GELATINE AND GLYCERINE 221 



the greater bulk of the raw material for skin gelatine, which is 

 thus derived principally from ox hides, but sheep and goat 

 skin pieces have also an important place. The skins of 

 other animals, such as dogs, cats, hares, rabbits, not usually 

 made into leather can also be depilated and used for making 

 skin gelatine and glue. Horse hide fleshings and pieces are 

 sometimes used, but are notorious for the poor quality of 

 their product. They seem to contain less a gelatin. All 

 these materials are of course readily putrescible and must 

 be put " into work " without much loss of time. When 

 it is impossible to convey them from the tannery to the 

 gelatine factory quickly enough, e.g. foreign material, the 

 "glue stock " is dried out completely and sold in that con- 

 dition. In the manufacture of pickers from limed pelt there 

 is some superfluous material, and this is cut into shavings 

 and dried. This " picker waste " also forms a useful source 

 of raw material. Skin gelatine material is not very strong in 

 gelatine-substance. The fleshings, pieces, etc., contain much 

 water, even up to 80 per cent. This, however, is very 

 variable, and only a practical test or a hide substance deter- 

 mination can indicate the commercial value of any particular 

 material. This value, moreover, is determined not only by 

 the yield and quality of the gelatine which can be obtained, 

 but also by the yield of grease, the valuable bye-product. 



The preliminary treatment of material for skin gelatine 

 consists essentially of liming and of washing. The object 

 of each process is to purify. Liming has much the same 

 action on hide pieces, etc., as on hides, and indeed the 

 liming treatment is somewhat superfluous on cuttings from 

 well-limed hides. The material is plumped up and the 

 partially hydrolyzed products are taken into solution. Lime 

 also acts as mild antiseptic, stops any putrefaction and 

 liberates ammonia formed by fermentation in transit to 

 the factory. When plumping is particularly wanted (as in 

 wetting in dry stock) caustic soda is sometimes used as an 

 assistant (cf. dried hides, p. 18). Sodium sulphide has 

 also been used for this purpose. The liming is in brick pits, 

 an excess of undissolved lime being always used. It is 



