I5O MODERN METHODS OF TESTING MILK 



cream before churning, the following rule is suggested 

 by Van Norman (Bulletin 104, Purdue Univ. Agr. 

 Exp. Sta.) : From 100 subtract the per cent, of fat 

 in the cream tested and multiply the result by .9, or, 

 expressed as a formula, (100 per cent, of fat in 

 cream) x.g. For example: 



Cream with 20 per cent, fat requires .72 per cent, of 

 acidity. 



Cream with 25 per cent, fat requires .67 per cent, of 

 acidity. 



Cream with 30 per cent, fat requires .63 per cent, of 

 acidity. 



Cream with 35 per cent, fat requires .58 per cent, of 

 acidity. 



The use of .9 as a factor for multiplying may not 

 suit all conditions and some other factor, .8 for exam- 

 ple, may be used. Each operator may experiment and 

 easily find what per cent, of acidity is best adapted to 

 the production of the butter suiting his market, and 

 then a table like the above can be made, using .9 or 

 some other factor. 



OUTLINE STATEMENT OF SOME SPECIAL 

 PRECAUTIONS IN TESTING ACIDITY 



1. The material to be tested for acidity must be 

 thoroughly mixed before sampling for a test. 



2. The water used in preparing the alkali solution 

 and in rinsing the pipette should be neither acid nor 

 alkaline and should be soft and clean. Use distilled 

 water if possible. The standard solution must be of 

 the exact strength desired. 



