180 THE ANALYSIS OF MILK. 



the reading of the fat is made more accurately than when an 

 attempt is made to read either to the bottom or center of the 

 meniscu^s. 



It is best to read the fat column immediately after the addi- 

 tion of the alcohol, because, if the latter is allowed to remain 

 in the fat column for several hours, it mixes with the fat to a 

 certain extent and the reading cannot then be taken accurately ; 

 but this does not occur short of two hours. This modification 

 has proven of great assistance in the manipulation of the Bab- 

 cock test for the determination of fat in cream and gives results 

 which compare very favorably with the gravimetric method and 

 the ordinary way of reading the fat column in the Babcock 

 bottle. Webster (15) has made a very exhaustive study of 

 the testing of fat in cream by the Babcock test. 



In the hands of a competent operator, the Babcock test gives 

 as reliable and accurate results as those obtained by the com- 

 plicated ether extraction method. 



Interpretation of specific gravity and fat. It is almost impos- 

 •sible to lay down any hard and fast rules concerning the inter- 

 pretation to be placed upon the specific gravity and fat content. 

 It may be said in general with reference to milk from herds in 

 normal condition that : 



1. High gravity with high fat content indicates a rich milk. 



2. High gravity with low fat content indicates either a 

 poor milk or that the milk has been skimmed. 



3. lyOw gravity with high fat content indicates ' ' top milk, ' ' 

 that is, the sample has been- taken from a quantity of milk 

 which has been allowed to stand some time previous to sam- 

 pling. 



4. lyow gravity, in connection with low fat content, indi- 

 cates a watered milk. 



Solids not fat. While it is true in many instances that the 

 fat per cent, and specific gravity are sufficient to enable the 

 inspector to judge of the quality of milk, at the same time it 

 is a simple matter to obtain the solids not fat by calculation. 

 Formulas for such calculation have been worked out by Bab- 

 cock, Fleischmann, Richmond and others. The one in general 

 use in this country is Babcock 's formula. 



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