18 BUTTER-MAKING. 



small amount of alcohol, formic, acetic, and succinic acids are 

 said to be normal accompanying by-products also. These 

 by-products may also partially result from the breaking down 

 of some of the other milk components. 



As milk-sugar is in perfect solution, it follows the water 

 of milk, and in cheese-making nearly all of it passes into the 

 whey. Commercially and chemically it is prepared from 

 whey. It is a white, not very sweet powder, and is used for 

 medicinal purposes to dilute pure, powerful drugs. It is also 

 used extensively in the preparation of modified milk. 



Ash. — The ash of milk is present in very small quantities, 

 and when viewed from such a standpoint it may first seem 

 to be of small importance. On account of the effect of the 

 mineral constituents upon the properties of milk, it is one 

 of the most important components of the milk. It consists 

 partly in solution, and partly in suspension. Babcock main- 

 tains that about one-third of the usual ash constituents is in 

 suspension, and that they consist chiefly of lime phosphate. 



All of the minerals in milk consist chiefly of potash, lime, 

 soda, magnesia, and iron, combined with phosphoric, hydro- 

 chloric, sulphuric, and carbonic acid. Calcium phosphate 

 constitutes about one-half of all the ash constituents. They 

 are named above, in order, according to the extent in which 

 they occur in milk. 



Gases of Milk. — These do not normally exist in milk to 

 such an extent as to enable chemists to determine them quan- 

 titatively, but they are of great importance, owing to the 

 effect they have upon the quality of the milk, viewing it in 

 the commercial sense. 



Gases in milk may be divided into two classes according to 

 their origin; namely, (1) those imparted to milk before milk- 

 ing and (2) those which are formed and absorbed in milk 

 later. 



(1) When freshly drawn milk has a characteristic cowy 

 smell, which seems to be normal to all fresh milk. These 

 gases are very volatile, and by cooling and aerating milk (differ- 



