CASEIN ADHESIVES AND PUTTIES. 83 



is capable of resisting moisture, by treating dry casein with a 

 dilute solution of borax, or with sufficient ammonia to pro- 

 duce a faintly alkaline reaction. This preparation may be 

 used or mixed with liquid starch in any proportion. 



CROSSPIETSCH'S ADHESIVE. 



A mixture of casein, castor oil and linseed oil, thickened 

 by heat, is treated with alum, sugar-candy and dextrin, and 

 heated over again until a homogeneous pap is formed, which 

 is then treated with water-glass. 



JEROMIN'S CASEIN ADHESIVE. 



According to German patent 154,289, lime, water-glass 

 and casein are mixed together and applied to the wood to be 

 glued, left to dry and afterwards heated, with application of 

 pressure, to make a waterproof joint. This method of mix- 

 ing the three ingredients direct has the disadvantage that the 

 casein is not fully dissociated ; and it is found that the adhe- 

 sive is more powerful when the casein has been treated with 

 lime water before mixing it with the water-glass and lime. 



The method of treating casein with alkalies is not new, 

 and a process of this kind is described in German patent 

 116,355, though the purpose of the treatment in that instance 

 is a different one, namely, the production of a viscous solu- 

 tion of casein. With this object the casein is treated with 

 sufficient alkali to produce a faintly alkaline reaction, that is 

 to say, the amount of alkali added is in excess of that neces- 

 sary to form the neutral caseate. This implies that the casein 

 passes into solution and is no longer in the colloidal form, 

 which solution, however, is incapable of fulfilling the purpose 

 for which it is intended, namely, that of an adhesive and 

 tiller. To overcome this drawback the casein is reconverted 

 into the colloidal state by means of tannin, so that the final 

 product is improved in respect of adhesive and filling power. 



