CHEMISTRY OF COWS MILK 3 



Total solids. — Under the general term of total solids 

 or niilk-soUds, we indicate the constituents of the milk 

 other than water (and gases). The per cent, of water 

 in milk subtracted from loo gives the percentage of 

 milk-solids, which include fat, proteids, milk-sugar 

 and salts or ash. The amount of solids in milk varies 

 with the same conditions that affect the percentage 

 of water in milk, but, of course, in just the reverse 

 manner. Most states orescribe a legal standard for 

 milk-solids, usually 12 per cent., and milk containing 

 less than the legal amount is regarded as adulterated. 



MILK-FAT 



The composition of milk-fat. — Milk-fat, also called 

 huttcr-fat, is not a single chemical compound, but is 

 a somewhat variable mixture of several different com- 

 pounds called glycerides. Each glyceride is formed by 

 the chemical union of glycerin as a base with some 

 acid or acids of a particular kind. These glycerin-acid 

 compounds, or glycerides, of milk-fat contain about 

 ten different acids, some being present in small propor- 

 tions. The four following acids enter most largely 

 into the composition of milk-fat, in the form of their 

 combinations with glycerin: Palmitic acid, oleic acid, 

 myristic acid and butyric acid. The compounds, or 

 glycerides, formed by the combination of glycerin and 

 the acids, have special names derived from the acids; 

 thus, we have palmitin (glycerin combined with palm- 

 itic acid), butyrin (glycerin combined with butyric 

 acid), olein, etc. ]\Iilk-fat contains, on an average, 

 about 40 per cent, of palmitin, 34 per cent, of olein, 

 10 per cent, of myristin, 6 per cent, of butyrin, and 



