Testing Butter, Cheese and Cream 97 
milk fat equivalent to 10 per cent of the weight of 
the milk taken. Hach subdivision of the scale, 
therefore, represents .2 of 1 per cent. The capa- 
city of the graduated portion of the neck is two 
cubic centimeters. The specific gravity of melted 
milk fat at a temperature of 120° F. is assumed to 
be .9. The two cubic centimeters will, therefore, 
weigh 1.8 grams, and in order that the percentage 
of fat read off shall be percentage by weight and 
not by volume, 18 grams of milk must be taken. 
But milk has an average specific gravity of 1.032, 
therefore 18 grams of milk will be contained in 
17.44 cubic centimeters. Two cubic centimeters of 
melted milk fat is, therefore, 10 per cent by weight 
of 17.44 cubic centimeters of average milk. It 
has been found by trial that a pipette of the. or- 
dinary form graduated at 17.6 cubic centimeters 
will deliver slightly less than 17.5 cubic centimeters 
of milk. The graduation of the ordinary pipette 
should, therefore, be 17.6 cubic centimeters. A 
little less acid than milk is ordinarily required, and 
the acid measure is graduated at 17.5 cubic centi- 
meters, though the amount of acid actually used 
may readily vary two or three cubic centimeters 
either way from this point. 
The fat in the various products of milk may 
be as readily determined by means of this test as 
fat in the milk itself, and for these determinations 
various forms of -special apparatus have been de- 
vised. (Fig. 14.) For testing cream, bottles with a 
capacity greater than 10 per cent are in use. Of 
