COLLIN. 209 



He gives as the formula for its constitution, C 48 H 41 Az 7 O 18 . 



If we calculate from this formula, we get, 



48 carbon, = 36- or per cent. 49-83 

 41 hydrogen, = 5-125 ... 7-12 

 74 azote, = 13-125 ... 18-14 

 18 oxygen, = 18-000 .,. 24-91 



72-25 100-00 



These numbers agree tolerably well with the analyses ; but 

 they do not quite agree with the formula of Mulder, which will 

 be given immediately. Scherer's formula, reduced to Mulder's 

 numbers, would be, C 15 H 11 Az 2 O 5 ; while Mulder's is, C 13 

 H 10 Az 2 O 5 ; thus differing from Scherer's by an atom of hydro- 

 gen. 



If we double the formula for collin we get, C 96 H 82 Az 15 O 36 

 If from these we subtract 2 protein, . C 96 H 72 Az 12 O 28 



There remains . . H 10 Az 3 O 8 



This is equal to 3 (Az H 3 ) + HO -f O 7 or three atoms of 

 ammonia, one atom of water, and eight of oxygen. 



Collin when dissolved in water and exposed to heat gradually 

 alters in its properties. Berzelius put a quantity of glue in a ge- 

 latinous state into a bottle, which was hermetically sealed. For six 

 successive days it was kept ten hours at the temperature of 176. 

 During the remaining fourteen hours it was left to cool. It assum- 

 ed the form of a jelly less and less firm every day. After the 

 sixth day, it did not gelatinize at all. It was limpid and slight- 

 ly brownish. On opening the bottle, a little air entered. When 

 the liquid was evaporated, it left a transparent brownish mass so- 

 luble in cold water.* A similar set of experiments made by M. 

 L. Gmelin had the same result. 



Gelatin, like all other constituents of animal bodies, is suscep- 

 tible of numerous shades of variations in its properties, and of 

 course is divisible into an indefinite number of species. Several 

 of these have been long known and manufactured for different 

 purposes : and many curious varieties have been pointed out by 

 Hatchett in his admirable Dissertations on Shell, Bone, and 

 Zoophytes, published in the Philosophical Transactions for 1797 

 and 1800. The most important species are the following: 



* Traite de Chimie, 



