332 Dr. W. C. Henry's Experiments on Gaseous Interference. 



gamated, though incapable, when immersed in dilute sulphuric 

 acid, of effecting the decomposition of water, has yet the power, 

 by its attraction for the oxygen of the particles of water in 

 contact with its surface, to induce a peculiar state of electrical 

 tension or polarity in those particles of water, as well as a si- 

 milar but opposite state in the contiguous particles of zinc. 

 By plunging a platina plate into the solution and completing 

 the galvanic circle, this tension is relieved and decomposition 

 of water instantly ensues. In the preparatory stage of this 

 important experiment we have then a case of chemical forces 

 in undoubted operation, yet giving no appreciable sign of 

 their existence. 



Other arguments present themselves in favour of the opi- 

 nion, that the property inherent in certain gases of preventing 

 or retarding the union of hydrogen and oxygen is to be re- 

 ferred to their attraction for oxygen, and not to any peculiar 

 action of the metallic surface, by which it becomes invested 

 with the interfering gas. (1.) All the gases which have been 

 hitherto observed to exhibit this power, are such as are ca- 

 pable of uniting with oxygen ; and the non-interfering gases 

 are such as cannot, at least within a considerable range of 

 temperature, be brought to combine with that element. 

 (2.) The property of interference follows, in its comparative 

 energy, the same order as the respective combustibilities of 

 the gases. Thus Sir Humphry Davy observed that carbonic 

 oxide and olefiant were most inflammable, while carburetted 

 hydrogen required for its combustion a much higher tempe- 

 rature, being neither fired by white-hot charcoal nor iron. 

 Dr. Henry also has shown that in presence of the sponge, 

 carbonic oxide combines rapidly with oxygen at from 300° to 

 3+0° Fahrenheit ; olefiant at 520° ; and carburetted hydrogen 

 not at any temperature to which the mercurial bath could 

 be raised. I have ascertained that the two first gases observe 

 the same order of union in presence of Liebig's powder, car- 

 bonic oxide inflaming at atmospheric temperatures, and 

 olefiant gas being rapidly acted upon at 212°. Now this 

 progression is precisely that of their interfering powers, car- 

 bonic oxide acting when it constitutes only aV^ °^ ^^^ mix- 

 ture, olefiant gas not suspending action till it amounts to f ths, 

 and carburetted hydrogen possessing no power whatever of 

 retarding the action of platina even when its volume exceeds 

 by ten times that of the explosive mixture. Finally, that the 

 restraining force is wholly dependent upon the relations of 

 the mixed gases among one another, is deducible from the 

 fact that the same gases which suspend the combining ten- 

 dencies of hydrogen and oxygen in presence of platina, resist 

 also other modes of effectuating the union of those gases ; 



