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DAIRY ANALYSIS

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DAIRY CHEMISTRY

For Dairy Managers, Chemists, and Analysts

A Practical Handbook for Dairy Chemists and others having

Control of Dairies
By H. DROOP RICHMOND, F.I.C., Chemist to the Aylesbury Dairy Co;

Contents. — I. Introductory. — The Constituents of Milk. II. The Analysis
of Milk. III. Normal Milk : its Adulterations and Alterations, and their
Detection. IV. The Chemical Control of the Dairy. V. Biological and
Sanitary Matters. VI. Butter. VII. Other Milk Products. VIII. The
Milk of Mammals other than the Cow. Appendices. — Tables. — Index.

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WATER ANALYSIS

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LONDON : CHARLES GRIFFIN & CO., LTD., EXETER ST. STRAND

THE LABORATORY BOOK

OF

DAIRY ANALYSIS

BY

H. DROOP RICHMOND, F.I.C.

ANALYST TO THE AYLESBURY DAIRY COMPANY LIMITED

ILLUSTRATED WITH PHOTOGRAPHS
BY THE AUTHOR

SECOND EDITION REVISED

LONDON

CHARLES GRIFFIN AND CO. LIMITED
EXETER STREET, STRAND

^ 1912

Of

^ LIBRARY

UNIVERSITY OF CALIFORNIA
DAVIS

BALLANTYNE & COMPANY LTD

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LONDON

PKEFACE TO SECOND EDITION

FOR some considerable time this little book has been
out of print, but the author has now found time to
make a few necessary corrections and add informa-
tion to bring it up to date. A number of new methods
have been added, and an endeavour has been made to
give information which will aid in the solution of those
practical problems which confront the dairy chemist.

October 1912 H. D. R.

PEEFACE TO FIRST EDITION

THIS work is intended to contain working directions
for the analysis of milk and dairy-products ; the esti-
mation of all constituents of diagnostic value is shortly
described in detail, and is in many cases illustrated
by photographs of chemists actually carrying out the
determination.

A chapter on the application of analysis to the solu-
tion of problems usually placed before the chemist is
included, and a very short summary of the composition
of milk and its products is given.

vi PREFACE

In the Appendix the composition and preparation of
the various solutions is detailed. Tables are given to
facilitate the working out of results ; these Tables
are condensed to occupy one page each, and the saving
of time by avoiding the turning over of pages will more
than compensate for the slight extra labour due to the
condensation.

While not intended to be a complete guide to the
analysis of milk, it is hoped that this work will afford
assistance to analysts, health officers, dairy students,
and those engaged in the supervision of dairies ; with
this object in view the more simple tests have been
described in a manner which will render their working by
persons other than chemists possible ; it must be remem-
bered, however, that though these methods are easy, they
are often fallaciously easy, and lack of chemical training
may lead to the making of errors, and the overlooking
of important points ; no amount of careful following of
directions can replace a thorough training in chemical
science and manipulation, and though simple tests have
a real value as a guide, they have not the reliability of

an analysis made by a skilled chemist.

H.D.R.

September 1905

CONTENTS

CHAPTER I
INTRODUCTION

PAGE

The Constituents of Milk — Products Derived from

Milk — Composition of Milk — and of its Products I

CHAPTER II
THE ANALYSIS OF MILK

Preparation of the Sample — Specific Gravity — Total
Solids — Ash — Mineral Constituents — Acidity — Fat
— Gerber . Method — Gravimetric Methods — Milk
Sugar — Proteins — Nitrogen — Aldehyde Figure
— Catalase — Relation between Fat, Solids not Fat,
and Specific Gravity 5

CHAPTER III
THE ANALYSIS OF MILK-PRODUCTS

Skim-milk — Cream — Butter-milk — Whey — Sterilised

Milk — Condensed Milk — Sour Milk — Milk Powder 43

CHAPTER IV

THE APPLICATION OF ANALYSIS TO THE SOLUTION OF
PROBLEMS

The Detection of Adulteration — Preservatives — Poor
Milk — Sweet Milk — High Colour — Sour Milk —
Unusual Taste — Urine — The Freshness of Milk
— Dirty Milk — Detection of Adulteration of Cream
— and Skim-milk 51

vii

viii CONTENTS

CHAPTER V

THE ANALYSIS OF BUTTER

Water — Curd and Salt — Preservatives — Examination of
the Fat — Reichert-Wollny Method — Soluble and
Insoluble Fatty Acids and Mean Molecular Weight
— Ave - Lallemant Method • — Phytosteryl Acetate
Test • — Density — Examination under Polarised
Light — Iodine Absorption — Refractive Index —
Detection of Adulteration — Application of Analysis
to Butter-making

CHAPTER VI
THE ANALYSIS or CHEESE

Water, Ash, and Salt — Fat — Nitrogen — Products of
Ripening — Examination of the Fat — Detection of
Adulteration — Application of Analysis to Cheese -
making

TABLES FOR CALCULATION
APPENDIX. Standard Solutions
INDEX

CHAPTER I
INTRODUCTION

Milk consists of (i) fat in small globules (Fig. i)
ranging in size from o.oi mm. in diameter to 0.0016 ;
(2) milk-sugar and (3) various salts in solution in
wa'er ; (4) caicin, combined with lime and phos-
phoric a^id; and (5) albumin in loss perfect solution.

i. — Milk (magnified 400 diameters).

There are in addition (6) other compounds in small
quantities, including enzymes or natural ferments.

The fat will be treated of in the section on butter ;
the milk-sugar belongs to the class of carbo-hydrates
and crystallises with i OH2, and is one of the hexa-
bioses. It rotates the plane of polarisation, its specific
rotatory power being 52.5° for the crystallised sugar ;
and reduces solutions of copper salts.

Casein is a protein belonging to the class of the

I A

2 DAIRY ANALYSIS

phospho-proteins ; it contains carbon, hydrogen, oxygen,
nitrogen, sulphur, and phosphorus ; in milk it exists as
a sab of lini'3 and soda combined with calcium phos-
phate ; a^ids precipitate the free casein if dilute, while
strong acid* re-dissolve it. Rennet splits casein up
in o curd, which 13 a combination of para-casein with
the limo and vhe cak-ium phosphate of the casein, the

FIG. 2. — Cream (magnified 400 diameters).

soda being split off, and whey protein which is free
from phosphorus.

Albumin is a protein which is distinguished by
coagulating on heating to 70° C. ; in milk it probably
exisos as a salt, and this does not coagulate until the
m Ik is acidified. Unaltered albumin is not precipi-
tated by acids.

When micro-organisms act on milk various products
are formed ; the most important change is the forma-
t ion of lactic acid from the sugar, which causes milk to
become sour, and curdles it by precipitating the casein.

The fat globules are lighter than the aqueous serum,
and they tend to rise. Cream (Fig. 2) is the upper
portion of milk after standing, and differs from milk
practically only in that it contains more fat and pro-

INTRODUCTION 3

portionately less serum. Skim-milk is the milk de-
prived of the bulk of its cream, and if the separation
of cream has been performed in a centrifugal separator
it is practically free from fat and contains only the
aqueous serum. This is termed separated or machine-
skimmed milk.

When cream (or milk) is suitably agitated for seme
time, the fat globules coalesce to small granules, and
these after working together into a nearly homogeneous
mass form butter. This is chiefly composed of fat, but
contains some water and other constituents of milk.
The residue is termed butter-milk, which does not differ
greatly from skim-milk in composition.

By treating milk with rennet, curd is separated ; this
carries down the bulk of the fat, and after pressing,
salting, and ripening, partly by the action of miero-
orgamsms and partly by the action of the natural
ferments of milk, it is converted into cheese ; cheese
consists essentially of fat, para-casein, and prc ducts de-
rived from the latter together with seme water and salts.

The following Table gives the average morning and
evening milk for each month, and represents the per-
centage composition during 1911 :

TABLE I

MORNING MILK

EVENING MILK

Month

Sp. gr.

Total
Solids

Fat

Solids
not
Fat

Sp. gr.

Total
Solids

Fat

Solids
not
Fat

January

0323

2.64

o/
3-68

8.96

.0321

2J36

3-°9°i

8-9°5

February

•0325

2-55

3-57

8.98

.0322

2.79

3-83

8.96

March

0324

2.41

3-49

8.92

.0321

2.66

3-76

8.90

April .

0321

2.31

3.48

8.83

.0318

2-59

3-77

8.82

May .

0323

2.12

3.26

8.86

.0319

2.51

3-68

8.83

June .

0323

2.09

3-24

8-85

.0316

2.42

3-64

8.78

July .

0316

2.17

3-44

8-73

,0309

2-35

3-74

8.61

August

0309

2.13

3-54

8.59

•0304

2.42

3-90

8-52

September

0311

2-35

3-69

8.66

.0306

2.68

4.07

8.61

October

0315

2.52

3-76

8.76

.0312

2.82

4.07

8-75

November

0316

2.65

3-83

8.82

.0314

2-85

4,05

8.80

December

0318

2-54

3-72

8.82

•0315

2.69

3-88

8.81

4 DAIRY ANALYSIS

In the Table below is given the average percentage
composition of milk and the various products derived
from it.

TABLE II

Water

Fat

Milk
Sugar

Proteins

Mineral
Matter

MILK

87.25

3.75

4.75

3.40

0.75

Separated Milk

90.40

0.20

4-95

3-57

0.78

Thick Cream .

39-37

56.09

2.29

1-57

0.38

Thin Cream

67.50

25.67

3-66

2.60

0-57

Fresh Butter .

12.99

85.81

0.37

0.74

0.09

Salt Butter

13-78

82.97

0.39

0.84

2. 02*

Butter-milk

90-33

0.76

4.78±

3-33

0.80

Whey

93.21

0.30

4.99

0.92

0.58

Curd .

49-43

27.38

2.04

20.00

I.I5

Cream Cheese .

30.66

62.99

0.26J

4-94t

I.I5

Soft Cheese

50.04

27.50

9

L8-3.il

4.12*

Hard Cheese

33.89

33-00

1.90$

27.56t

3.65*

Half-skim Cheese

37-35

24.61

9

32.40!

5.65*

* Including added salt.

t Including products of ripening.

J Including lactic acid.

CHAPTER II
THE ANALYSIS OF MILK

Preparation of the Sample. — A milk sample con-
veniently consists of a five-ounce bottle filled nearly
full ; if the sample is to be representative of a bulk,
the milk (whether in a churn, pail, can, or jug)
should invariably be well stirred before the sample is
taken in order to distribute the cream which always
tends to rise to the surface. Samples taken in a dairy
or other place for testing on the premises may, how-
ever, be taken in cans, and if the sample is one
frequently taken from the same source a distinguishing
mark may be stamped on the can.

On receipt of the sample in the laboratory it should
invariably be stirred before any portion is withdrawn
for analysis ; violent shaking is to be deprecated, as
not only is there a tendency to churn the fat but air
bubbles, which do not separate immediately, are in-
cluded, and prevent accurate measurements, especially
of specific gravity. In cold weather samples are often
frothy, and while they remain cold the air bubbles
separate very slowly. Freshly drawn milk is also
frothy, and the fat being in the liquid condition has a
lower specific gravity than it has after solidification.
If the sample is turning sour there is often difficulty in
uniformly distributing the cream, and violent shaking
may have to be resorted to ; if any of the fat is churned
or becomes churned in this operation, the lumps of
churned fat should be removed, dried, and the fat
extracted with ether and weighed ; the total weight of
milk is ascertained, and the percentage of churned fat
calculated. The remainder of the sample is analysed
separately.

Milk which is sour and curdled is mixed by turning

6 DAIRY ANALYSIS

the whole sample into a beaker, and whipping with a
brush made of fine wires.

Always determine the specific gravity of every
sample if possible.

FIG. 3. — Putting Lactometer into Milk.

Estimation of Specific Gravity by Lactometer.—

Nearly fill a cylindrical vessel of depth such that
the lactometer will float, and at least % inch wider
than the lactometer ; a glass jar, or tin pot, or even
a milk-can serves well. Hold the lactometer at an
angle (Fig. 3), and cautiously lower it into the milk,

THE ANALYSIS OF MILK 7

taking care that no air bubbles are retained in the space
between the upper and lower bulbs (see Fig. 4) ; when
the upper bulb is partially below the surface, raise to an
upright position and immerse the lactometer to the 30°

FIG. 4. — Vieth's Lactometer.

mark, and let it find its own level. When steady read off
the point where the surface of the milk cuts the stem ;
this point is not visible, as the milk is drawn up round
the stem by capillary attraction (Fig. 5), and must be
mentally estimated. Some little practice is required

8

DAIRY ANALYSIS

to do this, and the reading may be obtained by ob-
serving the point on the stem to which the milk
reaches, and adding a constant amount for the height
of the meniscus, usually \ degree ; thus in the
figure the true reading of the
lactometer is 32.5°, the apparent
reading is 32°, and with \ degree
added on the true reading is
obtained.

Immerse the bulb of a ther-
mometer in the milk, and stir the
milk till the temperature is con-
stant ; correct the reading to 60°
F. by means of the table given
on p. 88 or by the milk scale
(p. 40). To use the table, find
in the top line column the
specific gravity (or the nearest
figure to the left), and in the
left-hand column the tempera-
ture ; where the lines intersect
the corrected specific gravity is
given (adding on, if the specific
gravity found is not an exact
degree, the decimals).

A thermo - lactometer, i.e. a
lactometer which contains a
thermometer, may be used, and
the temperature can then be read
off from the upper scale at the
same time as the specific gravity
(Fig. 6).

Never take a specific gravity reading without also
noting the temperature and correcting to 60° F.

The lactometer should be checked by the gravi-
metric method, to make sure that the scale is
correct.

A lactometer does not give accurate results if a film
of milk is allowed to dry on it ; if a sample has been

]?IG. 5. — Lactometer
in Milk.

The jar in the figure
has been filled to the
brim with milk in
order to show clearly
the effect of capil-
lary attraction ; it is
neither necessary nor
advisable to do this
when testing milk.

THE ANALYSIS OF MILK 9

tested and the lactometer removed, and allowed to
stand, it must be washed and dried before being used
for another sample.

There is usually little objection, however, to removing

FIG. 6. — Thermo-lactometer.

a lactometer from one sample and, after draining,
placing it at once in another sample ; but if the sample
is likely to be the subject of legal proceedings or is
otherwise important, the lactometer should always be
cleaned before testing.

The Gravimetric Estimation of Specific
Gravity. — Dry a Sprengel tube (Fig. 7) by washing

10

DAIRY ANALYSIS

with distilled water, alcohol, and ether, and placing in
the water-oven ; aspirate air through while still hot,
cool, 'and weigh. Fill the tube with distilled water, and
place it in a vessel containing water at 15.5° C. till the

^. 7,— Sprengel Tube.

water inside no longer alters in volume ; adjust the
level of the water accurately to the mark on the wider
tube by cautiously applying filter-paper to the
narrower end ; wipe the outside of the tube dry, and
weigh. The difference between the weight of the full

THE ANALYSIS OF MILK II

and the empty tube gives its capacity in grammes of
water at 15.5°.

Empty the water, and rinse the tube several times
with the milk, and then fill it with milk ; allow the
tube to stand a minute to permit air bubbles to rise,
suck or blow these out, and fill the tube completely.
Immerse the tube in water at 15.5° C. till the
volume ceases to alter, and then wipe dry and weigh as
before. The difference between the full and the empty
tube gives the weight of milk, and this divided by the
capacity in grammes of water at 15.5° gives the specific
gravity at 15.5°.

The capacity of the tube once determined remains
constant, and it need not therefore be determined every
time ; the weight of the empty tube should, however,
be taken occasionally.

Rise of Specific Gravity of Milk on Standing.—
If the milk is freshly drawn or has been recently
heated, the fat is in the liquid condition, and its specific
gravity is lower than when solid. The solidification
of the fat globules takes some time, and twelve to
twenty-four hours may elapse before the maximum
specific gravity is attained. If the milk is frothy,
air bubbles may cause the specific gravity to appear
too low.

The maximum specific gravity is taken as the correct
figure.

Estimation of Total Solids. — Weigh a basin either
of platinum, tantalum, fused silica, or porcelain, prefer-
ably 2f in. wide and flat-bottomed; pipette in 5 c.c. of
milk and weigh again ; the weighing should be rapid,
but the exactitude of weighing need not be more than
2 mg. Place the basin on a water-bath (Fig. 8), and
from time to time break the skin with a needle ; when
apparently dry place in a water-oven (Fig. 9), and
continue the drying for four hours, cool in a desiccator,
and weigh ; replace in the oven for periods of one hour
each, cool and weigh, until the loss in one hour is less
than i rag. The weight of the residue divided by the

12 DAIRY ANALYSIS

weight of milk taken and multiplied by 100 gives the

percentage of total solids.

(Babcock's method) The basin may be loosely packed with

ignited asbestos, if
great accuracy is
required ; (Stokes'
method) if speed is
wanted, a few drops
of a 10 per cent, so-
lution of acetic acid
in alcohol, or (Revis*
method) an equal
volume of acetone,
may be added, and
FIG. 8. — Water-bath. the time of drying

canthenbe curtailed.
Estimation of Ash. — The total solids are ignited

in a muffle furnace (Fig. 10), which should not be

allowed to become hotter than a dull red heat ; to

facilitate burning, upstand-
ing portions of the ash may

be broken down by touch-
ing with a platinum wire ;

when all the carbon is

burnt away the basin is

cooled in a desiccator and

weighed. The ignition may

be performed over a Bun-
sen burner (Fig. n), the

point of the flame of which

should barely be allowed

to touch the bottom of

the basin, or an Argand

burner may be used; the FIG. 9.-Water-oven.

basin should be covered

with a platinum lid. It is very important not to heat

the ash to too high a temperature.
Estimation of Soluble and Insoluble Ash.—

Fill the basin with hot water and filter through a

THE ANALYSIS OF MILK 13

small ash-free filter ; wash with hot water. Place the
filter and its contents in the basin, and ignite ; the

FIG. 10. — Muffle.

residue is the insoluble ash and the soluble ash can be
obtained by difference.

Estimation of Alkalinity, Chlorine, Lime, and
Phosphoric Acid. — To the filtrate containing the
soluble ash add a drop or two of phenolphthalein

solution, and titrate with — sulphuric acid (see

14 DAIRY ANALYSIS

Appendix) till the colour is discharged. Each cubic
centimetre of acid indicates 0.0044 gramme C02 as

FIG. ii. — Tripod, Bunsen, and Desiccator.

carbonates. [Note. — The alkalinity is not all due to
carbonates, a little phosphate is present.]

To the solution add a few drops of potassium

chromate, and titrate with — silver nitrate solution

10

(see Appendix) till a red colour just appears. Each cubic
centimetre of silver solution indicates 0.00355 gramme

THE ANALYSIS OF MILK 15

of chlorine. [Note. — A little of the chlorine, about o.oi
per cent., is lost on ignition of the total solids.]

For the estimation of lime and phosphoric acid, it is
advisable to take another quantity of milk (10 c.c. or
25 c.c. being preferable) ; this is dried on the water-
bath, ignited, the ash dissolved in a little hydrochloric
acid, and the solution boiled; after cooling slightly,
ammonia is added drop by drop till a permanent tur-
bidity appears, and hydrochloric acid added in quantity
sufficient to remove this, excess being avoided. The
solution is brought just to the boiling-point, and a satu-
rated solution of ammonium oxalate added drop by
drop, so long as a precipitate appears ; the solution is
kept hot (in a water-oven) for at least two hours, and
filtered through a small ash-free filter ; the precipitate
is transferred to the filter, washed with hot water, and
the filter placed in a tared basin, and ignited over a small
flame ; when the filter-paper is all burnt away, the
precipitate is moistened with a solution of ammonium
carbonate, dried, and very gently ignited. The pre-
cipitate, now converted into calcium carbonate, is
weighed, and the weight of lime found by multiplying
by 0.56 ; it is usually slightly grey, and contains traces
of iron, which are small enough to be neglected.

To the filtrate is added 5 or 10 c.c. of magnesia
mixture (see Appendix), and about one-tenth its volume
of strong ammonia ; and after stirring well the liquid
is allowed to stand at least 12 hours ; the precipitate
is washed by decantation with dilute ammonia,
transferred to a filter, and the washing completed ;
the filter is placed in a weighed basin, and ignited
at first gently, and finally very strongly till white ;
the residue of magnesium pyrophosphate is weighed,
and the amount of phosphoric acid (as P205) found
by multiplying by 0.6396.

For the determination of other mineral constituents,
works on mineral analysis should be consulted.

The Estimation of Acidity. — Place 10 c.c. of
milk in a white porcelain basin (Fig. 12), add i c.c. of

i6

DAIRY ANALYSIS

phenolphthalein solution (see Appendix), and run in

N

from a burette — caustic soda, or other alkali solution,
strontia being recommended (see Appendix), in drops,

FIG. 12. — Estimation of Acidity.

stirring constantly, till a faint pink colour, equal
to that given by adding I drop of a o.oi per cent,
solution of rosaniline acetate in 96 per cent, alcohol to
II c.c. of the same milk, is produced; each TVc.c. of

- alkali solution represents i° acidity, and the degrees

THE ANALYSIS OF MILK 17

multiplied by 0.009 wiU give the acidity in percentage
of lactic acid.

If greater accuracy is required 50 c.c. may be taken,
and 5 c.c. of phenolphthalein solution added ; each
\ c.c. will then represent i° acidity.

The Volumetric Estimation of Fat— Gerber's
method of fat estimation consists in reading the volume
of fat brought into the graduated neck of a bottle by

FIG. 13. — Leffmann and Beam Machine.

centrifuging, after dissolving everything in the milk but
fat by strong sulphuric acid (the essential part of Bab-
cock's method) with the addition of a little amyl alcohol
to help the fat to separate (the essential part of Leffmann
and Beam's method (Fig 13) ). In chemical principles
Gerber's method is nothing but Leffmann and Beam's,
and a description of one only differs in details from that
of the other ; as, however, the details of Gerber's method
render it more generally suitable, it will be described in
preference to its predecessor.
Apparatus, — The essential apparatus consists of :

B

i8

DAIRY ANALYSIS

Acidobutyrometers or Test-bottles. — About 22 c.c. capa-
city with a long stem expanded to a conical bulb at the
top, and graduated in percentages of fat ; the bottom is
open and contracted to a neck, which is closed by an
india-rubber cork when in use. A suitable stand for
these is provided.

The stems are made either round, flat, square, or with
a magnifying scale ; the patterns other than round give
a wider and, by many, a more easily read scale.

The test-bottles can now be checked at the National

FIG. i4A.

Gerber Machine.

FIG. 146.

Physical Laboratory, who certify the correctness of the
graduated scale.

Measuring Apparatus. — n c.c. pipettes for measuring
the volume of milk taken for the test ; 10 c.c. pipettes
for measuring the acid ; and i c.c. pipettes for the amyl
alcohol. Burettes or automatic measuring apparatus
may be used.

Centrifuges. — A centrifuge is necessary to rapidly bring
the fat into the graduated neck (Fig. I4A). In the
smallest size this consists of two long cups hinged on
a bar, which is fixed to the top of a vertical spindle
running in plain bearings. This is driven by means of
a strap round a loose pulley, or by means of a string.
The larger machines have a disc carrying four or more
cups, provided with a cover, and fixed to the top of a

THE ANALYSIS OF MILK 19

vertical spindle running on ball bearings. The driving
is performed either as in the two-bottle machine, by a
string wound round the spindle or by a handle. Very
large machines are fitted with a steam or water turbine,
or an electro-motor (Fig. 143), and may be provided with
heating apparatus to keep the disc warm while running.

Hot-water Tank. — If the disc is not kept warm while
running the bottles must be placed in water between
60° and 70° C., before reading, in a small tank.

The Process. — Place a sufficient number of bottles in
the stand, open end upwards, and to each add 10 c.c.
of sulphuric acid (see Appendix) ; add n c.c. of milk to
each by means of the n c.c. pipette ; then add i c.c. of
amyl alcohol (see Appendix).

To measure with a pipette : place the constricted end
in the liquid, and draw with the mouth till the level of
the liquid is at least one inch above the mark on the
upper stem ; rapidly remove the mouth, and place the
forefinger over the top ; the finger must not be wet,
though it may with advantage be slightly damp ; if this
is done with sufficient rapidity, the liquid is above the
mark on the upper stem, if it is not it must be drawn
up again. Carefully and slightly raise the finger to
allow the liquid to run down slowly to the mark, then
stop the flow by pressing the finger on the top ; this^
operation requires some practice, but presents no real
difficulty. Keeping the finger pressed down on the top,
lift the pipette out of the liquid, and, taking care not to
let any drops fall while moving, place the end of the
pipette inside the neck of the bottle (Fig. 15) ; hold the
pipette slanting, and let the point touch the side of the
neck. On lifting up the forefinger the contents will
run out down the side of the bottle. Let the pipette
drain a few seconds, and remove it, but do not blow
out the last drops. It is essential that the milk be
measured with great accuracy, but there is less need for
exactitude with the acid or amyl alcohol, as slight
variations of these do not affect the results ; it is as well,
however, to cultivate a habit of accuracy.

20

DAIRY ANALYSIS

After measuring the three liquids, which should
float in three distinct layers, with little or no browning
at the junction of the acid and milk, insert a cork ;
the bottle should be held with the left hand, and the

FIG. 15. — Measuring Milk.

cork screwed in, not pushed in, with the right ; do not
exert too much force or the bottle may break. If there
is marked browning the milk has either been run in
too fast or has not been run down the side of the
bottle, and the experiment is best repeated.

THE ANALYSIS OF MILK 21

Hold the bottle by the stem, and by the cork, keeping
a slight pressure on the cork, and mix the contents by
shaking ; when all the white particles of curd have dis-
appeared, but not before, invert the bottle to allow the
acid to run out of the neck, and then turn it upright ;
repeat this several times till the acid that was in the
neck has completely mixed. The bottle is now almost
too hot to hold, from the heat developed by the action
of the acid, and its colour is brown ; place it in the
centrifuge. Treat the other bottles in the same way,
and arrange them in order in the centrifuge. It is well
to mark each cup with a number to avoid errors.

The shaking of all the bottles may be done at once
by means of the author's stand (Fig. 16), in which the
bottles are held by being pushed into slits in the india-
rubber plate ; the hand should be placed over all the
corks to prevent them from coming out, and the con-
tents of the bottles from being spilt. Other convenient
stands are also made.

If a number of samples insufficient to fill the disc
is being tested, care should be taken to place them
symmetrically so as to preserve the balance of the
machine ; a bottle filled with a mixture of equal parts of
acid and water may be kept to make up an even number
of bottles should an odd number of samples be tested.

Screw on the cover, and rotate the machine at about
1000 revolutions per minute for three or four minutes ;
modern centrifuges are usually turned with a handle ;
if there is a plain spindle, with a projecting piece,
place the eye of the cord on the projection and turn
the machine round counter-clock-wise till the cord is
wound round the spindle ; take the handle in the
hand, pull hard, and the disc will spin ; usually this
must be done twice. If there is a strap, place this half
round the pulley, and pull with the right hand in a
somewhat downward direction, keeping the strap taut
with the left hand, and continue giving sharp pulls till the
disc spins rapidly ; the pull must be downward as well
as forward, or the pulley will not engage the spindle ;

22 DAIRY ANALYSIS

when the speed slackens, a few further pulls are neces-
sary. If a string with two handles is provided, this is
wound once completely round the spindle (or the
pulley on the spindle) ; take a handle in each hand,
and pull with the right hand, keeping the string taut
with the left hand, and at the end of the pull continue
the motion of the left hand to loosen the string round
the spindle ; pull back with the left hand keeping the
string very loose, and then repeat the stroke. This
method of driving requires care, but is, when learnt, a
most satisfactory way of spinning the disc ; when a
sufficient speed is attained the string is allowed to
hang loosely, the handles being placed on the bench
at each side. If the string is not properly loosened
at the end of the stroke, or on the return stroke, it
winds up, and the handles must then be immediately
dropped, or the hands may receive a nasty blow.
Unbleached blind-cord is a suitable material for the
string, and a good supply should be kept, as the string
wears.

During the running the disc may be kept warm by
means of a Bunsen burner or a spirit-lamp placed
underneath near the edge, with a flame so adjusted
that it just touches the disc.

The disc should be stopped gently, not suddenly,
and the cover unscrewed. Do not take hold of the
boss, in the centre of the cover, when the machine is
running at high speed.

If the disc is not kept warm, place the bottles, after
stopping the machine and removing the cover, in water
kept at 60° to 70° C. ; the small tank provided with
the apparatus is nearly filled with water at the required
temperature, and a spirit-lamp or Bunsen burner used
to keep it warm.

After one minute the bottles may be read ; hold the
bottle (Fig. 16) by the top with the left hand and by
the cork with the right, at a level with the eye ; the
position of the bottle should be as nearly vertical as
possible. By gently moving the cork, the lower level

THE ANALYSIS OF MILK 23

of the fat column is adjusted to one of the longer lines
indicating percentages of fat, and the point on the scale
where the lowest part of the curved upper limit stands

FIG. 1 6. — Reading Bottles.

is read off ; a convenient method of reading is to count
first the number of whole percentages of fat (indi-
cated by the longer lines), and then the number of
small lines above this, each small line indicating o.i
per cent, of fat. Fig. 17 shows a sample reading 3.6
per cent, of fat ; it is quite easy to read to half a small
division or 0.05 per cent.

24 DAIRY ANALYSIS

Every bottle should be read twice to make sure that
there is no error in the first reading.

The following are sources of error :

(a) Faulty graduation of the bottle ; this

is rare.

(6) Chemicals not equal to specification;
it is important that the specification for
these be strictly adhered to.

(c) Insufficient mixing of the milk, acid,
and amyl alcohol ; this is indicated by
the fat being cloudy, and obstinately re-
fusing to become clear.

(d) Mixing of the milk and acid before
addition of the amyl alcohol ; a brown
colour of the fat is usually found here.

(e) Allowing a portion of the fat to remain
in the little conical bulb ; if the fat is
too low down on the scale for con-
venient reading, and the cork is not
pushed in carefully, the fat is liable to
jump up, as it is raised ; if the fat is too
high, it may partially occupy the conical
bulb; in each case the fat must be
allowed to run down before reading.

When the corks have been used for some
time, they do not fit the necks of the bottles
FIG. 17. so well as when new, and are liable to slip
BottlT ou^> anc^ SP^ ^he acid mixture ; the times
when they are most liable to come out are,
when shaking the bottle, when removing it from the
disc, when removing it from the warm water, and when
pulling down the cork to adjust the fat layer. As acid
is detrimental to the clothes, always keep a bottle of
ammonia handy, and soak the acid- bespattered garment
liberally with this, should any be spilt ; if acid is spilt
on the hands or face, a copious stream of cold water
is the remedy, but do not use ammonia ; even strong
sulphuric acid spilt on the flesh rarely does harm if
washed off at once, and plenty of water is used.

THE ANALYSIS OF MILK 25

When the bottles have been read, turn them cork
upwards in the stand, remove the corks, and empty
the contents of the bottle into a convenient pot, not
down a sink. The pot when full may be emptied down
a well-flushed drain ; rinse the bottles two or three
times in hot water and leave to drain open end down-
wards ; an occasional clean with a brush when the
inside becomes dingy is necessary. The corks should
be put in a basin and washed several times with hot
water and allowed to dry.

Care of the Machine. — The bearings require lubrica-
tion ; an oil-can and a supply of suitable oil is provided
with the machine. If the ball-bearings wear loose,
they can be adjusted by means of a collar in the top
bearing. If a bottle breaks in the machine remove the
cup and wash it carefully, and should acid be spilt on
the disc, wash this too.

The machine should be clamped and screwed to a
firm bench or table, preferably close to a leg.

If separated milk is being examined a special bottle
with narrow neck should be used, and the time of
centrifuging increased.

Cream cannot be tested direct, as the scale does not
go beyond 9 per cent., or in some bottles 6 or 7 per
cent., and a special bottle may be used. But cream
can be tested in the ordinary bottles by the following
method ; if a thin cream (containing less than 32 per
cent, fat) is to be examined, use a 3 c.c. pipette in place
of the ii c.c. pipette ; fill the bottle with acid as
before, and then add 8.2 c.c. of water from a pipette
graduated in -^ c.c. ; fill the 3 c.c. pipette with cream,
adjusting the upper level very accurately to the mark,
and wipe the outside of the stem ; hold the pipette
vertically over the centre of the opening and allow the
cream to run directly into the water and blow out the
last drops ; finally, add the amyl alcohol, and proceed
as described for milk.

For thicker creams, a small balance weighing to 0.05
gramme (Fig. 18), and a pair or pairs of accurately

26

DAIRY ANALYSIS

balanced tin pots are necessary ; place sufficient
cream in one pot to fill it nearly half full, and put
this on one pan of the balance ; place the other pot
on the other pan and pour in separated milk or

FIG. 1 8. — Weighing Cream.

water till exactly balanced. Mix the contents of the
two pots by pouring backwards and forwards several
times, and measure out the mixture as directed for
thin cream.

Use the following Table for the calculation of results ;
the first column is the reading observed ; if thin

THE ANALYSIS OF MILK 27

cream was tested, its percentage of fat is found in the
column headed " Undiluted " ; if thick cream was
examined, the column headed " Diluted " will give the
percentage of fat.

TABLE III

FOR CALCULATING FAT IN CREAM

The Table should be checked by a gravimetric method, and may

require a slight correction added or subtracted which may

vary with each pipette.

Reading

Diluted

Undiluted

Heading

Diluted

Undiluted

8.5

63.5

31.8

6.7

49.4

24.8

8.4

62.7

31.4

6.6

48.7

24.4

8-3

61.9

31.0

6.5

47-9

24.0

8.2

61.1

30.6

6.4

47-2

23-7

8.1

60.3

30.2

6-3

46.4

23.3

8.0

59-5

29.8

6.2

45-7

22.9

7-9

58.8

29-5

6.1

44.9

22.5

7.8

58.0

29.1

6.0

44.1

22.1

7-7

57-2

28.7

5-9

43-4

21.8

7.6

56.4

28.3

5.8

42.6

21.4

7-5

55.6

27.9

5-7

41.8

2I.O

7-4

54.8

27.5

5.6

41.1

20.6

7-3

54-o

27.1

5-5

40.3

20.2

7.2

53-3

26.7

5-4

39-5

19.8

• 7-i

52.5

26.3

5-3

38.8

I9.5

7.0

5i.7

25-9

5-2

38.0

I9.I

6.9

50.9

25-5

5-i

37-2

I8.7

6.8

50.2

25.2

5-0

36.4

I8.3

In the " Sinacid," " Sal," and " Neusal " methods an
alkaline solution is substituted for the acid of the
Gerber process, and iso-butyl alcohol for the amyl
alcohol. Gerber bottles are used for these methods ;
ii c.c. of alkaline solution, 10 c.c. of milk, and 0.6 c.c.
of iso-butyl alcohol (which is usually coloured by a
dye) are measured into the tubes. The mixing and
centrifuging are done as in the Gerber method, but
the temperature of the water-bath is 45° C. The
coloured alcohol passes into the fat, and colours the
layer, which is consequently easy to read.

28 DAIRY ANALYSIS

While the substitution of the alkaline solution avoids
the objections to a strong acid, this method has the
drawback that the corks become slippery and tend to
come out of the bottles.

Gravimetric Estimation of Fat. — Of the numerous
methods for the estimation of fat, the Storch, the Ritt-
hausen, the Werner-Schmid, and the Gottlieb methods
all present advantages.

The Storch Method. — Place three or four grammes of
ignited kieselguhr in a basin, and pipette 10 c.c. of
milk in such a manner that it is all absorbed by the
kieselguhr ; dry on the water-bath with occasional
stirring to break up lumps, grind fine, and transfer to
a fat-free thimble, rinsing out the basin with fresh
quantities of kieselguhr ; place the thimble in a Soxhlet
extractor, rinse the basin, pestle, &c., with ether, and
pour this into the thimble ; extract the kieselguhr
with ether.

The Ritthausen Method. — See Estimation of Proteins,

P- 34-

The extraction in these methods is performed by
attaching a weighed flask to the bottom of the
extractor to receive the ether containing the fat, and
connecting the extractor to an upright condenser ; the
flask is immersed in water kept warm by a small flame,
and the ether continually distils up, is condensed, and
runs back into the extractor, from which it siphons
back into the flask when the extractor is full.

The kieselguhr should be extracted about four hours,
and casein about one and a half hours, after which the
ether is distilled from the flask, and the fat freed from
ether by placing in a water-oven for twenty minutes,
blowing into and rotating the flask every five minutes.
After cooling for a quarter of an hour, the flask is
weighed, and the increase of weight represents the fat.

It is advisable to return the flask to the water-oven
for a second period, and re-weigh to make sure that
all the solvent has been removed. The fat may be
melted and dissolved in petroleum ether which is

THE ANALYSIS OF MILK 29

carefully decanted from any residue ; by successive
treatments with small quantities of petroleum ether
all the fat may be removed, and the flask, with any

FIG. 19. — Soxhlet Extractor.

small particles of kieselguhr that may have passed
into it, re-weighed.

The Werner- Schmid Method. — Pipette 10 c.c. of milk
into a Stokes tube (Fig. 20), add 10 c.c. of strong
hydrochloric acid, and heat over a flame with constant
shaking, till the fat, on standing a short time, collects in
a clear layer on the surface ; cool the contents of the

30 DAIRY ANALYSIS

tube, and add 30 c.c. of ether, cork the tube, and
shake well ; allow the tube to stand till the ether has
separated in a clear layer; remove as much ether as
possible, preferably by means of washbottle tubes, to
a weighed flask ; add about 20 c.c. more ether,
shake well, allow the ether to settle clear, and
remove as before, and again add about 20 c.c.
of ether, shake, allow to settle, and remove
the clear layer. Distil off the ether, dry, and
weigh as above.

Gottlieb's Method. — Place 5 c.c. of milk in a
stoppered tube, add successively 0.5 c.c. of
ammonia, 5 c.c. of alcohol, 12^ c.c. of ether,
and 12 \ c.c. of petroleum ether ; mix after
each addition, and allow to stand ; when a
clear layer has separated, mix again, allow to
separate, mix once more, and allow the clear
Stokes Ia7er ^° completely separate.
Tube Remove the ethereal layer as completely

as possible by washbottle tubes to a flask,
and add and remove three successive portions of a
mixture of equal parts of ether and petroleum ether.
Evaporate the solvent, dry, and weigh as above.
Extract with petroleum ether and weigh the empty
flask.

Estimation of Milk Sugar. — This may be estimated
either polarimetrically, or gravimetrically ; the results
in either case are expressed as anhydrous sugar.

Polarimetric Estimation. — 50 c.c. of milk are measured
into a dry flask, and a quantity of water equal in cubic
centimetres to the sum of

(a) The degrees of gravity divided by 20.
(6) The percentage of fat divided by 1.8.
(c) A. quantity to convert scale readings into
percentages of anhydrous sugar ; if the scale is
in angular degrees and a 200 mm. tube is used,
this is|543 c.c. (or 5 c.c. with a 198.4 mm. tube).
1.5 c.c. of Wiley's acid mercuric nitrate solution (see
Appendix) is added, and the whole well mixed by

THE ANALYSIS OF MILK 31

violent shaking. The solution is poured on a dry
filter, and a polarimeter tube filled with the clear
filtrate.

As an example : the milk has a sp. gr. of 1.032, the

degrees of gravity are 32.0, and (a) is -^ — 1.60 c.c. ;

the fat is 3.60 and (b) is ^- = 2.00 c.c. ; if an instrument
1 .8

graduated in angular degrees and a 200 mm. tube are
used (c) is 5.43. The water added is 1.60-1-2.00+5.43=
9.03 c.c.

The reading is made by placing the tube in the
instrument (Fig. 21), focusing the eye-piece on the
half -shadow plate when the analyser is' so turned that
one side is darker than the other, and adjusting the
analyser till both sides are equal in intensity ; the scale
is then read by means of the vernier provided. Several
readings should be made, the adjustment to equality
being made from either side alternately, and the mean
of the readings taken as the correct reading. A blank
estimation, i.e. one with a tube filled with distilled
water, should always be made, and the reading if to
the right subtracted from, or if to the left added to, the
reading of the sample. The corrected reading of the
scale gives the percentage by weight of anhydrous milk
sugar.

Mercuric nitrate does not remove the proteins quite
completely ; for greater accuracy add to the filtrate
^o of its volume each of phospho-tungstic acid
solution and of dilute (i : i) sulphuric acid solution,
filter and polarise. Multiply the reading by i.i. The
error with whole milk is, however, very small and hardly
exceeds the experimental error of reading.

Gravimetric Estimation. — About ten grammes of milk
are placed in a 100 c.c. flask with 60 to 70 c.c. water,
5 c.c. of Fehling's copper sulphate solution added (see
Appendix), and the Solution neutralised with caustic
soda ; the liquid is made up to 100 c.c., and the contents
of the flask, after mixing, filtered through a dry filter ;

32 DAIRY ANALYSIS

50 c.c. of the filtrate are placed in a beaker, and a
mixture of 30 c.c. each of Fehling's copper sulphate and
alkaline tartrate solutions (see Appendix) added ; the
beaker is heated by a flame of such size that the liquid

FIG. 21. — Polariscope.

boils in about four minutes, and it is kept boiling for
exactly six minutes. A tube of hard glass, about i c.m.
in internal diameter and 10 c.m. long, with one end
drawn out, and plugged with a fairly tight wad of
asbestos, is ignited, cooled, and weighed ; the drawn-
out end is inserted in a hole in the cork of a vessel
from which the air can be exhausted (e.g. by a filter
pump), a small funnel is placed in the wider end, and
the liquid carefully poured off from the red precipitate
of cuprous oxide ; the precipitate is washed several
times by decantation with hot, well-boiled water, and is
then washed into the tube, and the last traces removed

THE ANALYSIS OF MILK

33

from the sides of the beaker by rubbing with a police-
man, and transferred to the tube ; the precipitate in
the tube is well washed with hot water, and finally
with alcohol, and dried. The narrow end of the tube is

FIG. 22. — Washing Precipitate.

connected with an apparatus from which hydrogen can
be evolved, and after the stream has passed for a few
minutes the part of the tube containing the precipitate
is gently heated by a small flame, till the cuprous oxide
is reduced to copper; the hydrogen is passed till the
tube is cool, and it is then disconnected and weighed ;
the increase in weight gives the quantity of copper,

c

34

DAIRY ANALYSIS

from which the quantity of milk sugar can be found by.
the table below ; this multiplied by 200, and divided
by the weight of milk taken, gives the percentage of
milk sugar.

TABLE IV

FOR CALCULATING WEIGHT OF MILK SUGAR FROM
COPPER REDUCED

(All weights are in milligrammes)

Copper

Milk Sugar

Copper

Milk Sugar " Copper

Milk Sugar

120

86.4

215

158.2 310

232.2

125

90.1

220

161.9 315

236.1,

130

93-8

225

165.7

320

240.0

135

97.6

230

169.4

325

243-9

140

101.3

235

I73-I

330

247.7

145

105.1

240

176.9

335

3SI.6

150

108.8

245

180.8

340

25S-7

155

112. 6

250

184.8

345

259.8

1 60

116.4

255

188.7

350

263.9

165

120.2

26O

192.5

355

268.0

170

123.9

265

196.4

360

272.1

175

127.8

270

200.3

365

276.2

1 80

I3I.6

275

204.3

370

280.5

185

135-4

280

208.3

375

284.8

190

139-3

285

212.3

380

289.1

195

H3-I

290

216.3

385

293.4

200

146.9

295

220.3

390

297.7

205

I50-7

300 224.4

395 302.0

2IO

154-5

305

228.3

400 306.3

Estimation of Proteins. — These may be estimated
together by Ritthausen's method, or the casein arid
albumin may be separated ; indirect estimations may
be made from the nitrogen by Kjeldahl's method, from
the "aldehyde figure/' or from the organic phosphorus
and sulphur.

The Ritthausen Method. — Pipette IQC.C. of milk into
a beaker, and add 100 c.c. of hot water ; add 5 c.c. of
Fehling's copper sulphate solution (see Appendix), and
neutralise with caustic soda solution ; collect the
precipitate either in a weighed Gooch crucible, or on

THE ANALYSIS OP MILK 35

tared filter-paper ; remove the precipitate completely
from the beaker by means of a policeman, and wash well
(Fig. 22). Dry in the water-oven, and extract the fat
with ether, preferably in a Soxhlet extractor, and dry
again till the weight is constant. Ignite the precipitate
in the Gooch crucible, or place the filter containing the
precipitate in a weighed basin and ignite it (if tared
filters are used the tare should also be ignited in a
weighed basin) ; subtract the weight of the ash
(corrected if necessary for the ash of the tare) from the
weight of the precipitate, and the difference will give
the weight of the proteins.

Estimation of Casein and Albumin. — Pipette
10 c.c. of milk into a beaker, add 90 c.c. of water at
43°-43° 0. and 1.5 c.c. of a 10 per cent, solution of
acetic acid ; stir well, and collect and weigh the
precipitate as above. [Note. — This estimation or that
given above may be combined with a fat estimation.]
The precipitate is in this case casein.

Raise the filtrate to boiling, and keep for 15 minutes
on the water-bath ; collect the precipitate as above,
and weigh after drying ; as fat and ash are absent the
extraction and ignition may be omitted. The precipi-
tate consists of albumin.

Estimation of Nitrogen by KjeldahPs Method.—
5 c.c., or 10 c.c., of milk are pipetted into a long-
necked hard glass flask ; 20 c.c. pure sulphuric acid
and a drop of mercury are added ; a long-stemmed
bulb is placed in the neck ; the flask is supported
in an inclined position, and it is heated by a small
flame ; at first water is driven off, next a consider-
able amount of frothing takes place, and when this
has subsided the flame may be turned up to such a
height that the sulphuric acid distils up to and is con-
densed in the neck; 10 grammes of acid potassium
sulphate may be added after the frothing has subsided,
but this addition is hardly worth while with milk, as
the operation is fast enough without it ; the heating is
continued till the liquid in the flask is quite colourless.

36 DAIRY ANALYSIS

After cooling, the acid liquid is diluted with about
100 c.c. of water; and poured into a flask of at least
1000 c.c. capacity (preferably of copper (Fig. 23)), and

FIG. 23. — Kjeldahl Apparatus.

the hard glass flask rinsed out with further quantities of
water ; the large flask is furnished with a cork carrying
a tube which is connected to a condenser, and a tube
allowing additions to be made to the .liquid. 25 c.c.,

vr

(50 c.c. if 10 c.c, of milk was taken), of — acid, or an
amount calculated to be slightly more than sufficient from

THE ANALYSIS OF MILK 37

the aldehyde figure (p. 38), are accurately measured
into a flask, which is placed so that the end of the
condenser dips into the liquid. Through the tube in the
cork 100 c.c. of a solution of caustic soda containing
300 grammes per litre are poured in, followed by 10 c.c.
of a 10 per cent, solution of sodium sulphide ; the tube
is closed, and the contents of the flask mixed by shaking ;
a flame is placed under the flask, and the ammonia
formed by the action of the sulphuric acid on the
proteins and liberated by the alkali, distilled over ; the
distillation takes about half an hour, a volume of ap-
proximately 200 c.c. being collected. A few drops of
cochineal are added to the distillate, and the excess of

acid titrated with -- alkali (see Appendix). A blank

experiment, i.e. one without the milk, should be per-
formed, and the difference between the volume of
alkali used in the blank and the experiment in cubic
centimetres multiplied by 0.0014 wm< giye the weight
of nitrogen ; this multiplied by 100 and divided by the
weight of the 5 c.c. taken will give the percentage of
nitrogen ; the nitrogen multiplied by 6.38 may be taken
as proteins in the milk.

Estimation of Casein and Albumin Nitrogen.—
To 10 c.c. of milk add 20 c.c. of a saturated solution
of magnesium sulphate, and crystals of the salt so long
as they are dissolved ; allow to stand for some time, and
filter off the precipitated casein, and wash this several
times with the saturated solution of magnesium sul-
phate (this is a slow process) ; place the filter and pre-
cipitate in a long-necked, hard glass flask, add 30 c.c.
of pure sulphuric acid and a drop of mercury, and pro-
ceed as above ; 150 c.c. of soda solution must be added
before distillation, and the distillate should be collected

, N • i
in 35 or 40 c.c. ot — acid.

The filtrate is diluted, and the albumin precipitated
by tannin ; the precipitate is collected on a filter, and
the nitrogen estimated as above.

38 DAIRY ANALYSIS

The casein nitrogen and albumin nitrogen may be
multiplied by 6.38 to give the amounts of casein and
albumin respectively ; the sum of the two is usually a
little below the total nitrogen.

Indirect Estimation from Organic Phosphorus
and Sulphur. — Estimate the phosphoric acid in the ash
of the milk (see p. 15), preferably using 25 grammes
of milk ; evaporate 25 c.c. of the filtrate obtained by
adding Wiley's mercuric nitrate to milk for the polari-
metric estimation of milk sugar (see p. 30), ignite and
estimate the phosphoric acid in the ash of this ; multiply
the weight of P205 by 4.42, and this will give the per-
centage of mineral phosphoric acid in the milk ; this
subtracted from the percentages of total phosphoric acid
will give the organic phosphoric acid, and the casein can
be calculated from this by multiplying by 50.8.

Take 25 c.c. of milk, add 10 c.c. of strong nitric acid
and i gramme of sodium carbonate, evaporate to dryness,
and add 2 or 3 c.c. more nitric acid, and again evaporate ;
ignite to a fairly white ash, and take up the residue'
with dilute hydrochloric acid ; evaporate to dryness,
and boil the residue again with dilute hydrochloric
acid, and filter. Just raise the filtrate to boiling, and
add barium chloride solution drop by drop so long as a
precipitate is produced. Allow the solution to stand
24 hours to complete the precipitation, the first two
hours preferably in the water-oven, and collect the
precipitate on a small filter, wash well with hot water,
and place filter and precipitate still wet in a weighed
platinum dish ; ignite over a small flame till the paper
is burnt, and then more strongly ; the weight of the
precipitate (corrected for the ash of the filter) multiplied
by 13.7 and divided by the weight of milk taken will
give the percentage of sulphur in the milk. For each
71 parts of organic P205, 32 parts of sulphur belong to
the casein ; the remainder of the sulphur multiplied by
58.5 will give the albumin.

Aldehyde Figure. — This determination may be
combined with an acidity estimation; to 10 or n ex.

THE ANALYSIS OF MILK

39

of milk at least I c.c. of 0.5 per cent, phenolphthalein

solution is added, and the milk

neutralised with • —
ii

(approximately) strontia solution ; to the faintly pink
liquid 2 c.c. or more of Schermg's 40 per cent, form-
aldehyde solution is added, and the titration continued
till the same degree of pink colour appears.. After
deducting the acidity of the formaldehyde solution,
the latter titration represents the aldehyde figure. The
aldehyde figure is obtained by multiplying the number
of c.c. used by the strength of the solution (see p. 95)
and by 1000, and dividing by the volume taken. Pro-
teins may be deduced from this figure by multiplying
by 0.170 ; this factor is only applicable f A

to fresh cow's milk when determined by
strontia solution.

Catalase. — For the estimation, the
measuring cylinder is filled with water
through the opening rf, the cover of which
is then screwed down. The opening b
(for cleaning the tube) is closed with a
rubber cork, and the chamber A is
charged, through the opening c, with 15
c.c. of the milk and 5 c.c. of 1 per cent,
hydrogen peroxide solution (or 9 c.c. of
milk and 3 c.c. of hydrogen peroxide).
The tube is now held at / and d and
shaken with a pendulum motion, and
the cover to c rapidly screwed down.
The tube is then placed in water at
25° C. up to the level of c, shaken from
time to time, and the volume of the
liberated gas which rises into the measur-
ing chamber B read off after two hours.

The Relation between Fat, Solids „ ,,

i « *f* ** »z A J?IG.24. — LiObecks

not Fat, and Specific Gravity.— As Cataiase Tube.

the solids not fat of milk are heavier than

water, and the fat is lighter, and as, moreover, the extent

to which each of these is heavier or lighter respectively

DAIRY ANALYSIS

is practically constant, it is evident that
by means of an approximate formula
any one of the three can be approxi-
mately calculated from the other two.
A simple formula which gives a very
good approximation is :

where S = Solids not Fat per cent, by

weight ;

G = degrees of gravity ; and

F = Fat per cent, by weight.

If it is desired to calculate directly

the Total Solids (T), which consists of

the sum of the fat and solids not fat,

3 we ma write

p

5 T = S + F = - + 1.2 F + 0.14

4

(2)

As the solids not fat are not generally
estimated directly, but are obtained by
subtracting the fat from the total solids,
the second formula is more useful when
the fat is to be calculated from the
specific gravity and total solids, and it
may be usefully converted to the form
F = 0.833! — 0.208 G — 0.12 . (3)
or perhaps more simply

i.2F = T-|-o.i4 . . (4)

Tables for the easy calculation of
solids not fat from fat and specific
gravity, and fat from total solids and
specific gravity are given at the end of
the book (pp. 89, 90) . As the method is
only approximate the figures are calcu-
lated only to the nearest 0.05 per cent.
To use these Tables, find in the upmost

THE ANALYSIS OF MILK 41

horizontal column the specific gravity, and in the ver-
tical column the fat or the total solids ; in the space
where the columns intersect the figure required is found.
If the last figure in the specific gravity is 9, o, or i, or
4, 5, or (). use the figure in the column corresponding

FIG. 26. — Using Milk Scale.

to the nearest o or 5 ; if it is 2 or 7, use the column
corresponding to o or 5, but add. an Table XII 0.05, and
subtract 0.05 in Table XIII ; if it is 3 or 8, use the
column corresponding to 5 or o, and subtract 0.05 in
Table XII and add 0.05 in Table XIII. Read directions
for use of each Table.

The calculation may also be made with the milk scale,
which consists of a slide rule (Figs. 25, 26) ; on one side
is marked total solids (i inch = I per cent.), on the
other the fat (1.2 inches = i per cent.), on the slide

42 DAIRY ANALYSIS

is marked specific gravity (^ inch = i degree), and an
arrow is placed 0.14 inch from the end of the scale.
If the arrow is placed against the fat, the specific
gravity lies against the total solids ; vice versa, if the
specific gravity is placed against the total solids the
arrow will point to the fat.

On another part of the rule is a scale for correcting
the specific gravity taken at any temperature to 60° F.
This is not shown in Fig. 25. On the rule is a scale
of degrees of gravity (marked lactometer degrees), and

r.

FIG. 27.— Collins' Milk Scale

on the slide a scale of temperature ; an arrow is placed
at 60° F. and this is placed against the degrees of
gravity found ; the temperature then corresponds to the
specific gravity corrected to 60° F. ; the readings from
the milk scale only deviate from those given by the
Table within the limits of reading a lactometer.

Collins has devised a milk scale (Fig. 27) by which the
percentage of solids not fat can be read direct. In this
it is only necessary to set the reading on the lactometer
opposite the temperature at which the specific gravity
was taken, when the percentage of solids not fat will
be found opposite the percentage of fat.

Though the calculation of the solids not fat or fat
can never be so exact as the direct estimation, it is
sufficient for many purposes, where small deviations do
not affect the conclusions drawn from the results ; this
method also provides a useful check on the analyses
where all three estimations are made, and it is hardly
ever found that the deviations of the calculated figures
from those estimated exceed 0.2 per cent.

CHAPTER TTT
THE ANALYSIS OF MILK-PRODUCTS

THE liquid milk-products are skim-milk, cream, whey,
butter-milk, sterilised milk, condensed milk, and sour or
fermented milk ; milk powder consists of milk evapo-
rated to dryness.

Skim-milk is treated exactly as milk ; as the fat
globules are very small and few, the estimation of fat
requires more care ; the period of revolution of the disc
in the Gerber method should be increased, and a cor-
rection of 0.05 per cent, should be added to the reading
unless a special tube is used. The gravimetric methods
of Storch and Ritthausen tend to give slightly low
results, and those of Werner- Schmid or Gottlieb are
preferable. In the estimation of the proteins by
Ritthausen's method, the extraction of the fat may be
omitted, and the percentage of fat found subtracted
from the results.

Cream requires several modifications. The specific
gravity, except of a thin cream, is difficult to estimate,
and this is usually omitted. It is advantageous to ad<T
an equal volume of alcohol to the cream before drying
for the total solid estimation, as there is then no skin to
be broken. The fat may be estimated by macerating
the total solids with ether or amyl alcohol, carefully
decanting and repeating the maceration, &c., about
half a dozen times ; the solids not fat are weighed
directly, and the fat found by difference. The ash
estimation is made on the solids not fat. The Werner-
Schmid method is, however, excellent for cream, with the
modification that 2 or 3 grammes should be weighed, into
the Stokes tube, and the weight made up to 10 grammes
with water. The Gottlieb method is also good ; i to 2
grammes should be weighed, and enough water added

43

44

DAIRY ANALYSIS

to make the total weight up to 5.15 grammes. The
methods are then carried out as for milk.

The fat mar be calculated from the total solids with
a close approach to accuracy by the formula

V — 1.104 T — 10.4
or by the following Table :

TABLE V

FOR CALCULATING PERCENTAGE OF FAT IN CREAM FROM
TOTAL SOLIDS

Total Solids

Fat

Solids not
Fat

Total Solids

Fat

Solids not
Fat

60

55.8

4.2

44

38.2

5.8

59

54-7

4-3

43

37-i

5-9

58 53-6

4.4

42

36.0

6.0

57

52.5'

4-5

4i

34-9

6.1

56

51-4

4.6

40

33-8

6.2

55 -

50-3

4-7

39

32.7

6.3

54

49.2

4.8

38

31.6

6.4

53

48.1

4.9

37

30-4

6.6

52

47.0

5.0

36

29-3

6.7

51

45-9

5-i

35

28.2

6.8

50

44.8

5-2

34

27.1

6.9

49

43-7

5-3

33

26.0

7.0

48

42.6

5-4

32

24.9

7-1

47

41-5

5-5

3i

23.8

7.2

46

40.4

5.6

30

22.7

7-3

45

39-3

5-7

29

21.6

7-4

This method is not available in the case of clotted or
Devonshire cream.

The aldehyde figure multiplied by 0.45 will approxi-
mate to the solids not fat in both fresh and clotted
creams.

The milk-sugar estimation' by the polariscope
requires modification, as the cream must be more
highly diluted ; it is best to weigh out 50 grammes of
cream, make up to 100 c.c., and add i c.c. of Wiley's
acid mercuric nitrate, and polarise.

ANALYSIS OF MILK-PRODUCTS 45

The milk sugar is found by the formula

,,.„ i ioo — 1.076 F X W
Milk sugar = R x X 0.95 X ^—

Where R = Reading in angular degrees with a

200 mm. tube.

F = percentage of fat by weight.
W = weight of cream taken.

The gravimetric estimation will require slight correc-
tion for the volume of the fat, and the formula

ioo — 1.076 F x W
Milk sugar = 2M X ^ may be used.

M = weight of milk sugar obtained from the Table on

1>- 34-

The protein estimation is carried out as for milk ;
it saves time, however, to dry the cream and to extract
the bulk of the fat before submitting the sample to
Kjeldahl's method, as fat is attacked but slowly by sul-
phuric acid and mercury.

Butter-milk is analysed in exactly the same way as
milk.

It sometimes happens that when churning, both salt
and water find their way into the butter-milk ; when
the butter-milk is to be sold, it is important to be able
to rapidly estimate both the proportion of water and of
salt.

Chlorides can be titrated in milk with — silver

nitrate solution, using potassium chromate as indicator,
but as milk itself contains chlorides a correction is
necessary for this. To 10 c.c. add a few drops of

potassium chromate solution and run in — silver

10

nitrate (see Appendix) till a faint red tinge is seen ;
from the quantity used subtract the aldehyde figure
(obtained with strontia) multiplied by 0.171; the
remainder multiplied by 0.0585 gives the sodium
chloride.

By multiplying the amount of salt fcund by 0.00735

46 DAIRY ANALYSIS

the increment of specific gravity due to the addition is
deduced, and subtracting this from the specific gravity
found, the specific gravity of the milk is obtained. From
this last figure and the fat the solids not fat can be
calculated, and from this the amount of added water
deduced by the formula on p. 52, or the formula which
is based on the above factors,

added water =

N

/ c.c. ^silver solution -aldehyde fig. x o.i 71 \

V 2.?. )

• x 100

36

may be used.

Whey is treated as milk; it contains, however, no
casein, but gives a small precipitate consisting of
albumoses, which by the methods given would be
estimated as casein. The aldehyde figure multiplied by
0.125 gives the percentage of proteins.

Sterilised milk can be analysed by the methods
given for milk ; the polarimetric estimation of milk
sugar tends to be low, owing to change in the milk
sugar on heating, and the gravimetric method should
be used. The albumin behaves like casein, as it is
rendered insoluble in dilute acetic acid and magnesium
sulphate solutions ; the estimation of casein and albu-
min can, however, be made by the indirect method from
organic phosphorus and sulphur. The total nitrogen is
unaffected. Ritthausen's method should not be used
for the estimation of fat in sterilised or condensed
milk.

Condensed milk, if unsweetened, may be analysed
by diluting one part by weight with two parts of water,
and boiling and treating in the same way as steri-
lised milk ; the results must, of course, be multiplied

by 3-

Sweetened condensed milk should be similarly
diluted and analysed. Great care must be taken to
well mix the contents of the tin, as the milk sugar

ANALYSIS OF MILK-PRODUCTS 47

separates in minute crystals, which on long standing
sink to the bottom. It is not generally heated to an
extent sufficient to affect the milk sugar, and milk and
cane sugar may be estimated by Harrison's method.

Harrison s Method. — Prepare the nitrate with acid
mercuric nitrate as usual (p. 30), taking, however, double
quantities ; place as much of the nitrate as possible
in a 100 c.c. flask and weigh this ; immerse for exactly
seven minutes in a briskly boiling water-bath to invert
the cane sugar, cool, and make up with distilled water
to the original weight. Fill the 200 c.c. tube with this
solution (cleared if necessary by nitration), polarise
and at once note the temperature. Multiply the dif-
ference between the direct and the inverted readings

by T7 — F' ai*d this will <nve the reading due to

142.66 -.1

cane sugar ; this divided by 1.2 will give the per-
centage of cane sugar in the diluted milk ; the per-
centage of anhydrous milk sugar in the diluted milk
is given by the difference between the direct reading
and that due to cane sugar. These percentages multi-
plied by 3 will give the amounts in the condensed
milk.

The Werner- Schmid method for the estimation of ^
fat should not be used, and the Gottlieb method is
recommended.

Sour milk is difficult to analyse, and the results
are generally less satisfactory than those obtained with
fresh milk. If approximate results only are wanted,
such as would be furnished by a determination of
specific gravity and fat alone, the following modification
of WeibulPs method may be used ; measure the sour
milk, and to each 100 c.c. add 5 c.c. of a solution of
ammonia (i part of ammonia, sp. gr. 0.880, to 4 parts
water) ; shake gently, and allow to stand till the
precipitated casein is all dissolved ; the specific gravity
is estimated by a lactometer, and a correction (usually
about 2.7 or 2.8 degrees), found experimentally by
noting the decrease of specific gravity in fresh milk

48 DAIRY ANALYSIS

treated similarly, is added ; the fat is estimated by the
Gerber method (or one of the gravimetric methods),
and the result is increased by one-twentieth ; this
method is available if the milk is not too old, and
serves excellently for control work.

An estimation of total solids may be made after
neutralising the acid with strontia solution ; an
estimation of the acidity is made as usual (p. 15), a
weighed quantity being used instead of a measured
amount, and a proportionate amount of strontia solu-
tion added to the weighed quantity of milk taken for
total solid estimation ; from the weight of total solids
0.00428 gramme should be deducted for each cubic

centimetre of — strontia added.
10

The ash is estimated as usual, but 0.00738 gramme
should be deducted from the weight of the ash for each

cubic centimetre of — strontia solution added.
10

The fat estimation is preferably made by the Store h
method (an addition of strontia solution being made as
in the total solid estimation) or the Gottlieb method ; the
Werner-Schmid method is also available, though it tends
to give high results with very sour samples owing to the
solubility of lactic acid in ether.

Other determinations are made as for milk, except
that the quantities taken are all weighed and not
measured. The total nitrogen is a useful datum.

The aldehyde method does not give exact results for
proteins.

The methods used in the Government laboratory
include the determination of alcohol, volatile acids, and
ammonia, and from these, the solids lost by the various
fermentations undergone by the milk are reconstructed.
The following description is condensed from Dr.
Thorpe's report :

Alcohol. — To 75 grammes of sour milk half the
caustic soda solution necessary to neutralise is added,
and the mixture is distilled : to the distillate is added

ANALYSIS OF MILK-PRODUCTS 49

N

}-5 c.c. -- soda solution, and this mixture again dis-
tilled ; the final distillate is made up to the original
bulk, and the specific gravity estimated. The difference
in degrees of gravity between the specific gravity and
1000 multiplied by 0.977 gives the percentage by
weight of milk sugar converted into alcohol.

Volatile Acid.— Ten grammes of milk are neu-
tralised to the extent of one-half, and a little
phenolphthalein added; the mixture is evaporated
to dryness on a water-bath with frequent stirring, and
after the addition of 20 c.c. boiling distilled water, —
soda solution is added till a pink colour just appears!
The difference between the number of c.c. of — soda
solution used in this experiment, and that required for
the original acidity of 10 grammes of milk, is multi-
plied by 0.0255 to give the percentage of milk sugar
converted into volatile acid.

Ammonia.— Two grammes of milk are diluted to
100 c.c. and filtered clear. Ten c.c. of the filtrate made
up to 50 c.c. with distilled water are compared in tint
with a solution of ammonium chloride solution (i c c
- o.oi milligramme (NH3) in 50 c.c. water containing
10 c.c. of a solution of 2 grammes fresh milk acidified in
100 c.c. after the addition of 2 c.c. of Nessler solution
(see Appendix) to each. The number of c.c. of ammonia
solution required to produce the same tint multiplied
by 0.026 gives the percentage of casein converted into
ammonia.

The three amounts are added together, and constitute
the total correction for solids lost by fermentation.

Milk Powder.— Moisture is estimated by drying i to 2
grammes in a basin to constant weight, and the ash is
estimated in the same portion.

The estimation of fat should be made by the Gottlieb
method, 0.6 to 0.7 gramme being weighed out and
water sufficient to make up to 5.15 grammes; after

D

50 DAIRY ANALYSIS

the addition of the alcohol, the solution may be warmed
if necessary to effect complete solution, and cooled before
the ether is added.

For the estimation of nitrogen by Kjeldahl's method
about i gramme should be taken.

For other estimations 10 grammes may be dissolved
in water, and made up to 100 c.c. after heating and
cooling.

CHAPTEE IV

THE APPLICATION OF ANALYSIS TO THE
SOLUTION OF PROBLEMS

The Detection of Adulteration. — The principal forms
of adulteration of milk are the addition of water and
the removal of cream.

The detection of water is based on the reasoning that
while the water natural to milk contains solids not fat,
added water is free from these. The amount of solids
not fat is nearly though not quite constant, and rarely
falls below 8.5 per cent, or rises much above 9.2 per
cent. ; numerous cases, however, are on record of solids
not fat below 8.5.

The removal of cream is detected by a deficiency in
the fat ; this varies much more than the solids not fat,
but comparatively rarely falls below 3.0 per cent.

The probability of samples falling below 8.5 per
cent, of solids not fat, and 3.0 per cent, of fat is indi-
cated by the following Table, which gives the number
of samples per 100,000 which may be expected at each
percentage named ; it is assumed that each sample
represents a churn of milk, i.e. that the milk is the
mixed product of several cows.

TABLE VI

Percentage of
Solids not Fat

Number of
Samples

Percentage of
Fat

Number of
Samples

8.4 to 8.5

1892

2.9 to 3.0

370

8.3 to 8.4

242

2.8 to 2.9

209

8.2 to 8.3

27

2.7 to 2.8

8?

8.1 to 8.2

22

2.6 to 2.7

37

8.0 to 8.1

8

2.5 to 2.6

16

Below 8.0

2

Below 2.5

13

52 DAIRY ANALYSIS

By Clause 4 of the Sale of Food and Drugs Act,
1899, ^ne President of the Board of Agriculture is
empowered to lay down limits below which a pre-
sumption is raised that milk is not genuine, and he
has fixed 8.5 per cent, of solids not fat and 3.0 per
cent, of fat. The effect of this is that the onus of
proving that milk taken under the Sale of Food and
Drugs Acts falling below these limits is genuine lies on
the vendor, and for most practical purposes milk below
these limits is taken as adulterated.

It is generally, though not invariably, found that, in
milk falling below 8.5 per cent, of solids not fat, the
deficiency lies chiefly on the milk sugar, and that the
proteins and ash are normal ; a percentage of total
nitrogen above 0.5 and a percentage of ash above 0.7
in a milk below 8.5 per cent, of solids not fat will
afford strong evidence that the milk is genuine, while
figures for total nitrogen and ash low proportionately
to the solids not fat will strengthen the conclusion
that the milk is watered.

There appears to be no chemical means of dis-
tinguishing between fat naturally low and fat lowered
by the abstraction of cream ; the most numerous
instances of fat below 3.0 per cent, naturally occurring
have been found in April, May, June, and July, and
they are especially rare in October, November, and
December.

The percentage of added water may be calculated
by the formula :

o £ _ a

Added water — -~ - X 100. (S = solids not fat.)

A formula which gives a nearer approach to the
probable amount is :

Added water = - - ^ — ' x 100.
36

(G = degrees of gravity. F = fat.)

APPLICATION OF ANALYSIS 53

The percentage of added water may be calculated
from the aldehyde figure (A) by the formula :

Added water = X 100.

20

The amount of cream abstracted may be calculated
by the formula :

Tf

Cream abstracted = x 100. (F — fat.)

3

This gives the minimum percentage of cream abstracted,
and the more probable amount is obtained by sub-
stituting the average percentage for the month as
given in chap. i. (p. 3) for 3 in both places.

Detection of Preservatives. Boric Add. — To a
little milk add a few drops of phenolphthalein, and
caustic soda solution drop by drop till a faint pink
colour is produced ; place some of the milk in two test-
tubes, dilute one with an equal volume of water, and
the other with a neutral 50 per cent, solution of
glycerine ; in the absence of boric acid the two tubes
will have almost the same colour, in its presence the
glycerine tube will be the lighter, and usually white.

As an alternative method the milk or its ash may be
made distinctly, but not strongly, acid with hydro-
chloric acid and a piece of turmeric paper dipped into
the solution ; on drying, the paper turns pink in the
presence of boric acid, and is turned a greenish black
by alkalies.

ESTIMATION OF BORIC ACID. — To 10 c.c. of milk
add at least 5 c.c. of phenolphthalein solution; raise to

the boil, and neutralise with — alkali while still boiling ;

the pink colour produced when neutral is faint, though
quite distinct. Add 8 to 10 c.c. of glycerine, and run in
the alkali till a pink colour appears, boiling at this

N
stage being unnecessary ; the quantity of — alkali used,

corrected for the acidity of the glycerine, multiplied

54 DAIRY ANALYSIS

by 0.062 gives the percentage of boric acid (calculated
as H3B03).

Formaldehyde. — -Dilute a little milk with an equal
bulk of water in a test-tube ; pour carefully down the
side of the tube a little 90 per cent, commercial
sulphuric acid ; a bluish colour is developed at the
junction of the acid and milk in the presence of
formaldehyde. This blue colour may also be observed
during the estimation of fat by the Gerber process

(P- 17)-

Salicylic and Benzoic Acids. — These acids give a violet
colour with ferric chloride, and are best tested for by ex-
tracting the nitrate produced by treating milk with
acid mercuric nitrate (p. 31) with ether, shaking the
ether with a little water to which a drop of phenol-
phthalein solution has been added, and dropping in
dilute caustic soda solution, till the water after shaking
just turns pink ; after discharging the pink colour
with very dilute acid and adding a little ferric chloride
solution, the presence of salicylic acid is shown by a
violet colour and of benzoic acid by a buff precipitate.

Hydrogen Peroxide. — Mix the sample with a little
fresh milk, and add a small amount of para-phenylene-
diamine or ortol ; a blue or red colour will be developed
if hydrogen peroxide be present.

Reaction of Milk with Hydrogen Peroxide.—
Fresh milk when treated with a little para-phenylene-
diamine or ortol (a photographic developer) and a
drop of hydrogen peroxide gives a deep blue (with the
diamine) or a brick-red (with ortol) coloration within
a few seconds. Milk heated above 80° C. remains white.

The Cause of Poor Milk.— The detection of added
water and of a deficiency of cream would be an obvious
explanation of the cause of milk being poor. If it is
normal in composition, but very white, and the fat
separated in the Gerber process is nearly free from
colour, this would show that the poverty of the
milk had been fallaciously inferred from its lack of
colour ; if this is not the case, the test given above

APPLICATION OF ANALYSIS 55

should be applied, and the soluble albumin estimated
(P- 35) ; a deficiency of albumin below 0.35 per cent.;
or the non-production of colour with para-phenylene-
diamine or ortol will show that the milk has been
heated, and as the cream rises very slowly on heated
milk, the milk has been called poor because cream is
not apparent in a short time. Occasionally a sample
called poor turns out to contain a high percentage of
fat ; this would show that the milk has been standing
long enough for the cream to separate and it is then
divided into a rich and a poor portion.

A not unusual practice is for the servants in a house-
hold to pour off a portion of milk from a can which has
stood some time for their own consumption, and remove
the cream, and to send the rest of the milk, thus
impoverished, for the consumption of the other members
of the household. (P*

The Cause of Sweet Milk. — Milk is sometimes
alleged to be sweet. Cane sugar may be detected by
adding to 10 c.c. of milk o.i gramme of resorcinol and
i c.c. of strong hydrochloric acid ; on standing in
boiling water for five minutes a red colour is produced
if cane sugar be present; it may be estimated! by
Harrison's method (p. 47). If all the figures for solids
not fat, ash, sugar, and proteins are equally high, the
milk has simply been concentrated, usually by boiling ;
the solids not fat have been found as high as 17.5 per
cent, in a case of this kind.

The Cause of High Colour.— If the colour is yellow
and the fat separated by the Gerber process is very
much darker than usual, and the cream separating is
much yellower than the skim-milk, the high colour is
natural.

If this is not the case artificial colours should be
tested for ; annatto is detected by making the milk
alkaline with sodium bicarbonate, immersing a strip
of filter-paper in it, and allowing to stand till next day ;
in the presence of annatto the strip is stained brownish.
Coal-tar dyes of the azo group give a pink colour when

56 DAIRY ANALYSIS

a mineral acid is added to milk, and this is usually seen
in the G-erber test. Other artificial colours are practically
never used.

A pink colour is generally due to blood ; to detect

FIG. 28. — High-speed Centrifuge.

this the milk isjwarmed to 50° C., and separated in a
high-speed centrifuge (Fig. 28) ; a bright red deposit
at the bottom of the tube may be taken as blood ; the
microscopic appearance of the corpuscles is given in
Fig. 29.

APPLICATION OF ANALYSIS 57

The Cause of Sour Milk. — Practically the only
cause of milk turning sour is the formation of lactic
acid by the action of micro-organisms. Milk curdles on
boiling when the acidity reaches about 33°, and spon-
taneously in the cold when the acidity is about 80° ;
milk curdled by boiling generally contains somewhat
hard lumps of curd, and the acidity of the whey may

*

& :',

>* f '**

fc ak

A: w

FIG. 29. — Blood in Milk

be 25° and upwards ; at lower temperatures the curd is
softer, and if the acidity is appreciably below 80°, this
indicates that the milk has been kept warm, but not
warm enough to inhibit microbial action.

Freshness of Milk. — The freshness of milk may
be determined by an acidity estimation ; if the acidity
is more than 2°' higher than the aldehyde figure, it may
be assumed thatr a development of acidity due to the
action of micro-organisms has taken place.

Many micro-organisms secrete a reductase, whioh
decolourises methylene blue ; make a solution by di-
luting i c.c. of saturated alcoholic solution of methylene
blue to 100 c.c. with distilled water, add i c.c. of this to
25 c.c. of milk contained in a stoppered tube of little

58 DAIRY ANALYSIS

more than 25 c.c. capacity, and keep for half an hour
at a temperature of 37° C. (blood heat) ; if the colour
disappears, the milk is not fresh.

Milk which is not fresh gives a high catalase figure,

. 30. — Using Microscope.

but this is not conclusive evidence, as high catalase
figures are obtained with fresh milk from cows with
diseased udders.

Custards made with eggs, especially if much sugar is
added, inevitably curdle if heated to too high a tem-
perature ; the liquids from such samples are usually high

APPLICATION OF ANALYSIS 59

in total solids (about 16 per cent.), have a low acidity,
and are nearly clear, characteristics which permit of the
cause of curdling being established.

Occasionally milk is alleged to be sour because it
turns blue litmus red ; all milk does this, as well as
turning red litmus blue, owing to the amphoteric
reaction of the phosphates and citrates of the milk.

The three popular superstitions that milk can be kept
warm, i.e. a little above blood heat for several hours
without change, that custards can be heated to any
temperature, and that blue litmus can be used as a test
for sour milk, though all fallacious, are responsible for
many allegations of sour milk. The peptonisation of
milk with powders which are insufficiently alkaline or
which have been kept too long may cause it to curdle,
and to be thought to be sour.

The Cause of Unusual Taste.— Milk on boiling
acquires a taste, and the tests for heated milk (p. 54) and
soluble albumin (p. 35) will show this. Mixture with
dirty water may give an evil taste to milk, and usually
the establishment of the presence of water is all that
can be done to explain this ; if an alkali is added to
milk, the taste is soapy and the smell fishy, and an
increase in ash and its strongly marked alkalinity will
detect the cause. If the taste is due to a fermentation^
other than the normal lactic one, or to the food of the
cattle, it is usually difficult to detect the cause by
chemical analysis.

An unpleasant taste may be due to the presence of
urine, accidentally or wilfully added.

Detection of Urine. — Half fill a small test -tube
(2 X f is large enough) with sodium hypobromite
solution (see Appendix) ; carefully fill the tube with
milk so that the two liquids do not mix. Place the
thumb over the tube, and invert once or twice, and
then hold it, with the thumb still over the opening,
upside down. Milk causes practically no pressure on
the thumb, and gives not more lhan one -fifth of its
volume of gas ; if urine has been added, much pressure

6o

DAIRY ANALYSIS

FIGS. 31, 32.— Vegetable .Matter in Milk.

APPLICATION OF ANALYSIS 61

is developed, and the liquid squirts out ; milk containing
i per cent, of urine yields about two -fifths the volume
of gas, while 5 per cent, causes an evolution of gas
equal in volume to the milk taken. Lobeck's catalase
tubes (p. 39) may be used.

The Cause of Dirty Milk.— Dirty milk almost in-
variably deposits a sediment on standing or centri-
fuging ; the milk is carefully decanted, the sediment
washed with water, and allowed to settle again and
examined under the microscope (Fig. 30). Sharply
defined vegetable ceils (Fig. 31), indicate that the finer
particles of the food given to the cattle probably at
milking time have fallen in ; less well defined vegetable
cells (Fig. 32), stained yellowish are probably derived
from faecal matter ; small hairs and various fibres
(cotton, wool, &c.) show the presence of household dust ;
transparent irregular particles which do not polarise are
quartz, and are due to road dust ; this latter also gives
a strong reaction for iron on treating the sediment with
hydrochloric acid, diluting, and testing with potassium
ferrocyanide which gives a blue colour with iron salts.

Control of Milk Prescriptions.— To control the
preparation of milk mixtures made up for infant feeding
from prescriptions, it is necessary to estimate rapidly
fat, proteins, milk sugar, and added sugar. The problem
is often simplified by all the materials used being
available for analysis, and by determining fat (by the
Gerber method), specific gravity, and aldehyde figure,
and calculating the solids not fat, in the samples and
in the milk from which the samples were made, the
four determinations required can be obtained with
sufficient accuracy for control purposes.

By estimating the ratio of solids not fat to aldehyde
figure in the milk used, and multiplying the aldehyde
figure of the mixture by this ratio, the amount of solids
not fat derived from the milk is obtained, and the
difference between the actual amount and this gives
the added sugar. With an unknown milk mixture
the ratio 0.45 may be assumed. The method does not,

62 DAIRY ANALYSIS

of course, distinguish between added cane sugar or added
milk sugar, but when it is known what the added
substance is, an estimation of sufficient accuracy is
obtained.

Detection of Adulteration of Cream.— As there
is no standard for cream, it may contain any per-
centage of fat, and still be cream ; there is a practical
standard of " thickness " which the purchaser mentally
estimates, and judges the value of the cream thereby.
Artificial thickening is sometimes resorted to, and
gelatinised starch, gelatine, " viscogen " (a solution of
lime in cane-sugar syrup), condensed milk or milk
powder, and collagens are added.

Starch is detected by the blue colour produced on
adding a solution of iodine in potassium iodide.

Gelatine is found, if present, by diluting the cream
with water and adding a little acid mercuric nitrate solu-
tion (see Appendix) ; the filtrate, if gelatine is present,
is usually turbid, and gives a precipitate on the addition
of a saturated solution of picric acid.

Viscogen raises the percentage of lime in the ash ;
the lime on an average amounts to 22 per cent, of the
ash, and its ratio to phosphoric acid (CaO to P205) is
i : 1.3. Viscogen raises not only the percentage in
the ash, but also the ratio to the solids not fat. A
small cane-sugar reaction may be obtained, and the
percentage of sugar polarised as milk sugar will exceed
52.5 per cent, of the solids not fat.

Condensed milk or milk powder may be detected by
the solids not fat being found in much greater propor-
tion than that given as corresponding to the fat found
in Table V ; the percentages of ash, milk sugar, and
proteins, and the aldehyde figure will bear the same
proportion to the solids not fat as found in milk. Clotted
or Devonshire cream, however, is concentrated during
its preparation, but its physical appearance differs from
that of raw cream, and it does not give the reactions
with hydrogen peroxide given on p. 54.

Collagens are difficult of detection ; they raise the

APPLICATION OF ANALYSIS 63

percentage of solids not fat, and give the same re-
action as cane sugar with resorcinol (p. 55), but by
Harrison's method no cane sugar is shown.

Preservatives are detected in the same way as for
milk. For the estimation of boric acid, the cream
should be diluted with an equal weight of water.

Adulteration of Skim-milk.— The President of
the Board of Agriculture has fixed 9.0 per cent, as the
limit for total solids in skim-milk. Percentages below
this are presumed to be caused by the addition of
water.

Rennet is sometimes added to skim-milk, and even to
whole milk, usually with the idea of causing curdling
when the milk is warmed. Its presence may be inferred
if the milk curdles on warming to 40° 0., and the
acidity is less than 25° ; the whey on neutralising to
an acidity of 12° will cause fresh milk to curdle at
40°, and the amount of lime in the whey does not
exceed 0.06 per cent.

Detection of Foreign Fats in Milk and Cream.—
By means of an emulsifying apparatus, foreign fats
(margarine fat, cocoa-nut oil) are mixed with separate
milk and the product sold as milk or cream. The casein
should be precipitated from a considerable amount of
milk (p. 35), dried, extracted with ether, and the fat-,
examined as butter fat (pp. 67 et seq.).

CHAPTER V
THE ANALYSIS OF BUTTER

Estimation of Water. — Weigh a small round basin
(Fig. 33) about 3 in. in diameter, containing a small
rod ; place 5 to 10 grammes of butter therein, and
weigh again ; heat the basin over a very small flame,
or on a sand-bath, and stir constantly till frothing
has ceased, cool, and weigh again. The loss of weight
indicates water, and this multiplied by 100 and divided
by the weight of butter taken gives the percentage.
The flame should be of such a size that the butter takes
at least a minute to become melted.

As an alternative method, about 2\ grammes of
butter may be weighed in a flat-bottomed basin, just
melted in the water-oven, and i| c.c. strong alcohol
mixed with the melted fat ; the basin is placed in the
water-oven for two hours, cooled, and weighed. The
loss of weight gives the water.

Estimation of Curd and Salt.— Wash the fat
from the basin after driving off the water by nearly
filling it with ether or amyl alcohol, and carefully
decanting the liquid after the solid portion has settled,
and repeating this four times ; if amyl alcohol is used,
it should be hot ; the residue is dried in the water-oven
for two hours and weighed after cooling. This repre-
sents curd and salt (if present).

Extract the salt from the curd with hot water, and
filter the solution ; wash the residue and the filter, and
cool the filtrate ; add a few drops of potassium ch re mate

solution, and titrate with — silver nitrate solution till a

faint red colour just appears ; each cubic centimetre
used is equal to 0,00585 gramme salt.

64

THE ANALYSIS OF BUTTER 65

Estimation of Casein. — Extract another portion of
curd with dilute ammonia till no lumps are left ; filter and
wash the residue ; add dilute acetic acid till a white preci-
pitate falls, and collect this in a weighed Gooch crucible

FIG. 33. — Water Estimation.

or on tared filter-papers, as on p. 35. Extraction and
ignition may be omitted. The precipitate is casein.

Tests for Preservatives. — Boric acid may be
detected by melting the butter at a low temperature,
and testing the aqueous portion with turmeric paper as
directed on p. 53.

E

66 DAIRY ANALYSIS

If found, the estimation is carried out by weighing
25 grammes of butter, adding 25 c.c. of water, melting
the butter at a low temperature, and stirring well ; the
aqueous portion is allowed to settle, and 20 c.c. are
withdrawn, and placed in a small beaker and boiled ;
at least 10 c.c. of phenolphthalein solution (see Appendix)
is added, and the solution titrated while still boiling with

N

- caustic soda solution (see Appendix) till a faint pink

colour occurs ; the reading of the burette is noted, 12 c.c.
glycerine are added, and the solution titrated again
(boiling is not necessary) till a pink colour appears ;
the difference between the reading of the burette and
the first reading, corrected for the acidity of the
glycerine, multiplied by 0.031, will give the weight
of boric acid (as H3B03), and this multiplied by
5 + 0.05 W (W = percentage of water) will give the
percentage of boric acid. Where the percentage of
water is not estimated the figure 5.65 may be used
for 5 + 0.05 W, and as an approximate figure the

N
number of cubic centimetres of — soda solution used

2

between the first and second titrations may be multiplied
by 0.17.

Sulphites are detected by the smell of sulphurous
acid given off on acidifying the aqueous portion ; formal-
dehyde will give its characteristic reaction (p. 54) if a little
of the aqueous portion is added to milk ; fluorides are
detected by adding a solution of calcium chloride to the
aqueous portion, filtering, igniting the precipitate, taking
up with dilute acetic acid, and treating the insoluble
portion with strong sulphuric acid in a platinum dish
over which is inverted a glass plate coated with bees-
wax through which one or two lines are scratched ; on
warming the sulphuric acid, hydrofluoric acid is given
off in the presence of fluorides, and this etches the
portions of the glass exposed by scratching through the
beeswax, and the marks are visible on melting and
wiping off the beeswax.

THE ANALYSIS OF BUTTER 67

The Examination of the Fat. — Butter fat is of
peculiar composition, consisting of complex glycerides
containing lower fatty acids, chiefly caproic and butyric
acids ; these are characterised by being soluble in
water, and volatile with steam, while the fatty acids of
almost all other fats are insoluble and non- volatile ;
furthermore the presence of the lower fatty acids in
the glycerides causes them to have a softer consistency
than if only the insoluble acids were present, and a
comparatively small amount of the acids of the oleic
and more unsaturated series is present. To obtain a
fat of the consistency of butter without the lower fatty
acids, a larger amount of acids of the oleic, &c., series
must be present. The presence of the lower fatty acids
gives a high specific gravity to the glycerides, and
causes them to crystallise badly.

In addition to these facts on which the broad prin-
ciples of butter analysis are based, certain vegetable
oils, especially sesame oil, give characteristic reactions,
and it has been recommended that by international
agreement all margarine shall legally be made to con-
tain 10 per cent, of sesame oil.

The addition of margarine to butter may be detected
by-

(a) A lowered proportion of volatile acids ;

(b) A lowered proportion of soluble and increased

proportion ot insoluble acids ;

(c) An increased mean molecular weight ;

(d) A decreased density ;

(e) A more marked crystallisation ;

properties all chiefly depending on the lowering of the
amount of caproic and butyric acids in the glycerides,
and —

( / ) An increased iodine absorption ;

(g) An increased refractive index ;
properties chiefly depending on the increase of the
unsaturated acids in the glycerides ; to those may be
added—

(h) A turbidity of the fat on melting at a low

68 DAIRY ANALYSIS

temperature, a property which depends on the
fact that mixing margarine with butter often
causes overworking, which gives rise to turbidity.

Owing to the natural variations of the composition
of butter fat, and to a less degree of the composition of
adulterants, the detection of small quantities of mar-
garine is difficult, and unless sesame oil can be found,
impossible in minimal amounts ; as only three principles
underlie all the methods, one of which has little value,
a multiplication of tests does not greatly assist.

Preparation of the Fat for Analysis.— Place 20
to 50 grammes of butter in a small beaker, and put
this in the water oven till melted ; observe the fatty
layer, whether clear or turbid ; pour as much as possible
of the fat into a dry filter, taking care that none of the
aqueous portion accompanies it, and filter in the water
oven, collecting the clear fat in a small beaker.

Estimation of the Volatile Fatty Acids. Reichert-
Wollny Process, Polenske's Modification. — Place a flask
of 300 c.c. capacity on one pan of a balance and tare
it ; add 4.5 grammes to the weights, and run in the
melted fat till the flask is weighed down, and place
a further 0.5 gramme weight on the other pan ; con-
tinue the addition of the fat cautiously, till the weight
is exact, if necessary removing a surplus with a small
pipette. It is not necessary to wait for the fat in the
flask to cool before making the final adjustment, as
the error involved in weighing warm fat is within the
limits of error of the final titration, nor is it necessary
to weigh more accurately than to 0.005 gramme.
Weigh in 20 grammes of glycerine.

Add 2 c.c. of a 50 per cent, solution of caustic soda
(see Appendix), preferably from a special measuring
apparatus (Fig. 34) ; heat the mixture over a naked
flame till the turbid liquid suddenly becomes clear ;
allow it to cool a little and add 100 c.c. of hot water
which has been previously boiled for at least fifteen
minutes, and when all the resulting soap is dissolved
0.1 gramme of powdered pumice which has been sifted

THE ANALYSIS OF BUTTER 69

through muslin and ignited, and 400.0. of sulphuric
acid solution (see Appendix) ; attach the flask by
means of a cork to a bulb tube attached to a condenser,
the dimensions of which are {riven in the sketch

FIG. 34. — Caustic Soda Apparatus.

(Fig. 35). Support the flask on a piece of asbestos card
in which is cut a hole 5 c.m. in diameter and heat with
a very small flame, till the fatty acids float in a clear
layer on the surface of the liquid ; then turn up the
flame to such a height that no c.c. distil in from eighteen
to twenty-two minutes. Collect no c.c.; turn out the

70 DAIRY ANALYSIS

flame, and replace the flask by a 25 c.c. cylinder ;
cool the flask for ten minutes in water at 10° C.,
mix the distillate, and filter through a dry filter ;
use the first few c.c. to wash out a 100 c.c. flask, and
collect exactly 100 c.c. of the filtrate, and transfer

this to a beaker, add a
little phenolphthalein and

N

titrate with — baryta,
10

strontia, or soda solution
till a pink colour appears ;
pour this back into the
flask, and again into the
beaker, and if the colour
is discharged continue the
titration. From the num-
ber of cubic centimetres
used, subtract the figure
obtained in a blank ex-
periment, and multiply the
result by i.i to obtain the
Reichert-Wollny figure.

Wash out the condenser
with two successive quan-
tities of 9 c.c. each of cold
, water, collecting this in the
'cylinder and using it to
wash out the flask, and
pouring it through the
filter ; reject this filtrate,
and remove the funnel containing the filtrate to a clean
flask. Wash out the insoluble fatty acids from the con-
denser with three successive quantities of 10 c.c. each
of neutral alcohol, collecting each in the cylinder, and
pouring it through the filter ; titrate the combined

filtrates with — alkali after adding a little phenol-
phthalein ; the number of c.c. of -- alkali used gives
the Polenske figure.

FIG. 3 5. — Polenske Apparatus.

THE ANALYSIS OF BUTTER 71

The Polenske figure varies with the Reichert-Wollny
figure, and the following Table shows the relation :

TABLE VII

Reichert-Wollny
Figure

Polenske Figure

Mean

Maximum

32

3-2

3-7

31

3-o

3-5

30

2.8

3-3

29

2.7

3-2

28

2.6

3-1

27

2.4

2.9

26

2.3

2.8

25

2.1

2.6

24

2.0

2.5

23

1.9

2.4

22

1.8

2.3

21

i-7

2.2

Estimation of Soluble and Insoluble Fatty
Acids and Mean Molecular Weight. — Weigh a
glass flask, which has been previously well boiled with
caustic alkali solution ; add about 4 grammes of butter

fat, and weigh again. Run in 50 c.c. — alcoholic soda

solution (see Appendix), attach the flask to an upright
condenser, and boil for a quarter of an hour ; add a
few drops of phenolphthalein solution and titrate with

- hydrochloric acid till the pink colour is discharged.
As the alcoholic soda solution alters in strength it must
be checked against the - hydrochloric acid, and the

value in terms of the acid solution obtained of 50 c.c. of

N
alcoholic soda ; from this subtract the volume of -

hydrochloric acid used in titrating after saponification,
and multiply by 2.805 and divide by the weight of
butter taken ; the figure obtained will be the percentage
of potash required for saponification.

72 DAIRY ANALYSIS

- Wash out the alcoholic solution into a large basin,
and evaporate the alcohol on the water-bath ; add
enough hot water to make the bulk up to 150 to 200 c.c.

N
and then add sufficient - hydrochloric acid solution to

make with the volume already used in the titration
i c.c. more than the quantity equal to the 50 c.c.
alcoholic soda added ; heat on the water-bath till the
insoluble fatty acids float on the surface in a clear
layer, and filter through a wet filter ; wash out the
basin with hot water till the fatty acids are transferred
to the filter, and wash them well on the filter, stirring
them up with the jet of water ; at least a litre of water
is required for washing. With a good filter the fatty
acids do not run through ; when washed, allow all the
water to run out, and wash the filter with hot alcohol,
collecting the filtrate in a weighed flask, till all the
fatty acids are removed ; evaporate the alcohol, and dry
in the water-oven till the weight is constant ; this will
give the insoluble fatty acids.

To estimate the soluble fatty acids, add a little
phenolphthalein solution to the filtrate from the
insoluble fatty acids, and titrate with alcoholic alkali
till a pink colour appears ; from the volume used cal-
culate the equivalent of -- acid, from this subtract the

i c.c. added in excess of the soda added, multiply by
4.4, and divide by the weight of butter taken ; this will
give the soluble fatty acids in terms of butyric acid.

Ave-Lallemant Method. — Four grammes of fat are
saponified and neutralised as directed above, and the
alcohol evaporated ; 20 c.c. of water are added, and
the saponified fat evaporated to dryness. About
350 c.c. of hot water are added, and the soap solution
transferred to a 500 c.c, flask, which is placed on a

N
water-bath. 100 c.c. - barium chloride solution are

added with constant shaking, and the flask is left for
fifteen minutes on the water-bath ; it is then cooled?

THE ANALYSIS OF BUTTER

73

and the solution made up to 500 c.c. and filtered;
200 c.c. of the filtrate is raised nearly to the boiling-
point, and dilute sulphuric acid added till no further
precipitate is obtained, the precipitate collected on a
filter, washed with water, alcohol, and ether, ignited
and weighed ; the difference between the weight and
that of the barium sulphate obtained frcm 40 c.c. of
the barium chloride solution, multiplied by 1643.5
and divided by the
weight of fat taken,
gives the insoluble
baryta value (b). The
saponification value is
calculated in terms of
barium oxide by mul-
tiplying the percen-
tage of potash re-
quired for saponifica-
tion (see above) by
13.68 (a), and the dif-
ference between a and
b will give the soluble
baryta value (c).

In genuine butters
the value of b — (200 + c) is always negative, and
varies from — 0.7 to — 23.8 ; cocoa-nut oil, margarine,
and other fats give positive values.

The soluble baryta value of butter usually lies between
50 and 65, but may be occasionally higher ; cocoa-nut
oil gives nearly the same figure, but the soluble baryta
value for other fats does not exceed 10.

Phytosteryl Acetate Method. — Fifty grammes of the
clear melted fat are shaken with 75 c.c. of warm 95 per
cent, alcohol ; the alcohol is cooled and decanted,
and a further quantity of 75 c.c. of alcohol is added,
and the process repeated.

The fat is saponified with i c.c. of 50 per cent, caustic
soda solution, and the bulk of the alcohol evaporated
in a basin ; 2 grammes of sodium bicarbonate and

FIG. 36.— Butter.

74 DAIRY ANALYSIS

2 or 3 grammes of kieselguhr are added, and the mass
evaporated to dryness, placed in an extraction thimble,
and extracted with petroleum ether in a Soxhlet.

Evaporate the solution, add 5 c.c. of — alcoholic soda

solution, and evaporate to dryness, adding a little
sodium bicarbonate before the solvent has completely
evaporated. Extract with petroleum ether, and evapo-
rate this, and take up with alcohol ; if the solution
is dark add a little animal charcoal and filter. Allow
the cholesterol or phytosterol to crystallise, and to
the crystals add 2 or 3 c.c. of acetic anhydride, and
evaporate on the water-bath. Crystallise the acetates
several times from alcohol and take the melting-point.
Cholesteryl acetate melts at Ii3.2°-ii4.6° (corr.) and
a higher melting-point shows presence of phytosteryl
acetate.

Estimation of Density. — Follow the directions on
p. 10, with the following modifications : weigh the
tube full of water at 37.8° C. (100 F.) instead of at
I5-5° C. ; dry the tube before filling it with the fat,
and take the density at 37.8° C. instead of at 15.5° C.

Examination under Polarised Light. — Place a
small portion of the butter (not butter fat) on a micro-
scope slide, and press down a cover-glass thereon ;
examine with a microscope furnished with a polari-
scope, using a i in. or \ in. power, focus with the Nicols
parallel, and then cross them, shielding the slide from
light except that which has passed through the
polariser. Genuine butter appears nearly uniformly
dark, while crystalline fats show a more or less well-
marked lighting in portions of the field.

Old butters, especially those which have been
submitted to vibrations, and butters prepared by
processes in which the cream is churned soon after
heating and cooling may show (Fig. 36) a somewhat
crystalline appearance, but generally this is due to
margarine (Fig. 37) ; this test though very rapid may
not be reliable.

THE ANALYSIS OF BUTTER

75

Estimation of Iodine Absorption.— Weigh about
0.4 to 0.5 gramme of fat in a stoppered bottle, dis-
solve in 10 c.c. of chloroform, and add 20 c.c. of
Wijs' iodine solution (see Appendix). At the same
time mix 10 c.c. of chloroform with 20 c.c. of iodine
solution, and place both bottles in a dark place for half
an hour. Add 15 c.c. of a 10 per cent, solution of potas-
sium iodide solution
to each, and about
200 c.c. of water, and

titrate with - sodium
10

thiosulphate solution
(see Appendix) till
the colour on shak-
ing is removed from
both aqueous and
chloroformic solu-
tions ; a little starch
solution may be
added when the colour
is very pale, and the
titration carried on
till all blue has disappeared, but its use is not absolutely
necessary.

The number of c.c. of thiosulphate multiplied by the
value of i c.c. in terms of iodine used in the blank
experiment gives the total amount of iodine added to
the fat ; the number of c.c. of thiosulphate similarly
multiplied used in the actual experiment gives the
weight of iodine not absorbed by the fat, and the
difference between these two gives the quantity
absorbed, and this multiplied by 100 and divided by
the weight of fat taken is the iodine absorption.

Determination of Refractive Index.— The Zeiss
butyro-refractometer is employed for the determina-
tion of the refractive index ; it consists of two water-
jacketed prisms, between which the substance is
placed, a mirror to reflect light through these, an eye-

FIG. 37. — Margarine

76

DAIRY ANALYSIS

piece with a scale in it by which the refractive index
is read off, and a thermometer for observing the tem-
perature. An apparatus for providing a stream of
water of constant temperature can be used, or in default

Fm. 38. — Rsfractometer.

of this a stream of water warmed to the required
degree can be run through the jacket by india-rubber
tubes from any fair-sized vessel ; though it is an advan-
tage to use water at a constant temperature, the cooling
of a large bulk of water is sufficiently slow to keep
the prisms at practically a constant temperature during
the reading,

THE ANALYSIS OF BUTTER

77

To make an observation, take the refractc meter
(Fig. 38), out of its case, stand it up, screw it in
the thermometer, and connect the india-rubber tubes
carrying the water to the inlet and outlet tubes of the

FIG. 39. — Ref ractometer

jacket. Turn the milled head, and open and throw
back on to its support the lower prism ; see that both
glass surfaces are clean (a cloth dipped in alcohol,
followed by a dry soft cloth is best for cleaning), and
place a drop of the melted fat in the centre of the
surface of the lower prism (Fig. 39), and close it.

78 DAIRY ANALYSIS

Arrange the mirror to reflect either daylight or the
light of a lamp through the prisms, and observe the
point on the scale where the dark shadow comes,
focusing the eye-piece if necessary ; make two or
three observations till the position of the shadow is
constant, and read the temperature at the same time.
The thermometer may be graduated either in centi-
grade degrees, or in the normal reading for butter fat
at the temperature of the water ; if of the former kind,
both readings are noted, and the refractometer readings
corrected to a standard temperature by multiplying
the difference between the observed temperature and
the standard temperature by 0.55, and adding or sub-
tracting the result, as the temperature is higher or
lower than the standard, to the refractometer reading.
If the thermometer is of the latter type, the observed
reading of the refractometer is subtracted from the
reading of the thermometer, and the result is expressed
in degrees less than the standard.

Table VIII gives the standard readings for each five
degrees centigrade.

TABLE VIII

Temperature

Scale Divisions

25
30

52.5
49.8

35

47.0

40

44.2

45

41.5

The average figure for butter is 46° at 35° C. or a
little below, and margarine gives about 54°. Genuine
butter sometimes gives a reading higher than 47°, and
the limits found are 43.5° to 49°.

A standard solution (normal flussigkeit) is supplied
with the instrument, and the scale should be adjusted
from time to time with this ; a point is marked on the

THE ANALYSIS OF BUTTER 79

scale where the standard solution should read, and a
key is provided for adjusting the scale to this.

Detection of Sesame Oil. — Add to 10 c.c. of the
melted butter o.i c.c. of a 2 per cent, alcoholic solution
of furfural, add I c.c. of strong hydrochloric acid, shake
well and add 10 c.c. of chloroform. A crimson colora-
tion of the aqueous layer indicates sesame oil. Some-
times coal-tar colours are added to the butter which
give a red colour with hydrochloric acid alone ; make
sure of the absence of these by testing a little of the
butter with hydrochloric acid. If these are present
use the fatty acids (p. 72) for the test.

If furfural is not available dissolve o.i gramme of
sugar in 5 c.c. of hydrochloric acid, and shake with

10 c.c. of melted fat. This will also give a crimson
colour with sesame oil.

Detection of Cocoa-nut OiJ. Hinks' Method. — Dis-
solve 5 c.c. of fat in 10 c.c.^of -ether, in a corked test-
tube, and pack this in ice ; after thirty minutes pour
the whole mass on a filter, and evaporate the filtrate ;
take up the fat with 3 to 4 c.c. of 96 to 97 per cent,
alcohol, boil when the fat should all dissolve, and cool
to 5° C. for fifteen minutes, and filter this ; cool the
filtrate to o° C. for two to three hours. Place a little
of the cooled solution on a well-cooled slide, and
examine rapidly with a | or f in. objective. Butter
crystallises in round globular masses, while cocoa-nut

011 gives characteristic feathery crystals, easily recog-
nised after a little practice ; other fats such as lard
give somewhat similar crystals.

The Application of Analysis to the Solution
of Problems. The Detection of Adulteration. — The Pre-
sident of the Board of Agriculture, under his powers
authorised by Clause 4 of the Sale of Food and Drugs
Act, 1899, has laid down the limit of 16 per cent, of
water in butter, and any quantity above this amount is
presumed to have been added. Occasionally water has
been worked into butter to add to its weight, but a
more frequent occurrence of excess of water occurs in

8o DAIRY ANALYSIS

milk-blended butter ; in the latter the " curd " will be
in the proportion of i part for each 10 parts of water,
in the former much less,

A washed butter may be distinguished from an un-
washed one by containing less than i part of curd to
10 parts of water, usually only about 0.5 part ; un-
washed butter contains about i part ; a larger percen-
tage of curd indicates that the butter was churned from
very sour cream, and will not keep well, or that it has been
adulterated with casein. A higher percentage of casein
than 0.5 indicates the presence of added casein ; this
form of adulteration is not uncommon. Cane sugar
or honey is occasionally added ; the test given on
p. 54 applied to the aqueous portion obtained on
melting out will detect this. The percentage of salt
should not exceed 3 in a mild salt butter, but may go
up to 5 per cent, or more in other samples. Irish
pickled butters are high in water and in salt.

The Preservatives Committee of the Local Govern-
ment Board recommended that no preservative except
boric acid be allowed in butter, and that only to
the extent of 0.5 per cent. ; this has not yet been
legalised.

The detection of margarine is more difficult ; the
Butter Regulations Committee of the Board of Agricul-
ture has recommended a limit for the Reichert-Wollny
figure of 24c.c., but their recommendation has not yet
been adopted.

This figure, as well as 89 as a superior limit for
insoluble fatty acids, 5 per cent, as the minimum for
soluble fatty acids, 22.0 per cent, for the potash re-
quired for saponification, 0.910 for the density, 42 per
cent, for the iodine absorption, and 48° as a maximum
Zeiss butyro-refractometer figure, may be taken as
indicating the border-line of genuine butters. Certain
butters, however, especially those prepared from the
milk of cows exposed to cold climates and near the
end of lactation, yield figures beyond these limits. The
appearance on melting, and under polarised light, may

THE ANALYSIS OF BUTTER 81

be useful as confirmatory, and a reaction for sesame
oil will establish the presence of margarine, while
vegetable oils give the phytosteryl acetate test.
The average figures for butter and margarine are :

TABLE IX

Butter

Margarine

Cocoa-nut

Reichert-Wollny figure

29 cc.

Practically none

7

Polenske figure

2-5

2.O

17

Insoluble fatty acids

87.5'%

95-5%

85

Soluble fatty acids .

6.0 %

None

?

Potash required

•?? *7 °/

-"*•/ /o

19-5%

26

Density

0.913

0.902

1

Iodine absorption .

37

55

9

Refractometer at 35°

46°

54°

43°

Cocoa-nut oil has a different composition from that
of margarine ; but as it lowers the Reichert-Wollny
figure, while at the same time raising the Polenske
figure and potash absorption, and lowering the insoluble
fatty acids, iodine absorption and the refractometer
figure, its detection is not difficult. Positive evidence
of its presence can be obtained by Hinks' method.

Application of Analysis to Buttermaking.—
The acidity of the cream should be taken to see if it
is properly ripened ; an acidity of 60° to 70° is usually
suitable.

The fat in the butter-milk is an important item, as
this represents loss ; 0.2 per cent, shows satisfactory
churning, while more than i per cent, even with very
thick cream indicates bad working ; either the ripening
has not been properly done, the churning is too rapid,
or the temperatures are wrong.

The amount of butter yielded by milk may be cal-
culated by subtracting o.i from the percentage of fat,
multiplying by 7, and dividing by 60 ; this gives the
number of pounds of butter per gallon of milk.

The following Table will give the amount of butter

F

82

DAIRY ANALYSIS

that may be expected from cream of any percentage of
fat :

TABLE X

Percentage of j
Fat in Cream 1

Quarts of Cream Churned

1

2

3

4

5

6

1

8

9

10

15

.44

.87

i-3

1.74

2.1

2.6

3-0

3-4

3-92

4-35

16

•47

•93

1.40

1.86

2-3

2.6

3-i

3-72

4.19

4.65

17

•5°

•99

1.49

1.98

2.48

2.9

3-4

3-97

4.46

4.96

18

•53

1.05

.58

2.IO

2.6

3.16

3-6

4.2

4-73

5.26

19

• 56

i. ii

.67

2.23

2.79

3-34

3-90

4.46

5.01

5-57

20

•59

1.17

.76

2-35

2.94

3-52

4.1

4.70

5.28

5.87

21

.62

1.23

.85

2.46

3.08

3-70

4-3

4-93

5-54

6.16

22

•65

1.29

•94

2.58

3.23

3-87

4-52

5.16

5.81

6.45

23

.68

i-35

2.03

2.70

3.38

4-05

4-73

5-40

6.08

6.75

24

•7°

1.41

2. II

2.82

3.52

4.22

4-93

5-63

6.34

7.04

25

•73

1.47

2. 2O

2-93

3.67

4.40

5-13

5.86

6.60

7-33

26

.76

1.52

2.29

3-05

3.81

4-57

5-33

6.10

6.86

7.62

27

•79

1.58

2-37

3-16

3.96

4-75

5-54

6-33

7.12

7.91

28

.82

1.64

2.46

3-28

4.10

4.91

5-73

6.55

7-37

8.19

29

•85

1.70

2.54

3-39

4.24

5-09

5-94

6.78

7-63

8.48

30

.88

i-75

2.63

3-51

4.38

5.26

6.14

7.02

7.89

8.77

31

.91

1.81

2.72

3-62

4-53

5-43

6.34

7.24

8.15

9-05

32

•93

1.87

2.80

3-74

4.67

5.60

6.54

7-47

8.41

9-34

33

.96

1.92

2.89

3-85

4.81

5-77

6.73

7.70

8.66

9.62

34

•99

1.98

2.97

3.96

4.96

5-95

6.94

7-93

8.92

9.91

35

1. 02

2.04

3.06

4.08

5.10

6.ii

7-I3

8.15

9.17

10.19

36

1.05

2.09

3.14

4.18

5-23

6.28

7-32

8-37

9.41

10.46

37

1.07

2.15

3.22

4-30

5-37

6.44

7-52

8.59

9.67

10.74

38

1. 10

2.20

3.30

4.40

5-51

6.61

7.71

8.81

9.91

Il.OI

39

I-I3

2.26

3-39

4-52

5-65

6.77

7.90

9-03

10.16

11.29

40

1.16

2.31

3-47

4.62

S-78

6.94

8.09

9-25

10.40

11.56

41

1.18

2-37

3-55

4-73

5.92

7.10

8.28

9.46

10.65

11.83

42

.21

2.42

3-63

4.84

6.05

7-25

8.46

9.67

10.88

12.09

43

.24

2.47

3-71

4.94

6.18

7.42

8.65

9.89

II. 12

12.36

44

.26

2.52

3-79

5-05

6.31

7-57

8.83

O.IO

1.36

12.62

45

.29

2.58

3.87

5.16

6-45

7-73

9.02

0.31

1.60

12.89

46

•32

2.63

3-95

5.26

6.58

7.89

9.21

0.52

1.84

I3-I5

47

•34

2.68

4.02

5.36

6.70

.04

9.38

0.72

2.C6

13.40

48

•36

•73

4.09

.46

6.82

.18

•55

0.91

2.28

3-64

49

•39

•77

4.16

•55

•94

•32

•7i

I.IO

2.48

3-87

50

.41

.82

4-23

.64

•05

.46

9.87

1.28

2.69

4.10

CHAPTER VI
THE ANALYSIS OF CHEESE

Estimation of Water, Ash, and Salt— Place 2 or
3 grammes of cheese cut into small pieces in a small
flat-bottomed basin, and keep in the water-oven for six
hours ; the drying proceeds better if the basin is
inclined so that the fat runs off the drying cheese ;
weight and return to the water-oven, and weigh
again at intervals of one hour till the loss is less
than one milligramme per hour ; the loss may be
taken as water.

Pour off as much fat as possible, and macerate the
residue in hot amyl alcohol ; pour off the amyl alcohol
as completely as possible, and ignite the residue as in
determining the ash of milk (p. 12) ; to determine the
salt make a determination of chlorine as on p. 14 ; each

cubic centimetre of — silver nitrate is equal to 0.00585

grammes salt.

Estimation of Fat. — Weigh about 2 grammes of
cheese, cut into small pieces, and transfer to a Stokes
tube, add 8 c.c. of water, and heat gently till the cheese
is softened and disintegrated ; then add 10 c.c. of
hydrochloric acid, and treat as in the Werner- Schmid
method (p. 29).

Estimation of Total Nitrogen.— Weigh about i
gramme of cheese and treat by the Kjeldahl method

(P- 35).
Estimation of Products of Ripening. — Weigh

10 grammes of cheese, place in a small mortar, and
add 25 c.c. of boiling water ; with a pestle grind up the
cheese and water, and pour off the solution through a
filter, collecting the filtrate in a 250 c.c. flask ; repeat
the treatment with 25 c.c. of boiling water till nine

83

84 DAIRY ANALYSIS

portions have been used ; cool the total filtrates, make
up to 250 c.c. and mix well. Evaporate 50 c.c. in a
weighed basin, and weigh the solids after drying till
the loss is less than i milligramme per hour ; ignite, and
weigh the ash ; the weight of the solids less that of the
ash represents the products of ripening. The difference
between 100, and the sum of the water, fat, ash, and
products of ripening, may be taken as unaltered para-
casein.

Ths products of ripening may be differentiated ; to
50 c.c. of the filtrate add 5 c.c. of copper sulphate, and
treat as in the Ritthausen method for the estimation of
proteins (p. 34) ; the proteins estimated in this way
may be termed primary products of ripening, and the
remainder secondary products.

Examination of the Fat. — Dry 25 to 50 grammes
of cheese till the fat runs out ; extract with ether,
and wash the ethereal solution with water in a
separating funnel ; remove the ethereal layer, and
drive off the ether, and dry the fat till the ether is
completely removed. Examine the fat as directed for
butter fat ; usually a Reichert-Wollny figure is
required.

The Application of Analysis to the Solution of
Problems. Detection of Adulteration. — Practically the
only adulterations of cheese consist in the removal of
fat from the milk before curdling, and the addition
of foreign matter.

The removal of fat may be judged if the fat is less
than 45 per cent, of the dried cheese, or if the fat is
less than six times the total nitrogen, both of which
standards lead to practically the same result ; a large
number of cheeses are made with half-skimmed milk
(e.g. the evening's milk is skimmed, and mixed with the
fresh morning's milk) ; these fail to comply with the
above standards, and should be sold as half-skim
cheeses ; other cheeses are made from skim-milk alone,
e.g. Dutch cheese (though cheeses are made in Holland
with whole milk also).

THE ANALYSIS OF CHEESE 8

Another method, particularly applicable to cream
cheese, is to deduce the composition of the cream
(or milk) used for the preparation of the sample, as
follows :

Divide the proteins by 0.3, which will give the
equivalent of solids not fat.

Divide the solids not fat thus calculated by 0.104,
which yields the equivalent of water in the original
cream (or milk).

The sum of the water, the solids not fat, and the fat,
represents the original cream, and the fat and solids
not fat are calculated as percentages. To allow for
loss, add on 0.25 per cent, to the percentage of the
fat thus deduced.

An example will make this point clearer. A cream
cheese contains 4.1 per cent, of proteins, and 49.5 per
cent, of fat.

4.1 -f 0.3 = 13.7 solids not fat.
I3-7 -r 0.104 = 132.7 water.

49.5 fat found.

Total .. 195.9

Percentage of solids not fat — 13.7 x =7.0

195-9

Percentage of fat = 49.5 X — . — = 25.3 + 0.25 = 25.5

_/«-' * ./

The quality of the cheese is then judged by the
quality of the milk or cream used for its preparation.

The detection of " margarine-cheese " is accomplished
by the examination of the fat ; practically the same
standards as for butter may be used ; it must be
remembered, however, that during the ripening the fat
is slightly attacked, and the percentage of volatile acids
may be somewhat lowered by this cause.

Preservatives need not be looked for in cheese.

Application of Analysis to Cheese-making.
Estimation of the curd by Lindens Method. — Estimate

86 DAIRY ANALYSIS

the fat and specific gravity as previously described ;
to 100 c.c. of milk add o.oi gramme of rennet powder,
and keep at 42° C. till curdled ; cut up the curd and
allow it to settle, and strain off the whey through muslin ;
cool the whey to 15.5° C. and estimate the specific
gravity and the fat as before.

Add the degrees of gravity and the percentage of
fat of the milk and subtract the sum of the degrees of
gravity and the percentage of fat of the whey ; the
difference divided by 3.5 will give the percentage of
dry curd available for cheese -making.

In practice the whey obtained during cheese-making
may bs tested instead of a separate preparation of whey
being made ; the sample for testing should, however,
be removed as early as possible.

The difference in acidity (see p. 15) between the
milk and the whey divided by 3.5 will also give a rough
estimation: of dry curd.

This will give an idea of the value of milk for cheese -
making. The percentage of dry curd plus the per-
centage of fat less 0.25 divided by 0.055 will giye the
number of pounds of cheese per 100 gallons of milk.*

A fermentation test is useful ; plug a number of
clean test-tubes with cotton-wool, and sterilise by
heating to 150° C. in an air-bath for* half an hour.
Place 10 c.c. of the milk to be examined in one of
these, and keep it at blood-heat for eighteen hours ; if
the precipitated curd is distended by bubbles of gas the
milk will not make good cheese.

The acidity of the milk before renneting should be
estimated (p. 15), and that of the whey after the curd
is cut, and the whey running from the curd at intervals.
As an example of the use of the acidity test, in Cheddar
cheese-making the best acidity of the milk for renneting
is 22°-24° ; the acidity of the whey is less than this,
but constantly increases ; the whey should be drawn

* The factor 0.055 w^ require modification according to the
kind of cheese made ; it applies fairly well to Cheddar and Cheshire
cheese.

THE ANALYSIS OF CHEESE 87

at about 22° acidity, and the curd vatted when the
whey draining off has an acidity of about 100°.

The acidity of the curd may also be judged by the
hot-iron test ; an iron is heated and allowed to cool till
it can just be touched with the finger ; the acidity of
the curd is judged by the length of the string which
is formed when the iron is pressed on the curd and
withdrawn.

The strength of rennet is determined by weighing out
0.5 gramme of a solid extract, or measuring 5 c.c. of a
liquid extract, and diluting to 100 c.c. i c.c. of the
solution is added to 100 c.c. of separated milk of
acidity 20° at a temperature of 35° C. ; the tempera-
ture is kept at 35°, and the milk slowly stirred with a
thermometer till it curdles, which is indicated by the
path of the thermometer becoming visible ; the time
which has elapsed since the addition of the rennet is
noted, and the strength of the rennet calculated as
parts of rennet which will cause curdling in forty
minutes by the following formulae :

800,000 £ ,. -,
Strength — — ^ — tor solid extracts,

80,000, ,. -T
or —7^ — lor liquid extracts,

where T — time in minutes.

The curdling should not take less than five minutes
nor more than ten minutes, and should this be the case
less or more of the rennet solution should be used, and
the results increased or decreased proportionately.

DAIRY ANALYSIS

TABLE XI

FOR CORRECTING SPECIFIC GRAVITY TO 60° F.
(see p. 8)

Temperature I
Degrees F.

Degrees of Specific Gravity observed

25

26

27

28

29

30

31

32

33

34

35

36

Specific Gravity corrected to 60° F.

40

23-5

24-5 25.5

26.4 27.3 • 28.2

29.1 1-30.0 ; 31.0

3i-9

32.8

33-7

42

23-6

24.6 25.6

26.5

27.5

28.4

29.3 ! 30.2

31. i I 32.0

32.9

33-9

44

23.8

24.8 25.8 26.7

27.7

28.6

29.5 : 30.4 31.3 ; 32.2

33-i

34-1

46

23.9

24.9

25.9

26.8

27.8

28.7

29.6 30.5

3J-4 32.4

33-3

34-3

48

24.0

25.0 26.0

26.9

27.9

28.8

29.7 ; 30.6

31.6

32.6

33-5

34-5

50

24.1

25.1

26.1

27.0

28.0

29.0

29.9 ; 30.9

31.8

32.8

33-7

34-7

52

24-3

25.2

26.2

27.2

28.1

29.1

30.1 31.1

32.0

33-0

33-9

34-9

54

24.5

25-4

26.4

27.4

28.4

29-3

30-3 31-3

32.3

33-3

34-2

35-i

56

24.6

25.6

26.6

27.6

28.6

29.6

30-5

3i-5

32.5

33-5

34-4

35-4

58

24.8

25.8

26.8

27.8

28.8

29.8

30.8

3r-7

32-7

33-7

34-7

35-7

60

25.0

26.0

27.0

28.0

29.0

30.0

31.0

32.0

33.0

34.0

35.0

36.0

62

25.2

26.2

27-3

28.3

29-3

30-3

3i-3

32.3

33-3

34-3

35-3

—

64

25.4

26.5

27.5

28.5

29-5

30-5

31-5

32.6

33-6

34-6

35-6

—

66

25.6

26.7

27.7

28.7

29.8

30.8

'3i.8

32-9

33-9

34-9

35-9

—

68

25.9 i 27.0

28.0

29.0

30.1

31-1

32.1

33-2

34-2

35-2

36.2

—

70

26.1

27.2

28.2

29.2

30-3

31-3

32-4 < 33-4

34-5

35-5

36.5

—

72

26.4

27.4

2-8.4

29-5

30.5

-31.6

32.6; 33.7

34-7 35-8

—

—

74

26.6

27.7

28.7

29.7

30.8

31-9

32.9 34.0 35.0 36.1

—

—

76

26.9

27.9 28.9

29.9

31.0

32.2

33-3 ! 34-4 35-4

36.5

—

—

78

27.2

28.2

29.2

30-3 3i-4

32.5

33-6|34.7 35-8

36.9

— ' —

80

27.4

28.4

29-5 30.6 j 31.7

32,8

33-9 ! 35-0 36.1

TABLES FOR CALCULATION

TABLE XII

FOR CALCULATING SOLIDS NOT FAT FROM FAT AND SPECIFIC
GRAVITY (see p. 40)

Correction

* Specific Gravity (Degrees)

— i.o

2CJ.O

2S.5

26.0

26.5

27.0

27-5

28.0

'28.5

*

29.0

29.5

30.0

30.5

31.0

31.5

32.0

32.5

+ 1.0

33-o

33-5

34-0

34-5

35-o

35-5

36.0

36.5

Fat

Solids not Fat

0.0

7.40

7.50

7.65

7-75

7.90

8.00

8.15

8.25

0.25

7-45

7-55

7.70

7.80

7-95

8.05

8.20

8.30

o-5

7-50

7.60

7-75

7.85

8.00

8.10

8.25

8-35

o-75

7-55

7.65

7.80

7.90

8.05

8.15

8.30

8.40

I.O

7.60

7.70

7.85

7-95

8.10

8.20

8.35

8.45

1.25

7.65

7-75

7.90

8.00

8.15

8.25

8.40

8.50

i-5

7.70

7.80

7-95

8.05

8.20

8.30

8.45

8-55

i-75

7-75

7.85

8.00

8.10

8.25

8.35

8.50

8.60

2.O

7.80

7.90

8.05

8.15

8.30

8.40

8.55

8.65

2.75

7.85

7-95

8.10

8.20

8.35

8.45

8.60

8.70

2-5

7.90

8.00

8.15

8.25

8.40

8.50

8.65

6.75

2-75

7-95

8.05

8.20

8.30

8.45

8.55

8.70

8.80

3-0

8.00

8.10

8.25

8.35

8.50

8.60

8.75

8.85

3-25

8.05

8.15

8.30

8.40

8-55

8.65

8.80

8.90

3-5

8.10

8.20

8.35

8'-45

8.60

8.70

8.85

8.95

3-75

8.15

8.25

8.40

8.50

8.65

8.75

8.90

9.00

4.0

8.20

8.30

8.45

8.55

8.70

8.80

8.95

9-05

4-25

8.25

835

8.50

8.60

8.75

8.85

9.00

9.10

4-5

8.30

8.40

8.55

8.65

8.80

8.90

9-05

9-i5

4-75

8.35

8.45

8.60

8.70

8.85

8.95

9.10

9.20

5.0

8.40

8.50

8.65

8.75

8.90

9.00

9.15

9-25

f Change at

O.2

O.I

0.2

O.I

0.2

O.I

0.2

O.I

* The solids not fat are correct for the middle line of specific gravity;
if the specific gravity falls in the top line subtract I from the solids
not fat ; thus 26.0 sp. gr. and 3.0% fat give 7.25% solids not fat ; if
the specific gravity falls in the bottom line, add I to the solids not
fat ; thus 34.0 sp. gr. and 3.0% fat give 9.25% solids not fat.

f The last line indicates where the change of solids not fat takes
place ; in a column with 0.2 at the bottom use the column itself for
the percentage of fat given, and 0.05, o. 10, and o. 1 5 above, but use the
figure immediately below for 0.2 above ; thus 30.0 sp. gr. and 3.1%
fat give 8.25% solids not fat, but 30.0 sp. gr. and 3.2% fat give 8.30%
solids not fat ; in a column with o. I at the bottom, use the column
itself for the percentage of fat given and 0.05 above, but change to
the figure immediately below for o:i or more above ; thus 30.5 sp.
gr. and 3.30% fat give 8.40% solids not fat, but 30.5 sp. gr. and
3.40% fat give 8.45% solids not fat*

DAIRY ANALYSIS

TABLE XIII

FOB CALCULATING FAT FROM TOTAL SOLIDS AND
SPECIFIC GRAVITY (see p. 40)

Specific Gravity Observed

A25.O

25.5

26.0

26.5

A27.O

27-5

28.0

28.5

B29.O

29-5

30.0

30.5

B3I.O

3i.5

32.0

32.5

C33-0

33-5

34-0

34-5

C35-o

35-5

36.0

36.5

Total

Total

Total

Solids A

Fat

Solids B

Fat

Solids C

7.00

0.50

0.40

0.30

0.20

8.0

O.IO

_

9.00

7-25

0.70

0.60

0.50

0.40

8.25

0.30

0.20

O.IO

—

9.25

7.50

0.90

0.80

0.70

0.60

8-5

0.50

0.4O

0.30

O.2O

9.50

7-75

•15

1.05

0.90

0.80

8.75

0.70

0.60

0.50

0.40

9-75

8.00

•35

1.25

1.15

1.05

9.00

0.90

0.80

0.70

0 60

10.00

8.25

•55

1-45

i-35

1.25

9-25

1. 15

1.05

0.90

0.80

10.25

8.50

•75

1.65

i-55

1-45

9-50

1-35

1.25

i.i5

1.05

10.50

8.75

•95

1.85

1-75

1.65

9-75

i-55

1.45

1-35

1.25

10.75

9.00

2.15

2.05

i-95

1.85

10.00

i-75

1.65

i.55

1.45

II.OO

9-25

2.40

2.30

2-15

2.05

10.25

1.95

1.85

i-75

1.65

11.25

9-50

2.60

2.50

2.40

2.30

10.50

2.15

2.O5

1.95

1.85

11.50

9-75

2.80

2.70

2.60

2.50

IO-75

2.40

2.30

2.15

2.01

ii-75

10.00

3.00

2.90

2.80

2.70

II.OO

2.60

2.50

2.40

2.30

12.00

10.25

3.20

3.10

3.00

2.90

11.25

2.80

2.70

2.60

2.50

12.25

10.50

3-40

3-30

3.20

3.10

11.50

3.00

2.90

2.80

2.70

12.50

10.75

3-65

3-55

3-40

3-30

11.75

3-20

3.10

3.00

2.90

12.75

II.OO

3-85

3-57

3-65

3-55

12.00

3-40

3.30

3.20

3.10

13.00

11.25

4-05

3-95

3-85

3-75

12.25

3.65

3.55

3-40

3-30

13.25

11.50

4-25

4-15

4-05

395

12.50

3.85

3-75

3-65

3-55

I3-5°

11.75

4-45

4-35

4-25

4-15

12-75

4.05

3-95

3-85

3-75

13-75

12.00

4-65

4-55

4-45

4-35

13.00

4.25

4-15

4-05

3-95

14.00

12.25

4.90

4.80

4-65

4-55

I3-25

4-45

4-35

4-25

4.15

14.25

J2.50

5.10

5.00

4.90

4.80 13.50

4-65

4-55

4-45

4-35

14.50

12.75

5-30

5.20

5.10

5.00

13-75

4.90

4.80

4.65

4-55

J4-75

13.00

5-50

5-40

5-30

5.20

14.00

5.10

5.00

4.90

4.80

15.00

If the total solids do not exactly agree with a figure in the Table
add the excess of total solids to the fat ; thus, given 30.5 sp. gr. and
n.8% total solids, add 0.05 to fat corresponding with 11.75% total
solids = 3.35% fat.

If the specific gravity lies in line marked A use the total
solids column marked A ; if in B use total solids column B ; if in C
use total solids column C.

APPENDIX
PREPARATION OF STANDARD SOLUTIONS

As the preparation of a standard solution is rarely, if
ever, undertaken while an analysis is being performed,
and as also it is tedious to wade through a description
of a method when seeking only for the quantities to be
weighed or measured for the solution, details of the
preparation have been removed from the text ; the
arrangement is alphabetical.

Alcoholic Soda Solution.— ^approximately. Add

25 c.c. of a 50 per cent, caustic soda solution (see
p. 93) to i litre of alcohol (sp. gr. 0.830) and mix well ;
allow the solution to stand a day, filter into a dry

N
stoppered bottle, and titrate (see Titration) against —

hydrochloric acid (see p. 92) to ascertain strength.
As this solution loses strength on keeping, it must be
titrated each time it is used.

Amyl Alcohol (for Gerber test) should conform to
the following : Density, 0.8145 to 0.816 at 15.5° C.
(Water at 15.5° C. = i.) Boiling-point : should not
begin to boil below 124° C. ; not more than 5 c.c. should
distil at 127.5° C. when 25 c.c. are boiled in a 100 c.c.
flask, and the boiling-point should not rise above
130.5° C. ; 10 c.c. should completely mix with 10 c.c.
of hydrochloric acid (sp. gr. 1.17) and the addition
of 1.5 c.c. of water should produce a permanent
turbidity. 2 c.c. treated in the Gerber bottle with
10 c.c. water and 10 c.c. sulphuric acid should yield no
layer of " fat."

Barium Chloride Solution, -.—24.45 grammes of

crystallised barium chloride are dissolved in I litre of
distilled water.

91

$2 DAIRY ANALYSIS

Baryta Solution. — Dissolve 33-35 grammes of
barium hydrate in 2 litres of water ; allow to settle, and
store in a bottle fitted with a soda lime tube to prevent
access of C02. Check the strength by titration (see p. 94).

Caustic Soda. See Soda.

Fehling's Solution. — Copper sulphate solution: Dis-
solve 34.639 grammes of crystallised copper sulphate
in water, and make up to 500 c.c. Alkaline tartrate
solution : Dissolve 173 grammes of pure sodium
potassium tartrate (Rochelle Salt), and 51 to 55 grammes
of sodium hydroxide of good quality in water, and make
up to 500 c.c.

Hydrochloric Acid -. — Dilute 50 c.c. strong hydro-
chloric acid to i litre ; ignite a quantity of pure sodium
bicarbonate at a dull red heat, and cool in a desic-
cator ; weigh (accurately to i milligramme) portions of
this, of about i gramme each, dissolve in water, add
a little methyl orange, and run in the hydrochloric acid
solution from a burette till the sodium carbonate solu-
tion turns pink ; the solution should be covered as much
jas possible with a watch-glass to prevent loss by spirting
as the C02 is given off. Wash the watch-glass into the
solution, and boil it, and continue the titration till the
pink colour is permanent on boiling. It is well to
place a beaker containing an equal bulk of distilled
water, and the same volume of methyl orange solution,
and one drop (0.05 c.c.) of hydrochloric acid, and titrate
till the sodium carbonate solution has the same colour,
and subtract 0.05 c.c. from the quantity of acid used.

If the solution is — , 20 c.c. should be required for

each 0.53 grammes of sodium carbonate ; if this quantity
is not used dilute in the proportion of the quantity used
to 20 c.c. , or use the solution as it is, and multiply by
20 divided by the quantity used to obtain its value in

terms of — acid. — solution is made from — solution
2 10 2

by diluting 200 c.c. to i litre.

APPENDIX 93

Iodine Solution (Wijs).— Dissolve 13 grammes of
iodine in i litre of 95 per cent, acetic acid (but made
by diluting 100 per cent, acid with 5 per cent, of dis-
tilled water) ; pass in a current of chlorine till the
litre of the solution has been doubled ; this point is
indicated by a change of colour.

Magnesia Mixture. — Mix 60 grammes magne-
sium chloride (MgCl260H2), 145 grammes ammonium
chloride, 600 c.c. water, and 300 c.c. ammonia solution
(sp. gr. 0.880).

Mercuric Nitrate Solution (Wiley). — Dissolve mer-
cury in twice its weight of nitric acid (sp. gr. 1.42),
and, after solution, add an equal bulk of water.

Nessler Solution. — Dissolve 35 grammes of potas-
sium iodide in 100 c.c. of water ; set aside a few c.c.
of this solution, and add to the remainder a saturated
solution of mercuric chloride till a permanent red pre-
cipitate is formed ; add the small portion set aside, and
cautiously drop in mercuric chloride solution, till a
faint permanent precipitate is left. Dissolve 160
grammes of potassium hydroxide in water ; cool the
solution, and add it to the potassium mercuric icdide
solution. Make up to I litre, add a little mercuric
chloride solution and allow to stand till clear.

Phenolphthalein Solution. — Dissolve 5 grammes
of phenolphthalein in 600 c.c. of alcohol and dilute
to i litre with water. Methylated spirit may be used,
and if necessary the solution should be heated with
animal charcoal, and filtered till clear.

Silver Nitrate, — . — Dissolve 17.000 grammes of

silver nitrate in i litre of water.

Soda Solution, 50 per cent. — Dissolve 250 grammes
of caustic soda (purified by alcohol) in 250 c.c. of water ;
allow to stand till clear, and store in the apparatus
described on p. 68.

For Kjeldahl Process. — Dissolve 300 grammes of
caustic soda in water and make up to i litre. After
standing a few days, filter through glass wool.

94 DAIRY ANALYSIS

N

•— . — Dilute 25 c.c. of the 50 per cent, solution to I litre.

Check the strength by titration (see below).

N

— . — Dilute 5 c.c. of the 50 per cent, solution to i litre.

Check the strength by titration.

Sodium Hypobromite Solution. — Add i c.c. of tbro-
mine to 10 c.c. of soda solution (for Kjeldahl process).

Strontia Solution. — Dissolve 28-30 grammes of
strontium hydrate in 2 litres of water. Treat as baryta
solution (p. 92).

Sulphuric Acid. For Gerber Process. — Should con-
tain 90-91 per cent. H2S04. Acid of specific gravity
1.820 to 1.825 fulfils this requirement.

For Reichert Process. — Dilute 25 c.c. strong sulphuric
acid to i litre of water ; 2 c.c. of 50 per cent, soda solu-
tion should neutralise about 35 c.c. of this solution ;
adjust the strength, if necessary, by adding acid or
water.

— . — Dilute 3 c.c. of strong sulphuric acid to i litre.
Check the strength as for hydrochloric acid (0.2
grammes only of the sodium carbonate is weighed for -

"\T ^ ^

acid, and 100 c.c. of : - acid should be required for

0.53 grammes sodium carbonate).

Thiosulphate Solution. — Dissolve 25 grammes of
pure sodium thiosulphate and i gramme of salicylic acid
in i litre of water. Allow to stand for a few days and
filter. Weigh accurately about 0.25 gramme of iodine
in a small stoppered flask, add 2 grammes potassium
iodide and 2 c.c. of water, and shake gently till the
iodine js dissolved. Dilute with water and transfer to a
larger Vessel, and run in the thiosulphate solution from
a burette till the yellow colour just disappears. Eepeat
this two or three times, and from the mean results cal-
culate the weight of iodine equivalent to i c.c.

Titration. — Take two burettes, fill one with the
alkaline solution, and the other with hydrochloric acid

APPENDIX 95

solution of corresponding strength. Measure 25 c.c. of
the acid solution, add a few drops of phenolphthalein
solution (or cochineal solution if this is used in the
experiment for which the alkali is to be employed), and
run in the alkali till a pink colour (violet with cochineal)
is produced. Note the volume of alkali used. Repeat
this experiment two or three times, and from the
mean of the results calculate the ratio of the alkali solu-
tion to the acid solution. Thus, if 24.2, 24.15, and

24.2 c.c. of — soda were used for 25 c.c. acid the ratio is

— — = 1.0^4 or i c.c. of soda = 1.034 c.c. acid.
24.17

N • N

If the acid is strictly : • the soda is :- X 1.034;

2 2

if the acid is, for instance, — X i.oii, the soda is then
* X 1.034 X i.on = f X 1.0454-

The soda may be diluted in the ratio of 1000 parts to
1045.4 parts, i.e. 45.40.0. of water are added to each
litre, but it is preferable to use the solution as it is, and
multiply the results by the factor.

To standardise — solutions( — strontia) 5 c.c. of the
— hydrochloric acid should be carefully measured, a

2

few drops of phenolphthalein solution added, and the
alkali run in till a faint pink colour is seen. Several
titrations should be made, and the mean taken. This
figure divided into 2.5 will give the strength of the
solution in terms of normal. Thus if 26.2, 26.3, and
26.25 c.c. were used in three experiments the mean is

2 ^

26.25, and the strength is -- = 0.09505 N.

INDEX

ABSORPTION, iodine, 7 5

potash, 71

Abstraction of fat, 5 1
Acidity, estimation of, I 5

of curd, 8 5

Acidobutyrometer, 18
Adulteration, detection of

in butter, 79

in cheese, 84

in cream, 62

in milk, 5 1

in skim-milk, 63
Albumin, i, 2

estimation of, 35, 37
Alcohol in sour milk, estimation
of, 48

amyl, 17, 91

Alcoholic soda solution, 91
Aldehyde figure, 38
Alkalinity of ash, estimation of,

13

Ammonia in sour milk, estima-
tion of, 49

Amyl alcohol (for Gerber test),

17, 9i

Annatto, detection of, 5 5
Ash, estimation of, in milk, 12,

*3

in cheese, 83
Ave-Lallemant method, 72

BABCOCK'S method of total solid

estimation, 12

Benzoic acid, detection of, 54
Blood in milk, detection of, 56
Boiled milk, test for, 54
Boric acid, in butter, 65

in milk, 5 3

estimation of, 53
Butter, analysis of, 64-82

composition of, 4, 81

Butter, detection of adulteration

of, 79 ^
examination by.polariscope,

-milk, 4, 45

-making, application of

analysis to, 8 1
preservatives in, 65, 80

CANE sugar, detection of, 55

estimation of, 47, 5 5
Casein, i, 2

estimation of, 35, 37

in butter, 65

Catalase, estimation of, 39
Cause of dirty milk, 61

high colour in milk, 5 5

poor milk, 54

sour milk, 57

sweet milk, 5 5

unusual taste in milk, 5 9
Caustic soda solution (see Soda)
Centrifuges, 18, 56
Cheese, 3

analysis of, 83-87

composition of, 4

-making, application of
analysis to, 85

products of ripening of, 83
Chlorine, estimation of, 13
Coal-tar dyes, detection of, 55
Cocoa-nut oil, detection of, 79
Colour, cause of, in milk, 55
Collagens, 63
Composition of butter, 4, 8 1

cocoa-nut oil, 79

fat, 67

margarine, 67

milk, 3, 4, 51

morning and evening milk, 3

products, 4

97 G

98

Condensed milk, 46

in cream, 62
Cream, 3

analysis of, 24, 43
calculation of fat in, 44
composition of, 4
detection of abstraction of,

52
detection of adulteration of,

62
Curd, 2, 3, 57

composition of, 4

estimation of, 8 5

in butter, 64

in cheese, 85

in milk, 85

Curdling, cause of, 57
Custard, cause of curdling in, 58

DENSITY of butter, 74

(see also Specific gravity)
Detection of adulteration of
butter, 79
cheese, 84
cream, 62
milk, 51

of preservatives in
butter, 65
cream, 63
milk, 53

Dirty milk, cause of, 61
Dyes, in milk, 5 5

EXAMINATION of fat in
butter, 67

under polarised light, 74
cheese, 84
cream, 63
milk, 63

FAT globules, i

gravimetric estimation of,

27-30

in butter, 67
in cheese, 83
in cream, 43
in sour milk, 47
preparation of, for analysis,

68

relation between specific
gravity, solids not fat,
and, 39

DAIRY ANALYSIS

Fat, standard for. 52

volumetric estimation of,

17-27

Fatty acids, soluble and in-
soluble, estimation of,

71

volatile, estimation of, 68
Fermentation test (cheese), 86
Fluorides, detection of, 66
Formaldehyde, detection of, 54
Freshness of milk, 57

GELATINE, detection of, 62

Gerber's method, for fat estima-
tion, 17-27, 43

Gottlieb's method, for fat esti-
mation,, 30, 43

Gravimetric estimation of speci-
fic gravity, 9

HARBISON'S method for the

estimation of cane sugar, 47
Heated milk, detection of, 54
High colour, cause of, in milk,

55
Hink's method for the detection

of cocoa-nut oil, 79
Hydrochloric acid, 92
Hydrogen peroxide, detection

of, 54

INSOLUBLE ash, estimation of,

12
fatty acids, estimation of,

68

Iodine absorption. 75
solution, 93

KJELDAHL'S method of estimat-
ing nitrogen, 35
Kieselguhr, 29

LACTIC acid, 2, 57

estimation of, 16
Lactometers, 6 et seq.
Leffmann and Beam's method

of fat estimation, 17
Lime, 2

detection of added, 63*

estimation of, 1 5
Lindet's method for curd, 85

INDEX

99

MACHINE-SKIMMED milk (see

Separated milk)
Magnesia mixture, 93
Margarine, composition of, 67
detection of, 67, 74, 8 1
-cheese, detection of, 85
Mean molecular weight of fatty

acids, 71

Measuring apparatus for milk, 1 8
Mercuric nitrate solution, 93
Micro-organisms, action of, on

milk, 2, 57

Microscope, use of, 58, 6 1
Milk, composition of, 3, 4, 51
measurement of, 19
mixtures, control of, 61
morning and evening, com-
position of, 3
powder, analysis of, 49

in cream, 62
scale, 40

sour, analysis of, 6, 47
standards for, 5 2
sugar, i

estimation of, 30-34, 44

NESSLER solution, 93
Nitrogen, estimation of, in milk,

35
estimation of, in cheese, 83

PAR A- CASEIN, 2

Phosphoric acid, estimation of,

13, 38

Phytosteryl acetate test, 73
Polarimetric estimation of milk

sugar, 30, 44
Polarised light, examination of

butter under, 74
Polenske's method of butter

analysis, 68

Poor milk, cause of, 54
Preparation of fat for analysis, 68

samples of milk, 5
Preservatives, detection of
in butter, 65
in cream, 63
in milk, 5 3
Products of ripening of cheese,

83
Proteins, 2

estimation of, 34-39, 45

REDUCTASE, 57
Refractive index of butter, 75
Rei chert - Wollny method for
estimation of volatile fatty
acids, 68
Rennet, 2, 3

detection of, 63
estimation of strength of,

86
Revis' method for total solid

estimation, 1 2
Ripening of cheese, products of,

83
Rise of specific gravity of milk

on standing, 1 1

Ritthausen's method for fat esti-
mation, 28, 34
method for proteins, 34

SALICYLIC acid, detection of,

54

Salt, estimation of, in butter-
milk, 45

in butter, 64

in cheese, 83
Separated milk, 3

adulteration of, 63

analysis of, 43

standard for, 62
Sesame oil, 79, 80
Silver nitrate, 93
Skim-milk (see Separated milk)
Skimming, detection of, 52
Soda solution, 93
Sodium thiosulphate solution

94

Solids, estimation of total, 1 1
not fat, estimation of, 39
relation between fat
and specific gravity,

39

standards for, 52
Soluble ash, estimation of, 12
fatty acids, estimation of,

71
Solution of problems, 5 1-63, 79-

81, 84-85
Sour milk, analysis of, 5, 47

cause of, 2, 57
Soxhlet extractor, 29
Specific gravity, correction foi
temperature, 41, 88

100

DAIRY ANALYSIS

Specific gravity, estimation by

lactometer, 6
gravimetric estimation, 9
of sour milk, 47
relation between fat, solids

not fat, and, 39
rise of, in milk, on standing,

ii

Sprengel tube, 10
Standards for butter, 8 1
milk, 52
skim-milk, 63
Starch, detection of, 62
Sterilised milk, 46
Stokes method for total solids

estimation, 12
tube, 30

Storch's method for fat estima-
tion, 28, 43
Strontia solution, 94
Sugar, cane, estimation of, 47, 5 5

milk (see Milk sugar)
Sulphur, estimation of, 38
Sweet milk, cause of, 5 5

TASTE, cause of unusual, in

milk, 59
Thermo-lactometer, 8

Thiosulphate solution, 94

Titration, 94

Total solids, estimation of, 1 1

by calculation, 39, 90
Total solids, in cream, 43

in sour milk, 48

UNUSUAL taste in milk, cause

of, 59
Urine, detection of, 59

VEGETABLE matter in milk, 60,

61

Viscogen, detection of, 62
Volatile acid in sour milk, 49
fatty acids, estimation of,

WATER in butter, estimation of,

64
cheese, 83

standard for, 79
milk, detection of, 5 1
Werner-Schmid, method of fat

estimation, 29, 47
Whey, 2, 46

ZEISS butyro-refractometer, 75

BALLANTYNE & COMPANY LTD

TAVTSTOCK STREET COVENT GARDEN

LONDON

BATED & TATLOCK (LONDON) LTD/S LIST OF

APPARATUS AND CHEMICALS REQUIRED

FOR MILK ANALYSIS, &c.

As mentioned in the " Laboratory Book of Dairy Analysis"
~by H. DROOP RICHMOND, F.I.C.

ALL the apparatus detailed below are required for a"Jfull
equipment ; the quantity will vary according to require-
ments :

THE ANALYSIS OF MILK
Sampling

Page Item
No.

5 i Sample bottles, oval shape, with corks, 5 oz.

6 2 Beakers, with spout, No. 5.
6 3 Brush, fine wire, for mixing.

Specific Gravity

6 4 Lactometer, ordinary pattern, paper scale.

7 5 Lactometer, Veith's pattern, 25-35.

7 6 Lactometer, Soxhlet's pattern, about 13 in. long.

7 7 Lactometer jar, zinc, 4 in. by i| in., with spout.

8 8 Thermo -lactometer, Que venue's.
10 9 Beaker flasks, 200 c.c.

10 10 Sprengel tube, 10 c.c.

Estimation of Total Solids

11 ii Platinum basin, flat, shallow, with spout, 2f in.
ii 12 Porcelain capsule, glazed all over.

Tantalum basin.

Silica basin.

ii 13 Pipette for milk, 5 c.c., with mark,
ii 14 Pipette to hold 5 grammes of milk.

11 15 Water -bath to take 6 porcelain capsules.

12 1 6 Desiccator, Scheibler's pattern, 6 in.

12 17 Balance, Bunge's 200 grammes, sensibility to T^th

mgm. on plate -glass sole.
12 1 8 Set of gilt weights for above, 50 to .001 grammes.

11 APPARATUS AND CHEMICALS REQUIRED

Page Item

NO. Estimation of Ash, &c.

12 19 Muffle furnace, No. 461.
12 20 Fireclay muffle for ditto.
12 21 Platinum wire, 6 in. long.

12 22 Tripod, triangular, 8 in. high.
12 23 Bunsen burner, \ in.

Argand burner.
12 24 India-rubber tubing for above, heavy walls.

12 25 Pipe-clay triangle, Clowes' improved form.

Triangle silica.

13 26 Filter-paper, C.S. and S. 589, black band.

15 27 Porcelain basin, round-bottomed, with spout, dia-

meter 3 1 in.

Estimation of Acidity

1 6 28 Acidimeter for testing acidity, consisting of special

burette, stand, and dropping bottle.

Estimation of Fat

17 29 Gerber's butyro meter for 4 samples, with acces-

sories as follows :

4 bottles ;

i pipette, 3 c.c. for cream ;

i ,, 10 c.c. 100 divs. for water ;

I ,, ii c.c. for milk ;

i „ 10 c.c. for acid ;

i „ i c.c. for amyl alcohol.

17 30 Leffman-Beam centrifugal machine, for 4 samples,
with accessories as follows :

4 bottles ;

i pipette, 3 c.c. ;

i „ 9 c.c.

i „ 15 c.c.

20 31 Richmond's shaking stand for 8 Gerber's tubes.
25 32 Pair of tared tin dishe.s, 2 in. by if in. for weighing
cream.

Gravimetric Estimation of Fat

29 34 Werner-Schmid tube.

28 35 Fat extraction thimble.

28 36 Glass mortar, 3 in. diameter, with pestle.

FOR DAIRY ANALYSIS iii

Page Item

No.

35 37 Funnel, 2 J in.

35 38 Filter-paper, C.S. and S 595, to suit.
35 39 Beakers, Xo. 3, with spout.
35 40 6 glass stirring rods, 6 in. long.
35 41 Conical flasks, 6 oz.

4ia Stoppered cylinders.

416 Wash-bottle tubes.

29 42 Soxhlet's Fat Extraction Apparatus as follows ;

i water -bath for 3 apparatus on stand ;
I set Bunsen's for ditto ;
3 fat extractors, 60 grammes ;
3 flasks with short necks, 4 oz. ;
3 condensers with india-rubber caps ;
i stand with three -armed clamp for supporting
condensers.

30 43 Stokes tube.

30 44 Burette, 100 c.c. T\yths, with stopcock.

Mahogany stand, for ditto.

Estimation of Milk Sugar

32 45 Mitscherlich's polariscope, with 100 and 200 mm.
tube and burner.

32 46 Hard glass tubes, 10 x i c.m., with one end drawn down.

31 47 Flasks, with mark 100 c.c., unstoppered.

33 48 Policemen, with india-rubber tops, for stirring.
33 49 Filter pump glass.

33 5° Glass tubing, assorted.

33 51 Wash- bottles, fitted with cork and tubes, I litre.

Estimation of Proteins

34 52 Gooch's porcelain crucible.

34 53 Asbestos fibre, for use with above.

Estimation of Casein and Albumin

35 54 Porcelain crucibles, No. I, with lids.

35 55 Crucible tongs, gun-metal, with platinum tips.

Estimation of Nitrogen

35 56 Kjeldahl's apparatus, with litre copper flask,

Lie big's condenser, &c.
35 57 Flask, 200 c.c., hard glass, round bottom.

iv APPARATUS AND CHEMICALS

Page Item
No.
37 58 Burette, fitted with soda lime tube, and bottle with

39 soda lime tube to hold strontia solution.

40 58a Richmond's improved milk slide rule.
42 58b Collins' milk scale.

Analysis of Liquid Milk-Products

47 59 Pipette, 5 c.c., short form with india-rubber tube at

top.

48 60 Flask, with side tube, 250 c.c.

48 61 Liebig's condenser, for use with ditto.
39 6ia Lobeck's catalase tubes.

49 62 Nessler tubes, marked at 50 c.c.

The Application of Analysis to the Solutions
of Problems

54 62a Separating funnel for salicylic and benzoic acid.

54 63 Test-tubes, 6 x | in.

56 64 High-speed centrifuge.

58 65 Microscope, with J in. and J- in. objective, one eyepiece

and substage condenser and polariscope fitted.
58 65a Test-tubes, 2 x J- in.

64-66 2 burettes, 50 c.c. ^

94
18

64
94
14

64

67 Stand, double, for ditto.

68 6 dropping bottles, with grooved stopper, 30 c.c.

95

THE ANALYSIS OF BUTTER

Estimation of Water, &c.

64 69 Sand-bath, 6 in.

64 70 I round tripod for ditto.

64 71 i Bunsen burner for ditto.

64 72 Porcelain basins, No. I.

64 73 Glass rod for ditto.

66 74 Glass plates, 2| x 2| in.

66 75 Set of pipettes, with mark 5, 10, 20, and 25 c.c.

CHEMICALS AND STANDARD SOLUTIONS v

NO. Estimation of the Volatile Fatty Acids

69 76 Caustic soda apparatus.

70 77 Polenske apparatus.

71 78 Flask, CO2, 6 oz.

71 79 Liebig's condenser for ditto.

71 80 Porcelain basin, 6 in. diameter.

74 8 1 Microscope slides, 3 x I in.

74 82 Microscope cover glasses, f in. square, No. 2.

75 83 Bottles, 4 oz. N.M., flat -stoppered.

Determination of Refractive Index

76 84 Zeiss' butyro-refractometer.

THE ANALYSIS OF CHEESE

83 85 Porcelain capsules, glazed all over.

84 86 Flask, 250 c.c. with mark, stoppered.

84 87 Separators, 500 c.c. cylindrical, with stopper and
stopcock.

86 88 Hot-air bath, 7x7 in., on stand.

86 89 Thermometer, engraved up to 110° C.

86 90 Incubator, B. and T.'s form, slag wool lined, with
capsule regulating at 37° C., complete with thermo-
meter.

86 91 Pair watch-glasses with binder.

86 92 100 c.c. flask with mark.

CHEMICALS AND STAND AED SOLUTIONS

THE quantities detailed below are necessary for a large
laboratory. They may be reduced in proportion when only
a small outfit is required :

5 Ib. acetic acid 100%.

i Ib. acetone.

4 oz. phenolphthalein indicator, 0.5%

I litre sulphuric acid —^ solution.

4 oz. potassium chromate indicator.

I litre silver nitrate ~ solution.

I w. qt. hydrochloric acid, pure.

vi CHEMICALS AND STANDARD SOLUTIONS

1 w. qt. ammonia, .880.

2 Ib. Schering's formalin.

\ Ib. ammonium oxalate, pure.

\ Ib. ammonium carbonate, pure.

\ Ib. magnesia mixture.

I litre caustic soda -^ solution.

i Ib. Kieselguhr special for filtering.

I w. qt. amylic alcohol ^for Leffmann-Beam or Gerber

i carboy sulphuric acid / process.

I Ib. soda lime.

i w. qt. alcohol.

I w. qt. petroleum ether.

5 Ib. caustic soda, pure.

i w. qt. sulphuric acid free N.

1 Ib. mercury redistilled.

2 Ib. potassium bisulphate.

I Ib. sodium sulphide pure reagent.
4 oz. cochineal indicator.

1 Ib. phosphotungstic acid.

2 Ib. magnesium sulphate, pure.

1 w. qt. nitric acid, pure.

2 Ib. sodium carbonate,
i Ib. barium chloride.

i w. qt. ether .720 meth.

i tube rennet tablets.

i Ib. beeswax.

I roll each blue and red litmus paper

and turmeric paper.
| Ib. ferric chloride,
i oz. para-phenylenediamine.
i oz. ortol.

1 oz. resorcine.

2 Ib. sodium bicarbonate.

\ Ib. potassium ferrocyanide, pure.
| Ib. iodine re -sublimed.

1 Ib. potassium iodide.

2 Ib. hydrogen peroxide, 20 vol.
2 oz. picric acid.

| oz. silver nitrate.

r Ib. calcium chloride, dry,

1 Ib. chloroform.

2 Ib. Rochelle salt.

for Kjeldahl's
process.

CHEMICALS AND STANDARD SOLUTIONS Vii

1 oz. furfural.

2 Ib. copper sulphate.

I Ib. mercuric chloride.
1 Ib. magnesium chloride.
5 Ib. caustic potash.
J Ib. strontium hydrate.
I Ib. sodium thiosulphate.

1 oz. salicylic acid.

J litre Nessler's reac$enti

2 Ib. glycerine.
J Ib. bromine.
| Ib. pumice.

BAIRD & TATLOCK

(LONDON) LTD

LABORATORY FURNISHERS, SCIENTIFIC

INSTRUMENT MAKERS, PURE CHEMICALS

AND REAGENTS &o.

WAEEHOUSE: 14 CROSS STREET, HATTON GARDEN
LONDON E.C.

FACTORY : HIGH AM LODGE, WALTHAMSTOW

12 6455

THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW

RENEWED BOOKS ARE SUBJECT TO IMMEDIATE
RECALL

LIBRARY, UNIVERSITY OF CALIFORNIA, DAVIS

Book Slip-25w-6,'66(G3855s4)458

N9 572824

SF253
Richmond, H.D. R52

The laboratory book of 1912
dairy analysis.

LIBRARY

UNIVERSITY OF CALIFORNIA
DAVIS