204 MODERN METHODS OF TESTING MILK 



may be decreased without adding water, (i) by add- 

 ing skim-milk, (2) by adding milk poorer in fat, or 

 (3) by skimming part of the milk and then putting 

 the skim-milk thus obtained back into the rest of the 

 normal milk. 



Prof. R. A. Pearson, of Cornell University, has de- 

 vised an ingenious method by which one can accu- 

 rately, quickly and easily find the amounts of milk, 

 cream and skim-milk to be used in modifying or stand- 

 ardizing milk in order to produce a milk containing a 

 desired per cent, of milk-fat. The following diagram 

 and explanation may serve to make clearer the work- 

 ing of the method: 



Per cent, fat in milk=A - - ,C B or B C (pounds of A to use 



Per cent, fat inj 



cream, etc. | =C .A B or B A (pounds of C to use) 



Cream or skim- 

 milk, etc. 



Let A represent the per cent, of fat in the milk 

 to be modified. 



Let B represent the per cent, of fat desired in the 

 modified milk. 



Let C represent the per cent, of fat in the milk, 

 cream or skim-milk which is to be used in increasing 

 or decreasing the per cent, of fat. 



The problem is to find in what proportions we shall 

 use the milk, etc., containing A and C, in order to ob- 

 tain a product containing B. 



When the per cent, of fat in the normal milk is 

 to be increased, A is less than B, while C is greater 

 than B. In this case, B minus A gives the pounds of 



