VARIOUS METHODS OF PREPARING CASEIN. 25 



and non-mucinous form, but possesses the advantage that, 

 owing to the ready solubility of its lime salt, the casein is 

 obtained almost free from ash at the first precipitation. At 

 the same time the casein is poorer in germs than when 

 acetic acid or lactic acid is used, and the inverting action on 

 the milk sugar is smaller. Crude ethylsulphuric acid is 

 used, this being prepared by rapidly mixing equal volumes 

 of concentrated sulphuric acid and strong alcohol, and 

 leaving the mixture to stand for several hours in a warm 

 place. 



To obtain soluble casein in the dry commercial state, the 

 curd is thrown down from the milk, washed to remove whey 

 and any excess of precipitant, dried at a moderate tempera- 

 ture to preclude risk of burning, granulated, and allowed to 

 absorb a small quantity of dissolved alkali by rapidly stirring 

 the two together. Finally, the granulated alkaline product 

 is dried in accordance with American patent 664,318. 



Szekely's patent (German patent 126,423) relates to 

 the decomposition of milk into casein and whey by means of 

 carbonic acid. For this purpose, sweet new milk, cream, 

 skim milk or buttermilk, is placed in a closed vessel, warmed 

 somewhat above 86 F., and a sufficient amount of carbonic 

 acid gas is forced in under pressure to precipitate the whole 

 of the casein when well shaken or stirred. 



To neutralise the differences in skim milk in the separa- 

 tion of casein, C. H. Bellamy of Philadelphia adds to the 

 casein in the preparation of casein glue an alkali arsenate 

 (e.g., Na 2 HAsO 4 ). This addition is stated to increase the 

 adhesive power of the glue, preserve it from putrefaction, 

 and form a kind of mordant, acting as a binder between the 

 paper, the casein glue and any added colouring matter. 



Pure casein, free from ash, is obtained by precipitating 

 1,000 parts of cold milk with 2 -9 parts of acetic acid which 

 leaves the bulk of the lactalbumen in solution. The filtered 



