315] Babcock's Centrifugal Method 189 



temperature be 55 C. At this temperature the specific gravity 

 of fat is '9. 



A small correction should be made for the specific gravity 

 of the milk, but it is customary, when testing milk, to have a 

 pipette graduated to hold exactly 18 c.c. of milk of normal 

 density — viz., 1*03. 



315. Remarks on the Results of Milk Analysis. — The two 

 methods used in tampering with milk are the addition of water 

 and the removal of cream. In calculating the extent to which 

 either of these operations has been carried on, the analyst 

 assumes the milk to be of the lowest probable quality before 

 adulteration, and states his results calculated on this assump- 

 tion as ' minimum ' adulteration. The minimum standard for 

 pure milk is generally agreed upon as 9 per cent. ' solids not 

 fat ' and 3 per cent, fat, though the ' Somerset House ' standard 

 is rather lower. 1 To calculate added water^ let a be the per- 

 centage of solids not fat. Then the percentage of added 

 water will be at least 



100a 

 100 . 



9 



To calculate the percentage of fat removed from milk which 

 has been skimmed, let a be the percentage of solids not fat and 

 b the percentage of fat; then the minimum amount of fat 

 removed from 100 parts of the original milk 



= =- — b parts. 

 9 



1 The introduction of the * Adams ' process gave rather higher per- 

 centages of fat than had been obtained before. Hence the percentage of 

 1 solids not fat ' became lower. The ' Somerset House ' analysts apparently 

 accept the lowered value of 8-5 instead of 9-0 for the • solids not fat.' 



