Experiments on the Gas from Coal. 123 



TABLE IV. 



Comparative Tabic of the Qualities of the Gases from IVigan 

 Cannel, and from common Coaly at equal Timesfrom the Com- 

 mencement of the Distillation. 



Oxygen consumed Oxygen consumed by 



by 100 m. can- ] 00 m. of Clifton 



It appears from these experiments, that the gas from cannel 

 has, in an equal volume, an illuminating power about one-third 

 greater than that from coal of medium quality. The quantity, 

 also, from the former substance, exceeded by about one-seventh 

 that obtained from coal, distilled under precisely similar circum- 

 stances ; 3500 cubic feet of gas having been collected from 1 120 

 pounds of cannel, and only 3000 cubic feet from the same quan- 

 tity of coal. The whole product of one distillation of cannel, 

 mixed together in a gasometer, was of such quality, that 100 

 measures required for combustion 155 measures of oxygen gas,- 

 and gave 88 measures of carbonic acid. But as the gas was con- 

 taminated with 15 measures of azote in every hundred, the oxy- 

 gen, required for saturating 100 measuies of the really combus- 

 tible part of it, may be stated at 195; and the carbonic acid 

 produced at 110. It may be necessary to observe, that in com- 

 paring the value of gases produced from different kinds of coal, 

 or from the same kind of coal differently treated, it is not enough 

 to determine the quantity of aeriform products ; and no satis- 

 factory conclusion can be drawn res|)ecting the relative fitness of 

 any variety of coal for affording gas, or the advantages of clif- 

 ferent modes of distillation, unless the degrees of combnsiihility 

 of the gases compared be determined, by finding experimentally 

 the proportion of oxygen gas required for their saturation. 



The results expressed in the first table, when contrasted with 

 those which 1 formerly obtained by the destructive distillation of 

 small quantities of coal, present several circumstances of dis- 

 agreement, as to the quality of the products at different stages of 

 the operation. In small experiments, the sulphuretted hydrogen 

 and carbonic acid gases were evolved only at the early stages of 

 the process ; and sulphuretted hydrogen, especially, could not by 

 the nicest tests be discovered in the last products of gas. On the 

 large scale, both these gases continue to be evolved throughout 

 the whole operation, though in grcatlv diminished proportion to- 

 wards 



