402 DERIVATIVES OF THE PROTEIN-COMPOUNDS. 



the form of the tissue from which it is prepared ; it is insoluble in 

 water, acetic acid, and alkalies, but dissolves in concentrated nitric 

 and hydrochloric acids without communicating any colour to those 

 fluids ; after neutralisation with ammonia, tannic acid throws down 

 a precipitate from these solutions. In concentrated sulphuric acid 

 it swells up and becomes dissolved without communicating any 

 change of colour to the acid ; it gradually however again separates 

 as a black mass, while acetic acid and acetate of ammonia remain 

 in solution ; no sulphurous or formic acid is however formed. It 

 is not decomposed by the most concentrated solution of potash, 

 even at a boiling heat ; heated to 280 with water in closed tubes, 

 it becomes brown and brittle without undergoing any change of 

 structure that can be detected by the microscope. There are two 

 points worthy of notice in connexion with the dry distillation of 

 this substance ; it does not fuse, but leaves a charcoal which on 

 microscopic investigation always exhibits the form of the original 

 tissue ; and further, notwithstanding that it contains nitrogen, it 

 yields acid products of distillation in which not only water and 

 acetic acid are found, but also acetate of ammonia and a little 

 empyreumatic oil. 



Composition. This body has been analysed by Lassaigne* and 

 Payen ? f and has been most carefully studied by C. Schmidt^. 

 Payen found much too little nitrogen. The results of various 

 analyses and experiments which I have made with chitin exactly 

 correspond with those of Schmidt. The following are the results 

 of our analyses. 



Schmidt. Lehmann. 



Carbon 46-64 46734 



Hydrogen 6-60 6*594 



Nitrogen 6'56 6-493 



Oxygen 40-20 40-179 



100-00 100-000 



Schmidt regards C 17 H 14 NO H as the simplest formula express- 

 ing this composition. He directs especial attention to the peculiar 

 relations of this substance when acted upon by heat and by acids, and 

 arrives at the very interesting result that this body which so closely 



* Journ. de Chim. meU T. 9, p. 379. 

 t Compt. rend. T. 17, p. 227- 



% Zur vergleichend. Physiol. der wirbellos. Thiere, 1845, S. 32-C9 [or Tay- 

 lor's Scientific Memoirs, vol. 5, pp. 14-28. o. E. D.] 

 Jahresber. d. ges. Med. 1844, S. 7. 



