TKSTING FOR BUTTERFAT 611 



order to have .18 grams butterfat represent 1 per cent of the milk 

 or cream tested, .18 X 100 or 18 grams of milk or cream must be 

 used. 



In the case of milk, the sample, for convenience's sake, is 

 measured, instead of weighed into the test bottle. The average 

 specific gravity of milk is 1.032. Hence 18 grams of milk have a 



1 8 

 volume of y-?)T2 or ^>44 cubic centimeters. But when milk is 



poured from the pipette, approximately .15 c.c. remain in the pipette 

 and fail to be discharged into the test bottle. For this reason a 

 poured from the pipette, approximately .15 c.c. remain in the pipette 

 delivers 18 grams of milk. 



In the case of cream, the specific gravity varies very greatly 

 with the richness of the cream and the amount of foam it contains, 

 hence the measuring of the cream into the test bottle introduces 

 considerable error. For this reason the cream is weighed, and not 

 measured, into the test bottle, using 18 grams. In the course of the 

 development of the Babcock test for cream, it was found desirable 

 to reduce the charge of cream used for the test from 18 grams to 9 

 grams, and accordingly the percentage graduation in these cream 

 test bottles was modified to the effect that each 1 per cent of the 

 graduation has a capacity of .1 cubic centimeter which corresponds 

 to .09 grams of butterfat. In the use of these so-called 9 gram 

 cream test bottles, therefore, .09 X 100, or 9 grams of cream are 

 weighed into the test bottle and the graduation again represents per 

 cent. 



SPECIFICATIONS FOR STANDARD APPARATUS AND 



CHEMICALS FOR TESTING MILK AND CREAM 



FOR BUTTERFAT BY THE BABCOCK TEST 1 



1. Apparatus and Chemicals. 



Milk Test Bottle. 8 per cent 18 gram milk test bottle, gradu- 

 ated to 0.1 per cent. Graduation The total per cent graduation 

 shall be 8. The graduated portion of the neck shall have a length 

 of not less than 63.5 mm. (2y 2 inches). The graduation shall repre- 

 sent whole per cent, five-tenths per cent and tenths per cent. The 

 tenths per cent graduations shall not be less than 3 mm. in length ; 

 the five-tenths per cent graduations shall be 1 mm. longer than the 



1 Hunziker, Journal of Dairy Science, Vol. I, No. 1, May, 1917. 



