SUNDRY APPLICATIONS OF CASEIN. 165 



Crushed casein is stirred up well with water so as to be 

 thoroughly permeated therewith and to form a thin pap. 

 The surplus water is then drained off, the product dried and 

 allowed to shrink. 



EBERHARDT AND MIERISCH'S SOLUBLE CASEIN. 



A perfectly soluble, fat-free casein can be obtained by 

 centrifugalising skim milk at about 104 to 113 F., treating 

 it with caustic potash or soda, passing it through the sepa- 

 rator again until no more fat is eliminated, and then precipi- 

 tating the casein by means of an acid, e.g., dilute sulphuric 

 acid, or better still, by an acid forming soluble lime salts, 

 such as ethylsulphuric acid, lactic acid or acetic acid. The 

 precipitate is washed and dissolved in a solution of alkali. 

 The entire process is then repeated several times over, the 

 casein being finally dissolved in ammonia, treated with benzine 

 or chloroform to extract fat, and then filtered through dia- 

 tomaceous earth or the like. The resulting solution may 

 be used per se or treated with an acid to throw down the 

 casein. 



WATERPROOF CASEIN. 



When a circa 5 per cent, solution of sodium caseate is 

 mixed with formaldehyde no coagulation occurs, the solution 

 remaining clear and fluid for a long time. If this solution 

 be poured out on a sheet of glass, zinc, paper, etc., or left to 

 dry, an insoluble film of casein is obtained. 



Another way is to prepare a solution containing about 

 100 parts of casein and 1| parts of caustic soda in 1,000 of 

 water, to which 15 parts of a 40 per cent, solution of formal- 

 dehyde are then added. This mixture, which remains per- 

 fectly clear, is next poured out on a sheet of glass, zinc or 

 paper and evaporated or dried. In order to produce a water- 

 proof film from ammonium caseate, a solution is prepared 



