30 



CASEIN. 



INSOLUBLE PREPARATION OF CASEIN. 



Desgeorge and Lebriel, in making a supple, insoluble pre- 

 paration of casein and other albuminoids, endeavour to over- 

 come the defects of existing methods, using metallic oxides, 

 acids, etc., by utilising the chemical activity of the electric 

 current to increase the absorption of these oxides or acids by 

 the casein, and consequently improve their effect. The casein 

 is attached to the positive electrode of an electrolytic cell, 

 charged with a bath consisting of water 1,000 parts, sulphuric 

 acid 150 parts, and tannic acid 500 parts, the negative electrode 

 being formed of a plate insoluble in the bath. The sulphuric 

 acid supplies the casein with the sulphur, enabling it to absorb 

 the oxygen of the bath, whilst the tannic acid increases the 

 insolubility of the product and renders it supple and non- 

 putrefactive. The current decomposes the bath, liberating 

 hydrogen at the negative electrode, whilst the oxygen of all 

 the acids present flows to the positive pole, where it is absorbed 

 by the casein. Harder products may be obtained by replacing 

 100 parts of the sulphuric acid in the bath by 50 parts of 

 phosphoric or other acid. According to the uses for which 

 the casein is intended, the tannic acid may be replaced by 

 other insolubilising agents. 



