Page:Proceedings of the Royal Society of London Vol 1.djvu/329

Rh Description of an Apparatus for the Analysis of the Compound Inﬂam- mahle Gases by slow Combustion ; with Experiments on the Gas from Coal, eaplaining its Application. By William Henry, M.D. Vice- Pres. of the Lit. and Phil. Society, and Physician to the Inﬁrmary, at Manchester. Communicated by Humphry Davy, Esq. Sec. R.S. Read June '23, 1808. [Phi]. Trans. 1808, p. 282.]

The object of this memoir is to remove some obstacles which pre- sent themselves to a successful inquiry into the nature of compound inﬂammable gases. When a vegetable substance is submitted to dis- tillation, at a temperature not below that of ignition, the equilibrium of aﬂinities is destroyed, and the elements composing it are united in a new manner. The carbon, uniting with oxygen, either composes carbonic acid gas, or stopping short of that degree of oxygenation, is converted into carbonic oxide. The hydrogen, combining with a. portion of charcoal, forms either carburetted hydrogen gas, or super- carburetted hydrogen, better known by the name of oleﬁant gas. Towards the close of the process, simple hydrogen gas is also min- gled with the products.

The method hitherto pursued for the analysis of inﬂammable gases, has consisted in mixing them with a known proportion of oxygen, burning the mixture by the electric spark, noting the ﬁrst contraction and subsequent diminution, by lime-water, for the quantities of water and of carbonic acid formed, and thence inferring the proportion of hydrogen and of carbon in the gas examined, without making due allowance for the possible admixture of carbonic oxide, either before or after the combustion.

The author ascertains the presence of this gas by its great speciﬁc gravity, and by the very small proportion of oxygen with which it unites; but in the distillation of coal there is also often present a quantity of sulphuretted hydrogen, and an inﬂammable gas, which may possibly be a gas sui generis, but is more probably a mixture of carburetted hydrogen and carbonic oxide.

In Dr. Henry’s apparatus, which is not readily explained without reference to a drawing, the gas to be examined is passed through a small tube into a receiver containing oxygen gas, and is there burned by a continued ﬂame. The quantity of gas introduced, and quantity of contraction, are noted. The quantity of carbonic acid formed is found by liquid potash. The remaining oxygen is determined by sulphnret of lime. As it sometimes happens that part of the gas escapes combustion, precautions are given for avoiding that source of error, and the means of detecting it described.

Instances are given of computation, from combustion, of hydrogen gas, of oleﬁant gas, as the most simple, and of gas from cannel coal, in which it is a problem of some diﬁiculty to determine the prepartions of all the gases that occur; and these are carbonic acid, sulphuretted hydrogen, oleﬁant gas, carburetted hydrogen, and carbonic oxide.

The sum of the two ﬁrst is dctermined by liquid potash, after