Gloucester County Democrat. (Woodbury, N.J.) 1878-1932, 1897-07-29
THE LACTOMETER


specific gravity of pure milk varies
somewhat according to the richness OF
the milk. 70 say that milk has spe-
cific gravity of 1.029 at temperature of
so degrees is to say that il is 1.029
times as heavy as water, a little heavi-
er, that is. The specific gravity 1.029
is considered a good enough standard
for ordinary milk. Any milk which is
not that much heavier than water has
been weakened and adulterated unless
it is SO rich in fat as to be lighter than
water Then the Babcock test must be
used.
Now for the laotometer and how to
use it. Professor W. W. Hall of Cornell
university desert bes it and gives direc-
tions for its use as follows:
This instrument is form Of hydrom
eter for determining the specific gray
ity of milk The ordinary or board Of
health lactometer is graduated from 0
to 1870. When immersed in distilled
water at a temperature of go degrees
F., it sinks to the mark. When i'm
mersed in milk whose specific gravity
is 1929 at temperature of so degrees
f., it sinks to the 100 mark. Such milk
is considered pure as it has been found
that milk seldom if ever is poor enough
in solids to have a lighter specific gray
ity than 1929
This graduation from 100 to the 0
mark is equally divided and is made
for the purpose of testing milk whose
specific gravity is less than 1.029. When
this condition is found, it almost al
ways follows that the sample tested has
been diluted with water or some other
fluid.
The graduation from 100 to 1870 is
made for the purpose of testing milk
whose specific gravity is greater than
1929 Most milk has specific gravity
higher than l. 029, and i'll some cases it
has been found as high as l.035, the
average being 1.032.
The Quevenne lactometer is gradu-
ated from 10 to 40. When immersed in
milk at temperature of 60 degrees F.,
whose specific gravity is 1929, it sinks
to the 80 mark The graduation to Is
is for testing milk whose specific gray
ity is less than 1.029. The graduation
from 90 to 40 is for testing milk whose
specific gravity is greater than 1.029.
Thus it will be seen that 100 on the
ordinary and 80 on the Quevenne are
coincident. If the Quevenne is used, the
specific gravity can be determined by
prefxing / and Q. If the Quevenne
reading is 80. we would write 1.030,
which would be the correct specific
gravity. 1t is not necessary to bring the
milk to temperature of 60 degrees, as
a correction can be made by adding one
degree to the ordinary laotometer read
ing to every three degrees Of temper
ature above so, and by subtracting one
from lactometer reading for every three
degrees of temperature below 60. This
corrects the reading from 90 to 20 de-
grees of temperature, but if milk is cold
or than so degrees it were better tic
warm it to 90 degrees. If warmer than
20 degrees, it We're better to cool it to
20 degrees.
This may be satisfactorily deter
mined by the operator by making care
full test at 20 degrees, correcting it as
explained above, then cooling to 60 de-
grees and comparing results. If the
Quevenne lactometer is used, the cor
rection is made by adding one-tenth to
every one degree of temperature above
60 degrees and subtracting one-tenth
for every one degree below GO degrees
There are instances where milk can
have specific gravity of less than
1.029 and be pure and unadulterated,
as in the case of milk exceedingly
rich in fat If the fat has passed
the point where the albuminoids re-
fuse to follow, and, if it has specific
gravity of 94-100, which is lighter,
the ordinary lactometer will sink below
the go degree mark, and the Quevenne
will sink below the 80 mark For
this reason, where any doubt exists
as to the purity of the milk, sample
should be tested by the Babcock test,
and the per cent of fat ascertained be-
fore taking sample for analysis and a
duplicate given to the accused.
An experienced person can quite cas-
lily determine by the appearance of the
milk whether light specific gravity is
caused by the milk being exceedingly
rich in fat or whether it is caused by
dilution. To insure accuracy, where
any serious doubt exists, the Babcock
test should be used.
#, as in many cases, the ordinary
laetemeter sinks into milk to the so
mark, corrected, or the Quevenne to the
23 mark. it is safe to take duplicate
samples and deliver oHe to the accused
then and there without further test, as
you may rest assured that such milk
will contain more than 88 per cent of
water, less than 10 per cent of solids
and less than per cent of fat, but
when the ordinary, for board of health,
lactometer is used and q sample of milk
is found to show lnctoDeter standing
anywhere in the nineties, while there
is very little doubt about it being di-
luted, it is safe to take the per cent of
fat, even if the formula for ascertaining
solids Is not used. A great many sam
Piles of diluted milk will contain 8 per
cent of butter fat and yet be below IL
per cent total solids.