Testing Butter, Cheese and Cream 97 



milk fat equivalent to 10 per cent of the weight of 

 the milk taken. Each 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 



