SUNDRY APPLICATIONS OF CASEIN. 139 



Paper pulp was mixed with dissolved casein for twenty 

 minutes, and to the mixture was added a solution of alum 

 as in resin sizing followed by diluted sulphuric acid until 

 a faintly acid reaction was produced. In the trials the casein 

 was poured on at the same time as the resin soap, or else 

 .after the latter had been precipitated by aluminium sulphate. 

 In general the addition of casein was found to have a favour- 

 able influence on the firmness of the paper and on the amount 

 of size consumed. Casein can also be used for this purpose 

 by itself, and furnishes a coating that will make the paper 

 easier to roll up. 



WATERPROOFING PAPER. 



This process is devised for making paper and fabrics 

 waterproof to such an extent that they will stand protracted 

 exposure to the influence of moisture without losing their 

 Koftness and elasticity. At the same time they are made 

 superior to paper or fabric coated with caoutchouc, both in 

 point of durability and freedom from smell. 



The principal features of the process are that the paper or 

 other material to be waterproofed receives two waterproof 

 coatings in succession, the first consisting of a specially pre- 

 pared solution of glue or casein (or mixture of both), which, 

 when warmed and treated with certain additions, remains 

 permanently supple and elastic. 



In carrying out the process, glue or casein is dissolved in 

 water or other suitable solvent and treated with an addition 

 of sodium tungstate to improve the tenacity (if desired), the 

 albuminous substances being then precipitated by tannin or 

 other suitable precipitant as a viscid insoluble mass. 



This mass, which is elastic and plastic while moist, be- 

 comes very hard and brittle on drying, so that it would be 

 entirely unsuitable for the purpose in view were it not cor- 

 rected by melting it in a pan (preferably before it has set) 



