GELATINE AND GLYCERINE 229 



the original fibrous structure is retained. There is a 

 limited demand for this material for clarifying purposes by 

 brewers, wine merchants and cooks. 



Leather waste may sometimes be used to make a low- 

 grade glue. Vegetable-tanned leather offers much difficulty 

 unless very lightly and recently tanned. The tannage must 

 be stripped by drumming with weak alkalies, e.g. borax, 

 sodium sulphite, or weak soda. Chrome leather may be 

 stripped easily and completely by Rochelle salt and other salts 

 of hydroxy acids (Procter and Wilson), and also by ammonia 

 acetate, oxalate and similar salts (Bennett), also by certain 

 organic acids (Lamb). Processes are patented by which 

 chrome leather is digested with lime to make glue, the 

 chromium hydrate being insolubilized. Viscous and 

 tenacious substances are also obtained from some vegetable 

 matters and are called " glue." 



REFERENCES. 



" Glue and Glue Testing," S. Rideal, D.Sc., 2nd ed. ; Skin Gelatine and 

 Glue, pp. 25-48 ; Bone Gelatine and Glue, pp. 59-66. 



" Gelatine, Glue and their Allied Products," T. Lambert, pp. 11-52. 

 " Encyclopedic chimique," Fremy, tome x. 



