3 47 
of charcoal and hydrogen. 
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 
chlorine cannot be employed as a means of correctly analyz- 
ing mixtures 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 be expected to continue : and they ex- 
plain that uncertainty as to the results of analyses of mixed 
gases made in this way, which was first remarked by Mr. 
Faraday* and subsequently by myself. -f- Chlorine becomes, 
however, a most useful agent in separating olefiant gas from 
such mixtures, provided light be entirely excluded 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, I admitted into a gra- 
duated tube standing over water, a volume of chlorine ex- 
ceeding by about one half what was known to be sufficient, 
and noted its bulk when actually in the tube, which was im- 
mediately 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 mixture. But the 
greatest precision was attained by waiting 15 or 20 minutes, 
and then quickly washing the remaining gas with dilute solu- 
tion of potash, in order to remove the excess of chlorine. 
* Journal of Science, &c. vi. 358. + Manchester Memoirs, new Series, vol. iii. 
