CASEIN : ITS OEIGIN, PEEPAEATION AND PBOPEKTIES. 11 



after the removal of the whey-butter and whey-cheese. 

 The whey proper is used as a beverage, in baking, for feed- 

 ing pigs, and also for the recovery of milk sugar (for alcohol 

 or vinegar), and the preparation of fermented liquors, such 

 as whey- champagne and whey-punch. The two classes of 

 whey are accredited by Fleischmann with the following 

 composition : 



Cheese-milk. Whey. 



Water ...... 93-15 93-31 



Fat 0-35 0-10 



Proteids 1-00 0-27 



Milk sugar and lactic acid . . 4-90 5 - 05 



Ash . 0-60 0-47 



The casein separated from milk is termed " curd," and 

 is subjected to further treatment, mainly with a view to re- 

 ducing its water content when cheesemaking is in question. 

 If, on the other hand, it is to be used for technical purposes, 

 it must be thoroughly freed from the residual whey by re- 

 peated washings with hot or cold water, and finally more or 

 less thoroughly pressed (according to the purpose in view) 

 to expel the water. 



The spontaneous and artificial coagulation of milk has 

 been dealt with by Prof. Pokorny (Chemiker Zeitung) as fol- 

 lows. It is known that milk left to stand curdles and turns 

 sour spontaneously, as the result of the formation of acid. 

 This cause is demonstrated by the fact that fresh milk can 

 be curdled by the addition of lactic or some other acid, the 

 same result being produced by acid salts. Fresh milk treated 

 with acetic acid is coagulated almost instantaneously when 

 the amount of acid used is large, though with small quantities 

 of acid some little time elapses before the flakes of casein 

 can be observed adhering to the walls of the test glass on 

 shaking. Sulphuric acid, as a strong mineral acid, coagulates 

 milk at once when added in the proportion of 5 per cent, (e.g., 

 10 cc. of 10 per cent, sulphuric acid to 20 cc. of milk). 



