin from tar, 142.

Ramdohr's method of distillation, 20.
Raw material, treatment of, 40.
for shale tar, 50.

— materials, sampling and testing, 147.
Reagents, use of, 87.

Red product, 151.

from lignite tar, 76.

Refining in the Scottish industry, 93.
— of lignite tar, 87.

— of tar and its distillates, 86.
Refrigerating machinery, use of, 99.
Reichenbach, Baron von, discovery of

paraffin, 1.
Residue from distillation of Messel tar,

40.
Residues of distillation, 61.

— treatment of, in the Messel industry,

63.

Resinous constituents of wax, determi-
nation of, 164.
Resins, acid, 87.

separation of, 91.

treatment and properties of, 94.

— uses of, 94.

Retort charging for lignite tar, 22, 31.
treatment of material for, 31.

— coke, output of, 172.

— for estimation of tar yield, 148.

— gases, consumption of, in motors, 60.

182

SHALE OILS AND TABS

Eetort houses, 35.
Betorts, 21-7, 29-52.

— amount of material distilled in, 31.

— arrangement of, 33.

— cleaning of, 32.

— cooling of, 33.

— development of, 50.

— difficulties in working, 33.

— for tar distilling, 65, 79.

— heating of, 29, 39, 50.

— method of working, 50.
for lignite tar, 27.

— quantity of shale distilled in, 47.

— shape of, for lignite tar, 21.

— types of, for shale tar, 41.

— vertical, dimensions of, 23.

— work done in, 39.

— working process of, 39.
Rolle retort, 22-26.
Rotary retorts, 27.

Salt, effect of, on coke, 154.
Sampling raw materials, 147.
Saxon -Thuringian industry, history of
the, 165.

manufacture of paraffin, 98.

products obtained in, 11§.

treatment of paraffin, 98.

Scottish industry, refining process in the,

93.

Scrubbing retort gases, 60.
Separation of bituminous and non-
bituminous material, 17.

— of paraffin, 97.

— of water from tar, 89.

Shaft mining, in lignite deposits, 16.
Shale beds, method of working, 17.

— industry, statistics of, 174.

— output of, 175.

of products from, 175.

— tar, apparatus for distilling, 81.
composition of, 146.

cost of distilling, 51.

decomposition of, 83.

James Young's distillation of, 3.

recovery of, 41.

retorts for, 41.

temperature in retorts for, 45

46.

water, 56.

Silicates of aluminium and magnesia

use of, 158.

Soap from candle waste, 137.
Soda-tar, 87.
decomposition of, 95.

— — properties and uses of, 119.
uses of, 94.

Sodium carbonate, use of, in refining
tar products, 89.

oft paraffin mass from shale tar, 83.

use of, in candle-making, 128.

" olar oil —

Consumption of, 174.

Properties and uses of, 115.

Treatment of, 90.
Solidification point, determination of,

155.

Solubility of paraffin and oils, 98.
Standard alkali, 162.
Steam distillation, description of process
of, 71.

— jet treatment of paraffin, 106.

— raising with oil fuel, 118.

— use of, in distillation process, 20.

of, in purification of paraffin, 106.

Stearic acid, determination of, 162.
Stearine, effect of mixture with paraffin,

129.

— properties and uses of, 128.

— receptacles for, 134.

— soap, 137.

— substitutes for, 129, 163.

— tests of, 160.

— varieties of, 160.

Stills used for continuous process of dis-
tillation, 81.

in the Messel process, 80.

Storage of stearine, 134.

— of wick, 131.

— tanks for oil, 113.
Stoves for coke burning, 62.
Sugar industry, influence of, 101.

— refining industry, influence of, 168.
Sulphate of ammonia, output of, 175.
Sulphur compounds in lignite tar, origin

of, 142.

— determination of, 155.
Sulphuretted hydrogen, determination

of, 154.

from tar, 143.

Sulphuric acid —

Effect of impurities in, 157.

For refining, 86.

Tests of, 157.

Use of, in refining tar products, 89.
Sun bleaching, 91.
Sweating house, description of, 110.

— process, description of, 110.

Tapering candles, 136.
Tar —

Amount of, in lignite, 14.

Chemical treatment of, 88.

Determination of quality, 151.

Distillates from, 138.

— in France, 2.

Distillation of, in Australia, 7.

Distilling, apparatus used in, 65.

INDEX

183

Tar-
Dry distillation of, 20.
Earliest distillation of, 1.
Estimation of yield from lignite, 148.
Extraction of, from Messel coal, 36.
From lignite, properties of, 52.

— shale, properties of, 52.
Loss in manufacture, 149.
Oils, distillation of, 82.

— testing of, 154.
Output, diagram of, 170.
Products for chemical treatment, 90.
Refining, 86.

Testing of, 150, 151.
Water, 53.

— estimation of, 149.

— from Messel coal, 55.

— purification of, from lignite, 54.
- tests of, 150.

— value as a manure, 54.

Yield- from, in the Messel industry,
122.

— of, 33.

— of from Messel coal, 19.
Temperature, chemical action due to,

20.

— influence of, in tar distillation, 139.

— of pouring candle material, 136.

— of retort flues .30.

— of waste gases, 39.
Testing raw materials, 147.

— the by-products of tar distillation,

163.

Time occupied in distilling, 70.
Treatment of ammoniacal vapours, 57.

— of oils, 90.

— of paraffin in the Messel industry,

108.
in the Scottish Industry, 109.

— of permanent gases, 76. * «

— of raw material, 40.

— of residue in the Messel process, 80.

— of residues in the Messel industry, 63.
in tar distilling, 70.

— of tar for distillation, 69.

Treatment of vapours, from Messel tar,

40.
Trinkler motor, principle of the, 118.

Utilization of retort gas, 59, 61.
Utilizing waste gases, 40.

Vapours from distillation, treatment of,

from Messel tar, "40.
Vaseline oil in candles, detection of, 163.
properties and uses of, 115.

— oils, treatment of, 90.
Vertical hydraulic press, 102.

— retorts, introduction of, 166.
for lignite tar, 22.

Viscosity of oils, determination of, 155.

— of solar oil, 115.

— of vaseline oil, 115.
Volatile oil, washing of, 41.

Washing agents for paraffin, 104.
Waste products, recovery of, 95.
Water, determination of, in lignite, 3.48.

— gas manufacture of, 116.

— separation of, from tar, 89.
Whiteness of candles, substances pro-
ducing, 129.

Wick, method of supporting in moulds,

133.
Wicks, manufacture of, 130.

— weight of, 130.

Yarn for wicks, 130.

Yellow oil, treatment of, 90.

Young, James, treatment of shale tar

by, 3.
Young's retort, 42.

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Catalogue

Special

PAGE
Agricultural Chemistry ... 9
Air, Industrial Use of ... 10
Alum and its Sulphates ... 8
Ammonia ... ... ... 8
Aniline Colours ... ... 3

INDEX TO SUBJECTS

PAGE

Engraving ... 23
Essential Oils 7
Evaporating Apparatus ... 19
External Plumbing ... 20
Fats ... 6

PAGE
Pottery Decorating ... 11
Pottery Manufacture ... 11
Pottery Marks 12
Power-loom Weaving ... 14
Preserved Foods ... 22

Animal Fats 6
Anti-corrosive Paints ... 4
Architecture, Terms in ... 22
Architectural Pottery ... 12
Artificial Perfumes . . 7
Balsams 9
Bleaching 17
Bleaching Agents 17
Bone Products 8
Bookbinding 23
Brick-making ... 11, 12
Burnishing Brass 20
Carpet Yarn Printing ... 16
Casein 4
Celluloid 23
Cement 22
Ceramic Books 11
Charcoal 8

Faults in Woollen Goods 15
Flax Spinning ... ... 18
Food and Drugs 22
Fruit Preserving 22
Gas Firing 19
Glass-making Recipes ... 13
Glass Painting ... .. 13
Glue-making and Testing .. 8
Greases .. 6
Gutta Percha 11
Hat Manufacturing .. 15
Hemp Spinning ... .. 18
History of Staffs Potteries 12
Hops 21
Hot-water Supply ... 21
India-rubber 11
Industrial Alcohol 9
Inks 3459

Printers' Ready Reckoner 23
Printing Inks ... 3, 4, 5
Recipes 8
Resins 9
Ring Spinning Frame .. 18
Risks of Occupations .. 10
Riveting China, etc. .. 12
Sanitary Plumbing .. 20
Scheele's Essays 8
Sealing Waxes 11
Shale Oils and Tars .. 10
Shoe Polishes 6
Silk Dyeing 17
Silk Throwing 17
Smoke Prevention 19
Soap Powders 7
Soaps 7
Spinning ... ...15, 17, 18

Chemical Analysis 8
Chemical Essays 8
Chemical Reagents . . 8
Chemical Works 8
Chemistry of Pottery . . 12
Clay Analysis 12
Coal-dust Firing 19
Colour Matching 16
Colliery Recovery Work. . 18
Colour-mixing for Dyers. . 16
Colour Theory 16
Combing Machines ... 18
Compounding Oils .. ... 6

Iron-corrosion 4
Iron, Science of ... ... 19
Japanning , ... 21
Jute Spinning y ... 18
Lace-Making 15
Lacquering 20
Lake Pigments 3
Lead and its Compounds... 10
Leather-working Mater'ls 6,11
Libraries 24
Linoleum 5
Lithography 23

Spirit Varnishes 5
Staining Marble, and Bone 23-
Stain-removing Soaps ... 7
Steam Drying 10-
Steel Hardening 19-
Sugar Refining 2*
Sweetmeats 22
Technical Schools, List ... 24
Terra cotta 11
Testing Paint Materials ... 4
Testing Yarns 15
Textile Fabrics ... 14, 15
Textile Fibres 14

Condensing Apparatus ... 19
Cosmetics 7
Cotton Dyeing 17
Cotton Spinning ... 17, 18
Cotton Waste 18
Damask Weaving 15
Dampness in Buildings ... 22
Decorators' Books ... 4
Decorative Textiles ... 15
Dental Metallurgy 19
Disinfectants 9
Drugs ... 22
Drying Oils '". 5
Drying with Air 10
Dyeing Marble 23

Manures 8, 9
Meat Preserving 22
Medicated Soaps 7
Metal Polishing Soaps ... 7
Mineral Pigments 3
Mineral Waxes 6
Mine Ventilation 18
Mine Haulage 18
Mining, Electricity ... 19
Needlework 15
Oil and Colour Recipes ... 3
Oil Boiling 5
Oilmen Sundries ... ... 3
Oil Merchants' Manual ... 6
Oils 6

Textile Materials 14
Timber 21
Toilet Soapmaking ... 7
Varnishes 5
Vegetable Fats 7
Vegetable Preserving ... 22
Warp Sizing 16
Waste Utilisation 9
Water, Industrial Use ... 10
Water-proofing Fabrics ... 16
Waxes 6
Weaving Calculations ... 15
White Lead and Zinc ... 5
Wiring Calculations ... 21
Wood Distillation ... 21

Dyeing Woollen Fabrics... 17
Dyers' Materials 16
Dye-stuffs 17
Edible Fats and Oils ... 7
Electric Lamp Develop-
ment 21
Electric Wiring ... 20, 21
Electricity in Collieries ... 18
Emery 24
Enamelling Metal ... 13, 21
Enamels 13
Engineering Handbooks ... 19

Ozone, Industrial Use of... 10
Paint Manufacture ... 3
Paint Materials 3
Paint-material Testing . . 4
Paint Mixing 3
Paper-Mill Chemistry . . 13
Paper-pulp Dyeing . . 13
Petroleum ... ... . . 6
Pigments, Chemistry of . . 3
Plumbers' Work 20
Pottery Clays 12

Wood Extracts 21
Wood Waste Utilisation... 22
Wood-Dyeing 23
Wool-Dyeing 17
Woollen Goods ... 15, 16, 17
Woven Fabrics 16
Writing Inks 9
X-RavWork 11
Yarn Sizing 16
Yarn Testing 15
Zinc White Paints .. 5

PUBLISHED

SCOTT, GREENWOOD & SON,

8 BROADWAY, LUDQATE, LONDON, B.C.

FULL PARTICULARS OF CONTENTS

Of the Books mentioned in this ABRIDGED CATALOGUE
will be found in the following Catalogues of

CURRENT TECHNICAL BOOKS.

LIST I.

Artists' Colours — Bone Products — Butter and Margarine Manufacture— Casein —
Cements — Chemical Works (Designing and Erection) — Chemistry (Agricultural, Indus-
trial, Practical and Theoretical) — Colour Mixing — Colour Manufacture — Compounding
Oils — Decorating — Driers — Drying Oils — Drysaltery — Emery — Essential Oils — Fats
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Theory)— Cotton Combing Machines— Dyeing (Cotton, Woollen and Silk Goods) —
Dyers' Materials — Dye-stuffs — Engraving— Flax, Hemp and Jute Spinning and Twisting
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Point Lace— Power-loom Weaving— Printing Inks— Silk Throwing— Smoke Preven-
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—Textile Materials— Textile Fabrics— Textile Fibres— Textile Oils— Textile Soaps-
Timber — Water (Industrial Uses) — Water-proofing — Weaving — Writing Inks — Yarns
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the Oil and Fat Industry in General. By GEORGE H. HURST,
F.C.S. Third Revised and Enlarged Edition. Seventy-four
Illustrations. 384 pp. Demy 8vo. Price 10s. 6d. net. (Post
free, lls. home ; lls. 3d. abroad.)

TECHNOLOGY OP PETROLEUM : Oil Fields of the

World — Their History, Geography and Geology — Annual Pro-
duction and Development — Oil-well Drilling — Transport. By
HENRY NEUBERGER and HENRY NOALHAT. Translated from the
French by J. G. MC!NTOSH. 550 pp. 153 Illustrations. 26 Plates.
Super Royal 8vo. Price 21s. net. (Post free, 21s. 9d. home;
23s. 6d. abroad.)

MINERAL WAXES: Their Preparation and Uses. By
RUDOLF GREGORIUS. Translated from the German. Crown 8vo.
250 pp. 32 Illustrations. Price 6s. net. (Post free, 6s. 4d.
home ; 6s. 6d. abroad.)

THE PRACTICAL COMPOUNDING OF OILS,
TALLOW AND GREASE FOR LUBRICA-
TION, ETC. By An EXPERT OIL REFINER. Second
Edition. 100 pp. Demy 8vo. Price 7s. 6d. net. (Post free,
7s. lOd. home ; 8s. abroad.)

THE MANUFACTURE OF LUBRICANTS, SHOE
POLISHES AND LEATHER DRESSINGS. By

RICHARD BRUNNER. Translated from the Sixth German Edition
by CHAS. SALTER. 10 Illustrations. Crown 8vo. 170pp. Price
7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

THE OIL MERCHANTS' MANUAL AND OIL
TRADE READY RECKONER. Compiled by
FRANK F. SHERRIFF. Second Edition Revised and Enlarged.
Demy 8vo. 214 pp. With Two Sheets of Tables. Price 7s. 6d.
net. (Post free, 7s. lOd. home ; 8s. 3d. abroad.)

ANIMAL FATS AND OILS: Their Practical Pro-
duction. Purification and Uses for a great Variety of Purposes.
Their Properties, Falsification and Examination. Translated
from the German of Louis EDGAR ANDES. Sixty-two Illustrations.
240 pp. Second Edition, Revised and Enlarged. Demy 8vo.
Price 10s. 6d. net. (Post free, 10s. lOd. home; lls. 3d. abroad.)

For contents of these books, see List I.

VEGETABLE FATS AND OILS: Their Practical

Preparation, Purification and Employment for Various Purposes,
their Properties, Adulteration and Examination. Translated
from the German of Louis EDGAR ANDES. Ninety-four Illus-
trations. 340 pp. Second Edition. Demy 8vo. Price 10s. 6d.
net. (Post free, 11s. home; 11s. 6d. abroad.)

EDIBLE FATS AND OILS : Their Composition, Manu-
facture and Analysis. By W. H. SIMMONS, B.Sc. (Lond.), and
C. A. MITCHELL, B.A. (Oxon.). Demy 8vo. 150 pp. Price
7s. 6d. net. (Post free, 7s. 9d. home ; 8s. abroad.)

(Essential Oils and Perfumes.)

THE CHEMISTRY OF ESSENTIAL OILS AND
ARTIFICIAL PERFUMES. By ERNEST J. PARRY,
B.Sc. (Lond.), F.I.C., F.C.S. Second Edition, Revised and
Enlarged. 552 pp. 20 Illustrations. Demy 8vo. Price 12s. 6d.
net. (Post free, 13s. home ; 13s. 6d. abroad.)

(Soap Manufacture.)

SOAPS. A Practical Manual of the Manufacture of
Domestic, Toilet and other Soaps. By GEORGE H. HURST, F.C.S.
2nd edition. 390 pp. 66 Illustrations. Demy 8vo. Price 12s. 6d.
net. (Post free, 13s. home ; 13s. 6d. abroad.)

TEXTILE SOAPS AND OILS. Handbook on the
Preparation, Properties and Analysis of the Soaps and Oils used
in Textile Manufacturing, Dyeing and Printing. By GEORGE
H. HURST, F.C.S. Crown 8vo. 195 pp. 1904. Price 5s. net.
(Post free, 5s. 4d. home ; 5s. 6d. abroad.)

THE HANDBOOK OF SOAP MANUFACTURE.

By WM. H. SIMMONS, B.Sc. (Lond.), F.C.S. and H. A. APPLETON.
Demy 8vo. 160 pp. 27 Illustrations. Price 8s. 6d. net. (Post
free, 8s. lOd. home ; 9s. abroad.) ,

MANUAL OF TOILET SOAPMAKING, including
Medicated Soaps, Stain-removing Soaps, Metal Polishing Soaps,
Soap Powders and Detergents. Translated from the German
of Dr. C. Deite. Demy quarto. 150 pages. 79 Illustrations.
Price 12s. 6d. net. (Post free, 13s. home ; 13s. 6d. abroad.)

(Cosmetical Preparations.)

COSMETICS: MANUFACTURE, EMPLOYMENT
AND TESTING OF ALL COSMETIC
MATERIALS AND COSMETIC SPECIALITIES.

Translated from the German of Dr. THEODOR ROLLER. Crown
8vo. 262 pp. Price 5s. net. (Post free, 5s. 4d. home; 5s. 6d.
abroad.)

(Glue, Bone Products and Manures.)

GLUE AND GLUE TESTING. By SAMUEL RIDEAL,

D.Sc. (Lond.), F.I.C. Fourteen Engravings. 144 pp. Demy
8vo. Price 10s. 6d. net. (Post free, 10s. lOd. home ; 11s. abroad.)

BONE PRODUCTS AND MANURES : An Account

of the most recent Improvements in the Manufacture of Fat,
Glue, Animal Charcoal, Size, Gelatine and Manures. By THOMAS
LAMBERT, Technical and Consulting Chemist. Illustrated by
Twenty-one Plans and Diagrams. 162 pp. Demy 8vo. Price
7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

(See also Chemical Manures, p. 9.)

(Chemicals, Waste Products, etc.)

REISSUE OF CHEMICA.L ESSAYS OF C. W.
SCHEELE. First Published in English in 1786.
Translated from the Academy of Sciences at Stockholm, with
Additions. 300 pp. Demy 8vo. Price 5s. net. (Post free, 5s. 6d.
home ; 5s. 9d. abroad.)

THE MANUFACTURE OF ALUM AND THE SUL-
PHATES AND OTHER SALTS OF ALUMINA
AND IRON. Their Uses and Applications as Mordants
in Dyeing and Calico^Printing, and their other Applications in
the Arts Manufactures, Sanitary Engineering, Agriculture and
Horticulture. Translated from the French of LUCIEN GESCH-
WIND. 195 Illustrations. 400 pp. Royal 8vo. Price 12s. 6d.
net. (Post free, 13s. home ; 13s. 6d. abroad.)

AMMONIA AND ITS COMPOUNDS : Their Manu-
facture and Uses. By CAMILLE VINCENT, Professor at the
Central School of Arts and Manufactures, Paris. Translated
from the French by M. J. SALTER. Royal 8vo. 114 pp. Thirty-
two Illustrations. Price 5s. net. (Post free, 5s. 4d. home ;
5s. 6d. abroad.)

CHEMICAL WORKS : Their Design, Erection, and
Equipment. By S. S. DYSON and S. S. CLARKSON. Royal 8vo.
220 pp. With 9 Folding Plates and {-0 Illustrations. Price 21s.
net. (Post free, 21s. 6d. home; 22s. abroad.)

MANUAL OF CHEMICAL ANALYSIS, as applied to
the Assay of Fuels, Ores, Metals, Alloys, Salts and other Mineral
Products. By E. PROST, D.Sc. Translated by J. CRUICKSHANK
SMITH, B.Sc. Royal 8vo. 300 pages. 44 Illustrations. Price
12s. 6d. net. (Post free, 13s. home ; 13s. 6d. abroad.)

TESTING OF CHEMICAL REAGENTS FOR
PURITY. Translated from the German of Dr. C
KRAUCH. Royal 8vo. 350 pages. Price 12s. 6d. net. (Post free
13s. home ; 13s. 6d. abroad.)

For contents of these books, see List I.

SHALE OILS AND TARS and their Products. By
Dr. W. SCHEITHAUER. Translated from the German. Demy 8vo.
190 pages. 70 Illustrations and 4 Diagrams. Price 8s. 6d. net.
(Post free, 8s. lOd. home ; 9s. abroad). [Just published.

INDUSTRIAL ALCOHOL. A Practical Manual on the
Production and Use of Alcohol for Industrial Purposes and for
Use as a Heating Agent, as an Illuminant and as a Source of
Motive Power. By J. G. MC!NTOSH, Lecturer on Manufacture
and Applications of Industrial Alcohol at The Polytechnic,
Regent Street, London. Demy 8vo. 1907. 250 pp. With 75
Illustrations and 25 Tables. Price 7s. 6d. net. (Post free, 7s. 9d.
home ; 8s. abroad.)

THE UTILISATION OF WASTE PRODUCTS. A

Treatise on the Rational Utilisation, Recovery and Treatment of
Waste Products of all kinds. By Dr. THEODOR KOLLER. Trans-
lated from the Second Revised German Edition. Twenty-two
Illustrations. Demy 8vo. 280 pp. Price 7s. 6d. net. (Post free,
7s. lOd. home ; 8s. 3d. abroad.)

ANALYSIS OP RESINS AND BALSAMS. Trans-
lated from the German of Dr. KARL DIETERICH. Demy 8vo.
340 pp. Price 7s. 6d. net. (Post free, 7s. lOd. home; 8s. 3d.
abroad.)

DISTILLATION OF RESINS, RESINATE LAKES
AND PIGMENTS, CARBON PIGMENTS AND
PIGMENTS FOR TYPEWRITING MACHINES,
MANIFOLDERS, ETC. By VICTOR SCHWEIZER.
Demy 8vo. 185 pages. 68 Illustrations. Price 7s. 6d. net. (Post
free, 8s. home ; 8s. 3d. abroad.)

DISINFECTION AND DISINFECTANTS. By Dr.

M. CHRISTIAN. Crown 8vo. [In the press.

(Agricultural Chemistry and Manures.)

MANUAL OF AGRICULTURAL CHEMISTRY. By

HERBERT INGLE, F.I.C., Late Lecturer on Agricultural Chemistry,
the Leeds University ; Lecturer in the Victoria University.
Third and Revised Edition. 400 pp. 16 Illustrations. Demy
8vo. Price 7s. 6d. net. (Post free, 8s. home; 8s. 6d. abroad.)

[Just published.

CHEMICAL MANURES. Translated from the French
of J. FRITSCH. Demy 8vo. Illustrated. 340 pp. Price 10s. 6d.
net. (Post free, lls. home; 11s. 6d. abroad.)

(See also Bone Products and Manures, p. 8.)

(Writing Inks and Sealing Waxes.)

INK MANUFACTURE: Including Writing, Copying
Lithographic, Marking, Stamping, and Laundry Inks. By
SIGMUND LEHNER. Three Illustrations. Crown 8vo. 162 pp.
Translated from the German of the Fifth Edition. Price 5s. net.
(Post free, 5s, 3d, home ; 5s. 6d. abroad.)

SEALING-WAXES, WAFERS AND OTHER
ADHESIVES FOR THE HOUSEHOLD, OFFICE,
WORKSHOP AND FACTORY. By H. C. STANDAGE.
Crown 8vo. 96 pp. Price 5s. net. (Post free, 5s. 3d. home ;
5s. 4d. abroad.)

(Lead Ores and Lead Compounds.)

LEAD AND ITS COMPOUNDS. By THOS. LAMBERT,
Technical and Consulting Chemist. Demy 8vo. 226 pp. Forty
Illustrations. Price 7s. 6d. net. (Post free, 7s. lOd. home;
8s. 3d. abroad.)

NOTES ON LEAD ORES : Their Distribution and Pro-
perties. By JAS. FAIRIE, F.G.S. Crown 8vo. 64 pages. Price
Is. net. (Post free, Is. 3d. home ; Is. 4d. abroad.)

(White Lead and Zinc White Paints, see p. 5.)

(Industrial Hygiene.)

THE RISKS AND DANGERS TO HEALTH OF
VARIOUS OCCUPATIONS AND THEIR PRE-
VENTION. By LEONARD A. PARRY, M.D., B.Sc.
(Lond.). 196 pp. Demy 8vo. Price 7s. 6d. net. (Post free,
7s. lOd. home ; 8s. abroad.)

(Industrial Uses of Air, Steam and
Water.)

DRYING BY MEANS OF AIR AND STEAM. Ex-
planations, Formulae, and Tables for Use in Practice. Trans-
lated from the German of E. HAUSBRAND. Two folding Diagrams
and Thirteen Tables. Crown 8vo. 72 pp. Price 5s. net. (Post
free, 5s. 3d. home ; 5s. 6d. abroad.)
(See also " Evaporating, Condensing and Cooling Apparatus," p. 19.)

PURE AIR, OZONE, AND WATER. A Practical
Treatise of their Utilisation and Value in Oil, Grease, Soap, Paint,
Glue and other Industries. By W. B. COWELL. Twelve Illus-
trations. Crown 8vo. 85 pp. Price 5s. net. (Post free, 5s. 3d.
home; 5s. 6d. abroad.)

THE INDUSTRIAL USES OF WATER. COMPOSI-
TION—EFFECTS—TROUBLES— REMEDIES-
RESIDUARY WATERS — PURIFICATION— AN-
ALYSIS. By H. DE LA Coux. Royal 8vo. Trans-
lated from the French and Revised by ARTHUR MORRIS. 364 pp.
135 Illustrations. Price 10s. 6d. net. (Post free, Us. home;
11s. 6d. abroad.)

(See Books on Smoke Prevention, Engineering and Metallurgy, p. 19, etc.)
For contents of these books, see List III,

11
(X Rays.)

PRACTICAL X RAY WORK. By FRANK T. ADDYMAN,
B.Sc. (Lond.), F.I.C., Member of the Roentgen Society of London ;
Radiographer to St. George's Hospital ; Demonstrator of Physics
and Chemistry, and Teacher of Radiography in St. George's
Hospital Medical School. Demy 8vo. Twelve Plates from
Photographs of X Ray Work. Fifty-two Illustrations. 200 pp.
Price 10s. 6d. net. (Post free, 10s. lOd. home; 11s. 3d. abroad.)

( I ndia= Rubber and Qutta Percha.)

INDIA-RUBBER AND GUTTA PERCHA. Second
English Edition, Revised and Enlarged. Based on the French
work of T. SEELIGMANN, G. LAMY TORRILHON and H. FALCONNET
by JOHN GEDDES MC!NTOSH. Royal 8vo. 100 Illustrations. 400
pages. Price 12s. 6d. net. (Post free, 13s. home; 13s. 6d.
abroad.)

(Leather Trades.)

THE LEATHER WORKER'S MANUAL. Being a

Compendium of Practical Recipes and Working Formulae for
Curriers, Bootmakers, Leather ^Dressers, Blacking Manufac-
turers, Saddlers, Fancy Leather Workers. By H. C. STANDAGE.
Demy 8vo. 165 pp. Price 7s. 6d. net. (Post free, 7s. lOd. home;
8s. abroad.)

(See also Manufacture of Shoe Polishes, Leather Dressings, etc., p. 6.)

(Pottery, Bricks, Tiles, Glass, etc.)

MODERN BRICKMAKING. By ALFRED B. SEARLE,
Royal 8vo. 440 pages. 260 Illustrations. Price 12s. 6d. net.
(Post free, 13s. home; 13s. 6d. abroad.)

THE MANUAL OP PRACTICAL POTTING. Com-

piled by Experts, and Edited by CHAS. F. BINNS. Third Edition,
Revised and Enlarged. 200 pp. Demy 8vo. Price 17s. 6d. net.
(Post free, 17s. lOd. home; 18s. 3d. abroad.)

POTTERY DECORATING. A Description of all the Pro-
cesses for Decorating Pottery and Porcelain. By R. HAINBACH.
Translated from the German. Crown 8vo. 250 pp. Twenty-
two Illustrations. Price 7s. 6d. net. (Post free, 7s. lOd. home ;
8s. abroad.)

A TREATISE ON CERAMIC INDUSTRIES. A

Complete Manual for Pottery, Tile, and Brick Manufacturers. By
EMILE BOURRY. A Revised Translation from the French, with
some Critical Notes by ALFRED B. SEARLE. Demy 8vo. 308
Illustrations. 460 pp. Price 12s. 6d. net. (Post free, 13s. home;
13s. 6d. abroad.)

ARCHITECTURAL POTTERY. Bricks, Tiles, Pipes,
Enamelled Terra-cottas, Ordinary and Incrusted Quarries, Stone-
ware Mosaics, Faiences and Architectural Stoneware. By LEON
LEF£VRE. Translated from the French by K. H. BIRD, M.A.,
and W. MOORE BINNS. With Five Plates. 950 Illustrations in
the Text, and numerous estimates. 500 pp., royal 8vo. Price
15s. net. (Post free, 15s. 6d. home; 16s. 6d. abroad.)

CERAMIC TECHNOLOGY: Being some Aspects of
Technical Science as Applied to Pottery Manufacture. Edited
by CHARLES F. BINNS. 100 pp. Demy 8vo. Price 12s. 6d. net.
(Post free, 12s. lOd. home ; 13s. abroad.)

THE ART OF RIVETING GLASS, CHINA AND
EARTHENWARE. By J. HOWARTH. Second
Edition. Paper Cover. Pricels.net. (By post, home or abroad,
Is. Id.)

NOTES ON POTTERY CLAYS. The Distribution,
Properties, Uses and Analyses of Ball Clays, China Clays and
China Stone. By JAS. FAIRIE, F.G.S. 132 pp. Crown 8vo.
Price 3s. 6d. net. (Post free, 3s. 9d. home ; 3s. lOd. abroad.)

HOW TO ANALYSE CLAY. By H. M. Ashby. Demy
8vo. 72 Pages. 20 Illustrations. Price 3s. 6d. net. (Post free,
3s. 9d. home ; 3s. lOd/abroad.)

A Reissue of

THE HISTORY OF THE STAFFORDSHIRE POT-
TERIES; AND THE RISE AND PROGRESS
OF THE MANUFACTURE OF POTTERY AND
PORCELAIN. With References to Genuine Specimens,
and Notices of Eminent Potters. By SIMEON SHAW. (Originally
published in 1829.) 265 pp. Demy 8vo. Price 5s. net. (Post
free, 5s. 4d. home ; 5s. 9d. abroad.)

A Reissue of

THE CHEMISTRY OF THE SEVERAL NATURAL
AND ARTIFICIAL HETEROGENEOUS COM-
POUNDS USED IN MANUFACTURING POR-
CELAIN, GLASS AND POTTERY. By SIMEON
SHAW. (Originally published in 1837.) 750 pp. Royal 8vo.
Price 10s. net. (Post free, 10s. 6d. home ; 12s. abroad.)

BRITISH POTTERY MARKS. By G. WOOLLISCROFT
RHEAD. Demy 8vo. 310 pp. With over Twelve-hundred Illus-
trations of Marks. Price 7s. 6d. net. (Post free, 8s. home ;
8s. 3d. abroad.) .

For contents of these books, see List III.

(Glassware, Glass Staining and Painting.)

RECIPES FOR FLINT GLASS MAKING. By a

British Glass Master and Mixer. Sixty Recipes. Being Leaves
from the Mixing Book of several experts in the Flint Glass Trade,
containing up-to-date recipes and valuable information as to
Crystal, Demi-crystal and Coloured Glass in its many, varieties.
It contains the recipes for cheap metal suited to pressing, blow-
ing, etc., as well as the most costly crystal and ruby. Second
Edition. Crown 8vo. Price 10s. 6d. net. (Post free, 10s. 9d.
home ; 10s. lOd. abroad.)

A TREATISE ON THE ART OF GLASS PAINT-
ING. Prefaced with a Review of Ancient Glass. By
ERNEST R. SUPPLING. With One Coloured Plate and Thirty-
seven Illustrations. ' Demy 8vo. 140 pp. Price 7s. 6d. net.
(Post free, 7s. lOd. home ; 8s. abroad.)

(Paper Making, Paper Dyeing, and
Testing.)

THE DYEING OF PAPER PULP. A Practical

Treatise for the use of Papermakers, Paperstainers, Students
and others. By JULIUS ERFURT, Manager of a Paper Mill.
Translated into English and Edited with Additions by JULIUS
HUBNER, F.C.S., Lecturer on Papermaking at the Manchester
Municipal Technical School. With illustrations and 157 patterns
of paper dyed in the pulp. Royal 8vo, 180 pp. Price 15s. net.
(Post free, 15s. 6d. home; 16s. 6d. abroad).

THE PAPER MILL CHEMIST. By HENRY P. STEVENS,

M.A., Ph.D., F.I.C. Royal 12mo. 60 illustrations. 300 pp.
Price 7s. 6d. net. (Post free, 7s. 9d. home ; 7s. lOd. abroad.)

THE TREATMENT OF PAPER FOR SPECIAL
PURPOSES. By L. E, ANDES. Translated from the
German. Crown 8vo. 48 Illustrations. 250 pp. Price 6s. net.
(Post free, 6s. 4d. home ; 6s. 6d. abroad.)

(Enamelling on Metal.)

ENAMELS AND ENAMELLING. For Enamel

Makers, Workers in Gold and Silver, and Manufacturers of
Objects of Art. By PAUL RANDAU. Second and Revised
Edition. Translated from the German. With 16 Illustrations.
Demy 8vo. 180 pp. Price 10s. 6d. net. (Post free, 10s. lOd.
home; 11s. abroad.) [Just published.

THE ART OF ENAMELLING ON METAL. By

W. NORMAN BROWN. Twenty-eight Illustrations. Crown 8vo.
60 pp. Price 2s. 6d. net. (Post free, 2s. 9d. home and abroad.)

(Textile and Dyeing Subjects.)

THE FINISHING OF TEXTILE FABRICS (Woollen,
Worsted, Union and other Cloths). By ROBERTS BEAUMONT,
M.Sc., M.I. Mech.E., Professor of Textile Industries, the Univer-
sity of Leeds ; Author of " Colour in Woven Design " ; " Woollen
and Worsted Cloth Manufacture"; "Woven Fabrics at the
World's Fair" ; Vice-President of the Jury of Award at the Paris
Exhibition, 1900 ; Inspector of Textile Institutes ; Society of
Arts Silver Medallist ; Honorary Medallist of the City and Guilds
of London Institute. With 150 Illustrations of Fibres, Yarns
and Fabrics, also Sectional and other Drawings of Finishing
Machinery Demy 8vo. 260 pp. Price 10s. 6d. net. (Post free,
10s. lOd. home; 11s. 3d. abroad.)

FIBRES USED IN TEXTILE AND ALLIED IN-
DUSTRIES. By C. AINSWORTH MITCHELL, B.A.
(Oxon.), F.I.C., and R. M. PRIDEAUX, F.I.C. With 66 Illustra-
tions specially drawn direct from the Fibres. Demy 8vo.
200 pp. Price 7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

DRESSINGS AND FINISHINGS FOR TEXTILE
FABRICS AND THEIR APPLICATION. De-
scription of all the Materials used in Dressing Textiles : Their
Special Properties, the preparation of Dressings and their em-
ployment in Finishing Linen, Cotton, Woollen and Silk Fabrics.
Fireproof and Waterproof Dressings, together with the principal
machinery employed. Translated from the Third German
Edition of FRIEDRICH POLLEYN. Demy 8vo. 280 pp. Sixty
Illustrations. Price 7s. 6d. net. (Post free, 7s. lOd. home ;
8s. abroad.)

THE CHEMICAL TECHNOLOGY OF TEXTILE
FIBRES ; Their Origin, Structure, Preparation, Wash-
ing, Bleaching, Dyeing, Printing and Dressing. By Dr. GEORG
VON GEORGIEVICS. Translated from the German by CHARLES
SALTER. 320 pp. Forty-seven Illustrations. Royal 8vo. Price
10s. 6d. net. (Post free, 11s. home ; 11s. 3d. abroad.)

POWER-LOOM WEAVING AND YARN NUMBER-
ING, According to Various Systems, with Conversion
Tables. Translated from the German of ANTHON GRUNER. With
Twenty-six Diagrams in Colours. 150 pp. Crown Svo. Price
7s. 6d. net. (Post free, 7s. 9d. home ; 8s. abroad.)

TEXTILE RAW MATERIALS AND THEIR CON-
VERSION INTO YARNS. (The Study of the Raw
Materials and the Technology of the Spinning Process.) By
JULIUS ZIPSER. Translated from German by CHARLES SALTER.
302 Illustrations. 500 pp. Demy Svo. Price 10s. 6d. net.
(Post free, 11s. home ; 11s. 6d. abroad.)

For contents of these books, see List II.

15
GRAMMAR OF TEXTILE DESIGN. By H. NISBET,

Weaving and Designing Master, Bolton Municipal Technical
School. Demy 8vo. 280 pp. 490 Illustrations and Diagrams.
Price 6s. net. (Post free, 6s. 4d. home ; 6s. 6d. abroad.)

ART NEEDLEWORK AND DESIGN. POINT
LACE. A Manual of Applied Art for Secondary Schools
and Continuation Classes. By M. E. WILKINSON. Oblong
quarto. With 22 Plates. Bound in Art Linen. Price 3s. 6d.
net. (Post free, 3s. lOd. home ; 4s. abroad.)

HOME LACE-MAKING. A Handbook for Teachers and
Pupils. By M. E. W. MILROY. Crown 8vo. 64 pp. With 3
Plates and 9 Diagrams. Price Is. net. (Post free, Is. 3d. home ;
Is. 4d. abroad.)

THE CHEMISTRY OF HAT MANUFACTURING.

Lectures delivered before the Hat Manufacturers' Association.
By WATSON SMITH, F.C.S., F.I.C. Revised and Edited by
ALBERT SHONK. Crown 8vo. 132 pp. 16 Illustrations. Price
7s. 6d. net. (Post free, 7s. 9d. home ; 7s. lOd. abroad.)

THE TECHNICAL TESTING OF YARNS AND
TEXTILE FABRICS. With Reference to Official
Specifications. Translated from the German of Dr. J. HERZFELD.
Second Edition. Sixty-nine Illustrations. 200 pp. Demy 8vo.
Price 10s. 6d. net. (Post free, 10s. lOd. home; 11s. abroad.)

DECORATIVE AND FANCY TEXTILE FABRICS.

By R. T. LORD. For Manufacturers and Designers of Carpets,

Damask, Dress and all Textile Fabrics. 200 pp. Demy 8vo.

132 Designs and Illustrations. Price 7s. 6d. net. (Post free,
7s. lOd. home ; 8s. abroad.)

THEORY AND PRACTICE OF DAMASK WEAV-
ING. By H. KINZER and K. WALTER. Royal 8vo.
Eighteen Folding Plates. Six Illustrations. Translated from
the German. 110pp. Prlce8s.6d.net. (Post free, 9s. home;
9s. 6d. abroad.)

FAULTS IN THE MANUFACTURE OF WOOLLEN
GOODS AND THEIR PREVENTION. By

NICOLAS REISER. Translated from the Second German Edition.
Crown 8vo. Sixty-three Illustrations. 170 pp. Price 5s. net.
(Post free, 5s. 4d. home ; 5s. 6d. abroad.)

SPINNING AND WEAVING CALCULATIONS,

especially relating to Woollens. From the German of N.
REISER. Thirty-four Illustrations. Tables. 160 pp. Demy
8vo. 1904. Price 10s. 6d. net. (Post free, 10s. lOd. home; 11s.
abroad.)

ANALYSIS OF WOVEN FABRICS. By A. F. BARKER

and E. MIDGLEY. Demy 8vo. About 200 pages [In the press.

WATERPROOFING OF FABRICS. By Dr. S. MIER-
ZINSKI. Crown 8vo. 104 pp. 29 Illus. Price 5s. net. (Post
free, 5s. 3d. home ; 5s. 4d. abroad.)

HOW TO MAKE A WOOLLEN MILL PAY. By

JOHN MACKIE. Crown 8vo. 76 pp. Price 3s. 6d. net. (Post
free, 3s. 9d. home; 3s. lOd. abroad.)

YARN AND WARP SIZING IN ALL ITS
BRANCHES. Translated from the German of CARL
KRETSCHMAR. Royal 8vo. 123 Illustrations. 150 pp. Price
10s. 6d. net. (Post free, 10s. lOd. home; 11s. abroad.)

(For " Textile Soaps and Oils " see p. 7.)

(Dyeing, Colour Printing, Matching
and Dye = stuffs.)

THE COLOUR PRINTING OP CARPET YARNS.

Manual for Colour Chemists and Textile Printers. By DAVID
PATERSON, F.C.S. Seventeen Illustrations. 136 pp. Demy
8vo. Price 7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

THE SCIENCE OF COLOUR MIXING. A Manual

intended for the use of Dyers, Calico Printers and Colour
Chemists. By DAVID PATERSON, F.C.S. Forty-one Illustrations.
Five Coloured Plates, and Four Plates showing Eleven Dyed
Specimens Of Fabrics. 132 pp. Demy 8vo. Price 7s. 6d. net.
(Post free, 7s. lOd. home ; 8s. abroad.)

DYERS' MATERIALS : An Introduction to the Examina-
tion, Evaluation and Application of the most important Sub-
stances used in Dyeing, Printing, Bleaching and Finishing. By
PAUL HEERMAN, Ph.D. Translated from the German by A. C.
WRIGHT, M.A. (Oxon)., B.Sc. (Lond.). Twenty-four Illustrations.
Crown 8vo. 150 pp. Price 5s. net. (Post free, 5s. 4d. home ;
5s. 6d. abroad.)

COLOUR MATCHING ON TEXTILES. A Manual

intended for the use of Students of Colour Chemistry, Dyeing and
Textile Printing. By DAVID PATERSON, F.C.S. Coloured Frontis-
piece. Twenty-nine Illustrations and Fourteen Specimens Of
Dyed Fabrics. Demy 8vo. 132 pp. Price 7s. 6d. net. (Post
free, 7s. lOd. home ; 8s. abroad.)

COLOUR : A HANDBOOK OF THE THEORY OF
COLOUR. By GEORGE H. HURST, F.C.S. With Ten

Coloured Plates and Seventy-two Illustrations. 160pp. Demy
8vo. Price 7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

For contents of these books, see List II.

Reissue of

THE ART OF DYEING WOOL, SILK AND
COTTON. Translated from the French of M. HELLOT,
M. MACQUER and M. LE PILEUR D'APLIGNY. First Published in
English in 1789. Six Plates. Demy 8vo. 446pp. Price5s.net.
(Post' free, 5s. 6d. home; 6s. abroad.)

THE CHEMISTRY OF DYE-STUFFS. By Dr. GEORG
VON GEORGIEVICS. Translated from the Second German Edition.
412 pp. Demy 8vo. Price 10s. 6d. net. (Post free, 11s. home;
11s 6d. abroad.)

THE DYEING OF COTTON FABRICS : A Practical
Handbook for the Dyer and Student. By FRANKLIN BEECH,
Practical Colpurist and Chemist. 272 pp. Forty-four Illus-
trations of Bleaching and Dyeing Machinery. Demy 8vo. Price
7s. 6d. net. (Post free, 7s. lOd. home; 8s. abroad.)

THE DYEING OF WOOLLEN FABRICS. By

FRANKLIN BEECH, Practical Colourist and Chemist. Thirty-
three Illustrations. Demy 8vo. 228 pp. Price 7s. 6d. net.
(Post free, 7s. lOd. home ; 8s. abroad.)

(Silk Manufacture.)

SILK THROWING AND WASTE SILK SPIN-
NING. By HOLLINS RAYrfteR. Demy 8vo. 170 pp.
117 Illus. Price 5s. net. (Post free, 5s. 4d. home ; 5s. 6d. abroad.)

(Bleaching and Bleaching Agents.)

A PRACTICAL TREATISE ON THE BLEACHING
OF LINEN AND COTTON YARN AND FABRICS.

By L. TAILFER, Chemical and Mechanical Engineer. Trans-
lated from the French by JOHN GEDDES MC!NTOSH. Demy 8vo.
303 pp. Twenty Illus. Price 12s. 6d. net. (Post free, 13s.
home; 13s. 6d. abroad.)

MODERN BLEACHING AGENTS AND DETER-
GENTS. By Professor MAX BOTTLER. Translated
from the German. Crown 8vo. 16 Illustrations. 160 pages.
Price 5s. net. (Post free, 5s. 3d. home ; 5s. 6d. abroad.)

(Cotton Spinning, Cotton Waste and
Cotton Combing.)

COTTON SPINNING (First Year). By THOMAS
THORNLEY, Spinning Master, Bolton Technical School. 160 pp.
Eighty-four Illustrations. Crown 8vo. Second Impression.
Price 3s. net. (Post free, 3s. 4d. home; 3s. 6d. abroad.)

COTTON SPINNING (Intermediate, or Second Year).
By THOMAS THORNLEY. Second Impression. 180 pp. Seventy
Illustrations. Crown 8vo. Price 5s. net. (Post free, 5s. 4d.
home ; 5s. 6d. abroad.)

COTTON SPINNING (Honours, or Third Year). By
THOMAS THORNLEY. 216 pp Seventy-four Illustrations.
Crown 8vo. Second Edition. Price 5s. net. (Post free, 5s. 4d.
home; 5s. 6d. abroad.)

COTTON COMBING MACHINES. By THOS. THORN-
LEY, Spinning Master, Technical School, Bolton. Demy 8vo.
117 Illustrations. 300 pp. Price 7s. 6d. net. (Post free, 8s.
home ; 8s. 6d. abroad.)

COTTON WASTE : Its Production, Characteristics,
Regulation, Opening, Carding, Spinning and Weaving. By THOMAS
THORNLEY. Demy 8vo. 286 pages. 60 Illustrations. Price 7s. 6d.
net. (Post free, 7s. lOd. home ; 8s. abroad.) [Just published.

THE RING SPINNING FRAME : GUIDE FOR
OVERLOOKERS AND STUDENTS. By N. BOOTH.
Crown 8vo. 76 pages. Price3s.net. (Post free, 3s. 3d. home;
3s. 6d. abroad.)

(Flax, Hemp and Jute Spinning.)

MODERN FLAX, HEMP AND JUTE SPINNING
AND TWISTING. A Practical Handbook for the use
of Flax, Hemp and Jute Spinners, Thread, Twine and Rope
Makers. By HERBERT R. CARTER, Mill Manager, Textile Expert
and Engineer, Examiner in Flax Spinning to the City and Guilds
of London Institute. Demy 8vo. 1907. With 92 Illustrations.
200 pp. Price 7s. 6d. net. (Post free, 7s. 9d. home ; 8s. abroad.)

(Collieries and Mines.)

RECOVERY WORK AFTER PIT FIRES. By ROBERT
LAMPRECHT, Mining Engineer and Manager. Translated from
the German. Illustrated by Six large Plates, containing Seventy-
six Illustrations. 175 pp. Demy 8vo. Price 10s. 6d. net. (Post
free, 10s. lOd. home; 11s. abroad.) .

VENTILATION IN MINES. By ROBERT WABNER,
Mining Engineer. Translated from the German. Royal 8vo.
Thirty Plates and Twenty-two Illustrations. 240 pp. Price
10s. 6d. net. (Post free, 11s. home ; 11s. 3d. abroad.)

HAULAGE ?AND WINDING APPLIANCES USED
IN MINES. By CARL VOLK. Translated from the
German. Royal 8vo. With Six Plates and 148 Illustrations.
150 pp. Price 8s. 6d. net. (Post free, 9s. home ; 9s. 3d. abroad.)

THE ELECTRICAL EQUIPMENT OF COLLIERIES.

By W. GALLOWAY DUNCAN, Electrical and Mechanical Engineer,
Member of the Institution of Mining Engineers, Head of the
Government School of Engineering, Dacca, India ; and DAVID
PENMAN, Certificated Colliery Manager, Lecturer in Mining to
Fife County Committee. Demy 8vo. 310 pp. 155 Illustrations
and Diagrams. Price 10s. 6d. net. (Post free, 11s. home ; 11s. 3d.
abroad.)

For contents of these books, see List III.

(Dental Metallurgy.)

DENTAL METALLURGY: MANUAL FOR STU-
DENTS AND DENTISTS. By A. B. GRIFFITHS,

Ph.D. Demy 8vo. Thirty-six Illustrations. 200 pp. Price
7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

(Engineering, Smoke Prevention and
Metallurgy.)

THE PREVENTION OF SMOKE. Combined with
the Economical Combustion of Fuel. By W. C. POPPLEWELL,
M.Sc., A.M. Inst., C.E., Consulting Engineer. Forty-six Illus-
trations. 190 pp. Demy 8vo. Price 7s. 6d. net. (Post free,
7s. lOd. home ; 8s. 3d. abroad.)

GAS AND COAL DUST FIRING. A Critical Review

of the Various Appliances Patented in Germany for this purpose
since 1885. By ALBERT PUTSCH. 130 pp. Demy 8vo. Trans-
lated from the German. With 103 Illustrations. Price 5s. net.
(Post free, 5s. 4d. home ; 5s. 6d. abroad.)

THE HARDENING AND TEMPERING OF STEEL
IN THEORY AND PRACTICE. By FRIDOLIN
REISER. Translated from the German of the Third Edition.
Crown 8vo. 120 pp. Price Ss.yiet. (Post free, 5s. 3d. home;
5s. 4d. abroad.)

SIDEROLOGY: THE SCIENCE OF IRON (The

Constitution of Iron Alloys and Slags). Translated from
German of HANNS FREIHERR v. JUPTNER. 350 pp. Demy 8vo.
Eleven Plates and Ten Illustrations. Price 10s. 6d. net. (Post
free, 11s. home; 11s. 6d. abroad.)

EVAPORATING, CONDENSING AND COOLING
APPARATUS. Explanations, Formulae and Tables
for Use in Practice. By E. HAUSBRAND, Engineer. Translated
by A. C. WRIGHT, M.A. (Oxon.), B.Sc., (Lond.). With Twenty-
one Illustrations and Seventy-six Tables. 400 pp. Demy 8vo.
Price 10s. 6d. net. (Post free, 11s. home; 11s. 6d. abroad.)

(The "Broadway" Series of Engineering
Handbooks.)

One Uniform Size : Narrow Crown 8vo. (Pocket Size.)
VOLUME I.— ELEMENTARY PRINCIPLES OF RE-
INFORCED CONCRETE CONSTRUCTION. By

EWART S. ANDREWS, B.Sc. Eng. (Lond.). 200 pages. With 57
Illustrations. Numerous Tables and Worked Examples. Price
3s. net. (Post free, 3s. 3d. home ; 3s. 6d. abroad.)

VOLUME II.— GAS AND OIL ENGINES. By A.

KIRSCHKE. Translated and Revised from the German, and
adapted to English practice. 160 pages. 55 Illustrations.
Price 3s. net. (Post free, 3s. 3d. home ; 3s. 6d. abroad.)

VOLUME III. — IRON AND STEEL CONSTRUC-
TIONAL WORK. By K. SCHINDLER. Translated
and Revised from the German, and adapted to English practice.
140 pages. 115 Illustrations. Price 3s. 6d. net. (Post tree,
3s. 9d. home ; 4s. abroad.)

VOLUME IV.— TOOTHED GEARING. By G. T. WHITE,
B.Sc. (Lond.). 220 pages. 136 Illustrations. Price 3s. 6d. net.
(Post free, 3s. 9d. home ; 4s. abroad.)

VOLUME V.— STEAM TURBINES : Their Theory and
Construction. By H. WILDA. Translated and Revised from the
German, and adapted to English practice. 200 pages. 104 Illus-
trations. Price 3s. 6d. net. (Post free, 3s. 9d. home ; 4s. abroad.)

[J list published.

VOLUME VI. — CRANES AND HOISTS. By H.
WILDA. [In the press.

VOLUME VII. — FOUNDRY MACHINERY. By E.
TREIBER. [In the press.

VOLUME VIII.— THE CALCULUS FOR ENGINEERS.
By EWART S. ANDREWS, B.Sc. Eng. (Lond.), and H. BRYON
HEYWOOD, B.Sc. (Lond.). [In preparation.

VOLUME IX.— ILLUMINATION AND LIGHTING.

By A. BLOK, B.Sc. [In preparation.

VOLUME X. — MOTOR CAR MECHANISM. By

W. E. DOMMETT. [In preparation.

(Sanitary Plumbing, Electric Wiring,
Metal Work, etc.)

EXTERNAL PLUMBING WORK. A Treatise on
Lead Work for Roofs. By JOHN W. HART, R.P.C. 180 Illustra-
tions. 272 pp. Demy 8vo. Second Edition Revised. Price
7s. 6d. net. (Post free, 7s. lOd. home; 8s. abroad.)

HINTS TO PLUMBERS ON JOINT WIPING, PIPE
BENDING AND LEAD BURNING. Third Edition,
Revised and Corrected, By JOHN W. HART, R.P.C. 184 Illus-
trations. 313 pp. Demy 8vo. Price 7s. 6d. net. (Post free,
8s. home ; 8s. 6d. abroad.)

SANITARY PLUMBING AND DRAINAGE. By
JOHN W. HART. Demy 8vo. With 208 Illustrations. 250 pp.
1904. Price 7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

ELECTRIC WIRING AND FITTING. By SYDNEY R
WALKER, R.N., M.I.E.E., M.I.Min.E., A.M.Inst.C.E., etc., etc.
Crown 8vo. 150 pp. With Illustrations and Tables. Price 5s.
net. (Post free, 5s. 3d. home ; 5s. 6d. abroad.)

THE PRINCIPLES AND PRACTICE OP DIPPING,
BURNISHING, LACQUERING AND BRONZ-
ING BRASS WARE. By W. NORMAN BROWN. 48
pp. Crown 8vo. Price 3s. net. (Post free, 3s. 3d. home and
abroad.)

For contents of these books, see List III.

THE DEVELOPMENT OF THE INCANDESCENT
ELECTRIC LAMP. By G. BASIL BARHAM, A.M.I. E.E.
Demy 8vo. 200 pages. 2 Plates, 25 Illustrations and 10 Tables.
Price 5s. net. (Post free, 5s. 4d. home ; 5s. 6d. abroad.)

[Just published.

WIRING CALCULATIONS FOR ELECTRIC
LIGHT AND POWER INSTALLATIONS. A

Practical Handbook containing Wiring Tables, Rules, and
Formulae for the Use of Architects, Engineers, Mining Engineers,
and Electricians, Wiring Contractors and Wiremen, etc. By G.
W. LUMMIS PATERSON. Crown 8vo. 96 pages. 35 Tables.
Price 5s. net. (Post free, 5s. 3d. home ; 5s. 6d. abroad.)

[Just published.

A HANDBOOK ON JAPANNING. For Ironware,
Tinware, > and Wood, etc. By WILLIAM NORMAN BROWN.
Second Edition. 70 pages. 13 Illustrations. Crown 8vo. Price
3s. 6d. net. (Post free, 3s. 9d. home ; 4s. abroad.)

[Just published.

THE PRINCIPLES OF HOT WATER SUPPLY. By
JOHN W. HART, R.P.C. With 129 Illustrations. 177 pp. Demy
8vo. Price 7s. 6d. net. (Post free, 7s. lOd. home ; 8s. abroad.)

(Brewing and Botanical.)

HOPS IN THEIR BOTANICAL, AGRICULTURAL
AND TECHNICAL AfcPECT, AND AS AN
ARTICLE OF COMMERCE. By EMMANUEL GROSS,
Professor at the Higher Agricultural College, Tetschen-Liebwerd.
Translated from the German. Seventy-eight Illustrations. 340
pp. Demy 8vo. Price 10s. 6d. net. (Post free, 11s. home ;
11s. 6d. abroad.)

INSECTICIDES, FUNGICIDES AND WEED-
KILLERS. By E. BOURCART, D.Sc. Translated from
the French. Revised and Adapted to British Standards and
Practice. Demy 8vo. 450 pages, 83 Tables, and 12 Illustrations.
Price 12s. 6d. net. (Post free, 13s. home ; 13s. 6d. abroad.)

(For Agricultural Chemistry, see p. 9.) [Just published.

(Wood Products, Timber and Wood
Waste.)

WOOD PRODUCTS : DISTILLATES AND EX-
TRACTS. By P. DUMESNY, Chemical Engineer,
Expert before the Lyons Commercial Tribunal, Member of the
International Association of Leather Chemists; and J. NOYER.
Translated from the French by DONALD GRANT. Royal 8vo.
320 pp. 103 Illustrations and Numerous Tables. Price 10s. 6d.
net. (Post free, 11s. home ; 11s. 6d. abroad.)

TIMBER : A Comprehensive Study of Wood in all its
Aspects (Commercial and Botanical), showing the different
Applications and Uses of Timber in Various Trades, etc. Trans-
lated from the French of PAUL CHARPENTIER. Royal 8vo. 437
pp. 178 Illustrations. Price 12s. 6d. net. (Post free, 13s.
home; 14s. abroad.)

THE UTILISATION OP WOOD WASTE. Trans-
lated from the German of ERNST HUBBARD. Crown 8vo. 192
pp. Fifty Illustrations. Price 5s. net. (Post free, 5s. 4d. home
5s. 6d. abroad.)

(See also Utilisation of Waste Products, p. 9.)

(Building and Architecture.)

ORNAMENTAL CEMENT WORK. By OLIVER
WHEATLEY. Demy 8vo. 83 Illustrations. 128 pp. Price 5s.
net. (Post free, 5s. 4d. home ; 5s. 6d. abroad.)

THE PREVENTION OF DAMPNESS IN BUILD-
INGS ; with Remarks on the Causes, Nature and
Effects of Saline, Efflorescences and Dry-rot, for Architects,
Builders, Overseers, Plasterers, Painters and House Owners.
By ADOLF WILHELM KEIM. Translated from the German of the
second revised Edition by M. J. SALTER, F.I.C., F.C.S. Eight
Coloured Plates and Thirteen Illustrations. Crown 8vo. 115
pp. Price 5s. net. (Post free, 5s. 3d. home ; 5s. 4d. abroad.)

HANDBOOK OF TECHNICAL TERMS USED IN
ARCHITECTURE AND BUILDING, AND THEIR
ALLIED TRADES AND SUBJECTS. By AUGUS-
TINE C. PASSMORE. Demy 8vo. 380 pp. Price 7s. 6d. net.
(Post free, 8s. home ; 8s. 6d. abroad.)

(Foods, Drugs and Sweetmeats.)

FOOD AND DRUGS. By E. J. PARRY, B.Sc., F.I.C., F.C.S.
Volume I. The Analysis of Food and Drugs (Chemical and

Microscopical). Royal 8vo. 724 pp. Price 21s. net. (Post

free, 21s. 8d. home ; 22s. abroad.)
Volume II. The Sale of Food and Drugs Acts, 1875-1907.

Royal 8vo. 184 pp. Price 7s. 6d. net. (Post free, 7s. lOd.

home ; 8s. abroad.)

THE MANUFACTURE OF PRESERVED FOODS
AND SWEETMEATS. By A. HAUSNER. With
Twenty-eight Illustrations. Translated from the German of the
third enlarged Edition. Second English Edition. Crown 8vo. 225
pp. Price 7s. 6d. net. (Post free, 7s. 9d. home ; 7s. lOd. abroad.)

RECIPES FOR THE PRESERVING OF FRUIT,
VEGETABLES AND MEAT. By E. WAGNER.
Translated from the German. Crown 8vo. 125 pp. With 14
Illustrations. Price 5s. net. (Post free, 5s. 3d. home ; 5s. 4d.
abroad.)

For contents of these books, see L st III.

(Dyeing Fancy Goods.)

THE ART OF DYEING AND STAINING MARBLE,
ARTIFICIAL STONE, BONE, HORN, IVORY
AND WOOD, AND OF IMITATING ALL SORTS
OF WOOD. A Practical Handbook for the Use of

Joiners, Turners, Manufacturers of Fancy Goods, Stick and
Umbrella Makers, Comb Makers, etc. Translated from the
German of D. H. SOXHLET, Technical Chemist. Crown 8vo.
168 pp. Price 5s. net. (Post free, 5s. 3d. home; 5s. 4d. abroad.)

(Celluloid.)

CELLULOID : Its Raw Material, Manufacture, Properties
and Uses. A Handbook for Manufacturers of Celluloid and
Celluloid Articles, and all Industries using Celluloid ; also for
Dentists and Teeth Specialists. By Dr. Fr. BOCKMANN, Tech-
nical Chemist. Translated from the Third Revised German
Edition. Crown 8vo. 120 pp. With 49 Illustrations. Price 5s.
net. (Post free, 5s. 3d. home ; 5s. 4d. abroad.)

(Lithography, Printing and
Engraving.)

PRACTICAL LITHOGRAPHY. By ALFRED SEYMOUR.
Demy 8vo. With Frontispiece and 33 Illus. 120 pp. Price 5s.
net. (Post free, 5s. 4d. home ; 5s. 6d. abroad.)

PRINTERS' AND STATIONERS' READY
RECKONER AND COMPENDIUM. Compiled by
VICTOR GRAHAM. Crown 8vo. 112pp. 1904. Price3s.6d.net.
(Post free, 3s. 9d. home ; 3s. lOd. abroad.)

ENGRAVING FOR ILLUSTRATION. HISTORI-
CAL AND PRACTICAL NOTES. By J. KIRKBRIDE.
72 pp. Two Plates and 6 Illustrations. Crown 8vo. Price
2s. 6d. net. (Post free, 2s. 9d. home ; 2s. lOd. abroad.)
(For Printing Inks, see p. 4.)

(Bookbinding.)

PRACTICAL BOOKBINDING. By PAUL ADAM.
Translated from the German. Crown 8vo. 180 pp. 127 Illus-
trations. Price 5s. net. (Post free, 5s. 4d. home ; 5s. 6d. abroad.)

(Sugar Refining.)

THE TECHNOLOGY OF SUGAR: Practical Treatise
on the Modern Methods of Manufacture of Sugar from the Sugar
Cane and Sugar Beet. By JOHN GEDDES MC!NTOSH. Second
Revised and Enlarged Edition. Demy 8vo. Fully Illustrated.
436 pp. Seventy-six Tables. 1906. Price 10s. 6d. net. (Post
free, 11s. home; 11s. 6d. abroad.)

LS& •« Elaborating, Condensing, etc., Apparatus^' /. 9.)

(Emery.)

EMERY AND THE EMERY INDUSTRY. Trans-
lated from the German of A. HAENIG. Crown 8vo. 45 Illustra-
tions. 104 pp. Price 5s. net. (Post free, 5s. 3d. home ; 5s. 6d»
abroad.)

(Libraries and Bibliography.)

CLASSIFIED GUIDE TO TECHNICAL AND COM-
MERCIAL BOOKS. Compiled by EDGAR GREEN-
WOOD. Demy 8vo. 224 pp. 1904. Being a Subject-list of the
Principal British and American Books in Print ; giving Title,
Author, Size, Date, Publisher and Price. Price 5s. net. (Post
free, 5s. 4d. home ; 5s. 6d. abroad.)

HANDBOOK TO THE TECHNICAL AND ART
SCHOOLS AND COLLEGES OF THE UNITED
KINGDOM. Containing particulars of nearly 1,000
Technical, Commercial and Art Schools throughout the United
Kingdom. With full particulars of the courses of instruction ,.
names of principals, secretaries, etc. DemySvo. 150pp. Price
3s. 6d. net. (Post free, 3s. lOd. home ; 4s. abroad.)

THE LIBRARIES, MUSEUMS AND ART GAL-
LERIES YEAR BOOK, 1910-11. Being the Third
Edition of Greenwood's " British Library Year Book ". Edited
by ALEX. J. PHILIP. Demy 8vo. 286 pp. Price 5s. net. (Post
free, 5s. 4d. home ; 5s. 6d. abroad.)

THE PLUMBING, HEATING AND LIGHTING
ANNUAL FOR 1911. The Trade Reference Book
for Plumbers, Sanitary, Heating and Lighting Engineers,
Builders' Merchants, Contractors and Architects. Including
the translation of Hermann Recknagel's " Kalender fur Gesund-
heits - Techniker," Handbook for Heating, Ventilating, and
Domestic Engineers, of which Scott, Greenwood & Son have
purchased the sole right for the English Language. Quarto.
Bound in cloth and gilt lettered. Price 3s. net. (Post free,
3s. 4d. home ; 3s. 8d. abroad.)

SCOTT, GREENWOOD & SON,

tlccbnical JBoofc anD Grafce journal flMibltsbete,

8 BROADWAY, LUDGATE, LONDON, E.G.

Telegraphic Address, " Printeries, Cent., London ". February, 1913.

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

AN INITIAL FINE OF 25 CENTS

WILL BE ASSESSED FOR FAILURE TO RETURN
THIS BOOK ON THE DATE DUE. THE PENALTY
WILL INCREASE TO SO CENTS ON THE FOURTH
DAY AND TO $1.OO ON THE SEVENTH DAY
OVERDUE.

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