of Charccal and Hydrogen. 97 
found toensue. In the theory of these changes there is, it must 
-be confessed, a little uncertainty. Does the chlorine, it may be 
asked, act simultaneously on the hydrogen of water, aud on that 
of the combustible gas ; or does it decompose water only? The 
former view of the subject appears to me most probable, because, 
if the chlorine acted on water only, free hydrogen would be 
evolved from that portion of the hydro-carburet which abandons 
its charcoal to the oxygen of the water; which is not consistent: 
with experience. When it is required to form carbonie acid, four 
volumes of chlorine must be used for the decomposition of each 
volume of carburetted hydrogen. In this case, two atoms of 
chlorine unite with the two atoms ,of hydrogen existing in the 
combustible gas, and the two other atoms of chlorine with the 
two atoms of hydrogen from the water. But to convert car- 
buretted hydrogen into carbonic oxide, three atoms of chlorine 
are sufficient, two of which are employed as in the first case, 
and the third is expended in saturating the hydrogen of one 
atom of water, which supplies to the charcoal an atom of oxygen 
for the formation of carbonic oxide. Calculating in the same 
-manner, we shall find, also, that three atoms of chlorine are 
adequate to convert-one atom of carbonic oxide into carbonic 
acid. 
The facts which have been stated sufficiently prove, that chlo- 
rine cannot be employed as a means of correctly analysing mix- 
tures of olefiant gas, either with hydrogen or with carburetted 
hydrogen, if light be admitted, even though of feeble intensity, 
and for the short interval during which such an experiment may 
he expected to continue: and they explain that uncertainty as 
to the results of analyses of mixed gases made in this way, which 
was first remarked by Mr. Farraday*, and subsequently by myself}. 
Chlorine becomes, however, a most useful agent in separating 
olefiant gas from such mixtures, provided light be entirely ex- 
cluded during its operation, as I have found by subjecting to its 
action mixtures of those gases with known proportions of olefiant 
gas. In these analytical experiments, | admitted into a graduated 
. tube standing over water, a volume of chlorine exceeding by about 
one half what was known to be sufficient, and noted its bulk when 
actually in the tube, which was immediately shaded by an opake 
cover. A measured quantity of the mixture was then passed up, 
and in about ten minutes the outer cover was cautiously lifted, 
till the surface of the water appeared. The diminution of volume 
thus ascertained, divided by 2, was found to give pretty correctly 
the quantity of olefiant gas known to be contained in the mix- 
ture. But the greatest precision was attained by waiting fifteen 
, _* Journal of Science, &c.. vi. 358. 
+ Manchester Memoirs, New Series, vol, iii, 
Vol. 58, No, 280, Aug. 1821. N ture, 
, 
