The San Juan islander. [volume] (Friday Harbor, Wash.) 1898-1914, 1912-07-26

IhlllY I :. ]. :. :.
j Notes and Instructions from Aoricui
i Of Oregon and Kashinoton Special
MATHEMATICS BY MILK TEST
| Q. A. G. Professor Shows How t.
| Teach Per Cent Problems.
That school teachers, especially thos,
in rural districts, can make the sub
ject of percentage easier and more in
teresting to their pupils by using
problems on the application of TIT
Babcock milk test was shown to thu
teachers attending the summer session
at the Oregon Agricultural college il
a lecture by Prof. F. L. Kent, of the
dairy department. He first gave 9
demonstration of the test, that ali
might understand It's workings clearly
"The Babcock test has done more to
revolutionize dairying than any othe,
one thing in quarter of century, u
said Prof. Kent in introduction. "With
it and the cream separator, dairyinp
has been put on very different basis
than before. In nearly all the discus
sions of milk and it's handling you
hear something of the fat content, and
the Babcock test is the one commonly
used to find this content. The man
who supplies milk to a retailer does
m under tha Rahrock too%
"The test bottle in which the sam
pie of milk is measured holds an ounce
and half, and has graduated scale
on the long neck to aid in reading the
fat content.
There are two sources of error,
some bottles being incorrectly grad
uated on this scale, and some being
inaccurate in size. A definite guam
tity of milk must be taken to make
the test. and pipette Ga glass tube
larger in the middle, and graduated)
is used to suck up the sample from the
container. The milk to be tested is
poured from one cup to another sever
al times, to make sure that it is of an
even quality throughout, and has no
CI0ou SIduulu& OIl up.
"a third glass measure is used to
measure the acid necessary for the
test. These three pieces of glass and
the centrifugal motion whirler make
up the outfit for the test. Since the
glassware is unpatented, it is all
practically the same, but the machines
for whirling the bottles are Of differ
ent types.
"The pipette takes up 18 grams, or
1876 cubic millimeters of milk, which
is put into the test bottle. Then COM
mercial sulphuric acid is added, to
about the same quantity as the milk,
to dissolve all the Ingredients of the
milk except the fat. setting that free
30 that it can rise into the neck of the
hottie. The milk and acid are mixed
by rotary motion of the bottle to get
a uniform color, rich, dark brown,
50 that the acid may act on all the
milk.
"After the test bottles are put into
the whirler they are in motion about
FIVE minutes. Jersey milk generally
runs as much as so per cent higher in
fat content than the Holstein. The
| Ayrshire has medium fat content of
3.5 to 4 per cent. The Holstein has
about per cent as rule. When the
test bottle is taken from the whirler,
enough hot water is added to allow
the fat to rise we'll up in the tube, and
the sample is whirled again. When it
is taken out finally. the fat shows in a
clear yellow band in the neck of the
bottle. The best way of measuring it
accurately is by measuring with p
pair of dividers the band of fat, then
putting one leg of the dividers on
zero, and the upper leg will indicate
the precise per cent of fat content of
the milk in each 18 grams.
"The Babcock test is being used as
one Of the regular demonstrations in
schools where agriculture is being in
troduced. Teachers can get accurate
glassware by having it tested by the
state experiment station, or by sinsist-
| ing that the manufacturers guarantee
the goods. It should be pointed out
that one source of errors in the test is
in the taking of the sample. When
taken with spoon from the top Of a
pan after the milk has stood, the fat
content will be inordinately high.
sThe Babcock test is one OF the
best ways Of teaching percentage in
arithmetic classes. For example, it q
COW produces Sc pounds of milk day,
which tests &c per cent, her produc-
tion is 1.456 pounds of fat a day. Il
. COW gives AZ pounds, but the test is
3.5 per cent, she will give LAT pounds
of fat. Carrying the problem out by
means Of daily records to the end OF
the month, q COW producing TO
pounds in month with test OF 80
per cent, will give 25.375 pounds OF
fat Z month. Or, a COW giving AZ
pounds day. produces /, $50 pounds 9
i month, which, at test Of -O35, gives
I44.1 pounds of fat month. The
problems may further be elaborated
| by finding the gain in dollars, suppos-
ing the value Of the butter fat on the
market to be. say, q cents pound.
l nd ntt1Ry