Experiments on the Gasfrovi Coal. 119 



Product. 



oz. dr. 

 A cubic foot weighs . . 13 

 Consumes | a cul)ic foot 



of oxygen . . . . Oil 



1 14 Carbonic acid 1 14 

 4. Olefiant gas, or Bi-carburetted hydrogen. — This 

 has been demonstrated to be a compound of nearly 85 by weight 

 charcoal, and 15 hydrogen, without any oxygen. It is a little 

 lighter than common air, viz. in the proportion of about 974 to 

 1000. It surpasses all other gases in the brightness and density 

 of its flame. Its name was originally derived from the property 

 which it possesses, of being speedily and entirely condensed, by 

 rather more than an equal volume of chlorine gas, into a liquid 

 resembling oil in appearance, but since shown to approach more 

 nearly to the nature of ether. 



5 3 5 3 



Olefiant gas I found to be one of the })roducts of the distilla- 

 tion of oil and of bees' wax, and was led, therefore, to suggest, 

 that the wick of a lamp or candle, surrounded by flame, is to be 

 considered as a bundle of ignited capillary tubes, into which the 

 melted inflammable matter is drawn, and there resolved, not into 

 a condensable vapour, but into olefiant and carburetted hydrogen 

 gases. In the gas from coal, also, I detected the presence of 

 olefiant gas, by the test of the action of chlorine. 



In the second series of experiments*, I submitted to distilla- 

 tion, on a small scale, various kinds of coal, from different parts 

 of the kingdom. Tlie aijriform products, at different stages of 

 the process, were kept apart, and were separately analysed. From 

 coal distilled in small iron tubes or retorts, which, when filled, 

 were placed at once in a low red heat, small quantities ol sulphu- 

 retted hydrogen and carbonic acid gases came over at first, in 

 mixture with the other gases, but in a gradually diminishing pro- 

 portion, till at length, in the last products, they were not disco- 

 verable at all. The ])roduction of olefiant gas observed the same 

 order, and a gradual diininution took place, as the process ad- 

 vanced, in the combustibilitv of the gas, as determined by its re- 

 quiring less and less oxygen for saturation. A great variety was 



• Phil. Trans. 1S08, page 282. 



H 4 ascertained 



