THE BABCOCK TEST 33 



PRINCIPLES AT BASIS OF BABCOCK TEST 



This method is based on the action of two agents : 

 (i) the action of strong sulphuric acid upon the con- 

 stituents of milk-serum, and (2) the action of cen- 

 trifugal force. 



Action of sulphuric acid in Babcock test. The sul- 

 phuric acid used in the Babcock test performs, at least, 

 three functions, which we will consider briefly. 



(1) Action on serum-solids of milk. Strong sul- 

 phuric acid acts chemically and physically upon the 

 milk-serum solids (casein, sugar, albumin and salts) 

 in such a way as to destroy that strong mechanical, ad- 

 hesive influence exerted by the milk-serum solids, 

 which tends to prevent the fat-globules separating 

 from the form of an emulsion. When this influence is 

 overcome, the fat-globules are more free to collect in 

 a mass. 



(2) Heat furnished by action of sulphuric acid. 

 The action of sulphuric acid upon the water of milk- 

 serum and also upon the organic solids of the serum 

 generates so much heat that the fat-globules easily lose 

 their individuality and run together, a condition favor- 

 ing rapid separation of fat from serum. 



(3) Specific gravity of serum increased by sulphuric 

 acid. The sulphuric acid, being nearly twice as heavy 

 as milk, increases the difference in specific gravity be- 

 tween the milk-fat and the liquid surrounding it. The 

 milk-fat, being much lighter, more readily rises to the 

 surface of the heavy liquid. 



Action of centrifugal force in Babcock test. The 

 action of the sulphuric acid having released the milk- 

 fat largely from the form of an emulsion in the milk- 



