3 6 Mr. Brande on the composition and analysis 
free from carbon, that when detonated with its volume of 
oxygen, half a volume of the latter remained, which scarcely 
rendered lime water turbid, and underwent no perceptible 
diminution by exposure to liquid potassa. 
It may be supposed, that in consequence of the dilution of 
the last portions of olefiant by the hydrogen evolved, the per- 
fect decomposition of the gas is a matter of difficulty, and a 
trace of carbon will, I believe, always remain in the hydrogen 
evolved, since the decomposition is progressive. I cannot, 
however, on this account see reason to believe, with M. Ber- 
thollet,* that carbon and hydrogen are capable of forming 
several definite compounds ; the data are, on the contrary, 
such as to warrant an opposite conclusion. 
In making this experiment in the manner just described, 
and more especially when the tube is only dull red, the first 
portions of gas that reach the receiving gasometer, are ob- 
scured by a considerable quantity of vapour, which, however, 
afterwards disappeared. To examine more particularly the 
cause of this phenomenon, I passed some pure olefiant gas, 
very slowly, through a red hot glass tube, about two feet in 
length, and containing in the heated part some pure and well 
burned charcoal : the gas was collected in a cold receiver, 
the sides of which became lined with a brown viscid sub- 
stance of an agreeably fragrant odour, perfectly soluble in 
alcohol, and precipitated from this solution by water, which 
rendered it turbid, and of a whitish green hue. This peculiar 
resinous matter appears to be a compound of hydrogen and 
carbon ; its vapour is perfectly decomposed by passing it 
* Thenard, Traite de Chimie, Tom. I. p. 293. 
