ATTENDING THE FORMATION OF COAL, &c. 267 



and constitute rectified coal naphtha. Three are alkaline, 

 and contain nitrogen. The other four are solid and neutral. 

 It is worthy of remark, how few of the products of distilla- 

 tion contain any oxygen, and how much they differ in this 

 respect from the products of distillation of wood ; and that, 

 where the oxygen does enter into combination, it produces 

 compounds having no illuminating properties, viz., carbonic 

 oxide, carbonic acid, and water ; and that in one instance il; 

 unites with a compound of carbon and hydrogen, producing 

 an acid oil, that is found in very small quantity in the tar. 



The nitrogen of the coal forms ammonia, cyanogen, and 

 a few alkaline oils, the latter found in small quantity in the 

 tar. The products are nearly all compounds of carbon and 

 hydrogen, and respecting these it is further worthy of re- 

 mark, that when the hydrogen exists in the compound in 

 greater quantity than the carbon, as in light carburetted 

 hydrogen, which contains 2 atoms hydrogen to 1 of carbon, 

 the compound is permanently gaseous ; this gas has been 

 subjected to a pressure of 32 atmospheres, and to cold 166 

 degrees below zero, without liquefying. Olefiant gas, in 

 which carbon and hydrogen exist in equal proportions, but in 

 which 2 volumes of hydrogen and 2 of carbon are condensed 

 into one volume, is permanently gaseous at the ordinary 

 atmospheric temperature and pressure, but becomes liquid 

 under a pressure of 27 atmospheres at zero of Fahrenheit. 



The volatile hydro-carbons in coal gas, the exact nature 

 of which has not y«t been determined, and whose compo- 

 sition is valuable, or rather, perhaps, whose proportions in 

 the mixture are valuable, probably consist of propylene 

 Ce He, Faraday's gas, Cg Hg, and benzole, Ci^ He, with 

 perhaps a portion of Mansfield's allyle. In my earlier ex- 

 periments on coal gas, which had been made from a differ- 

 ent cannel to what is now employed at the Manchester 

 Gas- Works, I found, pretty uniformly, that each volume 

 of the gas condensible by sulphuric acid or chlorine re- 



