of Charcoal and Hydrogen. 95 
having acquired a small quantity of those gases which are always 
present in water, and of which it is impossible to deprive it even 
by long continued boiling. 
The process, by which carburetted hydrogen gas is evolved in 
natural operations, is no doubt the decomposition of water, and 
admits of being explained on the atomic theory of Mr. Dalton, 
by supposing two atoms of charcoal to act at once on two atoms 
of water. One atom of charcoal attracts the two atoms of hy- 
drogen, forming carburetted hydrogen gas, and the other atom 
of charcoal unites with two atoms of oxygen, constituting carbo- 
nic acid. This is illustrated by the annexed 
figure, iti which two atoms of charcoal C.C. are 
represented as interposed between two atoms of 
water, each consisting of an atom of hydrogen 
and an atom of oxygen. Dividing the diagram 
vertically into three parts, we have the original substances ; and 
separating it horizontally, we obtain the two new compounds. 
This theoretical view of the subject is confirmed by the fact, that 
the carburetted hydrogen, formed at the bottom of stagnant 
pools, is never accompanied by carbonic oxide, but always by 
carbonic acid, the full quantity of which is prevented from ap- 
pearing, in consequence of the absorption of a great part of it by 
the mass of water, under which the changes are taking place. 
Being provided with such an abundant supply of carburetted 
hydrogen, I availed myself of it to examine the mutual action of 
that gas and chlorine on each other, principally with a view to 
ascertain, how far reliance may be placed on the latter as an in- 
strument in the analysis of mixed combustible gases. ‘This is a 
part of the subject that was first investigated, though with a dif- 
ferent view, by Mr. Cruickshank*. | He observed that a mixture 
of chlorine with hydrogen, carburetted hydrogen, or carbonic 
oxide, in certain proportions, kept in a bottle entirely filled with 
the mixture, and furnished with an air-tight stopper, did not ex- 
hibit any immediate action, but that in twenty-four hours, on 
withdrawing the stopper, the fluid immediately rushed in, and 
filled most of the space originally occupied by the gases. But he 
was not aware of the influence of light on these changes, which 
was discovered about the same time by Gay Lussac ¢ and by Dal- 
tont. It does not, however, appear to have been ascertained 
by either of them, whether the complete exclusion of light pre- 
vents any degree of action of chlorine and carburetted hydrogen 
on each other. I mixed, therefore, those two gases in different 
proportions in well stopped vials, which were completely filled 
* WNicholson’s Journal, 4to. v. 202. 
+ Mem. de la Soe. d'Arcueil, ii. 349. 
t New System of Chemieal Philosophy, p. 300. 
with 
