TESTING FOR BUTTERFAT 623 



bottles from the properly mixed sample by means of a 9 or 18 cc. 

 pipette which has a short, wide-bore delivery tube. In this manner 

 spilling is readily avoided and the work is most rapid. If any 

 cream is spilled over the outside of the bottles or on the balance, it 

 should be wiped off immediately and before the weighing is com- 

 pleted. 



Making the Test. Three methods of performing the test have 

 been adopted as standard methods; each of which, when properly 

 executed, insures accurate results, but methods II and III are pre- 



Fig\ 97. Jalco Electric Centrifuge Tig. 98. Facile Steam Turbine 



Courtesy Jalco Motor Co. Tester 



Courtesy D. H. Burrell & Co. 



ferred to method I, as they leave less to the judgment of the oper- 

 ator and therefore are more nearly "fool-proof :" 



Method I. Add standard commercial sulphuric acid until the 

 mixture of acid and cream, immediately after shaking, resembles 

 in color, coffee with cream in it. Usually about 8 to 12 cc. of 

 acid is required in the case of the 9-gram bottle or 14 to 17 cc. 

 of acid in the case of the 18-gram bottle, the amount needed depend- 

 ing on the temperature of acid and cream and on the richness of 

 the cream. 



Whirl in Standard Babcock centrifuge at proper speed, five, 

 two and one minutes, respectively, filling the bottles with hot, soft 

 water, temperature 140 F. or above, to the bottom of the neck after 

 the first whirling and to near the top graduation after the second 

 whirling. 



