182 THE ANALYSIS OF MILK. 



Table X, page 181, based upon this formula and taken from 

 Farrington and Woll, shows the solids not fat and spindle 

 readings of 26 to 36. The spindle readings refer to the last 

 two figures of the specific gravity ; for instance, if the specific 

 gravity were 1.032, this would be represented in the table by 

 spindle reading 32. 



It is thus seen that by adding the fat and solids not fat the 

 total solids of the milk are obtained. In nearly all cases the 

 difference between the actual determination of the solids not 

 fat and the figure obtained by calculation does not differ mater- 

 ially. The inspector consequently by merely determining the 

 fat and the gravity will be in a position to judge whether or 

 no milk under examination is or is not up to the required 

 standard for pure milk. 



Preliminary tests of milk. It is often desirable to make pre- 

 liminary tests of milk with reference to its quality, for which 

 there are to be obtained several devices. These are well 

 described by Wing (6), who also gives a very interesting sum- 

 mary of the development of the tests for fat previous to the 

 invention of the Babcock test. 



Acidity of milk. This is a point which should receive more 

 attention from the health officer than it ordinarily does. Milk 

 fresh from the cow will often show an amphoteric reaction 

 but soon afterwards it will show an acid reaction and this acid- 

 ity will vary greatly, depending entirely upon how the milk 

 has been handled. The Committee on Chemical Standards of 

 the American Association of Medical Milk Commissions rec- 

 ommended that the maximum acidity of milk allowed should 

 be 0.18 % calculated as lactic acid. The writer considers this 

 to be a very generous standard. 



The acidity of milk should be determined at times but not 

 as a routine procedure. This may very easily be done by the 

 use of the Farrington alkaline tablet test as fully described in 

 Farrington and Woll (6). The test is very simple and does 

 not require an expensive outlay for apparatus, but it must be 

 emphasized that only distilled water or a clean, non-alkaline 

 soft water should be used for dissolving the tablets. 



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