24 CASEIN. 



On the other hand, if the liquid is cloudy, more ammonia 

 should be added, with stirring, until the solution becomes clear. 

 The finished solution is then run into glass bottles at once 

 and hermetically closed down. After prolonged standing, a 

 small deposit of undissolved casein may settle down in the 

 bottles. This clarified solution when poured out on glass, dries to 

 a hard, colourless and insoluble mass, of high lustre, on which 

 account it serves as an excellent lacquer. Printing colours that 

 are not sensitive to the action of ammonia may be mixed and 

 printed with the liquid, the casein becoming insoluble and 

 thus fixing the colour on the fabric. 



A patent on the following lines, for preparing fat-free 

 casein from skim milk, was taken out by Mierisch and 

 Dr. Eberhardt. Ordinary "separated" milk contains 0'2 to 

 0'3 per cent, of fat, and if used for the preparation of casein, 

 gives a product containing 6 to 8 per cent, of fat. The 

 usual method of getting rid of this fat is by extraction with 

 fat solvents or repeated solution in alkalies and reprecipitation 

 by acids ; but in the patented process the skim milk is 

 mixed with alkali, then warmed and centrifugalised to expel 

 the fat, and afterwards treated with acid, in the usual 

 manner, to throw down the casein. For example, 100 gallons 

 of skim milk are mixed with a solution of 2 to 4 Ib. of 

 caustic soda, the whole being warmed to 100 to 112 F. 

 and put through the centrifugal separator until no more fat 

 comes away. The casein is next thrown down with dilute 

 sulphuric acid and collected, washed, pressed and, if neces- 

 sary, dried. The product will satisfy practical requirements 

 in respect of freedom from fat. 



Riegel's method of precipitating casein with ethylsul- 

 phuric acid is intended to replace the use of acetic acid, 

 lactic acid and sulphuric acid for this purpose. The acid in 

 question shares with sulphuric and acetic acids the property 

 of precipitating the casein in an undecomposed, compact 



