1813.] Chemical Properties of Animal Fluids. 25 



tepid water with the disengagement of a small quantity of azotic 

 gas. The solution is reddish brown, and only semi-transparent. 

 A small part of the colouring matter remains undissolved, and 

 forms with the acid a compound of very sparing solubility. 



A solution of the colouring matter mixed with acetic acid does 

 not coagulate ; but when made to boil turns black and deposits 

 a very small quantity of its insoluble compound, without however 

 coagulating. 



The solution of the colouring matter in acetic acid is precipi- 

 tated both by alkalies and by alkaline prussiates. Ammonia 

 produces a dark brown precipitate, which, when well washed 

 and weighed, is found to be the colouring matter unaltered, and 

 again soluble in acetic acid. The solution after precipitation by 

 ammonia is yellow, and deposits by evaporation a quantity of 

 white matter, which is readily distinguished to be albumen, of 

 which it is impossible entirely to deprive the crassamentum. 



Prussiate of ammonia precipitates from the acetic solution a 

 mass of a blackish brown colour, resembling the precipitate by 

 pure ammonia. Both these precipitates, employed as pigments, 

 give the same shade of a dirty brown The prussic acid, there- 

 fore, appears to exert no action on the colouring matter of the 

 blood ; which should take place if the latter owed its colour to a 

 ferruginous salt. The solution of colouring matter in acetic acid 

 is precipitated by the mineral acids, and the precipitates have 

 precisely the same characters, excepting the colour, which is 

 brown, as those procured by the same methods from fibrin. 



4. Concentrated muriatic acid does not dissolve the colouring 

 matter, even when aided by digestion : a small quantity of azotic 

 gas is disengaged, and the acid assumes a yellow tint: alkalies, 

 however, produce in it hardly any precipitate. The undissolved 

 portion is a compound with excess of acid, which becomes 

 soluble in proportion as the superabundant acid is carried off. 

 The-neutial solution of colouring matter is brown, and has the 

 same properties as that formed by acetic acid. The colouring 

 matter boiled for a long time with muriatic acid, suffers a com- 

 mencement of decomposition : some iron is taken up by the acid, 

 and the undissolved portion is no longer soluble even by repeated 

 washing, although in this state it it lain- a portion of acid, of 

 which the water cannot deprive it. 



5. The nitric add products the same effects in the colouring 

 matter as on fibrin ; the only distinction being in the colour, 

 which in the former is invariably black. 



(j. Caustic ammonia dissolves, the colouring matter assuming 

 a very deep brown colour. A precipitate is thrown down by 

 acids, but not by tin; alkaline prossiatPS. The precipitate formed 

 by acetic acid is again soluble, but only by an excess of acid. 



