CASEIN ADHESIVES AND PUTTIES. 85 



to their tendency to absorb moisture, to decompose or to 



putrefy. 



CASEIN ADHESIVE. 



A solution of tannin or decoction of gallnuts is treated 

 with a gradual addition of clear lime water so long as a pre- 

 cipitate continues to form, and until the supernatant liquid 

 turns red litmus paper blue. The. precipitate, consisting of 

 calcium tannate, is separated from the liquid, dried, and mixed, 

 ground and sifted with casein, the usual proportions being 

 about 90 parts of casein to 10 of tannate. For use the 

 powder is mixed with water, with which it forms a viscous 

 adhesive, which, when perfectly dry, is very hard and tough, 

 being also completely insoluble in water, petroleum, and oils, 

 and therefore suitable for a variety of purposes. 



HALL'S CASEIN GLUE. 



A powerful fireproof glue is obtained, according to W. A. 

 Hall, by mixing 



50 to 60 parts by weight of dry casein, 



20 ,, ,, sodium phosphate, 



10 ,, ,, sodium sulphite, and 



20 to 30 ,, ,, dry lime, slaked or burned. 



In another of Hall's recipes an adhesive is prepared by 

 modifying starch under the influence of high temperatures, 

 and stirring this product up with casein until the whole is 

 nearly or quite absorbed by the particles of casein, a dissolved 

 alkali being added during stirring. By the intimate admix- 

 ture of the several ingredients a very useful adhesive is 

 obtained. 



Still another process consists in combining certain pro- 

 portions of casein, ammonia and formaldehyde to form a 

 mass suitable for sizing paper, straw, etc. 



WATERPROOF GLUE. 



A waterproof glue or putty is obtained by mixing an 

 albuminoid substance like casein, albumen, etc., with a 



