164 ANIMAL COLOURING MATTERS. 



by that acid when in a concentrated state. Nitric acid converts 

 it into a bitter tasted matter. When the alcoholic solution is 

 mixed with sulphuric or nitric acid, it becomes green, and the 

 red colour is not restored by saturating the acid with an alkali. 

 Caustic potash dissolves it, assuming a red colour. From this 

 solution it is precipitated by the acids, without having been aci- 

 dified. The alcoholic solution loses its colour when alum is ad- 

 ded to it. If we add ammonia we obtain the colouring matter 

 united to alumina. The alcoholic solution is precipitated by 

 acetate of lead. The compound of the colouring matter and 

 oxide of lead is violet. The salts of iron, tin, copper, and mer- 

 cury have no action on it. 



The deep green shell of the cancri is reddened by acids, al- 

 kalies, by some salts, by putrefaction ; by the action of air and 

 oxygen, but it is not reddened by carbonic acid nor by hydro- 

 gen. Chlorine gas bleaches it. According to the analysis of 

 Goebel it is composed of, 



Carbon, 68-18 or 16 atoms carbon = 12 or percent. 68.08 

 Hydrogen, 9-24 or 13 atoms hydrogen = 1-625 9-22 



Oxygen, 22-58 or 4 atoms oxygen 4- 22-70 



100-00* 17-625 100- 



CHAPTER IV. 



OF PERISTERIN OR THE COLOURING MATTER OF PIGEON'S FEET, 



THIS r "1 colouring matter was examined by Goebel, who fou ~ d 

 it analogous to that of the craw-fish. It is easily separated by 

 digesting the pigeon's foot in water. The external cuticle by 

 this process is easily separated, so that the red pigment is quite 

 exposed, and may be easily separated by a fine knife. 



It is easily soluble in absolute ether and alcohol, forming a 

 fine carmine red solution. When the liquid is evaporated the 

 colouring matter remains as a fine shining red mass, having the 

 consistence of tallow. It is insoluble in water. On hot water it 

 swims in red drops ; but concretes into a solid mass when the li- 

 quid cools. It dissolves in caustic potash. The solution may be 

 * Scliweigger's Journ. xxxix, 429. 



