14 MODERN [METHODS OF TESTING MILK 



inorganic bodies. The ash represents in amount, 

 therefore, more than the so-called mineral constitu- 

 ents of milk and less than the salts of milk. While 

 the ash in milk amounts to about 0.7 per cent., the 

 amount of salts probably approximates 0.9 per cent. 

 A portion of the salts of milk is in solution, including 

 such compounds as calcium citrate, sodium chloride, 

 potassium acid phosphate, etc., while a portion (tri- 

 calcium phosphate) appears to be in suspension in 

 the form of very finely divided particles. 



THE GASES OF MILK 



Alilk contains more or less oxygen and nitrogen, 

 these gases being carried into it mechanically from 

 the air in the process of milking. It contains also, 

 when freshly drawn, carbon dioxide, already present 

 in the udder milk, there being probably between 3 and 

 4 per cent, by volume, a portion of which escapes at 

 once while being drawn from the udder under usual 

 conditions. 



GENERAL SUMMARY 



Milk contains water, fat, casein, albumin, sugar, 

 salts, carbon dioxide and some other constituents in 

 small quantities. The fat and casein and some of the 

 salts are in suspension and not in solution, while al- 

 bumin, sugar and the larger portion of the salts are 

 held in solution by the water. 



As a matter of convenience, the compounds of milk 

 are divided into certain arbitrary groups. By one 

 system of division, the compounds of milk are ar- 

 ranged in two classes: — (i) JFafcr, and (2) milk- 

 solids (or total solids), this second class including 



