VARIATIONS OF MILK CONSTITUENTS 17! 



calculated amount; (4) in 2 cases the calculated per 

 cent exceeded that found by the chemical method to 

 the extent of 0.23 and 0.25 per cent. It is thus seen 

 that, taking the entire season's average, 80 per cent 

 of the results by the method of calculation differed 

 from those obtained with the chemical method by 

 less than o.i per cent. The results given below 

 represent the application of the formula in case of herd 

 milk : 



Per cent of fat Per cent of casein in milk, as found by 



in milk (1) (2) 



Chemical method Calculation 



3.25 2.38 2.20 



3.31 2.19 2.22 



3.42 2.27 2.27 



3.52 2.30 2.30 



3.55 2.34 2.32 



3.55 2.18 2.32 



3.63 2.45 2.35 



3.63 2.33 2.35 



3.71 2.29 2.38 



3.71 2.48 2.38 



3.71 2.35 2.38 



3.84 2.44 2.44 



3.84 2.37 2.44 



3.92 2.42 2.47 



4.00 2.53 2.50 



4.14 2.50 2.56 



425 2.51 2.60 



4.31 2.37 2.62 



For ordinary purposes, where the strictest accu- 

 racy is not required, the rule can be used with quite 

 satisfactory results, when applied to herd milks 

 within the limits specified, and most of our cheese- 

 factory milks come within these limits. Of course, 

 it is readily recognized that, when very accurate 

 results are necessary, only a direct determination 

 of casein by an accurate method can suffice for the 

 purpose ; and, by an accurate method, is meant one 

 which can be relied upon to give results within one- 

 tenth of one per cent of the truth. 



