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Description of an Apparatus for the Analysis of the Compound Inflam- 

 mable Gases by slow Combustion ; with Experiments on the Gas from 

 Coal, explaining 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. [Phil. 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 affinities 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 

 sulphuret 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 difficulty to determine the propor- 

 tions of all the gases that occur ; and these are carbonic acid, sul- 

 phuretted hydrogen, olefiant gas, carburetted hydrogen, and carbonic 

 oxide. 



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



