LIBRARY
UNIVERSITY OF CALIFORNIA.
Class
THE BREWER'S ANALYST
A SYSTEMATIC HANDBOOK OF ANALYSIS RELATING
TO BREWING AND MALTING
THE
BREWER'S ANALYST
A SYSTEMATIC HANDBOOK OF ANALYSIS
RELATING TO BREWING AND MALTING
GIVING DETAILS OF UP-TO-DATE METHODS OF ANALYSING ALL
MATERIALS USED, AND PRODUCTS MANUFACTURED,
BY BREWERS AND MALTSTERS
TOGETHER WITH
INTERPRETATION OF ANALYSES,
POLARISCOPICAL, MICROSCOPICAL, AND
BIOLOGICAL WORK
BY
R. DOUGLAS BAILEY, F.C.S., F.R.M.S.
WITH NUMEROUS ILLUSTRATIONS
OF THE.
UNIVERSITY
OF
FOKJJ^
KEGAN PAUL, TRENCH, TRUBNER & CO, LTD.
LONDON
D. VAN NOSTRAND COMPANY
NEW YORK
1907
[All rights reserved}
<-\0
^
't>'
UNIVERSITY
OF
I
PREFACE.
THE author's first work, dealing amongst other matters with the
analyses of brewing materials and products, was published sixteen
years ago, entitled Notes on Brewing, being a collection of the
more important of his articles contributed during several years to
the Brewers' Guardian. Since that time it has been his occasional
occupation to write articles on brewing for one of the trade
journals and to carry out analytical work for several large
brewing concerns. To this it may be added that for the past
eighteen years he has been daily employed in conducting practical
brewing and malting operations on an extensive scale, and can
therefore, with reason, claim to have a practical and scientific
knowledge of the subjects which his present work treats. So far
as he is aware, there are but two works dealing solely with
analyses relating to brewing one having been published so far
back as 1884, and slightly revised some six years ago, the other,
more recent, being a drawn-up course of laboratory studies for
the special use of the students at the Birmingham University.
There can be hardly any doubt under these circumstances that
there is at present a want for an up-to-date work for the use of
brewers and brewing students, and it is to supply this want that
the author has published the present volume.
Of late years there has been considerable controversy amongst
brewers' analysts as to the standardisation of analytical methods ;
and although nothing definite has so far been decided, the author
has borne the controversy in mind, and, in view thereof, has
endeavoured to steer clear of the same, and not vary the gener-
ally employed methods of analysis more than is consistent with
modern views, which have resulted in more accurate information
in the evaluation of brewing materials being obtained.
Details are given of the polarisation of light, a subject
neglected in all other works on brewing; particulars are also
given of the latest improvements in the polarimeter. A chapter is
Vi PREFACE
devoted to arsenical work, which is also of the greatest importance ;
whilst in the appendices is given a series of tables and typical
analyses which, it is believed, will prove extremely useful, par-
ticularly to those about to commence a laboratory course.
The author has left the consideration of the biological examina-
tion of water, malt, hops, and beer out of the part dealing with
methods of analysis, but has embodied the same in a separate
chapter on biological work, since an introduction to such a chapter
is necessary before a general idea of cause and effect in this
direction can be conveyed. Here will also be found particulars
of the microscope, the cultivation of single-cell yeast, the isolation
of bacteria, and other matters of general interest.
The author is indebted to Messrs Townsen & Mercer, 34
Camomile Street, London, E.G., and to Messrs Baird & Tatlock,
14 Cross Street, London, E.G., for the loan of blocks from which
numerous illustrations have been produced. The reader is
assumed to have a slight knowledge of theoretical chemistry, if
not of practical analytical methods, but the book is not intended
to replace any of the already numerous works on chemistry.
Finally, although the work is primarily intended for beginners,
it is anticipated that advanced students and qualified analysts
will find it useful as a work of reference.
K. DOUGLAS BAILEY, F.C.S., F.R.M.S.
LONDON, July 1907.
CONTENTS.
PART I.
PAGE
QUALITATIVE AND QUANTITATIVE ANALYSIS .... 1
PART II.
THE POLARIMETER 39
Polarisation of Light Specific Rotatory Power Solution
Weight Solution Factors Cupric Oxide Reducing Power
PART III.
CARBOHYDRATES AND ALLIED SUBSTANCES PROTEIDS OK AL-
BUMINOIDS AND ENZYMES 61
PART IV.
INDICATORS USED IN ALKALIMETRY 124
PART V.
PREPARATION OF STANDARD AND OTHER SOLUTIONS . . .127
PART VI.
METHODS OF ANALYSIS . . . . . . . 147
PART VII.
ARSENIC 270
PART VIII.
INTERPRETATION OF THE RESULTS OF ANALYSES 279
CONTENTS
PART IX.
MICROSCOPICAL AND BIOLOGICAL .
PAGE
326
PART X.
APPENDICES.
070
A. TYPICAL ANALYSES .....
B. TABLES AND FACTORS . . -
INDEX. ....... 407
LIST OF PLATES.
Plate
I. fig. 52. Solution Factors for Carbo-hydrates
at Various Densities
to face p. 60
II. {
I. JJ
53. Potato Starch \
54. Rye Starch J '
68
III. 1 "
I
55. Rice Starch \
56. Oat Starch J
68
IV. j
57. Maize Starch \
58. Pea Starch J '
68
H:
59. Tapioca Starch \
60. Sago Starch /
68
VI. f "
61. Barley Starch \
68
I
62. Wheat Starch /
VII. | "
63. Tous les Mois Starch \
64. Bermuda Arrowroot Starch J *
68
VIII.
80. Compound Microscope . . .
326
' ,, 85. Ped. acidi lacticf
,, 86. Sarcin a maxima
,, 87. Viscous Ferment
IX.-
,, 88. Bacterium aceti V .
,, 89. Lactic Ferment
,, 90. Bacterium lactis
,, 91. Bacterium termo
,, 92. Bacterium butyricum^
,, 93. Bacillus subtilis
,, 94. Bacterium ulna
X. -
,, 95. Bacterium leptothrix V
,, 96. Spirillum tenue
,, 97. Spirillum undula
^ , , 99. Mucor racemosus
XI / 98. Mucor mucedo 1
'I ,, 100. Mucor racemosus (submerged) /
XTT f 101. Odium lactis \
l '\ ,, 102. Penicillium glaucum J '
103 Burton Yeast \
104. London Yeast /
108. Saccharomyces Pastorianus, I
ix
.}
334
336
344
,, 346
348
358
LIST OF PLATES
Plate XV. j fi S' JJJ- Saccharomyces Pastorianus, II, )
(. ,, 110. Saccharomyces Pastorianus, III. /
XVI. -f" m< Saccharomyces ellipsoideus, I. 1
I ,, 112. Saccharomyces ellipsoideus, II. f
XVIII.
XIX.
XX.
XXI
'
( 113. Spore Formation: Saccharomyces 1
cerevisise, I. . . t *
| ,, 114. Spore Formation : Saccharomyces /
i Pastorianus, I. . J
115. Spore Formation: Saccharomyces 'l
Pastorianus, II. . . .
,, 116. Spore Formation: Saccharomyces J"
Pastorianus, III. . . . J
,, 117. Spore Formation: Saccharomyces^
ellipsoideus, I.
,, 118. Spore Formation: Saccharomyces f
ellipsoideus, II.
119. Film Formation
cerevisiae, I. .
120. Film Formation: Saccharomyces f
Pastorianus, I.
121. Film Formation
Pastorianus, II.
Pastorianus, III.
C 123. Film Formation: Saccharomyces^
XXII. -[ ellipsoideus, I. .
,, 124. lilm Formation: Saccharomyces f
t ellipsoideus, II. j
358
358
358
358
358
362
362
362
THE BREWER'S ANALYST.
PAKT I.
QUALITATIVE AND QUANTITATIVE ANALYSIS.
ANALYSIS is broadly divided into two classes, qualitative and
quantitative, the former consisting in processes for detecting one
or more or the whole of the constituents of a substance, the latter
in separating out one or more or the whole of the constituents
either in a pure state or in the form of some new substance of
known composition, and accurately estimating the quantity of
the product or products.
There are two methods by which this may be performed, the
first being known as
GRAVIMETRIC,
that is to say, separating out the constituents by gravity in the
form of a precipitate, collecting and weighing the same ; the
second method being known as
VOLUMETRIC,
consisting in submitting the substance to be estimated to certain
characteristic reactions, employing for such reaction solutions of
known strength, and from the volume of solution necessary for
the production of such reaction determining the weight of the
substance to be estimated by the aid of the known laws of
chemical equivalence. Both gravimetric and volumetric methods
are adopted in the analytical work described in subsequent pages,
and as the accuracy of both depend in the first place upon certain
principles, the employment of perfect thermometers, accurately
adjusted balances, weights, burettes, pipettes, measuring flasks,
etc., of definite capacity, and the use of certain forms of apparatus,
we may proceed at once to briefly consider the same.
1
.THE BREWERS ANALYST
means
1. The Bunsen burner (fig. 1) is generally employed in the
laboratory for heating purposes.
It is so constructed that the coal-gas, before being burnt, is
mixed with a proper proportion of air, which is drawn in through
holes at the lower part of the burner. The
flame is non-luminous, and is smaller than
the bright flame. It deposits no soot upon
a cool object. Its high temperature, non-
luminosity, and colourless appearance also
render it very valuable for producing flame
colorations. The burner is provided with
for partly or entirely closing the
air-inlets when requisite. This
is usually effected by turning
round a loose perforated ring,
which is slipped over the holes.
When the burner is to be used,
it is connected, by means of a
piece of tightly-fitting india-rubber tubing, about T \ths of an
inch in internal diameter, with the tube which supplies gas to the
working bench. The gas-tap is then turned on, and in a few
seconds the gas is lighted. The flame should be almost colourless,
and give scarcely any light.
When a small flame is used, the supply of air should be partly
FIG. 1.
FIG.
shut off, else the flame is apt to recede and burn beloiv. If this
should occur, the gas supply is stopped by pinching the rubber
tube, the supply of air is reduced, and the flame is then relighted.
The effect of partially or entirely closing the air-holes of the
burner should be learnt by experiment.
For diffusing heat over a large surface, a small perforated metal
cap, called the rose-top (a, fig. 1), is placed upon the top of the
QUALITATIVE AND QUANTITATIVE ANALYSIS 3
burner. It yields a circle of small tlames, and thus diffuses the heat.
Other forms of the burner are shown in figs. 2 and 3.
In country laboratories, where gas is not obtainable, a very
convenient form of burner is that shown in fig. 4, which is automatic
in action and constructed for burning methylated spirit contained
in the reservoir.
2. The Spirit-lamp is occasionally employed instead of the
gas or spirit burner ; but for general purposes it, or the methy-
FIG. 3.
ated spirit burner, should only be employed when coal-gas cannot
be obtained.
The spirit-lamp (fig. 5) consists of a glass vessel containing
methylated spirit, into which dips a cotton wick supported by
means of a brass or stone- ware wick-holder. When the lamp is
not in use, the upper end of the wick should be covered with the
glass cap, to prevent evaporation of the spirit.
3. Glass tube OP rod is CUt by making a deep scratch with
the edge of a three-cornered file at the point to be cut. The
glass is then held with both hands, and a gentle pressure is
exerted upon the glass as if trying to break it across. If the
file-mark has been made sufficiently deep, the glass will readily
break at this point. The sharp edges of a freshly-cut rod or
4
THE BREWER'S ANALYST
tube should always be rounded by holding them in the Bunsen
flame or blowpipe flame until they are partly melted, or by
rubbing them with the face of a file.
4. Glass tube is bent by holding it in the upper edge of
a common fish-tail gas-flame. The tube is constantly turned
slowly round on its axis, so as to heat all sides equally. As soon
as the glass is felt to be soft and pliable, it is quickly bent to
the required angle. The heated part must not be allowed to
touch anything until it is cold. It is then cleansed from soot
by means of a cloth.
A bend, if properly made, should be a curve, and should not
FIG. 6.
FIG. 4.
alter the bore of the tube. If a sharp angle is made, the bore
will be narrowed, and the bend, besides being unsightly, will be
very liable to break under a small strain.
Glass rod may be bent in the Bunsen flame or in the blow-
pipe flame.
5. The blowpipe is used for producing a small but very hot
flame. This is effected by blowing a fine stream of air through
an ordinary flame. The blowpipe (fig. 6) is held in the mouth,
and after the cheeks have been blown out to their full extent, the
air contained in them is forced out through the jet. This
produces a small-pointed, conical flame in the direction of the
blast. The chief difficulty in using the blowpipe properly is
experienced in maintaining the blast of air uninterrupted by the
respiration. The cheeks are kept inflated with air, so that the air
QUALITATIVE AND QUANTITATIVE ANALYSIS 5
may be forced through the blowpipe by the pressure of the
cheeks alone, and not by the action of the lungs. Breathing is
carried on meanwhile through the nose ; and the cheeks are
occasionally replenished with air from the lungs.
It is frequently necessary to have both hands free while the
blowpipe is being used. This "may be secured by resting the jet
on the top of the burner.
A blowpipe which is fed with air from a foot-bellows (fig. 7),
or from a mechanical or water blower, is often indispensable for
maintaining a high temperature, or for extensive glass-working
or glass-blowing.
6. Small Ignition Tubes. A piece of hard glass tubing,
FIG. 7.
five inches long, is drawn out at its middle point by heating it
strongly in the blowpipe flame. While the tube is being heated,
it is constantly turned round upon its long axis, and when
softened, it is gradually drawn out by pulling its ends in
opposite directions. By heating the conical parts successively
in the blowpipe flame, the narrow tube may be drawn off, and
two small closed tubes obtained. If the closed end of the tube
is strongly heated in the blowpipe flame, and is then gently
blown into while it is red-hot, it may be expanded into a small
bulb.
Small test-tubes, three inches long by half an inch in diameter,
will also serve for ignition tubes (fig. 8).
7. Mounted Platinum Wires. Two pieces of platinum wire,
each about two inches in length, should be fixed in glass handles
in the following way : Draw out a piece of glass tube, five inches
6
THE BREWER'S ANALYST
in length, at its middle point, and cut it across at the middle
of the narrow portion. Each piece of glass thus obtained serves
for the handle of a wire. Break off the narrow part of the tube
until it extends only about a quarter of an inch from the shoulder.
Insert the end of the platinum wire into this narrow opening ;
and hold the end of the tube in the blowpipe flame until the
glass melts and thickens around the wire, fixing it firmly
when cold. Then roll the free end of the wire round a stout
wire, so as to shape it into a loop about the eighth of an inch
across.
8. Glass Stirringf-RodS- Cut some glass rods into lengths
of three, six, and seven inches. Heat both ends of each of these
rods to redness in the blowpipe
flame, the rod being meanwhile
constantly turned round on its
long axis. The sharp edges are
thus removed. The end of the
rod must not be allowed to touch
anything until it is cool. If a
very thin glass rod is required,
FIG. 9.
FIG. 10.
heat part of an ordinary rod in the blowpipe flame until it is soft,
then draw it out to the requisite degree of fineness.
9. Corks are bored by means of the cork-borer, which is a
brass or steel tube sharpened at one end. These are of various
sizes, one fitting into another (fig. 9). A borer is selected
of slightly less diameter than the glass tube which is to be
inserted into the cork. The cork is then pressed against a
wooden surface, and the perforation is made by gently pushing
the borer through it with a constant movement of rotation upon
its axis.
QUALITATIVE AND QUANTITATIVE ANALYSIS 7
A convenient mechanical contrivance for boring holes through
corks and rubber stoppers is shown (fig. 10), several borers of
different sizes being supplied which may be conveniently screwed
to the apparatus as required.
A slender round file is used for smoothing the interior of
the hole made by the cork-bd'rer, and for slightly enlarging it.
Great care must be taken to leave the hole round in shape,
and not to enlarge it so much that the glass tubing, when
inserted, fits loosely. The cork-borer is sharpened by rubbing
the outer part of the edge obliquely with the face of a fine-
toothed file.
10. The Wash-bottle. A thin, flat-bottomed conical flask,
about eighteen ounces in capacity, and with a neck about an inch
in diameter, is fitted as is shown in fig. 11.
Select a sound cork which is slightly too large to enter the
neck of the flask. Roll it backwards and for-
wards under the foot with gentle pressure. When
the cork has been thus softened, it must fit tightly
into the neck of the flask.
Two pieces of glass tubing, rather longer than
would be required for the tubes, are then bent
(4) into the form shown in fig. 11. Their ends
are cut off to the right length, and the sharp
edges are rounded (3).
Two parallel holes are then made in the cork
by means of a cork-borer (9). The holes must
be somewhat smaller than the glass tubes, and may 'j,
be smoothed, and slightly enlarged, if necessary, by
the round file. Into these holes the tubes are then gently
pushed ; they must enter somewhat stiffly.
An india-rubber Stopper is much more durable than a cork
for this and for most other chemical purposes. It may be purchased
with two holes already made, or may be perforated by a sharp,
wetted cork-borer (9). Both the glass tubes and the inside of the
holes should be well wetted before the tubes are inserted, since water
serves as a lubricant for glass against rubber. Before the fitting
of the flask is proceeded with, insert the cork with the tubes into
the neck. Close one tube with the finger, and blow down the
other tube. A leakage of air is, as a rule, easily detected ; but by
wetting the outside of the cork, the escape of air-bubbles becomes
visible.
If the cork is air-tight, fit upon the long tube a piece of india-
rubber tubing about an inch in length. Into the other end
8
THE BREWER'S ANALYST
of this rubber tube push a short jet, made by drawing out a
piece of glass tubing in the blowpipe flame. The neck of the
flask may then be bound round with twine like the handle of a
cricket bat, or tightly covered with a folded strip of rubber or
other material. This renders it possible to handle the wash-bottle
when it is hot.
The wash-bottle is now nearly filled with distilled water, and
is ready for use.
Tap-water should not be kept in the wash-bottle. A fine stream
of water may be obtained from the jet by blowing down the
short tube. This stream serves for washing percipitates and for
other purposes. If a larger stream is required, the flask is in-
verted, when the water will flow out from the end of
the short tube, air entering meanwhile by the long
tube.
When hot water is required, the wash-bottle is
supported on a tripod stand upon a piece of coarse
iron-wire gauze, and is heated by the Bunsen flame,
or it may be placed on the water-bath (figs. 29, 30,
fl and 31).
It is preferable to have two wash-bottles, one as de-
scribed for hot water, the other of stronger build for
cold.
11. Cleaning 1 Apparatus. It is indispensable to
the success of an analyst that all glass and porcelain
apparatus should be scrupulously clean, and before
beginning to work, the student will do well to clean his
set of apparatus as directed below.
Test-tube Brush. This brush is constantly used for
/iff cleaning glass and porcelain apparatus. The piece of
FIG 12 s P n S e ordinarily fastened on the end of the brush does
not well adapt itself to the bottom of test-tubes and
boiling-tubes. A much more efficient end is given to the brush
by removing the sponge and bending back the end of the wire
stem sharply upon itself at a point just above where the hairs
commence (fig. 12).
Test-tubes^ beakers, and porcelain dishes are washed in a stream
of tap-water, their surface being rubbed meanwhile by the test-
tube cleaner. If the brush fails to remove a stain, hot dilute
hydrochloric acid may be used. Sometimes it is necessary to
heat a little strong sulphuric or nitric acid in a vessel in order
to cleanse it. Hot caustic potash solution may be used to remove
grease. In fact, when removing a substance from a vessel to
QUALITATIVE AND QUANTITATIVE ANALYSIS 9
which it strongly adheres, it should be treated by a liquid in
which it is easily soluble. Each article, after it has been carefully
washed with tap-water, should be placed upside down in a wicker
basket to drain.
Apparatus should be washed as soon as possible after use,
since the surface is more difficult to clean after standing.
Test-tubes containing liquids are placed in a test-tube stand.
After being washed, they should be placed to drain mouth down-
wards in the wicker basket.
Platinum foil and wire ar? cleansed by boiling them in hydro-
chloric acid and rinsing off the acid with water. The wire should
then be strongly heated for some time in the blowpipe flame,
until, when wetted with pure, strong hydrochloric acid and held
in the Bunsen flame, it no longer persistently colours the
flame. If the tip of the wire cannot be cleansed in this
way, it should be cut off. Commercial platinum is sometimes
FIG. 13. FIG. 14.
alloyed with barium or some other metal which colours the flame.
Wire made from such platinum is useless for flame-coloration
tests.
Instead of cleaning platinum foil and wire immediately before
use, it is better to keep them in a small beaker containing
moderately strong hydrochloric acid. The platinum, when
removed from the acid and rinsed with water, will then usually
be sufficiently clean for use.
Before putting apparatus away, it should be made a rule
to wash all glass or porcelain which is not in actual use,
and place it in the wicker basket to drain. The basket is
then put away with its contents. Dirty apparatus should never
be kept in the basket. AH iron apparatus should be carefully
dried, and must be kept in a dry place to prevent it from
rusting. Metal apparatus must never be put into the wicker
draining-basket.
12. Heating 1 Porcelain and Glass. The two follow-
ing rules must be attended to when either a glass or a
10
THE BREWERS ANALYST
porcelain vessel is being heated, in order to avoid the risk of
cracking it.
A vessel containing a liquid must never be heated by the flame
above the level of the liquid inside. A dry, hot vessel must be
allowed to cool before it is placed on a cool surface, and before
any liquid is poured into it.
Porcelain dishes (fig. 13) are generally used for the purpose of
boiling or evaporating liquids. They are supported on a pipe-
clay triangle or wire-gauze placed upon a tripod or retort-stand.
They may be safely heated by a small naked flame.
Porcelain crucibles (fig. 14) are used for containing solid
bodies which are to be strongly heated. They are supported in
the same way as porcelain dishes. The flame should not at first
be allowed to play steadily upon the bottom of the crucible so as
to heat it suddenly ; but the burner should be constantly moved
slightly from side to side until the porcelain is hot. The
crucible should be allowed to cool slowly on the triangle before
being removed. The hot crucible and cover are handled by
means of the crucible tongs (fig. 15).
Glass vessels require to be heated more cautiously than those
made of porcelain. A large naked flame must never be allowed
to play for any length of time on one part of
the glass surface. In heating a test-tube or
boiling-tube, this local heating is prevented by
holding the tube obliquely with the lower part
in the flame, and either moving it gently up and
down, or constantly turning it round on its axis.
Small quantities of liquid may be boiled in a test-
tube ; but for boiling larger quantities broader
boiling-tubes are better suited. The risk of burn-
ing the fingers by steam is avoided by bending
round the neck of the tube a strip of folded
paper, and pinching the ends of the strip together,
close to the tube.
Glass flasks are most safely heated by placing
them upon a piece of coarse wire-gauze on a
tripod stand. In many laboratories a sand-bath
is employed ; the flask may then be heated on the sand ; it is
better still, however, to heat the flask by placing it on the
water-bath.
13. Thermometers are instruments for measuring tempera-
tures. Owing to the imperfections of our senses, we are unable
to measure temperature by the sensation of heat or cold which
FIG. 15.
QUALITATIVE AND QUANTITATIVE ANALYSIS 11
they produce in us, and for this reason recourse must be had to
the physical actions of heat on bodies. These actions are of
various kinds, but the expansion of bodies has been selected as
being the easiest to observe.
Liquids are best suited for the construction of thermometers
the expansion of solids being too small, and that of gases too
great. Mercury and alcohol are the only liquids now commonly
used.
The mercury thermometer is the most extensively used. It
consists of a capillary glass tube, at the end of which is blown a
bulb a cylindrical or spherical reservoir. Both the bulb and
a part of the stem are filled with mercury, and the expansion is
measured by a scale graduated either on the stem itself, or on a
frame to which it is or may be attached.
The construction of the thermometer comprises three opera-
tions : the calibration of the tube, or its divisions into parts of
equal capacity ; the introduction of the mercury into the reservoir ;
and the graduation.
Division of the Tube into Parts of Equal Capacity. As the
indications of the thermometer are only correct when the
divisions of the scale correspond to equal expansions of the
mercury in the reservoir, the scale must be graduated, so as to
indicate parts of equal capacity in the tube. If the tube were
quite cylindrical, and the same diameter throughout, it would
only be necessary to divide it into equal lengths. But as the
diameter of glass tubes is usually greater at one end than
another, parts of equal capacity in the tube are represented by
unequal lengths of the scale. In order, therefore, to select a
tube of uniform calibre, a thread of mercury about an inch long
is introduced into the capillary tube, and moved in different
positions in the tube, care being taken to keep it at the same
temperature. If the thread is of the same length in every part
of the tube, it shows that the capacity is everywhere the same ;
but if the thread occupies different lengths, the tube is rejected,
and another one sought.
Filling the Thermometer. In order to fill the thermometer with
mercury, a small funnel is blown on at the top of the tube, and
is filled with mercury ; the tube is then slightly inclined, and the
air in the bulb is expanded by heating the bulb with a spirit-
lamp. The expanded air partially escapes by the funnel, and on
cooling, the air which remains contracts, and a portion of the
mercury passes into the bulb. The bulb is then again warmed,
and allowed to cool, a fresh quantity of mercury enters, and so on
12 THE BREWER'S ANALYST
until the bulb and part of the tube are full of mercury. The
mercury is then heated to boiling the mercurial vapours in
escaping carrying with them the air and moisture. The tube
being full of the expanded mercury and of mercurial vapour, is
then hermetically sealed at the open end, and when the thermo-
meter is again cooled, the mercury should fill the bulb and a
portion of the stem.
Graduation of the Thermometer. The thermometer being filled,
it requires to be graduated, that is, to be provided with a scale to
which variations of temperature can be referred. And, first of
all, two points must be fixed which represent identical tempera-
tures and which can always be easily reproduced.
Experiment has shown that ice always melts at the same
temperature whatever be the degree of heat, and that distilled
water under the same pressure, and in a vessel of the same kind,
always boils at the same temperature. Consequently, for the
fixed point, or zero, the temperature of melting ice has been
taken ; and for a second fixed point, the temperature of boiling
water in a metal vessel under the normal atmospheric pressure.
This interval of temperature, that is, the range from zero to the
boiling-point, is taken as the unit for comparing temperatures ;
just as a certain length, a foot for instance, is used as a basis for
comparing lengths.
Determination of the fixed Points. To obtain zero, snow or
pounded ice is placed in a vessel in the bottom of which there is
an aperture by which water may escape. The bulb or part of
the stem of the thermometer is immersed in this for about 15
minutes, and a mark is then made on the tube at the level of the
mercury and represents zero.
The second fixed point is determined by suspending the thermo-
meter in an apparatus designed so that water may be boiled and
the steam escape under ordinary atmospheric pressure. The
thermometer is thus surrounded with vapour, the mercury
expands, and when it has become stationary the point at which it
stops it marked. This is the point sought for.
The determination of the boiling-point of a centigrade thermo-
meter, viz. 100, would seem to require that the height of the
barometer during the experiment should be 29 '92 inches or 760
millimetres, for when the barometric height is greater or less
than this quantity, water boils either above or below 100 C.
But the point 100 C. may always be exactly obtained by making
a suitable correction. For every 27 millimetres' difference in
height of the barometer, there is a difference in the boiling-point
QUALITATIVE AND QUANTITATIVE ANALYSIS 13
of 1 degree. If, for example, the height of the barometer is 778
that is, 18 millimetres or two-thirds of 27, above 760 water
would boil at lOOf. Consequently, lOOf would have to be
marked, on a centigrade thermometer, at the point at which the
mercury stops.
Gay-Lussac observed that ..water boils at a somewhat higher
temperature in a glass than in a metal vessel ; and as the
boiling-point is raised by any salts which are dissolved, it was
assumed to be necessary to use a metal vessel and distilled water
in fixing the boiling-point. Rudberg showed, however, that these
latter precautions are superfluous. The nature of the vessels and
salts dissolved in ordinary water influence the temperature of
boiling water but not that of the vapour which is formed. That
is to say, if the temperature of boiling water from any of the
above causes is higher than 100 C., the temperature of the
vapour does not exceed 100 C., provided the pressure is not
more than 760 millimetres. Consequently, the higher point
may be determined in a vessel of any material, provided the
thermometer is quite surrounded by vapour, and does not dip
in the water.
Even with distilled water, the bulb of the thermometer must
not dip in the liquid ; for it is only the upper layer that really
has the temperature of 100 C., since the temperature increases
from layer to layer towards the bottom in consequence of
increased pressure.
Construction of the Scale. Just as the foot-rule which is
adopted as the unit of comparison for length is divided into a
number of equal divisions called inches, for the purpose of having
a smaller unit of comparison, so likewise the unit of comparison
of temperatures, the range from zero to the boiling-point, must
be divided into a number of parts of equal capacity called degrees.
On the Continent, and more especially in France, this space is
divided into 100 parts, and this division is called the Centigrade
or Celsius scale, the latter being the name of the inventor.
The degrees are designated by a small cipher placed a little
above, on the right of the number which marks the temperature,
and to indicate temperatures below zero the minus sign is placed
before them. Thus - 15 signifies 15 degrees below zero.
In accurate thermometers the scale is marked on the stem
itself. It cannot be displaced, and its length remains fixed, as
glass has very little expansibility. The graduation is effected by
covering the stem with a thin layer of wax, and then marking the
divisions of the scale, as well as the corresponding numbers, with
14 THE BREWER'S ANALYST
a steel point. The thermometer is then exposed for about ten
minutes to the vapours of hydrofluoric acid, which attacks the
glass where the wax has been removed. The rest of the wax
is then removed, and the stem is found to be permanently
etched.
Besides the Centigrade scale, two others are frequently used
Fahrenheit's scale and Reaumur's scale.
In Reaumur's scale the fixed points are the same as on the
Centigrade scale, but the distance between them is divided into
80 degrees instead of into 100. That is to say, 80 degrees
Reaumur are equal to 100 degrees Centigrade; 1 degree
Reaumur is equal to ^^ or f of a degree Centigrade ; and 1
degree Centigrade equals T 8 ^ F or i degrees Reaumur. Con-
sequently, to convert any number of Reaumur's degrees into
Centigrade degrees (20 for example), it is merely necessary to
multiply them by f (which gives 25). Similarly, Centigrade
degrees are converted into Reaumur by multiplying them by -|.
The thermometric scale invented by Fahrenheit in 1714 is still
largely used in England and elsewhere. The higher fixed point is
like that of the other scales, the temperature of boiling water,
but the null point or zero is the temperature obtained by mixing
equal weights of sal-ammoniac and snow, and the interval between
the two points (the lowest then known) was thought to represent
absolute cold.
When Fahrenheit's thermometer is placed in melting ice it
stands at 32 degrees, and therefore 100 degrees on the Centi-
grade scale are equal to 180 degrees on the Fahrenheit scale, and
thus 1 degree Centigrade is equal to f of a degree Fahrenheit,
and inversely 1 degree Fahrenheit is equal to f of a degree
Centigrade.
If it be required to convert a certain number of Fahrenheit
degrees (95 for example) into Centigrade degrees, the number 32
must first be subtracted in order that the degrees may count
from the same part of the scale. The remainder in the example
is thus 63, and as 1 degree Fahrenheit is equal to -| of a degree
Centigrade, 63 degrees are equal to 63 x f or 35 degrees Centi-
grade.
If F be the given temperature in Fahrenheit degrees and C the
corresponding temperature in Centigrade degrees, the former may
be converted into the latter by means of the formula
(F-32)|=C,
QUALITATIVE AND QUANTITATIVE ANALYSIS 15
and conversely, Centigrade degrees may be converted into Fahren-
heit by means of the formula
-
5
These formulae are applicable to all temperatures of the two
scales, provided the signs are taken into account. Thus, to
convert the temperature of 5 degrees Fahrenheit into Centigrade
degrees, we have
In like manner we have, for converting Reaumur into Fahrenheit
degrees, the formula
and conversely, for changing Fahrenheit into Reaumur degrees
the formula
" I =R
More briefly stated we have :
F. to C., subtract 32, multiply by 5, and divide by 9.
F. R., 32 4 9.
R. F., multiply by 9, divide by 4, and add 32.
R. C., ;, 5 4.
C. R., 4 5.
C. F., 9 5, and add 32.
14. Balances. In a brewer's laboratory, a pair of scales as
shown (fig. 16), and weights ranging from J oz. to 2 Ibs. (fig. 17)
will be found extremely useful, especially in weighing barley,
malt, hops, sugar, etc., where extreme accuracy is not needed.
It is absolutely essential, however, that the laboratory be equipped
with a really good light and delicate balance (fig. 18) to carry
100 grams and turn easily and quickly when loaded, with a
weight of one- or two-tenths of a milligram (figs. 19, 20). The
balance consists of a perfectly rigid metal beam suspended near
its centre of gravity on a fulcrum, the substance under comparison
being suspended from pivots placed at either extremity of the
beam, equidistant from and in the same horizontal line with the
fulcrum in the centre. The beam usually rests, by means of a
triangular piece of steel termed a knife-edge, on a plate of polished
16
THE BREWER'S ANALYST
agate. At the beam-arms similar arrangements exist,, the knife-
edge in each case being reversed and supporting an agate plate,
from which depends a hook, with wires attached to and supporting
each pan. A small metal vane is fixed on the exact centre of the
FIG. 16.
beam above the central knife-edge, which, by being turned to the
right or left, compensates any inequality in the weight of the arms
or pans ; or, instead of a vane, a screw weight may be employed at
one end of the beam, the precise distance of which, from the
centre, may be adjusted as required. The movements of the
beam are indicated by a vertical pointer
which oscillates before a small ivory
scale fixed to the base of the pillar.
A balance of this description serves for
weighing small quantities of substances
to be tested, many of which are hygro-
scopic and need to be weighed quickly
and with great accuracy. It also serves
for testing the accuracy of pipettes and
burettes, and, in fact, for the prepara-
tion of standard and other solutions and
all gravimetric analyses, as mentioned in subsequent pages.
15. Weights and Weighing". The weights most convenient
for use in chemical experiments are those based on the decimal
or metric system. A box of weights (fig. 19) ranging from 100
grams to a milligram is most useful and sufficient for all chemical
purposes. Since these weights are either multiples or sub-
multiples of ten, the weight of a substance is most conveniently
written down in the decimal notation. Thus a weight of 10
grams, 6 decigrams, 4 centigrams, and 3 milligrams, would be
written 10*643 grams.
FIG. 17.
QUALITATIVE AND QUANTITATIVE ANALYSIS
17
The larger weights are usually made of brass, the smaller
ones of platinum or aluminium (fig. 20). Instead of employing
the very small milligram weight, a wide " rider " (a piece of
platinum wire in the shape & ), weighing 1 centigram, is gener-
ally used. This is suspended over the graduated scale along the
beam of the balance,, the scale" being graduated in ten divisions,
each of which corresponds to 1 milligram. The " rider " placed
on the extreme end or tenth division of the scale, immediately
over the axis of the pan, equals 1 centigram, or, what is the
FIG. 18.
same thing, 10 milligrams; placed on the fifth division, it equals
but half this amount, and so on. Sometimes the arm of the
balance is divided into twelve divisions, in which case the rider
weighs 12 milligrams. Each division, of course, then corre-
sponds to 1 milligram.
The following rules should be observed during the process of
weighing :
(a) Place the substance on the left-hand pan of the balance
and the weights on the right.
(b) No substance must be placed directly on the scale- pan.
(c) Most substances can be weighed on a watch-glass or in a
2
18
THE BREWER S ANALYST
small dish, which has been previously weighed, or balanced by
means of a counterpoise.
(d) A non-volatile liquid is weighed in a balanced beaker or
dish ; a volatile liquid is weighed in a stoppered bottle.
FIG. 19.
(e) The weights should not be handled by the fingers, but
should be lifted by a brass forceps.
(/) The weights should be placed on the pan in a systematic
manner. Commence with the heavier weights, and if they are
too heavy, take the lighter weights in succession until the correct
ones are found. This method attains the result more quickly
and certainly than a random selection of weights would do.
FIG. 20.
(g) Before placing a substance or weight on the balance,
always bring the beam to rest by means of the lever.
(h) A substance should be weighed while it is at the same
temperature as that of the room ; if it is much colder or hotter
than the surrounding air, the body will appear heavier or lighter
than it should do.
QUALITATIVE AND QUANTITATIVE ANALYSIS 19
(i) The substance may be considered to be balanced by the
weights when the pointer swings through equal distances on
both sides of the central mark on the graduated ivory scale
fixed at the base of the pillar of the balance.
Occasionally the balance requires a careful removal of its
various parts for cleaning. The greatest care should be exer-
cised in this matter ; the various parts should be placed on a
clean sheet of paper, carefully wiped with a chamois leather,
and returned to their positions. Weights may be cleansed in
the same manner, and on no account should they be scraped or
cleansed otherwise than in the manner directed, excepting the
smaller weights, which, if of platinum, may be passed through a
smokeless Bunsen flame which will remove any organic matter
which may have become attached after prolonged use. The
smaller weights, however, are sometimes
made of aluminium, in which case they
must not be heated.
The balance case should never be left
open when out of use, should be closed
while ascertaining the final weight of any
substance by means of the rider, and
neither weights nor any substance should
be allowed to remain on the pans for any
length of time.
16. The desiccator usually employed FlG 21
in a laboratory consists of a glass dish of
the form shown in fig. 21. In the bottom of the vessel sulphuric
acid is placed, and over this is fitted a perforated tray of metal.
The rim of the vessel is smeared with grease or vaseline, so that
when it is covered by the lid the atmosphere is excluded. Upon
placing a substance to be cooled, such as a crucible containing
a calcined precipitate, on the perforated tray, and then fixing the
lid so as to render the vessel air-tight, the crucible and its
contents are, in time, cooled to the ordinary temperature, the
sulphuric acid at the bottom of the desiccator absorbing the
moisture. Substances should not be weighed until quite cold.
Should they have been previously heated, they would, in the
ordinary way, have to be exposed for a long period to the atmos-
phere in order to become cold ; and since all bodies, on cooling,
attract moisture to their surfaces in varying degree, their weight
by reason of this becomes augmented. This applies with greater
force to bodies which cool but slowly and to them that readily
absorb moisture, so that the use of a desiccator becomes obvious.
20
THE BREWER'S ANALYST
Fused chloride of calcium is sometimes employed as a desiccating
agent in place of sulphuric acid. For the interior of the balance,
calcium chloride is preferable, since, should sulphuric acid be here
employed and be accidentally spilt, it would ruin the balance,
whereas the spilling of calcium chloride might do but little damage.
Calcium chloride is not, however, so good a desiccating agent as
sulphuric acid, and should not
be employed, on this account,
in the ordinary desiccator.
17. Burettes. These in-
struments are used for the de-
livery of accurately measured
quantities of any particular
standard or other solution.
They invariably consist of a
long glass tube of even bore,
throughout the length of
which are engraved certain
divisions corresponding to a
known volume of fluid.
They may be obtained in a
great many forms under the
names of their respective in-
ventors, such as Mohr, Gay-
Lussac, Binks, etc. The Mohr
burette, with india-rubber tube
and metal spring clip (fig.
22, a), is preferred to any
other, being simple, the
quantity of fluid to be de-
livered being regulated to a
nicety by the pressure of the thumb and finger on the clip, and
the instrument not being held in the hand, there is no chance of
increasing the bulk of the fluid by the heat of the body, and thus
leading to incorrect measurement. There is, however, a great
drawback to this instrument, viz., it cannot be used for per-
manganate in consequence of its india-rubber tube, which decom-
poses the solution ; nor can it be used for iodine or strong alkaline
solutions. In such instances it is therefore preferable to employ
a burette of the same kind, only fitted with a glass stop-cock,
as is shown (fig. 22, 6).
These instruments are usually of a capacity to hold 100 c.c. or
50 c.c., and graduated in tenths of a c.c.
FIG. 22.
QUALITATIVE AND QUANTITATIVE ANALYSIS
21
31
The burette is filled with liquid from the top, the lower end
being closed. A little of the liquid is allowed to flow out through
the rubber tube or tap, in order to sweep out air-bubbles. The
liquid is then allowed to gradually flow out until the curved
under surface, called the meniscus, just reaches the zero graduation
near the top of the burette. The appearance of the meniscus is
shown in fig. 23. The volume of liquid shown in this figure
would be read as 32 c.c.
When the burette is being used, the volume of liquid is read,
and the stop-cock is then opened. When the requisite quantity
of liquid has flowed out, the reading is again taken. The differ-
ence between the two readings will
give the volume of the liquid which
has flowed from the burette. A
light glass float known as Erdmann's
float (fig. 24) is sometimes used to j 30 1 1-^:30
facilitate the reading of the liquid
volume.
The float consists of an elongated
closed glass bulb containing a small
quantity of mercury, and having a
diameter slightly less than that of
the burette ; round this bulb is
etched a regular line. The position
of this line is read off on the burette. ^^ k^xjj a b
In titrating hot or boiling solu- FlG 2 3. FIG. 24. FIG. 25.
tions, the burette should not be
arranged directly over the utensil containing the hot liquid, since
the burette would be heated and an incorrect reading obtained.
It is advisable in such instances to attach to the end of the
burette, by means of rubber tubing, a piece of bent glass tubing,
so that the heat evolved does not come directly in contact with
the burette.
18. Pipettes. A pipette is used for delivering a small
volume of a liquid. It usually consists of a tube narrowed at
both ends. Two kinds of pipette are in general use : one (fig. 25, b)
serves to deliver a definite volume of liquid, in this instance 20
c.c. ; the other (fig. 25, a) is graduated throughout, and serves to
deliver fractions of 10 c.c.
In using the pipette, the liquid is drawn into it, by suction,
past the graduation mark, and is retained by placing the first
finger over the upper end. The pressure of the finger is then
slightly relaxed, and the liquid is allowed to flow out until the
22
THE BREWER'S ANALYST
lower curve of its surface (meniscus) just reaches the graduation.
The finger is then firmly pressed down again so as to arrest the
flow. When the liquid is to be "delivered" from the pipette, the
finger is removed or its pressure relaxed until the liquid has
flowed out. When the pipette is emptied, it is allowed to drain
further for a few seconds in a vertical position, so as to deliver the
liquid which adheres to its inside. In both the whole and
graduated pipettes the upper end is narrowed to about one-eighth
inch, so that the pressure of the finger is sufficient to arrest the
flow at any point.
The usual capacities are 5 c.c. or 10 c.c. graduated stem ; 5 c.c.,
c.c
GO
50 -
FIG. 26.
10 c.c., 15 c.c., 20 c.c., 25 c.c., 50 c.c., 70 c.c. and 100 c.c. to
deliver.
19. Measuring-Flasks. These indispensable instruments are
made of various capacities ; they serve to mix up standard solu-
tions to a given volume, and also for the subdivision of the liquid
to be tested, and are in many ways most convenient. They
should be tolerably wide at the mouth, and have a well-ground
glass stopper, and the graduation line should fall just below the
middle of the neck, so as to allow room for shaking up the liquid.
Convenient sizes are 50 c.c. (to deliver), 100 c.c., 200 c.c.,
250 c.c., 300 c.c., 500 c.c. and 1000 c.c. (1 litre), all graduated to
contain the respective quantities.
Graduated cylinders are shown (fig. 26) and glasses (fig. 27).
QUALITATIVE AND QUANTITATIVE ANALYSIS
The latter are graduated, as shown, to contain from 1 pint to
1 gill and also to show fluid ounces.
Cylinders are usually graduated throughout the greater part of
their length, the graduations indicating cubic centimetres, or
multiples of cubic centimetres, according to the capacity. They
may be obtained either closed Ijy a stopper, or open.
When the measurement of a volume of liquid is being taken,
FIG. 27.
the under surface of the liquid (meniscus) should be exactly level
with the graduation.
20. Filtration is generally performed by employing a glass
funnel (fig. 28) into which a folded filter paper is placed, adding
the solution to be filtered in such quantity as will
not fill the funnel more than three-quarters full at
any time.
Glass funnels of a diameter of three inches, the
sides of which should be perfectly regular and
inclined at an angle of 60 degrees, the stems
narrow and long and cut off at the end obliquely,
are the most convenient to employ.
The liquid to be filtered should be added to the
funnel containing the filtered paper, by allowing it
to gently run down a glass rod which should be held over the
funnel with one hand, the other hand decanting the liquid.
If the liquid were poured into the apex of the paper, loss by
spirting might result, and there is the danger also of the paper
itself becoming ruptured.
FIG. 28.
24 THE BREWER'S ANALYST
In most cases a portion of the precipitable matter in suspension,
or the precipitate itself, when passed on to the filter paper, is apt to
pass through the pores of the paper ; it is therefore advisable to
first see that the pores of the paper are filled before proceeding
to use the filtrate. A portion of the liquid to be filtered should
therefore be allowed to pass through the paper and then be
returned and refiltered. This is in numerous instances essential,
whilst in some cases it is necessary to first moisten the filter
paper with hot or cold water or weak ammonia before commencing
to filter.
The stem of the funnel should be arranged to touch the side
of the receptacle receiving the filtrate, so that splashing may be
avoided, and the speed of flow accelerated by capillary attraction.
Having transferred the whole of the precipitate to the filter
paper, the next operation is to wash it ; this is performed by the
aid of the wash-bottle (fig. 11). By holding the wash-bottle and
blowing through the short tube, the spray of water issuing from
the long tube may be directed against the upper edge of the
filter paper. Care should be taken, however, to moderate the
force of the flow so as to avoid rupturing the paper.
The funnel should not be refilled until the liquid previously
added has passed through. A precipitate usually requires three
thorough washings after the whole of the liquid has been passed
through the paper. This is a point of great importance, as
inattention to it is the cause of many worthless results.
Precipitates of a very gelatinous nature take a long time to
filter, and the process therefore becomes tedious. In order to
accelerate filtration in such instances, one of the simplest and
most efficacious ways is to take a rubber stopper through which
two holes are bored, fit it to a flask or bottle in the same manner
as in constructing a wash-bottle, pass the stem of the glass
funnel, through which it is intended to filter, through the hole
which would, in the case of the wash-bottle, be fitted with a piece
of glass tubing to almost the bottom of the flask, and through the
other hole pass the ordinary piece of bent tube. To the end of
this bent tube fit a small piece of india-rubber tubing and a metal
spring clip. Having inserted the folded filter paper in the funnel
and added the liquid it is intended to filter, place the mouth to
the end of the rubber tubing and apply suction, by which means
the air is withdrawn from the flask and a partial vacuum created ;
this facilitates the filtration, which, under such circumstances, is
wonderfully expedited. In fact, the most gelatinous precipitates
can be speedily and effectively filtered in this way. Care should
QUALITATIVE AND QUANTITATIVE ANALYSIS . 25
be exercised to only gently create the partial vacuum, as, otherwise,
there is great danger of rupturing the apex of the filter paper.
21. Evaporation. Liquids are easily evaporated by long-
continued heating or by boiling them in a porcelain or platinum
dish over a Bunsen flame. In these cases, however, there is the
liability of spirting, and with such liquids as beer, wort, sugar
solutions, etc., there is the disadvantage that their constituents
may, by this method of evaporation, caramelise. 1
It is best to avoid evaporation by direct flame, and in no
instance should alcohol, methylated spirit, ether, or liquids con-
taining the same, be subjected to such method of evaporation, as
they would undoubtedly catch fire.
Under these circumstances it is wisest in all cases to evaporate
liquids over the water-bath.
22. The water-bath (figs. 29, 30, 31) consists of a vessel
made of sheet copper fitting
into another vessel of the same
material, leaving a space
between the two around the
sides and bottom of about
1 inch, and at the top about
1J inch, so that water may
be added to nearly fill the
space. There are usually one
or two doors in front of the
vessel, the interior constitut-
ing a drying oven, so that
samples of malt, etc., may be
introduced and dried. On the
top of the vessel there are FIG. 29.
openings fitted with lids
(fig. 29), or a series of flat rings of varying diameter which fit one
on top of the other (fig. 30), so that the openings may be made
large or small to allow of the exact fitting of the utensil containing
the liquid to be evaporated. On the other hand, each opening is
fitted with an Iris diaphragm as shown (fig. 31).
A liquid to be evaporated is poured into a porcelain or platinum
dish and the dish placed on the water-bath. A Bunsen flame is
1 In evaporating liquids it should be remembered that both glass and
porcelain are attacked by many solutions, and thus error (sometimes serious)
may be introduced into analyses. The estimation of alkalies may be affected
by this cause. It is preferable, therefore, to employ a platinum dish for all
such purposes.
26 THE BREWER'S ANALYST
placed beneath the bath, and as the water boils the steam heats
the vessel containing the liquid being experimented with, and
evaporation is allowed to continue until the liquid is of the bulk
desired, or until it is completely evaporated.
In the analysis of malt, when the mash is made and placed on
the bath, it is necessary to maintain a constant temperature of
150 F. (65 '5 C.) for about an hour. In order to do this the
Bunsen burner employed for heating the water in the bath is
fitted with a gas regulator, so that the water may be maintained
at the proper temperature. The gas regulator is known as the
"thermostat."
FIG. 30.
23. Thermostat. The principle of this instrument consists
in the mercury, when heated, expanding, and closing the main
entrance of the gas.
Referring to fig. 32, a shows a T-tube ground to fit into the
wide part of a thermometer tube ; b shows a side gas exit tube,
and c shows a mercury bulb at the foot of the thermometer tube ;
s represents the side tube filled with mercury and fitted with a
metal screw ; A is a small hole in T-tube a opposite b. The gas
enters by a and passes through b to the burner. When the
temperature rises the mercury expands into the wide part of the
cylinder, closing the bottom a tube ; the burner is thereby
reduced, as it is only fed by the small hole in T-tube. S screw
regulates the heat. If a high temperature is wanted, then the
QUALITATIVE AND QUANTITATIVE ANALYSIS
27
mercury must be pressed down the tube to begin with, as it is only
when the required temperature is reached that the mercury should
rise as high as the widening in the tube, and shut off the excess
of gas above that which is required.
Owing to impurities in the gas, the mercury in time becomes
coated with a film, which affects the sensibility of the apparatus.
FIG. 31.
In order to remove this film, take out T-tube a, screw down
the mercury, and clean with a brush.
This regulator, known by the name of its inventor Reichert
is suitable for all temperatures. For very low temperatures
however, instead of a Bunsen burner, it is better
to use a burner with a very small opening, almost
the size of a blowpipe jet.
24. The Air-Bath. For driving off the water
of crystallisation from salts such as the residue
from water and with substances which do not
undergo change at very high temperatures, it is
usual to dry them off in an air-bath. This con-
sists of a box of sheet copper having a closely
fitting door. It is placed on an iron tripod and
heated by a Bunsen flame, the temperature
employed and regulated by a thermostat being
215-6 F. (102 C.).
25. Precipitates and Ignition. In some
cases it is necessary to weigh a precipitate col-
lected on a filter paper ; but before weighing, it j,
becomes essential to thoroughly dry it. In such
instances the glass funnel containing the filter paper and its
contents is placed in the water oven (22) and thoroughly dried,
28 THE BREWER'S ANALYST
after which the paper is removed from the funnel, folded, placed
under the desiccator (16) to cool, and afterwards weighed, deduct-
ing the weight of the unburned paper from the total weight found,
whereby we arrive at the weight of the precipitate.
In other cases it becomes necessary to subject the precipitate
to ignition. This is performed by folding the paper, placing it
in a small tared platinum dish or crucible (12), and burning it
by means of a small Bunsen flame. In such instances a triangle
made of wire, the three sides of which carry small pieces of pipe-
clay, is employed. This is placed on an iron tripod over a Bunsen
flame ; the crucible containing the precipitate is then placed on
the top, and ignition proceeded with, it is at all times advisable
to employ a small flame, and to arrange it so that the tip of its
inner blue cone approaches to within an eighth of an inch of the
bottom of the crucible. Experience has shown, in fact, that
inattention to this, such as the application of a large flame which
excludes atmospheric air and hence prevents oxidation, may
necessitate the ignition of a precipitate for several hours,
and that even then the ignition may be imperfect and the
precipitate not thoroughly burnt.
With a platinum crucible this would result in considerable
damage and loss of weight, thus vitiating the result in a two-
fold way.
After burning off in the proper manner, the crucible is placed
under the desiccator, and when cool, weighed, the weight of the
ash of the filter paper being deducted from the weight thus found.
26. Filter Papers. It is always advisable to employ filter
papers of the purest kind, that is to say, as free as possible from
saline bodies. There are now several kinds on the market, which,
when subjected to ignition, leave practically no weighable
residue, and obviously they are the best to employ.
The author uses and prefers the Swedish papers manufactured
by J. H. Munktell, a box of which contains 500 papers, each of
which, when reduced to ash, leaves no weighable residue. With
other papers it is necessary to know the amount of ash they leave,
so as to deduct this from the weight of a precipitate. The ash
will be less, however, when the liquid filtered is acid ; for example,
when dealing with a precipitate of boric sulphate, the filtrate of
which is acid, 1 milligram would probably be the correct differ-
ence ; whilst for lime, the filtrate of which is alkaline, the same
paper would give an ash of 2 milligrams. It is advisable there-
fore to prepare unknown papers by steeping them over-night in
a 5 per cent, solution of hyrochloric acid, afterwards decanting
QUALITATIVE AND QUANTITATIVE ANALYSIS
29
the liquid and washing the papers with distilled water until the
washings are neutral to litmus. Upon then drying the papers
in the drying oven, they will invariably be found, upon ignition,
to give no appreciable residue.
27. Distillation. There
are several forms of distilling-
or condensing apparatus. Fig.
33 shows Keene's, employed in
beer analysis, which consists
of a copper tube, curved at
the top, to the end of which
is attached the distilling flask
D. The straight portion of
the tube is surrounded by
a strong metal jacket through
which cold water is passed
during distilling, the water
entering at A and leaving at
B. The distilling flask D is
heated by an Argand burner
E, and the distillate is col-
lected in a plain or graduated
flask C.
Another form of distilling
apparatus is Thorpe's (fig. 34),
whilst a further form of yet
more ancient date is the well-
known Liebig's (fig. 35), still
employed, particularly in water
28. Density and Specific
Gravity. According to the
principle of Archimedes, every
body immersed in a liquid is
submitted to the action of two
forces gravity, which tends FIG. 33.
to lower it, and the buoyancy
of the liquid which tends to raise it with a force equal to the weight
of the displaced liquid. The weight of the body is either totally
or partially overcome by this buoyancy, from which it is con-
cluded that a body immersed in a liquid loses a part of its weight
equal to the weight of the displaced liquid.
If we take the density of distilled water at a given temperature
\
OF THE
UNIVERSITY
OF
30
THE BREWER S ANALYST
to be the unit, the relative density of any other substance is the
ratio which the mass of any given volume of that substance at
that temperature bears to the mass of an equal volume of water.
Thus, it is found that the mass of any volume of platinum is
22'069 times that of an equal volume of water; conssquently, the
relative density of platinum is 22*069, and this relative density
of a substance is called its specific gravity.
In order, therefore, to calculate the specific gravity of a body,
it is sufficient to determine its weight and that of an equal
FIG. 34.
volume of water at the same temperature, and then divide the
first weight by the second ; the quotient is the specific gravity of
the body.
In taking the specific gravity of a liquid or solid body,
a temperature of 39 '2 F. (4 C.) is often chosen, this being the
temperature at which water is at its maximum density ; for
water, unlike most other substances which contract between this
temperature and the freezing-point 32 F. (0 C.), expands.
It is exceedingly inconvenient, however, to have to bring bodies
to such a low temperature, so in ordinary practice a more readily
attainable temperature is chosen, namely 60 F. (15*5 C.).
The specific gravity of gases, however, is determined at the
QUALITATIVE AND QUANTITATIVE ANALYSIS ' 31
temperature of the air at the time of performing the experiment,
and the volume the particular gas would occupy at any other
temperature is found by calculation.
It is obvious that in practical brewing operations a method
of arriving at the specific gravity of a solution, requiring a
balance, weights and a specific- gravity bottle, is quite out of the
question. Instruments were therefore devised which will show
the specific gravity of solutions when immersed therein.
These instruments hydrometers and saccharometers are
well known to the practical brewer ; for instance, we have the
Sykes hydrometer, the indications of which are simply in degrees
of specific gravity over the weight of water. Thus 20 Sykes
correspond to 1020 specific gravity. We have also the Bates
FIG. 35.
hydrometer, which deals with true specific gravity ; thus with the
smallest counterpoise attached, which is 1000, or equal to the
weight of water and floating in a liquid to the graduation mark
of 20 on the stem, the specific gravity is 1020.
We have also the hydrometer of Twaddell, so graduated that
real specific gravity may be deduced by a simple method from
the degrees indicated, viz., multiplying the latter by 5, and
adding 1000; the same being the specific gravity, water being
1000. Thus 5 Twaddell indicate 1025 specific gravity. Again,
we have two different instruments under the name of Baume, one
being for liquids heavier than water, the other for those lighter
than water, the specific gravity being calculated as follows :
To convert degrees Baume into specific gravity, deduct the
degree indicated from 144, and then divide 144 by the number
so found and multiply by 1000.
32 THE BREWER'S ANALYST
Thus to convert 20 Baume into specific gravity
144-20=124.
144 -r 124=1-16129.
1-16129 x 1000= 1161-29 specific gravity.
We have also the saccliarometer of Balling, graduated to indicate
the percentage of dry, solid matter in the liquid ; and the Dringe
and Page saccharometer, graduated to show pounds per barrel.
Thus water weighs 10 Ibs. to the gallon, so that a barrel of 36
gallons weighs 360 Ibs. Should a barrel of beer weigh 380 Ibs.,
the indication by the saccharometer would be 20 Ibs, that is, the
excess weight over the natural barrel of water.
To convert specific gravity as found by any of the former
mentioned hydrometers into pounds per barrel degrees, it is
merely necessary to multiply the excess weight over 1000 by '36
or divide by 2 '7 7. Whilst to convert pounds per barrel degrees
into specific gravity, all one has to do is to. multiply the pounds
per barrel by 2'77 or divide by -36 and add 1000.
Example :
1025 specific gravity - 1000 = 25 x "36 = 9 Ibs. per barrel.
1025 -1003 = 25-2-77 = 9
9 Ibs. per barrel x. 2'77 + 1000 = 1025 specific gravity.
9 -r "36 = 25 + 1000 = 1025
Although these instruments are essential in practical operations,
they are of little use in analytical work ; a pint of liquid is
necessary in order to immerse the instrument, and not only is
such a quantity seldom at hand in analytical operations, but
greater accuracy is necessary than these instruments are capable
of showing; hence in analytical operations the specific gravity
of a liquid is always ascertained by means of the specific-gravity
bottle.
Specific- Gravity Bottle. This instrument (fig. 36) consists of
a glass flask, generally made to contain some even quantity of
distilled water at 60 F. (15'5 C.), such as 25, 50, or 100 grams,
or 250, 500, or 1000 grains. An accurately ground stopper,
perforated by a fine hole, fits into the neck of the flask. The
liquid to be weighed is brought to the temperature of 60 F.
(15'5 C.), the bottle rinsed with it and then filled, and the stopper
fitted, care being taken to exclude air-bubbles. The bottle is
then wiped dry with a handkerchief, placed on the balance, and
weighed.
The object of the fine hole through the stopper is to allow for
QUALITATIVE AND QUANTITATIVE ANALYSIS Ii3
the expansion of the liquid which sometimes takes place owing
to the warmth of the atmosphere, or the hands when handling
the bottle. The position of the liquid
due to expansion thus finds its way
up the hole in the stopper, but pro-
vided the weighing be quickly per-
formed, the liquid on the top of the
stopper will not have had time to
evaporate before an exact weight is
obtained.
Before taking the specific gravity of
a liquid, we have first to ascertain the
weight of the bottle, both when empty
and when filled with distilled water, at FrG>
60 F. (15-5 C.); and knowing these
two factors, upon weighing any other liquid we obtain the specific
gravity by a single calculation.
Example :
Weight of bottle filled with wort . 90*960 grams.
Weight of empty bottle . . .21-810 ,,
Weight of wort . . 69*150
Weight of bottle filled with water . 86'260
Weight of empty bottle . . . 21 '8 10
Weight of equal volume of water to
that of wort . . . . 64*450
Wort 69-150 irw , fto
= 1072-92 specific gravity of wort.
Water 64-450
The specific-gravity bottle is usually purchased enclosed in a
tin box, the lid, which is arranged to hold a small weight, usually
containing shot (fig. 36). This weight is a counterpoise for the
weight of the empty bottle, so that in the above example the
specific- gravity bottle, filled with wort and placed upon the
balance, the counterpoise being placed upon the opposite scale
pan, would weigh 69*150 grams, which, divided by the weight of
water (64*450 grams), which has been previously ascertained and
noted so as to save a fresh calculation at each weighing, gives the
specific gravity. On the other hand, the specific-gravity bottle
may be purchased with a counterpoise, and to contain an exact
quantity of liquid such as 100 grams at 60 F. (15'5 C.), the
o
34
THE BREWER S ANALYST
weight of any liquid ascertained by its aid and in the manner
directed being, in such case, the specific gravity without any
calculation. Specific - gravity bottles, however, as purchased,
seldom contain exact quantities ; they are nevertheless at times
only slightly out, and in such cases, taking it that a bottle when
full contains 100*012 grams, with care the stopper may be
made smaller by rubbing with fine emery cloth, so as to fit
further into the bottle and the bottle thus made to hold exactly
100 grams. In like manner, if the bottle is found to contain
less than 100 grams, say
for instance 99*997, the
bottom of the stopper may
be slightly rubbed away
with emery cloth so as to
allow the extra volume to
be retained in the bottle
when the stopper is fitted.
29. The Centrifuge.
This instrument, more
commonly known as the
centrifugal machine (figs.
37, 38), has for many years
been employed by medical
men for the examination
of blood and urine, by
analysts for bacteriological,
microscopical, and other
purposes, and particularly
for testing milk.
It is employed in the brewer's laboratory for the rapid separa-
tion of suspended matter in beer.
The instrument (fig. 37) consists of an upright, which can be
clamped on to a table, with four short arms, which can be rotated
at extreme velocity by turning the toothed wheel communicating
with the screw of the upright. At the end of each arm hangs
a metal test-tube, into which slides a glass test-tube holding the
beer. When the machine is operated, the pendent tubes rise
towards the horizontal position, and the suspended matter in the
beer is driven in a compact mass by centrifugal force to the end
of the tube. It can then be examined microscopically, biologically,
and chemically.
Another form of the instrument is that shown in fig. 38. The
test-tubes are closed and placed round the dish in a horizontal
FIG. 37.
QUALITATIVE AND QUANTITATIVE ANALYSIS
35
position ; the lid is then lowered, and the dish rapidly revolved
by means of the strap or a piece of string.
With turbid beers it is often of great importance to know at
once the nature of the matter causing the cloudiness. Without
the centrifuge it is necessary to allow the suspended bodies to sub-
side which not only takes time, but may then be incomplete
or we may hasten subsidence by "forcing." Forcing, however,
brings about changes other than the mechanical separation of
FIG. 38.
suspended bodies, and these are not always required. Where,
therefore, it is desired to separate the suspended matter from
beers other than by fermentation and putrefactive changes which
are induced by forcing, the centrifuge becomes of value, and
enables us to gain information as to the nature of the organised
and amorphous matters suspended in the beer. Two or three
minutes' rotation of the apparatus is usually sufficient for the
purpose, but with very stubborn beers (such as those containing
budding primary yeast) a slightly longer time is often necessary.
It was shown by H. Tikes l seven years ago that micro-organisms
1 Allgem. Zeitschr. Bierbrau. und Malzfabrik., 1900, 28, 1-2.
36 THE BREWER'S ANALYST
can be rapidly separated from beer and other liquids by means of
the centrifuge, and it is due to him that the instrument has
become a valuable adjunct to the brewer's laboratory.
Sterilised solutions containing equivalent amounts of potash
alum and sodium carbonate were prepared, and a snail quantity
of each added to the liquid to be treated. After the evolution of
the carbon dioxide the mixture was spun in a centrifuge until the
gelatinous precipitate collected at the bottom of the tube.
The supernatant liquid was then poured off and the precipitated
alumina was then dissolved in 1 c.c. caustic soda, which had
practically no effect on the bacteria present, and the solution
examined under the microscope. By this process it was possible
FIG. 39.
to remove 89-90 per cent, of the organisms from beer and 96-100
per cent, of added organisms from water.
30. The Tintometer. This well-known instrument (fig. 39)
consists of a binocular tube B, terminating at the object end H
in two small square holes. The instrument is arranged to be
raised or lowered on the stand A and fixed in position as shown,
A 3 . At F a square of opaque unglazed porcelain is fixed.
Supplied with the instrument for brewers' purposes are two cells
or metal boxes, fitted at opposite sides with glass, one being
known as the 1-inch cell, the other the J-inch cell. A sample of
beer, caramel, sugar, or other solution to be tested is placed in
one of the cells, and the cell is then placed in position on the left
side of the instrument H. Upon looking through the tube at C
the colour of the solution is distinctly seen, and 'the object now is
to match the colour. For this purpose a series of yellow glasses,
known as the 52 series, are supplied with the instrument. These
glasses range from a decimal or from 1 degree in equal gradation
QUALITATIVE AND QUANTITATIVE ANALYSIS 37
up to any desired number. For instance, glass number 2 is of
double the colour intensity of glass number 1, or glasses numbered
4 and 6 equal in intensity the colour glass number 10. These
glasses are taken and slipped into the instrument at J, so that
upon looking through the tube at C the colour of both the
glasses and the solution are viewed, the glasses being added until
the colour of the solution is matched.
The numbers of the glasses are then read and added together,
and the colour value expressed as of so many degrees. For example,
if glasses 8, 11, and 12 were required to match the colour of the
solution in a 1-inch cell, the colour would be registered as equal to
31 in 1' cell. The author carried out a series of experiments
with this instrument in 1888, almost as soon as it was introduced,
and may here, with slight alteration, repeat the same as then
published. 1
.... The colour of beer is of great importance, since
uniformity in this direction is greatly admired by most consumers.
In order, therefore, to turn out beers day by day of constant
colour uniformity in accordance with their respective quality, some
form of instrument is useful, and we here refer to Lovibond's
Tintometer.
This instrument answers a chain of questions which are
interesting and necessary to the brewer, beginning with the
colour of a percentage solution of malt in relation to that of the
worts before and after boiling, to the registration of the colour of
the beer. A few estimations of colour in malt will lead to a
practical knowledge of character and evenness in drying ; it will
soon be ascertained what colour in malt produces a given colour
in ale, and what quantity of black malt or caramel is required to
produce a beer of definite colour intensity. Experiments carried
out with the tintometer were as follows :
Degrees of Colour.
1-inch cell.
Pale malt, 5 per cent, solution . . . .3
Wort before boiling, 1050 specific gravity . .10
Wort after boiling . . . . . .14
Finished beer .... . 13
Finished beer after storing 3 weeks . . .11
The above are the observations of an actual brewing, the
ultimate eleven degrees of colour being about that of the Burton
pale ale.
The instrument is also of great value in estimating roasted
1 Brewers' Guardian, Feb. 21, 1888.
38 THE BREWER'S ANALYST
malts and caramels, where the value bought is primarily colour,
the variations between samples very similar in outward judgment
being sometimes very wide :
Roasted Malt.
Degrees of Colour.
No. 1. Black, 1 per cent, solution J thickness 1\
No. 2. Chocolate, ,, 10
These observations show the large difference in colour value
between two samples of which the difference in price was very
trifling.
PART II.
THE POLARIMETER.
POLARISATION OF LIGHT SPECIFIC ROTATORY POWER SOLUTION
WEIGHT AND SOLUTION FACTORS CUPRIC OXIDE REDUCING
POWER.
SOME twenty years ago the Polarimeter, or " Polariscope " as it
was then incorrectly called, was looked upon and described by
those who had but little, if any, knowledge of its use, as a
" pretty but useless chemical toy." With the rapid strides that
have since been made in the science of brewing, the polarimeter
has become an indispensable instrument, and has played a
wonderful part in enabling those who have worked upon starch-
conversion products to define many points, particularly with
regard to the composition of the so-called malto-dextrins.
That the polarimeter is a most useful apparatus to the brewer,
and one which, without any laborious or tedious experimenting,
enables him to estimate the conversion products of his mashes,
apart from its value in numerous other well-known directions, is
now a recognised fact. As, therefore, it is essential that the
modern brewer should become familiar with the instrument, it is
necessary that we sketch the principle upon which it is based,
and then describe its construction.
The principle of the instrument depends upon the polarisation
of light.
Polarisation Of Light. There are four processes by means
of which a ray of light may be polarised : these are reflexion,
ordinary refraction, double refraction, and scattering by small
particles.
It will be convenient, however, to reproduce the description of
the phenomena of polarisation as given by Spottiswoode, 1 who
1 Polarisation of Light, Macmillan & Co.
39
40 THE BREWER'S ANALYST
starts with a plate of crystal called tourmalin as an instrument,
tolerably simple in its action and easy of manipulation :
"Tourmalin is a crystal, of which there are several varieties,
differing only in colour. Very dark specimens generally answer
the purpose well, excepting that it is difficult to cu'u them thin
enough to transmit much light. Red, brown, or green specimens
are usually employed ; the blue are, for the most part, optically
unsuitable. Some white, or nearly white, specimens are very
good, and may be cut into thicker plates without loss of
light.
" If we take a plate of tourmalin, cut parallel to a particular
direction within the crystal called the optic axis, and interpose it
in the path of a beam of light at right angles to the direction of
the beam, the only effect perceptible to the unassisted eye will
be a slight colouring of the light after transmission, in conse-
quence of the natural tint of the particular piece of crystal.
But if we examine the transmitted beam by a second similar
plate of tourmalin placed parallel to the former, the following
effects will be observed : When the two plates are similarly
placed, i.e. as if they formed one and the same block of crystal,
or, as it is technically expressed, with their optic axes parallel,
we shall perceive only, as before, the colouring of the light due
to the tints of the two plates. But if either of the plates be then
turned round in its own plane so as always to remain perpen-
dicular to the beam, the light will be observed to fade gradually
until, when the moving plate has been turned through a right
angle, the light becomes completely extinguished. If the turning
be continued beyond the right angle, the light will begin to
revive ; and when a second right angle has been completed, the
light will be as bright as at the outset. In figs. 40 and 41, a, b,
c -> d, e, j\ g, h represent the two plates. In fig. 40 the two plates
are supposed to be in the first position ; in fig. 41 the plate e, /,
g, h has been turned through a right angle.
" Of the parts which overlap, the shading in fig. 40 represents
THE POLARIMETER 41
the deepened colour due to the double thickness of the crystal ;
in fig. 41 it indicates the complete extinction of the light. The
same alternation of brightness and extinction will continue for
every right angle through which the moving plate is turned.
Now it is to be observed that this alternation depends only upon
the angle through which one of the crystals has been turned, or,
as it is usually stated, upon the relative angular position of the
two crystals. Either of them may be turned, and in either
direction, and the same sequence of effect will always be produced.
But if the pair of plates be turned round bodily together, no
change in the brightness of the light will be made. It follows,
therefore, that a ray of ordinary light possesses the same properties
all round ; or, as it may be described in more technical language,
a ray of ordinary light is symmetrical in respect of its properties
about its own direction. On the other hand, a ray of light, after
traversing a plate of tourmalin, has properties similar, it is true,
on sides or in directions diametrically opposite to one another,
but dissimilar on intermediate sides or directions. The properties
in question vary, in fact, from one angular direction to another,
and pass through all their phases, or an entire period, in every
angle of 180. This directional character of the properties of the
ray, on account of its analogy to the directional character of a
magnet or an electric current, suggested the idea of polarity j and
hence the condition in which the ray was found to be was called
polarisation.
"Having so far anticipated the regular order of things on the
experimental side of the subject, it will be worth while to make a
similar anticipation on the side of theory. It is considered as
established that light is due to the vibrations of an elastic
medium, which, in the absence of any better name, is called ether.
The ether is understood to pervade all space and all matter,
although its motions are affected in different ways by the mole-
cules of the various media which it permeates. The vibrations
producing the sensation of light take place in planes perpendicular
to the direction of the ray. The paths or orbits of the various
vibrating ethereal molecules may be of any form consistent with
the mechanical constitution of the ether ; but, on the suppositions
usually made, and none simpler have been suggested, the only
forms possible are the straight line, the circle, and the ellipse.
But in ordinary light the orbits at different points of the ray are
not all similarly situated ; and although there is reason to believe
that in general the orbits of a considerable number of consecutive
molecules may be similarly situated, yet in a finite portion of the
42
THE BREWER'S ANALYST
ray there are a sufficient number of variations of situation to
prevent any preponderance of average direction.
" This being assumed, the process of polarisation is understood
to be the bringing of all the orbits throughout the entire ray
into similar positions. And in the case of the tourmalin plate
the orbits are all reduced to straight lines, which consequently
lie in one and the same plane. For this reason the polarisation
produced by tourmalin, as well as by most other crystals, is
called rectilinear, or, more commonly, plane polarisation. This
property of tourmalin may also be expressed by saying that it
permits only rectilinear vibrations parallel to a particular
direction, determined by its own internal structure, to traverse it.
" Adopting this view of polarisation as effected by a plate of
tourmalin, it would be interesting to ascertain the exact direction
of the vibrations. And a simple experiment will go far to satisfy
a
o n
FIG. 42.
us on that point. The argument, as now stated at least, is
perhaps based upon general considerations rather than upon
strict mechanical proof; but the experimental evidence is so
strong that it should not be denied a place here. Suppose for a
moment that the tourmalin be so placed that the direction
of vibration lies either in or perpendicular to the plane of
incidence (that is, the plane containing the incident ray, and
perpendicular to the surface on which it falls at the point of
incidence) ; then it is natural to expect that vibrations executed
in the plane of incidence will be far more affected by a change
in the angle of incidence than those perpendicular to that plane.
In fact, the angle between the direction of the vibrations and the
surface upon which they impinge will in the first case vary with
the angle of incidence, but in the second case it will remain
unchanged. In fig. 42, n o represents the ray of light ; the
arrow the direction of vibration ; a, b, c, d, a', t/, c, d' the plate
in two positions, turned in the first instance about the direction
of vibration, in the second about a line perpendicular to it.
"Dismissing, then, the former supposition, and supposing that
nothing whatever is known about the direction of vibration, then,
THE POLARIMETER 43
if all possible directions be taken in succession as pivots about
which to tilt or turn the second tourmalin, it will be found that
for one direction the intensity of the light diminishes more
rapidly with an increase of tilting (or, what is the same thing,
with an increase of the angle of incidence) than for any other.
And, further, that for a direction at right angles to the first, the
intensity of light diminishes less than for any other, while for
intermediate directions the diminution of intensity is intermediate
to those above mentioned. In accordance, therefore, with what
was said before, we may conclude that the vibrations are parallel
to the line or pivot about which the plate was turned when the
diminution of light was least.
" Secondly, polarisation may be effected by reflexion. If light
reflected from the surface of almost any, except metallic, bodies
be examined with a plate of tourmalin, it will in general be found
to show traces of polarisation ; that is to say, if the plate of
tourmalin is caused to revolve in its own plane, and the reflected
rays be viewed through it, then in certain positions of the plate
the reflected light will appear less bright than in others. If the
angle at which the original rays fall upon the reflecting surface
be varied, it will be found that the amount of alteration in
brightness of the light seen through the revolving tourmalin (or
analyser) will also vary. This fact may also be expressed thus :
In polarisation by reflexion, the degree of polarisation, or the
amount of polarised light in the reflected rays, varies with the
angle of incidence on the reflecting surface. But at a particular
angle, called on that account the polarising angle, the polarisation
will be a maximum. This angle (usually measured between the
incident ray and perpendicular to the reflecting surface) is not
the same for all substances ; in fact, it varies with their refractive
power according to a peculiar law, which may be thus enunciated :
The tangent of the polarising angle is equal to the refractive
index. Simple geometrical considerations, combined with the
usual expressions for the laws of reflexion and refraction, will
show that this relation between the polarising angle and the
refractive index may be also expressed in the following way : If
light be incident at the polarising angle, the reflected and refracted
rays will be at right angles to one another.
"In fig. 43, si represents the incident, if the reflected, and in
the refracted ray. Then si will be incident at the polarising
angle when the angle fin is a right angle.
" An apparatus devised by Tyndall for experimentally demon-
strating the laws of reflexion and refraction is admirably adapted
44
THE BREWER'S ANALYST
for verifying this law. The following description is quoted from
his Lectures on Light : ' A shallow circular vessel RIG (fig. 44),
with a glass face, half filled with water rendered barely turbid
by the admixture of a little milk or the precipitation of a little
mastic, is placed upon its edge, with its glass face vertical. By
means of a small plane reflector M, and through a slit I in the
hoop surrounding the vessel, a beam of light is admitted in any
required direction.'
" If a little smoke be thrown into the space above the water,
the paths of the incident, the reflected, and the refracted beams
will all be visible. If, then, the direction of the incident beam
be so adjusted that the reflected and the refracted beams are at
right angles to one another, and a NicoPs prism be interposed in
FIG. 43.
the path of the incident beam, it will be found that, by bringing
the vibrations alternately into and perpendicular to the plane of
incidence, we shall render the intensity of the reflected and
refracted rays alternately a minimum.
" Thus much for the verification of the law. But not only so ;
if we take different fluids, and for each of them in succession
adjust the incident beam in the same manner, we shall only have
to read off the angle of incidence in order to ascertain the
polarising angle of the fluid under examination.
" The general theory of the reflexion and refraction of polarised
light was first established by Fresnel, who based it upon the four
following suppositions :
" (1) That the ether, to the vibrations of which light is supposed
to be due, is regarded as perfectly elastic, so that the whole of
the motion taking place at the source of light is transmitted
without loss throughout the ray. This appears to be substantially
THE POLAKIMETER 45
true in transparent media; but in proportion as a substance is
more opaque, so do its molecules take up part of the motion of
the ether, and convert the light into heat (the principle of vis
viva).
" (2) That in passing from one medium to another, although the
velocity and extent of the motion may change, yet its character
is not altered (the principle of continuity).
" (3) That any change in velocity or in extent, due to the
passage from one medium to another, takes place immediately at
the surface of separation ; and that such change is maintained
subsequently.
" (4) That while the elasticity of the ether in different bodies re-
mains the same, its density may differ.
" By means of these ^ ,,
suppositions relations
were established be-
tween the intensity of
the reflected and re-
fracted rays on the one
hand, and the angles of
reflexion and refraction
on the other, from which
many phenomena pre-
viously known only as
experimental facts were
deduced as conse-
quences. Of these, one FIG. 44.
should be mentioned,
viz., that in the case of vibrations in the plane of incidence, if
the ray be incident at such an angle that the reflected and
refracted rays are perpendicular to one another, there can be no
reflected ray.
" We next come to the subject of polarisation by double
refraction.
"There are a large number of crystals which have the property
of generally dividing every ray which passes through them into
two. But the extent of separation of the two rays varies with
the direction of the incident ray in reference to the natural
figure of the crystal. In every double refracting crystal there
is at least one, and in many there are two, directions in which
no separation takes place. These directions are called optic axes.
" Of such crystals Iceland spar (crystallised carbonate of lime)
is the most notable instance. If we take a block of such spar
46
THE BREWERS ANALYST
split into its natural shape, a rhombohedron, fig. 45, and for
convenience cut off the blunt angles by planes perpendicular to
the line joining them, ab, it will be seen that a ray of light
transmitted perpendicularly to these planes, that is, parallel to
the line joining the blunt angles, is not divided. In fact, the
image of an object seen by the eye in the direction in question
appears single, as if passed through a block of glass. The
direction in question (viz. the line a b itself, and all lines passing
through any part of the crystal parallel to a b) is called the optic
axis of the crystal.
"If, however, the crystal be tilted out of this position in any
direction, it will be seen, by the appearance of two images instead
of one, that the rays are divided into two. The angular diver-
gence of the two sets of rays, or, what comes to the same thing,
the separation of the two images, depends upon the angle through
FIG. 45.
which the crystal has been turned ; or, as it may also be expressed,
upon the angle between the directions of the incident ray and the
optic axis of the crystal. When this angle amounts to a right
angle the separation is at its greatest; and if the crystal be
still further turned, the images begin to come together again
until, when it has turned through another right angle, they
coincide.
" This process of separation, or doubling the rays, is called double
refraction, and the character of the polarisation of two images is
best studied by using flat instead of curved surfaces for separating
the rays.
"For the purpose in question there is, perhaps, no better
instrument than the double-image prism. This consists of a
combination of two prisms, one of Iceland spar, so cut that
the optic axis is parallel to the refracting edge; the other of
glass, and usually having a refracting angle equal to that of
the spar.
" The rays passing through the crystal prism being perpendicu-
THE POLARIMETER
47
lar to the optic axis, undergo the greatest separation possible.
And the chromatic dispersion caused by that prism is usually
corrected or neutralised entirely in the case of the extraordinary,
and nearly so in that of the ordinary, ray by the glass prism,
which is placed in a reverse position. In this arrangement the
extraordinary image occupies the centre of the field, and remains
fixed when the double-image prism is made to revolve in a plane
perpendicular to the incident rays ; while the ordinary image is
diverted to a distance from the centre, and revolves in a circle
about that centre when the prism revolves.
" Other dispositions of the double-image prism are also made for
particular purposes ; e.g. in which neither image is central, and in
which the chromatic dispersion of both images is partially
corrected. If the nature of the light in the two images thus
formed be examined by any polarising instrument,
it will be found that it is polarised in both cases,
and that the vibrations in the one image are
always perpendicular to those in the other. And
in particular, the vibrations in the extraordinary
image are parallel and those in the ordinary are ,,
perpendicular to the optic axis.
" On these principles polarising and analysing
instruments have been constructed by various
combinations of wedges or prisms of Iceland spar,
the details of which it is not necessary to describe
in full. But the general problem and object pro-
posed in all of them has been to cause such a
separation of ordinary and extraordinary rays that
one set of rays may, by reflexion or other methods, be further
diverted, and afterwards thrown altogether out of the field of
view. This done, we have a single beam of completely polarised
light, and a single image produced from it.
" One such instrument, however, the Nicol's prism, named after
its inventor, a clever optician, on account of its great utility and
its very extensive use, and which is to be found in all polarimeters,
must be described. A rhombohedron of Iceland spar, double of
its natural length, is taken (fig. 46) ; and one of its terminal faces
P, which naturally makes an angle of 71 with the blunt edges
K, is cut off obliquely so as to give the new face, say P', an
inclination of 68 to the edges K. The whole block is then
divided into two by a cut through the angle E in a direction at
right angles to the new face P'; the faces of this cut are then
carefully polished, and cemented together again in their original
FIG. 46.
48
THE BREWER'S ANALYST
position with Canada balsam. Fig. 47 represents a section of
such a prism made by a plane passing through the edges K. A
ray entering as a b is divided into two, viz. b c the ordinary and
b d the extraordinary. But the refractive index of the Canada
a balsam is 1 '54, i.e. intermediate between that of
the spar for the ordinary (1'65) and the extra-
ordinary (the minimum value of which is 1'48)
rays respectively; and in virtue of this the
ordinary ray undergoes total reflexion at the
surface of the balsam, while the extraordinary
passes through and emerges ultimately parallel
to the incident ray. Fig. 48 shows an end view
of a Nicol's prism P P, representing the plane of
polarisation of the emergent polarised ray.
"Two such instruments, wheri used together,
are respectively called the " polariser " and the
"analyser," on account of the purposes to which
they are put. These, when placed in the path
of a beam of light, give rise to the following
phenomena, which are, in fact, merely repro-
ductions in a simplified form of what has
gone before.
" When polariser and analyser are placed in front of one another
with their shorter diagonals parallel, that is, when the vibrations
in the image transmitted by the one are parallel to those in the
image transmitted by the other, the light will be projected exactly
as if only one instrument existed. If, however, one instrument,
say the analyser, be turned round,
the light will be seen to fade in
the same way as in the case of the
tourmalin plates; until, when it has
been turned through a right angle,
or, as it is usually expressed, when
the polariser and analyser are crossed,
the light is totally extinguished.
" In the complete apparatus or
polarimeter we may incorporate any system of lenses, so that we
may make use of either parallel or convergent light, and finally
focus the image produced."
Now various substances have the property of rotating polarised
light, as, for example, turpentine and sugar solutions of various
kinds, such as dextrin, maltose, dextrose, etc. If, therefore, we fill
a glass tube with turpentine or with a certain percentage sugar
FIG. 48.
THE POLARIMETER 49
solution, place the tube in the polarimeter and then look through
the telescope, it will be noticed that the two halves of the field
are unequally illuminated, being darker on one side than on the
other. By now adjusting the instrument so that both halves of
the field are evenly illuminated, the exact angle of rotation can
be read off from the vernier scale. Of the various substances
which are optically active, some turn the polarised ray to the
right, and are known as right-handed, dextro-rotatory, or positive
substances, whilst others bend the ray to the left, and are known
as left-handed, levo-rotatory, or negative bodies; the signs +
and - being used to briefly designate each kind. All solutions
of an optically active substance of the same strength, when tra-
versed by the polarised ray in layers of the same thickness, rotate
the ray, each substance having a definite power. When this is
calculated upon a certain definite strength of solution, and upon
a layer of such solution of a definite thickness, an expression is
found which is termed the "specific rotatory power" or the
"opticity"of the substance. The function, then, of the polari-
meter is to determine the amount of rotation which the polarised
ray suffers in passing through a layer of the solution of an
optically active substance.
From this, by taking certain other factors into account, the
specific rotatory power of the substance can be found ; and when
the specific rotatory power of a substance present in solution is
known, the polarimeter enables us to estimate its amount.
It is not within the scope of this work to describe the subject
at greater length ; suffice it to say that the polarisation of light is
undoubtedly one of the most intricate but at the same time most
beautiful branches of the science of optics. For full information
the reader should consult the latest work, viz. The Optical Rota-
tion of Organic Substances, by Professor Landolt. 1
The Polarimeter. There are several differently constructed
polarimeters, such as the Soleil or Ventzke-Scheibler ; the Lippich ;
Laurent; Schmidt & Haensch Half -Shadow instrument, and
others ; but the two most commonly used forms are the Laurent
and Schmidt & Haensch Half-Shadow. With the latter a white
light illumination from oil or gas is employed, but with the
former a sodium flame illumination is used.
Specific rotatory power, as determined in reference to the D
ray of the solar spectrum (that is, with the sodium flame), is
indicated by [a] D , whilst when determined by the older forms
1 Translated from the German by Dr Long. The Chemical Publishing Co..
Easton, Pennsylvania.
4
50
THE BREWER'S ANALYST
of instrument, such as the Ventzke-Scheibler, it is indicated
by [a],
In the Laurent polarimeter which is shown, fig. 49, F
indicates the telescope, I I the magnifying glasses, n n the two
verniers, K the graduated dial, A a prism of Iceland spar known
as the " analyser," or analysing Nicol, which is fixed to the revol-
ving dial K and to the telescope, and capable of being rotated on
its axis by means of the milled head T seen underneath it. It
carries with it the two verniers n n, which indicate the observed
rotation on the scale of the dial-plate K.
FIG. 49.
Next comes the trough B E, with a lid, in which the tube
50) filled with the solution to be examined is placed.
P is the movable " polariser " (another prism of Iceland spar;),
which converts one half of the ordinary light passing through;jl
into polarised light, the other half being reflected to the side aflfl'
absorbed. Above it is a fixed graduated segment of a circle h. At
G is a thin plate of quartz, covering half the field, known 'as
Laurent's plate, its function being to increase the delicacy of^jtfre
indications of the instrument, and at S is placed a bichromate
plate.
The apparatus can only be used in conjunction with a sodium
THE POLARIMETER 51
flame, and a suitable sodium lamp is supplied with it. This con-
sists of a burner supplied with a small piece of platinum wire, on
which some pulverised chloride of sodium is placed and made
intensely incandescent by means of the non-luminous flame from
the burner ; the apparatus is pointed to the most intense part of
the yellow flame, which can be done easily by means of an
adjuster with which the lamp is provided.
The lamp is placed a few inches away from the end of the
telescope, and observations are taken in a darkened room or
cupboard.
The observation tubes (fig. 50) are made of glass, their ends
being ground perfectly true. A brass cap attached to each end
enables the tubes to be closed water-tight with small circular
glass plates, which are retained in position by the screw-caps.
The length of the tubes usually employed are 1 and 2 decimetres
(100 and 200 millimetres) ; an extra 2-decimetre tube, jacketed for
invert-sugar determinations, being very useful.
FIG. 50.
If the liquid to be examined is dark in colour, a decimetre
(100 mm.) tube is used; whilst if sufficiently pale a 2-decimetre
(200 mm.) tube is employed by preference, since the longer the
tube the larger the reading and the smaller the chance of error.
It becomes necessary, however, in some instances to decolorise a
solution before it is possible to take a reading. Decolorisation is
usually effected by either passing the solution repeatedly through
animal charcoal or by adding basic lead acetate solution and
then filtering : examples are given hereafter.
In using the instrument, the lamp is lighted and the flame
adjusted to position. On looking through the eye-piece a circle
of light is seen divided into two halves by a vertical line, and both
halves of the field of view should be exactly equally illuminated.
For this purpose the telescope F is, by drawing it out or pushing
it together, focussed on the Laurent plate. If the graduated dial
is now turned round 3 or 4 degrees to the right of the zero line
it will be seen that one half of the field of view will become
lighter, the other half darker. The same will be observed on
turning it round to the left. That position, however, exactly
between these, when both halves of the field of view are equally
illuminated, is the zero position of the instrument, and the
52 THE BREWER'S ANALYST
latter is first so adjusted that the zero line of the circle
coincides with the zero line on the vernier. The half-shadow
can now be made lighter or darker, according as the polariser
is turned more or less to the right or left of the zero line,
by means of the pointer reaching beyond the dial-segment.
When the pointer is in the zero position the Laurent's plate
and the polarising Nicol have the same wave direction, and
consequently, if at the same time the analyser is placed in the
zero position, both halves of the field of view appear black. The
nearer the pointer is to the zero line, the darker the half-shadow
will be, and the more sensitive the apparatus ; but when the
solution being examined is not quite transparent, the pointer
must be moved more or less away from the zero line, so that the
field of view is clear. For the majority of experiments the
position of the pointer at 7 J is most suitable ; the apparatus is
therefore usually so adjusted that in this position the dial and
vernier read exactly 0. When the pointer is moved, of course,
the zero point of the apparatus changes and no longer corresponds
with the zero line of the dial. The difference between the latter
and the zero position of the apparatus must either be taken into
account this is the most simple way or else, after the graduated
dial has been moved to 0, the apparatus must be again placed in
the zero position ; to do this, the analysing Nicol is turned by
means of the screw T so far to the right or left until both half-
shadows are equal.
Having adjusted the instrument, if we now take a 2-decimetre
(200 mm.) observation tube, fill it with a 10 per cent, solution
of cane-sugar and place it in the instrument, it will be found on
examination that both halves of the Held of view are unequally
illuminated. On turning the index by means of the milled-head
in the same direction as that in which the hands of a clock move
( + ), a position will be reached when both halves of the field are
equally illuminated. When this position is reached, the reading
of the scale indicates exactly the amount of twisting or rotation
which the polarised beam of light has undergone in passing
through a layer of 10 per cent, cane-sugar solution 2 decimetres
(200 mm.) thick; and from this can be deduced the specific
rotatory power or opticity of the solution as before mentioned.
It often happens, especially during the time when the apparatus
is first taken in use, that a circumstance is mistaken for the zero
position of the apparatus which arises when the circle has been
turned too far and has gone beyond the sensitive range. In this
case the light is also to a certain extent equal, but will hardly
THE POLARIMETER
53
change if the circle is turned round 10, 15 or even more degrees.
Special attention must, therefore, be given to this circumstance,
especially after the fluid Jias been filled into the tube and the
latter placed in the apparatus, that a sudden change of light and
dark is not to be observed in both halves of the field of view
when, as described, the circle is turned a few degrees either to the
right or to the left of the zero line. When the tube has been
placed in the apparatus, the first thing to do is to again adjust
FIG. 51.
the telescope exactly, so that the field of view is again clear and
divided into two halves by the vertical line ; then the circle is
turned round until the half-shadows on both halves are the
same, and the result is then read off the scale on the circle.
The graduated dial is graduated right round, that is, into 360
degrees, and, by means of the vernier attached to the index, can
be read to the sixtieth of a degree.
The Lippich polarimeter shown (fig. 51) is somewhat similar
in construction to the Laurent just described, excepting that a
bichromate solution is employed instead of the bichromate glass.
54 THE BREWER'S ANALYST
With the Schmidt and Haensch Half-shadow Polari
HieteP. The scale is entirely different from that of the Laurent.
As the instrument was constructed specially for the use of
sugar manufacturers and refiners, its scale is constructed so as to
show percentages of cane-sugar directly. It has consequently 100
divisions, which by means of the vernier can be read to tenths of
a division. When the 2-decimetre tube is filled with a solution,
100 c.c. of which contains 26*048 grams of pure cane-sugar, the
instrument indicates 100 scale divisions. If an impure sugar is
employed for making the solution, and with this the reading is
75 '8 divisions, then such a sample contains only 75 '8 per cent, of
cane-sugar. Owing to this difference in the scales of the two
instruments, it is necessary, in order to convert half-shadow
degrees into Laurent degrees, to multiply by a factor. The
divisions of the scale of the instrument bear a fixed relation,
however, to the degrees of a sodium-light or Laurent polarimeter.
Each single division is equal to 0'34f>9 of a degree of the Laurent
instrument for the ordinary carbohydrates, excepting cane-sugar,
for which each division of the scale is equal to 0'3469 of a
degree. When therefore the half-shadow instrument is employed
to determine the specific rotation of a carbohydrate, multiply by
0*3459 for all carbohydrates other than cane-sugar, in order to
convert the observed scale divisions into angular degrees for
sodium light; in the case of cane-sugar multiply by 0*3469.
In order to convert divisions of the half-shadow instrument
into degrees [a]j, multiply by 0*3843 for all carbohydrates
other than cane-sugar; in the case of cane-sugar, multiply by
0*3854.
Lastly, the phenomenon of " mutarotation " or " bi-rotation "
must be mentioned ; that is to say, the varying opticity of certain
solutions. For instance, freshly prepared solutions of invert-
sugar or maltose show abnormal rotation; in the former
solution the rotation being above, in the latter below, normal.
In either case the solution may be immediately rendered normal
by either the addition of a very small amount of alkali (0*1 per
cent.) or by boiling. Care must be taken not to overlook this
point when analysing worts or freshly prepared solutions con-
taining maltose, dextrose, or levulose. 1 Observations should
also always be made with the solution to be examined at a
definite temperature, 68 F. (20 C.) being most usually
employed.
1 For recent views concerning muta rotation, see H. E. Armstrong,
"Studies on Enzyme Action," Jnl. Chem. &oc., 1903, Ixxxiii., 1310.
THE POLARIMETER 55
SPECIFIC lioTATORY POWER OR OPTICITY.
By the above terms is meant the angle indicated by the
polarimeter when a layer of the substance, 1 decimetre (100
mm.) in thickness, is examined in that instrument. For instance,
when a decimetre tube is filled with turpentine and examined on
the Laurent polarimeter, the reading is 22'4 ; this number, divided
by the specific gravity of the turpentine, gives directly the specific
rotatory power of that particular turpentine.
The specific rotatory power of an optically active substance in
solution is denned as the angle through which a plane polarised
ray of light of definite refrangibility is rotated by a column of
liquid, 1 decimetre in length, containing 1 gram of the sub-
stance in 1 c.c.
It is obvious that a 100 per cent, solution chus indicated could
not be used, and we therefore employ a 10, 20, or other per cent,
solution, and calculate to 100 per cent. If, for instance, a 10
per cent, solution of pure cane-sugar be examined in a 1-deci-
metre tube, the angle observed will be 6*66, and the multiplication
of this figure by 10 will give the opticity of cane-sugar = 66'6.
If instead of a 10 per cent, solution, one of 20 per cent, is
employed, the angle observed will be twice as large, and will,
consequently, have to be halved before being multiplied by 10.
Should the 2-decimetre (200 mm.) tube be employed, then
the reading will have to be halved and multiplied by 5. The
opticity is obtained in any case by the following equation :
R
T
Lx Too
in which R is the reading of the polarimeter, L the length of the
tube employed in decimetres, and G the number of grams
of substance contained in every 100 c.c. of the solution.
For instance, suppose we have a solution containing in every
100 c.c. 13'5 grams of a body, the opticity of which we wish to
determine, and upon examining in the 2 decimetre tube we
obtain a reading of + 42*5", then
The opticity or specific rotatory power of such a solution is
therefore [a] D = +157*4.
56 THE BREWER'S ANALYST
When the specific rotatory power of a solution is known, the
quantity of that substance in solution is readily determined with
the polarimeter by the aid of the following formula :
G is the number of grams of the substance in 100 c.c. of solu-
tion, R the observed angle, and [a] D the opticity of the substance,
L being the length of the observation tube in decimetres.
For example, a solution of cane-sugar of unknown strength is
found to give a reading of + 18 '20, then
Every 100 c.c. of the solution, therefore, contains 13'66 grams
of cane-sugar.
Again, supposing we have a solution containing maltose and
dextrin, and we desire to ascertain the amount of each of these
bodies present in the solution. Knowing as we do the opticity
of maltose and of dextrin, we proceed thus :
The solution is found to contain, say, 15*5 grams per 100 c.c.
of the mixture of maltose (opticity [a] D + 13S), and dextrin
([a] D + 198'9). On examining the solution in a 2-decimetre
tube, the angle observed is +52'90. Then
J. -M.+170... .
2x TOO
From this number, which is the opticity of the mixed substances,
we have to subtract the opticity of that which has the less
rotatory power in this case it will be maltose 138 and divide
the result by the difference of the rotatory powers of the two
bodies, which here is 60'9 (198'9-138).
This will be 170-6-138 = 32-6, and ^ = 0'53 gram dextrin.
60'9
Each gram of substance in solution consists therefore of 0'53
gram of dextrin and 0"47 gram of maltose ; consequently the
15 '5 grams contain 8 '2 15 grams of dextrin and 7 '285 grams of
maltose.
Lastly, to convert degrees [a] D into [a] j5 multiply by 1-111 or
simply add one-ninth.
To convert degrees [a]j into [a] D , multiply by '9 or simply
deduct one-tenth.
THE POLARIMETER
57
The following are the specific rotatory powers of the carbo-
hydrates according to Brown, Morris, and Millar. 1
TABLE SHOWING THE SPECIFIC ROTOTARY POWERS OF THE
CARBOHYDRATES.
Substance.
Formula.
Specific rotatory
power (absolute).
Specific rotatory
power reduced to
the common
divisor 3 "86.
[*)
IXb
t a ]l3'86
E
Dextrin . . (C 12 H 20 10 ) n
+ 221
+ 198-9
+ 216
+ 194*
Cane-sugar . C^H^n
+ 73-8
+ 66-6
+ 74
+ 66-8
Maltose . . ,,
+ 153-3
+ 138
+ 151
+ 135-9
Lactose (anhyd. ) ,,
+ 61-6
+ 55'4
+ 59-6
+ 53-6
Lactose (cryst. ) . C^H^OnHoO
+ 58-5
+ 52'6
+ 56't)
+ 50-9
Dextrose .
C 6 H 12 6
+ 57
+ 51-3
+ 57-4
+ 517
Levulose .
-106
- 95-4
-104-1
- 937
at 15-5 C.
at 15 -5 C.
I n vert- sugar . C 6 H 12 6 +
- 24-5
- 22
- 24-4
- 21-9
C 6 H 12 6
at 15 '5 C.
at 15-5 C.
Iii this table it will be noticed that the absolute specific
rotatory power is given, as well as that reduced to the common
factor 3-86.
SOLUTION WEIGHT AND SOLUTION FACTORS.
In the analysis of the carbohydrates it is necessary in most
instances to know the amount of solid matter present in solution.
This may be estimated by evaporating a known bulk to dryness
and weighing the residue. Such method, however, is by no
means satisfactory, since it becomes essential, in order to remove
the last traces of moisture, to continue heating for a considerable
time, and by thus heating, the organic substance is to an extent
decomposed. On this account it was found preferable to ascertain
the amount of matter in solution by taking the specific gravity
and dividing the excess weight over water (1000) by a factor.
The original factor employed was 3 '85, which was devised by
O'Sullivan in 1876, 2 who based it on the assumption that 10
grams of pure maltose or pure dextrin, when dissolved in so much
water that the solution measures exactly 100 c.c. at a temperature
of 60 F. (15-5 C.), the specific gravity of the solution (10 per
cent.) is 1038 '5, water being taken as 1000.
l Jnl. Chem. Soc., Jan. 1897, 86.
2 Ibid., 1876, 129.
58 THE BREWER'S ANALYST
Assuming that the strength of such solutions was strictly
proportional to their specific gravity, a 1 per cent, solution would
have a specific gravity of 1003*85, and solutions containing inter-
mediate quantities would have gravities expressed by intermediate
values. Consequently, if each per cent, of either of these bodies
raised the specific gravity of a solution by 3'85, it would be a
simple matter to ascertain the amount present in solution ; it
would, in fact, be only necessary to subtract 1000 from the
specific gravity of the solution and divide the figure so obtained
by 3-85.
Thus 100 c.c. of a solution of maltose of a specific gravity of
1055 would contain
1055- 1000 =14 . 285 grams of that su bstance.
O'OO
Later on Brown and Heron 1 came to the conclusion that 3'85
was too low for maltose, the correct divisor being 3 '9 3 14, and
O'Sullivan afterwards gave the fresh divisor 3 '95 for starch
conversion products. It was afterwards found that with solutions
of the various carbohydrates the specific gravity of the solution
was not strictly proportional to the amount of the substance
contained in solution, and Brown and Heron 2 proposed the use
of 3 '86 in all cases as a solution divisor ; but this is only correct
for a 10 per cent, solution of cane-sugar, which has a specific
gravity of 1038*6 at 60 F. (15'5 C.).
Brown, Morris, and Millar 3 have made fresh determinations "of
the solution weights of a number of the sugars, and of various
starch transformation products ; the last traces of moisture being
removed from the substances dealt with by a process devised by
Lobry de Bruyn and Van Leent. It consists in placing the sugar
or other body in a small flask, which is placed in a water or oil
bath, and connected with another small flask containing anhydrous
phosphoric acid, a vacuum being maintained in the apparatus
during the drying process. From the results thus obtained, the
solution factor was determined for various concentrations. They
were found, as in the case of cane-sugar, not to be directly pro-
portional to the percentages present in solution, but might be
expressed in the form of a series of curves. These are given in
a table, and by consulting this the proper solution factor for any
concentration of any of the sugars given can be found by inspection.
The solution factors for solutions of several of the sugars and
starch transformation products at a density of 1055 and at a
1 Jnl. Chem. Soc. t 1897, 618. 2 Ibid., 02. 3 Ibid., 72.
r>F THE
DIVERSITY
r 'F
THE POLARIMETER 59
temperature of 60 F. (15'5 C.) are shown, Plate 1. fig. 52, but
the original paper referred to should be consulted where extreme
accuracy is essential.
Brown, Morris, and Millar point out, in defence of their having
used the 3 '86 factor for starch conversion products, that, so far
as ascertaining the percentage of the constituents is concerned,
the factor employed is a matter of indifference, provided the
specific rotatory powers and cupric reducing values of the con-
stituents corresponding with those of the particular divisor taken
are used in the calculation. They can be readily calculated into
the true amounts as soon as the true factor for the particular
starch conversion is known. At the same time, attention is
called to the fact that this is only strictly correct when the
solutions are of approximately the same density, and the con-
stituents possess identically the same divisor; but they do not
consider that the error thus introduced is sufficiently large to
vitiate their former work, or the conclusions based on it.
When the curves of the divisors for the different grades of
starch conversions are examined, it is found that for equal
concentrations the divisor for high conversions is greater than
that for low, in fact there appears to be some inverse ratio
between it and the amount of apparent maltose present.
It was found that if the mixed products of starch conversions
were assumed to consist of dextrin and maltose, and that the
maltose, which, according to the amyloin theory, exists in com-
bination with dextrin, was assumed to have the same solution
density as free maltose, it became possible to obtain by calculation
the divisor for the amyloin or dextrin constituent. This was done
for various conversions, and the curve thus found is given in the
table.
Though, as stated, it is somewhat improbable that the solution
factor for combined and free maltose would be the same, yet it
was found that when this dextrin curve was used in conjunction
with the maltose curve it was possible to determine, within
certain limits of concentration, and with a fair amount of
accuracy, the solution divisor for the mixed products of any
starch conversion brought about by diastase, the apparent maltose
percentage being either obtained from the opticity or cupric
reducing power of the solution.
We thus understand that where carbohydrate bodies have to
be examined for cupric reducing power, their amount is most
frequently deduced from the specific gravity of their solutions
by means of a solution factor. Consequently, it is usual to affix
60 THE BREWER'S ANALYST
in small characters the solution factor which has been used in
any particular case, such as K 3 . 8(3 or K 3 . 85 . This means that the
amount of solid matter in the first instance was estimated by the
3 '86 factor, in the second by the 3 '85.
The absolute reducing power may be readily obtained from
the statement of these on the 3 '8 6 factor when the true solution
factor is known. Thus the reducing power of maltose is K 3 . 86 =
61. If, as O'Sullivan assumed, the true solution factor for maltose
is 3 '93 14, then its real reducing power is
3-86: 3-9314:: 61: 62-12.
CUPRIC OXIDE REDUCING POWER.
It is shown in subsequent pages that several of the carbo-
hydrates reduce Fehling's solution, or, in other words, precipitate
different amounts of the copper contained in that standard
solution. According to the amount of copper precipitated, so is
the power of the carbohydrate in solution. The cupric oxide
reducing power is based upon the specific cupric reducing power
of a substance referred to dextrose as a standard of 100, and
such a figure is indicated by the letter K. Thus K = 50 signifies
a solution having half the reducing power of dextrose. As the
amount of reducing carbohydrate is almost invariably determined
by means of a solution factor previously referred to, it is con-
venient to add the divisor which has been used: thus K 3 . 86 = 50
explains that the reducing power is expressed on solid matter
determined by the factor 3*86.
Brown, Morris, and Millar propose to refer the reducing power
of carbohydrates to maltose taken as 100, and for indicating this
they use the letter R; thus RS-SS^ 50 indicates that the substance
has a reducing power of half that possessed by maltose, when the
amount of the substance is determined by means of the factor
3-86.
The cupric oxide precipitated by the various carbohydrates,
under favourable conditions, is as follows :
1 gram CuO = *7435 maltose.
'4535 dextrose.
'4715 invert-sugar.
Ptciiley's Brewer's Analyst.']
[PLATE I.
Solution Factors for Carbo-hydrates at Various Densities.
Specific Gravity at 15' C. (From Brown, Morris and
Millar, Journal of the Chemical Society, 1897, vol. Ixxi.,
p. 72.)
FIG. 52.
[To face p. 60.
PAKT III.
CARBOHYDRATES AND ALLIED SUBSTANCES.
PROTE1DS OR ALBUMINOIDS AND ENZYMES.
CARBOHYDRATES AND ALLIED SUBSTANCES.
THE name carbohydrate, embracing a very large number of
organic bodies, was originally applied to compounds which contain
in the molecule six atoms of carbon, or a multiple of this number,
together with hydrogen and oxygen present in the proportion in
which these elements unite to form water. This water, expressed
by the formula OH 2 , contains two atoms of hydrogen and one atom
of oxygen to form the molecule. In cane-sugar, expressed by the
formula C 12 H 22 O n , it will be seen that the same ratio between
the hydrogen and oxygen atoms exists, viz. 2:1. In inorganic
compounds the term " hydrate " is applied to those substances
which actually contain hydrogen and oxygen combined as water :
thus calcic hydrate Ca(OH) 2 when gently heated gives off the
combined water Ca(OH) 2 = CaO + OH 2 . Hence it was that the
carbohydrates were designated as hydrates of carbon. The term
carbohydrate, however, applied to the group of compounds about
to be considered, is in this sense a misnomer, since the elements
of hydrogen and oxygen are not contained within the molecule of
these compounds in the same sense as would be understood in the
case of an inorganic substance. The term was deduced from a
consideration of the empirical formulae of these bodies before their
constitution was as well understood as at the present time.
Recent researches, especially those by Emil Fischer, have shown
that the carbohydrates possess an exceedingly complicated
molecular structure, and that the group term carbohydrate
includes a very large number of substances which may be sub-
divided into groups having relationships and properties analogous
61
62 THE BREWER'S ANALYST
to, and not greatly differing from, the elementary group of the
hydrocarbon derivatives.
Most of the carbohydrate compounds occur in the vegetable
organism, but some few are also found in the animal kingdom.
The larger number are well known as constituting articles of food,
and it is needless to say that the majority are of the highest
physiological importance. They consist of several isomeric
groups, 1 most of whose members when in solution exhibit active
optical properties deviating the plane of polarised light either to
the right ( + ) or to the left ( - ), and are therefore said to be
optically active.
The more important carbohydrates which have an importance
from the brewing point of view are, according to their empirical
composition, divided into the following groups :
A. THE PENTOSE GROUP (C 5 H 10 5 ).
(a) Aribinose.
(b) Galaetoxylan.
(c) Xylose, Amylan, and Furfural.
B. THE CELLULOSE GROUP (C 6 H 10 5 ) n .
(a) Celluloses including the Hemicelluloses
and Oxycelluloses.
The molecular weight and constitution of most of the members
of this group are unknown, or have only been ascertained with
approximate accuracy.
(b) Starch. Amylo-cdlulose.
Granulose.
Soluble Starch.
(c) Dextrms. Amylo-dextrins.
Ery thro-dextrins.
A chroo-dextrin*.
(d) Inulin.
C. THE HEXOSE GROUP C 6 H 12 6 .
(a) Dextrose, (d-glucose) \
(b) Galactose V Aldose.
(c) Mannose }
(d) Levulose Ketose.
bodies or isomePS are bodies of identical empirical com-
position, but vary in properties. Thus starch, dextrin, cellulose, etc. have all
the same percentages of carbon, hydrogen, and oxygen, though different in
many other respects.
CARBOHYDRATES AND ALLIED SUBSTANCES 63
D. THE DrsACCHARiDB GROUP (C 12 H 22 O n ).
(a) Cane Sugar or Saccharose.
(b) Maltose or Malt Sugar.
(c) Lactose or Milk Sugar.
E. THE POLYSACCHARIDBS.
(a) Malto-Dextrins. (C 12 H 22 O n ) n .
(C 12 H 20 10 ) n .
(b) Rafflnose. C 18 H 32 16 .
We need only discuss the characteristics of the more important
of these bodies, thus :
A. THE PENTOSE GROUP (C 5 H 10 O 5 ).
Aribonose. Galactoxylan. Xylose. Amy Ian and Furfural.
The pentoses and their derivatives are found as constituents of
the husk and gummy matters of barley and malt. The pentoses
yield furfural when hydrolysed * by acids, and to this compound
is due the objectionable smell which always accompanies any
attempt to the further conversion of " spent " grains by means of
acid. Furfural is also formed to a slight extent at the mashing
stage, the acidity of the mash inverting galactoxylan and then
xylose into this compound.
B. THE CELLULOSE GROUP (C 6 H 10 5 ) n .
Hemicelluloses.
Oxy celluloses.
Starch. Amylo-cellulose, Granulose, Soluble Starch.
Dextrins. Amylo-dextrins, Erythro-dextrins, Achroo-dextrins.
Inulin.
CELLULOSE, HEMICELLULOSE, OXYCELLULOSE (C 6 H 10 5 ) n .
The Celluloses constitute the fundamental material of the
structure of all plants from the highest tree to the lowest fungus.
They are built up from soluble carbohydrates contained in
1 Hydrolysis. The term was suggested by Dr Armstrong. It is the
term used where the assimilation of the elements of water by a molecule of any
substance is immediately followed by its splitting up into other compounds.
Decompositions, like that of starch into dextrose, of cane-sugar into
dextrose and levulose, of the fats into glycerine and an acid, or of ordinary
ether into ethylic alcohol, which involve the fixation of the elements of water,
may all be said to be the result of hydrolysis.
64 THE BREWER'S ANALYST
protoplasm, and, with the exception of the very young cellular
tissue, always contain mineral matter. Cellulose is therefore very
seldom found pure, inasmuch as other substances pass from the
cells into the membrane, and there become fixed. If we micro-
scopically examine a thin section of wood or a little pith of the
elder, we see that the mass is made up of a great number of
irregularly shaped cells, and these are composed of cellulose.
Whilst the wood or other vegetable growth is still young the
substance of the cells is almost pure, but as the structure gets
older the cells become encrusted with resinous and other
secretions, and frequently assume a yellow, brown, or red tint.
The sources of cellulose are practically endless, and the forms in
which it appears are very numerous. Cotton is almost pure
cellulose, so also is elder pith, whilst w&jjfld it in very hard form
in the date stone and in vegetable ivory. ^^arley contains about
7 per cent, of it, cotton 91 '35 per cent., straw 46*22 per cent.,
and in different kinds of wood the percentage varies from 30 to
63. The purest forms of cellulose are cotton- wool, frequently
washed linen, and unglazed paper. If either of* these substances
be washed, first with weak alkali, and, after every trace of the
alkali has been removed, by distilled water, then submitted to the
action of weak hydrochloric acid, and finally again washed with
distilled water, we obtain cellulose iincontaminated by foreign
substances. As such, it is insoluble in the ordinary solvents such
as water, alcohol, ether, etc., or by prolonged boiling with dilute
acids or alkalies, but it dissolves in an ammoniacal solution of
cupric oxide, or in a strong solution of zinc chloride and hydro-
chloric acid.
Cellulose is a white, tasteless, odourless, innutritious substance,
which readily takes up moisture, but is unacted on by it, and
unaffected by exposure to air. It is coloured brown by iodine
solution, and is about one and a half times as heavy as water.
A mixture of strong nitric and sulphuric acids converts cellulose
into nitro-cellulose or gun-cotton, C 6 HK(N0 2 ) 3 O 5 , a substitution
which is reversed by alcoholic solution of potassic hydrosulphide,
reproducing cellulose. Besides ordinary forms of cellulose, which
in general resist the action of acids, alkalies, and enzymes, there
are certain celluloses which undergo hydrolysis with comparative
facility. Instances of these are the hemi-celluloses, which in the
seeds of some plants constitute the reserve material stored by the
parent plant for the sustenance of a future plant whilst in
embryo. Such reserve material takes the place of the starch
stored in the endosperm of the barleycorn. This cellulose is
CARBOHYDRATES AND ALLIED SUBSTANCES 65
readily hydrolysed by acids, and is converted into soluble
saccharine matters by the agency of enzymes secreted by the
growing plant. As examples, mention may be made of the cellu-
lose forming the walls of the starch containing cells of the
endosperm of barley, the dissolution of which takes place during
germination by the enzyme cytase, and the amylo-cellulose of
ordinary starch granules which is slowly hydrolysed by diastase
in the cold, but with facility at a temperature of 140 F. (60 C.).
Cross and Be van have shown that there are still further modi-
fications of cellulose present in many vegetable tissues, such as
those of the barley plant; and these, since they contain larger
percentages of oxygen than ordinary cellulose, have been named
" oxy-celluloses." They are extremely resistant to the action of
dilute alkalies, and, like the pentose sugars, the oxy-celluloses,
when distilled with hydrochloric acid, yield furfural ; and upon
hydrolysis with dilute acids (1 per cent, sulphuric) are partially
converted into a fermentable sugar, having probably the following
constitution,
XX
3 H 8 C 5 < >H 2 .
It was whilst studying this class of bodies that the author con-
ceived and patented the idea of treating "spent" grains for the
extraction of sugar. 1
The process consisted in converting "spent" grains in a similar
fashion to that in which raw grain is sometimes converted.
" Spent" grains contain from 2 to 10 per cent, of starch ; and it
was not only to recover this residual starch, but also to act upon
the cellulose and convert it also into sugar, that constituted the
idea. The sugar obtained was found to be of the furfuroid
character, and amenable, to an extent, to the fermentative action
of yeast. The results of the author's experiments in conjunction
with those of Cross and Bevan have long been recorded; 2 suffice
it to say that no commercial progress was made, after lengthy
experiments and heavy expenditure.
+ STARCH (C 6 H 10 5 ) n .
Amylo- Cellulose. Oranulose. Soluble Starch.
The formula for starch is as shown above, the value of n not
being known. Brown and Morris, as is shown hereafter when
1 Bailey and Ford Patent, No. 1788, 1896.
2 Jnl. Fed. Inst. Breivincj, 1897, 75.
66 THE BREWER'S ANALYST
considering the malto-dextrins, are of opinion that the formula
for starch cannot be less than 5(C 12 H 20 10 ) 20 , but it is yet doubtful
whether this formula will not at some future date be altered. At
any rate we may look upon starch as a carbohydrate containing
C, H, and O in the proportions in which these elements unite to
form water, and await developments for more light upon the
actual multiple of these elements.
Starch is a substance found in the form of small granules in
the cells of grain, legumes, and potatoes. It exists in nearly all
plants with the exception of the fungi. It is, in fact, the most
abundant material to be found in the vegetable world. It is
originally formed in the cells of the leaves of plants from the
carbon dioxide of the atmosphere, by the agency of chlorophyll
(the green colouring matter of leaves) in the presence of sunlight.
The starch thus formed may be looked upon as migratory, since
by enzymic action it is transformed into soluble sugars, passing
into the sap of the plant, and thence carried throughout the
plant, building up its fabric, reappearing at different stages of
the plant growth as cellulose, gummy matter, lignin, or trans-
formed again into starch as the reserve material in the seeds of
cereals, the tubers of the potato, etc. The study of the meta-
morphoses of starch in the living plant, from the assimilation of
carbon dioxide in the green leaves to the formation of starch in
the barleycorn, is an interesting study, and yields much valuable
information upon the process of germination. The classical
researches of Brown and Morris upon the " Physiology of Foliage
Leaves " l and the " Germination of the Gramineae," 2 should
therefore be consulted.
Starch is generally obtained in Europe from wheat, maize,
potatoes, and rice, and in tropical countries from the stems of
the palm and from the tubers of various plants; thus, in the
East Indies and the Philippine Islands, starch is obtained from
the pith of the sago-palm (Sagus loevis or Sagus rlium.pMi). This
comes into the market under the name of sago (a word meaning
bread). Arrowroot is the starch of the Maranta arundinacea and
indica, and a few other tropical plants growing in the West Indies,
Brazil, and the Southern States of America. Tapioca is derived
from Yatropha manihot, this, like sago, being subjected to pressure
to give the grains a peculiar form.
1 "A Contribution to the Chemistry and Physiology of Foliage Leaves"
(Jnl. Chem. Soc. Trans., 1893, 604-677).
2 " Researches on the Germination of some of the Gramineae " (Jnl. Chem.
Soc. Trans., 1890, 458-528).
CARBOHYDRATES AND ALLIED SUBSTANCES 67
Starch being heavier than water, its density at a temperature
of 67-5 F. (19-7 C.) being 1-505, has the property, when mixed
with it, of sinking with proportionate rapidity, and we may observe
that the bottom layer is "remarkable for great toughness. It is
never found in a state of purity, but always occurs mixed with a
greater or less amount of nitrogenous matter. In order to purify
it, until within recent years the starch was mixed with water
and allowed to stand until fermentation set in, this being caused
by the action of aerial ferments, the result being that the formation
of acetic, butyric, and lactic acids in time split up the nitrogenous
matter, and a subsequent washing with water left the starch pure.
There are two objections to this method of preparing starch :
firstly, the lengthy time necessarily occupied ; and secondly, the
objectionable odour evolved from the fermentation, which renders
the manufacture a nuisance to the neighbourhood. It became
necessary, therefore, to adopt fresh means for purifying it, and this
is now performed by dissolving the nitrogenous bodies with caustic
soda instead of the previous objectionable method of fermentation.
The steep water is first made faintly acid by the addition of a
little sulphuric acid, and the starch is afterwards treated with
water containing y-g^th of its weight of caustic soda, or a solution
containing 200 grains or J ounce of the alkali per gallon.
The external characteristics of starch granules can only be
distinguished by the aid of the microscope on account of their
minute size ; and by the aid of this instrument it was discovered
that not only does the size of the granules vary in every species of
starch, but that each species exhibits its own particular form and
structural markings. Adulteration can thus be detected, and
admixture of cheap potato starch with the more expensive
wheaten starch may be approximately measured by microscopical
observation.
Though the cells of every species of starch vary in size and
shape, they nevertheless exhibit certain similarities in structure.
Each has a dark point, central in some, eccentric in others, known
as the "hilum." Round this are seen a series of concentric lines,
an appearance caused by the peculiar structure of the granules,
which are built up of layers containing varying amounts of water.
The hilum is always rich in water, and each layer alternately
contains more or less water, the outside layer being always most
free from moisture and richest in substance. As a consequence
of the proportion of water increasing from the outside of
the granule inwards to the hilum, fissures radiating from the
hilum towards the periphery often arise as the granule becomes
68 THE BREWER'S ANALYST
dry. By steeping starch granules in alcohol, which entirely
deprives them of water, all appearance of stratification disappears,
but the lines reappear if the granules are moistened with water.
If they are treated with dilute alkali or acid, the appearance of
stratification is rendered much more distinct.
The following sketches, figs. 53 to 64, Plates II. to VII., show the
microscopical appearance of the more important starches ; and the
table, by Gait, 1 gives their outline, measurement, surface, hilum,
and markings.
Air-dried starch contains from 15 to 20 per cent, of moisture,
the last traces of which it retains with remarkable pertinacity,
consequently it is almost impossible to remove the whole of the
moisture by heat alone without at the same time causing a
chemical alteration in the starch substance itself. To avoid this,
Dafert 2 proposes to remove the hygroscopic water by drying the
starch in vacua at 212 F. (100" C.). Absolutely dry starch
attracts moisture with such avidity that when moistened with
water a perceptible rise of temperature takes place, a phenomenon
which shows that the last portions of water are in a state of
chemical combination.
Starch is an exceedingly inert substance, insoluble in cold
water, alcohol, ether, and ammonia cuprate, the latter showing
its difference from cellulose ; but it dissolves in potassic hydrate
solution, in consequence of the formation of a potassium derivative.
On treating with acetic anhydride it is converted into a tri-
acetate, C 6 H 7 2 (C 2 H 3 2 ) S .
It may be heated, when dry, to a temperature of 300 F. (148*8
C.) without change, but by a temperature of from 300 to 400 F.
(148 '8 to 204'4 C.) it is converted into a substance soluble in
cold water, termed dextrin or British gum, and at temperatures
above this it is decomposed.
Starch is largely used in the arts for laundry purposes, paper
sizing, bookbinding, weaving and finishing calicoes, also for pre-
paring the thickening for colours and mordants in calico printing,
for dusting the formes in metal founding, and a variety of other
purposes.
So long ago as 1716 Leuwenhoek asserted that the cell -walls of
the granules differ from the cell contents ; and Raspail confirmed
this assertion, believing, however, that the cell contents were
identical with gum arabic. On the other hand, Guibort came to
the conclusion that both the above possessed the same chemical
1 TJie Microscopy of the Starches.
2 Jnl. f. prakt. Chem., Ixxiii. 51.
Bailey's Brewer's Analyst.]
[PLATE U.
FIG. 53. Potato Starch, x 116.
(Galt-Bailliere, Tindall, and Cox.)
FIG. 54. Rye Starch, x 116.
(Galt-Bailliere, Tindall, and Cox.)
[To face p 68.
Bailey s Brewer's Analyst.']
[PLATE III.
FIG. 55. Rice Starch, x 300.
(Macmillan.)
FIG. 56. Oat Starch, x 380.
(Galt-Bailliere, Tindall, and Cox.
[To face p. 68.
Bailey's Brewer's Analyst. '
[PLATE IV.
FIG. 57. Maize Starch, x 300.
(Macmillan.)
FIG. 58. Pea Starch, x 116.
(Galt-Bailliere, Tindall, and Cox.)
[To face p. 68.
Bailey's Brewer's Analyst. ]
[PLATE V.
FIG. 59. Tapioca Starch. xl!6.
(Galt-Bailliere, Tindall, and Cox.)
FIG. 60. Sago Starch, x 116.
(Galt-Bailliere, Tindall, and Cox.)
[To face p. 68.
Bailey's Brewer's Analyst,.
FIG. 61. Barley Starch, x 116.
(Galt-Bailliere, Tindall, and Cox.)
[PLATE VI.
FIG. 62. Wheat Starch, x 116.
(Galt-Bailliere, Tindall, and Cox.)
[To face p. 68.
Bailey's Brewer's Analyst.'
[PLATE VII.
FIG. 63. Tons les Mois Starch. x 116.
(Galt-Bailliere, Tindall, and Cox.)
FIG. 64. Bermuda Arrowroot Starch. x 116.
(Galt-Bailliere, Tindall, and Cox.)
[ To face p.
CARBOHYDRATES AND ALLIED SUBSTANCES
69
TABLE SHOWING THE LEADING MICROSCOPICAL CHARACTERS OF THE
MORE IMPORTANT STARCHES.
Fi
Outline.
Measuremen
Surface.
Hilum.
Markings.
60
Potato.
Oval or ellip
tical.
mm.
Js In long dia
" meter ;
J 7 in short
diameter.
Uniformly
but slightly
convex.
Dark spot nea
narrow end.
Concentric rings ;
closed, or almos
closed, curves.
61
Rye.
Circular.
A
Convex,
spherical.
Crucial o
radial, cen
tral, large.
Exceedingly faint
complete concen-
tric rings.
62
Rice.
Rectilinear
and poly-
gonal.
*i
Flat.
None.
None.
63
Oat.
Rectilinear
and poly-
gonal.
0(7
Flat or slight
ly convex 01
concave.
None.
None.
64
Maize.
Rectilinear
and poly-
gonal.
1
Uneven, anc
slightly
concave.
Stellate or ir
regular, large
central.
None.
65
Pea.
Ren if or m.
2 V in long dia-
meter ;
& in short
diameter.
Convex, with
central lon-
gitudinal
depression.
Large, si it-like
longitudinal,
central. '
Appearance of
concentric rings
forming closed
curves.
66
Sago.
Rounded ;
some partly
angular.
vfa in long
diameter ;
n in short
diameter.
Uniformly
and highly
convex.
Near large and
rounded end,
large, slit-like
or irregular,
transverse.
Occasionally a few
very faint, gener-
ally incomplete,
concentric rings.
67
Tapioca.
Rounded ;
some partly
angular.
^
Uniformly
convex.
Slit-like, trans-
verse, stel-
late, central.
Like sago, but still
more indistinct.
68
Wheat.
Circular, or
nearly so.
*
Convex.
Dark spot, ec-
centric.
Occasionally a few
exceedingly faint
concentric rings.
69
Barley.
Circular,
lenticular.
^00
Convex.
Dark spot, ec-
centric, sel-
dom apparent.
Very rarely, faint
indication of con-
centric rings.
70
Jermuda
arrow-
root.
Oval.
V in long dia-
meter;
3*5 in short
diameter.
Uniformly
but slightly
convex.
yfear broad
end, circular,
crucial, trans-
verse line or
slit.
Taint concentric
rings, in a few
cases extending
about two-thirds
of length of grain.
71
'ous'les-
Mois.
Irregularly
oval or
elliptical.
Jjy in long
diameter ;
T&J in short
diameter.
Uniformly
but very
slightly
convex.
Dark spot near
narrow end.
oncentric rings
extending for less
than one -third of
length of grain.
70 THE BREWER'S ANALYST
composition, and that they only differed physically. 1 The
structure of the starch granule was then carefully examined by
Fritsche, 2 and the classical researches of Naegeli 3 proved that
starch is a mixture of several isomeric compounds. Its internal
portion consists of what is termed yranulose with a small portion
of starch cellulose, whilst the outer coating consists principally,
if not entirely, of this latter substance. The outer coating or
cellulose of the starch granule protects the inner content or
granulose from being acted upon either by cold water or diastase,
and before any action can therefore take place it becomes necessary
to burst the granules either by attrition or heat.
There is great divergence of opinion as to whether or not the
granulose upon being set free from the granule enters into a state
of solution. Some say that it does not, since if it did so it would
readily pass through cell membrane, which property it does not
possess. Brown and Heron believe that the granulose is in a true
state of solution, and that the viscosity of starch paste is due to
the swollen state of the cellulose. They found the viscosity to
vary considerably. The more slowly the starch has been dried
and the lower the heat at which this has been effected, the more
viscous the solution ; in fact they found the difference in viscosity,
due to the varied methods of preparation, to amount to more than
three to one. Moritz and Morris express the opinion that on
boiling starch the granulose is converted into soluble starch.
In any case, when starch is heated with water the granules-
undergo a singular change in their structural condition. They
take up large quantities of water, become swollen, and in time,
if the temperature of the water is high enough, burst. A
gelatinous mass is formed which is designated as starch paste,
the process itself being termed the production of starch paste, or
the gelatinisation of starch.
During the heating the volume of the liquid becomes greater.
According to Pay en, the increase of volume amounts to 142 per
cent, at a temperature of 140 F. (60 C.), and to 1255 per cent,
at 158-161-6 F. (70-72 C.). The higher the temperature
of the water, the greater the swelling of the granules, and also
the greater the diffusion. The temperature at which starch
granules begin to swell, and also that at which a complete
transformation into paste occurs, differs according to the nature
of the starch.
Soluble Starch is conveniently prepared, according to
1 Jnl. Cliem. Med., v. 9. 2 Pogg. Ann., xxii. 129.
3 Jahresber. d. C/iemie, 1859, 544.
CARBOHYDRATES AND ALLIED SUBSTANCES 71
Lintner, 1 by digesting potato starch with a 7 '5 per cent, solution
of ordinary strong hydrochloric acid at a temperature of 60 F.
(15*5 C.) for one week, afterwards washing the starch by repeated
decantation until the washings are perfectly free from acid; or,
according to Brown and Morris, 2 a 12 per cent, solution of hydro-
chloric acid may be employed, in which case digestion for twenty-
four hours suffices. The starch granules undergo no apparent
physical change by the process, as is shown by microscopical
examination, in which case it will be seen that the granules retain
their original appearance.
Soluble starch is precipitated by a large addition of alcohol,
also by many metallic oxides, as lime, baryta, and lead oxide. It
is coloured an intense deep blue by iodine solution, this property
having been discovered by Gaultier de Clanbry in 1814. The
reaction, however, is much influenced by temperature ; the
lower the temperature the more sensitive is the reaction. At or
near the boiling-point of water the coloration does not appear at
all, but a deep blue makes its appearance as the solution cools,
provided the solution is not subjected to prolonged heating.
The blue colour does not show itself so readily, nor is it so
pure, in the presence of other bodies such as tannin, malt extract,
beer, yeast, etc. Whether the blue substance formed is a true
chemical compound or not has not been definitely settled.
The colour also varies according to the nature of the starch ;
thus potato starch gives a deep blue, wheat-starch a colour
inclined to violet. This is accounted for by a larger amount of
the cellulose, which is coloured brown by iodine, being contained
in some of the starches.
Two starches have been met with by Dafert and Kreusler, 3 the
one in a species of rice, the other in a kind of millet, which are
coloured from red to brown by iodine solution. The opticity of
soluble starch is given as [a]j 3 ' 86 + 216 by Brown and Morris, and
as [a] D + 200 by Lintner. Brown, Morris, and Miller state that
the opticity in 2*5 to 4*5 per cent, solution is at 60 F. (15'5 C.)
[a] D 202. It has no reducing action on Fehling's solution.
When acted on by diastase in the cold it is decomposed in ten
minutes to the No. 8 equation. When, however, the action of
diastase is allowed to proceed for ten or twelve days in the cold,
soluble starch is entirely converted into maltose. 4
1 Jnl. f. praM. Chem. , xxxiv. 378.
2 Jnl. Chem. Soc., 1889, 450.
3 Landwirth. Jahrbuch, xiii. 767, xiv. 831.
4 Lintuer, Jnl. /. prakt. Chem., 1887.
72 THE BREWER'S ANALYST
By the action of diastase or acid on soluble starch, under
suitable conditions, identical sugars are formed, and the inference
naturally arises that the intermediate products (malto-dextrins),
formed by the respective agents, are identical.
The transformation of soluble starch to dextrins and malto-
dextrins can be followed to a certain extent by the iodine reaction,
the deep blue tint produced in soluble starch changing to red
upon the starch hydrolysing to dextrin.
Brown and Morris, 1 by employing Raoult's method, found the
molecular weight of soluble starch to vary from 20,000 to 30,000 ;
and on the asumption that the stable dextrin of the No. 8
equation constitutes one-fifth of the molecule, they concluded that
its molecular weight is 32,400, and its formula 5(C ]2 H 20 10 ) 5 , .
The question the brewer has to take into consideration is how
best and most economically he can transform starch into dextrin,
maltose, and malto-dextrin, in proportions suitable for any
particular beer. No matter whether he employs the starch of a
cereal such as rice or maize, he obtains the same fermentable
products as those produced by the employment of oats or barley.
Certain starches, however, produce somewhat objectionable
flavoured worts, and such worts are prone to quickly acidify ;
hence it is that only certain raw grain starches are employed by
the brewer.
+ DEXTRIN (C 6 H 10 5 ) n .
Amylo-dextrins. Erythro-dextrins. Acliroo-dextrins,
By heating dry starch to a temperature of from 300-400 F.
(14S'S-204*4* C.), as already mentioned, a substance, soluble
in cold water, termed dextrin or British gum, is produced.
Dextrin forms an intermediate stage in the conversion of starch,
whether effected by mineral acids or malt-extract (diastase).
There are three kinds of dextrin, designated amylo, erythro,
and achroo, the amylo- and erythro-dextrins giving a red or
brownish colour with iodine solution, the achroo-dextrins
being unaffected by this reagent. There has been great con-
troversy as to the existence of different types of dextrin, Greiss-
mayer, O'Sullivan, Nsegeli, and other investigators describing
several.
The dextrins are neutral, tasteless substances, soluble in
water, dilute alcohol or naphtha, but insoluble in absolute
alcohol or ether.
1 Jnl. Chem. Soc. t 1889, 465.
CARBOHYDRATES AND ALLIED SUBSTANCES 73
C. THE HEXOSE GROUP C 6 H 12 6 .
+ Dextrose (d-glucose). Galaciose. Mannose.
Levulose (fructose).
+ DEXTROSE (d-glucose} C 6 H 12 6 .
Dextrose or d-glucose is one of the sugars found in great
abundance in the vegetable kindom. Ripe sweet fruits, such as
grapes, plums, figs, etc., contain, in addition to levulose and
small quantities of cane-sugar, large quantities of this substance.
It is also met with in the stems and seeds of cereals and in the
flowers of many plants from which bees derive honey ; it is also
found in honey.
Compounds of dextrose are frequently met with, termed
glucosides, which readily split up under the hydrolysing action of
dilute acids or enzymes into dextrose and their other constituents.
Dextrose is now largely prepared from starch and starchy
materials by the action of dilute mineral acids, the product thus
obtained consisting of a mixture of dextrin, maltose, and dextrose,
the percentages of these sugars depending upon the conditions
and length of time the hydrolysis is allowed to proceed. But if
the hydrolysis is prolonged to its fullest limit, the dextrin first
formed is converted to maltose and the latter to dextrose. In
such cases other substances besides dextrose are formed, amongst
which is supposed to be a substance termed gallisin. Of their
character, little of a satisfactory nature is known.
Dextrose is only half as sweet as cane-sugar ; it is readily soluble
in water and dilute alcohol, but is completely insoluble in absolute
alcohol. It is not charred or blackened by concentrated sulphuric
acid, as is cane-sugar, but if heated with solutions of the alkalies
a brown coloration is produced, and with dilute acids prolonged
heating forms brown substances termed ulmin and ulmic acid.
On heating dextrose to temperatures between 230-309F.
(110-154 C.) caramel is produced. On heating to 340F.
(171 C.) water is given off and glucosan is formed; whilst on
still further heating, the substance is decomposed.
Dextrose readily combines with oxygen, and hence is able to
reduce the oxides of several metals to the metallic form ; whilst
in the case of some metals such as copper, the higher oxide is
reduced to the lower, viz., CuO to Cu 2 O. On this property the
methods of determining dextrose quantitatively are founded.
Dilute nitric acid oxidises dextrose to saccharic acid (C 6 H 10 8 ).
Solutions of dextrose are readily fermented by yeast, maltose
74 THE BREWER'S ANALYST
requiring to be first hydrolysed to dextrose by the enzyme
maltose contained in yeast, and cane-sugar to be first hydrolysed
to invert by the enzyme invertase contained in yeast, before
fermentation commences and splits the sugar up into alcohol and
carbon-dioxide. Upon fermenting, dextrose yields 48*67 per cent,
of alcohol. It possesses an optical activity of [a] D3 . 86 = 51'7, and
its cupric-oxide reducing power is K 3 . 86 = 100.
Dextrose solutions, like those of levulose and maltose, produce
an osazone when treated with phenyl-hydrazine.
If 1 gram of dextrose is dissolved in 50 c.c. of water, and 2 grams
of phenyl-hydrazine dissolved in 2 grams of 50 per cent, acetic
acid are added, the mixture upon being treated throws down a
dense yellow precipitate. The action is complete in one hour.
The precipitate, microscopically examined, will be found to consist
of needle-shaped crystals, some of which may occur in fan-shaped
aggregates. The precipitate, when collected, washed with hot
water, and dried at 212 F. (100 C.), will be found to be very in-
soluble in boiling water, which characteristic assists in its
identification.
The reaction of phenyl - hydrazine with the hexoses is as
follows : If one molecule of phenyl-hydrazine is allowed to act
on one molecule of a hexose, a normal hydrazone is formed :
Dextrose. Phenyl-hydrazine. Hydrazone.
CH 2 .OH(CH.OH) 4 . CHO + C 6 H 5 NHNH 2 = CH 2 .OH(CH.OH) 4 .
CH + H 2
II
N-NH.C 6 H 5 -
But if two molecules of phenyl-hydrazine are used, an osazone
is obtained :
CH 2 .OH(CH.OH) 3 .C - CH = N - NH.C 6 H 5
II
N
NH.C 6 H 5 .
Glucosazone.
Dextrose solutions, like those of some other carbohydrates,
also possess the phenomenon of muta-rotation. A freshly-prepared
solution shows an opticity nearly twice as great as that given
after standing, and the opticity only becomes stationary after a
lapse of about 24 hours. Two minutes boiling or the addition
of a very small quantity of caustic potash or ammonia (O'l per
cent.), however, at once fixes the rotatory power. Besides by the
hydrolysis of starch, dextrose may be prepared from cane-sugar,
CARBOHYDRATES AND ALLIED SUBSTANCES 75
in which case the product consists of nearly equal weights of
dextrose and levulose, otherwise known as invert-sugar. The solid
portion of commercial samples of invert consist of crystallised
dextrose, which may be washed with alcohol, dissolved, and
recrystallised from methyl-alcohol. The dextrose then separates
as hydrate (C 6 H 12 O 6 + H 2 0).
- LEVULOSE (Fructose) C 6 H 12 O 6 .
Levulose exists in association with dextrose in grapes, ripe
fruits, honey, and in the stems and seeds of cereals; and is
present in invert-sugar to the extent of nearly half the latter's
weight. It may be separated from invert by making a solution,
mixing an equal weight of finely-powdered slaked lime, and
maintaining for some time at a low temperature. The lime forms
a solid compound with the levulose known as insoluble calcic
levulosate, while the dextrose forms a compound which is freely
soluble, and may be separated by nitration and washing. The
residue is then mixed with water, and on passing a current of
carbon-dioxide through the liquid, decomposition occurs, the
lime being precipitated as carbonate, and the levulose passing
into solution. This solution may be rendered anhydrous by
evaporation in vacuo over sulphuric acid. Thus prepared,
levulose is a colourless, uncrystallisable syrup, distinctly sweeter
than dextrose, and more soluble than the latter in alcohol. By
careful recrystallisation, it may be obtained in fine silky crystals,
which melt at a temperature of 203 F. (95 C.).
Levulose turns a polarised ray of light strongly to the left,
hence its name, the angle of rotation being [] D 3-sG = - 93'7,
and it has a cupric-oxide reducing power of K 3 . 8(j = 92'4.
The polarisation is thus more powerful than that of dextrose
to the right, so that a solution of invert-sugar, containing equal
quantities of each sugar, possesses a distinct levo-rotatory power.
The levo-rotatory angle diminishes as the temperature of the
solution rises, so that at a certain temperature levulose apparently
possesses no rotatory power at all, since the action of the negative
levulose is then exactly balanced by the positive rotation of the
dextrose, and at about this temperature invert-sugar becomes
dextro-rotatory.
Levulose ferments in contact with yeast, but not so readily as
does dextrose, a fact which favours the theory that the sluggish-
ness of its fermentation is due to it not being able to diffuse so
readily as dextrose through the walls of the yeast cells.
76 THE BREWER'S ANALYST
When levulose is heated strongly it is converted into levulosan
(C C H 10 5 ), a body isomeric with glucosan and produced in the
same way from dextrose by the expulsion of water. It comports
itself in many respects in an almost similar manner to dextrose,
and is oxidised into saccharic acid by contact with dilute nitric
acid.
Solutions of levulose form an osazone when treated with phenyl-
hydrazine.
D. THE DISACCHARIDE GROUP C 12 H 22 O n .
Cane-sugar or Saccharose. Maltose or Malt-sugar.
Lactose or Milk-swjar.
+ CANE-SUGAR C 12 H 22 lr
Cane-sugar is freely soluble in water, a cold, saturated solution
at 60 F. (15-5 C.) contains about 66'3 per cent., a boiling
solution about 82-5 per cent. The gravity of a solution increases
in a slightly greater ratio than the percentage of sugar, and the
difference in ratio becomes still more pronounced as the quantity
is further increased.
Cane-sugar is insoluble in ether, slightly soluble in absolute
alcohol, and more so in dilute alcohol, the solubility increasing
with the dilution of the alcohol. It has no reducing action on
Fehling's solution, melts at a temperature of 320 F. (160 C.).,
and on cooling solidifies to an amorphous mass, which, after some
time, becomes crystalline.
When heated for some time to 338 F. (170 C.) it is split up
into dextrose and levulose, but if exposed to a higher temperature,
356-392* F. (1SO-200 C.), the mass becomes first yellow and
then brown, forming caramel. Heated to a still higher tempera-
ture, decomposition takes place with evolution of combustible
gases and acid vapours, a light porous mass of carbon being left
behind.
If a little concentrated sulphuric acid be added to cane-sugar
syrup, an immediate and characteristic action ensues ; the sugar
is deprived, by the acid, of the elements of water, and its carbon
separates as a solid swollen black mass, of much greater bulk
than the syrup from which it is derived. If, however, a solution
containing not more than 30 per cent, of cane-sugar is heated
with dilute acid, the sugar, instead of parting with, takes up
the elements of water and is hydrolysed into a mixture of dextrose
and levulose, otherwise known as invert-sugar. The same change
CARBOHYDRATES AND ALLIED SUBSTANCES 77
is brought about when cane-sugar solution is placed, under
suitable conditions, in contact with yeast, invertase, the enzyme
of monilia Candida, or malt extract. In the latter cases, how-
ever, the action is very slow. The reaction which results is the
same whichever agent be employed ; it consists in the assimilation
of water by the cane-sugar molecule, followed by its separation
into the two different kinds of sugar named, which, though of
very different properties, have the same formula.
The following equation expresses the change : -
C 12 H 22 O n + H 2 = C 6 H 12 6 4 C 6 H ]2 6 .
Cane-sugar. Water. Dextrose. Levulose.
Invert-sugar.
Yeast ferments cane-sugar solutions of weak or medium strength,
but is unable to ferment solutions of 50 to 60 per cent, strength,
or any solutions to which large quantities of glycerine have been
added : the enzyme zymase, however, ferments these solutions
readily.
Cane-sugar forms compounds (saccharates) with several bases,
such as potassium, strontium, lead, etc., all of which are de-
composed by carbon-dioxide.
It does not form a compound with phenyl-hydrazine, but when
heated in a solution of the acetate of that base, it first suffers
inversion into dextrose and levulose, these latter sugars uniting
with the phenyl-hydrazine to form glucosazone. Cane-sugar
solutions of medium dilution and under suitable conditions are
completely fermentable by yeast, but in such instances the
fermentation is not a direct one, the sugar being first split up
into invert.
Many bacteria are able to induce peculiar fermentations in
solutions of cane-sugar, in which such bodies as lactic acid,
butyric acid, mannitol, etc., are produced.
+ MALTOSE C 12 H 22 O n .
Although belonging to the same group as cane-sugar, maltose
has few properties in common with that most familiar substance.
It nowhere in nature exists ready formed to any great extent. It
is surmised that plants, during their growth, transform a portion
of their starch into maltose as and when they require the latter
for food, but the amount required is so infinitesimal that no large
quantity is found to exist therein.
78 THE BREWER'S ANALYST
Maltose was discovered by De Saussure in 1819, but the
discovery was overlooked or forgotten. It was again discovered
by Dubrunfant 1 in 1847, but again overlooked or forgotten. In
1872, however, C. O'Sullivan 2 rediscovered it.
O'Sullivan prepared it by acting upon gelatinised potato starch,
with diastase at about 90 F. (32'2 C.). Chloroform was added
to prevent bacterial growths, and the infusion allowed to stand for
ten days. The solution was then evaporated to a syrupy
consistency, when maltose slowly crystallised out which was
purified by. being dissolved in alcohol and recrystallised. It
separates from an aqueous solution in needle form, and contains
one equivalent of water of crystallisation ; but when separated
from alcoholic solution it is anhydrous. It is a white substance,
soluble in water, but sparingly soluble in alcohol. It reduces
Fehling's solution in a degree equal to about two-thirds of its
weight of dextrose. This reduction is stated by O'Sullivan to be
equal to 65 per cent, of its weight of dextrose, but Brown and
Morris state the percentage to be equal to K 3 . 86 = 61, which, how-
ever, is practically the same thing, when allowance is made for the
fact that O'Sullivan employed the factor 3 "85 in place of the
now commonly used factor 3 '86.
According to Soxhlet, with an excess of undiluted Fehling's
solution and an approximately 1 per cent, solution of maltose, 100
parts of maltose invariably yield 127 '3 parts of cupric oxide, or
113 parts of copper. A series of tables for the estimation of
maltose have been prepared by Kjeldahl. 3
The optical activity of maltose is [a] D3 . 8fi = 135'9. It is
converted into dextrose when heated for a short time with
dilute mineral acid, the best temperature for the hydrolysis being
176 F. (80 C.) to 194 F. (90 C.). Malt extract or diastase is
unable to effect any change in it, whilst in contact with yeast,
under suitable conditions, it is hydrolysed to dextrose under
the influence of a special enzyme contained within the yeast
termed maltase or glucase, and is further decomposed with the
production of from 51 to 52 per cent, of alcohol. When in
company with dextrose the latter is fermented first.
A hot solution of maltose, heated with phenyl-hydrazine, forms
osazone which separates on cooling as yellow needles, and which
melt and decompose at a temperature of 390 F. (198*8 C.).
1 Ann. Chim. et Phys., xi. 379.
2 Jnl. Chem. Soc. Trans., xxv. 579.
3 Med. Carlsb. Lab., 1895, 1.
CARBOHYDRATES AND ALLIED SUBSTANCES 79
E. THE POLYSACGHARIDES.
+ Malto-dextrins (C 12 H 22 O n ) B .
( C 12 H 20lo)"-
Raffihose C 18 H 32 O 16 .
+ Malto-dextrins (C 12 H 22 O n ) n .
( C i2 H 2oio)-
The transformation products in a starch conversion possessing
an [] D 150'3 consist of :
Maltose . . . 80'8 per cent.
Dextrin . . 19'2
KHM)
The optical activity of a starch transformation effected by
unrestricted diastase falls rapidly from [a] D 202, representing the
original soluble starch, to [a] D 150'3 representing a so-called
complete conversion, and when it reaches this stage the velocity
of the transformation change is checked; [a] D 150'3 therefore
represents a well-defined point in the hydrolysis of starch. An
equation representing this change, commonly called the " No. 8 "
equation, is given thus :
[5(C 12 H 20 10 )] + 4H 2 - 4C I2 H 22 O n + (C 12 H 20 10
Starch. Water. Maltose. Stable dextrin.
This equation represents that four-fifths of the starch molecule
is converted into maltose and one-fifth into stable dextrin ; but
the amount of maltose in the starch transformation products is
not four-fifths the weight of these products, owing to the fixation
of water during hydrolysis, hence the proportion 80 '8 maltose to
19*2 dextrin in the products of a complete conversion.
The starch molecule is, however, much larger than [5(C 12 H 20
o w )].
Brown and Millar 1 bring forward evidence to show that the
molecule of stable dextrin is [20(C 12 H 20 10 )], and therefore that
the molecule of soluble starch must be at least five times as large.
According to this view, the conversion of soluble starch into
maltose and dextrin is represented as follows :
(C 12 H 20 10 ) 20 + 80H 2 - 80C 12 H 22 O n + [20(C 12 H 20 10 )]
(C 12 H 20 ]0 ) 20 Maltose. Stable dextrin.
(^12-^-20^10)20
Soluble starch.
1 Jnl. Chem. Soc., 1899, Jxxv. 317.
80 THE BREWER'S ANALYST
The so-called " stable " dextrin, although it strongly resists the
action of diastase, is eventually hydrolysed to maltose and
dextrose if the action of the diastase is very prolonged ; but
the velocity of the action is exceedingly slow as compared with
the velocity of hydrolysis of starch to maltose and dextrin.
RAFFINOSE C 1S H 32 16 .
Raffinose was discovered by O'Sullivan as a constituent, to a
small extent, in barley ; its common origin, however, is the sugar-
beet. The formula is C 1S H 32 16 + 50H 2 , and it crystallises in small
needles or prisms which readily dissolve in water but are only
slightly soluble in alcohol and possess but a faint sweetness.
It does not reduce Fehling's solution, its rotatory power being
[a] D3 . 86 = 104-5.
When heated for a short time with dilute mineral acid, it
splits up into equal molecules of levulose and of a disacharide
isomeric with lactose, called "melibose." This latter substance,
on prolonged treatment with dilute acid, splits up into galactose
and glucose in equal molecules. 1
On fermentation, raffinose behaves differently with various
yeasts; some are able to hydrolyse and ferment it completely,
others only partially invert it into melibose and levulose, the latter
sugar being alone fermented.
It is not known whether raffinose has any important influence
upon worts or beers.
a and (3 AMYLAN.
These bodies were found by O'Sullivan in barley, wheat and
rye. Barley contains about 2 per cent, of a-amylan and about
0'3 per cent, of ft-amylan.
They were obtained from barley by extracting the cereal first
with alcohol and then with water. The aqueous solution was
concentrated by evaporation, and strong alcohol added, which
precipitated the two bodies. The precipitates were treated with
cold water, which dissolved out the fi-amylan and left the a-amylan.
The latter was afterwards dissolved in dilute hydrochloric acid,
and precipitated therefrom by alcohol.
Both these bodies are levo-rotatory, and have the following
opticities :
a-amylan . . [a] j = - 24
/3-amylan . . . []j= -73
Hydrolysis by dilute acids converts them into glucose.
1 Berichte, xxii., 1678 and 3118.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 81
GUM.
Lintrier separated a small amount of gum from beer, and a
similar, if not identical, substance was afterwards found in barley,
malt, straw, bran, and "spent" grains. The gum forms very
viscous solutions which are very difficult to filter. The gum is
dextro-rotatory, does not reduce Fehling's solution, and is pre-
cipitated by lead acetate. Like many other gums, it gives a
cherry-red colour with phloroglucin and hydrochloric acid, also a
bluish-green colour with orcein and hydrochloric acid, its
presence in beer being demonstrated by these reactions.
Lintner and Diill l have shown that the gum may be regarded
as galactoxylan ; for when boiled with dilute acid it is resolved
into galactose and xylose. It is evidently formed by the union of
a molecule of galactose with a molecule of the penta glucose sugar,
xylose, with the elimination of a molecule of water, thus :
C 6 H 12 6 + C 5 H 10 5 - H 2 = C n H 20 10 .
Galactose. Xylose. Water. Galactoxylan.
PROTEIDS OR ALBUMINOIDS AND ENZYMES.
Serum, Fibrin, Egg, Casein, and Plant Albumins Molecular
Constitution of the Proteids Effects of Hydrolysis on the
Proteids Chemical Reactions of the Proteids Members of
the Proteid Groups The Proteids of Barley The Proteids
of Malt Enzymes or Hydrolysis Chemical Composition
of the Enzymes Enzyme Groups Action of Proteoiijtic
Enzymes on the Proteids.
DIASTASE, GLUCASE OR MALTASE, CYTASE, INVERTASE, ZYMASE.
The proteids or albuminoids, otherwise spoken of as protenaceous,
nitrogenous, or albuminous bodies, form the chief part of the solid
constituents of the blood, muscles, nerves, glands, and other
organs of animals. They occur in small quantities in almost every
part of vegetables, and in large quantities in the seeds, and in
fact enter so largely into the composition of organic substances
that they have been regarded as building up the animal and
vegetable worlds. They are of great importance to man's
existence ; both plants and animals lay up reserves or stores of
them in various parts of their tissues for contingent use, so that
should their food supplies be suddenly withdrawn, neither the
plant nor animal would immediately die, but would live for a time
1 Zeit.f. angew. Chem., 1897, 538.
82 THE BREWER'S ANALYST
on its reserves. Before these reserves, however, can be made
available for the operations of nutrition, they must first be
converted from their inert and mostly insoluble state into a state
of solution and adaptability to circulate in the nutritive fluid
which constitutes the alimentary atmosphere or environment of
the protoplasmic elements. We shall hereafter more readily
perceive how these operations are performed, so for the present
may merely look to the characteristics of a few specially studied
proteid bodies.
ALBUMIN.
Of the various forms of albumin we have serum albumin, fibrin
albumin, egg albumin, and plant albumin or gluten.
Serum albumin is the most abundant albuminous substance
in animal bodies. It may be obtained tolerably pure, from blood-
serum by precipitation with lead acetate, washing with water,
suspending the precipitated lead compound in water, and decom-
posing it with carbon-dioxide ; then, by nitration, a very cloudy
solution of albumin is obtained. The albumin may now be pre-
cipitated from this solution by the addition of alcohol which in
time coagulates it. It is not precipitated by weak mineral acids
in small quantity; but large quantities of acid precipitate it
immediately, nitric acid acting most strongly. It forms a yellow,
elastic, transparent substance which, when perfectly dry, can be
heated to 100 F. (37'7 C.) without change. The substance to
which the clotting of blood is due is termed fibrin. It is insoluble
in water, sparingly soluble in dilute acids and alkalies and in
neutral saline solutions. It may be obtained by washing blood-
clots, or more readily by stirring with a bundle of twigs blood
just shed, before it has had time to clot. The fibrin, which
adheres in layers to the twigs, may then be stripped off and
washed till perfectly white.
Egg* albumin or white of egg differs from serum albumin by
gradually giving a precipitate when agitated with ether, whilst oil
of turpentine coagulates it. A characteristic between serum and
egg albumin is that the former is easily dissolved by nitric acid
whereas the latter is only dissolved with difficulty therein. The
so-called vitellin contained in solution in the yolk of egg is a
mixture of albumin and casein. If a drop of egg albumin is
allowed to fall into a saturated solution of resorcinol, the drop of
albumin, at first transparent, becomes gradually opaque, and
finally white like a hailstone. It gradually falls through the
liquid, lengthens itself out to a band, becomes broader and
PROTEIDS OR ALBUMINOIDS AND ENZYMES 83
broader, and finally reaches the bottom. It has the appearance of a
bacteriological culture. If the liquid is now shaken it falls to the
finest powder, and is so disseminated in the froth that it appears
to have dissolved. The s'ame effects are produced however dilute
the egg albumin may be.
Casein OP legumin, sometimes termed alkali-albumin, or
albuminate, according to whether the substance is derived from
animal or vegetable sources.
An example of casein is the flocculent substance which separates
when milk becomes acid, whilst legumin occurs in peas, beans, etc.
Casein occurs most plentifully in the milk of animal feeders,
and is best obtained from milk by precipitating with crystalline
magnesium sulphate, filtering and washing with concentrated
solution of sodium chloride, and dissolving the precipitate in
water; the butter is then filtered off, and the clear solution
precipitated by dilute acetic acid. Dried casein and albuminate
are yellow, transparent, and hygroscopic ; they swell in water but
do not dissolve. They dissolve easily in alkaline water when
placed in it in a flocculent state. The precipitate which forms,
on neutralising the alkaline solution, dissolves easily in an excess
of acetic or hydrochloric acid.
By fusion with potassium hydrate, casein yields valeric and
butyric acids, besides other products.
Plant albumin or gluten is a substance analogous to the
fibrin previously described ; it occurs as an insoluble substance in
plants, especially in the seeds of cereals and grasses.
When wheat flour is lixiviated with water, a tough, coherent,
elastic mass is left behind, which can be pulled out into strings.
This is the gluten, or the body which gives the coherent character
to the dough, and the presence of which confers the property of
enabling it to yield a light, porous bread. Gluten cannot be
obtained in this way from the meal of any other grain. It is
insoluble in water, becomes dark by exposure to the air ; whilst
dried at a low temperature, it assumes a yellowish-brown colour
and becomes horny, and when treated with strong alcohol it
assumes an earth-like appearance. It may be dissolved by
hydrochloric acid and dilute alkalies, and is precipitated from
these solutions by mineral salts and acetic acid.
MOLECULAR CONSTITUTION OF THE PROTEIDS.
All proteids contain the elements carbon, hydrogen, nitrogen,
and oxygen, whilst occasionally they contain sulphur and phos-
84 THE BREWER'S ANALYST
phorus. Our knowledge of their composition is, however, very
imperfect, and at present it is assumed that their molecule is
extremely complex.
Stohmann and Langbein assert that the formula of crystallised
proteid is C 720 H 113 N 218 S 5 248 , equivalent to a molecular weight
of 16,954, whilst Sabanejeff obtained a molecular weight of 15,000
by Raoult's cryoscopic method. This method, however, is admitted
to be inapplicable to the accurate determination of the molecular
weights of colloid bodies, hence the figures cannot be accepted as
of definite value, but merely as a confirmation of the high
molecular weight of these bodies. Many investigators have
obtained compounds of proteids with inorganic salts; thus a
copper salt obtained approximates to the formula
whilst with magnesium and other salts the formula
has been indicated.
EFFECTS OF HYDROLYSIS ON THE PROTEIDS.
By the action of certain hydrolysing agents such as superheated
steam, dilute mineral acids, caustic alkalies or enzymes, the latter
of which are dealt with hereafter, the large proteid molecule is
split up into much smaller and less complex molecules. From a
study of these we have obtained some general knowledge as to.
the nature of the molecular groups which enter into the composi-
tion of the proteids. When the proteids are acted upon by
enzymes, the splitting-up process does not extend nearly so far,
the molecules of the bodies produced being much nearer in size
to that of the original proteid molecule.
Of such a nature are the proteoses and peptones.
The nature of the hydrolysis may be conveniently stated as
follows :
Proteid Albumin.
Proteoses.
Peptones.
I
Amides.
All the amides are of a crystalline nature and eminently diffus-
ible in plants ; and it is extremely probable that the amides in
the living plant form a portion of the materials from which the
PROTEIDS OR ALBUMINOIDS AND ENZYMES 85
proteids are constructed, the amides themselves being probably
produced by a combination of the deoxidation products of the
chlorophyll cells with nitrogen, derived from the nitrates and
ammonia contained in tire fluid contents of the cells. Whether
this conjecture is right or wrong, we know that numerous amide
bodies and also various products resulting from their hydrolysis
exist in plants. We are also aware that by the action of acids,
alkalies, or steam, proteids or albumins may be decomposed to
proteoses and amides, and that the latter bodies are further
hydrolysed. Thus by the action of boiling hydrochloric acid to
which a little stannous chloride is added, amides produce, more
or less, the following substances :
Leucine.
Tyrosine.
Aspartic acid.
Glutamic acid.
Glutaminic acid.
Lysine.
Arginine.
Histidine.
Lysatine.
When barium hydroxide is used as the hydrolysing agent, in
addition to the formation of the above-mentioned products, much
ammonia and carbon-dioxide are evolved ; and these gases are
given off in the proportion of one molecule of water and one of
VTTT
urea, CO** 2 + OH 2 = C0 2 + 2NH 3 .
Taking the principal amide substances, we have the following:
Leucine or ctmido-caproic add.
CH 3 , /NH 2
C 6 H 13 N0 2 = >CH-CH 2 -CH<
CH 3 / \COOH.
This amide is usually the normal product in every energetic
decomposition of proteid matter ; it is obtainable in considerable
amount by the hydrolysis of horn by acids, and by the action of
trypsin upon most proteids. It is found in germinating seeds
and is present in germinated barley and in malt worts. In a
state of purity it consists of brilliant, silvery- white plates,
which melt at 338 F. (170 C.). It is soluble in water, arid
its aqueous solutions are dextro-rotatory. It is only slightly
soluble in alcohol. It has been prepared synthetically. When
86 THE BREWER'S ANALYST
treated with nitrous acid it yields up the whole of its nitrogen
thus : ^
C 6 H 8 N0 2 + HN0 2 = C 6 H ]2 O 3 + OH 2 + 2N
Leucine. Nitrous Hydroxy- Water. Nitrogen.
acid. caproic acid.
Tyrosine or paraliydroxy-phenylamido-propionic acid
/OH /NH
C 9 H n N0 3 = C 6 H/ CH<
\CH 2 \COOH
is also produced in the decomposition of all proteids, with the
exception of gelatine, and has frequently been detected in
germinated seeds. When pure, it crystallises in brilliant silky
needles which are not readily soluble in water, and insoluble in
alcohol. An aqueous solution is Isevo-rotatory, but a dextro-
rotatory modification is known.
It is found in the liver and other organs, and among the
excretory products of yeast, and frequently accompanies the
decomposition of proteids by the putrefactive action of bacteria.
Treated with nitrous acid, it yields up nearly the whole of its
nitrogen.
Asparaglne or amido-succinamide.
/ CH \
C 4 H 8 N 2 3 = COOH< >CH 2 -CON H 2 .
So called because it was first found in asparagus sprouts. This
substance, although probably not resulting from the breaking
down of proteids by proteohydrolysts, is of great importance,
since it is found in considerable amount in many plants and
germinating seeds. It has not yet been isolated from malt, but
occurs in considerable quantity in the rootlets. It is supposed
that the formation of this compound in living plants is, in reality,
a result of synthesis rather than decomposition ; that is to say,
as previously mentioned, it makes an early stage in the building
up of the complex albuminoids rather than a final stage in the
retrograde decomposition by proteolysis.
Although the existence of asparagine in malt and wort is
uncertain, there is little doubt that its presence would be of
considerable benefit. The extraordinary stimulating effect of this
substance upon the activity of diastase has been investigated by
Effront and Fernback, and its high value as yeast nutriment has
been fully demonstrated by Stern.
In a state of purity it forms large colourless crystals, soluble in
PKOTEIDS OR ALBUMINOIDS AND ENZYMES 87
water, but insoluble in alcohol. Its aqueous solutions are laevo-
rotatory, its specific rotatory power being [o] D =-6 % 23. A
dextro-rotatory asparagine which rotates the same angle in the
opposite direction has, however, been found in tares. The dextro-
rotatory body has a distinctly sweet taste; the laevo-rotatory is
almost tasteless. When heated with dilute acids, asparagine is
readily transformed into aspartic acid and ammonia, thus :
C 4 H 8 N 2 8 + OH 2 = C 4 H 7 N0 4 + NH 3 .
Asparagine. Water. Aspartic acid. Ammonia.
When acted on by nitrous acid, it yields half of its nitrogen in
the gaseous state as follows :
C 4 H 8 N 2 8 + NH0 2 - C 4 Hg0 5 + NHg + 2JS T .
Asparagine. Nitrous Malic Ammonia. Nitrogen,
acid. acid.
A method for the estimation of asparagine and the amides
generally has been based on this reaction by Sachasse. 1 Aspara-
gine is precipitated by mercuric nitrate, and the compound so
obtained may be decomposed into asparagine and mercuric
sulphide by the action of hydrogen sulphide.
AspartlC acid or amido-sucdnic add.
C 4 H 7 N0 4 = CH/
pw \COOH
UH 2 ,
\COOH.
This is the crystalline body previously referred to ; it is slightly
soluble in water, rotates the polarised ray to the left or right,
according as the asparagine from which it is obtained is laevo- or
dextro-rotatory. Treated with nitrous acid, it yields up the whole
of its nitrogen thus :
C 4 H 7 N0 4 + HN0 2 = C 4 H 6 B + OH 2 + 2N.
Aspartic Nitrous Malic Water. Nitrogen,
acid. acid. acid.
Among other amide compounds resulting from the decomposi-
tion of the proteids, the following may be enumerated, which have
a more or less important bearing upon the subject :
Glutamic acid or amido-gluiaric add.
/\
4 = CH 2 < \COOH
\CH 2 -COO
Agricult. Chem., 390.
88 THE BREWER'S ANALYST
Glutaminie acid.
^5H 10 N 2 O a ^ A j. 2 v x
\CH<
CH 2 -CONH 2
K 2
COOH.
And the hexone bases :
Lysine or diamido-caproic acid.
C 6 H 14 N 2 2 = CH 2 NH 2 -CH 2 -CH 2 -CH 2 -CH/
\COOH
a dextro-rotatory substance from hydrolysis of casein.
Arginine or diamido-valeric acid.
/NH 2X ,NH 2
C 6 H 14 N 4 2 = NH = C< >CH 9 -CH 2 -CH -CH<
\NH / X COOH.
Histidine. C 6 H 9 N 3 2 .
Lysatine. C 6 H 18 N S 2 .
In addition to the above compounds, glycocoll (amido-acetic acid)
CH 2 <^ sometimes results from proteolytic decomposition,
\COOH
and has been detected in many plants.
Besides the important amide products, resulting from the
decomposition of the proteids by hydrolysis, either by acids or
enzymes, there are numerous bodies which result from the
breaking down of albuminoid substances by the aid of living
organisms ; these are frequently excretory products such as :
Xanthine . . . C 5 H 4 N 4 2 .
Sarcine . . . C 5 H 4 N 4 0.
Guanine . . . C 5 H 3 N 5 0.
The above and other xanthine bases are found among the
excretory products of yeast and micro-organisms of other
description. In addition to these or similar substances, besides
the normal products of proteohydrolysis, many pathogenic
organisms form either products of a phylacteric nature, such as
protective serums, or of a poisonous nature, such as the toxins,
which, together with the ptomaine* formed by certain kinds of
putrefactive bacteria, partake of the nature of alkaloids.
CHEMICAL REACTIONS OF THE PROTEIDS.
The proteids give the following characteristic reactions, which
may readily be observed with a solution of egg albumin, made by
PROTEIDS OR ALBUMINOIDS AND ENZYMES 89
mixing a small quantity of white of egg, which contains about 12
per cent, of albumin, with water, and filtering.
Precipitation by Nitric Acid. When strong nitric acid is added
to an aqueous solution of any of the proteids, a white precipitate
forms, which turns yellow on heating the liquid. The addition of
ammonia to the mixture, after it has become cold, causes the
yellow precipitate to become orange-coloured.
Biuret Reaction. On adding a few drops of a dilute solution of
cupric sulphate to an aqueous solution of a proteid, and after-
wards a few drops of a strong solution of caustic soda, a colour is
developed which varies with the different classes of proteid. The
proteids give a violet colour ; the proteoses, a reddish-violet ; the
peptones, a rose-red.
Millon's reagent l yields a white precipitate which becomes
reddish on boiling the fluid.
Evolution of Ammonia. The proteids when strongly heated
evolve ammonia, produced under the destructive action of heat.
The ammonia may be recognised hy its changing the colour of a
piece of moist red litmus paper to blue. A smell resembling that
of burnt hair is also given off during the heating.
Formation of Cyanides. The proteoses, when heated with
metallic sodium, yield sodium cyanide. The presence of this
compound can be detected by extracting the mass with water,
adding a few drops of a solution of ferrous sulphate containing a
little ferric sulphate, and digesting for a short time. On the
addition of hydrochloric acid a blue or bluish-green colour is
produced if proteids are present.
MEMBEES OF THE PROTEID GROUPS.
By means of the solvent power of various saline solutions it
has been found possible to isolate the proteids from the sub-
stances with which they are associated, and to effect a fairly
complete separation of the various members of the proteid
groups from one another by reason of the further property
possessed by certain salts of throwing out of solution certain
members of the groups when the solution is saturated with the
particular salt.
This latter process is known as "salting out," and by the
1 Millon's Reagent. Prepared by gently warming mercury with an
equal quantity of strong nitric acid till it dissolves, then diluting the liquid
with twice its bulk of water, and leaving the precipitate to settle. The clear
supernatant liquid is the reagent.
90 THE BREWER'S ANALYST
employment of this method the various plant proteids have been
divided into the following groups :
Albumins. Soluble in water, coagulated by heat.
Gliadin and Hordein. Slightly soluble in water, readily soluble
in 70 per cent, alcohol.
Glutenin. Slightly soluble in hot water and hot alcohol,
soluble in O'l per cent, solution of caustic potash and in 0'2 per
cent, hydrochloric acid ; insoluble in saline solutions.
Gloubulins- Vitellins. Insoluble in water, soluble in dilute
saline solutions, coagulated in great part by heat.
Gloubulins- Myosi7is. Insoluble in water, soluble in dilute
saline solutions, precipitated by sodium chloride, coagulated by
heat.
All these bodies, excepting the latter (gloubulins), are obtained
in an amorphous condition, in which state they probably exist in
plants. Many of the gloubulins have been obtained in a crystalloid
form, and to some extent exist in this condition in seeds.
THE PROTEIDS OF BARLEY.
Ritthausen l succeeded by fractionation with alcohol in
differentiating three proteid bodies from wheat-flour, viz., gluten-
fibrin, gliadin, and mucedin, and a fourth, gluten-casein, which
was insoluble in alcohol but soluble in dilute alkali. He con-
sidered that these four bodies constituted the gluten of wheat,
and that it was the gliadin which formed the binding material.
This body was found to be absent in the flour of those grains
which left no gluten behind on washing.
Ritthausen also considers that these are the bodies belonging
to the gluten group in barley, viz., gluten-fibrin, gluten-casein,
and mucedin.
Osborne 2 finds that there are only two : hordein, which is
apparently identical with Ritthausen's mucedin, but which has
almost the same physical and chemical properties as the gliadin
obtained from wheat, though it differs from it in composition ; the
second being the insoluble proteid which it was found impossible
to isolate.
Mulder 3 found a barley to contain 6 per cent, of albumin and
plant gluten ; he obtained the latter by extracting the ground
barley with hot alcohol.
Von Bibra 4 considers that the proteids of barley are albumin,
1 Die EiweissJcdrper. a Jnl. Amer. Chem. Soc., xv. 392.
3 Ann. Chim. et Phys. , 306. 4 Die Getreidearten, 204.
PROTEIDS OK ALBUMINOIDS AND ENZYMES
91
plant gluten, and casein, but gives no particulars concerning
these substances.
Kreusler found that an aqueous extract of ground barley con-
tained an albumin which '"coagulated on boiling, and that hot
75 per cent, alcohol dissolved a substance which could be sub-
sequently separated into three proteids gluten-casein, gluten-
fibrin, and mucedin, which were supposed to be identical with
the bodies having the same names, which Ritthausen had isolated
from wheat.
According to Osborne, 1 to whom we are indebted for an
elaborate and extensive series of investigations on the proteids of
various grains and seeds, barley contains the following proteid
bodies :
Per cent.
Leucosin (albumin) . . 0*30
Proteose ) , .g^
)
Edestin (globulin)
Hordein
Insoluble proteid .
Total
4-00
4-50
10-75
whilst the average percentage composition of a large number of
analyses gave the following :
Carbon.
Hydrogen. Nitrogen.
Sulphur.
Oxygen.
Leucosin .
Edestin .
Hordein .
52-81
50-88
54-29
6-78 16-62
6-65 18-10
6-80 17-21
1-47
2232
^/
24-37
0-83
20-87
Insoluble proteid
Unknown.
THE PROTEIDS OF MALT.
During the process of malting, the proteids of barley undergo
considerable modification, a large portion which are insoluble in
water becoming soluble as the barley germinates. This arises
chiefly from the breaking down of the proteids into proteoses.
The proteids of malt have been investigated by Osborne and
1 Report of the Connecticut Agricultural Experimental Station, 1892.
92 THE BREWER'S ANALYST
Campbell, 1 who, by employing similar processes to those which
they adopted in their investigations on the proteids of barley,
obtained the following bodies :
Bynedestin. A globulin, soluble in dilute solutions, and
therefore passing into the aqueous extract of malt. It appears
to replace the original edestiu of the barley, from which it differs
in composition, since bynedestin contains about 2 per cent, more
carbon and 3 per cent, less nitrogen. Its percentage composi-
tion is
Carbon .... 53-19
Hydrogen .... 6"69
Nitrogen .... 15*68
Sulphur . . . .1-25
Oxygen . . . .23-19
Leucosin. Identical in composition and properties with the
albumin of the same name contained in barley.
Protoproteose 1. Has the same composition as leucosin,
from which it is impossible to effect a complete separation. The
proteose is precipitated from its aqueous solution by adding an
equal weight of alcohol.
Protoproteose 2. Less readily precipitable than No. 1, by
alcohol, its percentage composition being
Carbon .... 5O63
Hydrogen . . . 6 -67
Nitrogen .... 16"69
Oxygen and sulphur . . 20*01
DeutCPOproteOSe. A body inseparable from non-proteid
impurities.
HetePOproteOSe. A substance found in extremely small
amount.
Bynin. A body insoluble in water or saline solutions, but
readily soluble in dilute alcohol, its percentage composition
being
Carbon . . . .55-03
Hydrogen . . . 6 -67
Nitrogen . . . . 16 '26
Sulphur .... 0-84
Oxygen . . 21 '20
Insoluble Proteid. This, which amounts to about 3 '80 per
cent, of the total proteid matters, is insoluble in water, saline
1 Report of the Connecticut Agricultural Experimental Station, 1896, 239.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 93
solutions, or alcohol ; and consequently it is impossible to study
its composition or determine its properties. A sample of malt
which contained altogether 7 '84 per cent, of proteid matters,
yielded the following quantities of these substances, as far as they
could be separated :
Per cent.
Proteids, insoluble in salt solution or alcohol . 3'80
Bynin, soluble in dilute alcohol . . . .1*25
Bynedestin, leucosin, and proteoses (coagulable) . 1 -50
Bynedestin, soluble in water and salt solution
(uncoagulable) . . . . . . 1'29
Total proteids . . . 7 '84
These results show that during germination the proteids of
barley undergo extensive changes before acquiring the properties
of proteoses ; that hordein disappears, and an alcohol-soluble body
of entirely different composition takes its place ; that edestin
also disappears, and a new globulin is formed very different both
in composition and properties.
The albumin, on the other hand, appears to be unchanged in
character, but its quantity is increased. It is to be noted that
hordein and edestin are both replaced by proteids much richer
in carbon and poorer in nitrogen.
ENZYMES OR HYDROLYSTS.
Enzymes or hydrolysts exist in all living organisms whether
of animal or vegetable origin, and are remarkable nitrogenous
bodies either actually albuminoids or very closely allied to them.
There are numerous varieties, each having its special correlative
alimentary principle or group of principles, on which, under
certain conditions (an absolutely necessary one being the presence
of water), it is capable of acting. Diastase, for instance, acts on
amylaceous substances and cane-sugar ; whilst pepsin and trypsin
act only on the azotised principles. The emulsive ferment of the
pancreas is only capable of acting on fatty bodies, and the
inversive ferment of yeast and of the small intestine has no
activity except on cane-sugar.
These nitrogenous bodies are often spoken of as the " unorganised
ferments " or " enzymes," * and the transformations they effect
1 The word "enzyms" was first proposed by Ktihne. Roberts afterwards
adopted the word into English with a slight change of orthography, terming
it "enzymes."
94 THE BREWER'S ANALYST
" fermentative processes." In 1 890, however, Armstrong suggested
more scientifically correct terms, viz., as in the changes brought
about by these bodies water is almost invariably assimilated or
added to the molecule of one or both of the newly formed
substances, the process is one of, and should be designated,
" hydrolysis," and the agents concerned in the action " hydrolysts."
Thus by combining with the word " hydrolyst," the name of the
substance on which each particular enzyme acts, we obtain a
distinctive name for each class. Thus the enzymes which act
upon starch are now called amylo-hydrolysts ; those that act on
proteids, proteo-hydrolysts, etc.
CHEMICAL COMPOSITION OF THE ENZYMES.
It is doubtful whether any of the preparations of .the enzymes
obtained by different investigators have been of a sufficient degree
of purity to permit of accurate determination of their chemical
composition.
Lintner, working with the diastase of malt, obtained a solution
possessing a high diastatic power having the following com-
position :
Carbon . . . .46*66
Hydrogen . . . 7 '35
Nitrogen . . . 10 '41
Oxygen . . 34*46
Sulphur .... 1-12
A substance having this composition differs from albumin, to
which the enzyme bodies are generally closely allied, albumin
on analysis giving the following percentage composition :
Carbon .... 53*02
Hydrogen . .6*84
Nitrogen . . . 16*80
Oxygen . . 22*06
Sulphur . . . .1*28
At first sight one would be disposed to consider diastase as
a substance differing in a marked degree from albumin. Osborne,
however, who has made a very close study of the albuminoid
constituents of cereals, isolated a diastase having a much higher
diastatic power than Lintners preparation, its diastatic power
being equivalent to 600 upon Lintner's scale.
The composition of this body, which is undoubtedly one of
PROTEIDS OR ALBUMINOIDS AND ENZYMES
95
the purest preparations of the enzymes which has been obtained,
is as follows :
Carbon
Hydrogen
Nitrogen
Oxygen
Sulphur
52-50
6-72
16-10
22-78
1-90
a- body of this percentage composition closely agreeing with the
analysis of albumin already given.
Osborne further found that this diastatic preparation had a
very close resemblance to leucosin, an albumin which he had
previously isolated from barley, wheat, rye, and malt.
Other preparations of diastase and enzyme substances have
been made by different investigators, the chief of which are in-
cluded in the following table by Enron t, " Les enzymes " :
Carbon.
Hydrogen.
Nitrogen.
Sulphur.
Ash.
Malt diastase
45-68
6-90
4'57
6 08
j j j j
47-57
6-49
5-14
...
3-16
Invertase .
43-10
7-80
4-30
...
6-10
>
43-90
8'40
6 00
0-63
3 )
40'50
6-90
9 30
...
Ptyalin .
43-10
7-80
11-86
6-10
Trypsine .
5275
7-50
16-55
17-70
Pepsine
53-20
670
17-80
...
Pancreatin
43-60
6-50
13-81
0-88
7-04
Emulsin
43-06
7'20
11-52
1-25
48-80
7-10
14-20
1-30
...
It will be seen from the foregoing table that considerable
differences exist between the various enzyme bodies, these differ-
ences being due to imperfectly purified substances. The diffi-
culty of obtaining these bodies free from ash and carbo-
hydrate matters, with which they are always contaminated, being
the cause.
All the enzymes when in solution are extremely susceptible to
elevated temperatures, their power being weakened, and if the
heating be continued they are wholly destroyed, the destruction
being usually accompanied by separation of the albuminoid in an
insoluble form, since many of them appear to belong to the group
of coagulable proteids.
96 THE BREWER'S ANALYST
ENZYME GROUPS.
The enzymes may be divided into the following seven groups,
in which they are arranged according to their respective specific
actions :
GROUP I. Diastatie Enzymes :
Diastase of secretion (malt) . } , . ,
, ( . \ Convert starch into mal-
Translocate diastase (barley) . ,
Ptyalm (saliva) . . . '
Glucase (maize) /Converts starch finally
( into glucose.
GROUP If. Cyto-hydrolytic Enzymes:
Cytase (malt) . . . . | Transform cellulose into
Enzymes of seeds in which the r sugars, such as man-
reserve material is cellulose . ' nose, xylose.
GROUP III. Pectin Enzymes:
Enzymes which convert pectinous substances into vege-
table jelly.
GROUP IV. Inverting 1 Enzymes :
Invertase (yeast) . . . ) Convert cane-sugar into
Invertase (malt) . . .1 invert sugar.
Maltase or glucase (yeast) . ) Transform maltose into
Enzymes of the small intestine J glucose.
Enzymes of yeast which degrade the intermediate dextrins
into maltose ; these are especially present in wild
yeasts.
Enzyme of Kephir . . . Inverts milk-sugar.
Probable enzyme of germinating ) Converts maltose into
barley . . . . J cane-sugar.
GROUP V. Proteolytie Enzymes :
Enzymes of malt and other ^
vegetables (sometimes called Convert P roteids into
peptase), but which have not f P roteose ' peptones,
i j ,, ., , . i , i and amides,
yet been definitely isolated . J
Trypsin (pancreas) . . | Amido acids and hexone
I bases.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 97
j Converts proteids into
Pepsin (stomach) . . proteosesand peptones,
' but not into amides.
Peptonising ferments secreted by many bacteria.
GROUP VI. Glucosidal Enzymes :
Splits up amygdalin into
oil of bitter almonds,
Jijniulsin (bitter almond) . . i , , . .-,
hydrocyanic acid, and
water.
Many other enzymes which have the power of hydrolysing
glucosides.
GROUP VII. Zymase (yeast) :
Splits up sugar into alcohol and carbon-dioxide.
ACTION OF THE PROTBOLYTIC ENZYMES ON THE PROTEIDS.
From the preceding list showing the various groups of enzymes,
we have, amongst others, those of animal origin, which act upon
insoluble proteids as follows :
1. The pepsin group, which act upon albumins, degrading them
to proteoses and peptones.
2. The trypsin group, which act upon albumins, resolving them
beyond the peptone stage, with the formation of simpler com-
pounds, viz., amido acids and hexone bases.
There is no doubt that proteolytic enzymes exist in plants,
since, as already mentioned, before the reserve materials stored
up by plants can be made available for the operations of nutrition,
they must first be converted from their inert and mostly insoluble
state into a state of solution and adaptability to circulate in the
nutritive fluid of the plants.
Group-Besanez, in 1874, 1 was the first to conclude that a
proteolytic enzyme existed in germinating barley, and he con-
sidered he had extracted it not only from barley, but also from
tares, hempseed, and linseed.
It is extremely doubtful, however, whether or not he detected
such enzyme, and in any case his method for detecting the pro-
ducts of its action is open to criticism. A powerful enzyme of
this nature has, however, been lately isolated in a fairly pure
state from the latex of the tropical plant Carica papaya, so that
proof is no longer wanted of its existence in plants, although it
has not yet been isolated from barley or malt. Shortly after
1 Berichte, 1874, 7, 1478.
7
98 THE BREWER'S ANALYST
Group-Besanez's investigations, Neumeister, 1 working with ex-
tracts prepared from germinating barley and green malt, obtained
products from blood fibrin which he considered exhibited char-
acteristic albumose and peptone reactions. Here the matter rested
until 1899, in which year Lazynscki 2 disputed the existence of
a proteolytic enzyme. In 1900, however, Fernback and Hubert 3
concluded that they had discovered it, and then followed other
investigations by Windisch and Schellhorn, 4 Petit and Labourasse, 5
Weiss, 6 and finally Schidrowitz, 7 all of which endeavoured to prove
the existence of a proteolytic enzyme in barley and malt.
The tests of these various investigators, however, have no real
value, and up to the time of writing no proteolytic enzyme has been
satisfactorily isolated from barley or malt, and on this account
there is and will be, from time to time, considerable controversy
as to whether barley or malt contains such an enzyme and whether
any peptonising action really takes place during mashing.
When germination commences in the grain of barley, it is
necessary that the starch stored up in its endosperm should be
able to travel to the growing germ. This is first effected by an
enzyme or amylo-hydrolyst (the translocation diastase) already
present in the seed, afterwards by another hydrolyst (ordinary
diatase) which is formed in considerable quantity during
germination. 8 In like manner the insoluble proteids in the grain
are, to a great extent, rendered soluble and diffusible, but in what
manner has not yet been settled, although from what has been
stated there is strong evidence of the existence of proteid-
hydrolysts both in barley and malt in spite of the fact of their
non-extractability therefrom.
As, therefore, we are unable to obtain a single proteolytic enzyme
from barley or malt, we have to rest content with a knowledge of
the action of the animal proteolytic enzymes, pepsin and trypsin,
which can be obtained in an almost pure state from the stomach
and pancreas of animals, and surmise, from their action, what
action takes place during the germination of barley and the
peptonisation of the proteids of malt during mashing.
Wort must contain proteid bodies of a nature readily assimilable
1 Zeit.f. Biologic, 30 (94), 447. 2 Zeit. f. d. gesammt. Brau., 22, 71.
3 CompL Rend. (4). 4 Wocliensch. Brauw. (1900), 17, 334-452.
5 Compt. If end., July 5 and 6, 1900.
6 Zeit.f. phys. Chem., 31, 78-97, and Zeit. ges. Brauw., 1903.
7 Jnl. Fed. Inst. Brewing, 1903, 361.
8 "Researches on the Germination of some of the Gramineae," Jnl. Chem.
Soc. Trans., 1890,458-528.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 99
by yeast, or the yeast would speedily become weak for want of
food and as a consequence become incapable of properly ful-
filling its functions. The albumin and globulins which occur in
barley seem completely indiffusible, but the proteoses and amides
are very highly diffusible.
These facts therefore show that the diffusible and assimilable
bodies requisite for yeast nourishment are yielded by the proteo-
lysis of the proteids originally contained in the barley, effected for
the most part during its germination, and afterwards, to a slight
extent, during the mashing process. Pepsin acts best in slightly
acid media, preferably 2 per cent, hydrochloric acid, and the most
favourable temperature for its action is 100 F. (37*7 C.), the
" blood-heat " of most mammals. When coagulated egg albumin
or other insoluble proteid is added to an acid solution of pepsin,
and maintained at a temperature of 100 F. (37'7 C.) for some
hours, the process of digestion is imitated, solution of the proteid
taking place accompanied by a degradation of the albumin mole-
cule to proteose and then peptone, the proportion of the latter
body being dependent upon the time of digestion.
Pepsin is incapable of degrading proteids beyond the peptone
stage, so that peptone must be considered the final product of its
action, although there is evidence that other bodies besides
proteoses and peptones are formed. These secondary products
result from the action of pepsin upon a portion of the peptone,
and although closely allied to this group, do not give the
characteristic reactions of these bodies.
According to Dr Sykes, 1 "The proteid molecule consists of two
distinct groups or radicles, from which the various products of
proteolytic action are derived. The following schematic arrange-
ment will, without going into too minute distinctions, give a
general idea of the series of changes :
Proteose
Deuteroproteose
Pro
Synt
beid
ilbumin
Anti-f
I
Peptone
IHetroproteose
Deuteroproteose
Peptone.
Principles and Practice of Brewing, 167-168.
100 THE BREWER'S ANALYST
"The great distinction between these two groups, which are
called the hemi- and an ti -groups, and which appear to exist in
about equal quantities, is that the peptone of the former can be
further broken down by the action of trypsin into a number of
amide bodies, whilst the peptone of the latter cannot be so
broken down. In every digestion a variable quantity of a
substance is left undissolved, which is called anti-albumin ; it is
extremely resistant to the further action of the proteolytic
enzyme, but, by treatment with strong solution of pepsin and acid,
may be partially converted into anti-deutero-albumose, and finally
into anti-peptone."
Sykes proposes l the following process for the estimation of the
proteids in malt : " The malt is extracted with cold water,
filtered, and the albumin in the nitrate coagulated at a tempera-
ture of 140 F. (60 C.). The coagulum is filtered off and
weighed. The filtrate is then boiled for a short time, when a
second precipitate forms, which is filtered off and weighed. This
is considered to represent the globulin, but from the recent
experiments of Osborne, it is extremely doubtful if all the globulin
can be separated by boiling.
"The filtrate is now evaporated to small bulk and saturated with
ammonium sulphate, when a precipitate consisting of the proteoses
(and probably some globulin) comes down. This is filtered off,
washed with saturated solution of ammonium sulphate, dried and
weighed, the weight of the ammonium sulphate, adhering to the
precipitate and filter paper, being determined and deducted. The
filtrate from this precipitate is then diluted with an equal
quantity of water, and solution of tannic acid added. This pre-
cipitates peptone, if it be present; but no precipitate of any
moment has ever been observed, which leads to the conclusion that
real peptone does not occur in malt."
Szymanski considered that he had separated peptone from malt,
but from the process he adopted for its isolation, the substance
which he obtained and mistook for real peptone was evidently
deuteroproteose.
Sykes, experimenting on the proteids of malt, was never able
to detect a hetroproteose on dialysing the precipitate thrown
down by ammonium sulphate.
A precipitate was always yielded on saturating malt extract with
sodium chloride and adding a little acetic acid, leaving the body in
solution which Szymanski mistook for peptone. In all probability,
therefore, the two proteoses are proto- and deutero-proteose.
1 Jnl. Fed. Inst. Brewing, vol. jv, 173.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 101
DIASTASE.
The diastatic enzymes^ are of the greatest importance and
interest in brewing and malting, from the fact that they embrace
the numerous bodies which have the power of liquefying and
saccharifying starch.
Of this group, malt diastase is the best known, for the reason
that it has received the most attention from scientific investigators.
In 1811, Kirchoff found that the albumin contained in barley
is capable of acting upon soluble starch and producing a
cry stalli sable sugar similar to that produced when starch is
boiled with dilute acid ; and he noticed that this action is greatly
intensified if the barley is germinated or malted.
Payen and Persoz, in 1833, were the first, however, to isolate the
soluble " ferment " and to identify it as the principle which is
capable of exercising such a powerful action upon starch. They
gave it the name diastase, which it still retains. This name was
given on account of the agent's supposed property of separating
the interior of the starch granule (granulose) from its outer
membrane (amylo-cellulose), but, as is now well known, this is
not strictly true, and furthermore erroneous ideas prevailed as to
the nature of the sugar produced by its action.
The isolation of diastase from malt was undoubtedly a most
important discovery, but little further advance was made until
O'Sullivan, in the course of his researches upon the products of
the hydrolysis of starch, again isolated it in a fairly pure state,
and from his study of its specific action under varying conditions
of temperature, evolved many of the principles which are now
well known to govern its action.
Diastase has been detected in almost all animal tissues and
vegetable substances ; thus Payen and Persoz detected its presence
in many germinating seeds, such as wheat, maize, rice, oat, potato
tubers, and in the buds of Ailantkus glandulosa ; Kossmaun and
Kranch found it in foliage and vegetable shoots ; whilst we owe
to Kjeldahl the observation, confirmed by Brown and Morris, of
the presence of diastase, albeit in sparing quantity, among un-
germinated seeds.
Mulder mentions its occurrence in saps which contain starch,
Hansen found it in the sap of Ficus carica, and Gonnermann
detected it in Beta vulgaris. To this we have to add that
Duclaux has shown the common moulds, Aspergillus niger and
PeniciUium glaucum, produce it in abundance ; that Bourquelot has
conducted a complete series of researches, having as its object the
OF THE
IIMIX/PDftlTY
102 THE BREWER'S ANALYST
discovery of diastatic ferments in mould fungi generally, and we
perceive how universal is the occurrence and how widely distri-
buted are amylo-lytic ferments in the vegetable world. Yeast
itself is said to contain a small quantity of diastase, whilst certain
Mucors, also thus endowed, are able to directly ferment starch.
The well-known Tonkin yeast, and even the better known
Koji yeast, the micro-organism employed in the production
of the Japanese beverage, Saki, afford peculiar symbioses of
diastase-producing mould fungi with alcohol-producing saccharo-
mycetes ; in the first-named case a mould, Amylomyces Rouxii,
being associated with a pastorianus yeast, and, in the second
instance, Aspergillus oryzse producing the taka diastase, whilst the
alcohol is formed by the action of some true alcoholic ferment.
Diastase has also been isolated from bacteria, investigators such
as Wood, Wortmann, Perdrix and others having succeeded in
proving its existence in organisms such as the Cholera vibrio, B.
mesentericus vulgaris, B. termo, and in fact practically every
micro-organism is now believed to secrete an enzyme capable of
dissolving starch.
Plants possess three distinct diastases, called respectively
secretion diastase, translocatiou diastase, and cytase; these are
respectively dealt with hereafter under Cytase, where diastatic
action from the maltster's point of view is detailed. From the
brewer's point of view, however, malt diastase is the agent which,
under suitable conditions during mashing, saccharines or trans-
forms soluble starch into dextrin, maltose, and intermediate
malto-dextrins. There is a further part played by diastase which
it is also necessary to remember, viz., the strobiles of the hop
plant contain active diastase which exercises an important
function in " hopping down," the conditioning of cask beer being
brought about to some extent by its hydrolysing action on the
residual malto-dextrins.
O'Sullivan obtained active preparations of diastase by digesting
finely ground malt, preferably low dried, with cold water for
several hours. The mass is then placed in a press and the
resulting extract filtered. On adding 80 per cent, alcohol to the
clear filtrate, a precipitate containing diastase is formed, which is
collected, washed with alcohol and finally with ether, and then
dried as quickly as possible in a vacuo desiccator over sulphuric
acid. During manipulation there is a liability, if the manipula-
tion be unduly prolonged, for the diastase to become converted
into a hard mass which is only partially and with difficulty
soluble in water.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 103
Lintner has devised a better method for preparing diastase
from malt, as follows :
One part of air-dried malt is digested for 24 hours with two to
four parts of 20 per cent, alcohol. The liquid is filtered and
precipitated by two or three times its own volume of absolute
alcohol. The precipitate, rapidly collected on a filter, is crushed
in a mortar with absolute alcohol, filtered, again washed with
absolute alcohol, then with ether, and dried in vacua. When the
operation is performed properly, it yields a white powder which
is readily soluble in water, giving an almost clear solution.
This method of precipitation by alcohol was first employed by
Payen, to whom we owe the earliest important work on diastase.
He had noticed what is also observed with Lintner's diastase, viz.,
that the precipitated substance is not free from mineral matter
(ash). The amount of ash decreases if the diastase is dissolved
in water and precipitated by alcohol, but at the same time it has
lost some of its strength, so that we arrive at this somewhat
paradoxical conclusion, that the purer the diastase, the less active
it is. Purification, instead of increasing, decreases the character-
istic property of diastase, viz., the power of saccharifying starch.
Lintner made the activity of his preparation the standard
(= 100) or basis of comparison.
Osborne, however, as previously mentioned, succeeded in
obtaining preparations of malt diastase, possessing much higher
diastatic power, by precipitating the diastase from cold-water
extracts by means of ammonium sulphate, and by repeated
solution in water and dialysis into alcohol whereby he succeeded
in obtaining diastase practically free from ash and having a
composition approximating very closely to vegetable albumin.
The preparation had a diastatic power of 600, that is, six times as
great as that obtained by Lintner. Diastase prepared by the
foregoing processes is a white or pale yellow coloured substance
readily soluble in cold water, giving slightly opalescent solutions.
Its composition has been determined by various workers, but
considerable difference is shown in the different preparations
obtained, particularly in regard to the nitrogen percentage which
may be taken as a guide to the relative purity of the respective
samples.
Owing to the great diffusibility of diastase contained in malt,
it has been a very easy task for chemists to prepare it from
cold-water extracts of malt, and they have been enabled in this
manner to make a relative determination of the amount of
diastase contained in different malts, and to compare them from
104 THE BREWER'S ANALYST
that point of view. The extract of malt prepared in this way
has been generally employed for the study of diastatic action,
and the researches of Brown and Heron, followed 'by those of
Brown and Morris, have established the laws to which this action
is submitted, to the great benefit of the brewing trade.
These laws are so well known that it is only necessary to briefly
record them.
The maximum energy of diastase, in solution, is obtained at a
temperature slightly below 140 F. (60 C.), immediately above
this temperature it commences to lessen in activity. At 151 F.
(66 C.) this is distinctly pronounced, whilst at 169 F. (76 C.)
its action is almost entirely arrested, and at 177 F. (80'5 C.) its
power is destroyed.
Although, however, solutions of diastase are extremely sensitive
to the influence of heat, solid preparations carefully desiccated
and free from moisture may be heated to 250 F. (121*1 C.)
without their activity being destroyed. This different effect pro-
duced by heat upon the moist and dry substance fully explains
the practical observation of the great loss of diastatic activity in
malt during the first few hours upon the kiln, when the corns
contain a large percentage of moisture, and the relatively slight
influence of high-kiln temperatures when the malt is completely
dry.
Fernback states that the action of diastase, as well as that of
other enzymes, is, within certain limits, favoured by an increase
of the temperature.
The amount of starch transformed by a given quantity of malt
extract increases as the temperature rises. This point is very well
illustrated by Ehrich l :
Temperatures of Time employed for
Saccharification . Saccharification.
F. C. Minutes.
140 60 .... . 120
149 65 ... 25-30
158 70 .. 10
167 75 10
But there is another peculiarity of great importance in the
practice of brewing which, of all enzymes, diastase alone shows.
The amount of fermentable sugar varies with the temperature of
Saccharification. The lower the temperature the greater the
amount of maltose. So that, by employing a definite temperature
1 Der Bierbrauer, 1896, No. 7.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 105
of saccharitication, the brewer has in his hands the means of pro
duoing with a given malt a wort of a given composition, which
will, during the fermentation, yield a given attenuation.
We also find, in the researches of Brown and Morris, a third
point of the greatest practical importance. When an extract of
malt has been heated to a certain temperature, and is afterwards
employed for the saccharification of starch paste at a lower
temperature, the amount of maltose produced is the same as that
which would have been produced at the high temperature to
which the extract of malt had been previously heated. We learn
from this observation that the greatest attention should be paid
to the mashing temperature, as no change at all will be brought
about by the addition of cold water, if the temperature has been
raised too high at a certain period.
Science cannot at present give a satisfactory explanation of
these facts. It was formerly supposed that saccharitication was
produced by two distinct enzymes, one transforming starch into
maltose, the other producing dextrin. The former of these
enzymes was supposed to be destroyed at a lower temperature
than the latter, so that heating the malt extract restricted the
enzyme-producing maltose to a certain extent, and the liquid
obtained produced a wort containing less maltose than was
furnished by the same extract unheated. Different attempts
have been made, especially by Wijsman, to prove the existence of
these two enzymes, but, up to the present, no convincing experi-
ment has been published, and it seems that this hypothesis has
to be abandoned.
In addition to these considerations, it must be stated that
although we know what effect the action of heat has on diastase
from a practical point of view, we have very little information on
the way in which diastase is affected by heat. In a series of
experiments, Fernback noticed that if a solution of pure diastase
(after Lintner's process) be prepared and heated to 140 F.
(60 C.) in a water bath, it will, in a very short time, after less
than one hour, have lost a great part of its activity. This effect
will be observed even if the solution be heated in vacuo, so that
the possibility of an oxidation cannot be admitted, and is out of the
question. This temperature is one of the lowest at which
saccharification can practically operate, so that we are forced to
this conclusion : that, in malt, diastase is accompanied by
substances which confer on it a certain immunity a certain
resistance against the destructive action of heat. It is never-
theless most probable that, during the saccharifying process, a
106 THE BREWER'S ANALYST
part of the diastase undergoes destruction, and from that con-
sideration we understand the great practical utility of a fact
which is most generally observed, viz., that malt contains an
amount of diastase greatly superior to what is necessary for the
transformation of the starch present in the grain.
The twofold function of diastase, namely, the liquefying and
saccharifying, is only found in malt diastase. Kjeldahl showed,
in 1879, that barley diastase has the saccharifying power, but not
the liquefying. This latter power of malt diastase appears to be
closely associated with its ability to slowly dissolve the outer cell
membrane of the starch granule, hence if barley starch be digested
in the cold with a solution of malt diastase, erosion or pitting of
the starch granule occurs, an action which can be distinctly
observed by microscopical examination. Effront has shown that,
if malt or malt diastase is added to a cold-water extract of raw
grain, the power of the diastase is increased ; and that if malt or
malt diastase is added to a raw-grain infusion at a temperature
beyond that at which diastase is destroyed, liquefaction of the
starch takes place, but no saccharification. Although diastase is
capable, however, of exercising a liquefying power upon gelatinised
starch even in the cold, its action upon ungelatinised starch is
slow and negligible from a practical point, this being due to the
resistance offered by the amylo-cellulose which constitutes the
envelope of each starch granule. Hence, it is necessary, in order
that the action of the diastase upon starch granules may be
effective, to conduct the operation at temperatures favourable to
the solution of the cellulose by the diastase.
It has been found that between 130 and 140 F. (54 '4 and
60 C.) the hydrolysis of the cell wall is rapid and complete in
the case of malt and specially prepared raw grain such as maize
and rice flakes or grits, but that in the case of unprepared raw
grain it is necessary to conduct the operation at temperatures
more closely approaching the gelatinisation point of the starch of
the particular cereal employed.
As previously mentioned, then, the saccharifying power of malt
diastase is destroyed at a temperature of 177 F. (85'5 C.). The
liquefying power, however, is not wholly destroyed even up to a
temperature of 220 F. (104'4 C.), and this is, therefore, a
point of considerable importance in the liquefaction of starch
when carrying out raw-grain conversion in specially constructed
vessels.
The nature of the medium in which diastase acts, whether acid
or alkaline, also exerts a very important influence not only upon
PKOTEIDS OR ALBUMINOIDS AND ENZYMES 107
the activity of the enzyme in respect to the amount of starch
hydrolysed, but also upon the nature of the products formed.
Its maximum action is exerted in neutral solutions, comparatively
small quantities of free acid or alkali being extremely prejudicial.
Brown and Morris found that when only slightly alkaline
('005 per cent.) with barium hydrate, sodium carbonate, or sodium
hydrate, its saccharifying power is very much restricted, and
that further increase of alkalinity completely inhibited its power.
The restrictive action of free acid is also well known.
Ling showed that diastatic action is completely arrested by the
presence of *007 per cent, hydrochloric acid and by alkalies.
Other acids, even carbonic, in like manner exert a restrictive
influence. On the other hand, the presence of acid salts,
particularly the phosphates, appears to exert a favourable influence.
Effront has shown that diastatic action is favoured by the
presence of small amounts of asparagin, ammonium acetate,
ammonium chloride, alums of potash and soda, phosphoric acid,
and of ammonium phosphate.
In the presence of 0'4 per cent, of asparagin, the amount of
maltose calculated on the dry substance after one hour's action
at 122 F. (50 C.) was found to be 58'2 per cent., whereas
without asparagin it was only 16*4 per cent. Analogous effects
were observed with the other bodies mentioned, and as the
presence of some of these substances is not excluded, moreover,
is certain, in the extract of malt, we must take them into account,
and we are led to conclude that they play an important part in
diastatic action.
A mash always shows an acid reaction, but this is not due to
free acid, but rather, as has been explained by Fernback, Prior,
and others, to the presence of acid phosphates pre-existing in
the malt or formed by the interaction of the saline constituents
of the mashing liquor and the potassium phosphates of the malt.
From the foregoing details it will be understood why many
conflicting statements have been made by different observers and
investigators as to the absolute energy of diastase. Payen and
Persoz estimate that it is capable of converting 2000 times its
own weight of starch into sugar.
Dubrunfaut, who pursued his investigations on this active
agent up to the time of his death, alleges that malt contains
1 per cent., and that it possesses a power capable of converting
150,000 to 200,000 times its weight of starch. Roberts found
pancreatic diastase to convert. 40,000 times its weight of starch,
and other distinguished observers state that malt contains only
108 THE BREWER'S ANALYST
002 to "003 per cent., and that its converting power is as stated
by Payen and Persoz.
Although the converting power of diastase is very great, a
small quantity being capable of saccharifying a very large amount
of starch, this statement, as will have been seen, only applies
when time, temperature, and concentration are taken into account.
Hence when the time is limited, the converting power of the
enzyme is also limited. In equal intervals of time, and under
definite conditions, the quantity of starch converted is proportional
to the amount of active enzyme present.
This is what is known as Kjeldahl's "law of proportionality,"
and was expressed by him in 1879 as follows: " When equal
volumes of two diastatic solutions are allowed to act upon solutions
of soluble starch under identical conditions of time, temperature,
and concentration, then the cupric reducing power of the tivo solutions,
taken at any given time, is a measure of the relative transforming
powers of the diastatic solutions, providing the cupric reducing
power when calculated as percentage of dextrose is not allowed to
exceed K 25 to 30." In other words, if the amount of maltose
formed does not exceed 40 to 50 per cent, of the starch originally
taken, the relative activities of the two solutions can be deter-
mined from the amounts of maltose formed in a given time, since,
under such conditions, the formation of maltose is proportional
to the amount of diastase present. In the mashing process the
amount of maltose formed is, however, not necessarily proportional
to the diastatic powers of the respective malts, since, in this case,
the diastase is present in excess, and, further, the products of
hydrolysis exceed the proportion above stated.
In 1886 Lintner elaborated a more accurate method for the
estimation of the diastatic power of malt, such method being
based on the same law "the law of proportionality" and
being the one now considered as the most satisfactory. Details
for carrying out the estimation are given hereafter under
" Diastatic Power " in malt analysis.
During the conversion of soluble starch by diastase, the
products formed consist of free maltose and dextrin, and of
intermediate bodies termed malto-dextrins or amyloins, which are
compounds of maltose and dextrin.
Although such intermediate products are undoubtedly formed,
the result of the action of diastase upon soluble starch can always
be expressed in terms of free maltose and dextrin. This "law
of definite relation," enunciated by Brown and Morris, is as
follows : " The products of a starch transformation can always
PROTEIDS OR ALBUMINOIDS AND ENZYMES 109
be expressed in the terms of maltose, having an optical activity of
[a] J3 . 86 =150, and a cupric reducing power K 3 . 86 = 61, and of
dextrin having an optical activity of []j 3 . 86 = 216, and no reducing
power."
Under normal conditions diastase has no further action upon
the maltose and dextrin first formed, but the malto-dextrins are
capable of further hydrolysis, being wholly converted by continued
digestion into maltose, the dextrin content of the malto-
dextrin thus behaving differently to the free or stable dextrin.
GLUCASE OR MALTASB.
The hydrolysis of carbohydrate bodies to the simple hexose
sugar glucose is performed by the group of enzymes termed
glucase or maltase, these designations being to a great extent
synonymous according to the different systems of nomenclature
adopted by different workers. Of the two glucase appears the
better term to employ, since it points to an enzyme capable of
acting upon carbohydrate substances producing glucose, whereas
the designation maltase appears to restrict the term to enzymes
capable of hydrolysing maltose only.
As will be shown later, the enzyme of yeast, which is capable
of decomposing the disaccharide maltose into the simple hexose
sugar glucose preliminary to fermentation, has also an action upon
dextrins, malto-dextrins, and, under certain conditions, hydrolyses
starch; hence it is preferable to employ the term glucase for
this enzyme rather than that of maltase, which was at first
adopted, and is now sometimes employed.
The glucases differ in their nature and properties according to
the source from which they are derived, those which have
received the most attention being derived from maize and yeast
respectively.
Musculus and Gruber were the first to mention the existence
of glucose as being produced by the action of diastase on starch
in addition to the main product maltose. This statement, there-
fore, is tantamount to showing that glucase exists in malt, but
opinions of different investigators are divided as to whether it
does or does not exist in malt; the balance of evidence so far
adduced, however, is in favour of its existence in certain classes
of malt at any rate. Apart from malt, Cuisenier, in 1855, proved
the existence of glucase in maize, and commercially worked an
industrial process for the production of glucose from maize.
Mering was the first to suggest that yeast contained a " ferment "
110 THE BREWER'S ANALYST
capable of converting maltose into glucose before alcoholic fer-
mentation, and Bourquelot shortly afterwards proved that maltose
is hydrolysed before fermentation is started, by acting upon
solutions of maltose with yeast in the presence of chloroform,
whereby the action of yeast cells is suspended.
More recent work, viz., that of Emil Fischer, has resulted in
substantiating Bourquelot's statement that yeast contains an
enzyme which hydrolyses maltose to glucose preliminary to
fermentation, the presence of the glucose being identified by his
now well-known osazone reaction with phenyl-hydrazine. Fischer's
investigations in these respects have since been repeated and
confirmed by Morris, who extracted the active enzyme from yeast
cells, quickly dried upon porous plates.
Besides the glucase of maize and yeast, the enzyme is widely
distributed in nature, and is frequently associated with the
diastatic enzymes. Bourquelot identified it in many plants and
nearly all moulds. It is not found, however, in the lactose or
kephir yeasts, S. marcianus or S. apiculatus.
In the majority of instances it is looked upon as a starvation
phenomenon, secreted by the living cell in proportion as it is
deprived of the presence of the simple hexose sugars, such as
glucose, which alone appear to be directly assimilable. Thus
many moulds which ordinarily contain glucase do not secrete
the enzyme at all if continuously supplied with saccharose or
glucose, but if their supply of these sugars is cut off and maltose
substituted, then the secretion of the enzyme, glucase, is at once
stimulated in the plant cell by its deprivation of suitable food.
Glucase is found associated with invertase and diastase in
Aspergillus oryzae, and it has been shown by Atkinson that the
final product of the action of this enzyme on gelatinised starch is
glucose and not maltose.
Glucases have been found in the saliva, secretions of the
intestines and the pancreas,, and in various organs of animals.
The methods adopted for extracting glucase are similar to those
employed in the extraction of diastase and invertase, the extrac-
tion being accomplished by suitable solvents and precipitation by
alcohol. In the case of yeast, which in the fresh state yields no
glucase to water, the yeast must first be dried quickly upon
porous plates at low temperature, and the resulting mass, after
pulverising, digested with water at 86 - 95 F. (30 - 35 C.), or
by extraction with 1 per cent, sodium hydrate, and subsequent
precipitation.
To study the action of the glucase of yeast upon maltose, fresh
PROTEIDS OR ALBUMINOIDS AND ENZYMES 111
yeast is suspended in a solution of maltose. If the fermentative
action of the yeast be inhibited by the addition of chloroform,
toluene, or thymol, in the course of a few hours the progress of the
hydrolysis of the maltose c"an be followed by the lowering of the
opticity of the solution and the increase of its cupric-reducing
power.
The glucase prepared from maize is of a light, friable character,
brownish in colour, dissolving in water with difficulty, and pre-
cipitated from its solutions by alcohol. Aqueous solutions of
glucase of different origin quickly lose their activity, and their
action is weakened by the presence of alcohol, chloroform, and
antiseptics. The enzyme acts most energetically upon maltose,
but most glucases are capable of acting upon dextrin and malto-
dextrins, and some are capable of hydrolysing starch. As a rule
the glucase of cereals hydrolyse maltose readily, but acts with
difficulty upon starch, whilst on the other hand the glucase of
moulds acts more vigorously upon starch than upon maltose.
The presence of a slight acidity is favourable to the action of the
glucases, but is entirely arrested when the acidity of the medium
is equal to or above ;2 per cent.
The optimum temperature and that at which the enzyme is
destroyed varies with its origin as follows :
Origin. Optimum Temperature. Destroyed at
OTjl f^ T? C*
Yeast . . . 120-2 49 131-0 55
Penicillium glaucum . 113'0 45 158*0 70
Eurotiopsis gayoni . 122'0 50 131'0 55
Aspergillus niger . 140'0 60 176*0 80
Maize . . . HO'O 60 158-0 70
CYTASE.
In their epoch-making paper, " Researches on the Germination
of some of the Graminese," Brown and Morris published an account
of the existence of an enzyme produced during the germination of
barley to which they gave the name cytase.
In order to thoroughly understand the action of this enzyme, it
is necessary to be first familiar with the structure of the barley-
corn and the morphological changes occurring during germination.
As before stated, under Diastase, plants possess three distinct
diastases, called respectively secretion diastase, translocation
diastase, and cytase. The first named is that present in germinat-
ing seeds ; the second is the diastase of ungerminated seeds and
112 THE BREWER'S ANALYST
other plant organs ; whilst cytase is an enzyme which possesses
the power of dissolving the cell walls.
The distinguishing feature between secretion and translocation
diastase is the inability of the latter to exercise any solvent action
on ungelatinised starch granules.
In the barleycorn the columnar cells (termed the epithelium,
forming the membrane intervening between the endosperm and
embryo) secrete the diastase necessary for the resolution of the
reserve material stored up in the endosperm, performing a duty
analogous to that of the alimentary canal and of the walls of the
stomach, which secrete the enzymes necessary for the proper
digestion and assimilation of food by animals.
During malting it was formerly considered that diastase was
the immediate cause of that mealiness and friability which
indicates the modification of rnalt ; or, in other words, that the
starch of the endosperm was gradually modified by the action
solely of secretion diastase. It is now shown, however, that
before this diastatic action can proceed, it is first necessary for the
cell walls to be dissolved, and the enzyme which performs this
dissolving action is cytase.
Cytase is the agent which attacks the cellulosic tissue of the
endosperm cells, breaking it down and causing its complete dis-
solution. 1 Following this there is an erosion of the starch
granules by secretion diastase, but this action on the starch
granules never takes place so long as the walls of the cells
containing them are intact.
The two enzymes diastase and cytase are quite distinct,
the action of cytase on the cell walls of the endosperm always
preceding that of the diastase on the starch granules. The pro-
duction of mealiness or friability in the content of the endosperm
is therefore, according to Brown and Morris, "coterminous with
the dissolution of the cell wall," and is entirely independent of the
disintegration of the starch granules.
In their endeavour to locate cytase in the barleycorn, Brown
and Morris state that the elaboration of the enzyme, as well as
the diastases, is carried out by the columnar cells forming the
epithelium dividing the scutellum of the embryo from the endo-
sperm ; and that its first action could be traced upon the depleted
cells adjacent to the embryo, and thence proceeding slowly
1 It appears to be an open question as to whether the cell walls are entirely
or only partially dissolved by cytase, but apart from this it is sufficient that
cytase opens the door sufficiently wide, so to speak, to render the starch of
the endosperm permeable to the action of secretion diastase.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 113
throughout the corn. Tangl and Haberlandt were able to show,
however, that the secretion of cytase is not due to the epithelial
cells alone, but that a triple row of cells surrounding the endo-
sperm, termed aleurone ceUs, exercise a marked influence upon the
progress of the dissolution of the cell wall, and this view was
afterwards accepted by Brown and Escombe.
Sachs was the first to demonstrate the existence of a special
enzyme capable of attacking the less resisting forms of cellulose
during germination of the date seed, and later Green endeavoured
to isolate the enzyme. Brown and Morris were the first, however,
to isolate cytase from malt, and this they accomplished by making
infusions of air-dried malt, precipitating the enzyme with alcohol,
and carefully drying the precipitate in vacua. This preparation
was found to exhibit marked cyto-hydrolytic action (cellulose
dissolving power). Its action upon cellulosic tissue is, however,
more or less restricted to the cell walls of the endosperm of the
seeds from which the enzyme has been derived, or similar tissues
from seeds belonging to the same material order. Thus the
cytase derived from germinated barley acts readily upon the
cellular tissues of the endosperm of the Graminese, but is less
active towards similar tissues from other groups ; and it appears
to be a general rule that the cytases are most active upon the
cell walls of the particular seed in which the enzyme has been
elaborated.
Cytase is not capable of acting upon all forms of cellulose, this
term being used to embrace the members of a general group of
substances, forming the fabric of plant structures, similar in
chemical composition but differing in certain chemical and
physical characteristics. Thus the cellulose material forming
parenchymatous tissue, as found in the cellular membranes of the
barleycorn, is less resistant to chemical and enzyme action than
the lignified tissues of cellulose constituting the husk. As will
have already been seen under Cellulose, the former kind is termed
hemi-cellulose in order to distinguish it from the more stable and
resistant forms which are unacted upon.
The products of the action of cytase are generally understood to
be substances of a gummy nature, but have not yet been identified ;
whatever the nature of such products may be, it is generally
considered that they serve as food for the embyro during the
early stages of germination.
Giiss considers the hemi-cellulose of barley to be of the nature
of arabinoxylan, yielding, as the result of cyto-hydrolysis, the
pentoses arabinose and zylose, and similar substances have been
114 THE BREWER'S ANALYST
shown to exist in cold-water extract of malt, Morris indicating
that the unfermentable reducing residue of beer may in some
measure be attributed to the products of cytase hydrolysis during
germination.
Cytase is very sensitive to the action of heat. The activity of
a cold-water infusion of air-dried malt is greatly weakened in its
action, so far as cellulosic tissues are concerned, if heated to 122 F.
(50 C.), and this power is completely destroyed if heated for a
short time to 140 F. (60 C.), although the amylo-hydrolytic power
of diastase is still energetic in its liquefying and saccharifying
action upon starch granules beyond these temperatures. Owing
to this ready destruction of the enzyme, it will be understood that
only green malt, dried at a low temperature, contains active cytase,
ordinary malt being devoid of it owing to its complete destruction
during kiln-drying.
INVERTASE.
Invertase was discovered in 1830 by Doebereiner and Mitscher-
lich, who described it as a "soluble material" extractable from
yeast when the latter substance is mixed with water. The soluble
material liquefies cane-sugar and produces inversion in it by
causing it to take up the elements of water.
In 1860 Berthelot discovered that invertase could be pre-
cipitated, by means of alcohol, from its solution without losing its
activity, arid since this date numerous experimental data, showing
means by which the ferment can be extracted from yeast and its
properties when extracted, have been produced by Be'champ,
Donath, Seyler, Gunning, Tulkowsky, Konig, Kjeldahl, Mayer,
Earth, and Miiller. In all their experiments, however, no notice
was taken of the age of the yeast or its condition as regards health
or disease, and this seems the more strange considering that long
previously (1835) Schwann had shown Leuwenhoek's globular
yeast particles to be alive. All of any considerable importance
that was pointed out in this direction was that dead cells parted
with their invertase more freely than living cells, no mention
being made of the further fact that healthy yeast yields none of
its invertase or hydrolysing agent or enzyme to water in which it
is washed.
The widespread occurrence of cane-sugar or saccharose in nature
is well known, but the biases, to which group cane-sugar belongs,
are not directly fermentable or immediately available as plant
food, but require to be split up into the simple liexose sugars,
dextrose and levulose, before either fermentation or assimilation
PROTEIDS OR ALBUMINOIDS AND ENZYMES 115
by the living cell can take place. Hence it is that nature provides
the transforming enzyme, and that cane-sugar in nature is
accompanied by the existence of invertase in the saps and juices
of plant cells which depend for their nourishment upon the
assimilation of the sugar.
Invertase plays an important part among the higher plants in
as much as by its aid the cane-sugar carried by the sap is rendered
available for building up the cell fabric. It is found in all parts
of the Gramineae ; C. O'Sullivan demonstrated its presence in the
roots, stalks, and leaves of wheat and maize, and others have noted
its presence in the leaves of many plants belonging to different
natural orders. Its presence in green malt is undoubted, and
according to Brown and Morris, Kjeldahl and others, it is present
in kilned malt, not being wholly destroyed during kilning. In
animals, invertase has been located in some of the organs, its
presence in the intestinal secretions being first discovered by
Bernard.
Invertase is invariably present in yeast cells, usually associated
with other enzymes such as glucase and zymase. It is not, how-
ever, present in all yeasts, for Hansen has shown that Saccharo-
myces apiculatus, the yeast found on many fruits, is devoid of it.
Invertase has been found in many of the mould fungi, among
which the genus Aspergillus may be specially mentioned, the
invertase of Aspergillus niger, Aspergillus oryzx, or taka ferment
having been closely investigated. Invertase is also secreted by
Mucor racemosus, Penicillium glaucum, and Penicillium Duclauxii.
It also occurs in many species of Fusarium, and has been shown
to be present in Manila Candida. Its occurrence in this organism
is of special interest from the fact that, although it readily
transforms cane-sugar, an active enzyme cannot be prepared from
it by the usual methods, the investigations of Fischer and others
having demonstrated that, unlike the invertase of most organisms,
the invertase secreted by Manila Candida is insoluble.
Invertase has also been shown to be secreted by many bacteria,
among which B. mesentericus vulgatus, B. megatherium, and the
Cholera vibrio may be mentioned. It also occurs in Leuconostoc
mesenter bides, the "frog spawn" of beet-sugar juices. J.
O'Sullivan states :
" 1. Healthy yeast yields none of its invertase or hydrolytic
power to water in which it is washed.
"2. When healthy yeast is placed in contact with cane-sugar
solution, the hydrolysis that takes place is solely an action under
the immediate influence of the plasma of the cell, and no invertase
116 THE BREWER'S ANALYST
leaves the yeast cell during the time the hydrolysis is being
effected.
" 3. The hydrolytic action of yeast on cane-sugar takes place
without increase of yeast, and there is no alcohol formed. The
power which yeast possesses of producing alcoholic fermentation
is not altered in any way by the yeast having first hydrolysed
sugar-cane, and this is the case whether the hydrolytic action is
brought about in the first instance in the presence of air or
carbon-dioxide."
C. O'Sullivan and Tompson point out as follows :
" 1. When yeast is placed in cold water and allowed to remain
for a few hours, what is known as ' osmosis ' takes place, that is
to say, a soluble albuminous substance contained in the torpid and
dead cells, being extremely soluble in water, diffuses through the
cell membrane of the yeast and passes into the exterior liquid.
"2. If sound brewers' yeast be pressed and placed in a large
wide-mouthed vessel covered with a filter paper to prevent access
of dust, and allowed to stand at the ordinary temperature for a
month or two, or at a temperature of 64-4 -68'0 F. (18-20
C.) for 7-14 days, during this time auto-fermentation of the yeast
takes place, and the mass liquefies, yielding a thick yellow liquid
of not unpleasant smell. If this liquid is then filtered by the aid
of a filter pump, a clear yellow liquid is obtained, having a specific
gravity of 1075"-! 080. The filtrate has an inverting power
equal to 30 per cent, of the original yeast. It will remain for a
long time unaltered, excepting that the colour darkens ; and if
exposed to the air, it may slowly become covered with mould.
If spirit be added to the yeast liquid until the mixture contains
47 per cent, of alcohol, the whole of the invertase separates with
only a slight loss of power.
" This precipitated invertase may be washed with spirit of the
same strength, and then the residue either dehydrated with
strong alcohol and dried in vacuo, or else it may be extracted by
means of 10 to 20 per cent, alcohol and then filtered. The
filtrate contains the invertase. On one occasion it was deter-
mined what the loss involved by this process amounted to, and
it was found that 87 '7 per cent, of the invertase of the yeast
liquor was present in the filtrate."
C. O'Sullivan and Tompson have not, up the present,
succeeded in further purifying invertase preparations carefully
made in this manner, as the slightest attempt at purification
destroys the invertase. They have, however, succeeded in
preparing the enzyme almost free from ash.
PROTEIDS OR ALBUMINOIDS AND ENZYMES 117
Invertase prepared by the foregoing process is a fairly white
powder, which soon becomes yellowish on exposure to air and
light. It is soluble in water, giving clear solutions which are
not coagulated on heating. Solutions of invertase are dextro-
rotatory, and, according to 0. O'Sullivan, the specific rotatory
power of pure invertase is [a\- } = + 80. Invertase is readily
precipitated from its solutions by the addition of alcohol, and is
completely insoluble in alcohol of specific gravity '940. The
precipitates are of a semi-syrupy nature, and usually contain
inorganic salts precipitated from the solutions by alcohol,
although a considerable quantity of these inorganic bodies can be
eliminated by washing the precipitate with alcohol.
Invertase can be separated from solutions by filtration through
porcelain or by parchment in a dialysing apparatus. It is
difficult to keep it either in solution or as a dry preparation
without loss of power, this being probably due to oxidation in
the presence of light. It is extremely sensitive to temperature
above the normal or optimum when in solution, but when
perfectly desiccated will withstand the temperature of the boiling-
point without appreciable loss of power.
Little is known of the constitution of invertase j most
authorities concur that it is not an albuminoid. It gives no
coloration with Millon's reagent in the cold, but on heating, a
pink coloration is produced. It does not reduce Fehling's
solution.
O'Sullivan considers invertase, as separated from yeast, to be
a mixture of yeast albuminoid and a carbohydrate. As the
invertase approaches the pure state it becomes a very unstable
body, the purification resulting in the formation of decomposition
products designated the Invertan series, which may be expressed
in terms of a carbohydrate of the formula :
Carbon, 43*22, hydrogen, 6 28, oxygen, 50'40, and an
albuminoid (yeast albuminoid)
Carbon, 54'33, hydrogen, 7 '50, nitrogen, 14 '88.
Seven members of the Invertan series were examined and their
properties described. According to O'Sullivan the proportion of
carbohydrate to yeast albuminoid varies from '74 part in a
Invertan, the first member of the series, to I2'84 parts in n
Invertan. All the members of the group are devoid of inverting
power with the exception of the second member of the l> Invertan,
this constituting the true enzyme invertase.
The action of invertase upon cane-sugar is one of simple
hydrolysis, and the change, which is precisely the same as that
118 THE BREWER'S ANALYST
effected by acids, consists in the assimilation of water by the
cane-sugar molecule, followed by its separation into the two
different kinds of sugar dextrose and levulose which though of
very different properties have the same formula :
C 12 H 22 O n + OH 2 = C 6 H 12 6 + C f) H 12 6 .
Cane-sugar. Water. Dextrose. Levulose.
Invert-sugar.
Like most enzymes, the action of invertase is influenced by
concentration, temperature, and the nature of the medium; the
amount of inversion being governed by the quantity of invertase
present and the time its action is allowed to continue.
The most favourable concentration for sugar solutions is
between 20 and 30 per cent, of sugar, a decline in the speed of
inversion taking place when the solutions are dilute or in
saturated solutions above 40 per cent. The rapidity of inversion
is greatly influenced by the temperature. At low temperatures
the inversion proceeds slowly, rapidly increasing with every
increment of temperature until the optimum of 131-140 F.
(55-60 C.) is reached. The optimum temperature is not a
constant one, but varies according to the source from which the
invertase is derived. The invertase of top fermentation yeast
acts best at a temperature of 131-140 F. (55-60 C.), whilst
the invertase from bottom fermentation yeast exhibits its
maximum effect between 86-95 F. (30-35 C.). At tempera-
tures above 140 F. (60 C.) the activity declines, and the
enzyme is weakened by exposure to the elevated temperature
until at 167 F. (75 C.) it is totally destroyed.
The activity of invertase is at a maximum when acid is present
iu normal amount, this, according to O'Sullivan being, for tempera-
tures of 131-150 F. (55-65-5 C.), 1'25 parts SO 3 per 100,000
(=0016 percent. H 2 S0 4 ).
It is, however, extremely sensitive to any increase of acidity.
The presence of alkali is absolutely destructive to its action, and
the presence of alcohol is distinctly prejudicial, the decrease of
activity being proportional to the amount -of alcohol present.
The action of invertase upon cane-sugar is rapid in regard to
speed and enormous as to amount. O'Sullivan illustrates these
points by two striking experiments :
A preparation of invertase reduced the optical activity of a
solution of cane-sugar to the zero point [a] D = in 25'1 minutes,
the sugar being present in the proportion of 100 to 1 of invertase
added. This is equivalent to the inversion of 74 times its own
PROTEIDS OR ALBUMINOIDS AND ENZYMES 119
weight of cane-sugar in 25*1 minutes. By adding a weighed
quantity of invertase to a large bulk of cane-sugar, and digesting
at a temperature of 122-1 29-2 F. (50-54 C.) for a fortnight,
it was found that an inversion equal to 100,000 times its weight
of invertase added had taken place, and that the inverting action
was still slowly progressing.
ZYMASE.
In 1 897 the scientific world was startled by the discovery by
Dr E. Buchner of an enzyme extractable from yeast capable of
fermenting solutions of cane-sugar. The idea was at first looked
upon as incredible, owing to the long-cherished famous dictum of
Louis Pasteur, viz., that " Fermentation is the physiological effect
of the life-action of yeast and other cells." Buchner, however,
very quickly proved his point, having succeeded in extracting from
yeast an active liquid capable of effecting the decomposition of
sugar without the direct agency of living cells, and established
beyond question that the production of alcohol by yeast fermenta-
tion does not differ essentially from other zymolytic decomposi-
tions, but is analogous to the inversion of cane-sugar by invertase,
and the hydrolysis of maltose by yeast glucase. Buchner obtained
the active alcoholic enzyme as follows :
Fresh yeast is first subjected to a pressure of 750 Ibs. to the
square inch, in order to free it from adherent liquid. It is then
mixed with an equal weight of quartz-sand and a fifth of its
weight of kieselghur 1 , and placed in a grinding mill driven by a
motor, and ground until the mass, at first pulverulent, becomes
moist and adheres together in balls. The object of this grinding
is to rupture the walls of the yeast cells, and to permit their
protoplasmic contents to escape. The doughy mass is then
enveloped in a cloth and placed in a hydraulic press, where it is
slowly and gradually submitted to pressure until at last a pressure
of between 3 and 3J tons to the square inch is reached. After
about two hours the cake is removed from the press, broken up,
and moistened with water. It is then pressed as before. In this
way a mass of yeast yields about half its weight of yeast extract,
rather less than three-tenths of this extract consisting of the
water added to moisten the yeast cake. The yeast extract, as it
drops from the press, is allowed to pass through a funnel,
provided with a filter paper, into a vessel which is kept in ice, in
order to prevent decomposition of the extract as much as possible
1 A fine, earthy powder which consists of the siliceous coverings of diatoms.
120 THE BREWER'S ANALYST
during its preparation. A microscopic examination of the yeast
cake after the second pressing shows that only about 4 per cent,
of yeast cells remain intact. The extract obtained in this way is
a clear or slightly opalescent liquid, with a pleasant yeasty odour,
its specific gravity being about 1041 '6. On boiling, a considerable
amount of coagulum forms, so much so that the liquid is converted
into an almost solid mass. But the most remarkable property it
possesses is the power of inducing fermentation.
When equal volumes of the extract of a concentrated solution
of sugar-cane are mixed, or if powdered sugar-cane is dissolved in
the extract, in from 15 minutes to an hour a regular evolution of
carbon-dioxide commences, and this continues for several days.
Saturation of the mixture with chloroform does not arrest the
action, though it is a well-known fact that this substance com-
pletely stops fermentation when conducted with ordinary living
yeast. The fermentative power of the extract is not destroyed
when the extract is passed through a Berkefeld filter, and this
treatment would certainly remove from it all living organisms.
The yeast extract gradually loses its fermentative power when
kept at the temperature of an ice chamber, much more rapidly at
higher temperatures. It has been pretty conclusively shown
that this is due to the destruction of the zymase by another
enzyme of a proteolytic nature present in the extract. Living
yeast is unable to ferment solutions of cane-sugar of 50 to 60 per
cent, strength, or solutions to which large quantities of glycerine
have been added ; zymase ferments these readily. Like most"
other enzymes, zymase can be precipitated by alcohol, but on
subsequent solution in water it is found to have lost very much
of its activity. It may be obtained, however, in the dry state,
with little or no loss of activity, in the following manner :
500 c.c. of fresh yeast extract are evaporated, in a vacuum
apparatus, at a temperature of 68-77 F. (20-25 C.) until
of a syrupy consistency ; the syrup is then spread in thin layers
on glass plates and dried at a temperature of 93-95 F. (34-
35 C.) either in a vacuum or in the air, since it is found that,
when the above-mentioned degree of concentration has been arrived
at, air has no longer any effect upon the zymase. The dried
extract is then scraped off the plates, reduced to a powder, and
brought to a state of absolute dryness by being placed in a
desiccator over sulphuric acid. The 500 c.c. of yeast extract is
found to yield about 70 grams of this yeast powder, which has a
pleasant yeasty odour, and in appearance somewhat resembles
dried white of egg. If the 70 grams of yeast powder so obtained
PROTEIDS OR ALBUMINOIDS AND ENZYMES 121
are dissolved in 500 c.c. of water, that is, made up to the same
strength as the original yeast extract from which it was prepared,
a solution is obtained which possesses nearly the same fermenta-
tive power as the original yeast extract.
In the dried form the fermentative power of the enzyme can
be preserved for a longer period than in the liquid state, some
preparations retaining their activity for 20 days, whilst those
concentrated in vacuo preserved their full activity for over two
months.
Buchner further demonstrates that the yeast cell can be so
dried as to destroy its vitality without impairing the activity of
the zymase, which can still exert its fermentative function in situ
within the cell membrane. The yeast is first well washed with
water, and after removing extraneous moisture as much as
possible by pressure, it can be perfectly dried in two or three .
days if spread out in thin layers, A yellow powder is obtained *";
which, on heating to 212 F. (100 C.) for 5 to 6 hours, becomes
completely sterile, the vitality of the cells being wholly destroyed
and no longer capable of developing in nutrient solutions. That
the zymase is not destroyed by this procedure is evidenced by the
fact that, when the powder is placed in a saccharine solution,
fermentation is set up.
Yeast extract, representing the sap or juice of the cell, contains,
besides zymase, those other enzymes known to be secreted by the
living cell, viz., invertase and glucase, in addition to which a
proteolytic enzyme and an oxydase have been noted. The
presence of an amylase, however, does not appear to have been
definitely established. Hence the zymase is capable of fermenting
those sugars which are ordinarily decomposed by the living cell,
whether directly as dextrose and levulose, or fermentable only
after hydrolysis, such as saccharose, maltose, etc., which require
the presence of specific enzymes. It has been found that maltose,
saccharose, dextrose, and levulose are equally rapidly fermented
by zymase. In the case of the two last-named sugars, how-
ever, this is not the case when fermented by the living cell, the
greater diffusibility of dextrose through the cell membrane
causing the fermentation of this sugar to proceed more quickly
than that of levulose ; in fact a solution of invert-sugar under-
going fermentation increases in Isevo-rotatory power. With
the expressed yeast extract (zymase) this phenomenon does
not occur, both dextrose and levulose being decomposed uniformly.
Of other carbohydrates, raffinose, galactose, and glycogen are very
slowly attacked, whilst lactose and arabinose are not fermented
122 THE BREWER'S ANALYST
by it ; in fact only those carbohydrates which are readily hydro-
lysed by the enzymes of ordinary yeast with the formation of
simple hexose sugars are capable of fermentation by yeast.
Buchner, studying the specific action of zymase, found that
the relative proportion of C0 2 to alcohol produced by the enzyme
during fermentation, does not wholly agree with the ratio obtain-
able by living-cell fermentation, the amount of alcohol being
usually in excess. In one experiment the quantities found were
C0 2 = 6'7 grams, alcohol 7'72 grams, an excess of '72 grams
alcohol.
Macfadyen and Morris also showed that the amounts of alcohol
and carbon-dioxide produced were less than should be yielded by
the amount of saccharose which disappears, so that it is evident
that the decomposition of sugar by zymase, like the action of the
living cell, cannot be a simple decomposition such as can be ex-
pressed by the equation of Gay-Lussac
It is more than probable, therefore, that complex combinations
between the enzyme and the carbohydrate, followed by decom-
position, take place before the final products, alcohol and carbon-
dioxide, result. In cell fermentation, too, secondary products,
glycerol and succinic acid, are formed ; and the investigations
of Buchner show that these products are also formed by the
action of zymase, although in much smaller amount.
The fermentative power of zymase was found by Lange to
increase with the ratio of nitrogen, this fact being in accordance
with the conclusions of Hayduck, who showed this to be the case
with living yeast. Zymase appears to closely resemble albumin,
but it differs in many respects from invertase. It is in some of
its properties analogous to the enzyme of Manila candida, par-
ticularly in the extreme difficulty with which it diffuses, if at
all, through cell membranes or parchment. Although the
action of zymase is not impeded by the presence of antiseptics
which are inimical to yeast growth, thus behaving as a true
enzyme, it is extremely sensitive to the presence of excessive
amounts of inorganic substances. Neutral salts in small quantity
appear to favour the action, but if they are increased beyond 1 '5
per cent., the action is completely arrested. Acids and alkalies
are both unfavourable, but in minute quantities appear to
stimulate it. Phosphates, particularly acid phosphates, in small
proportion, exercise a stimulating effect. Fermentation is
diminished by the addition of 15 per cent, alcohol, whilst the
PROTEIDS OR ALBUMINOIDS AND ENZYMES 123
presence of 20 per cent, completely arrests it, the enzyme being
practically precipitated.
Here then we have the most conclusive evidence that Buchner's
yeast extract contains an ertzyme which is the cause of alcoholic
fermentation, and as with other enzymes it has not been found
possible to obtain zymase in a state of purity, no attempt has
been made to ascertain its true chemical composition.
PART IV.
INDICATORS USED IN ALKALIMETRY.
LITMUS SOLUTION AND PAPERS.
1. Litmus Solution. It is customary, in testing both acids
and alkalies, to employ a solution or papers of litmus. The
solution may be prepared as follows :
Weigh about 10 grams of solid litmus, reduce to powder, and
boil with alcohol of about 80 per cent. Let stand for some time,
then pour off the alcohol, it being no longer required for the
preparation. Colouring matter, which is a hindrance to the proper
reaction, is thus removed. Now digest the litmus repeatedly with
cold distilled water till all soluble colour is extracted, let the
mixed washings settle clear, decant, and add to them a few drops
of concentrated sulphuric acid until quite red, then heat to
boiling ; this will decompose the alkaline carbonates and convert
them into sulphates. Now cautiously add baryta water until the
colour is restored to blue or violet, let the baric sulphate settle
perfectly, and decant into a bottle for use. Litmus solution so
prepared is very sensitive to dilute acids and alkalies ; with the
slightest excess of oxalic, sulphuric, hydrochloric, or nitric acids it
gives a pink-red, and with caustic soda or potash, a blue colour;
with ammonia or the bicarbonated alkalies it retains its violet
colour, and the same with most of the neutral salts of the weak
acids, such as sodium or ammonium acetate or borax. Free
carbonic acid interferes considerably with the production of the
blue colour, and its interference in titrating acid solutions with
alkaline carbonates can only be got rid of by boiling the liquid
during the operation, in order to displace the gas from the
ammonia. If this is not done, it is easy to overstep the exact
point of neutrality in endeavouring to produce the blue colour.
124
INDICATORS USED IN ALKALIMETRY 125
The same difficulty is also found in obtaining the pink red when
acids are used for titrating alkaline carbonates, hence the great
value of the caustic alkaline solutions free from carbonic acid in
acidimetry.
Litmus papers are simply made by dipping strips of unglazed
paper in the solution and drying them ; if required red, the liquid
is slightly acidified.
Neither the solution nor papers should be used by gaslight, nor,
as stated, for testing any solution containing free C0 2 .
2. Methyl-orange (a salt of sulpho-benzene-azo-dimethyl-
amine).
Solution. One gram in a litre of distilled water.
Used for titrating mineral acids in the cold : very useful for
ammonia and its salts. Inapplicable for hot liquids and organic
acids.
Special Properties. Its indifference to C0 2 and SH 2 in the
cold.
Colour Reaction. Pink, with excess of acids. Faint yellow, with
excess of alkali.
3. Phenol-phthalein (C 20 H H 4 ).
Solution. One gram in a litre of 50 per cent, alcohol.
Used for determining caustic fixed alkalies in presence of the
carbonates. Gives no colour with the bicarbonates. Absolutely
useless for the titration of free ammonia and its compounds, or
for the fixed alkalies when salts of ammonia are present.
Special Properties. Unlike methyl-orange, this indicator is
specially useful in titrating all varieties of organic acids oxalic,
acetic, citric, tartaric, etc.
Colour Reaction. Purple-red in alkaline solutions, rendered
colourless by excess of acid.
4. Cochineal Solution.
Solution. Digest one part of powdered cochineal with ten parts
of 25 per cent, alcohol.
This indicator is not very much modified in colour by C0 2 , and
can be used by gaslight. Most useful in titrating solutions of
the alkalies and alkaline earths. Inapplicable in presence of Fe
or Al compounds or acetates.
Colour Reaction. Yellowish-red turned violet by alkalies :
mineral acids restore the original colour.
5. Phenacetolin.
Solution. Two grams in a litre of alcohol.
Special Uses. To estimate KHO or NaHO in the presence of
K 2 C0 3 or Na 2 C0 3 , or CaO in the presence of CaC0 3 .
126 THE BKEWER'S ANALYST
Colour Reaction.
With NH 3 and normal alkaline carbonates dark pink.
,, bicarbonates intense pink.
mineral acids golden-yellow.
6. Rosolic Acid (C 20 H 16 3 ).
Solution. Two grams in a litre of 50 per cent, alcohol. This
indicator is excellent for use with all the mineral acids, but
unreliable for the organic acids.
Colour Reaction. Pale yellow, unaffected by acids, turned
violet-red by alkalies.
7. Iodine Solution. One gram iodine and 1 gram potassic
iodide in a litre of distilled water; or 1 per cent, solution of
decinormal iodine.
Used for detecting starch in mashes, worts, etc., in the cold ;
inapplicable for hot liquids.
Colour Reaction. Blue or violet with starch, reddish-brown with
erythro dextrins.
8. Ferrous Thiocyanate Solution. One gram of ferrous
ammonium sulphate and the same quantity of ammonium thio-
cyanate are dissolved in 10 c.c. of distilled water at a temperature
of about 120 F. (49 C.) and immediately cooled ; 5 c.c. con-
centrated hydrochloric acid are then added. The solution so
obtained has invariably a brownish -red colour, due to the presence
of ferric salt, which latter must be reduced. For this purpose
zinc dust is the most satisfactory reagent to employ, and a mere
trace is sufficient to decolorise the solution if pure reagents have
been employed.
When kept for some hours, the indicator develops the red
coloration by atmospheric oxidation.' It may, however, be
decolorised by the addition of a further quantity of zinc dust,
but its delicacy is decreased after it has been decolorised several
times. For practical purposes the indicator may be too delicate,
and it is therefore best to prepare it the day before it is required
for use, as it gives the best results after the second decolorisation.
The indicator is employed for ascertaining the reduction of the
copper in Fehling's test.
PART V.
PREPARATION OF STANDARD AND OTHER
SOLUTIONS.
STANDARD SOLUTIONS.
WHEN analysis by measure first came into use, the test solutions
were generally prepared so that each substance to be tested had
its own special reagent, and the strength of the standard solution
was so calculated as to give the result in percentages. Con-
sequently, in alkalimetry a distinct standard acid was used for
soda, another for potash, a third for ammonia, and so on, necessi-
tating a great variety of standard solutions.
Griffin and Ure were the first, however, to suggest the use of
standard test solutions based on the atomic system, and, following
in their steps, Mohr l worked out and verified many methods of
analysis, which are of great value to all who concern themselves
with scientific and especially technical chemistry.
Normal solutions as a general rule are prepared so that 1
litre at 60 F. (15'5 C.) shall contain the hydrogen equivalent
of the active reagent weighed in grams (H = l). Decinormal
solutions are made one-tenth, and centinormal one-hundredth of
N N
this strength, and may be shortly designated as and -
10 100
solutions.
In the case of univalent substances such as silver, iodine,
hydrochloric acid, sodium, etc., the equivalent and the atomic
(or, in the case of salts, molecular) weights are identical ' f thus a
normal solution of hydrochloric acid must contain 36-5 grams
of the acid in a litre of fluid, and sodic hydrate 40 grams.
Jn the case of bivalent substances such as lead, calcium, oxalic
acid, sulphurous acid, carbonates, etc., the equivalent is one-half
1 Lehrbuch der Chemisch Analytischen Titrirmethode.
128 THE BREWER'S ANALYST
of the atomic (or, in the case of salts, molecular) weight ; thus a
normal solution of oxalic acid would be made by dissolving 63
grams of the crystallised acid in distilled water, and diluting the
liquid to the measure of 1 litre.
Further, in the case of trivalent substances such as phosphoric
acid, a normal solution of sodic phosphate would be made by
358
weighing -g-,119'3 grams of the salt, dissolving in distilled
water, and diluting to the measure of 1 litre.
One important point, however, must not be lost sight of,
namely, that in preparing solutions for volumetric analysis the
value of a reagent as expressed by its equivalent hydrogen-weight
must not always be regarded, but rather its particular reaction in
any given analysis; for instance, with a solution of potassic
permanganate MnK0 4 , when used as an oxidising agent, it is the
available oxygen which has to be taken into account, and hence
in constructing a normal solution one-fifth of its molecular weight,
- = 31 '6 grams, must be contained in the litre.
Illustrations may be given in order to show the method of
calculating the results of this kind of analysis :
1. Suppose, for instance, that it is desired to know the quantity
of pure silver contained in a shilling. The coin is first dissolved
in nitric acid, by which means a bluish solution, containing silver,
copper, and probably other metals, is obtained. It is a known
fact that chlorine combines with silver in the presence of other
metals to form chloride of silver, which is insoluble in nitric acid.
The proportions in which the combination takes place are 35'5
of chlorine to every 108 of silver; consequently, if a standard
solution of pure chloride of sodium is prepared by dissolving in
distilled water such a weight of the salt as will be equivalent to
35*5 grams of chlorine ( = 58'5 grams NaCl) and diluting to the
measure of 1 litre (1000 c.c.), such a solution will be a normal
one, and every single gram measure of this solution will combine
with 0*108 gram of pure silver to form chloride of silver, which
is precipitated to the bottom of the vessel in which the mixture
is made. In the process of adding the salt solution to the silver
drop by drop (titrating), a point is at last reached when the
precipitate ceases to form. Here the process is stopped.
On looking carefully at the graduated burette from which the
standard solution has been used, the operator sees at once the
number of c.c.'s which have been necessary to produce the com-
plete decomposition. For example, suppose the reading, that is
PREPAKATION OF STANDARD AND OTHER SOLUTIONS 129
to say, the number of c.c.'s used, equalled 33 7, all that is
necessary to be done is to multiply 33*7 by the coefficient for
each c.c., viz., 0*108, which shows the amount of pure silver
present to be 3*63 grams.-
Inversely, it is obvious that one may similarly test a substance
for the quantity of chlorine by titrating a dissolved and measured
quantity with a standard solution of silver.
N
2. Each c.c. of silver solution will contain T o\J-<nr of the
atomic weight of silver = 0*0108 gram, and will exactly precipitate
"nr.FinF f tne atomic weight of chlorine = 0*00355 gram from any
solution of a chloride.
3. In the case of normal oxalic acid each c.c. will contain ^^
of the molecular weight of the acid = 0*063 gram, and will
neutralise ^-^^ of the molecular weight of sodic carbonate =
0'053 gram, or will combine with -g-irW f ^ ne atomic weight of
a dyad metal such as lead = 0'1 035 gram, or will exactly saturate
TWO u" ol? * ne molecular weight of sodic hydrate = 0*040 gram, and
so on.
The great convenience of this equivalent system is, that the
numbers used as coefficients for calculation in any analysis are
familiar, and the solutions agree with each other, volume for
volume.
We have hitherto looked only at one side of its advantages.
For technical purposes, the plan allows the use of all solutions of
systematic strength, and simply varies the amount of substance
tested according to its equivalent weight.
Thus the normal solutions, say, are
Sulphuric acid . . . .49 grams per litre
Nitric acid .... 63 ,, ,,
Oxalic acid . . 63 ,, ,,
Hydrochloric acid . . . 36*5 ,, ,,
Sodic hydrate .... 40 ,, ,,
Sodic carbonate .... 53 ,,
100 c.c. of any one of the normal acids should exactly neutralise
100 c.c. of any of the normal alkalies, or the corresponding
amount of pure substance which the 100 c.c. contain.
It is obvious that no experiment, however carefully performed,
can be accurate unless the chemical reagents are pure and of
the proper strength. It is also obvious that even if these con-
ditions apply, proper quantities cannot be weighed without the
balance is in perfect order, and that all burettes, pipettes, and
9
130 THE BREWER'S ANALYST
measuring flasks are perfectly graduated. It is therefore highly
essential that these conditions should be carefully looked to, and
particularly that burettes, pipettes, and measuring flasks be
standardised, and re-marked with a file if practicable, or other-
wise rejected and perfect ones obtained.
In the making up of all standard solutions a further essential
is that the distilled water in use be perfectly pure and in most
instances particularly free from ammonia.
We may now proceed to a consideration of the
PREPARATION OF STANDARD AND OTHER SOLUTIONS.
To begin with, volumetric solutions may be divided into two
groups :
(a) Permanent solutions, e.g., of sodium chloride, hydrochloric
acid, and oxalic acid, which may be accurately prepared, and will
keep well if properly stored. These may be regarded as true
standards with which other solutions may be compared. If there
be a doubt as to the exact strength of the standard, it is better,
as a rule, to check it against a known weight of a suitable re-
agent rather than by some other standard solution.
(b) Non-permanent solutions, such as ferrous salts and dilute
thiosulphate. With such it is a waste of time to aim at getting
some definite strength. An approximation will suffice, the exact
litre being determined each time of use by trial against some
permanent standard, or a known weight of some reagent.
NORMAL SULPHURIC ACID
= 49 grams H 2 S0 4 per litre
1 c.c. = 0-049 gram H 2 S0 4
0-048 S0 4
0-040 S0 3
0-090 albumin
O'OIT ,, ammonia
0*014 ., nitrogen.
Run about 30 c.c. pure sulphuric acid, specific gravity 1-84, into
a litre flask about a quarter full of distilled water ; cool and make
to mark at 60 F. (15*5 C.) with distilled water.
If the acid from which the solution has been made was of the
specific gravity mentioned, the solution will be too strong, which
is preferable, on account of the ease by which, in preference to a
weak solution, it can be rendered accurate.
PREPARATION OF STANDARD AND OTHER SOLUTIONS 131
To test its strength several methods may be employed, the
best being perhaps as follows :
Weigh 2 grams of pure anhydrous sodic carbonate recently
heated and cooled under "a desiccator and place in a tared
platinum dish. Dissolve in a small quantity of distilled water,
covering the dish with a watch glass. Temporarily remove the
watch glass and run in exactly 25 c.c. of the sulphuric acid to
be standardised and immediately replace the watch glass. When
the effervescence at first occurring has ceased, place the dish on
the water bath and evaporate the contents to complete dryness,
previously rinsing in any drops of liquid which may have collected
on the inner surface of the watch glass. Now heat to 350 F.
(176 '6 C.) in an air bath, cool under desiccator, and weigh, re
peating this until the weight is constant.
From this the exact strength of the made solution may easily
be calculated.
The CO 2 in the sodic carbonate has been displaced by S0 3 ,
and, as the atomic weight of the former is 44 as against 80 for
the latter, it is evident that the increased weight of the residue
over that of the sodic carbonate originally taken is proportional
to the amount of sulphuric acid employed, provided an excess
of the salt named be present and the quantity recommended
ensures this being so.
Example :
Platinum dish and Na 2 C0 3 = 68*904 grams.
Platinum dish = 66*808
2-096
25 c.c. of the sulphuric acid of approximately normal strength
were run in, and the whole evaporated to dryness, heated to
350 F. (176'6C.) for some time, cooled under a desiccator arid
weighed. The dish and contents now weighed 69*382 grams,
an increase of 0'478 grams. This increased weight is in pro-
portion to the difference between the atomic weights of C0 2
and S0 3 , that is, 44C0 2 will be replaced by 80S0 3 , or the presence
of 80 parts S0 3 will give an increased weight of 36. Therefore
36 : 80 : : 0'478 : 1'062 grams of S0 3 in 25 c.c. of dilute acid, or
4 '248 grams per 100 c.c. in place of 4*00, the correct quantity.
We therefore now dilute this as follows :
4-00 : 100 : : 4-248 : 1-062.
That is, each 100 c.c. must be diluted to 106-2 to make it of
correct strength.
132 THE BREWER'S ANALYST
The accuracy of this may be verified by making another ex-
periment with the dilute liquid, either by evaporation with sodic
carbonate as before, or as follows :
Run 10 c.c. normal alkali into a small beaker or flask, add a
few drops of litmus or methyl-orange, and allow the acid to flow
from a 10 c.c. pipette, divided into -^ c.c., until the point of
neutrality is reached. If more than 10 c.c. are required, the acid
is too weak ; if less, too strong.
Suppose it required 8*9 c.c. to saturate the 10 c.c. of alkali.
890 c.c. will be required to make 1 litre of standard acid ;
remove, therefore, the excess from the litre flask and dilute to
mark. Now test again with the pipette, and if the previous
examination was correct, 10 c.c. of each solution should exactly
neutralise each other.
As a further check upon the accurate strength of the solution,
it is advisable to use larger quantities, say 50 or 100 c.c., for the
final adjustment. The solution may also be controlled by pre-
cipitation with baric chloride, in which case 10 c.c. should
produce as much baric sulphate as is equal to 0*49 gram of
sulphuric acid, or 49 grams per litre.
NORMAL NITRIC ACID
= 63 grams HN0 3 per litre
1 c.c. = 0-063 gram HN0 3
0-062 N0 3
0-054 N 2 5 .
Nitric acid used for making the normal solution should be
colourless, free from chlorine and nitrous acid, and of a specific
gravity of from 1*35 to 1'40. If the acid is coloured from the
presence of nitrous acid, it should be mixed with an equal volume
of distilled water and boiled until colourless. When cold it may
be diluted and titrated against pure sodic carbonate, as described,
with normal sulphuric acid.
/N
NORMAL OXALIC ACID (
= 63 grams H 2 C 2 4 , 20H 2 per litre
1 c.c. = 0-063 gram H 2 C 2 4 , 20H 2
0-045 H 2 C 2 4 .
This solution possesses the advantage that it may be established
directly, by weighing 63 grams of the pure crystallised acid,
PREPARATION OF STANDARD AND OTHER SOLUTIONS 133
dissolving the same in distilled water and making to the bulk
of 1 litre at 60 F. (15'5 C.). The acid should be recrystallised,
thoroughly air-dried, but not in the slightest degree effloresced.
The solution keeps well, and will bear heating without volatilising
the acid. The solution should be titrated against a normal
solution of sodic carbonate.
/N
NORMAL HYDROCHLORIC ACID f
= 36"5 grams HCL per litre
1 c.c. = 0-0365 gram HCL
0-0355 Cl.
About 181 grams of pure hydrochlorlic acid (sp. gr. 1*10) made
up to 1 litre at 60 F. (15-5 C.) with distilled water. The solution
should be titrated against normal alkali.
NORMAL ALKALI.
Normal alkali may consist of either soda, potash, or (less
recommendable) ammonia.
As pure sodic hydrate, manufactured from metallic sodium and
free from carbonic acid, is readily obtainable, the standard solution
is made from it as follows :
CN\
- )
= 40 grams NaHO per litre
1 c.c. = 0-040 gram NaHO
0-031 ., Na 2
0-06 ,, acetic acid
0-09 lactic acid.
Dissolve about 42 grams sodic hydrate in about 800 c.c.
distilled water, cool to 60 F. (15 '5 C.). Titrate a portion of this
solution with normal acid, calculate therefrom its exact strength
and the dilution necessary to reduce it to 40 grams of actual
NaHO per litre.
NORMAL SODIC CARBONATE (
= 53 grams Na 2 C0 3 per litre
1 c.c. =0-053 gram Na 2 C0 3
0-030 C0 3
0-022 C0 2 .
134 THE BREWER'S ANALYST
Dissolve 53 grams of pure and dry sodic carbonate in distilled
water and dilute to 1 litre at 60 F. (15'5 C.). The solution should
be titrated against normal hydrochloric acid.
DECINORMAL ACID OR ALKALI (
Run 100 c.c. normal acid or normal alkali into a litre flask
about quarter full of distilled water, cool, and make to mark at
60 F. (15'5 C.) with distilled water.
FOUR-TIMES NORMAL ACID OR ALKALI
Take 400 c.c. of strong hydrochloric acid and make up at 60 F.
(15-5 C.) with distilled water to 1 litre. The solution may be
titrated against normal alkali and appropriately diluted; each
c.c. of the corrected standard should require 4 c.c. of normal
alkali.
The corresponding four-times normal alkali is made by dissolving
about 170 grams of sodic hydrate in distilled water, cooling, and
making up to 1 litre. The solution may be titrated against four-
times normal acid.
The acid solution is generally employed for inverting cane-
sugar, and the corresponding alkali for neutralising the acidity
after inversion. The solutions, however, need not be of exact
strength.
DECINORMAL POTASSIC PERMANGANATE
/NX
VioJ
= 3*156 grams MnK0 4 per litre
1 c.c. = 0-0056 Fe
0-0072 FeO
0-0080 Fe 2 3
0-0017 H 2 S
0-0056 CaO.
Weigh 3*156 grams pure crystal potassic permanganate and
dissolve with a little distilled water (free from ammonia) in a litre
flask and make to mark at 60 F. (15 '5 C.). In standardising the
solution it should react with its own volume of oxalic acid.
The solution should be kept in a well-stoppered bottle, and
while it is quite free from sediment, it may be taken for granted
PREPARATION OF STANDARD AND OTHER SOLUTIONS 135
that its strength is unaltered. It will retain its strength for
several months.
DECINORMAL IODINE
'H\
aoy
= 12 '7 grams I per litre
1 c.c. = 0-0032 gram S0 2 .
Chemically pure iodine may be obtained by mixing commercial
iodine with about one-fourth of its weight of potassic iodide and
gently heating the mixture between two large watch glasses or
porcelain capsules, the lower one being placed upon a heated iron
plate, when the iodine sublimes in brilliant crystals which are
absolutely pure.
The resublimed iodine of commerce is not always free from
chlorine, and, unless purchased absolutely pure, it becomes
necessary to prepare it by a second sublimation as described.
The watch glass or capsule containing the iodine is then placed
under the desiccator so that the iodine may be cooled and freed
from traces of moisture; then 12'7 grams are weighed and,
together with about 18 grams of pure white potassic iodide,
dissolved in about 250 c.c. distilled water.
The solution is then transferred to a litre flask, and made to
mark at 60 F. (15'5 C.) with distilled water. The flask should not
be heated in order to promote solution, and care should be taken
that iodine vapours are not lost during the operation. The solution
N
should be titrated against potassic permanganate :
Take 10 c.c. of the permanganate, dilute with distilled water,
acidify with sulphuric acid. Add potassic iodide, and titrate with
N N
sodic thiosulphate. Then titrate 10 c.c. of the iodine with
the same thiosulphate solution. The volume consumed should
be the same as in the previous titration.
(N
= 24'8 grams Na 2 S 2 3 , 50H 2 per litre
1 c.c. = 0-01 265 gram I.
As it is not difficult either to manufacture or procure pure
sodic thiosulphate, a portion is taken, powdered, and dried between
blotting paper and 24'S grams weighed. This quantity is then
136 THE BREWER'S ANALYST
dissolved in a little distilled water, transferred to a litre flask, and
made to mark at 60 F. (15*5 C.) with distilled water. .
The solution should be titrated with decmormal iodine solution,
using a little gelatinised starch as an indicator. It should
N
correspond, volume for volume, with iodine solution.
The solution is prone to decompose, depositing sulphur, especially
if not kept in the dark. This tendency may be obviated, according
to Mohr, by adding about 2 grams sesquicarbonate of ammonia.
O'Shaughnessy states that the addition of a little salicylic acid
entirely prevents the solution decomposing.
DECINORMAL SODIC CHLORIDE ( J
= 5'85 grams NaCl per litre
1 c.c. = 0-003537 gram Cl
0-005837 NaCl.
5'85 grams of pure sodic chloride dissolved in distilled water and
made up to 1 litre at 60 F. (15'5 C.).
POTASSIC NITRATE.
1-011 gram KN0 3 per litre
1 c.c. = 0'14 milligram N.
Dissolve 1*011 gram pure potassic nitrate and make to 1 litre
at 60 F. (15-5 C.) with distilled water.
There is no simple volumetric method for checking this solution.
If iu doubt, make up a fresh one, as this will involve less time
than the exact titration of the old solution.
INDIGO SOLUTION.
1 c.c. = 0-0001 gram N
0-000386 N 2 5 .
Weigh 4 grams pure soluble indigo carmine in a small beaker ;
mix in a few drops of cold distilled water to form a paste, and
then add 4 c.c. of strong sulphuric acid. Cover the beaker and
allow to stand all night. Dilute with water, thoroughly mix, and
make up at 60 F. (15'5 C.) to 1 litre.
The solution keeps for a lengthy period, but should be
standardised against a standard solution of potassic nitrate (TO 11
PREPAKATION OF STANDARD AND OTHER SOLUTIONS 137
gram of the crystallised salt in 1 litre of distilled water). 5 c.c.
of the nitrate solution is diluted to 50 c.c. with distilled water,
sulphuric acid run in, and titration performed with the indigo as
described under Water Analysis. 5 c.c. of the nitrate solution
should require exactly 7 c.c. of the indigo.
Indigo solution to be used for tannin estimations need not be
of exact strength.
ARGENTIC NITRATE.
4 '79 grams AgN0 3 per litre
1 c.c. -0-001 gram Cl
0-00165 NaCL.
Dissolve 4'79 grams pure recrystallised argentic nitrate in a
little distilled water, transfer to a litre flask, and make to mark at
60 F. (15-5 C.) with distilled water.
N
The solution should be titrated against sodic chloride, using
potassic chromate as indicator.
A decinormal solution may be prepared, if required, by
dissolving 17 grams of the silver nitrate and diluting to 1 litre.
Each c.c. will then equal 0'010766 gram Ag.
0-016966 AgN0 3 .
IRON SOLUTION.
1 c.c =0*1 milligram Fe.
Weigh 0'7 grain ferrous-ammonia sulphate, transfer to a boiling
flask, dissolve in about 300 c.c. of distilled water, add about 5
drops nitric acid, and boil for about 10 minutes in order to oxidise
the iron. Cool the solution, transfer to a litre flask, wash in the
rinsings from the boiling flask, and make to mark at 60 F.
(15-5 C.) with distilled water.
The formula of the ferrous-ammonia sulphate is Fe(NH 4 ) 2
(S0 4 ) 2 60H 2 = 392. Consequently, it contains exactly one-
seventh of its weight of iron; 0*7 gram therefore represents
O'l gram of iron, and this is a convenient quantity to weigh
for the purpose of titrating permanganate solution hereafter
referred to.
The solution is not permanent, and should be titrated before
use. When freshly prepared, 100 c.c. of it should require 5 -35
c.c. of permanganate.
30
138 THE BREWER'S ANALYST
THIRTIETH NORMAL POTASSIC PERMANGANATE ( ).
\30/
1 c.c. = '001385 tannic acid.
Add 333*3 c.c. decinormal potassic permanganate to a litre
flask and make to mark at 60 F. (15'5 C.) with distilled water
free from ammonia.
The solution should be titrated against oxalic acid, 30 c.c.
N
requiring 10 c.c. oxalic.
SODIC THIOSULPHATE FOR FORSCHAMMER'S OXYGEN PROCESS.
Weigh 2 grams pure recrystallised sodic thiosulphate, transfer
to a litre flask, dissolve in a little distilled water, and make to
mark at 60 F. (15'5 C.) with distilled water.
N
The solution may be titrated against iodine.
POTASSIC IODIDE FOR FORSCHAMMER'S OXYGEN PROCESS.
Weigh 100 grams pure potassic iodide, dissolve in a little
distilled water, transfer to a litre flask and make to mark at
60 F. (15'5 C.) with distilled water free from ammonia. The
solution is not required to be very exact ; it may be titrated,
however (in the same way as a chloride), with silver nitrate, using
potassic chromate as indicator : 5 c.c. of iodide should equal 30*1
N
c.c. silver solution.
POTASSIC PERMANGANATE FOR FORSCHAMMER'S OXYGEN PROCESS.
1 c.c. = '0001 gram available oxygen.
Dissolve 0'395 gram pure dry potassic permanganate and make
to a litre at 60 F. (15*5 C.) with distilled water free from
ammonia.
N N
The solution may be titrated against oxalic acid : 5 c.c.
oxalic requires 40 c.c. permanganate.
So long as the solution is quite free from sediment, it may be
taken for granted that its strength is unaltered.
STANDARD AMMONIA.
Dissolve 3*15 grams ammonic chloride and make to 1 litre at
60 F. (15*5 C.) with distilled water free from ammonia.
PEEPARATION OF STANDARD AND OTHER SOLUTIONS 139
The solution should be titrated against the silver nitrate
solution previously described (4*79 grams AgN0 3 per litre), 10
c.c. requiring 20*9 c.c. of the silver solution.
DILUTE STANDARD AMMONIA.
1 c.c. = '01 milligram NH 3 .
Take 10 c.c. of the standard ammonia solution previously
described and dilute to 1 litre with distilled water at 60 F.
(15-5 C.).
The solution should be freshly prepared at least once a month.
NESSLER'S SOLUTION.
Dissolve 62-5 grams potassic iodide in about 250 c.c. distilled
water, set aside a few c.c., and add gradually to the larger part a
cold, saturated solution of corrosive sublimate until the iodide of
mercury precipitated ceases to be redissolved on stirring. When
a permanent precipitate is obtained, restore the reserved potassic
iodide so as to redissolve it, and continue adding corrosive
sublimate gradually until a slight precipitate remains undissolved.
(The small quantity of potassic iodide is set aside merely to
enable the mixture to be made rapidly without danger of adding
an excess of corrosive sublimate.)
Next dissolve 150 grams potassic hydrate in 150 c.c. distilled
water, allow the solution to cool, add it gradually to the above
solution, and make up with distilled water to 1 litre.
On standing, a brown precipitate is deposited, and the solution
becomes clear and of a pale, greenish-yellow colour. It is ready
for use as soon as it is perfectly clear, and should be decanted into
a bottle as required.
WATER FREE FROM AMMONIA.
When determining the amount of free or saline ammonia in a
water, the sample is distilled which causes the free or saline
ammonia, if present, to come off with the distillate. For this
reason distilled water usually contains a considerable quantity of
free ammonia and should therefore be tested before use. Unless
free, it is useless to employ it for making up standard ammonia
solutions or for Nesslerising purposes. If a good tap- water is at
hand, showing no reaction of ammonia, it may be employed for
Nesslerising, but failing the possession of such a water, it becomes
140 THE BREWER'S ANALYST
necessary to prepare distilled water free from ammonia ; whilst
owing to tap- water containing, as a rule, large quantities of saline
bodies, it should not, even if free from ammonia, be employed for
making up standard solutions.
It is an easy matter to expel the free ammonia from distilled
water by vigorously boiling it in a capacious flask for about 30
minutes ; the water being afterwards cooled and transferred to a
bottle ready for use.
On the other hand, ordinary tap-water may be distilled rejecting
the distillate so long as any colour is produced by Nessler's re-
agent ; or the water in the retort may be acidulated with pure
sulphuric acid, when the whole distillate will be free from ammonia
and in all other respects pure.
ALKALINE POTASSIC PERMANGANATE.
Dissolve 200 grams potassic hydrate and 8 grams crystallised
potassic permanganate with 800 c.c. distilled water in a large
porcelain dish and evaporate over water-bath almost to dryness.
This effectually expels all traces of ammonia. Cool, transfer to
a litre flask, and make to mark at 60 F. (15'5 C.) with distilled
water free from ammonia.
AMMONIA MOLYBDATE SOLUTION.
Dissolve 4 grams molybdenum trioxide (Mo0 3 ) in 94 c.c.
ammonia (sp. gr. 0'880) and 150 c.c. distilled water; filter into
694 c.c. strong nitric acid (sp. gr. 1*2), dilute to a litre with a
1 2 per cent, solution of nitric acid ; stand about 1 2 hours at
122 F. (50 C.) and then filter through three folded papers and
bottle.
MAGNESIA MIXTURE.
Dissolve one part of crystallised magnesic sulphate and two
parts ammonic chloride in eight parts of distilled water and four
parts strong ammonia.
Allow the mixture to stand for several days and then filter and
bottle.
FEHLING'S SOLUTION.
Volumetric.
50 c.c. = '24 gram dextrose.
25 invert.
40 maltose.
PREPARATION OF STANDARD AND OTHER SOLUTIONS 141
Gravimetric.
I gram CuO = '4535 dextrose.
'4715 invert.
7435 maltose.
The solution consists of copper sulphate, potassic sodic tartrate
(Rochelle salt), and sodic hydrate, and it was formerly customary
to make and keep the solution in one bottle ready for use. It
was found, however, that the mixed solution would not keep, but
that under certain conditions, namely, provided the copper
sulphate is made up as a separate solution and slightly acidified,
it will keep sound for an almost indefinite period, whilst the
alkaline solution kept separately will also keep for a lengthy
period. The latter solution is not, however, so permanent as the
copper sulphate, but as it need not be of accurate strength, it
becomes an easy matter to prepare fresh solutions from time to
time.
Two solutions are therefore now employed, viz., copper
sulphate solution and alkaline tartrate, and are prepared as
follows :
Copper Sulphate Solution. About 70 grams of crystallised
copper sulphate are powdered and pressed between blotting paper;
69-28 grams are then carefully weighed and dissolved in about
400 c.c. distilled water, about 4 c.c. concentrated sulphuric acid
then added, and the solution made to 1 litre at 60 F. (15'5 C.)
with distilled water.
The solution should be standardised as hereafter described.
Alkaline Tartrate Solution. 346 grams of Rochelle salt
and 130 grams of caustic soda are dissolved in about 800 c.c.
distilled water, cooled, and made to 1 litre at 60 F. (15-5 C.)
with distilled water. The solution should then be allowed to
stand for 24 hours, and be afterwards filtered through a funnel
containing a plug of glass wool.
Standardisation. Volumetric. It is necessary to first
prepare a standard solution of invert-sugar as follows :
The purest variety of cane-sugar is that known as coffee-sugar,
which generally contains from 99 to 99-8 per cent, of absolute
sugar. The large crystals of this sugar should be selected, and
after examining a solution in the polarimeter or determining the
moisture percentage by drying a portion in the water oven,
2 grams of actual sugar should be weighed, that is, making
allowance for the amount of moisture.
The 2 grams of actual sugar are now placed in a 200 c.c.
142 THE BREWER'S ANALYST
4.
flask, 50 c.c. of distilled water and 5 c.c. of hydrochloric acid
added, and the whole maintained at a temperature of 150 F.
(65*5 C.) on the water bath for 20 minutes. By this time the
sugar will have been inverted to dextrose or invert-sugar ; the
flask is then cooled and the solution neutralised by the addition
4.
of 5 c.c. alkali, the bulk being afterwards made up to 200 c.c.
at 60 F. (15-5 C.) and a Fehling's test performed with some of
the sugar solution in order to determine the quantity of Fehling's
required. Having determined this, and knowing by calculation
what quantity correct Fehling's should require, we may ascertain
the dilution necessary to bring the copper sulphate solution to the
proper strength.
Example. The coffee-sugar taken was found by the polari-
meter to contain 99 "6 per cent, of real cane sugar; 2 grams of
sugar were required, so 99'6 : 100 : : 2 : 2'OOS. 2-008 grams of
the sugar were weighed and inverted with 5 c.c. acid,
N
4.
neutralised with 5 c.c. alkali and diluted to 200 c.c. Every
95 parts of cane-sugar on inversion become 100 parts of invert,
hence 95 : 100 : : 2 : 2*10 grams invert-sugar in 200 c.c. and
2-10-^2 = 1-05 in 100 c.c.
If 100 c.c. contain 1*05 gram of invert-sugar, how many c.c.
will contain *25 gram? the quantity corresponding to 50 c.c.
Fehling's.
1-05 : 100 : : -25 : 23-8.
Therefore 23*8 c.c. of the sugar solution are required to reduce
50 c.c. Fehling's.
We now conduct a Fehling's test in order to ascertain if this
is so or what the actual strength of the Fehling's is. To do this
it should be remembered that the sugar solution experimented
with should not contain more than 1 per cent, of sugar. In our
example it will be noted that 2 grams of sugar diluted to 200
c.c. equals a 1 per cent, solution, so that the sugar solution is not
above the maximum concentration for a Fehling's test. We
therefore take 200 c.c. of distilled water in a boiling flask of about
800 c.c. capacity and boil. When well boiled, 50 c.c. Fehling's
solution are added, that is, 25 c.c. of the standard copper solution
and 25 c.c. of the alkaline tartrate.
The contents of the flask are again raised to the boiling-point,
and 10 c.c. of the 1 per cent, sugar solution are run in from a
PREPARATION OF STANDARD AND OTHER SOLUTIONS 143
graduated burette. The whole is again boiled for about two
minutes, and further quantities of the sugar solution are added
at the rate of 5 c.c. at a time, the boiling being continued after
each addition until a bright red colour, due to the formation of
cuprous oxide (CuO), is obtained. The flask is now removed and
set aside for the precipitate to settle. If the flask is now held to
the daylight, the colour may readily be seen ; should any blue
tinge remain, more sugar solution, 1 c.c. at a time, is added, and
the boiling recommenced and continued until the blue colour
just disappears. To test whether the reduction of the copper is
complete, a little of the solution is withdrawn by a glass rod
and brought at once in contact with a drop of ferrous thiocyanate
on a porcelain or opal glass slab.
It is always advisable to test before it is thought that the
Fehling's is quite completed, as it is impossible to tell how much
it is overdone, but absolutely easy to ascertain the incompletion.
If it has been overdone, it is necessary to repeat the estimation
over again with fresh Fehling's and further quantities of the
sugar solution. It is almost impossible to hit the exact point
on the first trial, but it affords a very good guide for a
more exact titration the second time, and a second titration
should always be made. When the titration is once com-
menced it should be carried on as quickly as possible, in order
to prevent irregularities from long exposure of the hot solution
to the atmosphere.
The reduction being complete, the number of c.c. of sugar
solution used is read off from the burette. Let us assume
we have used 31*4 c.c. sugar solution. We have seen from
the calculation that 23'8 c.c. of the invert-sugar solution
should reduce 50 c.c. Fehling's ; but it is here found that
31 '4 c.c. were required, so that the Fehling's solution is too
strong.
What factor does 31 '4 c.c. correspond to?
23-8 : -25 : : 31'4 : '320.
Therefore each 50 c.c. of Fehling's, or 25 c.c. of copper solution,
equal '320 invert-sugar instead of *25.
How many c.c. of correct standard copper solution should
represent -320 grams ?
If 25 c.c. equal '25, how many c.c. does '320 equal 1
25 : 25 : : -320 : 32'0 c.c.
So we have merely to dilute 25 c.c. of our Fehling's solution
144 THE BREWER'S ANALYST
to 32 c.c. to bring it to proper strength, or add to each 25 c.c.
that are left 7 c.c. of distilled water.
For particulars of gravimetric estimation, see p. 213, Malt
Wort Analysis.
SOLUBLE STARCH (DRY).
Take about 1 Ib. purified potato starch, place in a clean
Winchester quart bottle, and add 1000 c.c. of a 7'5 per cent,
solution of hydrochloric acid (75 c.c. hydrochloric acid, specific
gravity 1037-0, and 925 c.c. distilled water). Set aside the
mixture at the room temperature 60-65 F. (15-5 -18'3 C.)
for seven days, stirring daily. 1
At the end of this time wash thoroughly by decantation, at
first with tap-water, and later on with pure distilled water, until
the washings are free from chloride neutral to freshly prepared
litmus paper.
Now collect the starch on a filter paper, place in a Buchner's
funnel, pump as dry as possible, and then spread it out on a new
unglazed porous plate. The starch should now be dried at a
gentle heat 110 F. (43'3 C.), as quickly as possible and then
triturated in a porcelain mortar and rubbed through a fine hair
sieve.
SOLUBLE STARCH SOLUTION FOR LINTNER'S DIASTATIC PROCESS.
The previously prepared dry soluble starch is dissolved in
boiling water at the rate of 2 grams per 100 c.c. of water. The
solution is then cooled to 70 F. (21'1 C.) for use. It should be
perfectly mobile (not gelatinous), indicating perfect conversion
into soluble starch, and show only a negligible reducing action
on Fehling's solution. It should be neutral to litmus solution,
and the distilled water employed for making up the solution
should be absolutely pure.
POTASSIC PERMANGANATE FOR HOP TANNIN PROCESS.
Dissolve 1 gram pure dry potassic permanganate in a little
distilled water and make to 1 litre with distilled water at a
temperature of 60 F. (15'5 C.). The distilled water should be
free from ammonia.
1 According to Brown and Morris (Jnl. Chem. Soc., 1889, 450), if a 12
per cent, solution of hydrochloric acid is employed, 24 hours' digestion
suffices.
PREPARATION OF STANDARD AND OTHER SOLUTIONS 145
The solution may he titrated against decinormal oxalic acid :
N
10 c.c. oxalic should require 31 '6 c.c.
INDIGO SOLUTION FOR HOP TANNIN PROCESS.
Dissolve 5 grams pure indigo carmine in 500 c.c. distilled
water ; add 50 c.c. concentrated sulphuric acid, cool, and make
to 1 litre at 60 F. (15'5 C.) with distilled water. Each c.c. of
this solution should correspond to an equal amount of the
previously prepared potassic permanganate.
GELATINE SOLUTION FOR HOP TANNIN PROCESS.
Weigh 25 grams Nelson's gelatine, place in a beaker, add
250 c.c. distilled water, and set aside for about 6 hours. Now
heat on the water bath until the gelatine is dissolved ; next
saturate with fairly pure sodic chloride and make up to 1 litre
at 60 F. (15'5 C.) with a saturated solution of sodic chloride.
Shake the solution, allow to stand for a few days, warm, and then
filter bright into a bottle ready for use.
BOTTLES (10 PER CENT. SOLUTIONS).
Plumbic acetate. Sodic phosphate.
Baric chloride. ,, carbonate.
,, hydrate. ,, hydrate.
Ammonic chloride. ,, bisulphate.
,, oxalate. Potassic hydrate.
,, carbonate. ,, ferrocyanide.
phosphate. ,, chromate (free from Cl).
,, nitrate. iodide.
Potassic chloride.
Sulphuric acid, dilute (1-3).
Hydrochloric acid, dilute (1-3).
Acetic acid, dilute (1-1).
Ammonic hydrate, dilute (1-3).
10
146
THE BREWER'S ANALYST
TABLE FOR THE SYSTEMATIC ANALYSIS OF ALKALIES, ALKALINE
EARTHS, AND ACIDS.
|
Quantity to be
weighed so that
Substance.
Formula
Atomic
Weight
1 c.c Normal
Solution =
Normal
Factor. 1
1 per cent, of
Substance.
grams.
Ammonia .
NH 3
17
1-7
0-017
Ammonic carbonate
Acetic acid .
(NH 4 ) 2 C0 3
G 2 O 2 H 4
96
60
4-8
6'0
0-048
0-060
Baric hydrate
BaH 2 2
171
8-55
0-0855
,, (crystals)
Ba0 2 H 2 (OH 2 ) 8
315
15-75
0-1575
,, carbonate .
BaC0 3
197
9-85
0-0985
Calcic oxide
CaO
56
2-8
0-028
,, hydrate .
CaH 2 2
74
3-7 -
0-037
,, carbonate .
CaC0 3
100
5-0
0-050
Citric acid .
C 6 7 H 8 + OH 2
210
7-0
0-070
Hydrochloric acid
HCL
36-5
3-65
0-0365
Magnesia
M 9
40
2-00
0-022
Magnesic carbonate
M 9 C0 3
84
4-20
0-042
Nitric acid .
HN0 3
63
6-3
0-063
Oxalic acid .
C 2 4 H 2
126
6-3
0-063
Potash
K 2
94
47
0-047
Potassic hydrate .
KHO
56
5-6
0-056
carbonate
,, bicarbonate .
K 2 C0 3
KHC0 3
138
100
6-9 0-069
10-0 . 0-100
Soda ....
Na^O
62
3-1 0-031
Sodic hydrate
NaHO
40
4-0 0-040
,, carbonate .
, , bicarbonate
Na,C0 3
NaHC0 3
106
84
5-3 0-053
8-4 0-084 -
Sulphuric acid .
H 2 S0 4
98
4-9 i 0-049
Strontia
SrO
103-5
5-175 0-05175
Strontic carbonate
SrC0 3
147-5
7-375 0-07375
Tartaric acid
C 4 6 H 6
150
7-5 0-075
1 This is the coefficient by which the number of c.c. of normal solutions
used in analysis is to be multiplied in order to obtain the amount of pure
substance present in the material examined. See also Multipliers required in
Volumetric Analysis, p. 394.
PART VI.
METHODS OF ANALYSIS.
OF the various chemical preparations offered for sale to brewers,
it is necessary to know how much pure substance they contain.
Let us first take, for instance, the various acids :
SULPHURIC ACID.
Take 10 c.c. of concentrated white sulphuric acid in a tared
crucible and weigh. Suppose the weight is found to be 18*27
grams; then this, divided by 10, gives the specific gravity, viz.
1-827.
In consequence of the great concentration and high specific
gravity of sulphuric acid, it is best to use only 1 or 2 c.c. for
analysis ; hence, after the specific gravity is ascertained, 2 c.c.
may be titrated, taking care that a very fine and accurate
pipette is used for the purpose ; or, if this is not at hand, the acid
may be weighed direct upon the balance.
Suppose we take 2 grams of the above acid in a porcelain dish,
dilute with distilled water, add a few drops of methyl-orange or
litmus solution, and titrate with normal alkali, 37 '2 c.c. of the
alkali being required ; then
37-2 x 0-049 (coefficient table) = 1'822, and
l-822x 1QQ = 91 percent> hydrated acid,
which agrees with Otte's table (p. 401).
HYDROCHLORIC ACID.
Take 5 c.c. of white hydrochloric acid in a tared crucible and
weigh. Suppose the weight to be 5'6 grams; then this, divided
by 5, gives the specific gravity as 1'12.
147
148 THE ETC EWER'S ANALYST
Dilute with distilled water and titrate with normal alkali,
using a few drops of methyl-orange or litmus as indicator.
N
Suppose 37"! c.c. - - alkali are required; this, multiplied by
0-0365 (coefficient table), gives 1'354 grams.
hydrated acid
5*6
Ure's table (p. 402) gives 24"46 per cent, for the same specific
gravity.
In order to ascertain the percentage of hydrochloric acid gas
in any sample, it is only necessary to multiply the weight of gas
found by normal alkali by 100, and divide by the weight of
acid originally taken for analysis : the quotient will be the
percentage. Or, simpler than this, if the ^ equivalent in grams
3"646 grams be weighed, the number of c.c. will be the per-
centage.
NITRIC ACID.
Take 5 c.c. of pure nitric acid and weigh. Suppose the weight
to be 6 '055 grams; this, divided by 5, gives the specific gravity
N
as 1'211. Say the quantity of alkali required to saturate the
5 c.c., using methyl-orange as indicator, is 28'3 c.c. This, multi-
plied by the coefficient factor 0*063, gives 1*782.
1-782x100
6-055
= 29'4 per cent.
ACETIC ACID.
In consequence of the anomaly existing between the specific
gravity of acetic acid and its strength, the hydrometer gives no
uniformly reliable indication of the latter, and consequently the
volumetric method is peculiarly suitable for ascertaining the
value of acetic acid in all its forms. For most purposes normal
caustic alkali may be used as the saturating agent ; but a slight
error occurs in this method, from the fact that neutral acetates
have an alkaline reaction on litmus ; the error, however, is very
small, if care be taken to add the alkali till a distinct blue colour
is reached. As acetic acid is volatile at high temperatures,
normal carbonate of soda must not be used for titrating it, as it
would necessitate heat to expel the carbonic acid.
Five c.c. of acetic acid weighs, say, 5'206 grams -{-5=1-041
specific gravity. The quantity of normal alkali required to
METHODS OF ANALYSIS 149
saturate it is, say, 27'1 c.c.; then this multiplied by 0*06 (co-
efficient) = 1*626 grams.
1-626 x 1QO:
-T206- = 31 ' 2 P
For the ordinary vinegar or turned beer there is no necessity
to take the specific gravity into question : 5 or 10 c.c. may be
taken as 5 or 10 grams. It is advisable to copiously dilute highly
coloured liquids, in order that the change in the colour, produced
by the litmus, may be distinguished ; recourse must also be had
to litmus paper, upon which little streaks should be made from
time to time with the stirring rod.
SULPHUROUS ACID.
N
1 c.c. iodine = 0'0032 gram S0 2 .
N
1 c.c. thiosulphate = 0'01265 gram iodine.
1. Take 20 c.c. of the acid in a 200-c.c. flask and make to
mark at 60 F. (15'5 C.) with recently boiled and cooled distilled
water. Take 10 c.c. of this in a porcelain dish, add a few drops
of freshly prepared gelatinised starch solution, 1 and titrate with
decinormal iodine until a blue colour makes its appearance and
becomes permanent on stirring.
N
Suppose 2 3 '3 c.c. iodine are required to produce the blue
colour. Then 23-3 x -0032 (factor) = 0'0745xlOO = 7-45 per
cent, sulphurous acid.
2. It is invariably found that the result is below the truth,
for not only is oxidation proceeding during the time occupied in
adding the iodine, but volatilisation of the free sulphurous acid
also, to a slight extent, takes place. The source of error may
be reduced by conducting a second titration, running into a
porcelain dish containing distilled water and gelatinised starch
solution the amount of iodine consumed in the first instance
(23'3 c.c.), and then adding to this the 10 c.c. of dilute sulphurous
acid. A further addition from the burette of as much as 1 c.c.
iodine may have to be made in order to produce the blue colour.
The result would therefore be 24*3 c.c. instead of the previously
mentioned 2 3 -3 c.c.
1 See footnote, p. 172.
150 THE BREWER'S ANALYST
The exactness of the method may, however, be still further
ascertained by the following method:
3. Take 10 c.c. of the prepared dilute acid solution in a
porcelain dish, and add a few drops of gelatinised starch solution.
In the first experiment 23'3 c.c. iodine were required, we
therefore now add this quantity, together with an extra 5 c.c.
N
= 28'3 c.c., and titrate with thiosulphate.
N
Suppose 7*1 c.c. thiosulphate are required to change the
blue colour; then
7'1 x -01265 (factor) = -0898 x 100 = 8'98 percent, sulphurous acid.
However, 5 c.c. extra iodine have been used, which are equal
to 1-60 per cent. (5 x "0032 = -0160 x 100), so that 1'60 from
the above 8'98 = 7'38 per cent. ; and as the amount found in the
first experiment with iodine was 7 '45 per cent., the one experiment
confirms the accuracy of the other, and the acid may be said to
contain 7 '45 per cent, of sulphurous acid.
Thiosulphate solutions are prone to change ; it is advisable,
therefore, to make a blank experiment with iodine ; and if this be
done, it is of no importance that the thiosulphate be strictly
decinormal, since its exact value, as compared with iodine, is
easily calculated, and the multiplier '01265 merely altered
accordingly.
The principle of this beautiful method of analysis, discovered
by Dupasquier, consists in the fact that free iodine converts
sulphurous into sulphuric acid by decomposing water, the oxygen
of which goes to the sulphurous and produces sulphuric acid ;
the hydrogen, being taken by the iodine, forming hydriodic acid.
The reaction between iodine and very dilute sulphurous acid
is represented by the formula
S0 2 + 1 2 + 20H 2 = 2H1 + H 4 S0 4 .
Bunsen found that the solution should not contain more than
0'5 per cent, of sulphur dioxide, since, if above this strength, the
action is reversed, the irregularity of decomposition varying with
the quantity of water present, and the rapidity with which the
iodine is added. This irregularity is, however, now obviated, as
shown by Mohr, by the use of ammonic, potassic, or sodic
bicarbonate, which have no effect upon iodide of starch. Either
of these salts, added in moderate quantity to the liquid sulphurous
acid, or, in case of sulphites, dissolving them in the alkaline
METHODS OF ANALYSIS 151
solution previous to titration with iodine, overcomes the difficulty
hitherto found in concentrated solutions.
This method can be applied to the determination of a great
variety of substances with extreme accuracy.
Bodies which take up oxygen, and decolorise the iodine solu-
tion, such as sulphurous acid, sulphites, sulphuretted hydrogen,
alkaline thiosulphates, etc., are brought into dilute solution,
gelatinised starch solution added, and the iodine delivered in with
constant stirring until a point occurs at which a final drop of
iodine colours the whole blue a sign that the substance can
take up no more iodine, and that the drop in excess has shown
its characteristic effect upon the starch.
In diluting the liquid acid or in dissolving sulphites, etc., the
distilled water employed for dilution should be well boiled and
cooled, since, as shown by Giles and Shearer, 1 the air dissolved
in the water used for dilution interferes with the accuracy of the
results. They adopt, therefore, the method of placing the
sulphite in a known excess of iodine, and determining such
excess by means of sodic thiosulphate.
Commercial sulphurous acid purchased by brewers for cleansing
purposes, fining manufacture, etc., should always be purchased
at a definite specific gravity, a convenient gravity being about
10-33.
AMMONIA.
Take 10 c.c. ammonia and weigh. Suppose the weight to be
9'67 grams ; this, divided by 10, gives the specific gravity as 0'967.
The quantity of normal acid required to saturate the 10 c.c.,
using methyl-orange as indicator, is, say, 46 c.c. ; then this
multiplied by 0'017 (coefficient) = 0'782
' 782xl( L8per cent, ammonia (NH 8 ).
y *u i
Carius's table, 0'967 specific gravity, gives 8 per cent. (p. 405).
SODIC CARBONATE.
If it were absolutely pure, 5 '3 grams of it should require exactly
100 c.c. acid to effect neutralisation. If we therefore weigh
that quantity, bring it into solution with distilled water, add a
1 Jnl. Soc. Chem. Ind., April 1884.
152 THE BREWER'S ANALYST
few drops of phenacetolin as indicator, and deliver into the
mixture normal hydrochloric acid from a 100 c.c. burette, the
number of c.c. required to saturate it will show the percentage
of pure sodic carbonate in the sample.
Suppose 90 c.c. acid are required. Then the sample contains
90 per cent, sodic carbonate.
As a further example 90 c.c. x '053 (coefficient factor) = 4*77.
477 x 100 nn
= 90 per cent.
O'o
Suppose, on the other hand, it is required to know the equiva-
lent percentage of
DRY CAUSTIC SODA,
free and combined, contained in the above sample of soda ash.
This may be ascertained by calculation thus :
The sample contains 90 per cent, of sodic carbonate.
Sodic oxide =62
Sodic carbonate = 106
= 0-585
90 x 0'5S5 = 52 '65 per cent, sodic oxide.
Again, instead of calculating the result, we may proceed as
follows :
Weigh 3'1 grams of the soda ash, bring it into solution with
water, add a few drops of phenacetolin, and titrate with normal
acid; the number of c.c. acid required to saturate it is the
percentage of sodic oxide.
Example :
N
Reading acid = 5 2 '6 c.c. = 52 '6 per cent, sodic oxide, or
90 per cent, carbonate. 1
ALKALINE SOLUTIONS.
From the nature of the substance, or its being in solution, the
percentage method previously employed cannot here be con-
veniently followed. For example, suppose we have a solution
which from the flame coloration is seen to be potash a weighed
or measured quantity of it is brought under the acid burette and
saturated exactly by normal hydrochloric acid, using phenacetolin
as indicator.
1 52-6 x -031 (coefficient factor) = 1 '630. 3'1 : 1'630 : : 100 : 52'6 per cent,
sodic oxide or 90 per cent, sodic carbonate.
METHODS OF ANALYSIS 153
It is advisable, owing to the usual high strength of these
solutions, to weigh or measure only about 5 c.c. and dilute
largely with distilled water so that the reaction may be clearly
observed.
Supposing, of 5 c.c. taken, the amount of normal hydrochloric
acid employed to saturate it is 37 c.c. The molecular weight of
potassic hydrate being 56, 100 c.c. - hydrochloric acid will
5*6 x 37
saturate 5*6 grams, therefore - = 2'072 ; and as 5 grams of
the solution were taken, 2*072 x 20 = 41*44 per cent. KHO.
On the other hand, suppose the specific gravity of the solution
is found to be 1 '380 ; this, by Tiinnermann and Richter's table
(p. 404), is equal to 41*37 per cent., against our 41*44 per cent,
found by titration.
With soda solutions we preceed in precisely the same manner.
For example, we have a solution which by the colour flame is seen
N
to be soda. Of 5 c.c. taken, the amount of hydrochloric acid
employed to saturate it is, say, 23 c.c.
N
The molecular weight of sodic oxide being 62, 100 c.c. of hydro-
6*2 x 23*0
chloric acid will saturate 6*2 grams, therefore lnn = 1*426 :
and as 5 c.c. were taken, 1*426 x 20 = 28*52 per cent.
Na 2 0.
The specific gravity is found, say, to be 1 *40 ; according to
Tiinnermann's table (p. 404) = 28*40 per cent, against our
28'52 per cent, by titration.
WATER ANALYSIS.
The following are the determinations to be made
1. Total solids.
2. Saline residue.
3. Organic and volatile matter.
4. Lime.
5. Magnesia.
6. Sulphuric acid.
7. Chlorine and chloride of sodium.
8. Iron.
9. Alkalinity before and after boiling.
10. Soda and potash.
154 THE BREWER'S ANALYST
Nitrogen as Nitrates and Nitrites :
11. Nitric acid.
12. Nitrous acid.
Organic Matter :
13. " Free or saline " ammonia.
1 4. " Albuminoid " ammonia.
15. Oxygen required to oxidise organic matter.
The following further tests are sometimes necessary :
16. Silica.
17. Lead.
18. Copper.
19. Bacteriological examination (see p. 369).
WATER ANALYSIS.
Collection of Samples.
Every precaution should be taken to ensure the collection of a
truly representative sample. Stoneware bottles should be avoided,
as they are apt to affect the hardness of the water, and are more
difficult to clean than glass. Stoppered glass bottles should be
used where convenient; those known as "Winchester Quarts,"
which hold about two-and-a-half litres each, are very handy and
easy to procure. One of these will hold sufficient for the general
analysis of a water, whilst two are ample for all purposes, including
a bacteriological examination, should such be required.
If corks are used, they should be netv, and well washed with
the water at the time of collection.
In collecting from a well, river, or tank, plunge the bottle itself,
if possible, below the surface ; but if an intermediate vessel must
be used, see that it is thoroughly clean and well rinsed with the
water. Avoid the surface water and also any deposit at the
bottom. If the sample is taken from a pump or tap, take care to
let the water which has been standing in the pump or pipe run
off before collecting, then allow the stream to flow directly into
the bottle.
If it is to represent a town water supply, take it from the
service pipe communicating directly with the street main, and
not from a cistern.
In every case, first fill the bottle completely with the water,
empty it again, rinse once or twice carefully with the water, and
then fill it nearly to the stopper and tie down tightly.
At the time of collection note the source of the sample, whether
from a deep or shallow well, a river, or spring. If it is from a
METHODS OF ANALYSIS 155
well, ascertain the nature of the soil, subsoil, and water-bearing
stratum, the depth and diameter of the well, its distance from
neighbouring cesspools, drains, or other sources of pollution;
whether it passes through all impervious stratum before entering
the water-bearing stratum, and if so, whether the sides of the well
above this are, or are not, water-tight.
If the sample is from a river, ascertain the distance from the
source to the point of collection ; whether any pollution takes
place above that point, and the geological nature of the district
through which it flows.
If from a spring, take note of the stratum from which it
issues.
In order to ensure uniformity, the bottle should invariably be
well shaken before taking out a portion of the sample for the
purpose of analysis.
Colour.
A very tolerable opinion may be formed as to whether a sample
of water contains unchanged organic matter by comparing its
colour with that of distilled water ; to this end Lovibond's
tintometer may be used, or, failing this, two white glass cylinders
about 12 or 18 inches high should be placed upon white paper or
a white porcelain slab, one filled with distilled water and the
other with the sample to be tested, side by side : any yellow or
brown colour in the sample indicates the presence of organic
matter, but it may not necessarily be owing to very objectionable
impurity, since purely vegetable matter such as peat will often
produce it.
Smell.
The smell can be observed by shaking up some of the water in
a large, wide-mouthed flask or bottle, and applying the nose to
the bottle immediately afterwards. If the water be warmed to a
slight extent, any objectionable smell is more readily detected.
Filtration.
Before commencing the quantitative analysis, it is necessary
to decide whether the water shall be filtered or not. This must
depend on the purpose for which the examination is undertaken.
As a general rule, if the suspended matter is to be determined,
the water should be filtered before the estimation of ammonia and
total solid residue ; if otherwise, it should merely be shaken up.
If the suspended matter is not determined, the appearance of
the water, whether clear or turbid, should be noted.
156 THE BEEWER'S ANALYST
Water derived from a newly sunk well, or which has been
rendered turbid by the introduction of innocuous mineral matter
from some temporary and exceptional cause, should be filtered ;
but the suspended matter, in most cases, particularly with
brewery well waters, need not be determined.
Suspended Matter.
From a sanitary point of view suspended matter is of minor
interest, because it may be in most cases readily and completely
removed by nitration. Mineral suspended matter is, however,
of considerable mechanical importance as regards the formation
of impediments in the river-bed by its gradual deposition, and as
regards the choking of niters and the binding effect it has with
the saline bodies causing incrustation in boilers.
1. Total Solids. Evaporate over the water bath half a litre
(500 c.c.) or a less quantity of the water, measured at 60 F.
(15*5 C.), in a platinum dish which has been heated to redness,
cooled under the desiccator, and carefully weighed.
As soon as the evaporation is complete, the dish with the
residue is removed from the water bath, its outer side wiped dry
with a cloth, and then dried in the oven for about three hours.
It is then placed under the desiccator, allowed to cool, weighed
as rapidly as possible, returned tu the oven, dried, copied, and
again weighed at intervals of an hour until the weight is constant.
Example :
Weight of platinum dish and solids . 70 '41 4 grams.
Weight of platinum dish . . . 60'420
9-994
A gallon of water weighs 10 Ibs. or 70,000 grains ; when taking
500 c.c. multiply by '2 to bring to 100 c.c., and by '7 to obtain
the number of milligrams in 70 c.c., which for the purpose of
calculation is reckoned as a miniature gallon. Milligrams per
70 c.c. equal grains per gallon; hence 9*994 x -2 = T9988 x '7 =
1-39916 = 13-9916 grains solid matter in 70 c.c., or 139'92
grains per gallon total solid matter.
2. Saline Residue. Having obtained the weight of the total
solid matter, the platinum dish containing it is placed over a gas
flame and gently ignited. If, on being heated, the solid residue
darkens, it indicates a large amount of organic matter ; and if it
becomes black, the water is highly contaminated. The ignition
is carried on for about half a minute until the residue is quite
METHODS OF ANALYSIS 157
white or brown, the latter showing the presence of iron. The
dish is then cooled, the residue recarbonated, by moistening it
with a drop or two of ammonic carbonate, and again gently
heated over the gas flame, care being taken that the carbonate is
not driven off during the heating. The dish is once more cooled
under the desiccator and again weighed at intervals until constant.
Example :
Weight of platinum dish and saline
residue ..... 69 '380 grams.
Weight of platinum dish . . . 60'420
8-960
8-960 x -2 = 1-7920 x -7 = 1-2544, or 125'40 grains per
gallon saline residue.
3. Organic and Volatile Matter. The difference between
the total solid matter and the saline residue, thus :
Total solid matter = 139*920 grains per gallon.
Saline residue = 125 '400
14*520 grains per g-allon
organic and volatile matter.
4. Lime. Take 500 c.c. of the water at 60 F. (15'5 C.) in
a large beaker, add 5 or 6 drops of hydrochloric acid, and boil
down to about half bulk. Now add about 20 c.c. of 10 per cent,
solution ammonic oxalate, about 10 c.c., 10 per cent, ammonic
chloride, and about the same quantity of 10 per cent, ammonic
hydrate, which cause the lime to separate in the form of calcic
oxalate. 1 The liquid should now be set aside and allowed to
1 The object of the addition of ammonic hydrate is as follows :
Lime may be precipitated in neutral or fairly acid solution by ammonic
oxalate, but the precipitation is in such case incomplete. In ammoniacal
solutions, however, the precipitation is perfect.
The addition of ammonic chloride is unnecessary for the separation of calcic
salts, but it is added to prevent the simultaneous precipitation of magnesia,
which also forms an insoluble oxalate, but not in the presence of ammonic
chloride. A quantity of ammonic oxalate should therefore be added sufficient
not only to convert the calcic, but also the magnesic, salts into oxalates.
Fresenius shows that in the presence of large quantities of magnesia this
process is not rigidly accurate, but that a small quantity of this body pre-
cipitates along with the lime ; and further, that unless a large excess of
ammonic oxalate is present, the lime is not completely precipitated. He
considers a re-solution and precipitation of the calcic oxalate a necessity, but
waters as a rule do not contain sufficient magnesia to render such operation
necessary.
158 THE BREWER'S ANALYST
stand for not less than 3 hours, by which time the precipitation
will be complete and the supernatant liquid bright.
Nearly the whole of the liquid is now carefully filtered into a
clean dry beaker, through a filter paper previously moistened
with water, the precipitated insoluble calcic oxalate, together with
the small quantity of liquid left in the beaker, being then stirred
up by means of a glass rod to the end of which is attached a
small piece of rubber tube ; the liquid is then passed on to the
filter, the beaker being rinsed with distilled water, any particles
of calcic oxalate being removed by the glass rod, and the repeated
washings in this manner transferred to the filter until every
particle of the oxalate has been transferred to the filter. The
filter paper is now washed by sparging successive portions of
boiling distilled water from the wash bottle, and these wash-
ings also collected in the beaker containing the filtrate. If
the filtrate is cloudy, it must be again returned to the filter
paper and filtered until perfectly brilliant; there is, however,
seldom any difficulty in this respect with a filtration of a lime
precipitate.
The filtrate from the lime is required for the subsequent
estimation of magnesia, and is therefore set aside until required.
The filter paper containing the calcic oxalate is now placed in
the water oven and dried, after which it is carefully folded, put
in a tared crucible, and placed on a tripod over a Bunsen flame
and the oxalate burned to a white or grey ash, the oxalate by
this ignition being reduced to carbonate. Very slight heat is
sufficient to decompose calcic oxalate into calcic carbonate, but
small quantities of carbon - dioxide are disengaged from the
carbonate so that it is advisable to " recarbonate." This is
effected by moistening the ash, after cooling, with two or three
drops of ammonic carbonate solution, then carefully drying on
the water bath, and finally gently heating for a moment or two
over a small flame. Any carbon-dioxide which may have been
volatilised in the first heating is thus replaced at the expense of
the ammonic carbonate, while the excess of the latter is volatilised
on drying in the water bath and subsequent exposure to gentle
heat over the flame.
The crucible is now placed under the desiccator to cool and
is then weighed, the ash being again recarbonated, dried, cooled,
and weighed until the weight is constant. The amount of calcic
carbonate (CaC0 3 ) so found is now calculated to that of calcic
oxide (CaO).
The atomic weight of CaC0 3 is 100, and that of CaO 56,
METHODS OF ANALYSIS 159
therefore every 100 parts of CaCO 3 contain 56 parts of CaO; the
quantity of calcic oxide is therefore calculated as follows :
56 x CaC0 3 found
"100
Or the same thing is arrived at by multiplying the CaC0 3 found
by -56.
Example :
Weight of crucible and precipitate . 8-027 grams.
Weight of crucible .... 7 '564
CaC0 3 -463
Then -463 x -2= "0926 grams CaC0 3 in 100 c.c.
0926 x -7 = -06482 CaC0 3 in 70 c.c. ; or
64'82 grains per gallon CaC0 3 , and
64-82 x -56 = 36-33 grains per gallon of lime (CaO).
5. Magnesia. To the filtrate from the lime add about 10 c.c.
of 10 per cent, solution ammonic or sodic phosphate and about
10 c.c. of strong ammonic hydrate, well stir, and allow to stand
for 6 hours, or preferably over-night. Filter, wash the pre-
cipitate with dilute ammonia, dry, place in a tared crucible, and
strongly ignite to a grey ash; cool under desiccator and weigh
as pyrophosphate of magnesia 2(MgO)P 2 5 .
The atomic weight of 2(MgO)P 2 O fi is 222, and that of 2MgO,
80; every 222 parts of the pyrophosphate therefore correspond
to 80 of magnesia, or
-52.-.-M.
222
The factor -36 may be employed to convert the one into the other.
Example :
Crucible and precipitated pyrophos-
phate 7'765 grams.
Crucible . ... 7-564
201
Then -201 x -2 = -0402 x 7 = -02814 per 70 c.c.
So that 28-14 x *36 = 10*15 grains per gfallon mag'-
nesia (Mg-0).
6. Sulphuric Acid. Take 500 c.c. of the water at 60 F.
(15*5 C.) in a large beaker, add three or four drops of hydro-
chloric acid, boil to half bulk, and add about 15 c.c. of 10 per
160 THE BREWER'S ANALYST
cent, solution baric chloride. Boil for a further two or three
minutes and then set aside in a warm place so that the baric
sulphate may settle. When the supernatant liquid is clear,
filter l and wash the precipitate thoroughly with boiling distilled
water. Now place the filter containing the precipitate in the
water oven to dry, then ignite to a white ash in a tared crucible,
cool under the desiccator and weigh, repeating ignition, cooling,
and weighing until the weight is constant.
Example :
Weight of crucible and baric sulphate . 8 '739 grams
Weight of crucible .... 7'650
1-089
Therefore 1 -089 x '2 = 2'178 x -7 = 1-5246 per 70 c.c., or 15'246
grains per gallon BaS0 4 .
It now remains to ascertain the quantity of sulphuric anhy-
dride corresponding to the weight of baric sulphate obtained.
The atomic weight of BaS0 4 is 233, and that of sulphuric anhy-
dride (S0 3 ), 80 ; 233 parts of baric sulphate therefore correspond
80
to 80 parts of sulphuric anhydride, hence - = '343 ; so that
2oo
we have merely to multiply by the factor '343. Thus 15'24G
grains per gallon BaSO 4 x -343 = 52 "29 grains per gallon
sulphuric anhydride (SO*).
7. Chlorine and Chloride of Sodium. To 250 c.c. of the
water at 60 F. (15*5 C.) in a large porcelain dish, add two or
three drops 10 per cent, potassic chromate (free from chlorine), so
as to give it a faint tinge of yellow, and add gradually from a
burette standard argentic nitrate solution (p. 137) until the red
argentic chromate which forms after each addition of the nitrate
ceases to disappear on stirring.
The chromate is simply an indicator, the affinity of silver for
chlorine being greater than that for chromic acid ; hence no
chromate of silver is found until the chlorides in the water are
used up.
Where extreme accuracy is desired, after completing a deter-
mination, destroy the slight red tint by an excess of a soluble
chloride, and repeat the estimation on a fresh quantity of the
1 It is sometimes difficult to obtain a clear filtrate owing to the sulphate
forming a very finely divided precipitate ; this may be avoided by the addition
at the time of adding the baric chloride, of about '005 gram of potato starch
which has a conglomerating action upon the precipitate and retains it on the
filter paper. Repeated filtration, however, is effectual.
METHODS OF ANALYSIS 161
water in a similar porcelain dish placed by the side of the
former. By comparing the contents of the dishes, the first
tinge of red in the second dish may be detected with great
accuracy.
It is absolutely necessary that the liquor examined should not
be acid, unless from carbonic acid, nor more than slightly alkaline.
It must also be colourless or nearly so. These conditions are
generally found in waters ; but, if not, they may be brought about
in most cases by rendering the liquid just alkaline with lime
water (free from chlorine), passing carbonic anhydride to satura-
tion, boiling, and filtering. The calcic carbonate has a powerful
clarifying action, and the excess of alkali is exactly neutralised by
the carbonic anhydride. If this is not successful, the water must
be rendered alkaline, evaporated to dry ness, and the residue
gently heated to destroy organic matter. The chlorine may
then be extracted with distilled water and estimated in the
ordinary way.
Example. 8 '5 c.c. argentic nitrate solution were required to
produce the reddish tint in 250 c.c. of the water. Then S'5 x '4 =
3-40 x -7 = 2*38 milligrams chlorine per 70 c.c. or grains
per gallon.
In order to convert chlorine to sodic chloride :
The atomic weight of chlorine (Cl) is 35 '5, and that of sodic
chloride (NaCl) 58*5. Every 35 '5 parts of chlorine therefore
K Q , K
correspond to 58'5 parts of sodic chloride, hence - = 1*645;
oO'D
so that we multiply by the factor 1'645, or, to simplify matters, by
1-65. Thus 2-38 grains per gallon chlorine x 1'65 = 3'92 grains
per gallon sodic chloride.
8. Iron. Take 70 c.c. of the water at 60 F. (15-5 C.) in a
small boiling flask, add 1 c.c. concentrated nitric acid (the
presence of free acid is always necessary in this process in order
to convert iron existing in the water in a ferric state to that of
the ferrous state), and boil for 5 minutes. Cool to 60 F.
(15*5 C.), transfer to a Nessler tube, and make up to 70 c.c.
with distilled water. Add a drop or two of 10 per cent, solution
potassic ferrocyanide, when, if iron is present, a blue colour will
appear which is then imitated by a standard solution of iron
(p. 137), added to a similar bulk of distilled water in a Nessler
tube until the colour matches that of the sample, when both tubes
are looked through while standing on a white surface.
The exact strength of the iron solution being known (1 c.c. =
O'l milligram Fe), it is easy to arrive at the quantity of pure iron
11
162 THE BREWER'S ANALYST
present in the water, and to convert it into its state of combina-
tion by calculation.
Example. In this case 1'4 c.c. of the standard iron solution
were required to imitate the blue colour, each c.c. being equiva-
lent to O'l milligram of iron.
1*4 x '1 = '14 milligram of iron in 70 c.c.
or '14 grain per gallon.
It is usual, however, to express the iron as ferric oxide (Fe 2 3 ),
112
so that as 160 parts Fe 2 3 equal 112 parts of iron, i- =0-7. We
have merely to multiply O'l 4 by 0'7 to obtain the amount of
ferric oxide, which, therefore, equals 0*098 grain per gallon
Fe 2 3 .
This method, which approaches in delicacy the Nessler test
for ammonia, is applicable for very minute quantities of iron ;
in fact, 1 part of iron in 13,000,000 parts of water can thus be
detected.
9. Alkalinity before and after Boiling 1 . This estimation
is merely carried out as a check upon the accuracy of other
analytical results, and is of great importance, particularly with
waters containing carbonate of soda or potash.
Thus, after combining the acids and bases we have, say, a
certain quantity of calcic carbonate, and a certain quantity of
magnesic carbonate. By now finding the equivalent of the
magnesic carbonate and expressing it as calcic carbonate, this;
added to the actual amount of calcic carbonate originally found,
shows the total alkalinity of the water ; which, if the same as the
alkalinity estimated by this test, shows that the analysis in this
respect is correct. If, however, there is a deficiency, then the
analysis is incorrect ; whilst if there is an excess, it shows that
such excess is due to carbonate of soda or potash.
The estimation is made as follows :
(1) Measure 350 c.c. of the water at 60 F. (15'5 C.), run into
N
a large beaker and titrate with acid, using two or three drops
of methyl- orange as an indicator. Say, for instance, that 32*2 c.c.
acid were required to produce the faint pink coloration.
(2) A further 350 c.c. of the water at 60 F. (15 "5 C.) are now
measured out into a large beaker and boiled for three-quarters of
an hour. The liquid is then filtered through a paper previously
moistened with boiling distilled water, the beaker rinsed with
METHODS OF ANALYSIS 163
distilled water, and the washings transferred to the filter. The
filtrate, after cooling, is now titrated with - acid, using methyl-
orange as an indicator. Say, for example, that T6 c.c. acid
were required to produce the faint pink coloration.
Now the difference between these two titrations is due to the
precipitation of carbonate of lime during boiling, with perhaps a
trace of carbonate of magnesia. Lime is not, however, absolutely
insoluble in boiling water, but remains in solution to the extent
of 1 4 26 grain per gallon, and this figure may therefore be taken
into account when calculating the result. If 350 c.c. of the water
N
are employed, each c.c. of acid corresponds to one grain of
carbonate of lime per gallon.
Example :
N
350 c.c. unboiled water required . 32*2 c.c. acid.
350 c.c. boiled and filtered water 1'6
Alkalinity removed by boiling . 30'6
grains per gallon CaC0 3 . To this figure is added 1*26 (solubility
of CaC0 3 in boiled water) = 31*8 grains per gallon CaC0 3 .
10. Soda and Potash. Take 500 c.c. of the water at 60 F.
(15'5 C.) in a beaker and boil down to about 50 c.c. Add baric
hydrate until the liquid is alkaline (about 10 c.c.), and set aside in
a warm place (on the water bath) for one hour. Filter and wash
the precipitate well with hot distilled water. To the filtrate add
about 5 c.c. of 10 per cent, ammonic chloride and ammonic
carbonate until no more barium is precipitated (probably about
10 c.c.).
The barium precipitates the bases except the alkalies soda
and potash ; and the ammonic chloride and carbonate precipitate
the excess of barium, leaving the alkalies in solution as chlorides.
Now allow to stand for 2 hours, then filter and wash with
hot distilled water, after which boil the filtrate down to about 25
c.c. ; transfer to a clean platinum dish and evaporate to dryness.
When dry, gently ignite until ammoniacal fumes cease to be given
off, but taking care not to heat too strongly for fear of volatilising
small quantities of chlorides. Cool under the desiccator and
weigh ; repeat ignition, cool, and again weigh. Now extract the
residue with warm distilled water and filter. Return the filter
paper to the platinum dish, ignite, cool, and weigh.
164 THE BREWER'S ANALYST
The difference between the former weight (which is the tare of
the dish and traces of insoluble substances) and this one gives
sodium and potassium as chlorides. It now remains to separate
these alkalies. This is performed by adding 5 c.c. of platinic
bichloride to the nitrate, which is then evaporated to dryness,
dried at 212 F. (100 C.), cooled, and weighed until constant.
The gain in weight is due to potash existing as potassic platinic
chloride (KCl 2 )PtCl 4 . The potassic chloride being thus found,
the quantity of sodic chloride is then calculated.
Example :
Weight of platinum dish + solids before
extraction '. 62'570 grams.
Weight of platinum dish + solids after
extraction .... 62"462 ,,
108
108 x -2 = -0216 x -7 = 15-120 grains per gallon total chlorides.
After treatment with platinic chloride :
Weight of platinum dish + solids . 60-450 grams.
Weight of platinum dish . . 60'418
032
032 x -2 = -064 x '7 = -0448 ; therefore potassic platinic chloride
= 4'48 grains per gallon and 4'48 x 307 1 = 1*375 grain per gallon
potassic chloride.
Total alkalies . . 15*120 grains per gallon.
Potassic chloride . . 1'375
Sodic chloride . . 13*745
NaCl 13-745 x '53 = 7-25 grains per gallon Na 2 0.
KCL 1-375 x -63 = 0-86 K 2 O.
It will be seen that the estimation of soda and potash is rather
tedious, and by no means easy. Frequently, owing to incomplete
separation of other bodies, the alkalies come out too high, and this
error is attributed to the soda, owing to the potash being sub-
sequently determined.
1 (KCl 2 )PtCl 4 = 484'5 gives 2KC1 = 1487, therefore 1 = '307.
2 j 2NaCl = 1167 gives Na 2 = 62'0, therefore 1 = '53.
i 2KC1=1487 gives K 2 = 94'0, therefore 1 = "63.
METHODS OF ANALYSIS 165
NITROGEN AS NITRATES AND NITRITES.
By far the best test for estimating nitrogen as nitrates and
nitrites in water is that known as the mercury method, but it has
the great disadvantages of requiring costly gas-analysis apparatus,
of being complicated, and, in inexperienced hands, yields poor
results. The indigo method about to be described is the one now
generally resorted to, and when carefully performed gives excellent
results. In fact the following will show the difference in the
results obtained by the two processes :
Parts per 100,000.
With Mercury. With Indigo.
1 . . 0-973 ' . . . 0-912
2 . . 4-235 . . . 4-530
3 . 1-825 . . . 1-706
4 . . 0-729 . . . 0-676
5 . . 2-749 . . . 2-912
6 . . 1-696 . . 1-294
7 . . 2-144 . . 2-265
8 . . 0-354 . . . 0-338
9 . . 2-860 . . 2-824
10 . . 0-222 . . . 0-221
The indigo process was originally devised by Marx 1 and
improved by Warrington. 2
The principle of the method is that of liberating free nitric and
nitrous acids from their combinations by the aid of strong
sulphuric acid, and measuring the quantity so liberated by the
decoloration of a solution of indigo.
The accuracy of the method is disturbed in the presence of
much chlorides, so that for such cases an alternative method,
Gladstone and Tribe's, is also given.
11. Estimation of Nitric Acid : Marx Indigo Process.
Take 50 c.c. of the water at 60 F. (15'5 C.) in an 8 ounce flask
and add an equal bulk of pure strong sulphuric acid, allowing
the acid to run down the side of the flask and avoiding mixing
the solutions as far as possible. Now agitate the contents of the
flask and rapidly add, from a burette, a standard solution of
indigo (p. 136), until a permanent faint bluish-green tint is
perceptible. Read off the number of c.c. of indigo consumed,
and as each c.c. corresponds to 0*1 milligram of nitrogen, the
1 Zeitschr.f. ang. Chem., vol. viii. 412.
- Jnl. Chem. Soc. Trans., xxxv. 578.
166 THE BREWER'S ANALYST
amount of nitrogen in the 50 c.c. of the water is found by
multiplying by '01.
To find from this the corresponding amount of nitric acid is
a simple matter. Two atoms of nitrogen (N 2 ) are contained in
the molecule of nitric anhydride (N 2 O 5 ) ; the calculation there-
fore is :
N 2 =28 N 2 5 =108
108 x N found ~
Or, by dividing the atomic weight of N 2 into that of N 2 O 5 , the
factor 3 '86 is obtained, which gives the amount of nitric acid
(anhydrous) from the nitrogen found; and the result is then
calculated to grains per gallon.
Example. 50 c.c. of water took 2*3 c.c. indigo solution
2'3 x 2 = 4-6 x -7 = 3-22 per 70 c.c. water; 3'22x'l = '322 gram
N per gallon; -322 x 3'86 = 1'25 grain per gallon nitric
anhydride.
Estimation of Nitric Acid: Gladstone and Tribe's
Method. This method was introduced by Gladstone and Tribe J
twenty-eight years ago, and its application to water analysis was
fully dealt with in 1881 by W. Williams. 2 It is accomplished
as follows :
Take 250 c.c. of the water at 60 F. (15-5 C.) in a porcelain
dish, add two or three drops of caustic potash solution which
must be free from ammonia, evaporate over the water bath ta
about 50 c.c., and then transfer to a small flask, the cork of
which is provided with a thistle-headed funnel and stop-cock.
Wash the porcelain dish with distilled water, and add the
rinsings to the flask so as to make up the bulk to about 20 c.c.
Now add a few pieces of copper-coated zinc. 3 Connect the flask
to a distilling apparatus and arrange the exit of the condenser
tube with a glass tube passing to the bottom of a 100 c.c. flask
in which has been placed 1 or 2 c.c. of distilled water and a
single drop of hydrochloric acid. Now heat the flask gently
for one hour (do not boil) and then distil the contents until
nearly the whole has evaporated ; then fill up the funnel with
hot distilled water and turn on the stop-cock, allowing the
whole to pass over into the 100 c.c. flask. Repeat addition
of water to the flask and continue distillation until about
90 c.c. have been collected. Remove the 100 c.c. flask,
1 Jnl. Chem. Soc., 1878, 140. 2 Ibid., 1881, 100.
3 Granulated zinc is immersed in strong copper sulphate solution until
metallic copper is deposited on the surface of the zinc.
METHODS OF ANALYSIS 167
dilute to mark with distilled water free from ammonia,
agitate, take 5 c.c., dilute to 50 c.c., and Nesslerise as ex-
plained (p. 169).
Each equivalent of ammonia found corresponds to one equiva-
lent of nitric acid; that is to say, each 17 parts of ammonia
correspond to 54 parts of nitric acid ;
So that by multiplying the ammonia found by the factor 3 '176,
we get the nitric acid, and the result is calculated to grains per
gallon.
Example. 250 c.c. of water taken and 5 c.c. of the distillate
(after diluting to 50 c.c.) required 7'0 c.c. of standard ammonia
to produce equivalent colour value. 7'0 x '01 = '070 milligram
of NH 3 in the 5 c.c. or 1'40 in the whole distillate containing the
ammonia from the nitric acid in 250 c.c. of the water. Then
1-40 x -4= '560 milligrams of NH 3 in 100 c.c. x '7 = '3920 in
70 c.c., i.e. "3920 grain per gallon NH 3 due to nitric acid. This
multiplied by 3-176 = 1 '25 grain per gallon nitric an-
hydride.
12. Nitrous Acid: Greiss's Method of Detection. 1 It is
only in very impure waters that nitrous acid is found, and even
in these cases it generally exists in quantity too minute for
quantitative estimation.
The author has never yet found nitrous acid in a deep well
water, and believes that where it has been detected in such waters
it is due more to the system adopted than to the fact of its
existence.
The simplest method of detection is that proposed by Greiss,
which consists in the addition of meta-diamido-benzene to the
water after acidifying, which imparts a yellow colour with the
most minute traces of nitrous acid. 100 c.c. of the water are
taken in a Nessler tube, 1 c.c. of strong sulphuric acid added,
and then a few drops of meta-diamido-benzene solution. The
tube, after standing for a few minutes, is then examined by
looking down through it, on a white porcelain tile or piece of
white paper.
Nitrous Acid: Fresenius's Method of Estimating-.
The following method is given by Fresenius 2 for the quantitative
1 For full particulars of Greiss's method, see paper by R. Warrington, Jnl.
Chem. Soc., 1881, 229.
2 Fresenius's Quantitative Analysis, Churchill.
168 THE BKEWER'S ANALYST
estimation should nitrites be present in quantity in a water,
which is seldom the case :
Take 250 c.c. of the water at 60 F. (15'5 C.), acidify by the
addition of a few drops of acetic acid, place in a retort and distil
off about 100 c.c., collecting the same in a 250 c.c. flask and
making up the distillate to mark with distilled water.
A portion of this distillate is then taken, acidified with a few
drops of pure sulphuric acid, and titrated against a very weak
solution of potassic permanganate, 30 c.c. of which should equal
'01 gram of iron = '0034 nitrous anhydride ^N T 2 3 .
Organic Matter. We are indebted to Wanklyn, Chapman,
and Smith for the now well-known "albuminoid ammonia
process " of estimating the quantity of nitrogenous organic matter
in water, which dates from the year 1867. 1
The method depends upon the conversion of the nitrogen in
such organic matter into ammonia when distilled with an alkaline
solution of potassic permanganate. The authors have given the
term "albuminoid ammonia" to the NH 3 produced from nitro-
genous matter by the action of permanganate, doubtless because
the first experiments made in the process were made with
albumin ; but they also proved that ammonia may be obtained
in a similar manner from a great variety of nitrogenous organic
substances, such as hippuric acid, narcotine, strychnine, morphine,
creatine, gelatine, casein, etc. Unfortunately, however, although
the proportion of nitrogen yielded by one substance when treated
with boiling alkaline permanganate appears to be definite, yet
different substances give different proportions of their nitrogen.
Thus hippuric acid and narcotine yield the whole, but strychnine
and morphine only one-half of their known proportions of
nitrogen. Hence the value of the numerical results thus obtained
depends entirely on the assumption that the nitrogenous organic
matter in water is uniform in Its nature, and the authors say
that in a river polluted mainly by sewage "the disintegrating
animal refuse would be pretty fairly measured by ten times the
albuminoid ammonia which it yields."
They also state that " the albuminoid ammonia from a really
good drinking water should not exceed O'OOS parts per 100,000."
The average of fifteen samples of Thames water supplied to
London by the various Water Companies some years ago was
0'0089, and in five samples supplied by the New River Company
0-0068 parts per 100,000. The rapidity and simplicity of the
operation are the chief merits of this process, and the information
1 Jnl. Chem. Soc. N.S., vol. v. 591.
METHODS OF ANALYSIS 169
to be obtained from its performance may, for some purposes, be
of considerable value ; and even if the numerical results cannot
be insisted upon, yet a good water could not be condemned by it,
and a bad one should not escape its indications.
There are two estimations to be made, viz. :
13. Free or saline ammonia.
14. Albuminoid ammonia.
13. Estimation of Free or Saline Ammonia. Half a
litre (500 c.c.) of the water at 60 F. (15-5 C.) is measured and
added to a retort, together with 10 c.c. of a saturated solution of
sodic carbonate. The retort is then connected with a Liebig
distilling apparatus (fig. 35, p. 31), condensing water turned on,
and a Bunsen-flame placed close under the bottom of the retort
and lighted full on. The distillation soon commences, and the
distillate should be received in a tall glass cylinder of about
150 c.c. capacity, and marked at 50 c.c. and 100 c.c.
Four such cylinders are required at hand during the operation.
When 50 c.c. have distilled over, the cylinder should be
removed and a fresh cylinder placed to receive a further 50 c.c.
of the distillate.
Whilst this second cylinder is slowly receiving the second
50 c.c. distillate, the free or saline ammonia contained in the
first 50 c.c. should be tested. 1
In order to perform this, a standard tube is first made up as
follows :
NESSLERISING.
To a tall glass cylinder of a capacity of 150 c.c., marked at
50 c.c. and 100 c.c., similar to those employed for the collection
of the. distillate, but graduated at each 5 c.c., is added from a
burette 5 c.c. of standard ammonia (p. 139), and then made up
to 50 c.c. with water free from ammonia (p. 139) 2 and mixed.
One c.c. of Nessler's solution (p. 139) is then added, and the
whole mixed. One c.c. of Nessler's solution is at the same time
added to the 50 c.c. distillate, and both this tube and the
1 It is inadvisable to allow the tubes containing the distillate to remain
standing in the laboratory for any length of time, as (water being very
absorbent) ammoniacal or sulphuretted hydrogen fumes may be absorbed and
thus vitiate the results
2 Distilled water invariably contains a large percentage of ammonia, and
therefore, if not previously freed from the same, should not be used. Good
tap-water will usually be found free, and may, therefore, in most cases be
employed.
170 THE BREWER'S ANALYST
standard tube are now placed on a white surface, such as a
white tile, and allowed to stand for 5 minutes. By this time
a yellow or brown colour will be produced in the distillate,
varying in intensity with the amount of free ammonia contained
in the water, and the object is to imitate the colour in the
standard tube.
The two tubes are therefore taken and examined side by side.
If the colour in the standard tube is too deep, withdraw sufficient
solution, so that, on looking down the tubes on to the white surface,
the colours are exactly of the same intensity. Note the amount
of standard ammonia required. If the colour is darker than that
of the standard, a fresh standard of double strength should be
made. The second 50 c.c. distillate is now taken and Nesslerised
in a similar manner; a third 50 c.c. distillate collected and
Nesslerised, and again a fourth 50 c.c. if necessary. Three
separate 50 c.c.'s, however, usually suffice with most waters.
Generally speaking, the whole of the free NH 3 will come over in the
first 100 or 150 c.c., but the distillation should be continued
until 50 c.c. of the distillate contain less than j-^ milligram of
NH 3 .
Wanklyn has recommended the uniform plan of Nesslerising
only the first 50 c.c. for free ammonia, throwing away the 150 c.c.
subsequently distilled, and calculating that it contains one-third
of the quantity found in the first 50 c.c.
14. Estimation of Albuminoid Ammonia. To the contents
of the retort left from the operation just described, are at once
added, through a clean funnel inserted into the tubulure of the
retort, 50 c.c. alkaline permanganate (p. 140). Having added this,
resume the distillation, and estimate the ammonia as before until
no more is evolved ; generally speaking, it is sufficient to distil
150 c.c. after adding the alkaline permanganate, estimating the
ammonia in each 50 c.c. The boiling is often very irregular,
especially in bad waters, and if so it is advisable to introduce into
the retort a few small pieces of freshly ignited pumice or pipe-
clay to moderate the bumping. It is always advisable to
incline the neck of the retort upwards, so that the liquid carried
up by spirting may be returned ; especially as manganese com-
pounds in particular have a powerful effect upon the colour pro-
duced by the Nessler solution, generally intensifying it> and thus
vitiating results. The amount of ammonia estimated by the
Nessler test in this distillate is entered as albuminoid ammonia.
The number of c.c. of standard ammonia required to imitate
the colour intensity in each tube are now added together, and
METHODS OF ANALYSIS 171
the result calculated and expressed in parts per million as
follows :
The graduated tube contained 5 c.c. of standard ammonia (O01
milligram per c.c.), 50 c.c. therefore contain 0'05 milligram of
ammonia.
Free Ammonia
1st tube, 50 c.c. distillate
from NaC0 3 = 42 c.c. standard ammonia.
2nd tube, 50 c.c. distillate
from NaC0 3 = 19
3rd tube, 50 c.c. distillate
from NaCCL = Nil.
61 c.c. total to equal tint.
Now 50 c.c. = '05 milligram of ammonia, therefore '061
milligram is present in the 61 c.c. ; that is, in 500 c.c. of the water,
or -122 per 1000 c.c. of water. Now 1000 c.c. contain 1,000,000
milligrams, therefore milligrams per 1000 c.c. = parts per million.
The sample therefore contains 0'122 parts per million Of
free ammonia.
Albuminoid Ammonia (calculated in the same way) :
1st tube, 50 c.c. distillate from
potassic permanganate = 19 c.c. standard ammonia.
2nd tube, 50 c.c. distillate from
potassic permanganate = 12 ,,
3rd tube, 50 c,c. distillate from
potassic permanganate = Nil.
31 c.c. total.
31 c.c. = '031 milligram of ammonia in 500 c.c., or 0*062
milligram in 1000 c.e. or parts per million.
Jf it is desired to express the result in parts per 100,000, instead
of in parts per million, it is written thus :
Free ammonia =0'012.
Albuminoid ammonia = 0*006.
15. Oxygen required to oxidise Organic Matter. This
process, originally designed by Forschammer and reintroduced by
Tidy, depends upon the estimation of the amount of oxygen
absorbed in oxidising the organic and other oxidisable matters in
172 THE BREWER'S ANALYST
a known volume of water, when slightly acidified with sulphuric
acid.
For this purpose a standard solution of potassic permanganate
(p. 138) is used in excess; the amount unoxidised after a given
time being ascertained by the help of a standard solution of sodic
thiosulphate (p. 138), by the aid of the well-known iodide of starch
reaction.
Ferrous salts, nitrites, or sulphuretted hydrogen, if present in
the water, also decompose the permanganate ; but as organic matters
are only slowly oxidised, the bodies named affect the permanganate
almost immediately. Therefore, by conducting two experiments,
one after standing 15 minutes, the other after standing 4 hours,
the reduction of the permanganate due to iron, nitrites, etc., and
that due to organic matter, may be determined.
The estimation is performed as follows :
A stoppered bottle of about 300 c.c. capacity is carefully rinsed
out with dilute sulphuric acid and well rinsed afterwards with
distilled water. Ten c.c. of standard potassic permanganate and
200 c.c. of the water are then added, and afterwards 10 c.c. of
dilute sulphuric acid, which is first rendered a faint pink by the
addition of a few drops of the permanganate.
The bottle, with the stopper replaced, is then set aside on the
forcing tray and maintained at about 75-80 F. (23-8-26'6 C.) for
4 hours.
At the end of this time, the undecomposed permanganate is
determined as follows :
One or two drops of potassic iodide solution are added to the
water in the bottle, which change the pink colour to yellow, due
to the liberation of the free iodine. Standard thiosulphate
solution is now run in from a burette until the yellow colour has
nearly, but not quite, disappeared. A few drops of freshly
prepared gelatinised starch solution l are now added, which turn
the solution blue. The thiosulphate is then again added to the
solution until the blue colour is just destroyed. The quantity of
thiosulphate used is noted. Let us denote this as A.
As the thiosulphate solution is liable to slightly change upon
keeping, a blank experiment is now made to determine its value.
This is performed by taking 200 c.c. distilled water, 10 c.c. of the
standard permanganate, and 10 c.c. of dilute sulphuric acid made
faintly pink with permanganate. A drop of potassic iodide is
1 Gelatinised starch, prepared by mixing about 1 gram of potato starch with
about 80 c.c. distilled water, boiling for a few minutes, cooling, and making
up to about 100 c.c.
METHODS OF ANALYSIS 173
added, which changes the colour to yellow, and the solution is
again titrated with the thiosulphate solution. This gives the
value of the thiosulphate solution. Let us denote this as B.
A further experiment is now performed with a further 200 c.c. of
the water, with the addition of permanganate and acid as before,
but allowed to stand 15 minutes, after which a drop of potassic
iodide is added and the solution titrated wit thiosulphate as
before described. Let us denote this by C.
From the results of the three experiments the amount of
oxygen absorbed is thus obtained :
A. 200 c.c. of water after 4
hours required 9'3 c.c. thiosulphate solution.
C. 200 c.c. of water after 15
minutes required 10'8 ,,
B. Blank experiment required 11 '4 ,, ,,
1T4 equals 10 c.c. permanganate, therefore 9'3 = 8'1
10x9-3
=o'i
11-4
and 10 - 8'1 = 1 '9 permangante absorbed in 4 hours.
Similarly, as 11*4 equals 10 c.c. permanganate, 10-8 equals 9'5,
and 10-9'5 = 0'5 permanganate decomposed in 15 minutes.
Each c.c. of the standard permanganate equals 0*1 milligram of
available oxygen, so that the above figures correspond to '19 and
05 milligram respectively per 100 c.c. of water.
It is usual, however, to express the results in terms of parts
per 100,000, so that as 100 c.c. contains 100,000 milligrams,
we get :
Oxygen absorbed in 15 minutes . . . '025
Oxygen 4 hours . . '095
16. Silica. It is only in exceptional circumstances that the
estimation of silica is necessary ; such, for instance, as when the
water is seen to contain an excess of suspended or deposited
matter. In such instances the estimation is carried out as
follows :
To 500 c.c. of the water at 60 F. (15-5 C.) add a few drops of
hydrochloric acid, and evaporate by degrees to dry ness in a
platinum dish. Heat to 300 F. (14S'8 C.), cool, add a few
more drops of hydrochloric acid and about 50 c.c. distilled water.
Stir the residue by the aid of a rubber-tipped glass rod and allow
to stand when the silica precipitates.
Filter, wash the precipitate with distilled water, dry the filter
174 THE BREWER'S ANALYST
paper and its contents in the water bath, ignite, cool under
desiccator, and weigh.
Example :
Weight of platinum dish + Si0 2 . . . 9'688
Weight of platinum dish . . 9 '685
003
0030 x -4 = -001 20 x -7= -00084.
= 0'84 grain per gallon.
17. Lead. Add 50 c.c. of the water at 60 F. (15 -5 C.) to a
Nessler tube, acidulate with a few drops of acetic acid, and then
run in 10 c.c. of saturated aqueous solution of sulphuretted
hydrogen.
Compare the colour thus produced in a similar cylinder with a
known quantity of a standard solution of lead acetate in a manner
similar to that described for the estimation of iron.
The lead solution may be prepared so as to contain 0'183 gram
of normal crystallised plumbic acetate in a litre of distilled water
at 60 F. (15-5 C.) ; each c.c. will therefore correspond to '001
gram of metallic lead.
18. Copper. Of the coloured reactions which copper gives
with different reagents, those with sulphuretted hydrogen and
potassic ferrocyanide are by far the most delicate, both showing
their respective colours in 2,500,000 parts of water. Of the two
reagents sulphuretted hydrogen is the more delicate ; but potassic
ferrocyanide has a decided advantage over sulphuretted hydrogen
inasmuch as lead, when not present in too large quantity, does
not interfere with the depth of colour obtained, whereas to sul-
phuretted hydrogen it is, as is well known, very sensitive. And
though iron if present would, without special precautions being
taken, prevent the determination of copper by means of potassic
ferrocyanide, yet, by the method here described, the copper in a
solution can be estimated by this reagent. Ammonic nitrate
renders the reaction much more delicate ; other salts, such as
ammonic chloride and potassic nitrate, have likewise the same
effect.
The method of analysis consists in the comparison of the
purple-brown colours produced by adding to a solution of potassic
ferrocyanide first, a solution of copper of known strength ; and
secondly, the solution in which the copper is to be determined.
To 100 c.c. of the water at 60 F. (15'5 C.) add two or three
drops of nitric acid and evaporate to dryness in a platinum dish.
METHODS OF ANALYSIS 175
Ignite the residue to get rid of any organic matter that may
colour the liquid, and dissolve in a little boiling distilled water
and a drop or two of nitric acid ; if the residue is not all soluble, it
does not matter. Ammonia is next added to precipitate the iron,
the latter filtered off, washed, redissolved in nitric acid, and again
precipitated by ammonia, filtered off, and washed. The filtrate is
added to the one previously obtained, and the copper estimated
in the united filtrates after rendering the liquid neutral.
The liquid must be neutral, for, if it contain free acid, the
latter lessens the depth of colour and changes it from a purple-
brown to an earthy brown. If it should be acid, it is rendered
slightly alkaline with ammonia, and the excess of the latter got
rid of by boiling. The solution must not be alkaline, as the
brown coloration is soluble in ammonia and decomposed by potash
or soda. If it be alkaline from ammonia, this is removed by
boiling; while free potash or soda, should they be present, are
neutralised by an acid and the latter by ammonia.
Example. Two Nessler tubes are taken and into each is run five
drops of potassic ferrocyanide. Fifty c.c. of the neutral water to
be tested are now run into one cylinder and a similar quantity of
distilled water into the other; 5 c.c. of ammonic nitrate, 10 per
cent, solution, are now added to each cylinder, and then the colour
produced in the cylinder containing the water under examina-
tion is imitated by running into the other cylinder standard
copper solution till the colours in both cylinders are of equal
depth,, the liquid being well stirred after each addition of the
copper solution.
Combination of Acids and Bases. The amount of acids
and bases having been determined, it now becomes necessary to
calculate the salts in the form in which they are generally
believed to exist in water. The salts are usually calculated
on the basis proposed some years ago by Fresenius, the general
rules laid down by him being as follows :
(1) The chlorine is combined with sodium.
(2) Any chlorine afterwards left is combined with calcium,
magnesium, and potassium in respective order.
(3) Potash is next combined with sulphuric acid.
(4) If sodium remains, it is combined with nitric acid (N 2 O 5 ) ;
and if there is still an excess, it is combined with carbon-dioxide.
(5) Lime is first combined with nitric acid, then with sulphuric
acid, and finally with carbon-dioxide. Whilst if chlorine is in
excess of that required to saturate the sodium (these amounts
generally saturate one another), it is combined with calcium.
176 THE BREWER'S ANALYST
(6) Magnesia is combined first with nitric acid (if lime has not
saturated it) then with sulphuric acid, whilst any excess is
combined with carbon-dioxide.
(7) Any excess of lime is always finally combined with carbon-
dioxide ; the reason being that any ordinary water contains C0 2 ,
and any excess of lime must combine with the same to form
carbonates.
The sum of these constituents is checked by the alkalinity of
the water, so that if, by calculation, carbonate of potash or soda
is found to exist, the alkalinity of the water after boiling would
prove the existence of one or the other or both.
The total salts should almost equal the saline residue of the
water when dried at 350 F. (176'6 C.), provided nitrates are
not present.
We may now proceed to combine the acids and bases of the
foregoing analysis, which is that of a water drawn froin a well at
Burton-on-Trent, suitable only for bitter-ale production, and
follow with typical combinations of a water suitable for stout and
porter, and then one suitable for mild-ale production. First,
however, it may be useful if we tabulate the proportions of the
various acids and bases necessary to saturate one another in
order to form salts.
80 parts sulphuric acid combine with
56 parts lime to form sulphate of lime.
40 magnesia to form sulphate of magnesia. -
62 ,, soda to form sulphate of soda.
94 potash to form sulphate of potash.
108 parts nitric acid combine with
56 parts lime to form nitrate of lime.
40 ,, magnesia to form nitrate of magnesia.
62 soda to form nitrate of soda.
44 parts carbonic acid combine with
56 parts lime to form carbonate of lime.
40 ,, magnesia to form carbonate of magnesia.
62 ,, soda to form carbonate of soda.
71 parts chlorine (35'5 x 2) combine with
40 parts calcium to form calcic chloride.
24 ,, magnesia to form magnesic chloride.
46 soda to form sodic chloride.
Now, taking the results of our previously conducted analysis,
we proceed to combine the acids and bases.
METHODS OF ANALYSIS 177
TYPE I.
The sodium being in excess, we take the chlorine and combine
it with sodium :
35'5 parts 01 require 23 parts Na.
90
Therefore 2'37 01 x |f = 1 "53 Na required,
oO *0
and 1-53 Na + 2'37 Cl = 3'90 NaCl.
We now take the potash and combine it with sulphuric acid :
94 parts K 2 require 80 S0 3 .
Therefore 0'86 K 2 x = 073 SO S required,
t?4r
and 0-73 S0 3 + 0'86 K 2 = 1 '59 K 2 S0 4 .
We have now to combine nitric acid with sodium :
108 parts Na 2 combine with 62 parts N 2 5 .
fiO
Therefore 1 '25 N 2 5 x ^ = 071 Na 2 required,
108
and 0-71 Na 2 + 1 -25 N 2 5 = 1 "96 Na(N0 3 ) 2 .
Thus far we have used up 1'53 Na to form NaCl, and 071
Na 2 to form sodic nitrate. But in our analytical figures the
soda 7'25 is expressed as Na 2 ; we have therefore to calculate
the 1-53 Na back to Na 2 :
46 parts Na require 62 parts Na 2 0.
So 1-53 (amount Na used) x _ = 2'06 Na 2 0.
46
Therefore 2-06 Na 2 + 071 Na 2 = 277, the amount of Na 2 used,
and 7'25 Na 2 - 277 - 4-48 Na 2 required.
We have now to combine this 4'48 Na 2 with S0 3 :
62 parts Na 2 require 80 parts S0 3 .
4'48 (Na 2 remaining) x = 578 S0 3 required,
\) 2i
and 578 + 4-48 = 10-26 Na 2 S0 4 .
We have thus used up our soda, 073 S0 3 for K 2 S0 4 and 578
S0 3 for Na 2 S0 4 ( = 6-51 S0 8 ), leaving (52-29-6-51) 4578 SO,.
We have now to combine the S0 3 with lime (CaO) :
80 parts S0 3 require 56 CaO.
12
178 THE BREWER'S ANALYST
e*/
Therefore 45'78 (remaining S0 3 ) x = 32'04 CaO required,
80
and 32-04 CaO + 4578 S0 3 =77'82 CaS0 4 .
This disposes of our S0 3 and leaves us with (36'33- 32-04)-=
4'29 CaO :
56 parts CaO require 44 parts C0 2 .
Therefore 4-29 (remaining CaO) x li = 3'37 C0 2 ,
and 4-29 CaO + 3'37 C0 2 = 7*66 CaC0 3 .
(There are no acids left to combine with the magnesia, which
must therefore exist as carbonate) :
40 parts MgO require 44 parts C0 2 .
Therefore 10-15 (amount of MgO) x = 11 '16 C0 2 ,
40
and 10-15 M 9 0+ 11*16 C0 2 = 21'31
We have already estimated the alkalinity of the water both
before and after boiling, and seen that after boiling the alkalinity
is equal to 31-80 grains per gallon CaC0 3 ; the amount of
carbonates arrived at by calculation may therefore be checked by
this figure.
In our combination results we have 21*31 grains per gallon
carbonate of magnesia :
88 parts MgC0 3 have the same alkalinity as 100 parts CaC0 3 .
So 21-31 x^ = 24-21 asCaC0 3 .
08
Therefore actual CaC0 3 7-66-1- 24'21 = 31-87 grains of alkalinity,
and by our test 31*80 grains.
The composition of the water is therefore as follows :
TYPE I.
Total solids . . . .139*920 grains per gallon.
Saline residue . . . 125-400
Organic and volatile matter . 14*520 ,, ,,
Lime 36*330
Magnesia .... 10-150
Sulphuric acid . . . 52*290 ,,
Chlorine . . . 2 -380
Iron 0-098
Soda 7-250
Potash .... 0-860
Silica . 0-840
METHODS OF ANALYSIS 179
Nitrogen as nitrates and nitrites :
Nitric acid .... 1 -250 grains per gallon.
Nitrous acid . . . Nil.
Organic matter :
Free or saline ammonia . 0'122 parts per million.
Albuminoid ammonia . . 0*062 ,, ,,
Oxygen required to oxidise organic matter :
15 minutes . . . OO25 parts per 100,000
4 hours . . . 0-095 ,,
MOST PROBABLE COMBINATION.
Sodium chloride (NaCl) . . 3'90 grains per gallon.
Potassium sulphate (K 2 S0 4 ) . 1-59 ,,
Sodium nitrate Na(N0 3 ) 2 . . 1'96
Sodium sulphate (Na 2 S0 4 ) . . 10'26
Calcium sulphate (CaS0 4 ) . . 77'82
Calcium carbonate (CaC0 3 ) . 7'66
Magnesium carbonate (MgCO s ) .21-31 ,, ,,
Iron oxide (Fe 2 3 ) . . . 0-09
Silica (Si0 8 ) . . . 0-84
Saline residue . . 125'43
Saline residue found = 125 '40 grains per gallon.
TYPE II.
We will now take a typical analysis of a water suitable for mild
ale production, the analytical figures of which have been deter-
mined as follows :<
Silica . . . .0-26 grains per gallon.
Iron oxide . . . 0*24 ,,
Lime .... 9'79
Magnesia . . . 0'43
Soda .... 0-97
Chlorine . . I'll
Sulphuric acid . . 2'62 ,,
We first take the sodium (Na 2 = 0'97) and calculate it back
to Na :
62 parts Na 2 contain 46 N a.
Therefore 0'97 (amount of Na 2 0) x = 0'71 Na.
62
We combine this with chlorine :
23 parts Na require 35'5 parts Cl.
180 THE BREWER'S ANALYST
So 0-71 (amount of Na)x~-Hl Cl required,
and 0-71 Na+1-11 C1 = 1'82 NaCl.
This disposes of our soda and chlorine (these amounts just
saturating one another). We have neither potash nor nitric acid,
so we proceed to combine sulphuric acid (S0 3 ) with lime (CaO) :
80 parts S0 3 require 56 parts CaO.
Therefore 2 '62 S0 3 x = 1-83 CaO required,
80
and 2-62 SO 8 + 1'83 CaO = 4*45 CaS0 4 .
Our CaO equalled 9 "79, and as we have used 1*83 parts of it to
form CaS0 4 , we have 7 '06 left, which we combine with C0 2 :
56 parts CaO require 44 parts C0 .
Therefore 7'96 (remaining CaO) x i| = 6'25 C0 2 ,.
ob
and 6-25 C0 2 + 7'96 CaO =14*21 CaC0 3 .
We next combine magnesia (0'43) MgO with C0 9 :
40 parts MgO require 44 parts C0 2 .
Therefore 0'43 (amount of MgO) x ^ = 0'47 C0 2 .
and 0-43 MgO + 0'47 C0 2 = 0'90 Mg*C0 3 .
The composition of the water is therefore :
Sodium chloride (NaCl) . . 1*82 grains per gallon.
Calcium sulphate (CaS0 4 ) . . 4'45
Calcium carbonate (CaCO 3 ) .14-21
Magnesium carbonate (MgC0 3 ) . 0"90 ,,
Iron oxide (Fe 2 3 ) . . " . 0*24
Silica (SiO 8 ) . . . 0'26
TYPE III.
We finally take a typical analysis of a water suitable for stout
and porter production, the analytical figures of which have been
determined as follows :
Silica .... 0-22 grains per gallon.
Iron .... 0-24
Lime . . . 13-13
Magnesia . . . 1"91
Soda .... 18-62
Chlorine . . . 23'81
Sulphuric acid . . 3 '6 7
METHODS OF ANALYSIS 181
We first take the soda, which is expressed in our analysis as
Na 2 0, and calculate it back to Na]:
62 parts Na 2 contain 46 parts Na.
18-62 (amount of Na 2 0) x 1? = 13-81 Na.
o 2i
We now combine this with chlorine :
23 parts Na require 35-5 Cl.
OK.K
Therefore 13 "81 Na x - t - = 21 '31 Cl required,
aw
and 21-31 Cl + 13'81 Na = 35*12 NaCL
We have thus used up our sodium and have (23*81 Cl - 21 '31 Cl)
2-50 Cl left.
We have now to combine this Cl with calcium (Ca) :
35-5 parts Cl x 2 = 71 parts Cl, which combine with
40 parts Ca to form CaCl.
Therefore 2-50 (Cl remaining) x ^ = 1 -40 Ca required,
and 1-40 Ca + 2'50 Cl = 3'90 CaCL
We now take our S0 3 (3'67) and combine it with lime (CaO) :
80 parts SO 3 require 56 parts CaO.
Therefore 3'67 (S0 3 ) x ~ = 2'56 CaO required,
and 2-56 CaO + 3'67 S0 3 = 6'23 CaSo 4 .
Of our original lime 13'13 we have bound 1'40 with chlorine
to form CaCl and 2 56 with S0 3 to form CaS0 4 : 1'40 + 2'56 = 3'96
and 13-13-3 96 = 9-17.
Lime remaining :
56 parts CaO require 44 parts C0 >2 .
Therefore 9-17 (lime remaining) x -=7'20 C0. 2 ,
and 9-17 (lime) + 7'20 C0 2 =16'37 CaC0 3 .
We now finish with the magnesia (1'91 MgO) :
40 parts MgO require 44 parts CO 2 .
Therefore 1'91 (amount of MgO) x - 2-10 C0 2 ,
and 1-91 MgO + 2'10 C0 2 = 4'01 MgC0 3 .
182 THE BREWER'S ANALYST
The composition of the water is therefore :
Sodium chloride (NaCl) . . 35'12 grains per gallon.
Calcium chloride (CaCl 2 ) . 3 '90
Calcium sulphate (CaS0 4 ) . . 6'23
Calcium carbonate (CaC0 3 ) . 16*37
Magnesium carbonate (MgC0 3 ) . 4*01 ,, ,,
Iron oxide (Fe 2 3 ) . . . 0'24
Silica (SiOj) . . . . 0-22
The foregoing calculations can all naturally be shortened by
cancelling and the use of factors, but are given in detail so as to
be explicit to the student.
BISULPHITE OF LIME ANALYSIS.
The following are the determinations to be made :
1. Specific gravity.
2. Total sulphurous acid (free and combined).
3. Sulphuric acid.
4. Lime.
5. Magnesia.
6. Chlorine.
7. Iron.
8. Hyposulphites.
The bisulphite should be drawn from the cask through a
freshly bored peg-hole into a clean dry stoppered bottle, the
stopper being tightly fitted and the contents well shaken before
use. The bottle should be immersed in cold water or the con-
tents otherwise brought to 60F. (15-5 C.) before commencing
the analysis, and owing to the rapidity with which the sulphite
oxidises when exposed to the air and the volatilisation of S0 2 , it
is essential to perform each experiment as quickly as possible.
1. Specific Gravity. This is determined in the ordinary
manner by the aid of the specific-gravity bottle (fig. 36,
p. 33).
2. Total SulphUPOUS Acid. Gravimetric Method. The total
sulphurous acid may be determined either gravimetrically or volu-
metrically. In the former case the sulphurous acid, both free and
combined, is first oxidised into sulphuric acid and then determined
by the aid of baric chloride, the amount of sulphurous acid being
calculated from the weight of the precipitated baric sulphate.
We have first, however, to determine the weight of baric sulphate
METHODS OF ANALYSIS 183
which may be due to any sulphuric acid existing as such in the
bisulphite owing to oxidation, and deduct this from the total
weight of baric sulphate, calculating the difference into sulphurous
acid. We therefore proceed as follows :
Add to a beaker about 120 c.c. distilled water and about
10 c.c. bromine and stir well. Now measure 20 c.c. of the
bisulphite in a 200 c.c. flask and make to mark with distilled
water =10 per cent, solution. Run 10 c.c. of this 10 percent,
solution into the previously prepared bromine water = 1 c.c. of
bisulphite. The solution should now be distinctly brown ; if it is
not, add a few more drops of bromine and stir well. Now add
2 or 3 c.c. hydrochloric acid and boil the solution over a Bunsen
name until the whole of the free bromine is volatilised and the
solution is free from colour. The sulphurous acid has now been
oxidised into sulphuric acid, the bromine having decomposed
the elements of water and combined with the hydrogen to form
hydrobromic acid, whilst the sulphurous acid has seized the
liberated oxygen.
The sulphuric acid is now determined in the solution in exactly
the same manner as in water analysis, and the sulphurous acid
calculated after deducting the BaS0 4 due to sulphuric acid natur-
ally present in the sample.
Example. To the colourless boiled solution a few drops of baric
chloride are added, the solution further boiled for a minute or two
and then set aside in a warm place until the baric sulphate has
settled and the supernatant liquid is perfectly clear. The solu-
tion is then filtered, the filter paper repeatedly washed with hot
distilled water, dried, folded, and ignited in a tared crucible.
The crucible is then cooled under the desiccator and weighed.
The weight is found, say, to be :
Weight of crucible + BaS0 4 . . 6 '801 grams.
Weight of crucible . . . 6'540
BaS0 4 . . 0-261
It is found, however, that 1 c.c. of the bisulphite contains '007
BaS0 4 due to sulphates naturally present, so 0'261 - 0'007 = 0*254
BaSO 4 from sulphurous acid (S0 2 ) in 1 c.c.
As shown under Water Analysis, the atomic weight of baric
sulphate is 233, and that of sulphurous anhydride 64, so that
every 233 parts of BaS0 4 correspond to 64 parts S0 2 , or 1 gram
to 0-2746 = 0-06974 gram SO 2 in 1 c.c. bisulphite or 6'974 per
100 c.c.
184 THE BREWER'S ANALYST
Let us now confirm this gravimetric method by the volumetric
process.
This depends upon the beautiful and sensitive iodine reaction
already fully described under Sulphurous Acid (p. 149).
Measure 20 c.c. of the bisulphite into a 200 c.c. flask and
dilute to mark with recently prepared distilled water. Now
take 10 c.c. of this solution in a porcelain dish, add a few drops
of gelatinised starch solution (footnote, p. 172), and titrate with
N
-- iodine until a blue colour makes its appearance and becomes
permanent on standing.
N
Suppose the amount of iodine used = 2J c.c. Then, as each
c.c. of iodine corresponds to 0*0032 sulphurous acid 21 x 0-0032 =
0-0672 S0 2 in 10 c.c. dilute bisulphite ( = 1 c.c. of bisulphite),
and 0-0672 x 100 = 6'72 S0 2 per 100 c.c. as against 6 '97 per 100
c.c. found gravimetrically. If only the volumetric method is em-
ployed, then it becomes necessary to confirm the result by
N"
titration with iodine, by using an excess of the latter and
N
performing a second titration by the use of ^ thiosulphate as
exemplified under Sulphurous Acid, p. 149.
3. Sulphuric Acid. Add about 10 c.c. concentrated hydro-
chloric acid and about 100 c.c. distilled water to a small boiling
flask and boil for a few minutes to expel the air from the flask
and free oxygen from the water. Now add 50 c.c. of the bi-
sulphite and boil for about 15 minutes, or until the evolved
steam no longer smells of sulphurous acid. Transfer the contents
of the flask to a beaker, dilute slightly with distilled water, add
about 10 c.c. baric chloride solution, and set aside in a warm
place until the baric sulphate has precipitated and the super-
natant liquid is clear. Now filter, wash with hot distilled water,
dry, ignite, cool, and weigh as baric sulphate (BaS0 4 ).
Example :
Weight of crucible + ash . . . 6*797 grams.
Weight of crucible .... 6'500
BaS0 4 . . . 0-297
The atomic weight of BaS0 4 is 233, and that of sulphuric
anhydride (SO,) 80. 233 parts of BaS0 4 therefore correspond
Qf\
to 80 parts of sulphuric anhydride, =-343, so that
METHODS OF ANALYSIS 185
0-297 x -343 = -1018 S0 3 in 50 c.c. bisulphite x2 = 0'203 per
100 c.c.
4. Lime. Make a 10 per cent, solution of the bisulphite by
taking 20 c.c. and making- up to 200 c.c. with distilled water.
Measure 20 c.c. of this 10 per cent, solution ( = 2 c.c. bisulphite)
into a beaker, add about 150 c.c. distilled water and about 10 c.c.
animonic oxalate, about the same quantity of ammonic chloride,
and about the same quantity of ammonic hydrate. Gently warm
the liquid and allow to remain at rest for about 3 hours and
then filter. (The filtrate is required for the following magnesia
estimation.) Wash the precipitate with hot distilled water, dry,
ignite, cool, recarbonate, heat gently, cool under desiccator, and
weigh as calcic carbonate (CaC0 3 ).
Example :
Weight of crucible + ash . . . 6'588 grams.
Weight of crucible .... 6 '500
0-088
0-088 x -56 = 0-049 CaO in 2 c.c. bisulphite and x 50-2-450
lime (CaO) per 100 c.c.
5. Magnesia. To the filtrate from the previously described
lime estimation add about 10 c.c. ammonic or sodic phosphate
and about a like amount of ammonic hydrate ; stir well and set
aside for 6 hours. Now filter, wash the precipitate with dilute
ammonia, dry, ignite, cool, and weigh as pyrophosphate of
magnesia 2(MgO)P 2 5 .
Example :
Weight of crucible + ash . . . 6 '5 11 grams.
Weight of crucible . . . 6-503
008
The atomic weight of 2(MgO)P 2 5 is 222, and that of 2MgO 80,
so that 222 parts of pyrophosphate correspond to 80 parts of
80
magnesia, ^-='36. So that O'OOS x -36 = -00288 magnesia in
222
2 c.c. bisulphite, which x 50 = 0' 1 50 per 100 c.c.
6. ChlOPine. Take 25 c.c. of the bisulphite in a platinum or
porcelain dish, evaporate to dryness over the water bath, moisten
the residue with a little distilled water and again evaporate to
dryness, repeating the moistening with distilled water and
evaporation to dryness three times. Now dissolve the residue
with hot distilled water and transfer to a filter paper and filter
186 THE BKEWER'S ANALYST
collecting the filtrate in a clean porcelain dish. Wash the
precipitate with hot distilled water and collect the filtrate in the
same porcelain dish. Now add to the filtrate one or two drops
of potassic chromate and titrate with a standard solution of
argentic nitrate (p. 137) as in Water Analysis, p. 160.
Example. 25 c.c. of the bisulphite took 1'7 c.c. of argentic
nitrate, so that as each c.c. of the silver solution corresponds to
O'OOl gram of chlorine, I '7 x '001 = "0017 in 25 c.c. x 4 = '0068
gram Cl per 100 c.c.
To bring this to terms of common salt (sodic chloride) the
atomic weight of chlorine (Cl) is 35 '5, and that of sodic chloride
(NaCl) 58-5.
Every 35*5 parts of chlorine therefore correspond to 58 '5 parts
58'5
of sodic chloride = 1'645, so we multiply by the factor 1'645
oo'D
or, roughly, by l'65-O'Oll NaCl per 100 c.c.
7. Iron. Measure 20 c.c. of the bisulphite into a small
beaker, add about 50 c.c. distilled water and a few drops hydro-
chloric and nitric acids and boil until the evolved steam no
longer smells of nitrous or sulphurous fumes. Now cool, transfer
to a 100 c.c. flask and dilute to mark ( = 20 per cent, solution).
Of this solution take 50 c.c. in a Nessler tube, add a drop or two
of potassic ferrocyanide, and stand for a minute or two, when,
if iron is present, a blue colour will have developed varying in
intensity with the amount of iron. Now take a second Nessler
tube, add 50 c.c. distilled water, a drop or two of potassic ferro-
cyanide, and run in from a burette a standard solution of iron
(p. 137), until the colour, which develops on standing for a few
minutes after each addition of iron, exactly matches in intensity
that of the bisulphite solution.
Suppose the quantity of iron solution used equals 30 c.c. ; then,
as each c.c. of iron solution is equivalent to O'l milligram of iron
30 x O'l = '30 milligram of iron, and "30 x 5 = 1*50 milligram iron
in the 100 c.c. of 20 per cent, bisulphite solution. Therefore
1-50 x 5 = 7'50 milligrams per 100 c.c. of the bisulphite, or '0075
gram.
It is usual, however, as in water analysis, to express the iron
as ferric oxide (Fe 2 3 ), so that as 160 parts of Fe 2 3 correspond to
112
112 parts of iron . = -7. We multiply '0075 x '7 and obtain
iron as '0052 (Fe 2 3 ) per 100 c.c.
8. Hyposulphites. These bodies, if present, render the
bisulphite utterly unfit for use. It is therefore only necessary
METHODS OF ANALYSIS 187
to detect their presence, no estimation being necessary; and, if
found to exist, the bisulphite should be at once condemned as unfit
for use.
Their detection is a simple matter ; all that is needed is to add
to the bisulphite concentrated hydrochloric or any strong mineral
acid and raise to the boil, when, if hyposulphites exist, a yellow
precipitate of sulphur is thrown down. The precipitate should
not be confused with one of a white colour sometimes obtained
by this treatment. .
Combinations. We have now to combine acids and bases,
our determinations being :
Per cent.
Total sulphurous acid . . . 6'974
,, sulphuric acid .... -203
lime 2-450
,, magnesia '150
chlorine '006
,, iron -005
We first take the '203 sulphuric anhydride (S0 8 ) and saturate
it with lime equivalent :
80 parts S0 3 combine with 56 parts CaO.
Therefore ' 20 |j * 56 = '142 CaO.
(142 + -203) = '345 per cent. CaS0 4 (calcic sulphate).
142 parts of lime having thus been disposed of, the remainder
(2'450 "142) = 2*308, so that this now requires to be combined
with sulphurous acid (S0 2 ), the atomic weight of which is 64.
Therefore ^ u g x ^ . 2'602 S0 2 ,
_x 64
56
and 2-602 + 2-308 = 4-91 per cent, calcic sulphite (CaSO 3 ).
Having thus completely saturated the lime, we have now to
deal with the magnesia and combine this also with sulphurous
acid. The atomic weight of MgO is 40, so that - 5 * 64 = -24
S0 2 , combining with '15 MgO to form '39 per cent, magnesic
sulphite (MgS0 3 ). The total amount of sulphurous acid is 6 -9 74
per cent., and the amount required to saturate the lime (2*60) and
magnesia ('24) added together = 2 '84, which deducted from the
total = 4'13 per cent, free sulphurous acid. The full analysis
is therefore as follows :
188 THE BREWER'S ANALYST
Analysis of Bisulphite of Lime expressed on 100 parts by volume.
Specific gravity . . . 1069-0
Total sulphurous acid . . 6 '97 per cent.
Free sulphurous acid . . 4 '13 ,,
Combined sulphurous acid . 2 '84 ,,
Calcic sulphate . . . 0-34 ,,
Calcic sulphite . . . 4'91
Magnesic sulphite . . 0*39 ,,
Sodic chloride . . O'Oll
Ferric oxide . . . 0*005
Hyposulphites . . . Nil.
The results of analysis are frequently required to be expressed
on 100 parts by weight instead of on 100 parts by volume as
above. In such instances, taking the present analysis as an
example, the results would work out thus :
The specific gravity of the bisulphite was found to be 1069 ;
the actual weight of 100 c.c. is therefore 106-9 grams, or 100
parts by volume equal 106 '9 parts by weight; therefore each
100
figure of the analysis multiplied by - expresses the results
106*9
in percentage on the latter.
Example :
Total SO 2 = 6*97 in 100 c.c.
Therefore ^ X - 100 == 6-52 per cent, total S0 2 by weight.
Free S0 2 = 4*13 in 100 c.c.,
= 3-86, and so on with each item.
106*9
The results therefore stand :
Analysis of Bisulphite of Lime expressed on WO parts by weight.
100 parts weight . . . 106*9 grams.
Total sulphurous acid . . 6*52 ,,
Free sulphurous acid . . ' 3*86
Combined sulphurous acid . 2*65 ,,
Calcic sulphate . . . 0*30
Calcic sulphite . . . 4*59 ,,
Magnesic sulphite . . 0*36 ,,
Sodic chloride . . . 0*11
Ferric oxide .... 0'004
Hyposulphites . . . Nil.
METHODS OF ANALYSIS 189
SOLID SULPHITES.
Calcic Sulphite. Sodic Sulphite. Potassic Sulphite.
CALCIC SULPHITE.
The determinations to be made are :
Lime.
Sulphurous acid.
Sulphuric acid.
Iron.
The same general methods are adopted as those given for
bisulphite of lime, half a gram of the sulphite being dissolved in
distilled water and made up to 100 c.c. at 60 F. (15'5 C.) and
the analysis proceeded with as described.
In some instances it will be found that there is a proportion
of the lime CaO or CaCO 3 uncombined with acid, the presence
of which is indicated when the acids fail to satisfy the base ; and,
if desired, a determination of the alkalinity or carbonic acid may
be made, as described under Water Analysis, to check such result.
Samples of soluble or precipitated sulphite contain an equivalent
of water of crystallisation, the sulphite existing as CaS0 3 + H 2 ;
with such, the analytical results will of course not add up to 100
parts, even when the moisture has been determined, because the
water of crystallisation is not expelled, except at higher tempera-
tures than can be employed without decomposing the salt.
SODIC AND POTAHSIC SULPHITE.
With these it is only necessary to determine the sulphurous
and sulphuric acids and ferric oxide. The bases are not usually
determined, but if required they can be done as described under
Water Analysis.
MALT ANALYSIS.
The following are the determinations to be made :
1. Extraneous matters.
2. Defective corns.
3. Weight per bushel.
4. Steely corns and modification.
5. Specific gravity of 10 per cent, solution.
6. Extract per quarter.
7. Dry extract per cent.
190 THE BREWER'S ANALYST
8. Saccharification period.
9. Specific rotatory power of mash wort.
10. Acidity.
11. Moisture.
12. Matters soluble in cold water
13. Ready -formed soluble carbohydrates.
14. Colour of wort.
15. Mineral matter or ash.
16. Total proteids or albuminoids.
17. Soluble proteids or albuminoids.
18. Insoluble proteids or albuminoids.
19. Diastatic power.
Sampling*. Care should be exercised in obtaining an average
sample of the malt. With malt heaped up on the kiln or in store,
a little should be taken from different parts of the bulk. With
malt delivered in sacks, a sample from the top, middle, and
bottom of several sacks should be selected. The well-known
FIG. 65.
corn sampler (fig. 65) may be conveniently employed for this
purpose. The various portions selected in this manner from 3,ny
one particular class of malt should then be well mixed together
and about 200 grams taken and screened.
1. ExtFaneOUS MattePS. A very simple and efficient screen
for this purpose is the " Boby," which consists of a series of iron
rods fixed together in the form of a frame which, enclosed in a
box, may be given a fast or slow reciprocatory motion by hand
at the manipulator's desire, or the well-known miniature screen
shown in fig. 66. The refuse such as rootlets, tail corn, and other
bodies falls through the mesh, from whence it may be collected
and weighed. Thus, if we take a definite quantity of malt, screen
it, and weigh the extraneous bodies, we naturally arrive at the
quantity originally present in the sample. In one instance 200
grams were taken and screened; the screenings, together with
seeds, stones, and other rubbish picked from the malt, weighed
2-4 grams = 1 '2 per cent, extraneous matters.
2. Defective Corns. These include corns which are crushed,
mouldy, half corns or extremely minute in size. Five hundred
METHODS OF ANALYSIS 191
corns are promiscuously separated from the sample and the per-
centage ascertained.
3. Weight pep Bushel. It is necessary to remember that
malt just off the kiln is warm, and that when in this condition it
is impossible to obtain its correct weight. It is wise in fact not
to attempt the weighing of any malt until it has been off the kiln
for at least 24 hours. The weight is ascertained by the instru-
ment known as the " chondrometer " (fig. 67), which consists of a
balance provided with a small measure to hold about a half-pint.
The measure is filled with an average screened sample of the
bulk from which the impurities such as stones, etc., have been
removed ; the surface is levelled with the " strike " and the weight
ascertained. The weights bear the same proportion to the measure
FIG. 66. FIG. 67.
as pounds do to the bushel, so the weight in pounds per bushel
is read off directly. 1
4. Steely Corns and Modification. Imperfectly vegetated
or kiln-dried malts contain varying proportions of steely corns
which are resistant to the bite and usually roughly detected in
this manner. If selected and cut in two, it will be found that
the starch has a peculiar cast and a vitreous or glassy appearance.
It is advisable to estimate the steely corns, and this is most
readily performed by means of the well-known "farinator"
(fig. 68), which cuts through 50 or 100 corns with one stroke of
the knife. Further, it has been found that light will pass through
glassy but not through mealy corns. From this fact the instru-
ment designated the " diapharioscope " (fig. 69) has been con-
structed It consists of a box made of sheet metal, in the
interior of which is placed a petroleum, gas, or electric lamp. The
roof of the apparatus is provided with a number of slits, into each
1 The results obtained must be regarded more as comparative values than
reliable determinations of the actual bushel weight of the corn.
192 THE BREWER'S ANALYST
of which a corn of malt is placed. The quality of the malt is
then judged from the relative transparency of the corns.
In examining malt by either the farinator or diaphanoscope, it
is usual to operate on 500 corns. These are divided into three
classes floury, vitreous, and semi-vitreous ; the numbers thus
obtained, divided by five, giving the respective percentages of the
different classes.
The old-fashioned " sinker " test was formerly much in vogue,
and was considered capable of testing the percentage of semi-
grown or dead corns in a sample of malt. It originated from
a paragraph in Edward Lisle's work entitled Observations in
FIG. 68. FIG. 69.
Husbandry, 1757, p. 205, where he states: "My maltster sent
me malt which my butler was not pleased with. He said there
were many grains in every handful of it which were not malted
at all, and many grains that were but half-malted, of which I
might be satisfied if I made trial in water ; for the corns which
were not malted at all would sink to the bottom, and the half-
malted grains would swim on end like a fishing quill. I called for
a basin of water to make the experiment and found it to be true."
The test is carried out by counting three or four separate
hundred corns, or measuring off 300 or 400 corns in a small
thimble or measure, 1 throwing the corns into a tumbler of water,
well stirring for about half a minute, and counting those that
sink and those that float perpendicularly.
The principle of the test depends upon the fact that corns
1 This method is much quicker than counting, and the error in the number
taken does not amount to more than a few corns, being inappreciable in
the result.
METHODS OF ANALYSIS 193
which contain their starch, or a portion of it, in an unmodified,
steely, or vitreous state, have a specific gravity greater than water,
and sink when immersed. There are of course gradations in this
difference of specific gravity, and many corns will be found to float
in a perpendicular position which, on examination, may be found
to have steely tips, but in which the balance of specific gravity
between the friable portion of the corn and its steely part is so
close as to prevent its subsidence. Also a shrivelled corn in which
the plumule may have grown completely out, and yet not com-
pleted the whole of its modification, may occasionally be found
floating. When this occurs it is in the case of a thin corn in
which the growth of the plumule has apparently been too great
to be sustained by the ordinary available food supply. A large
portion of the cell walls, being in a steely state, has remained
unmodified, and the embryo has used up the reserve starch along
the dorsal side of the grain, depleting the endosperm cells.
During the kilning process the corn becomes unduly shrivelled,
and sometimes leaves sufficient air-space beneath the husk to turn
the scale in favour of its floating.
Meacham, some two or three years ago, suggested the use of a
5 per cent, solution of methylated spirit in place of ordinary water ;
the decrease in specific gravity of the water thus produced bringing
down those corns which, by reason of their being very slightly
steely at the tips, otherwise float perpendicularly in ordinary water.
A further test is that of immersing the malt in toluol. 1 The
specific gravity of malt immersed in this solution varies from 0'95
to I'l; and, generally speaking, malts with specific gravity less
than 1 '0 are well modified, whilst those showing a specific gravity
above this are not considered to be well modified.
On the whole, it may be stated that the sinker test with water
or aqueous methylated spirit, and the method of judging modifica-
tion from the specific gravity found by the aid of toluol, are
decidedly unsatisfactory. The percentage of sinking corns varies
so much from day to day, and is dependent upon so many condi-
tions, that it is dangerous to condemn a sample of malt which
may be very good from a chemical point of view and bad if done
1 Toluol, or, as it is better known, toluene, is a hydrocarbon of the aromatic
series, with a boiling point of 231 '8 F. (111 C.) and a specific gravity 882 '4
(water = 1000). It is used for taking the specific gravity of malt in precisely
the same way as the specific gravity of a solid is usually taken with water, a
method to be found in any elementary text-book on physios. It is necessary
to use toluene instead of water when dealing with malt, because of the solvent
action of the latter on certain constituents of the malt. Toluene, it is stated,
has no solvent action on the malt.
13
194
THE BE EWER'S ANALYST
by either of these methods. Tt is decidedly more advantageous
and reliable to count or measure out several separate hundred
corns and examine the degree of growth of the acrospire of each,
so arriving at fair conclusions as to irregularity of growth or
otherwise of the sample ; whilst for steely, vitreous, or dead corns
examination should be made by means of a penknife, separating
out the dead or idle corns, vitreous corns, steely-backs, and steely-
tips, classifying them in percentages.
Examination by means of the diaphanoscope or farinator is,
however, reliable, so that we may resort to these methods of
procedure and discard the sinker or specific-gravity tests as
obsolete and next to useless.
The acrospire in the corns of good malt should be well and
evenly grown, the average length being between two-thirds and
three-quarters up the back. There should be few corns in which
it either pierces the end or fails to extend to more than half up.
As the vitality of barley is the chief characteristic when judging
its quality, so the growth of malt is also the main factor in con-
sidering its positive and comparative value.
The word growth has ;i wider significance than vitality ; for, al-
though no barley can possibly possess too much vitality, malt which
is grown too much is of greatly reduced value. Any corn which
remains unvegetated is not malt, but barley, and the paramount
importance of the growth of the acrospire is consequently obvious.
To detect regularity in growth, a number of corns are taken
promiscuously from a sample, say several lots of 200 each, and
the number of corns which have grown to the various different
lengths, or grown out, are determined by inspection ; and the
different groups of figures so obtained, divided by two, give the
percentages. The following typical illustrations, giving per-
centages of growth, show the value of uniformity in samples from
careful examination.
PERCENTAGE or GROWTH.
Good Malt.
Medium Malt.
Bad Malt.
Acrospire grown out .
,, I up back .
;: :: ! ;: :
, , started
1
9 4
64 80
26 9
1 3
1
3
7 4
64 79
14 11
6
3 2
12 26
19 21
42 28
17 9
1
2
Dead corns ....
2
3 4
8 15
100 100
100 100
100 100
METHODS OF ANALYSIS 195
Grinding". Much controversy has taken place within recent
years as to the degree of fineness to which the malt should be
ground. Some prefer to grind to powder, others only to a coarse
state such as is usual when grinding on a practical scale in the
brewery. It naturally follows that two analysts, one grinding
the malt to powder, the other only grinding so that the grist
resembles the degree of fineness which is usual in practical opera-
tions, obtain very dilt'erent results. In fact a difference of 3 or
4 Ibs. per quarter results in the amount of extract obtained by
grinding in both ways.
The old method of grinding, and at present largely practised,
is by the use of the coffee-mill ; and naturally, as the fluted
cone is fixed or screwed up in these mills to different degrees,
hardly two mills grind to the same degree. In any case, how-
ever, where such mills are employed, they should be arranged so
that the interior may be cleaned before grinding.
In view of the fact that different analysts obtain different
results by reason of the variance in the degree of fineness in
grinding, it became obvious that a fixed standard was desirable,
and some years ago it was agreed by many analysts to grind the
malt to the finest powder. By this method, however, the extract
obtained is far and away greater than can be obtained from the
malt in practice ; and, more particularly, steely corns which give
little or no extract in the ordinary manner are, upon being
reduced to powder, rendered amenable to the influences of heat
and diastase.
In order to avoid these drawbacks, that is to say, enable
the operator to grind to any desired degree of fineness and
express the degree so that it may be known under what
standard in this direction his analysis is conducted, Messrs
Seek Bros., Ltd., of Dresden, Germany, some few years ago
introduced their now well-known "Seek mill" for use either
in the brewery or for laboratory purposes, the latter being shown
in fig. 70 (p. 196).
In this mill the malt is crushed between two steel rollers as in
actual practice. One of them is mounted in stationary bearings,
whilst the other is capable of adjustment by means of an eccentric
and lever, the adjustment being indicated on a scale graduated
from to 50.
The following figures represent the results obtained with the
Seek mill by grinding to varying degrees, and they illustrate
not only the wide difference in extract obtainable from one and
the same malt, but also the fact already referred to, that in the
196
THE BREWER'S ANALYST
case of a steely malt these differences will be much greater than
in that of a tender sample.
EXTRACTS PER 336 LBS.
Ground
to flour.
Seek 10.
Seek 20.
Seek 30.
Seek 40.
Seek 50.
English malt tender
97-6 96-9
96-5
96-0
95-6
94-1
English malt fairly
98'4
97-6
967
96'2
951 94-0
tender
English malt very
93-9
92-0
91-5
89-8
87'5 85-0
steely
Californian malt . 91 "6
90-6
89-6
89-0
86-6
85-2
For laboratory purposes the mill is, as a rule, set at 25, this
being the standard adopted on the Continent.
There is this, however, to be said with regard to the grinding
of malt, that so far as
the consulting analyst is
concerned, with the Seek
mill he should state in his
analysis the degree he set
the mill to before grinding.
Whilst if a coffee-mill is
employed, he should grind
to powder, state this in
his analysis, and by no
means omit reference to
' the percentage of steely
corns, since these, as
before stated, with fine
grinding give extract.
With the analyst on
the brewery premises, if
FIG. 70. a Seek mill is employed
it should always be set at
the same degree ; whilst in the absence of such mill a coffee-mill
may be employed, since by its use the grain will always be ground
to the same degree and the evaluation of his malts will always
be judged from this and his comparisons uniformly drawn.
5. Specific gravity of 10 per cent, solution.
6. Extract per quarter.
7. Dry extract per cent.
METHODS OF ANALYSIS 19?
The method which has been most widely adopted in this
country for ascertaining the iirst and second of these estimations
is that proposed by Heron l in 1888, and modified somewhat
later, 2 which essentially consists as follows :
Measure 400 c.c. of distilled water and run the same into a
copper or enamelled beaker of about 1 litre capacity. Place the
beaker containing a thermometer in a water bath in which the
water is maintained by a thermostat (fig. 32, p. 27) at a constant
temperature of 150 F. (65*5 C.). While the water is heating,
weigh 50 grams of the screened malt in a small tared beaker ; add
three or four extra corns, grind in a coffee or Seek mill, transfer
the grist to the same beaker and again weigh, withdrawing grist,
if necessary, until exactly 50 grams are obtained.
When the 400 c.c. of water registers a temperature of 150 F.
(65*5 C.), add the 50 grams of grist and stir well with the
thermometer.
The miniature mash so made will shortly register an initial
temperature of 150 F. (65'5 C.), and should be maintained at this
temperature for 1 hour, which is more than ample time for
complete saccharification to be /effected.
8. Saeeharification Period. In order to record the time in
which complete saccharification has taken place, a drop of the
wort should be removed from the mash by the withdrawal of the
thermometer. The drop should be allowed to fall from the
thermometer upon a white surface such as a white tile then
cooled, and a single drop of iodine solution added. The absence
of a blue colour proves the absence of soluble starch, and hence
saccharification, so far as it is capable of being accomplished by
the infusion process, is complete, the modified starch of the malt
having been transformed. The test for starch should be carried
out 10 minutes after the mash has been made, and every 5
minutes afterwards, so long as a blue colour appears. It will be
found, however, that the saccharification period of malts is usually
from 20 to 30 minutes from the time the mash is made, so there
is no perceptible loss of extract by the withdrawal from the mash
of 4 or 5 drops.
Let us assume that the mash shows no blue colour with iodine
after 25 minutes' infusion : the saccharification period is therefore
25 minutes. At the end of 1 hour's infusion the beaker contain-
ing the mash is removed from the water bath and the temperature
of the contents raised to 160 F. (71 C.). The mash is then
1 Jnl. Soc. Chan. Ind. , vii. 259.
3 Jnl. Fed. Inst. Brewing, 1895, i. 116, and 1902, viii. 666.
198 THE BREWER'S ANALYST
transferred to a graduated glass jar through a copper or glass
funnel, the beaker carefully washed out with distilled water, and
the washings added to the graduated jar. The jar is then
immersed in cold water so that the contents may cool, and the
volume is finally made up to 515 c.c. at 60 F. (15'5 C.) with
distilled water. The stopper is then inserted in the neck of the
jar and the contents vigorously shaken and then thrown upon a
filter and the filtered wort collected in a clean dry beaker. Every
100 c.c. of the filtrate will now contain the extract derived from
10 grams of malt. The specific gravity of the wort is now taken
at 60 F. (15*5 C.) by means of the specific-gravity bottle (p. 33,
fig. 36), and from this the extract is obtained by subtracting 1000
(weight of water) and multiplying the remainder by 3*36. This
factor is arrived at as follows :
W = weight in Ib. of 1 quarter of malt.
V = volume of wort in c.c.
S = specific gravity of wort, less 1000.
p = quantity of malt in grams employed for the
determination.
E = extract in Ibs. per quarter.
F wvs
The E ~ 16665
when Y = 100 and p = 10.
T , p, W100S WS
E= 1000-10 = TOO ;
and if we assume that all malts weigh 336 Ibs. per quarter, then
E = S 3-36.
Example :
1029'! 1 is found to be the specific gravity.
Then 29'11 x 3'36 = 97'80 Ibs. extract per quarter.
and 29-11 4-3-86 ! = 7-541 dry solids per 100 c.c.
7-541 x 10 = 75-41 Ibs. dry extract per cent.
It will be noticed in the above experiment that, having taken 50
grams of grist and mashed with 400 c.c. of water, the bulk is
finally made up to 515 c.c. Heron's contention is that the
average volume of the grains from 50 grams of malt is 15 c.c.
On this assumption, therefore, his wort would measure 500
c.c., and by the use of the factor 3'36 he obtains in the most
direct manner the extract per 336 Ibs.
In January 1891 a paper was published by Briant in the
Analyst in which he takes exception to Heron's method for the
1 Solution factor, p. 57.
METHODS OF ANALYSIS 199
determination of the extract of malt. Brian t says : " This method
is not, in my opinion, entirely satisfactory ; Heron, it will be
remembered, makes up to a constant bulk of 515 c.c., yet there is
a very great variation in the amount of husk contained in malt
samples. This is abundantly evident to anyone who is accustomed
to the analysis of malts, and the amount of husk in a thin, foreign
barley malt is manifestly very much larger than that in a thin-
skinned, plump, bold English or Scotch barley malt. There is
thus an error introduced due to this difference for which Heron
has not made allowance."
Then he goes on to describe a method proposed by him which,
he says, eliminates the error arising from the difference in amount
of husk, and gives the true extract value of the malt sample.
Frew, in his paper on some notes on the analysis of malts, 1 a
paper which, under a plea for simplicity and uniformity, appears to
have been written with the set purpose of condemning in no measured
terms the analytical English methods and extolling to the skies
the German methods, says : " Heron's method of making up to a
final volume of 515 c.c., based as it is upon an assumption, would
be quite good enough if the volumes of the grains from all malts
were equal, but this we know is not the case. The extract
obtained by the use of this method from a heavy, thin-skinned,
well-modified malt cannot be compared with that from a husky
eastern malt of a somewhat steely character."
In answer to these criticisms, Heron 2 points out to what extent
the difference in volume produced by the grains from different
malts influence the extract. He says : "I have made extensive
analyses of a good many malts and of various qualities in my time,
and the smallest volume occupied by the grains, I found, was equal
to 13 c.c., whilst the largest never exceeded 17 c.c.
"Now, suppose we had a malt the grains of which exactly
occupied a volume equal to 15 c.c., and which gave an extract of,
say, 90 Ibs. ; and another malt giving likewise an extract of 90 Ibs.,
but whose grains occupied a volume equal to 17 c.c., but that the
total volume of the wort was made up to 515 c.c. what will be
the error introduced 1 ? Why, the enormous amount of-fO'34
Ib. On the other hand, with a malt whose grains occupy a
volume of only 13 c.c. and giving also, say, an extract of 90 Ibs.,
the error will be - 0'34 Ib. But, as a matter of fact, such malts
are very exceptional, and, in the great majority of cases, the error
does not amount to more than + or - O'l to 0'15, and I think
1 Jnl. Fed. Inst. Brewing, 8, 341.
2 Ibid.. No. 6, 1902,668.
200 THE BREWER'S ANALYST
such an error as this in the determination of the extract of malt
may very well be neglected."
From this controversy the reader may take it for granted that
Heron's method is to all intents and purposes as near perfection
as anything can be, and is adopted in preference to others which
introduce errors as great and in most cases greater than the
infinitesimal amounts shown by him from an extensive number of
experiments with different varieties and qualities of malt.
Determination of the "Full Theoretical" Extract.
The method of Heron's, already described, is employed to
determine the extract of malts when mashed under conditions
approximating to those in the brewery ; but the whole of the
possible extract is not obtained by such means, because even in
the case of tender malts a small amount of the starch present is
not hydrolysed, whilst with hard malts a large amount of starch
often escapes conversion.
A method frequently employed to obtain the total available
or "full theoretical " extract consists in treating the ground malt,
previous to mashing, with a cold-water infusion of oats.
Ripe oats (not kiln-dried) contain a considerable amount of the
enzyme cytase, and a cold-water infusion containing this enzyme
is employed to act on the malt for the purpose of liberating the
starch contained in the unmodified portions of the malt by
dissolving the cell walls enclosing the starch granules.
Digest 50 grams of oats, rather finely ground, with 250 c.c.
of cold water, for 3 or 4 hours, and filter. Mix 100 c.c. of the
filtrate with 50 grams of the ground malt experimented with,
and allow the mixture to stand at the room temperature for from
18 to 24 hours. Mash with 250 c.c. hot water, so as to obtain
an initial heat of 151 F. (66 C.), and keep at this temperature
for 1 hour. Transfer the mash to a 515 c.c. flask, and, after
cooling, make up to the mark and filter, and proceed to
determine the specific gravity of the wort in the usual manner.
Before calculating the extract a correction must, however, be
made for the specific gravity of the oat extract used in the
experiment. Determine the specific gravity of the oat extract
used, and subtract one-fifth of its excess gravity above 1000
from the specific gravity of the malt extract. The extract
derived from the malt can then be calculated in the usual
manner.
If the ordinary laboratory extract of the same malt has been
determined, the difference between the two extracts is a measure
of the modification of the malt. The so-called " coefficient of
METHODS OF ANALYSIS 201
modification " may be obtained by calculating the ordinary extract
as a percentage on the " full theoretical " extract. For instance,
if the ordinary extract of a malt is 87 '6, and the "full
theoretical " extract 95 '7, then
87-6x100
""95-7 '
the " coefficient of modification " of the malt, and the value is
comparable with the " coefficient of modification " of any other
malt found in a similar manner.
9. Specific Rotatory Power of Mash Wort. Raise a small
quantity of the 10 per cent, wort derived from the previously
made miniature mash, by Heron's method, to the boiling-point,
cool to 68 F. (20 C.), fill a 1 decimetre tube (100 mm.), place
in the polarimeter, and take a reading. Let us assume the
opticity in a 1 decimetre tube to be 9.
In cases where the wort is too dark in colour to enable a correct
polarimetric reading to be observed, such as when the malt
mashed is highly dried or when colour malts are employed, it
becomes necessary to decolorise the wort before polarising.
To do this take 50 c.c. of the boiled and cooled wort in a 100
c.c. flask, add a few drops of a 10 per cent, solution of lead
acetate, make to mark with distilled water, agitate, and filter
through a dry paper into a dry beaker. Fill a 1 decimetre tube
with this solution at 68 F. (20 C.) and polarise.
Example :
Opticity in 1 decimetre tube = 4 '5.
4'5x2 = 9 on 100 parts of wort, which on 7 '54 dry extract
in 100 parts of wort = 9 x ?. = [a] D 119-4.
10. Acidity. -This is determined by titrating 100 c.c. of the
10 per cent, wort at 60 F. (15 '5 C.) with sodic hydrate,
using litmus as indicator.
Example :
100 c.c. wort required 1'5 c.c. alkali.
1-5 x -009 = -0135 x 10-0-13 percent, on malt.
11. Moisture. For the determination of the moisture per-
centage in malt, it is advisable to have at hand three or four
small bottles of wide mouths and low build. The bottles should
be numbered by marking with a file, and their weights carefully
202 THE BREWER'S ANALYST
ascertained and entered in a convenient book. Marked counter-
poises are sometimes employed, such as are explained with the
specific-gravity bottle.
In estimating the moisture percentage 5 grams of the malt are
weighed, one or two extra corns added, and ground to a fine
powder in a coffee or Seek mill. The powder is then transferred
to the bottle and weighed, withdrawing grist, until exactly 5
grams are weighed. The bottle is then placed iu the water-bath
drying oven and left for 5 hours. This time should not be
exceeded, as, if so, the sample gains in weight owing to oxidation.
At the end of 5 hours the bottle is placed under the desiccator
to cool, 1 hour being the usual time allowed for this purpose.
The weight is now ascertained, the bottle again placed in the
drying oven for a further hour, again cooled under the desiccator,
and weighed.
Example :
Weight of bottle + 5 grams grist . 105'513 grams.
Weight after drying . . . 105 "396
Moisture in 5 grams . '117
117 x 20-2*34 per cent, moisture on malt.
Instead of weighing an exact 5 grams as per the foregoing
experiment, any convenient quantity may be weighed, and a rule
of three sum gives the result, thus :
Weight of bottle 100 '300 grams.
Weight of grist before drying . . ". 5'370
105-670
Weight of bottle + 5 '370 grams grist
after drying 105'544
126
Then A X J^ = 2 ' 34t P ep cent - moisture on malt.
5-370
The above-mentioned method of determining the moisture
percentage in malts is at present considered sufficiently satisfactory
for general purposes ; but in view of the fact that slight oxidation
of the constituents of the malt takes place during drying in this
manner, a much more accurate though complicated method has
been proposed, particulars of which may be found in a paper by
Ford and Guthrie, 1 which consists in drying the sample (ex-
1 Jnl. Fed. List. Brewing, No. 4, 1905, 326-332.
METHODS OF ANALYSIS 203
eluded from the ordinary air) in contact only with an atmosphere
of carbonic acid gas.
MATTERS SOLUBLE IN COLD WATER AND READY-
FORM KD SOLUBLE CARBOHYDRATES.
12. Matters Soluble in Cold Water. The extract for the
determination of matters soluble in cold water may be made so
as to answer also for the determination of colour value, next
described, and also, with dilution, for the estimation of diastatic
power and soluble albuminoids. With this in view, instead of
directly making a 10 per cent, solution as is usual, one of double
strength may be conveniently prepared thus :
Forty grams of the malt are weighed, ground to powder, and
transferred to a stoppered bottle of about 1 litre capacity.
200 c.c. of distilled water at 70 F. (21 C.) are next added, and
the bottle set aside for 3 hours at a temperature of 70 F.
(21 C.), shaking every half hour = 20 per cent, solution. 1
At the end of the 3 hours the extract is filtered, and
50 c.c. at 60 F. (15-5 C.) are added to a 100 c.c. flask and
boiled for 5 minutes. The contents are then cooled and made
to mark at 60 F. (15'5 C.) =10 per cent, solution. 2 This is
then filtered, and the specific gravity taken, from which the
matters soluble in cold water are determined by dividing the
specific gravity, less 1000, by the factor 3*86.
Specific gravity = 1006 '20 - 1000 = 6 '20
6'20 -f- 3-86 = 1-606 dry solids per 100 c.c.
and 1-606 x 10= 16*06 per cent, matters soluble in
cold water expressed on the malt.
1 From this 20 per cent, solution the colour i.s determined as in experiment
14, and a 5 per cent, solution is prepared from it for the determination of
diastatic power as in experiment 19.
Brown and Heron (Jnl. Chem. Soc., 1879, 596) showed that the addition
of sodium hydrate to the cold-water extract completely destroys diastatic
action ; and Ling, in view of this, proposes that the water, before being added
to the bottle, should be rendered slightly alkaline by the addition of 0'02 per
cent, caustic potash, or an equivalent amount of caustic soda or ammonia.
Morris has shown that there is no appreciable attacking and solution of starch
unless the 3 hours' limit of standing is exceeded. The author found that
whereas the matters soluble in cold water at the end of 3 hours were 15 '36
percent., at the end of 6 hours they were 20'33 per cent., and in 24 hours,
24 '74 per cent. ; so that time is a factor of great importance, and in no
instance should the 3 hour limit be exceeded.
' 2 From this 10 per cent, solution is also determined the ash as in experiment
15, and the soluble albuminoids as in experiment 17.
204 THE BREWER'S ANALYST
13. Ready-formed Soluble Carbohydrates. From the
matters soluble in cold water, which have been found to equal
16'06 per cent., the ready-formed soluble carbohydrates are
estimated by deducting the soluble albuminoids, mineral matter,
and acidity, thus :
Matters soluble in cold water . . 16 '06 per cent.
Per cent.
Soluble albuminoids . . . 2'66
Mineral matter . . . . T08
Acidity 0'13
3-87
12-19
The ready- formed soluble carbohydrates are therefore 12' 19 on
100 parts of malt, so that 10 grams malt contain 1*21 to corre-
spond with 100 c.c. of wort.
Where the albuminoids, mineral matter, etc., are not deter-
mined, the ready -formed soluble carbohydrates are always
approximately estimated by subtracting 4 from the matters
soluble in cold water.
14. ColOUP of Wort. In this determination it is necessary
that the wort should possess a gravity near the Excise standard
(1055 or 20 Ibs.), or be calculated to the same. The 20 per
cent, cold-water extract previously prepared for the determination
of matters soluble in cold water answers this requirement, as it
has been shown by Heron that as much colour is extracted from
a malt by cold water as by water at 150 F (65'5 C.). The
determination of colour is therefore most conveniently performed
by filling a 1 inch cell of Lovibond's tintometer with the 20 per
cent, cold-water extract, and employing the 52 series of yellow
glasses.
Example. A 20 per cent, cold-water extract, prepared as
described, filtered and examined in the tintometer, using a 1 inch
cell, required glass No. 5. The colour value is therefore 5.
15. Mineral Matter Or Ash. This is determined by
measuring 50 c.c. of the 10 per cent, cold-water extract at 60 F.
(15*5 C.) and evaporating to dryness over the water bath in a
tared platinum dish. The dish is then placed over a Bunsen
flame and the residue cautiously ignited. At first the residue
swells in the form of a semi-carbonaceous mass, but afterwards
shrinks. Objectionable fumes are often given off, but may be
obviated by applying a light. A strong flame may now be used,
and the dish covered with a piece of platinum foil so as to
METHODS OF ANALYSIS 205
accelerate the oxidation of the carbonaceous matter. 1 The
ignition should be continued until not a glowing particle can be
seen in the ash when the latter is red-hot. Preferably, however,
the dish is placed in a muffle, and the reduction to complete ash
easily effected. When the ash is either grey or brown the latter
indicating the presence of iron the dish is placed under the
desiccator, and when cool, weighed. After weighing, the ash
should be dissolved by means of a little hydrochloric acid, the
dish carefully cleaned, ignited, cooled, and re-tared ; a correction
being necessary should the dish have lost weight, which is
sometimes the case, especially if subjected to prolonged intense
heat.
Example. Fifty c.c. of the 10 per cent, cold-water extract,
evaporated to dryness, incinerated to ash in a platinum dish,
cooled, and weighed.
Weight of platinum dish + ash . . . 16*394
Weight of platinum dish .... 16*340
054
054 x 2 = '108 per cent, ash on wort,
and -108 x 10 = 1 '08 per cent ash on malt.
PROTEIDS OR ALBUMINOIDS.
There are several methods for estimating the proteids or
albuminoids in malt, wort, sugar, beer, etc.; thus we have
Kjeldahl's process, 2 which consists in digesting the substance
in a flask for several hours with an excess of sulphuric acid at
a temperature approaching the boiling-point of the acid, whereby
the greater part of the organic nitrogen is converted into
ammonia, and this conversion is completed by oxidation with
potassic permanganate, which is added as a fine powder in very
small quantities at a time. The addition of permanganate is
continued until the solution becomes green, showing that an
excess has been employed. When cold, the liquid is diluted
with water, rendered alkaline with a strong solution of caustic
soda, and then distilled into a receiver containing a measured
quantity of standard acid (figs. 71 and 72). Kjeldahl's method
1 It is usual to sulphate before incineration, the result being more quickly
and reliably achieved. This is accomplished by adding 2 or 3 c.c. of
sulphuric acid to the wort, evaporating, and burning off in the manner
described.
2 Jnl. Chem. Soc., Abstracts, 1884, 364.
206
THE BREWER'S ANALYST
was quickly taken up by other investigators, C. Arnold 1 suggest-
ing a slight modification and Gunning 2 proposing another.
We have also the older methods, such as burning the organic
substance with copper oxide and copper so as to obtain all the
nitrogen as a gas, and the well-known method by which the
substance is mixed with soda lime and burned so as to decompose
the nitrogenous substance to ammonia. Kjeldahl's process,
however, either as originally proposed or with slight modification,
is usually resorted to in ordinary routine work ; but for a thorough
investigation as to its accuracy, the reader is referred to the first
volume of the Transactions of the Guinness Research Laboratory.
For all ordinary purposes, however, the following modification
of Kjeldahl's method is sufficiently accurate :
Fio. 71.
From 1 to 5 grams (according to richness in nitrogen) of the
substance is introduced into a flask of hard Jena glass, and
treated with 10 or 20 c.c. of strong sulphuric acid and 5 grams
of potassic sulphate. The flask is then heated over a Bunsen
flame very gradually, and after frothing has ceased, the heat
is increased to brisk boiling and continued until the liquid
gradually becomes clear and colourless. The contents of the
flask are then cooled, washed into a distilling flask, a sufficient
quantity of sodium hydrate to more than neutralise the acid is
quickly added, arid the flask then connected with the condensing
apparatus and the ammonia distilled over into a flask containing
a known quantity of a standard sulphuric acid. The loss of
acidity is then finally determined in the usual way, and expressed
as nitrogen or albumin. In figs. 71 and 72 we have a series of
* Jnl. Chem. Soc., Abstracts, 1885, 930, and 1887, 78.
2 Ibid., 1889, 796.
METHODS OF ANALYSIS
207
flasks in which to digest the substance, a series of distilling flasks
each connected with a condensing tube, and a series of flasks to
contain the standard acid.
Example :
16. Total Albuminoids. Two grams of the malt are
weighed, ground to powder, and placed in a boiling flask. Ten c.c.
of strong sulphuric acid and 5 grams of potassic sulphate are added,
and the flask placed over a flame and the contents gradually
raised in temperature. After frothing has ceased, the heat is
increased to boiling-point and the heating continued until the
FIG. 72.
contents become colourless or possessing but a pale yellow tinge.
The contents of the flask are now cooled, washed into a distilling
flask with about 100 c.c. of ammonia free water, about 40 c.c.
of sodium hydrate added, and a few pieces of pumice-stone or
pipe-clay to prevent bumping. The flask is then connected
with the distilling apparatus and the contents distilled, the
N
distillate being collected in a flask containing 75 c.c. - sulphuric
acid. When about 100 c.c. of the distillate has been collected,
the whole of the ammonia produced by decomposition of the
proteid bodies will have passed over and have been absorbed and
N
neutralised by the acid.
The acidity of the distillate is now tested by adding a few
208 THE BREWER'S ANALYST
drops of methyl-orange as indicator and titrating with
ammonia; the number of c.c. required being deducted from the
quantity of acid placed in the flask (75 c.c.), equals the
20
number of c.c. of acid neutralised by the ammonia produced by
the decomposition of the proteids originally in the malt.
N
Each c.c. of acid equals '0007 nitrogen. Taking the
20
albuminoids as containing 15*7 per cent, of nitrogen, we calculate
the quantity of albuminoids to which the nitrogen corresponds.
The factor 6 '33 is used for this purpose. In titrating the
N
distillate with ammonia, suppose the quantity required to
20
N
neutralise the acid equalled 34'60 c.c. Then 75'00-
N
34*60 c.c = 40 '40 c.c. acid neutralised by the ammonia
derived from the albuminoids originally contained in 2 grams of
malt, and 40'40 x -0007 = '028280 x 50 = 1-414000 x 6'33 = 8'94
per cent, total albuminoids on the malt.
A correction is necessary for the nitrogen in the reagents used
and for the action on the glass apparatus, and it is advisable in
all instances to perform a blank experiment and deduct the
ammonia so found.
17. Soluble Albuminoids. Ten c.c. of the 10 per cent,
cold-water extract employed for the determination of matters
soluble in cold water (p. 203) are run into a boiling flask and
evaporated to dryness on the water bath. Ten c.c. of sulphuric
acid and 5 grams of potassium sulphate are now added and the
mixture heated, at first gently, until the first violent action is
over, and afterwards strongly, until the liquid is decolorised.
The liquid is now transferred to the distilling flask with about
100 c.c. of ammonia free water, about 40 c.c. of sodium hydrate
added, and a few pieces of pumice-storie or pipe-clay to prevent
bumping. The flask is then connected with the distilling
apparatus and the contents distilled, the distillate being collected
N
in a flask containing 50 c.c. - sulphuric acid. When about
'20
100 c.c. of the distillate has been collected, the whole of the
ammonia produced by decomposition of the proteids will have
passed over and have been absorbed and neutralised by the
N aci d.
20
METHODS OF ANALYSIS 209
The acidity of the distillate is now tested by adding a few
N
drops of methyl-orange as indicator and titrating with
^0
ammonia ; the number of c.c. required being deducted from the
N
quantity of acid placed in the flask (50 c.c.), equals the number
of c.c. of acid neutralised by the ammonia produced by the de-
composition of the proteids originally in the malt wort.
N
Each c.c. of acid equals '0007 nitrogen. Taking the album-
20
inoids as containing 15*7 per cent, of nitrogen, we calculate the
quantity of albuminoids to which the nitrogen corresponds by
the use of the factor 6*33, thus
N
In titrating the distillate with ammonia, suppose the
.20
N
quantity required to neutralise the acid equals 44 '0 c.c.
.20
Then 50*0 c.c. - 44'0 c.c. = 6-0 c.c. x -0007 = "00420 x 100 - '42000
x 6-33 = 2*66 per cent, soluble albuminoids on the malt.
18. Insoluble Albuminoids. The soluble albuminoids de-
ducted from the total albuminoids denote the insoluble, thus :
Total albuminoids . . . 8 '94 per cent.
Soluble 2-66
Insoluble 6'28
19. Diastatie Power. A 5 per cent, solution of cold-water
malt extract is prepared by taking 50 c.c. of the former 20 per
cent, cold-water extract, detailed under the determination of
matters soluble in cold water (p. 203), and making up to 200 c.c.
with distilled water at 60 F. (15'5 C.). 1 Now take twelve
1 It will be observed (p. 203) that the 20 per cent, cold-water extract is
allowed to stand for exactly three hours at 70 F. (21 C.). The time of
standing, up to six hours, does not interfere with the diastatic power, so long
as the temperature is a constant 70 F. (21 C.), but if the temperature is
increased the diastatic power of the extract varies, as the following will show :
Diastatic power taken after cold-water extract stood
For 1 hour. 3 hours. 6 hours.
D. P. 29 29-4 29'4
Temperature of digestion. Diastatic power.
29-4
37-7
57-1
14
210 THE BREWER'S ANALYST
Nessler or other glass tubes of about 50 c.c. capacity marked
1 to 12 (these are best arranged in order in the star apparatus
devised by Reischauer), and add to each tube 10 c.c. of soluble
starch solution prepared as described under Standard Solutions
(p. 144). Now fill a graduated 5 c.c. pipette with the 5 per
cent, cold-water extract, and add to the first tube *1 c.c., to the
second tube -2 c.c., to the third tube -3 c.c., and so on up to
the twelfth tube 1 "2 c.c. Shake the tubes and place them in the
water bath, and maintain for exactly one hour at a temperature
of 70 F. (21 C.). Now add to each tube 5 c.c. of Fehling's
solution (i.e. 2'5 c.c. copper sulphate, and 2 '5 c.c. alkaline tartrate),
shake the tubes and place them in boiling water, and leave them
for five minutes. At the end of this time remove the tubes
and allow them to stand for five minutes. Now note the
tube in which the blue colour has entirely disappeared. It
often happens that there is a blue colour in one tube, and
the next is overdone, that is, the colour is yellow In such
case the mean of the two is taken. For instance, suppose
the third tube, containing '3 c.c. of wort, is blue, and the fourth
tube, containing *4 c.c. of wort, is overdone. In such instance
the mean, viz. '35, is taken, and with practice it is easy to
judge even more accurately, reading to one-fourth the value
between each tube. Thus the third tube may be quite blue,
the fourth only slightly overdone, in which case a reading of
325 is taken.
Lintner, to whom we are indebted for this test (see p. 108),
bases his standard as follows:
The diastatic power of a malt is to be taken at 100 degrees,
when "1 c.c. of a 5 per cent, solution of malt extract just reduces
5 c.c. of Fehling's solution.
Example. The end point was found to lie between the third
and fourth tube ; the amount of malt extract to be taken is there-
fore -3 + '4 -r 2 = -35, and 122 x ] = 28'57.
3o
This figure must be calculated upon water-free malt. Our malt
is found to contain 2'34 per cent, of moisture; then 100 - 2'34 =
97-66, and -122. x 28'57 = 29'25.
97 66
The cold-water extract, however, itself contains a small
amount of reducing sugars, and a correction for these
must be made. This may be accomplished by conducting a
blank experiment, or the more usual practice is to reckon
that such reducing sugars are equal to 1'4. We therefore
METHODS OF ANALYSIS 211
have 29-25 - 1*4 = 27*85 diastatic power of malt on Lintner's
scale.
Instead of performing the operation as just described, the
following method may be adopted :
Three c.c. of the 5 per cent, cold-water extract is allowed to
act on 100 c.c. of a 2 per cent, solution of soluble starch at 70 F.
(21 C.) for one hour in a 200 c.c. flask.
N
Ten c.c. of caustic alkali is then added, in order to stop
further diastatic action, the liquid cooled to 60 F. (15*5 C.),
made up to 200 c.c. with distilled water at the same temperature,
well shaken, and titrated against 5 c.c. portions of Fehling's
solution, using ferrous thiocyanate as indicator.
The titration is carried out as follows :
Five c.c. of Fehling's solution are accurately measured into a
150 c.c. boiling flask. The converted starch solution is added
from a burette, in small quantities at first of about 5 c.c., the
mixture being kept rotated and boiled after each addition until
reduction of the copper is complete, which is ascertained by
rapidly withdrawing a drop of the liquid by a glass rod, and
bringing it at once in contact with a drop of the indicator on a
porcelain or opal glass slab.
Our analysis now works out as follows :
MALT ANALYSIS.
1. Extraneous matters (per cent.) . . . 1'2
2. Defective corns (per cent.) . . . 1 '0
3. Weight per bushel (Ibs.) .... 42
4. Steely corns (per cent.) .... 2
5. Specific gravity (10 per cent. wort). Seek 25 1029'! 1
6. Extract per quarter (336 Ibs.) . . . 97'80
7. Dry extract (per cent.) . . . 75*41
8. Saccharification period (minutes) . . 25*00
9. Specific rotatory power of mash wort . 9 = [a] n l!9*4
10. Acidity (per cent.) . . . . 0*13
11. Moisture (per cent.) . . . . . 2 '34
12. Matters soluble in cold water (per cent.) . 16*06
13. Ready-formed soluble carbohydrates (per cent.) 12*19
1 In the examination of green malts, where the diastatic power often exceeds
100, the malt, extract is diluted with an equal volume of water before being
added to the tubes containing the soluble starch, the result being multiplied
by 2.
212 THE BREWER'S ANALYST
14. Colour of wort 5
15. Mineral matter or ash (per cent.) . . T08
16. Total albuminoids (per cent.) . . . 8*94
17. Soluble albuminoids (per cent.) . . . 2'66
18. Insoluble albuminoids (per cent.) . . 6 '2 8
19. Diastatic power 27*85
WORT ANALYSIS.
Some few years ago the analysis of wort, as far as the carbo-
hydrate constituents are concerned, consisted in first making a
certain per cent, solution according to the gravity, taking a
definite quantity, and conducting a Fehling's test, so as to obtain
the cupric reducing power from which the percentage of maltose
was first calculated, and afterwards the percentage of dextrose
which such maltose would yield by hydrolysis. A further
percentage solution of the wort was then made, and a definite
portion inverted for a certain time at the boiling temperature, with
the addition of 5 c.c. hydrochloric acid, after which it was cooled,
neutralised, made to bulk, and the cupric reducing power again
estimated and calculated to percentage on the wort. From these
two results (before and after inversion) the former calculated
dextrose was deducted from the reducing bodies obtained after
inversion, and the result multiplied by - 9 gave the actual amount
of dextrin. We thus obtained both the percentage of maltose
and dextrin which the wort was supposed to contain. Now this
was all very well in its way, but within recent years it has been
shown that malt contains reducing sugars (ready-formed soluble
carbohydrates) such as dextrose, levulose, and cane-sugar, so that
unless we first take account of and deduct these we shall actually
be attributing their presence in wort as due to the conversion of
our starch, which is not so. Again, the inversion by the aid of acid
results in the formation of inert bodies by reason of a decomposi-
tion of the end-products of inversion, the ready-formed cane-sugar
being hydrolysed to dextrose, and some of the albuminoids trans-
formed into actual cupric reducing bodies.
There can be no doubt under these circumstances that, with
worts, the inversion method is to be condemned, and in its stead
the carbohydrates estimated by the aid of the polarimeter. The
total sugars are therefore now estimated from the cupric oxide
reducing power, after deducting those ready formed, calculating
to maltose, and then multiplying the maltose by the specific
rotatory power of the wort,^so obtaining the angle due to maltose,
METHODS OF ANALYSIS 213
and deducting this from the total rotatory power so as to obtain
the angle due to dextrin ; the latter angle is then divided by the
rotatory power of 1 part dextrin, which gives at once the percentage
of dextrin present in the wort.
MALT WORT.
The method proposed as regards malt wort was originally
devised by Heron, and is essentially as hereafter detailed, the
following being the determinations to be made :
/ 1. Dry extract per cent.
Hot mash wort . j * S P eoifio rotator y P ower '
3. Cupnc oxide reducing power.
4. Acidity.
5. Matters soluble in cold water.
6. Ready-formed soluble carbohydrates.
7. Soluble proteids or albuminoids.
Cold-water extract -, g gpecifi( , rotatory power _
9. Cupric oxide reducing power.
^0. Mineral matter or ash.
In the ordinary course of events, had it been our primary
intention to analyse the wort from the previously examined malt,
most of these results would be carried forward. If they have
not been determined, it becomes essential to make a 10 per cent,
mash wort and carry out the experiments. We may, however,
to save repetition, carry the results of our malt analysis forward,
thus :
1. Dry Extract per cent, or Total Solids. Determined
as explained under Malt Analysis.
Example. The specific gravity of 10 per cent, hot mash wort
= 1029-10 -1000 = 29-11-^3-86 = 7-54 dry solids per 100 c.c. of
wort.
2. Specific Rotatory Power of Hot Mash Wort.
Determined as explained under Malt Analysis.
Example. Opticity of 50 per cent, solution at 68 F. (20 C.)
in a 1-decimetre tube= 4'5 x 2 = 9 on 100 parts of wort.
3. Cuprie Oxide Reducing 1 Power of Hot Mash Wort.
The determination of the reducing sugars is one of the most
important estimations in brewing analysis, and as this depends
largely on the reduction of Fehling's solution, it is advisable to
give in some detail the exact method in which the reductions
are made.
214 THE BREWER'S ANALYST
In estimating the cupric reducing power, careful attention
must be paid to the following points :
(1) The exact composition of the Fehling's solution as regards
copper, and the nature and amount of the alkali it contains.
(2) The degree of dilution of the Fehling's solution.
(3) The restriction of the amount of copper reduced within
certain prescribed limits.
(4) The mode of heating the solution, and the time occupied in
reduction.
Having regard to the foregoing, the normal conditions under
which all determinations should be made are :
(a) The use of Fehling's solution prepared as described under-
Standard Solutions.
(b) The degree of dilution of the copper solution, taking into
account the volume of the saccharine solution added, should be
one part of Fehling's solution to one part of water.
(c) An amount of the reducing sugar should be taken which
will give a weight of CuO lying within the limit of 0*15 to 0'35
gram.
(d) The diluted Fehling's solution should be heated in a
suitable beaker in a boiling-water bath until the temperature is
constant, and then the weighed or accurately measured volume
of liquid containing the reducing sugar added, arid the heating in
the water-bath continued for exactly 12 minutes, the beaker
being covered with a clock-glass during the whole period of
heating. The nitration should be performed as rapidly as
possible through a carefully folded paper, and the paper then
dried and burned off in a tared crucible over a Bunsen flame in
the usual way, and after cooling, the contents weighed as cupric
oxide.
Example. Fehling's solution is first diluted as follows :
25 c.c. of the copper solution and 25 c.c. alkaline tartrate are
added to a beaker together with 30 c.c. of distilled water. The
beaker is then placed in the boiling-water bath, and when its
contents are brought to the boiling-point 20 c.c. of the 10 per
cerrt. mash wort are added, and the whole boiled for 12 minutes.
The beaker is then removed and the contents filtered. A good
filter paper should be used, or otherwise some of the CuO is liable
to pass through. If such were the case, it would, after standing,
be found at the bottom of the beaker which has received the
filtrate, in which case it becomes essential to refilter. Wash the
precipitate time after time, using for this purpose about 200 c.c.
of boiling water, and finally wash with about 10 c.c. of strong
METHODS OF ANALYSIS 215
alcohol, then dry the filter in the water oven, transfer to a tared
crucible and burn off, ignite to redness for 15 minutes, cool under
the desiccator and weigh, repeating the heating, cooling, and
weighing until the weight is constant.
Example ;
Weight of crucible and CuO . . 6'780 grams
Weight of crucible . . . 6'633
147 i
147 = amount in 20 c.c. of 10 per cent, solution of wort, or 2 c.c.
of wort. Then '147 x 50 = 7 '35 grams in 100 c c. of wort.
4. Acidity. This is determined as in Malt Analysis by
N
titrating 100 c.c. of the 10 per cent, wort with alkali, using
litmus as indicator.
Example, 100 c.c. of 10 per cent, wort required 1*5 c.c.
alkali. 1-5 x -009 = '0135 acid in 100 c.c. of wort.
5. Matters Soluble in Cold Water. These are determined
exactly as in Malt Analysis.
Example. Specific gravity of cold-water extract = 1006-20.
1006-20 -1000 = 6-20 -=-3-86 = 1'60G dry solids per 100 c.c. of
solution.
6. Ready-formed Soluble Carbohydrates. Also deter
mined as in Malt Analysis.
Per cent,
on malt.
Matters soluble in cold water . . 16*06
Per cent.
on malt.
Soluble albuminoids . . . 2 -6 6
Mineral matter or ash . . . 1'OS
Acidity . . . . 0*13
3-87
12-19
The ready-formed soluble carbohydrates on 100 parts of malt =
12'19, so that 10 grams of malt contain 1'21 to correspond with
100 c.c. of wort.
7. Soluble Proteids Or Albuminoids. These are deter-
mined as in malt analysis, under Soluble Albuminoids.
10 c.c. of the 10 per cent, cold-water extract evaporated to
dryness in a boiling flask ; 10 c.c. of strong sulphuric acid and 5
1 This figure, it will be noticed, is rather low.
216 THE BREWER'S ANALYST
grams of potassic sulphate added, the contents warmed and then
boiled until the solution is clear ; then added to a distilling flask
with about 100 c.c. distilled water, about 40 c.c. sodic hydrate
added together with a few pieces of pumice, the flask connected
with the distilling apparatus and the contents distilled, the
N
distillate being collected in a flask containing 50 c.c. sulphuric
20
acid.
100 c.c. of the distillate having been collected, the acidity is
tested :
N N
Example. 50 c.c. acid required 44 c.c. - alkali to effect
neutralisation.
50 - 44 = 6-0 c.c. x -0007 = -00420 x 10 = -04200 x 6'33 = -26
albuminoids in 100 c.c. of cold-water extract.
8. Specific Rotatory Power of Cold water Extract. A
small quantity of the extract is boiled and then cooled to 68 F.
(20 C.). A 2 decimetre tube is then filled with the same, placed
in the polarimeter, and a reading taken. The reading, divided by
2, gives the reading of a 1 -decimetre tube.
Example. Opticity in 2-decimetre tube = 0'60. 0'60 -f 2 = 0'30.
9. Cupric Oxide Reducing* Power of Cold water Extract.
Determined as with the 10 per cent, hot mash wort (p. 213).
Example. CuO obtained = '282 amount in 20 c.c. -282x5 =
1'41 gram on 100 c.c. of 10 per cent, malt extract to correspond
with 100 parts of wort.
10. Mineral Matter or Ash. Determined as per Malt
Analysis. 50 c.c. of the 10 per cent, cold-water extract evaporated
to dryness in a tared platinum dish, after sulphating; then
ignited to ash, cooled, and weighed :
Weight of platinum dish + ash . . . 16-394
Weight of platinum dish .... 16 '340
054
054 x 2 = -108 per cent, on wort.
We now deduct the figures obtained from experiments with
our cold-water extract from the corresponding determinations of
our hot wort, thereby arriving at figures due entirely to starch
products. Our results are therefore worked out as follows :
w , Cold-water Conversion Products
Extract. due to Starch.
Cupric oxide reducing power 7'35 - 1'41 = 5'94
Specific rotatory power . 9'00 - 0'30 = 8'70
METHODS OF ANALYSIS 217
Each gram of cupric oxide, according to Fehling's factor, equals
7435 grain of maltose; we therefore obtain the amount of
maltose in the wort by multiplying the cupric oxide obtained by
this factor.
5*94 (CuO due to starch products) x '7435 = 4*44 maltose in the
wort expressed in percentage on the wort.
The specific rotatory power of 100 grams of maltose, when
observed in a 1-decimetre tube, is [a] Dg . 86 = 135'9 ; therefore
1 gram = T359 . The amount of maltose calculated equals 4'44 ;
so this, multiplied by 1*359, = 6*03 angle due to maltose. Deduct-
ing this angle from the total angle of starch products, we get the
angle due to dextrin.
The specific rotatory power of 100 parts of dextrin = [a] D3 . 86
194-4 , or 1 part= 1*944; therefore the remaining specific rotatory
angle, divided by 1'944, gives the amount of dextrin expressed in
percentage on the wort.
Example. Total angle = 8'70 - 6 '03 = 2*67 due to dextrin, and
*2'fi7
JLrL.1-38 dextrin in 100 parts of wort.
100 parts of the wort therefore contain :
Maltose (due to starch conversion) . . . 4 '44
Dextrin (due to starch conversion) . . . 1'38
Ready-formed soluble carbohydrates . 1-21
Proteids or albuminoids ..... -26
Mineral matter or ash . . . . . '10
Other bodies by difference . . . . "15
Total dry solids . . .7-54
It is usual to express the composition of wort in percentage on
its dry extract, as this permits of a comparison of the composition
irrespective of gravity. This is performed by ordinary rule of
three, thus :
Dry extract
7'54 : 4-44 (maltose) : : 100 58*87
1-38 (dextrin) : : 100
1*21 (ready-formed
sugars) : : 100
26 (albuminoids) : : 100
10 (ash) : : 100
15 (other bodies) : : 100
18-32
16-05
3-44
1-33
1-99
100-00
218 THE BREWER'S ANALYST
The specific rotatory power of the wort is similarly calculated
on the dry extract :
Dry Extract. Sl-ific Rotatory
7-54 : 9-0 :: 100: |>] D 119-4 .
KAW-GRAIN WORT ANALYSIS.
In our former analysis we have dealt with wort obtained
entirely from malt, but it is hardly necessary to mention that
similar analysis may be performed by conducting our mashing
operation with a mixture of malt and prepared raw grain, such
as flaked or granulated maize or rice, in such proportions as is
carried on practically in any particular brewery. It may also
be necessary to conduct our mashing operation with malt and
unprepared raw grain, such as maize or rice grits. In such
instances it therefore becomes necessary to take a similar pro-
portion of the one or the other as is being used in practice,
gelatinise the starch, and cool the same to 150 F. (65 '5 C.)
before mixing with our malt mash.
In all such instances we merely reduce the percentage of malt
in accordance with the percentage of raw grain employed, obtain-
ing the usual 10 per cent, wort both with our mash and our
cold-water extract, our results being then obtained precisely as
described in malt and malt-wort analysis. It is obvious, however,
that this essential method of procedure with different percentages
of raw grain, raises grave difficulties to the standardisation of
analysis (see p. 231).
MASH-TUN WORT ANALYSIS.
In many breweries it is a general custom, and an excellent
one, to test the wort obtained from every mash in order to
ascertain whether the conversion has been rightly conducted and
the proper ratio of dextrin to maltose obtained.
With pale ale and so-called " stock ale," the dextrin percentage
should undoubtedly be greater than for a mild or running beer,
so that by testing the mash-tun worts any change in character of
materials used or variation in mashing or sparging may at once
be detected.
Mash-tun wort to be tested should be collected from the taps
at two different periods : first, a sample should be taken exactly
15 minutes from setting taps ; and secondly, a further sample
after the sparge liquor has got well through the goods, say
METHODS OF ANALYSTS 219
exactly 2 hours after setting taps. The two samples should
then be well mixed together, boiled for a minute or two, cooled
to 60 F. (15*5 C.), and the specific gravity taken. The specific
gravity should then be reduced to 1050 and a polarimetric
reading taken with the wort at a temperature of 68 F.
(20- C.).
Example. (a) Sample of wort collected from inash-tun taps 15
minutes after setting, sp. gr. 1078 '96. (b) Sample taken 2 hours
after setting taps, sp. gr. 1025*28.
The two samples mixed together = sp. gr. 1052' 12. 50 c.c. of the
wort at 1052 '12, reduced in gravity to 1050 by the addition of
2*12 c.c. water, and the solution raised to the boiling-point.
Now, before a polarimetric reading can be accurately taken, the
wort must be perfectly clear. Wort taken from the mash-tun
taps, on cooling, is never clear ; it therefore becomes necessary to
render it so; and in order to do this, 100 c.c. of the wort at a
specific gravity of 1050, after raising to the boiling point, is run
into a 200 c.c. flask together with 10 c.c. of a 10 per cent, solution
of lead acetate, made to 200 c.c. with distilled water, thoroughly
mixed and filtered through a dry filter paper into a clean dry
beaker = 50 per cent, solution.
The specific rotatory power is now taken in a 1 decimetre tube,
with the wort at a temperature of 68 F. (20 C.) ; reading x 2 =
opticity of the wort.
COPPER-WORT ANALYSIS.
In the analysis of wort from the copper, the following are the
determinations to be made :
1. Specific gravity.
2. Dry extract per cent.
3. Cupric oxide reducing power.
4. Specific rotatory power.
5. Proteid bodies or albuminoids.
6. Mineral matter or ash.
From the third and fourth determinations we arrive at the
percentage of dextrin and maltose in the wort.
As previously cited, malt contains ready-formed soluble carbo-
hydrates ; and unless we estimate their amount and deduct them
from our results, we shall be attributing their presence to
the conversion of starch at the mashing stage. It is therefore
necessary to estimate the cupric oxide reducing power and the
220 THE BREWER'S ANALYST
specific rotatory power of a cold-water extract made from a sample
of the malt employed in mashing, and deduct these results from
the results obtained with the copper wort. We may then
determine the albuminoids and mineral matter from the copper
wort itself.
Now, provided any of these results have already been determined,
such as they would have been had we already analysed the malt
or a cold-water extract produced from it, our results may be
carried forward ; and it only becomes necessary to find the factor
by which to multiply our cold-water extract results to make them
correspond with a wort of the same percentage of dry solids as
our copper wort.
The following example will make this clear :
Sp. gr. of copper wort = 1045 - 1000 = ^1 = 11'66 dry solids
3*86
per 100 c.c.
9Q-1 1
Sp. gr. of laboratory 10 percent. wort = 1029'11 - 1000 = -~
o'oo
= 7-54 dry solids per 100 c.c.
1 1 fifi
,- - = 1*54 factor by which to multiply 10 per cent, cold-water
extract results in order to make them correspond with a wort
of the same percentage of dry solids as our copper wort
(viz. 11-66).
An analysis of our copper wort gives, say, CuO per 100 c.c. =
11-42.
An analysis of our copper wort gives, say, specific rotatory
power = 14 '43.
Our cold-water extract results gave CuO per 100 c.c. = 1*41.
Our cold-water extract results gave specific rotatory power 0'30.
Hence corrections to correspond with our copper wort are :
CuO 1-41 x 1-54 = 2-17.
Specific rotatory angle . . 0*30 xl '54= '46.
Which give figures due to maltose and dextrin as follows :
CuO 11-42 -2-17 = 9-25.
Specific rotatory angle . . 14-43 - -46 = 13-97.
Then 9-25 x -7435 = 6*87 per cent, maltose on the wort,
6 '87 x 1'359 = 9-34 specific rotatory power due to maltose,
13*97 - 9'34 = 4'63 specific rotatory power due to dextrin,
and 4-63 -"-1-944 = 2*38 per cent, dextrin on the wort
METHODS OF ANALYSIS 221
The copper wort therefore contains :
Carried forward. Maltose 6-87percent.
Dextrin 2 -38
Ready-formed soluble carbohydrates 1*21 x 1*54 . 1*86
Soluble albuminoids 0-26 x 1-54 . . . -40
Mineral matter O'lO x 1 '54 -15
11-66
Which may be expressed as percentage composition thus :
Dry extract
11-66 : 6-87 : : 100 : 58'92 maltose.
2-38 : : 100 : 20'41 dextrin.
1'86 : : 100 : 15'95 ready formed soluble carbohydrates.
40 : : 100 : 3'43 albuminoids.
'15 : : 100 : 1-29 mineral matter.
100-00
Should it be desired to express the maltose and dextrins in
terms of malto-dextrins, this may be performed as hereafter
described.
MALTO-DEXTRINS OR AMYLOINS IN WORT.
It will have been seen that in our former wort analysis we
have returned the starch transformation products as maltose
and dextrin only, but from a perusal of our remarks, p. 79, it is
evident that the products of the hydrolysis of starch by diastase
include not merely maltose and dextrin, but combinations of
the two, termed malto-dextrins or amyloins.
Moritz and Morris 1 describe a method for the determination
of the malto-dextrins based on the assumption that the free
maltose is completely fermentable by primary yeast, any reducing
sugars found after such fermentation being therefore due to
combined maltose, existing as malto-dextrin ; the combined
dextrin being determined by hydrolysing it into maltose by
means of cold-water extract, and then determining the increase
in reducing sugars.
The method of analysis is as follows :
(1) A diastatic solution to be used for hydrolysing the malto-
dextrins is first prepared thus :
200 grams of finely ground highly diastatic malt are added to
1 ^Text-book of the Science of Brewing.
222 THE BREWER'S ANALYST
500 c.c. of distilled water, well stirred, and allowed to stand in
a cool place over-night. It is then filtered, the bright nitrate
being used for the subsequent determinations.
The reducing power of this solution is now ascertained :
10 c.c. of the filtrate are diluted to 100 c.c., digested 1 hour
at 130 F. (54'4 C.), then cooled, and the reducing power estimated
on 10 c.c. (=1 c.c. of cold-water extract).
CuO obtained = 0'074 gram.
This correction must be made when the solution is employed.
(2) The percentage of dry solids in the wort is now determined
by taking the specific gravity and dividing the excess weight
over 1000 by the solution factor 3-86. Thus sp. gr. = 1045.
.'. . = 11 '65 per cent, dry solids.
o'$G
(3) Determination of Combined Maltose, (a) Reducing
Power of Wort after removal of free maltose by fermentation with
yeast. Fifty c.c. of the wort are taken, placed in a small flask,
"25 gram of washed pressed yeast added, the mouth of the flask
loosely plugged with cotton-wool, the flask placed on the forcing
tray, and the contents allowed to ferment at 80 F. (26'6 C.)
for 48 hours.
The wort is now boiled to expel the alcohol, cooled to 60 F.
(15'5 C.), diluted to 100 c.c., a small quantity of alumina or
kieselguhr added to assist clarification, then filtered, and the
reducing power determined on 25 c.c. of the bright filtrate.
CuO obtained = 0'196 gram.
(b) Reducing Power of the Wort after removal of free maltose
and maltose in malto-dexlrin, by diastatic hydrolysis and yeast
fermentation. Fifty c.c. of the wort are fermented as previously
described, but with the addition of '25 c.c. of diastatic solution as
well as yeast (to hydrolyse the malto-dextrins).
Fermentation being complete, the solution is boiled to expel
the alcohol, cooled to 60 F. (15'5 C.), a little alumina or
kieselguhr added, the whole made up to 100 c.c., filtered, and
the reducing power determined on 25 c.c. of the bright filtrate.
CuO obtained = 0-1 30 gram.
This is due to the reducing bodies in the wort, other than
maltose, and must be deducted from the amount found in the
former experiment 3 (a). Therefore -196 - '130 = -066 CuO due
to combined maltose. The 25 c.c. of reduced wort used contained
METHODS OF ANALYSIS 223
12 '5 of original wort; therefore, by multiplying by 8, we have
the CuO due to maltose per cent, on the wort.
066 x 8= '528 CuO in 100 c.c. wort, and
528 x -7435= ^392 combined maltose.
This, calculated on the dry solids, gives :
'392 x .. _ = 3 '36 per cent, maltose in motto-dextrin.
4. Determination of Combined Dextrin. (a) Reducing
Power of Wort. Two hundred c.c. of the wort are diluted to 100
c.c., 10 c.c. of this solution ( = 2 c.c. wort) are now taken, and a
gravimetric estimation of the sugar made, just as described under
Wort Analysis.
CuO obtained = 0-282.
(b) Reducing Power of the Wort after digestion with cold-water
malt extract. Twenty c.c. of the wort are taken, 2 '5 c.c. of the
previously prepared diastatic solution added, and the whole
maintained in a water bath for 1 hour at 130 F. (54 '4 C.).
The solution is now cooled and diluted to 100 c.c., and the
reducing power determined in 10 c.c.
CuO obtained = 0-324.
As the cold-malt extract used contained some reducing bodies,
the amount of CuO due to these must be deducted. As 1 c.c. of
the cold extract gave 0'074 CuO, a deduction of 0'018 due to
'25 c.c. must be made from the total CuO obtained.
Total CuO 0-324
Deduction for cold-water extract 0-018
0-306
The CuO due to the maltose and reducing bodies naturally
present in the wort amounted to 0*282 gram. Therefore 0'306 -
0-282 = 0-024 CuO due to maltose from the hydrolysis of the
combined dextrin in 2 c.c. of wort, and 0'024 x 50= 1'20 CuO
in 100 c.c., and 1'20 x 706 x = '847 combined dextrin in 100 c.c.
1 00
of wort, or 11-65 dry solids. Then -847 x __ = 7'27 per cent.
1 1 "(3t)
of combined dextrin on the dry solids.
1 The factor '706 is obtained by multiplying that for maltose, viz., '7435 x
'95, as 1 part of maltose is produced from "95 part of dextrin.
224 THE BREWER'S ANALYST
Our results expressed on the dry solids work out thus :
Maltose in malto-dextrin . . . .3*36
Dextrin in malto-dextrin. 7'27
Total malto-dextrin . . 1O63
It will be seen that the method is rather lengthy and tedious,
and is open to the objection that its accuracy must in a great
measure depend upon the type of yeast employed to bring about
the fermentation. It is a process, however, which gives some
useful information and at times is necessary to carry out.
RAW-GRAIN ANALYSIS.
Of this class of material we have unprepared varieties such as
barley, sago, tapioca, oats, maize, and rice. Of these barley gives
a wort possessing a raw, objectionable flavour, and therefore has
not been found an advantageous material to employ ; sago and
tapioca are expensive, and oats are only of use for the production
of a particular kind of stout, as, owing to their high content of
albuminoids and oily matter, they produce definite flavour and a
cloudy wort. We thus narrow down to maize and rice.
Maize contains from 3 to 5 per cent, of oil which suffers decomposi-
tion at the boiling temperature, imparting offensive odours to wort,
and on this account cannot be employed in its raw state. Within
recent years, however, means have been devised for removing .the
oil; and raw maize freed from oil, and now known as "grits," has
become a valuable malt adjunct. The oil in maize is principally
contained within the germ, so that it is merely necessary, in order
to produce it practically free from oil, to grind it through fluted
rollers and afterwards screen it with the help of an air-blast, by
which the germ and hull and starchy portion may be separately
collected. Rice as it comes into this country is dehusked, and is,
practically speaking, free from oil and other deleterious substances,
and hence is a unique brewing material.
We thus have raw maize grits on the one hand and raw rice
on the other, either of which may be employed by the brewer.
The cheapness of these raw materials in comparison to the large
percentage of starch they contain, and the high extract derivable
from their manipulation, is a strong factor in favour of their use,
but unfortunately there exists the fact that it becomes necessary
to first gelatinise the starch prior to mashing. In order to do
this it is necessary, on the practical scale, to infuse the material
METHODS OF ANALYSIS 225
for about one hour at a temperature of 190 F. (87*7 C.) with
constant stirring, and hence a specially constructed conversion
vessel is generally used, so that the starch may be gelatinised and
the solution cooled to a temperature below that at which diastase
is destroyed before passing to the mash-tun or otherwise mixing
in the ordinary malt grist. In order to obviate the necessity of
the brewer carrying out this necessary prior starch gelatinisation,
manufacturers years ago undertook the performance of this
object, with the result that prepared maize and rice were placed
on the market.
These materials are therefore now cooked so as to burst the starch
cells, and are then dried, in which condition they may be directly
employed in the mash-tun, the starch becoming more or less soluble
at the ordinary initial mash temperature of 150 F. (65*5 C.).
The usual mode of preparation is to grind the material through
fluted rollers (in the case of maize grits this will have already
been done), and then pass it to a revolving perforated hopper
which is jacketed so that steam may be injected and made to
permeate the grain. Here the grain is maintained in contact
with steam until gelatinisation of the starch is effected, after
which it is passed to rollers which are internally heated by steam
or gas. The rollers are so adjusted that one roll travels faster
than the other, and in this manner the gelatinised starchy
material as it passes through becomes flaked.
The flakes are finally passed to another perforated cylinder,
enclosed with an iron casing, where they are kept in motion and
subjected to a circulation of hot air until perfectly dry.
In the manufacture of granulated material the methods
employed are similar, excepting that there is no necessity to pass
through rollers, as when manufacturing flakes. It is not unusual
to steep the material in an aqueous acid solution for some time
and then wash it until the washings are neutral, before steaming.
In the analysis of raw grain it sometimes becomes necessary to
estimate the percentage of starch, but so far as the brewer is
concerned, it is more usual to determine the extract yield.
PREPARED RAW GRAIN (GRANULATED AND FLAKED MAIZE
AND RICE).
The following are the determinations to be made :
1. Oil.
2. Starch.
3. Extract per quarter.
15
226
THE BREWER'S ANALYST
4. Proteids or albuminoids.
5. Acidity.
6. Mineral matter or ash.
7. Moisture.
1. Oil. This estimation is usually carried out by means of a
Soxhlet fat-extracting apparatus (fig. 73), which consists of a
water bath 16 cm. diameter, a con-
stant water-level arrangement, a
stand and burner, a metal ball con-
denser, a Soxhlet tube, and a dis-
tilling flask. The alcohol or ether,
used for extracting the oil, is heated
in the flask by means of the heated
water in the bath, the vapour rising-
through the Soxhlet tube and being
condensed falls back into the inner
tube, where the material to be
denuded of oil is placed, so extract-
ing the oil. The condensed solvent
slowly fills the extractor, rises to
the level of the upper inner syphon,
and then returns back again into
the flask, the process being con-
tinuous.
Care should be taken that there
is no leakage in any of the con-
nections or parts of the apparatus,
as the solvent, being very inflam-
mable, would immediately take fire
should any of its vapour come in
contact with a flame.
A loose plug of glass wool or
cotton wool (free from fat) is in-
serted in the bottom of the Soxhlet
tube, and on the top of this is placed the material to be experi-
mented upon. Preferably, however, the material is placed in a
thimble of bibulous paper (fig. 74) and the thimble with its
contents inserted in the Soxhlet tube.
With raw grain, 5 grams, previously freed from moisture and
ground to powder, are added to a thimble and placed in the
Soxhlet, Forty c.c. of alcohol, specific gravity 0'920, are now
added to the distilling flask and the whole Soxhlet apparatus
FIG. 73.
METHODS OF ANALYSIS
227
connected together. The distilling flask is now slowly heated by
the water in the bath, and the alcohol then syphons off from the
extractor; it will be found of the required specific gravity, viz.
0*900, whilst the temperature inside
the extractor varies from 95-104 F.
(35-40 C.). The extraction is carried
on for 5 hours, after which the thimble
is removed from the Soxhlet tube and
its contents transferred to a beaker. 1
The distilling flask is now discon-
nected and the alcoholic solution is
filtered through a filter paper into a
tared beaker, both the flask and paper
being washed with alcohol and the
washings also collected. The beaker
containing the filtrate is now placed
on the water bath and the alcohol
cautiously evaporated. The beaker
with its residue is then placed in the
drying oven for 1 hour, after which
it is cooled under the desiccator and
weighed, the drying, cooling, and weigh-
ing being repeated until the weight is
constant.
The calculation is then as follows :
Five grams of grain taken, the oil,
after extracting, evaporating, drying, cooling, and weighing
Weight of beaker + oil residue
Weight of beaker
100
17-282 grams.
17-120
162
162 x ^ 3*24 per cent, of oil.
u
2. Starch. For the estimation of starch in cereals and other
starch-containing vegetable substances, C. O'Sullivan's method 2
is, on the score of accuracy, by far the best which has been pro-
posed. It consists in first denuding the grain of oil by lengthy,
repeated decantation by the aid of solvents, then solubilising the
starch and afterwards converting it into maltose and dextrin by
1 The grain freed from oil is used in the next experiment for the estimation
of starch.
2 Jni. Chem. Soc. Trans., 1884, 1.
228 THE BREWER'S ANALYST
the aid of malt extract, calculating the starch from the conver-
sion products obtained from both cupric oxide and polarimetric
estimations. The method, however, is very tedious and requires
a great deal of time ; means had therefore to be taken to shorten
the operation, and this has been accomplished ' by extracting the
soluble substances in a Soxhlet apparatus (as in our previous
experiment) in the place of the ordinary process of washing by
decantation, and after converting the starch calculating the same
from the amount of maltose produced.
When starch is hydrolysed by active diastase under suitable
conditions, there is a well-defined resting-stage in the reaction
which closely approximates to the following equation :
10C 12 H 20 10 + 8H 2 = 8C 12 H 22 O n + C 12 H 20 10 .
Starch. Water. Maltose. Dextrin.
Thus 100 parts of starch yield 84'4 per cent, of maltose.
Hence it follows that, if the starch of raw grain is so converted
by diastase as to ensure its splitting up according to the above
reaction, a mere determination of maltose from its cupric reducing
power ought to give a direct measure of the original starch in the
material without the necessity of polarimetric observation. The
following method is therefore recommended :
Five grams of the grain, freed from moisture and denuded of
oil, as in our former experiment, are removed from the Soxhlet
apparatus and transferred to a beaker; 100 c.c. of distilled water
are added and the infusion gradually boiled for about 30 minutes,
adding water, a little at a time, to replace that lost by evaporation.
After cooling to 134'6 F. (57 C.), 10 c.c. of active malt extract 2
are added, and the conversion allowed to proceed for 1 hour.
The solution is then boiled, filtered into a 200 c.c. flask, the
residue well washed, and the volume made up to 200 c.c. at
60 F. (15'5 C.). The solution now contains the conversion
products from the starch of 5 grams of the grain, and the precise
amount of the maltose is ascertained from the cupric oxide
reducing power as follows :
Cupric Oxide Redwing Poiw r. This estimation is made
as described in malt-wort analysis, 10 c.c. of the solution being
added to 30 c.c. of Fehling's solution (15 c.c. copper sulphate
1 Trans. Guinness Research Laboratory, 1903, 1, 79-91.
2 The malt extract is prepared by weighing about 40 grams of malt, grind-
ing the same to powder, and adding to a stoppered bottle together with 150 c.c.
of distilled water. The infusion is set aside for about 1| hours, occasionally
shaking, and is then filtered bright.
METHODS OF ANALYSIS 229
and 15 c.c. alkaline tartrate) together with 50 c.c. of water,
and the determination carried through as explained. CuO ob-
tained = '335 gram. The same estimation is made with 10 c.c.
of the cold-water malt extract, so that correction may be made
for the same. CuO obtained = '152. Then -335 - '152 = '183 x
Fehling's factor 7435= -1360 x 20 = 2-720 maltose in 200 c.c. or
5 grams of grain, which again multiplied by 20 gives 54*40 per
cent, maltose.
The starch equivalent to this maltose is now estimated on the
assumption that 84'4 parts of maltose correspond to 100 parts of
starch ; hence - = 64'45 per cent, starch.
3. Extract per QuaPteP. The method of procedure in this
estimation is somewhat similar to that employed for the estima-
tion of starch, viz., it consists in saccharifying the starch of a
known quantity of the raw grain by the aid of malt extract.
Twenty grams of the grain are weighed, placed in a beaker
together with 120 c.c. of distilled water and 50 c.c. malt extract
at a temperature of 150 F. (65'5 C.). The beaker is then
placed on the water bath and the contents maintained at this
temperature for 1 hour. At the end of this time the mash is
transferred to a 200 c.c. flask, cooled, and made to mark at 60 F.
(15-5 C.) with distilled water.
The mixture is then thoroughly shaken, filtered bright, and
the specific gravity of the wort taken.
We have here the extract produced by the grain plus that due
to the cold-water extract, and a correction must therefore be
made for the latter. This is performed as follows :
Of the original cold-water extract 50 c.c. are taken, slowly
raised in temperature to 150 F. (65*5 C.), and maintained at
this temperature with occasional stirring during 1 hour. The
extract is then transferred to a 200 c.c. flask, cooled, and made
up to bulk at 60 F. (15'5 C.) with distilled water. After
thoroughly mixing, the solution is filtered bright and the specific
gravity taken. We have here the extract due to the cold-water
infusion. The gravity in our first experiment obtained from the
mash, less that in our second experiment obtained from the cold-
water extract, gives the gravity due to the grain. This gravity,
multiplied by 3-32, 1 gives the extract yielded by 336 Ibs. of the
grain or extract per quarter.
1 The grains obtained from 20 grams of granulated or flaked maize or rice
are assumed to occupy a volume of 2 '5 c.c. This being the case when the
mash is made up to 200 c.c., the liquid portion will have a volume of
230
THE BREWER S ANALYST
Formerly it was not unusual to determine the extract obtain-
able from prepared raw grain by mashing two-thirds of a malt of
known extract and one-third of the grain, calculating the extract
in the usual manner of the mixture of malt and raw grain.
Obviously the extract of the malt had to be determined with the
greatest accuracy, as any error would be multiplied in the calcula-
tion of the extract of the raw grain. To show what this error
might amount to, Baker 1 determined the extracts of flakes by
mashing in the first place equal quantities of maize and malt,
and in the second place maize, together with two-thirds its weight
of malt. Four experiments were conducted, in each case with the
same maize, but with malts the extracts of which were known,
but of different diastatic powers. The following table shows the
results :
Diastatic
Power of
Malt.
Extract per 336 Ibs. of
Maize when mashed
with an equal Weight of Malt.
Extract per 336 Ibs. of Maize
when mashed with
two-thirds its Weight of Malt.
40
Ibs.
106*50
Ibs.
106-4
34
102-40
103-2
25
100-25
103-3
12
97-64
99-17
These results indicate the very marked influence which the
diastatic power of the malt employed has on the yield of extract,
and they also show that when more or less highly cured malts are
used, the proportion of malt to maize in the laboratory mash is a
matter of importance, if comparative results are to be obtained.
Where such a process has been followed, the manipulator will
now entirely agree with Baker; but the method has long been
superseded by the diastatic process devised by O'Sullivan, and
already described, the accuracy of which has been recently con-
firmed, 2 the following table being given in proof thereof.
200- 2 '5 = 197 '5 c.c. The factor to convert a 10 per cent, solution into Ibs.
per quarter is 3 '36. As, however, the concentration of the liquid in the above
experiment is less, the factor must be altered in proportion. The calculation
is as follows :
(200 - 2-5) x 3 -36 =3 . 318 in d numbers 3-32.
200
1 The Brewers' Journal, 1905, 41, 186.
2 Jnl. Fed. List. Brewing, No. 5, vol. xi., 1905, 395, 398.
METHODS OF ANALYSIS
231
20 GRAMS OF FLAKBS AND 25 c.c. DIASTATIC SOLUTION.
Diastatic Power of Malt
from which the Diastatic
Solution was obtained.
28
34
65
Extract per 336 Ibs.
of Flakes.
. 102-2 Ibs.
. 102-2
102-2 ,
From these results it appears that the diastatic power of the
malt used is of little importance when working with cold-water
malt extract. The question arose, however, as to whether the
full yield of extract was given when employing this proportion
of diastatic solution. A second series of experiments was
therefore conducted to ascertain what differences resulted from
the use of varying amounts of cold-water extract. The following
are the results :
20 GRAMS OF FLAKES USED.
Diastatic Power of
Malt used.
Extract per 336 Ibs. of Flakes.
25 c.c. Diastase
Solution.
50 c.c. Diastase
Solution.
75 c.c. Diastase
Solution.
28
Ibs.
102-3
Ibs.
104-0
Ibs.
104-2
65
103-4
104-4
104-4
It will thus be seen that when using 50 c.c. of cold-water
extract an increase over the amount yielded by 25 c.c. is shown,
but that no further increase occurs when as much as 75 c.c. is
used, and when using 50 c.c. it does not matter whether the
malt has a diastatic power of as low as 28 or as high as 65 ;
hence 50 c.c. of cold-water malt extract is the proper quantity
to employ for 20 grams of material.
It will be noted by these experiments that, although on the
laboratory scale the details are such as to result in reliably
obtaining the full extract capable of being yielded by the raw
material, yet in practice the extract yield may fall short by as
much as 7 Ibs. per quarter, should the malt employed be of very
low diastatic power.
Under these circumstances it is sometimes of as much
importance to know what extract a definite proportion of raw
material will yield in practice, when mashed in conjunction with a
232
THE BREWER'S ANALYST
certain class of malt, as it is to know what extract can be
obtained analytically ; hence the remarks on p. 218.
4. Proteids or Albuminoids Total Albuminoids.
These are determined by Kjeldahl's method, as explained for total
albuminoids under Malt Analysis (p. 207).
Soluble Albuminoids. Twenty grams of the grain, ground
to powder, are digested for 1J hours in 200 c.c. of distilled water
at a temperature of 120 F. (48*8 C.), with occasional stirring.
The infusion is then cooled to 60 F. (15*5 C.) and filtered =
10 per cent, solution. Fifty c.c. of the filtrate are now evaporated
to dryness and the determination conducted as explained with
soluble albuminoids in Malt-wort Analysis (p. 208).
Insoluble Albuminoids. Difference between total and
soluble albuminoids.
5. Acidity. This is determined by titrating 50 c.c. of the
10 per cent, cold-water infusion as used for the estimation of
soluble albuminoids with sodic hydrate, using litmus as
indicator.
N
c.c. alkali used x '009 x 10 = per cent, acidity on the grain.
6. Mineral Matter OP Ash. Determined from 50 c.c. of the
10 per cent, cold-water extract as employed for the determination
of soluble albuminoids just described, and conducted as explained
under Malt Analysis (p. 204).
7. Moisture. Determined on 5 grams of the material, as
explained under Malt Analysis (p. 201).
ANALYSIS OF PREPARED EAW GRAIN (GRANULATED AND FLAKED
MAIZE AND RICE), CONDUCTED ACCORDING TO THE PRECEDING
INSTRUCTIONS, GAVE THE FOLLOWING :
Granulated.
Flaked.
Maize.
Rice.
Maize.
Rice.
Oil.
Extract per quarter (336 Ibs. )
,, per cent.
Total proteids or albuminoids
Soluble
Insoluble ,, ,,
Mineral matter or ash
Moisture . ...
0-98
98-44
75-90
9-20
0-62
8-58
0-30
1072
0-76
102-48
79-01
874
0-41
7-33
0-26
7'83
0-97
98-78
76-16
9-50
0-34
9-20
0-44
6-30
0-29
10315
79-53
8-53
28
8'25
0-32
7-43
METHODS OF ANALYSIS
233
ANALYSIS OF UNPREPARED RAW GRAIN (RAW MAIZE GRITS
AND RAW RICE).
The determinations to be made are exactly the same as with
the preceding prepared granulated and flaked maize or rice, and
are carried out in precisely the same manner, excepting that in
the determination of extract it becomes necessary to gelatinise
and cool the starch before adding the malt extract.
Twenty grams of the ground grain are placed in a beaker
together with 120 c.c. of distilled water and gradually boiled for
about 30 minutes, adding water, a little at a time, to replace
that lost by evaporation. The solution is then cooled to 150 F.
(65 '5 C.), 50 c.c. of malt extract added, and the operation carried
on as described, from this point, with prepared raw grain
(p. 229).
ANALYSIS OF UNPREPARED RAW GRAIN (RAW MAIZE GRITS AND
RAW RICE), CONDUCTED ACCORDING TO THE PRECEDING
INSTRUCTIONS, GAVE THE FOLLOWING :
Unprepared
Unprepared
Raw Maize Grits.
Raw Rice.
Starch .
6438
78-20
Oil
3'25
0-21
Extract per quarter (336 Ibs.)
Total proteids or albuminoids
99-50
9-00
106-00
7-73
Soluble
0-50
0-33
Insoluble ,, ,,
8-50
7-40
Mineral matter or ash
2-20
1-54
Moisture ....
870
10-92
Cellulose, gums, etc., by difference
12-47
1-40
ANALYSIS OF BLACK, BROWN, AMBER, AND CRYSTAL MALTS.
These materials are analysed in precisely the same manner as
prepared raw grain (granulated or flaked maize or rice).
We have, however, to alter the factor by which to multiply the
excess gravity between the mash and cold-water extract. The
average bulk occupied by the grains from 20 grams of any of
these malts is 6 c.c. ; the factor to multiply the excess gravity
between that of the malt and cold-water extract, calculated on
the basis shown in the footnote, p. 203, is therefore 3'26. Hence
in the determination of extract, specific gravity, minus 1000,
multiplied by 3'26, gives Ibs per quarter (336 Ibs). There is one
234
THE BREWER S ANALYST
other point, viz., with regard to black malt, it is often required
to test its colour value. This is best performed by examining a
'01 per cent, boiled and cooled solution in a 1-inch cell of
Lovibond's tintometer. One gram of the malt is weighed, ground
to powder, and boiled in about 200 c.c. of distilled water for 15
minutes, afterwards cooled and made up to 1 litre *= '01 per cent,
solution.
ANALYSES OP BLACK, BROWN, AMBER, AND CRYSTAL MALTS,
CONDUCTED ACCORDING TO THE PRECEDING INSTRUCTIONS,
GAVB THE FOLLOWING :
Black.
Brown.
Amber.
Crystal.
Extract per quarter (336 Ibs. )
57-75
57-12
84-53
58-26
,, per cent. .
44-30
44-04
65-02
45-07
Acidity of wort
29
23
19
17
Total proteids or albuminoids
6-11
7-13
7-62
8-71
Soluble
2-12
2-32
1-93
2-83
Insoluble ,, ,,
3-99
4-81
5-69
5'88
Mineral matter or ash
32
29
1-20
76
Moisture
5-37
6-23
4-14
2-12
BARLEY ANALYSIS.
It is not often that the analyst is submitted samples of barley
and asked to judge quality and give chemical analysis of the same,
yet the importance of analytical results are now being realised.
The following are the determinations to be made :
1. Extraneous matters.
2. Defective corns.
3. Weight per bushel.
4. Steely corns.
5. Character of endosperm.
6. Vegetative energy and capacity.
7. Oil.
8. Starch.
9. Proteids or albuminoids.
10. Mineral matter or ash.
11. Moisture.
1. Extraneous Matters. Determined as with Malt (p. 190).
2. Defective COPnS. These include those corns which are
broken, crushed, mouldy, damaged in dressing or by insects,
METHODS OF ANALYSIS 235
weathered in field, sprouted, heated in stack or very minute in
size.
Five hundred corns are taken promiscuously from the sample
and the percentages calculated.
3.' Weight per Bushel. As per Malt (p. 191).
4. Steely Corns. As per Malt (p. 191).
5. Character Of Endosperm. Obviously, if barley will
not germinate, vegetate, or grow, it is impossible to convert it
into malt. Hence vitality of the germ is one of the most
essential conditions of good barley, since should any sample
possess more than an extremely small percentage of the grain
incapable of germinating, there is con-
siderable loss, as all ungerminated corns
represent merely so much raw barley
in the finished malt, and apart from
yielding merely an infinitesimal extract
at the mashing stage, form breeding-
grounds for mould during vegetation
on the malt-house floor, and result in
the diastatic power of the malt being
low.
Defective vitality may arise from
under- or over-ripeness, incipient ger-
mination in the ear owing to a wet p IGi 75.
harvest, death of the germ through
heating in the stack, or improper storage, the attacks of insects
and vermin, or damage to the grain during threshing.
The best test for vitality is to grow a sample of the barley ; but
this takes time, and the practical man, purchasing as he does in
the open market, is therefore unable to avail himself of this
method of procedure.
The test is usually carried out by taking 100 corns pro-
miscuously from the sample without any picking or choosing,
and placing them in an apparatus known as Coldew's germinator
(fig. 75). It consists of a glass vessel with a constriction about
1J inches from the top, on which rests a porcelain plate provided
with 100 perforations. Into each of these a corn of barley is
inserted with the germ end downwards. The apparatus is nearly
filled with water, the plate inserted, a small quantity of sand
placed on top of the barley, and this is then moistened with water.
A wooden cover with a layer of felt is then placed over the sand,
and a small thermometer attached to the cover serves to indicate
the temperature at which the experiment is being conducted. Upon
236 THE BREWER'S ANALYST
allowing germination to proceed for a few days, the relative
degrees of vitality of the different corns can be readily estimated,
and the number of sluggish and dead corns seen at a glance.
6. Vegetative Energy and Capacity. According to the
percentage of grain in a sample of barley which, when placed
under favourable conditions for germination, vegetate within a
definite time (this at the ordinary temperature being generally
taken as 3 days), so is the vegetative energy; whilst the
term vegetative capacity is employed to express the
percentage number of corns which are found capable of germinat-
ing irrespective of time.
In a good sample of barley the vegetative energy should be not
less than 90 per cent., and the capacity not below 95 per cent.
The more closely these two characters correspond, the better,
since any great variation plainly indicates that the sample would
grow irregularly during malting.
7. Oil. Determined as per Raw Grain (p. 226), 5 grams being
taken and the extraction in a Soxhlet apparatus conducted for
5 hours.
8. Starch. As per Raw Grain (p. 227).
9. Proteids or Albuminoids. As per Malt (p. 205), 5
grams being taken, ground to powder, and treated according to
KjeldahPs method.
10. Mineral Matter or Ash. As per Raw Grain (p. 232).
11. Moisture. As per Malt (p. 201), 5 grams of the finely
ground material being dried for 3 hours in the water oven.
HOP ANALYSIS.
The following are the determinations to be made :
1. Extraneous matters.
2. Soft and hard resins.
3. Tannin.
4. Moisture.
5. Sulphur.
1. Extraneous Matters. A fair sample of the hops should
be taken by opening the pocket or bale and taking a piece from
the middle. This should include both the outside and interior of
the hops. A flake should then be selected right across the hops
so as to include as near as possible a portion of the outside and
inside of the sample. The flake may be about 5 grams weight,
and, without breaking it up, its exact weight should at once be
ascertained. Say, for example, we select exactly 5 grams. This
METHODS OF ANALYSIS 237
sample is now placed on a piece of white glazed paper, and, by
means of forceps, separated. Such a sample will be found to
contain leaves, stalks, etc. ; and these are then separated as
accurately as possible and,, weighed, the amount so found being
expressed as extraneous matters.
2. Soft and Hard Resins. Having separated the extraneous
bodies from the sample, as in the former experiment, and ascer-
tained the weight of the same, the hops, which in this instance,
including their moisture content, which must hereafter be reckoned
with, weigh, say, exactly 4'5 grams. They are now transferred
to a Soxhlet oil-extracting apparatus (fig. 73, p. 226) ; l 120 c.c.
of petroleum ether is now added to the distilling flask, and the
whole connected as shown in the figure. A light is now placed
under the water bath and the temperature raised and maintained
by the thermostat at a temperature of 155 F. (68*3 C.), which
causes the ether to circulate continuously through the hops. The
extraction, which proceeds slowly, is carried on for about 24 hours,
the flask being then disconnected from the apparatus, its contents
being filtered, whilst hot, through a small filter paper into a tared,
wide-mouthed flask, and the filter paper being thoroughly washed
with petroleum ether and the washings also collected.
The filtrate is now gently evaporated over the water bath, the
soft resins being left as a residue. The flask is now placed on its
side in the water oven, where it is maintained at a higher tempera-
ture than the boiling-point of ether, so that all traces of ether
are got rid of. The flask is now placed under the desiccator
and when cool weighed, the drying, cooling, and weighing being
repeated until the weight is constant.
In the meantime the hops in the Soxhlet apparatus are further
extracted by placing 120 c.c. of ordinary ether in the original
flask, again connected with the apparatus, and the flask heated as
before, excepting that the water in the bath is reduced in tempera-
ture to 135 F. (57 '2 C.), and the circulation of ether carried on
for a further 12 hours. The ethereal extract of the hard resins is
thus obtained, filtered through the paper previously employed for
the soft resins, washed with ether, and the evaporation and drying
carried on as before. The analysis of both extracts is carried on
in duplicate, and the mean of the results expressed in percentage
on the dry hops, thus :
Of the 4'5 grams of hops originally taken, we have to make a
1 Instead of adding the hops direct to the Soxhlet tube, they are preferably
placed in a thimble of bibulous paper (fig. 74, p. 227), this and its contents
being placed in the Soxhlet apparatus.
238 THE BREWER'S ANALYST
correction for moisture, and as this is found (p. 242) to equal
9 per cent., the 4'5 grams contain 0*4, so that the actual hops used
in our experiment equal 4'1 grams.
On extraction with petroleum ether the weight equalled 0-439
i no
gram of soft resins, therefore '439 x = 10'70 per cent.
preservative soft resins.
After extraction with sulphuric ether the resins obtained
equalled 0'136 gram, so -136x^=3-03 per cent, non-
preservative hard resins.
Heron points out 
