Page:Experimental researches in chemistry and.djvu/187

172 In the same way some of the more fixed essential oils may be used, as dry oil of turpentine; and even a portion of the condensed liquor itself as that part which requires a temperature of 220° or 230° for its ebullition; care being taken to estimate the expansion of the gas by the vapour of the liquid, which may readily be done by a known portion of common air preserved over the liquid as a standard.

With reference to the proportions of the different substances in the liquid as obtained by condensation of oil-gas, it is extremely difficult to obtain anything like precise results, in consequence of the immense number of rectifications required to separate the more volatile from the less volatile portions; but the following Table will furnish an approximation. It contains the loss of 100 parts by weight of the original fluid by evaporation in a flask, for every 10° in elevation of temperature, the substance being retained in a state of ebullition.

The residue, 3.4 parts, was dissipated before 250° with slight decomposition. The third column expresses the quantity volatilized between each 10°, and indicates the existence of what has been described as bicarburet of hydrogen in considerable quantity.