Biographical Memoir irfthe late Dr Her.iy. 11 



were then detonated in a volta tube with oxygen, and afforded 

 results, shewing that they were mixtures of carburetted hydro- 

 gen, carbonic oxide and hydrogen gases, in proportions which 

 he was then unable to determine except by approximative cal- 

 culation. — " No one instance," he concludes, " has ever occurred 

 to me of a gas obtained from oil or coal, which, after the action 

 of chlorine upon it, with the exclusion of light, presented a 

 residuum at all approaching to simple hydrogen gas." 



In his latest communication to the Royal Society (1824), Dr 

 Henry succeeded in conquering the only remaining difficulty in 

 the analysis of these complex mixtures ; viz., the ascertaining, 

 by chemical means, the exact proportions which the gases, left 

 after the action of chlorine on oil and coal gas, bear to each 

 other. For this purpose he skilfully availed himself of the 

 property, which had been recently discovered by Dobereiner 

 in finely divided platina, of determining gaseous combination. 

 Having ascertained that carbonic oxide with oxygen is rapidly 

 converted into carbonic acid, in presence of platina at a tempe- 

 rature of 340° Fahrenheit, while carburetted hydrogen is wholly 

 unchanged, till the heat considerably exceeds that of boiling 

 mercury, Ur Henry exposed a mixture of carbonic oxide, hy- 

 drogen, and carburetted hydrogen with oxygen, into which pla- 

 tina had been admitted, to the temperature of 340°. The car- 

 bonic oxide and hydrogen were converted into carbonic acid and 

 water, — and their relative proportions easily determined. The 

 residuary carburetted hydrogen was then detonated with oxy- 

 gen in a volta eudiometer. The numbers thus obtained cor- 

 responded precisely with the quantities of the gases that had been 

 mingled together. In further trial of this new mode of operat- 

 ing, it was applied to the analysis of a mixture of the same 

 gases, but in unknown proportions, which constitutes an inferior 

 quality of coal gas. The specific gravity of this gas, derived 

 from the proportions thus ascertained of its constituents, was 

 .303, a number coinciding as nearly as could be expected with 

 the actual specific gravity of the gas .308. 



In the course of this enquiry, Dr Henry noticed the curious 

 property of gaseous interference, which was observed about the 

 same time, and first made public by Dr Turner. Though not 

 affecting the main object of his researches, these phenomena at- 



