346 



CHAPTEE XV. 

 THE ANALYSIS OF MILK AND MILK PRODUCTS. 



FOR a detailed account of the methods employed in making 

 a complete analysis of these substances the reader must con- 

 sult a manual on analysis. Only a few of the more important 

 determinations in the analysis of milk, butter, and cheese will 

 be described here. 



MILK. For many purposes an examination of milk directed 

 to the estimation of the percentages of total solids and fat and 

 the absence or presence of preservatives is sufficient. 



The Amount of Fat, as already stated, is subject to 

 greater variation than that of the other constituents, and from 

 a practical standpoint is usually considered the most impor- 

 tant criterion of the value of a sample. 



Of many methods which have been described the following 

 are among the most reliable and best known : 



1. Adams's paper -coil method. In this process 5 c.c. of the 

 milk are allowed to run from a pipette upon a strip of filter 

 paper (from which all matter soluble in ether has previously 

 been removed) about 22 inches long by 2 inches wide. The 

 paper is then dried by holding it near a fire, care being taken 

 not to scorch it. It is then rolled into a coil round a short 

 piece of wide glass tubing sealed up at each end (containing a 

 little mercury so that it may not float in ether)" and introduced 

 into a Soxhlet extractor, in which it is repeatedly treated with 

 ether, the ether with the dissolved fat being received in a 

 wide-mouthed small flask, previously weighed. After eight or 

 ten siphonings the flask is removed from the extractor, the 

 ether distilled off into another condenser, the flask dried in the 

 steam bath for an hour or so, cooled, and weighed. The 



* This device greatly hastens the extraction, by diminishing the amount of ether 

 required to till the apparatus. 



