A Manual of Experiments Illustrative of Chemical Science

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: III.?DEFINITION OF GASES, WITH THE METHOD OF PREPARING THEM. Definition of Gases. JJY a gas is to be understood that form of matter which remains permanently elastic, or is aerial at a reduced temperature; we thus adopt a distinction between gas and vapour, the latter becoming liquid or solid as soon as the temperature is sufficiently decreased. Hence steam is an elastic vapour; but when the temperature is lowered by only a few degrees, it is resolved into water again; iodine also at 158 F. becomes a violet- coloured vapour, but when cool it condenses into crystals, which by Wollaston's reflective goniometer, appear to be octohoedra. The distinction now assumed, however, must not be pressed too closely, since modern discovery has effected the condensation and liquefaction of such gases as are absorbable by water; and it is not improbable that the condensation of others may eventually be accomplished. In the carbonates, the carbonic acid gas is locked up in a highly-compressed form. In water, oxygene and hydrogene, its chemical elements, are exceedingly condensed; and in chloride of azote, its gaseous constituents, chlorine and azote, are so closely united, that a gallonof the combined gases in this compound might repose within the shell of a hemp-seed;?its explosive and expansive force is terrible. I have discovered, that the vapour of sulphuric ether, and that of sulphuret of carbon, at the common temperature, may be treated very much like carbonic acid gas in its character of superior specific gravity, and they have become the means of a series of interesting experiments. For the liquefaction of the gases we are indebted to Mr. Faraday: cold and compression are the agents employed, though Sir H. Davy stated his having accomplished the liquefaction of carbonic aci...