112 CASEIN. 



methods of preparation adopted, it is impossible to give 

 any minimum quantity of alkali that will cause separation 

 in all cases ; nevertheless, a preliminary test will furnish the 

 necessary information. 



The clear casein solutions prepared in the foregoing- 

 manner can be treated sifter removal of the sediment in 

 the same way as the turbid solutions. For instance, the 

 casein can be precipitated by an acid, and used in place of 

 ordinary casein, or the precipitate may be dried whereby it 

 becomes perfectly transparent and worked up into artificial 

 amber, jet, etc. 



The claim advanced for the method is for the preparation 

 of transparent masses from casein by treating casein, either 

 dissolved or suspended in water, with such an excess of 

 caustic alkali as to precipitate the opaque particles, whilst 

 the casein is retained in clear solution, whence, after the 

 sediment has been removed, the casein can be precipitated 

 and worked up in any suitable way. 



In the additional patent (141,309: 5th March, 1902) it is 

 stated that the caustic alkali originally prescribed can be 

 partly or wholly replaced by alkali carbonates, further ex- 

 periments having shown that these carbonates have a clari- 

 fying effect when added in far larger quantity than is needed 

 to dissolve free casein. The resulting decomposition is not 

 so thoroughgoing as when caustic alkali is used, the latter 

 acting also on the sulphur compounds present in the casein 

 solution, and causing discoloration (yellow stain) of the 

 clarified solution or of the precipitated casein, unless the 

 operation be performed with extreme care. Hence when 

 a colourless product is specially desired, the caustic alkalies 

 may be advantageously replaced, wholly or in part, by their 

 carbonates. 



For example, 55 gallons of milk, separated from all im- 

 purities as far as could be effected by repeated centrifugal- 





