MILK. 



383 



Cow's milk always shows slight alkaline reaction ; its density is 

 about 1.03. According to M. Haidlen, it contains no salt formed 

 by an organic acid, no lactates, and the alkali is in combination with 

 caseum, the solution of which it assists. It may contain about a 

 half per cent, of ash, the several constituents of which appear to be 

 very stable, though their proportions vary greatly. In 100 parts 

 of milk, taken from two different cows, Haidlen found the following 

 salts : 



Phosphate of lime 0.231 0.344 



Phosphate of magnesia 0.042 0.064 



Phosphate of iron 0.007 0.007 



Chloride of potassium 0.144 0.183 



Chloride of sodium 0.024 0.034 



Soda.... 0.042 0.045 



0.490 0.677 



As cow's milk is that which is by far the most directly interesting 

 to agriculture, I shall enter somewhat particularly into its history ; 

 having, however, already spoken of caseum, its distinguishing con- 

 stituent, and albumen, I shall here confine myself to the subject of 

 the sugar and the oil or butter. 



Sugar of milk is prepared for commercial purposes, in countriea 

 or districts where cheese-making is carried on to a great extent, 

 and the quantity of whey at command is very large. In some Can- 

 tons of Switzerland, sugar of milk is obtained by simply evaporating 

 whey properly clarified, to the consistence of sirup, which deposites 

 the sugar in the crystalline form as it cools. This first produce is 

 brown, and contaminated with various impurities, from which it is 

 freed by repeated solutions and crystallizations. It then becomes 

 colorless, transparent, and nearly tasteless, feeling gritty between 

 the teeth, and having only an obscure sweet taste. Ii requires from 

 8 to 9 parts of cold water to dissolve it ; in hot water it is more 

 soluble. According to Proust, it consists of : 



