Dr. Henry must have contained not only this compound, and a portion of the bicarburet of hydrogen, but also portions of the other (as yet apparently indefinite) substances; and there can be no doubt that the quantity of these vapours will vary from the point of full saturation of the gas, when standing over water and oil, to unknown, but much smaller proportions. It ls therefore an object in the analysis of oil and coal-gas, to possess means by which their presence and quantity may be ascertained; and this I find may be done with considerable exactness by the use of sulphuric acid, oil, &c., in consequence of their solvent power over them.
Sulphuric acid is in this respect a very excellent agent. It acts upon all these substances instantly, evolving no sulphurous acid; and though when the quantity of substance is considerable as compared with the acid, a body is left undecomposed by or uncombined with the acid, and volatile, so as constantly to afford a certain portion of vapour, yet when the original substance is in small quantity, as where it exists in vapour in a given volume of gas, this does not interfere, in consequence of the solubility of the vapour of the new compound produced by the action of the acid in the acid itself in small quantities: and I found that when 1 volume of the vapour of any of the products of the oil-gas liquor was acted upon, either alone, or mixed with 1, 2, 3, 4, up to 12 volumes of air, oxygen, or hydrogen, by from half a volume to a volume of sulphuric acid, it was entirely absorbed and removed.
When olefiant gas is present, additional care is required in analytical experiments, in consequence of the gradual combination of the olefiant gas with the sulphuric acid. I found that 1 volume of sulphuric acid in abundance of olefiant gas, absorbed about 7 volumes in twenty-four hours in the dull light of a room; sunshine seemed to increase the action a little. When the olefiant gas was diluted with air or hydrogen, the quantity absorbed in a given time was much diminished; and in those cases it was hardly appreciable in two hours,
the similar salts of MM. Liebig and Gay-Lussac, except their composition (Gilbert's Annalen, lxxviii. 157; Ann. de Cbimie, xxvii. 190). M. Gay-Lussac observes, that if the analysis be correct, the difference can only be accounted for by admitting a different mode of combination.
