BB iy ory Tssued Uepriaty, 17, 1916.
| U. S, DEPARTMENT OF AGRICULTURE,
| SBUREAU OF ANIMAL INDUSTRY.

} A?

| CHEMICAL TESTING OF MILK
5 AND CREAM

BY

ROSCOE H. SHAW,

Chemist, Dairy Division. —

WASHINGTON:
GOVERNMENT PRINTING OFFICE,
1916.

6

“the Oe , Jerr. 20

Issued February 17, 1916.

U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ANIMAL INDUSTRY.

A. D. MELVIN, Chief.

P
4

CHEMICAL TESTING OF MILK AND
CREAM.’

By Roscok H. Suaw, Chemist, Dairy Division.

CONTENTS.
Page.

Chemical nature of milk - Bu Seon dobe: Sh Soe See ce ee tea 1
RUS HIM CMON tbe naire seach nek avek ee sda coda. oe! PERE: 3
Determination of total solids in milk _........... Soe eae ee 22
Determination of specific gravity of milk...........-.......---.-- 26
Calculating total solids by formula. -............-..-.------------ 28
Determination of acidity of milk and cream..................---. 32
The detection of preservatives...-........-22--2-22-2222202- eee 34
Chemicals and apparatus used in the chemical analysis of milk

BSH UCR VIA ia stra io oe ccteime o)s 2 <idiais = c/a msise ema senesis sateen se 36

ow

_ CHEMICAL NATURE OF MILK.

In order to follow intelligently the methods for testing
milk and cream some knowledge of the chemistry of milk
is essential. From a chemical standpoint milk is a very
complex substance. The component parts may, however,

1Tn preparing this.bulletin free use has been made of the various
publications on the subject, particularly ‘“‘Testing Milk and Its Pro-
ducts,” by Farrington, E. H., and Woll, F. W. (Madison, Wis., 1911),
and “Modern Methods of Testing Milk and Its Products,” by L. L.
Van Slyke (New York, 1907).

15037°—16—1

2

be classified into a few well-marked groups, as follows:
(1) Water, (2) fat, (3) nitrogenous constituents, (4) sugar,
and (5) ash. The components other than water are col-
lectively known as total solids or milk solids, and the
solids other than fat as solids not fat. Milk serum, or
more properly milk plasma, is the term used to denote
the milk minus the fat; hence the terms serum solids and
plasma solids are synonymous with solids not fat.
Water.—The water in milk varies from 82 to 90 per
cent. The usual variation in mixed-herd milk is much
less and is probably covered by 84 to 88 per cent.
Fat.—The fat in milk—milk fat or butter fat—is not in
solution but exists as an emulsion of microscopic globules —
so small that a single drop of average milk contains more
than one hundred millions of them. These globules, even
in milk from one cow, are not all of the same size. Some
may be two or three times the size of others, the average
size depending upon several factors, the principal one of
which is the breed of the animal. Chemically the fat is
not a single compound but a mixture of several compounds
known as glycerids. Some of these glycerids are common
to all fats, while others are peculiar to butter. This fact
is made use of in detecting oleomargarin or artificial
butter.
Cows’ milk meee contains from 3 to 6 per cent of fat,
depending very largely upon the breed of the animal.
Nitrogenous constituents.—These are principally casein
and albumin, with traces of less important nitrogenous
compounds. The coagulum produced by rennet, dilute
acids, or certain other chemicals, when added to milk, is
chiefly casein. Albumin is the flocculent precipitate
produced by heating whey or skimmed milk from which
the casein has been removed. In constitution and be-
havior it closely resembles white of egg. Casein is not
really in solution in the milk, but exists in an extremely _
fine colloidal condition in combination with some of the ©
ash constituents. With an appropriate filter of clay it
is possible to separate it from the water. Albumin is in
true solution in the water of the milk. Frequently, but
improperly, the term casein is applied to all the nitrogen-
ous constituents in milk. Sometimes the term total pro-
teins is used in referring to the nitrogenous constituents

3

taken asa whole. The amount of casein in average
cows’ milk varies from 2 to 4 per cent and the albumin
from 0.5 to 0.8 per cent.

- Sugar.—Milk sugar, or lactose, belongs to a group
known as carbohydrates, and is a white substance less
sweet in taste than cane sugar. Milk sugar is broken up
into lactic acid by the action of bacteria, this bringing
about the souring of milk. Milk sugar is in solution in
the water of the milk and is present to the extent of from
3.5 to 6 per cent.

Ash.—The ash, or the mineral part of milk, exists to
the amount of about 0.75 per cent and consists largely
of the chlorids and phosphates of sodium, potassium,
magnesium. and calcium.

AVERAGE CHEMICAL COMPOSITION.

The table below gives the average of more than 5,000
analyses of milk at the New York State Agricultural pas
iment Station, Geneva:

Per cent.

RRC EME yy On IENES DP Mo ve AP Ok 87.1
Moralisolidsweye tne stie re bem. wees crshoo Gane! yore 12.9
DMleo's f Seo 0 oe cle SS Oe, See ee eS eee 3.9
Cesetin . . 2 Saar ei een 2.5
sail PTOTEES UTD 5 1m, ogee eyamespuen dg emt pala lta alae did aii
LEIS « ot An eal te pel e eae ie Oa a a 5.1
Riemer enter aryiy 04 csogeatalls waid 8 oem wl 7

TESTING FOR FAT.

In the following remarks on the testing of milk and
cream the aim will be to present the subject in such a man-
ner that it may be followed by those who have had neither
chemical training nor a course of any sort in milk testing.
To those who have had such training the following pages
will doubtless appear coy elementary and overburdened
with detail.

TESTING MILK FOR FAT.

Preparing the sample for testing.—As before mentioned.
fat is not in solution in milk, but is in an emulsion of very
fine globules. These, being lighter than the surrounding
serum, tend to rise, carrying with them some of the other
solids, resulting in the familiar creaming of milk. Before

4

the test can be made a homogeneous mixture must be ob-
tained. This can best be obtained by pouring the milk
several times from one vessel into another. When the
sample is small, beakers are convenient for this purpose,
and if the sample has not remained in the container more
than a few hours, pouring back and forth four or five times
is sufficient. When, however, the sample has stood for
some time in the container, the cream layer is liable to be
hard and to adhere to the walls. Thisis particularly true of
preserved samples. In such event it is well to place the
container in warm water until the cream has become scft-
ened and can then be easily removed. Care must be taken
that none of the cream is left on the cover of the container;
if, however, any is left, a brush such as is used in cleaning
eveene | is ue in disigdeiee mts

The sample must always be well mixed immediately
before measuring out a charge for testing. If several
charges are to be measured out, the sample must be mixed
each time. Thorough mixing is imperative for accurate
work.

Partially churned milk.—Milk from some cows, notably
of the Jersey breed, churns very easily and sometimes a too
vigorous agitation in the mixing of such milk results in
some of the fat collecting in small granules which refuse to
emulsify again. This also frequently happens when the
milk is sent a long distance in partially filled containers.
These granules are easily recognized, and when they are
present special treatment is required to prepare the sample
for testing. A little ether equal in volume to 5 per cent
of the milk may be added, and the container stoppered and
vigorously shaken. The ether will dissolve the granules
and the solution will mix with the milk. A fairly accurate
charge may now be quickly removed, but the percentage
obtained must be corrected for the volume occupied by the
ether.

Another and perhaps a better way to treat churned milk
is to place the container in hot water until the milk has
attained a temperature of about 110° F. Ina few minutes
at this temperature the granules will have melted. The
container is then vigorously agitated and a charge for test
immediately measured out.

e

The partial churning of the sample is not a frequent
occurrence and with proper care can always be avoided.
When samples are to be sent a considerable distance the
containers should be completely filled so that no space is
leftatthe top. A good way is to fill a bottle to overflowing
with the mixed sample and then to insert a rubber or cork
stopper having a hole about one-eighth of an inch in diame-
ter. As thestopper goes to its place the milk will spurt out
through the hole; the hole is then filled with a piece of
glass rod or a wooden plug. When treated in such a man-
ner milk will not churn.

Sour milk.—While the souring of milk does not affect
the fat, it is impossible to obtain a representative charge
from curdled milk without special treatment. . In order to
obtain a good mixture it is necessary to dissolve the curd.
This may be accomplished by adding 5 or 10 per cent by
volume of a strong solution of either caustic soda or potash;
strong ammonia water may also be used. The alkali must
be thoroughly mixed with the milk until it is completely
liquid. The charge for test must be immediately meas-
ured out and a correction made in the final percentage for
_ the volume occupied by the alkali solution. If desired,
the powdered alkali may be added directly to the milk in
small portions at a time, being sure that one portion is
dissolved before another is added, and agitating until the
milk has become liquid. No correction is necessary for
the volume occupied by the powdered lye. When making
a fat test on milk containing alkali, special precautions
must be observed in adding the sulphuric acid, as an
excessive amount of heat is generated and the contents of
the test bottle may be thrown out. When alkali is used,
slightly more acid is required.

THE BABCOCK TEST.

The Babcock test for fat in dairy products, named for its
inventor, Dr. S. M. Babcock, chief chemist of the Wiscon-
sin agricultural experiment station, is based upon the
fact that strong sulphuric acid will dissolve the serum
solids in milk and set the fat free from its emulsion. In
conducting the test, the charge is placed in a specially
constructed test bottle and mixed with the proper quan-

6

tity of sulphuric acid. The acid performs other functions
than the simple solution of the serum solids. Much heat
is developed by its action, and this causes the fat globules
to lose their individuality and run together, a condition
which greatly facilitates the separation from the serum,
and this separation is still further accelerated by the
increase in specific gravity of the serum caused by the

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u Don @

A RINMIMeeie —_(\)

QUO MOU OOUOT CCGG COCO OCC O CU |

wo

Vn

Fic. 2—Type of Babcock
milk-test bottle conforming

F to the requirements of the

Fie. 1.—Old type of | United States Bureau of

- Babcock milk-test Standards, and showing
bottle. | graduations.

presence of the heavy sulphuric acid. When the solution
of the serum solids is effected the complete separation of
the fat and serum is accomplished by whirling in a centri-
fuge. The fat is gradually driven into the graduated neck
of the bottle and the percentage read directly.

Test bottles.—The Babcock-test bottle for milk, as shown
in figure 1, consists of a body holding about 50 cubic centi-

7

meters and the neck graduated so that the percentage of
fat may be read directly. Seventeen and one-half cubic
centimeters are used in the test, and this volume of average
- milk weighs almost exactly 18 grams. At the temperature
at which the bottles are standardized the specific gravity
of butter fat is about 0.9. Two cubic centimeters weigh
twice 0.9, or 1.8 grams, which is just one-

tenth of the weight of the charge used in

the test bottle. The volume between 0

and 10 per cent in the neck should, there-

fore, be 2 cubic centimeters, if the bottle

has been correctly standardized. Each

unit per cent is represented by a volume

of 0.2 cubic centimeters in the neck. The

old types of bottles were 10 per cent bot-

tles, the smallest subdivision being 0.2 per

cent. In the more recent types, notably

those made to conform to the specifica-

tions of the United States Bureau of Stand-

ards, the necks are somewhat smaller in gz
diameter and read only to 8 per cent, and

the smallest subdivision is 0.1 per cent.

(Fig. 2.)

Milk pipette —The charge for the Bab-
cock test for milk is measured rather than
weighed, the measuring instrument being
a pipette graduated to deliver 17.5 cubic
centimeters of milk. These pipettes, filled
to their graduation mark, hold 17.6 cubic :
centimeters. The extra 0.1 cubic centi- ser aenen es
meter is allowed for the milk which clings _ eypiec ° Conte:
to the walls. Pipettes may be obtained ~ meters, used
which conform to the requirements of | i= Measuring
the United States Bureau of Standards. a aie ohne
(Fig. 3.)

Acid measure.—This may be either a simple glass cylinder
graduated to deliver 17.5 cubic centimeters, or one of the
more complicated devices shown in figures 4,5, and 6. A
convenient little device is the small beaker with the glass
handle by which the proper quantity of acid may be

8

dipped out of a larger beaker and poured into the test
bottle. (See fig. 7.)

The centrifugal machine.—This is commonly called the
Babcock tester, and various types are on the market, —
ranging from the small, two-bottle hand tester to the large
steam turbine or electric tester, accommodating 24 or
more bottles. (See figs. 8,9, 10, and 11.) They all con-
sist mainly of a horizontal revolving disk or wheel provided
with swinging sockets to hold the bottles. At rest, these

Fie. 4.—Simple Fic. 5—Burette Fie. 6—A combined bottle
acid graduate. for measuring and acid measure.
the acid.

sockets allow the bottles to stand upright, but when in
motion, the centrifugal force causes the sockets to swing
outward, bringing the bottles to a horizontal position, with .
the necks toward the center. Where steam pressure is
available, a steam-turbine tester is strongly recommended
for the reason that it maintains a uniform motion under a
definite pressure and at the same time the steam keeps
the bottles warm and supplies the hot water required.
Whatever kind of tester is used, it must be firmly secured

9
-toarigid support. There must be no shaking or trembling
of the tester when in motion.

Acid.—The acid used in the Babcock test is the commer-
cial sulphuric acid, sometimes called oil of vitriol, and
should have a specific gravity of between 1.82 and 1.83.
It should be kept in glass bottles or jugs, preferably with
glass stoppers. Rubber stoppers will last for a time, but

Fia. 7.—A dipper made entirely of glass and holding 17.5 cubic centi-
meters for measuring acid in the Babcock test.

the use of cork stoppers is not permissible, as cork is rapidly
attacked by the acid. Owing to the property of sulphuric
acid of absorbing water from the air and thus diluting
itself, it can not be kept in open containers. :
Sulphuric acid is an extremely corrosive liquid, which
attacks the skin, the clothing, wood, and most of the com-

Fic. 8.—A 2bottle hand tester.

mon metals. Should the acid be spilled on the clothing,
it should be immediately washed off with plenty of water,
and ammonia water applied; this in turn must also be
washed off. Unless the acid is washed off immediately
after contact with the skin, severe burns will result. Acid
spilled on the table or floor may be neutralized with wash-
ing soda or other alkali. Lead is the only common metal
15037°—16—2

10

not attacked by this acid. If much testing is to be done,
it is a good plan to cover the testing table with sheet lead.

Testing strength of acid.—As already mentioned, the
specific gravity of the sulphuric acid used should be

between 1.82 and 1.83.

It is much better to pur-

chase it guaranteed of the
“ proper strength than to ~

bother with diluting the
stronger acid. Creamery
supply houses handle acid
guaranteed to be of the
proper strength, and if
kept in well-stoppered
Fig. 9.—A hand tester for 12bottles: Containers it will not
change. For the benefit
of those who prefer to test the acid themselves, the follow-
ing directions are given:

Use of the acid hydrometer—This is a hydrometer de-
signed only for liquids having a specific gravity about
that of concentrated sul-
phuric acid. (See fig. 12.)
It is standardized at 60°
F., and for correct results
must be used with acid at
that temperature only.
The acid at this tempera-
ture is poured into the
hydrometer cylinder and
the hydrometer allowed to
float in it. When it has
come to rest, the point on
the scale intercepting the
surface of the acid indi-
cates the specific gravity.
If it is much under 1.82
it can not be used for test-
ing milk, and should be discarded and a fresh lot of acid
obtained. Ifit is above 1.83 it may be diluted with water
untilit is of the proper strength. There are two ways of
doing this. The acid may be exposed to the air until it
absorbs sufficient water to lower its specific gravity; this is

Fig. 10.—A type of steam tester
with an arrangement for heating
the water used in the test.

11

the safest and best way if the specific gravity of the acid is
notmuchabovethestandard. Thesecond way is tomix the
acid with a small quantity of water. A small quantity of
water is placed in a bottle or jar and the acid poured into
it. Never pour water into acid, as a serious accident may
result. . After the mixture has cooled to 60° F. it is again
tested with the hydrometer and the process repeated if
necessary.

DIRECTIONS FOR MAKING THE BABCOCK TEST WITH
MILK.

Measuring the charge.—Directions have already been
given for preparing the sample for the test. The milk is
poured from one beaker to another two or three times.
The tip of the pipette is
immediately inserted and
the milk sucked up with
the mouth until it reaches
a point well above the
graduation mark on the
stem; the dry forefinger is
then quickly placed over
the mouth of the pipette.
By slightly relaxing the
pressure of the finger the
milk is allowed to flow
down until it just reaches Fig. 11.—A type of electric tester.
the mark. The tip of
the pipette is now placed in the neck of the test
bottle and the milk allowed to flow slowly down the
side. The right way is to hold the pipette obliquely
to the mouth of the test bottle as shown in figure 13.
The wrong way is shown in figure 14. If the bottle and
pipette are held in the latter position the neck of the bottle
may clog up and some of the milk run over the top.
Care must be taken that none of the milk is lost
during the operation. When nearly all the milk has run
out of the pipette, the last drop is forced out with a puff of
the breath.

Adding the acid.—The temperature of the milk when the
acid is added should be between 60° and 70° F., and the
acid should be at about the same temperature. Seven-

12

teen and one-half cubic centimeters of the acid are meas-
ured out, and, with the bottle held at an angle, carefully
poured down the side, the bottle being turned slowly at
the same time so that any milk adhering to the neck will
be washed down. For two reasons the acid must not be
poured into the middle of the test bottle; first, because it
may form a plug in the neck, which may be driven out by
the expansion of the air below; and second, because the ~

Fig. 12.—H y -
drometer and Fig. 13.—Theright way of add-
cylinder used ing milk to the test bottle.
in testing sul- (Farrington and Woll, Testing
phuric acid. Milk and Its Products.)

acid may partially mix with the milk and produce black
particles which do not dissolve and later interfere with
the reading of the test. The acid and milk should now
be in two distinct layers without much of a dark layer
between them.

Mixing the acid and the milk.—The acid is now mixed
with the milk by giving a combined rotary motion and
gentle shaking with the hand grasping the neck of the

13

‘bottle. When once commenced the mixing must not be
interrupted until the solution iscomplete. The first effect
ofthe acid on the milk isa curdling, which is subsequently
dissolved. As the solution progresses the color changes
first to a light yellow, then to dark yellow, then through
various shades of violet to brown and finally to dark brown,
if the acid is of the proper strength and the milk and acid
are at the right temperature
when united. Too strong or
too warm acid produces a
dense black. If the milk has
been preserved with formalde-
hyde, a longer time is re-
quired to complete the solu-
tion, owing to the toughening
of the casein by that preser-
vative. Common errors of
beginners are failure to mix
the acid thoroughly with the
’ milk and to continue the shak-
ing until the solution is com-
plete. A good planis to shake
the bottle for a minute or
so after the solution is appar-
ently complete. Although
not necessary, it is preferable
to centrifuge the bottles im
mediately, though they may
be kept 24 hours if desired,
in which case they must be
placed in water from 170° to Fig. 14.—The wrong way of

180° F. for 15 to 20 minutes - adding the milk to the
Bier milk bottle. (Farrington

before whirling. and Woll, Testing Milk

Centrifuging the bottles —The and Its Products.)

bottles are now placed in

the sockets of the centrifuge, taking care that they are
equally distributed about the wheel or disk so that the
equilibrium of the latter is not disturbed. An even num-
ber of bottles should always be whirled. Should an odd
number of tests be made a test bottle filled with water may
be used to balance the machine. When the bottles are in
place, the tester is covered in order to keep the bottles

14

from getting cold and to protect the operator from flying
glass and acid should any of the bottles break. The tester
is now set in motion and the bottles whirled 4 to 5 minutes
at the proper speed. This will be sufficient to bring prac-
tically all the fat to the surface. In cold weather, if a
hand tester is used, it may be necessary to pour hot water
into the jacket of the tester to keep the bottles warm.
Speed of centrifuge—Farrington and Woll have calcu-

lated the proper speed of testers with wheels of different —

diameters to be as follows:

Revolutions
of wheel

Diameter of wheel in inches: ' per minute.
108 oe on eee 1, 074
12. een. =. Se PEs 2 ee er 980
14 RS ee Be ee 909
16 n2 les Sa ol ee 848
US eee se Ges cack sk. 2. See ee .2 ee 800
202. ee ete ch. es ee 759
QO oe eae OR. Se 724
QA Se Se oR deisb 2 oh eee eee 693

Adding the water.—With the pipette or with the device ©

for the purpose attached to some steam testers, or in any
other convenient manner, hot water is added to the bottles
until the contents come nearly to the lower part of the
neck. The cover is now replaced on the tester and the
whirling repeated for one minute. Hot water is again

added until the fat reaches a point below the highest

graduation mark on the neck. It must never reach the top

mark, or some of the fat may be lost. This time the water

should be dropped directly into the fat in order to clear

the fat of the light, flocculent material which may be

entangled in it and which would later interfere with the
reading of the test. The whirling is repeated for another

minute. The temperature at which the readings are
~ taken is between 130° and 140° F., and this should be
borne in mind when the water is added, the object being to
add the water at such a temperature that the temperature
of the fat at the close of the last whirling will be between
these two figures.

The water used should preferably be soft water or con-
densed steam. The use of hard water is liable to cause
trouble on account of its carbonates; these are decomposed
by the acid, liberating carbon dioxid, which may cause

SS

a.

of dividers is useful in making this read-

15

‘foam on the top of the fat column and obscure the menis-

cus. If soft water or condensed steam is not available,
hard water may be used if, before heating it, a few drops of
sulphuric acid are added.

Reading the percentage.—Ii the test has been successfully
conducted, the fat will be in a clear, yellowish liquid
column sharply separated from the clear and nearly color-
less acid solution immediately below it and with no foam
on top. The bottles should be kept warm either in the.
tester or in warm water until read, and the
readings should always be made at be-
tween 130° and 140° F. The fat at this
temperature will, if other conditions have
been correct, have a well-defined menis-
cus at both the top and the bottom. The
readings are made from the extreme bot-
tom of the lower meniscus to the extreme
top of the upper meniscus. Figure 15
shows this graphically. An ordinary pair

ing. The points are placed at the upper
and lower limits, then lowered until one
point is at the 0 mark; the other point
will intercept the scale at the correct per-
centage for the sample tested. Wie, 15. Show:

In some steam testers where the exhaust ing method of
steam escapes into the jacket and no ven- reading fat
tilation is provided, the temperature of column in
the bottles will be too high. In such ae ae a
case, the bottles must be allowed to cool to b, not a to
to 130° to 140° F. by placing them in c, nor a tod.
water at that temperature for several minutes before
making the reading. — .

Imperfect tests—Ii the foregoing directions have been
strictly followed, a perfect test should result. It is not to
be expected, however, that the beginner will always meet
with success. The next two paragraphs may be helpful in
locating the trouble.

An imperfect test is caused by one of three things:
(1) Foam on the fat column obscuring the upper menis-
cus; (2) a dark-colored fat column containing dark parti-
cles and with dark particles obscuring the lower meniscus;

{

16

(3) a light-colored fat column containing white, caseous.
material obscuring the lower meniscus.
The first is caused by using hard water. Any one or a

combination of the following may cause the second trou-

ble: (a) The acid was too strong; (b) too much acid was

used; (c) the acid was too warm when added to the milk;

(d) the milk was too warm when the acid wasadded; (e)

the acid was dropped directly into the milk; (f) the mix-
ing of the acid and the milk was interrupted before the

solution was complete; or (g) the acid and milk were al-

lowed to stand too long in the test bottle before being

mixed. The third trouble is caused by one or more of the

following: (a) The acid was too weak; (6) too little acid

was used; (c) the acid was too cold when added to the

milk; (d) the milk was too cold when the acid was added; —
or (e) the mixing was not continued long enough to dis-
solve all the serum solids.

Tested Babcock glassware.—Babcock-test bottles and
pipettes should always be tested and found correct before
being used. It is now possible to purchase test bottles and
pipettes which have been tested and approved by the
United States Bureau of Standards. Many States also
have officials empowered to test and approve Babcock
glassware. The best way is to purchase it already tested
by the Bureau of Standards, or to have it made to conform
to the requirements of that bureau and then tested by a
State official. _
TESTING CREAM FOR FAT.

While in a general way cream is tested by the Babcock
test in much the same manner as milk, there are some
-modifications that must be observed. The range of fat in
cream, and consequently the specific gravity is much
greater than in milk, so that 17.5 cubic centimeters do not
necessarily represent 18 grams, as in the case of milk.
Cream also varies in consistency, some being thin and some
thick; therefore in some cases much more would adhere
to the walls of the pipette than in others. For these rea-
sons cream can not be accurately measured. The charge
for the test must be weighed into the test bottle.
Cream-test botiles—The cream-test bottles used in the
Babcock test are of various designs, as shown in figures 16,
17, 18, and 19. Those conforming to the requirements of |

17
‘the United States Bureau of Standards differ from milk
bottles only in the graduations and in the length and diam-
eter of the neck. Test bottles are made for both an 18-
gram and a 9-gram charge.

Cream-test balances.—Several types of balances designed
for weighing cream charges are on the market (figs. 20, 21,
and 22). The small torsion balances prove to be very sat-
isfactory if care is taken that the important metal parts

HI
wy
Ve

rn

n
o
3

8

Ty a
te

(nt

oa

ay Map!
r A a aR

aw

Fic. 16.—9-gram, 6- Fig. 17.—18-gram 6-
inch cream bottle. inch cream bottle. _

are not allowed to rust. Balances should be tested for
sensitiveness from time to time and should always be kept
in perfect condition.

Preparing cream. for testing.—The point never to be lost
sight of in testing cream or milk is that the small quantity
taken for the test must be truly representative. No matter
how carefully the test is carried out, if the charge taken
does not accurately represent the cream or milk to be

15037°—16—3

18

tested, the results will be worthless. The preparation of
cream for testing does not differ materially from that of
milk. The fat must be evenly distributed, and if there are

I]
w
Ss

oY ]

Re

Mn} iti

Fic. 18,—18-gram 9-
inch cream bottle.

no lumps this can be accomplished by
pouring from one receptacle to another,
warming the cream slightly if cold. If
lumps are present, it has been advised
to pass the cream through a fine sieve,
rubbing the lumps through with the ©
fingers and then mixing as usual. If
the cream has stood for some time in the
sample jar, the top may have become
hard, leathery, and difficult to remove.
In this case, the jars should be set in
warm water until the contents have
reached 100° to 110° F., when the cream
will be soft and can be easily removed.
Weighing the charge.—After the sam-
ple has become homogeneous through-
out, the charge is quickly weighed into
the test bottle. The weight of the
charge depends upon the style of bottle
used. For this purpose the 9-eram bottle
isrecommended. A pipette is useful in
conveying the cream to the test bottle,
as the flow can be easily controlled and
checked on the drop when the pointer
of the balance indicates that the correct
quantity has beenrunin. This weight
must be exact, and some experience is
necessary before the charges can be
quickly and accurately weighed. :
Completing the test—Instead of add-
ing a measured quantity of sulphuric
acid to the cream in the test bottle, asis

done with milk, the best way is to add the acid until the
mixture assumes the color of coffee to which cream has
been added.! The quantity of acid required to produce
this color varies with the percentage of fat in the cream.
If the cream and acid when mixed are about 70° F., from

10. F. Hunziker and H. C. Mills, Testing Cream for Butter Fat, Indi-
ana Agricultural Experiment Station, Bul. 145. June, 1910.

19

iLL

Fig. 19.—Types of cream bottles conforming to the requirements of the
United States Bureau of Standards.

*

20

4 to 8 cubic centimeters of acid (specific gravity 1.82 to
1.83), depending upon the percentage of fat, will be re-
quired for a 9-gram charge. After adding the acid to the ©
cream, the procedure up to the reading of the percentage

Fic. 20.—Type of knife-edge cream balance.

is exactly the same as in the milk test. After the final
whirling, the test bottles are submerged to a point above the
fat column in water at 135° to 140° F. in a suitable tank.
After remaining in this tank for about 15 minutes they are

Fig. 21.—Type of torsion balance for single bottle.

removed and the readings quickly made. The important
difference between reading the cream test and the milk
test is that in the cream test the fat column included is
from the bottom of the lower meniscus to the bottom, not
the top, ofthe uppermeniscus. (Seefig.23.) Itisadvised

21

to destroy the upper meniscus by dropping into the bottle
at this point a few drops of a liquid in which the fat is
not soluble. Glymol (petrolatum liquidum, U. S8. P.),
known commercially as white mineral oil, gives satisfac-
tory results and may be purchased at almost any drug store.
If desired it may be colored with alkanet root.1_ If glymol
is used, the fat column included in the reading is from the
bottom of the lower meniscus to the line between the fat
and the glymol. If the fat column is read with the upper
meniscus intact, care must be taken that the eye is on a

Fig. 22.—Type of torsion balance for several bottles.

level with the points on the scale at which the readings
are made; otherwise an error will be introduced.

PRESERVING SAMPLES.

If, for any reason, it is desired to keep a sample of milk
or cream for a few days before testing it, a preservative
should be added to prevent decomposition. Formalin
(which is a 40 per cent solution of formaldehyde), corrosive
sublimate (mercuric chlorid), or potassium bichromate
are used for this purpose. Formalin has the advantage of
being a liquid and easily handled; on the other hand, it

1 Hunziker and Mills, loc. cit.

22

has the property of toughening the casein and rendering it
more difficult to dissolve later in the sulphuric acid. One
cubic centimeter should keep a pint or a quart of milk or
cream for two weeks or more. Corrosive sublimate, while
the most powerful of the three, is a deadly poison. Sam-
ples preserved with it should be colored in some way to
indicate the presence of the poison. Tablets of corrosive
sublimate containing coloring matter are
onthe market. If potassium bichromate
is used, the samples should be kept in a
dark place; 15 to 20 grains is sufficient
to preserve a pint for a reasonable length
of time.

CLEANING THE TEST BOTTLES.

After the test, and before the test bot-
tles have become cold, they should be
emptied with a shake or two to loosen
the deposit of calcium sulphate which
accumulates on the bottom. <A conven-
ient device is shown in figure 24. This
consists of a 5-gallon stone jar with a
wooden cover in which one - half-inch
holes have been bored. After the test
the necks of the bottles are placed in the
holes and the contents allowed to run
out, giving each bottle an occasional
Fig. 23—Show- = shake. The bottlesshould then be rinsed

ing method F 5 ac

of reading fat Ut twice with boiling water and, after

column in the outside has been rinsed off, placed

cream testing. in asuitable rack and drained. At fre->
Read from @ quent intervals the bottles should also be

toc,notatob, : : ; 4

Se in given a bath in a dilute solution of lye,

or a solution of soap or cleansing powder.

DETERMINATION OF TOTAL SOLIDS IN MILK.

As brought out earlier in this circular, milk is composed
of water and the various solids collectively known as total
solids or milk solids. Manifestly the simplest way of
determining the amount of total solids in a given quantity
of milk is to separate them from the water and weigh them.

23

This is precisely the manner in which the total solids in
milk are determined in the laboratory. A small quantity
of milk is weighed into a shallow, flat-bottomed dish, and
then heated until all the water is driven off. During this
evaporation the milk must not be heated more than a
degree or so above the boiling point of water, because at a
higher temperature some of the solids are decomposed.

. Ovens.—Several types of ovens are used for holding the
milk at the right temperature during the evaporation.
_ The simplest type is perhaps the so-called double-walled
drying oven (fig. 25). This piece of apparatus is really one
oven inside of another, the space between the two being
partly filled with water. A burner placed under the oven
boils the water, and the remaining space
between the walls is filled with steam, ;
maintaining a constant temperature in |]>—Zam
the inner compartment which holds the
milk dishes. Unless carefully watched,
the oven will “boil dry,” to prevent
which it is a good plan to attach some
sort of condenser. The type of condenser

‘ Fie. 24.—Jar
known as the globe condenser is very sat- =, ity DR
isfactory for this purpose. Some ovens forated cover
are constructed with a constant-level at- for use in
tachment. PMpiyAne test

; ears : bottles.
Balance.—Nice weighings are required

in the determination of total solids in milk, and it is nec-
essary to use the type of balance known as the analytical
balance (fig. 26), the cream-test balance not being sensi-
tive enough for this purpose. On the other hand, the
analytical balance can not be used with advantage in
weighing cream charges. Both balancesare required. An
analytical balance sensitive enough for the purpose can be
purchased for from $30 to $40. A set of accurate analytical
weights will also be required. Space does not permit di-
rections for using the analytical balance. If the operator
is not familiar with its use, he is advised to consult some
elementary treatise on quantitative chemical analysis. It
must be borne in mind that the analytical balance is a very
delicate instrument and should be treated accordingly.

24

t

- Desiccators.—Dishes that are warm can not be accurately
weighed on the balance because air currents are created
which will buoy up the scale pan sufficiently to make the
object appear lighter than it really is. Again, many sub-
stances can not be exposed to the air without absorbing
atmospheric moisture and in this way introducing an error
into the weighing. Tor these reasons it is customary
always to cool the dishes in a dévice known as a desiccator
(fig. 27) before weighing them. A desiccator is a specially —

MM

Fig. 25.—Double-walled drying oven.

constructed covered jar containing a substance like cal-
cium ¢chlorid, which attracts to itself all the atmospheric
moisture in the inclosed space surrounding it. The desic-
cator, containing no moisture, will, of course, permit a sub-
stance to be kept in it without absorbing any. The cal-
cium chlorid, which forms a layer about 1 inch deep on
the bottom of the desiccator, should be renewed as soon as
it shows any signs of moisture. The cover of the desiccator
should be removed only as often as is necessary, and then
for the shortest possible time.

25

Milk dishes —These are best made of aluminum and
should be from 2 to 24 inches wide and about one-half inch
deep (fig. 28). Each dish should bear a number by which

Fig. 26.—Analytical balance.

it can be identified; this number may be scratched or
punched on the side.

Preparing the dishes.—After the dishes are clean and dry
they should be placed in the drying oven for half an hour,
: then removed and placed in the
desiccator until cool. They
should be handled with forceps or
crucible tongs, and as soon as they
are cool they are weighed on the
analytical balance.

: Weighing the charge.—After the

milk has been thoroughly mixed,

it is drawn up in a pipette and

allowed to flow into the dish until

Fic. 27:—Desiccator. a thin film just covers the bottom;

r the dish and milk are then

quickly weighed. The weight of the empty dish sub-

tracted from the last weight is the weight of the charge,
and should be about 2 grams.

26

Evaporating the water.—The dishes containing the milk
are now placed in the oven, dried for about four hours, and
then placed in the desiccator until cool, when they are
weighed. They are then returned to the oven for 30 min-
utes, after which they are cooled and weighed as before.
Tf there is no loss in weight,
or if there isa slight gain in
weight during the 30
minutes, it indicates that all
the water is driven off, and
this last weight minus the

Fic. 28.—Milk dish. weight of the empty dish is

the weight of the total solids

in the charge taken. This multiplied by 100 and divided

by the weight of the charge gives the percentage. If there

was a lossin weight during the 30 minutes, the dishes are

returned to the oven and

dried for another period or

until they cease to lose
weight.

Determination of solids
not fat—The percentage
of solids not fat, or serum
solids, is found by sub-
tracting the percentage of
fat from the percentage of
total solids.

DETERMINATION OF
SPECIFIC GRAVITY
OF MILK.

_For exact work the spe-
cific gravity of milk is de-
termined by comparing the weight of a volume of milk with
that of an equal volume of pure water under controlled-
temperature conditions. For inspection work an instru-
ment known as the Westphal balance or the special
lactometer described in Bulletin 134 of the Bureau of Ani-:
mal Industry, United States a of Agriculture,
is sufficiently accurate.

Fig. 29.— Westphal balance.

27

Westphal balance.—This instrument (fig. 29) consists of
a pivoted beam graduated on one arm and bearing a
plummet or float. The weights in terms of specific gravity
represent unity, tenths, hundredths, thousandths, and
ten-thousandths. With no weight on the beam it balances
when the plummet floats in air. When the unit weight
is in position, it balances when
the plummet floats in pure water

at the proper temperature. Ba
When the plummet is submerged Ea
in a liquid heavier than water, FH
such as milk, additional weights i
are required to bring the instru- uF,
ment to equilibrium. The spe-

cific gravity is read off directly
from the value of the weights
and their position on the beam.
Detailed directions usually ac-
company the instrument.
Lactometers—Most _lactome-
ters are not sensitive enough for
determining the specific gravity
of milk if more than approxi-
mate figures are required. The
use of either the Westphal bal-
ance or the special lactometer,
previously mentioned, is ad-
vised. If, however, only ap-
proximate results are required
the ordinary lactometer, of
which there are several types on
the market, will suffice. :
The lactometer (figs. 30 and 31)
is used exactly in the same man-
ner as is the hydrometer in test-
ing sulphuric acid, directions for which are given on page
10. Care must be taken that the milk is at the temperature
at which the lactometer is standardized and that the lac-
tometer floats freely in the cylinder. The specific gravity
of milk can not be taken until the milk is three or four
hoursold. The point on the scale of the lactometer where
the suriace of the milk intercepts represents the specific

rn

vara

Fig. 30.—Types of ordinary
lactometers.

Fie. 31.—Special lactometer described in Bulletin 134, Bureau of Animal Industry, U. S. Department of Agriculture.

28

gravity which is usually expressed in
Quevenne degrees.! A slight meniscus -
will obscure the surface line, and it is neces-
sary to estimateitsdepth. This will cause
no error if it is remembered that the point
to be read is at the surface of the milk and
not at the top of the meniscus.

A type of lactometer known as the New
York board of health lactometer is in
somewhat general use. The scale of this —
instrument does not give the specific
gravity directly, but is so arranged that
milk having a specific gravity of 1.029
(at 60° F.) will read 100°. As the zero
mark is the point to which it will sink
when immersed in pure water, 100° on the
scale corresponds to 29° on the Quevenne
scale. New York board of health lactom-
eter degree may be converted into Que-
venne degrees by multiplying by 0.29.

CALCULATING TOTAL SOLIDS BY
FORMULA.

When the percentage of fat and the spe-
cific gravity of the milk are known and
only the closely approximate percentage
of total solids is wanted, it should be cal-
culated by the Babcock formula. The
following table and directions for using it
are taken from Bureau of Animal Industry
Bulletin 134:

1Quevenne degrees are converted into specific
gravity by dividing by 1,000 and then adding 1 to
the quotient. This is done at a glance. For ex-
ample, if the Quevenne reading is 32.5, the specific
gravity is 1.0325.

29

_ Table for determining total solids in milk from any given spe-

cific gravity and percentage of fat.

[Per cent total solids.]

Lactometer reading at 60° F. (Quevenne degrees).

30

28

41
47
53
59
65
71
77
83
89
95

0:
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1
2
2

91

97
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9
5
1
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30

Table for determining total solids in milk from any given spe-
cific gravity and percentage of fat—Continued.

[ Per cent total solids.]

Per- Lactometer reading at 60° F. (Quevenne degrees).

- 90/12. 16)12. 41/12. 66/12. 91)13. 16/13. 42/13. 67/13.
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i=)

—

or

8

31

Table for determining total solids in milk from any given spe-
cific gravity and percentage of fat—Continued.

PROPORTIONAL PARTS.

Fraction Fraction Fraction
Lactom-| tobe Lactom-| tobe Lactom-| tobe
eter added to eter added to eter added to
fraction. total fraction. total fraction. total

solids. solids. solids.
od

0.1 0. 03 0.4 0. 10 0.7 0.18

o2 -05 -3 -13 8 - 20

3 - 08 .6 15 9 - 23

Directions for using the table.—-Ifi the specific gravity as
expressed in Quevenne degrees is a whole number, the
percentage of total solids is found at the intersection of
the vertical column headed by this number with the
horizontal column corresponding to the percentage of fat.

Ii the specific gravity as expressed in Quevenne degrees
is a whole number and a decimal, the percentage of total
solids corresponding to the whole number is first found,
and to this is added the fraction found opposite the tenth
under “‘Proportional Parts.’’ Two examples may suffice
for illustration: (1) Fat, 3.8 per cent; specific gravity, 32.
Under column headed 32, 12.57 per cent is found corre-
sponding to 3.8 per cent fat. (2) Fat, 3.8 per cent; specific
gravity, 32.5. The percentage of total solids correspond-
ing to this percentage of fat and a specific gravity of 32 is
12.57. Under ‘‘Proportional Parts” the fraction 0.13
appears opposite 0.5. This added to 12.57 makes 12.70,
which is the desired percentage.

An inspection of the table shows that the percentage
of total solids increases practically at the rate of 0.25 for
each lactometer degree and 1.2 for each per cent of fat.
This gives rise to Babcock’s simple formula: Total solids=
4L+1.2F. (L=lactometer reading in Quevenne degrees
and f=percentage of fat.)

To illustrate the use of the formula the following example
is given: Fat, 4 per cent; specific gravity, 32. In this case
one-quarter of 32 is 8; 1.2 multiplied by 4 is 4.8; 8 plus
4.8 equals 12.8, which represents the percentage of total
solids.

32

This simple formula can be used in cases not provided _
for in the table.

DETERMINATION OF ACIDITY OF MILK AND —
CREAM.

Acidity in milk is attributable to two causes, (1) the pres-
ence in milk of acid phosphates and perhaps of carbon
dioxid, and (2) lactic and other acids produced by the
decomposition of the milk sugar by. bacterial action.
When freshly drawn milk is acid to phenolphthalein, this
acidity is from 0.07 per cent to 0.08 per cent and is owing
to causes given under (1). Lactic acid is not present in
freshly drawn milk; it develops.only on standing. Milk
is not sour to the taste until it has a total acidity of at
least 0.3 per cent.

For convenience the total acidity of milk is usually
calculated as lactic acid. The principle upon which the
determination of acidity is based is the well-known
chemical action of acids upon alkalies. To illustrate, the
action of hydrochloric (sometimes called muriatic) acid
on a solution of caustic soda may be taken. This acid
has a sharp and very sour taste, while caustic-soda solu-
tions have a soapy feel and a peculiar odor, and if suffi-
ciently strong will attack the skin. If the solution of
caustic soda is slowly added to the hydrochloric acid, the
sour taste will gradually disappear until the exact point of
neutrality is reached, when a new substance is produced—
sodium chlorid, or common salt, which has neither the
acid properties of the one nor the alkaline properties of
the other. The sense of taste, however, is not sufficiently
sensitive to determine when the exact point of neutrality
has been reached. Phenolphthalein is an organic com-
pound, having the property, when in solution, of turning
pink with alkalies and remaining colorless with acids.
_ Such a substance is called an indicator because it indicates
by a color change when a certain chemical reaction has
taken place.

There are several so-called acid tests before the public.
The one known as Manns’s acidity test is widely used and
is conducted as follows:

33

MANNS’S ACIDITY TEST.

Apparatus required:

One 50 cubic centimeter glass burette graduated to
tenths, with stopcock.

One 50 cubic centimeter pipette.

One 250 cubic centimeter beaker, or a white teacup.

One support for burette.

Glass stirring rods.

One-tenth normal solution of caustic soda, each cubic
centimeter of which will neutralize 0.009 gram of
lactic acid.

An alcoholic solution of phenolphthalein made by
dissolving 10 grams in 300 cubic centimeters of 90
per cent alcohol. ;

One who has not had training in chemistry should not
attempt to make the tenth-normal solution of caustic soda,
as it can be purchased to better advantage from any
chemical supply house.

Conducting the test —With the pipette 50 cubic centi-
meters of the milk or cream is measured into the beaker or
cup. If the cream is thick, it may be slightly warmed.
The burette is filled with the tenth-normal caustic-soda
solution so that the lowest part of the meniscus is level
with the zero point on the graduations. The solution is
now run slowly from the burette into the milk or cream,
stirring with a glass rod at the same time. It will be
noticed that the alkali at once produces a pink color where
it strikes; this, however, disappears on stirring. As more
and more of the alkali is added, it will be noticed that the
pink color is slower in disappearing until finally it becomes
permanent fora time. Toward the end, the alkali should
be added drop by drop and the very first appearance of a
permanent faint pink is the signal that the neutral point
has been reached. This color, on account of absorption
of carbon dioxid from the air, will disappear after standing
a short time. The number of cubic centimeters of alkali
used can be learned by referring to the burette, remember-
ing that the reading is taken from the lowest point of the
meniscus.

34

The percentage of acidity is calculated by multiplying
the number of cubic centimeters of alkali solution used
by 0.009 and dividing by the number of cubic centimeters
of milk or cream taken, the quotient being multiplied by
100. Thus:

ce. c. alkalix .009
c. c. sample tested * 100.

If 50 cubic centimeters of the sample required 10 cubic
centimeters of the alkali to neutralize, the percentage of
acidity would be

10 .009
50

Percentage of acidity=

100, or 0.18 per cent.

THE DETECTION OF PRESERVATIVES.

The preservatives usually met with are formaldehyde,
borax, and boric acid, and these are not difficult to
detect if care is used in conducting the tests. Until one
is thoroughly familiar with the tests it is a good plan to
run three samples together, one being the suspected
sample, one which is known to contain the preservative
looked for, and one known to be free from that preserva-
tive.

Formaldehyde.—There are two well-known tests for
detecting formaldehyde, one known as the Hehner test
and the other as the Leach test.

In the Hehner test, about 5 cubic centimeters of the
milk is placed in a 6 by 4 inch test tube, and then about
the same quantity of concentrated sulphuric acid to which
a trace of ferric chlorid has been added. The acid is
allowed to run down the side of the test tube so as not to
mix with the milk. In a few minutes the presence of
formaldehyde will be indicated by a violent coloration at
tne juncture of the milk and the acid. This must not be
confused with the charring of the milk by the acid. A
modification which avoids this charring is in use in the
dairy laboratory of the Bureau of Chemistry, United
States Department of Agriculture, the only difference
being that the sulphuric acid used is diluted with water
until it has a specific gravity of 1.8.

The Leach test, which is the more delicate test of the
two, is conducted as follows: To 10 cubic centimeters of

35

the milk in a white teacup, 10 cubic centimeters of con-
centrated hydrochloric acid (specific gravity 1.2) contain-
ing one part by volume of a 10 per cent ferric-chlorid
solution per 500 parts is added and the mixture brought
slowly to a boil over a Bunsen burner. Formaldehyde is
indicated by a violent coloration varying in intensity with
the amount present.

Boraz and boric acid.—Twenty-five cubic centimeters of
the milk is treated with limewater until a piece of red
litmus paper when immersed in it turns distinctly blue.
The mixture is evaporated to dryness in a small platinum
or porcelain dish and then burned to an ash. A few drops
(not too much) of hydrochloric acid are added to the ash,
and then a few drops of water. A strip of turmeric paper
is then dipped in the solution. When the turmeric paper
becomes dry, it will be of a cherry-red color if borax or
boric acid is present. The test is still more certainil,
when the paper is moistened with an alkaline solution, it
turns a dark-olive color.

A test for the detection of borax or boric acid which is in
use in the dairy laboratory of the Bureau of Chemistry,
United States Department of Agriculture, and by which
the ignition of the milk is avoided, is conducted as follows:
Ten cubic centimeters of the milk is mixed with 5 cubic
centimeters of hydrochloric acid in a white cup. A strip
of turmeric paper about 3 inches long is suspended in the
mixture so that at least 2 inches of the dry strip remain out
of the liquid. The dry portion of the paper will gradually
become moist by capillarity, and if borax or boric acid is
present the paper will take on a reddish-brown tint. If
only a trace of the preservative is present, several hours
may be required for this color to develop. A drop of am-
monia water on the red portion will produce an olive-
green color, which becomes lighter, and finally disappears
as the ammonia evaporates.

36

CHEMICALS AND APPARATUS USED IN THE
CHEMICAL ANAYLSIS OF MILK AND CREAM.

Chemicals: Apparatus—Continued.

Ammonia water.

Borax or boric acid.

Caustic soda.

Caustic soda, tenth-
normal solution.

Caustic potash.

Corrosive sublimate.

Ether.

Ferric chlorid.

Formaldehyde.

Hydrochloric acid, con-
centrated.

Potassium bichromate.

Phenolphthalein.

Sulphuric acid, com-
mercial.

Sulphuric acid, pure
concentrated.

Litmus paper, blue.

Litmus paper, red.

Turmeric paper.

Apparatus:

Balance, analytical,
with weights.
Balance, cream test.
Balance, Westphal.
Babcock tester.
Beakers, 250 c. c. and
500 c. c.
Burner, Bunsen.
Burette, 50 c. c., gradu-
ated to tenths, with
, stopcock.

- Cylinder, for acid hy-

drometer.

Cylinder, for lactome-
ter.

Condenser for oven.

Desiccator.

Dishes, milk.

Dishes, evaporating,
either porcelain or
platinum.

Drying oven, double-
walled.

Forceps.

Hydrometer, acid.

Jars, sample.

Jars, stoneware.

Lactometer.

Measure, acid, 17.5 c¢. c.

Pipette, 17.6 c. c.

Pipette, 50 c. c.

Stirring rods, glass.

Support for burette.

Test bottles, Babcock,

for milk.

Test bottles, Babcock,
for cream.

Tongs, crucible.

Test tubes, 6 by inch.

37

Comparison of metric and customary weights and measures.

Customary

: Equivalents in
weights and .
ESTOS. metric system.
Mainehe = 2552.22 2.54 centimeters.
I foot=). -as=2-- 0.3048 meter.
1squareinch. _| 6.452 square centi-
meters.
1 square foot. -| 9.29 square deci- |
meters.
1 cubic inch.-.}] 16.387 cubic centi-
meters.

1 cubic foot - - .| 0.0283 cubic meter.

1 fluid ounce. .| 29.57 cubic centi-
meters.

1 quart....-.-- 0.9464 liter.

1 gallon. -| 3.7854 liters.

1 grain... .-| 64.8 milligrams.

28.35 grams.

yo.
1 pound (ay.)-.| 0.4536 kilogram.

Metric . .
" Equivalents in
weights and
ST STDS. customary system.
1 meter...... 39.37 inches.
1 meter. ...--| 1.0936 yards.
1 square cen- | 0.155 square inch.
timeter.
1square met- | 10.764 square feet.

er.

1 cubic centi-

meter.

1 cubic centi-

meter.

1. cubic deci-

meter.
1 liter. ..-

1 kilogram...

0.061 cubic inch.
0.0338 fluid ounce.
61.023 cubic inches.

1.0567 quarts.

-| 2.6417 gallons.
15.43 grains.
0.035274 ounce.
2.2046 pounds (av.)

Comparison of Fahrenheit and Centigrade thermometer scales.

Fah- | centi- Fah.
_ren- aide ren-
heit. gr heit.
° ° °
212 100. 00 183
211 99. 44 182
210 98. 89 181
209 98. 33 180
208 97.78 179
207 97.22 178
206 96. 67 177
205 96. 11 176
204 95.55 175
203 95. 00 174
202 94, 44 173
201 93. 89 172
200 93.33 171
+ 199 92.78 170
198 92.22 169
197 91. 67 168
196 91.11 167
195 90. 55 166
194 90. 00 165
193 89:44 -164
192 88. 89 163
191 88. 33 162
190 87. 78 161
189 87. 22 160
188 86..67 159
187 86. 11 158
186 85.55 157
185 85. 00 156
184 84. 44 155

Centi- a es Centi-

grade. fart grade.
83. 89 154 67.78
83.33 153 67.22
82.78 152 66. 67
82.22 151 66. 11
81. 67 150 65. 55
81.11 149 65. 00
80.55 148 64. 44
80. 00 147 63. 89
79. 44 146 63. 33
78. 89 145 62.78
78. 33 . 144 62. 22
77.78 143 61. 67
77.22 142 61.11
76. 67 141 60. 55
76. 11 140 60. 00
75.55 ~ 139 59. 44
75. 00 138 58. 89
74, 44 137 58.33
73. 89 136 57.78
72.33 135 Dieee
72.78 134 56. 67
71.22 133 66.11 ©
71. 67 132 55. 55
71.11 131 55.00
70. 55 130 54, 44
70. 00 129 53. 89
69, 44 128 53. 33
68. 89 127 52.78
68. 33 126 52.22

38

Fahrenheit and Centigrade thermometer scales—Continued.

Centi- Centi- Centi- 4
ren- = -

heit, | grade. heit grade heit grade.
125 51. 67 82 27.78 | 39 3.89
124 51.11 81 27.22 38 3.33
123 50. 55 80 26. 67 37 2.78
122 50. 00 79 26.11 36 222
121 49. 44 78 25. 55 30 1, 67

120 48. 89 77 25.00 || 34 1,11 ~
119 48. 33 76 24. 44 33 0. 55
118 47.78 75 23. 89 32 0. 00
117 47,22 74 23.33 31 — 0.55
116 46. 67 73 22.78 30 |} — 111
115 46. 11 72 22.22 29 — 1.67
114 45.55 va 21. 67 28 — 2.22
113 45. 00 70 21.11 PAY — 2.78
112 44,44 69 20. 55 26 — 3.33
111 43.89 68 20.00 |! 25 — 3.89
110 43.33 67 19.44 || 24 | — 4.44
109 42.78 66 18. 89 23 — 5.00
108 42.22 65 18. 33 22 — §.55
107 41. 67 64 17.78 | 21 — 6.11
106 41.11 63 17. 22 20 — 6.67
105 40.55 62 16. 67 19 — 7.22
104 40. 00 61 16.11 | 18 — 7.78
163 39. 44 60 15.55! 17 — 8.33
102 38. 89 59 15. 00 16 — 8.89
101 38. 33 58 14. 44 15 | — 9.44
100 37.78 57 13. 89 14 —10. 00
99 37.22 56 iB} 88 13 —10. 55
98 36. 67 55 12.78 12 —11.11
97 36.11 54 12.22 11 —11, 67
96 35. 55 53 11. 67 10 —12.22
95 35. 00 52 11.11 9 —12.78
94 34. 44 51 10. 55 8 —13. 33
93 33. 89 50 10. 00 7 —13.89
92 33.33 49 9. 44 6 —14, 44
91 32.78 48 8.89 5 —15.00
90 32. 22 47° 8.33 4 —15. 55
89 31. 67 46 7. 78 3 —16.11
88 31.11 45 7.22 2 —16. 67
87 30. 55 44 6. 67 1 —17. 22
86 30. 00 43 6.11 0 | —17.78
85 29. 44 42 5.55 -— 1 —18. 33
84 28. 89 41 5.00 —2 | —18. 89
83 28. 33 | 40 4.44 —3 —19, 44

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