116 MR. EDWARD SCHUNCK ON SOME 



it ought to have done, supposing it to have been perfectly 

 pure. In consequence of the amorphous nature of the 

 product it is difficult to determine whether Indian and 

 American cotton contain two distinct colouring-matters, 

 both easily soluble in alcohol and having the same general 

 physical properties, or whether in one or both cases the 

 specimens submitted to analysis, though essentially the 

 same substance, were not chemically pure. It is, I believe, 

 a difficult task to obtain, in a state of purity, an uncrystal- 

 lizable resinous body having few characteristic properties ; 

 and the results arrived at by examining the composition of 

 such bodies are seldom satisfactory. 



Colouring-Matter B. 



This substance is deposited from its solution in boiling 

 alcohol as a brovrn powder, which, after being filtered ofi" 

 and dried, forms coherent masses of a colour varying from 

 light to dark brown, which may be easily broken, the 

 fracture being dull and earthy. In boiling water it softens 

 and yields a dark-brown cake. It is almost insolable in 

 cold alcohol, and when it has once been dried it dissolves 

 with great difficulty even in boiling alcohol. By this pro- 

 perty it may easily be distinguished from the other colour- 

 ing-matter, which it closely resembles in most other re- 

 spects. When heated on platinum, it burns without pre- 

 viously melting ; and the carbonaceous residue burns away 

 with difficulty, leaving at last a bulky white or yellowish 

 ash. This ash is not alkaline, and consists principally of 

 alumina and sulphate of lime. The ash was in most cases 

 so considerable that I was led to suspect that this colour- 

 ing-matter might possibly be a compound of the other with 

 some earthy base, in which case the striking similarity in 

 the properties and reactions of the two substances would 

 have admitted of an easy explanation. In order to submit 

 this supposition to the test of experiment, I took some of 



