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 snlphnric 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. 



(i) Action on scni}n-soIids 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) Hcaf fiiniishcd 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 scrum 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 larcielv from the form of an emulsion in the milk- 



fc.' 



