ANIMAL AMIDES. 



chondrin ;* and in 1841 a set of experiments, serving still farther 

 to characterize it, was published by M. Vogel, Jun.f It may be 

 distinguished by the following properties. 



1. It is less brown than collin. 



2. It is precipitated completely from its aqueous solution by 

 acetic acid, The precipitate is in very fine flocks, and gives the 

 liquid a white colour. It is not redissolved by an excess of acid ; 

 but if we neutralize the acid with carbonate of potash, the preci- 

 pitate is again dissolved. Acetic acid is incapable of throwing 

 down collin from its aqueous solution, or of rendering that solu- 

 tion muddy. 



Vogel found that a similar precipitate was occasioned by most 

 of the mineral acids and organic acids tried. To precipitate by 

 sulphuric acid, we must employ a very small quantity of the acid. 

 If into half-an-ounce of the solution of chondrin we dip a rod 

 moistened with sulphuric acid diluted with six times its weight 

 of water, a precipitate falls. But the addition of a drop of the 

 acid redissolves the precipitate. Sulphurous acid precipitates 

 chondrin, and the precipitate is not redissolved by adding an ex- 

 cess of the acid. Nitric acid precipitates and readily dissolves 

 chondrin. This is the case also with phosphoric acid, but pyro- 

 phosphoric acid throws it down and an excess of the acid does 

 not redissolve the precipitate. 



Phosphorous acid and fluoric acid precipitate chondrin, and the 

 precipitate is redissolved by an excess of the acids. A current 

 of carbonic acid long enough continued throws down the whole 

 of the chondrin, and does not again redissolve it. The precipi- 

 tate is a carbonate of chondrin. 



The precipitates by arsenic, tartaric, oxalic, and citric acids 

 are not redissolved by an excess of these acids. 



3. The aqueous solution of chondrin is precipitated by alum, 

 sulphate of alumina, acetate of lead, and persulphate of iron. 

 These reagents have no action on the aqueous solution of collin. 

 Alum or sulphate of alumina occasions the greatest precipitate. 

 It consists of white compact flocks, which speedily coalesce into 

 balls. The precipitate by acetate of lead or persulphate of iron 

 is in larger or smaller flocks, according as the liquid is more or 

 less concentrated. The addition of a small quantity of alum or 

 sulphate of alumina is sufficient to precipitate the whole chondrin 



* Poggendoi-fs Annalen, xxxviii. 304. f Jour, de Pharm. xxxvii. 494. 



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