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1820.] portion of the substance, giving rise to the second volume of the carbonic oxide, and to the calomel.

A mixture of two volume of hydrogen and one volume of oxygen was made, and three volumes of it detonated with the vapour, as before. After cooling, the expansion was to six volumes, four of which were muriatic acid, and two carbonic oxide. There was no action on the mercury in this experiment. Again, Eve volumes of the same mixture being detonated with the vapour of the substance expanded to 9.75 volumes, of which 6.25 were absorbed by water and were muriatic acid, and 3.5 were carbonic oxide mixed with a very small portion of air introduced along with the fluid chloride. These experiments, I think, establish the composition of the protochloride of carbon, and prove that it contains one proportion of each of its elements.

From a consideration of the proportions of these two chlorides of carbon, it seems extremely probable that another may exist, composed of two proportions of chlorine combined with one of carbon. I have searched as assiduously for such a compound, but am undecided respecting its production. When the fluid protochloride was exposed with chlorine to solar light, crystals were formed, as before described. The greater number of these were certainly the per chloride first mentioned in this paper; but when the retort was examined by a microscope, some rhomboidal crystals were observed here and there among those of the usual dendritic and square forms. These may perhaps be the real per chloride; but I had not time, before the season of bright sunshine passed away, to examine minutely what happens in these circumstances; and must defer this, with many other points, till the next year brings more favourable weather.

Compound of Iodine, Carbon, and Hydrogen.—The analogy which exists between chlorine and iodine, naturally suggested the possible existence of an iodide of carbon, and the means which had succeeded with the one element offered the best promise of success with the other.

Iodine and olefiant gas were put in various proportions intoretorts, and exposed to the sun's rays. After awhile, colourless crystals formed in the vessels, and a partial vacuum was produced. The gas in the vessels being then examined, was