400 DERIVATIVES OF THE PROTEIN-COMPOUNDS. 



into a substance which does not gelatinise but which glues very well, 

 and which, moreover, resembles chondrin in its behaviour to acetic 

 acid and metallic salts, but is not precipitated by the salts of the 

 oxides of platinum, silver, and gold ; and, finally, that ossified 

 fish-cartilage when boiled, yields a non-gelatinising fluid which is 

 precipitated by tannic acid, but not by acetic acid and the salts of 

 alumina, and consequently, approximates in its character to glutin. 



Origin. In our observations on glutin we pointed out that we 

 are still perfectly ignorant of the mode of origin of chondrin. The 

 experiments of Miiller render it highly probable that glutin is 

 formed from chondrin. But how ? This must be decided by future 

 researches. 



Uses. The animal tissues which yield chondrin are of the same 

 use through their physical properties as those which yield glutin ; 

 their most important character being their elasticity. 



FIBROIN. 

 Chemical Relations. 



Properties. It is a white, amorphous mass, devoid of odour 

 or taste, insoluble in water, alcohol, and ether, but dissolving in 

 concentrated sulphuric, nitric, and hydrochloric acids, from which 

 solutions, if diluted with water, it is precipitated by tannic acid ; 

 it is insoluble in acetic acid and in ammonia ; it dissolves in a con- 

 centrated solution of potash but at the same time undergoes decom- 

 position. This substance becomes decomposed, when heated ; 

 developing ammonia and empyreumatic vapours. 



Composition. This body was discovered and has been analysed 

 by Mulder* ; it consists (taking the mean of four of his analyses) of: 



Carbon 48-61 



Hydrogen 6*50 



Nitrogen' 17-34 



Oxygen 27*55 



100-00 



From these numbers Mulder calculated the formula 

 C 39 H 31 N 6 O 17 according to which fibroin may be regarded as 3 

 atoms of glutin which have assimilated 1 atom of oxygen and 1 

 atom of water, for 3(C 13 H 10 N 2 O 5 ) + HO + O=C 39 H 31 N 6 O 17 . 

 Mulder and Croockewitf moreover found that the common sponge 



* Natuur en Scheik. Archief. D. 3, p. 93, D. 5, p. 281. 

 t Scheik. Onderz. D. 2, p. 1. 



