1821.] of Charcoal mid Hydrogen. 173 



were ascertained, both by Dr. Davy and the late Dr. Murray,* 

 to depend on the presence of moisture, which is unavoidably 

 introduced in the common mode of operating; for when the 

 gases, first perfectly dried, were mixed in an exhausted glass 

 vessel, and exposed even to the direct rays of the sun, no mutual 

 action was found to ensue. In the theoryof 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, and 

 on that of the combustible gas ; or does it decompose water 

 only? The former view of the subject appears to me most pro- 

 bable, because, if the chlorine acted on water only, free hydro- 

 gen would be evolved from that portion of the hydrocarburet 

 which abandons its charcoal to the oxygen of the water; which 

 is not consistent with experience. When it is required to form 

 carbonic 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 hydro- 

 gen existing in the combustible gas, and the two other atoms of 

 chlorine with the two atoms of hydrogen from the water. But 

 to convert carburetted 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. Calcu- 

 lating 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 analyzing 

 mixtures of olefiant gas, either with hydrogen or with carburet- 

 ted hydrogen, if light be admitted, even though of feeble inten- 

 sity, and for the short interval during which such an experiment 

 may be expected to continue : and they explain that uncer- 

 tainty as to the results of analyses of mixed gases made in this 

 way, which was first remarked by Mr. Faraday,f and subse- 

 quently by myself.J 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 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 opaque cover. A measured 

 quantity of the mixture was then passed up, and in about 10 

 minutes the outer cover was cautiously lifted, till the surface of 



• Nicholson's Journal, xxviii. 143, and 201. 



•f Journal of Science, &c. vi. 358. 



£ Manchester Memoirs, New Series, vol. iii. 



