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74
Of the above, samples P 47, P 48 and T 57 are deficient in solids-not-fat,
the percentages of fat are very high particularly for the month of May.
Under present conditions with regard to the supply of milk from cowsheds
the afternoon milk will always be considerably richer in fat than the morning
supply and morning unbulked milk will be liable to be below the standard.
During the year this apparatus has been obtained in order to obtain
more certain evidence of the addition of water to milk. The method depends
on the fact that genuine milk from healthy cows, whatever its chemical
composition, freezes at a point which is within a known range.
The method is official in Holland and in America for the detection of
watered milk.
The Hortvet
Cryoscope.
The freezing point of milk, as determined by means of the Hortvet
apparatus ranges from —0.535° C. to —0.560° C. In Holland a depression
of less than 0.53° C. is regarded as definite proof of adulteration. In America
the added water is calculated on an average figure of —0.55° C. and a tolerance
of 3 per cent. of added water allowed unless this figure is exceeded; this
is the same as fixing a limit figure of —0.533° C.
Some of the results obtained are given below and these show that
useful information in doubtful and other cases of adulteration may be obtained.
An average figure of —0.54° C. has been taken as a basis for calculation.

Column 4 in the above table shows the amount of added water calculated
from the legal minimum of 8.5 per cent. of solids-not-fat. The amount of
water so obtained is usually an under estimate of the truth as genuine commercial
milk will normally contain more than the legal minimum of 8.5 per
cent. of solids-not-fat; the added water required to dilute this milk to the
legal minimum of 8.5 per cent. is not included.