Mr. Grove on the Gas Voltaic Battery. 425 



bine with the zinc; but touch both zinc and liquid with pla- 

 tinum, and combination ensues, the platinum being unaltered. 

 So with a mixture of oxygen and hydrogen, the gases, although 

 in intimate contact, will not chemically unite, but touch them 

 with clean platinum and more or less rapid combination ensues. 

 Here also the platinum is unaltered. Leaving out of the case 

 any purely hypothetical explanation, why may not effects so 

 similar in their character be related in other respects? In 

 the voltaic combination the platinum is heated during action, 

 and if the surfaces, and consequently the quantity of electro- 

 chemical action be considerable, it is ignited ; so in the cata- 

 lytic combination, if the platinum be thin and of large extent, 

 or in the form of a sponge, which still more increases its sur- 

 face, it is ignited. Why, therefore, may we not regard the de- 

 tonation of gas by platinum as a voltaic effect? or the combina- 

 tion of oxygen and zinc by the presence of platinum a catalytic 

 effect? The only difference is, that gases do not admit of that 

 interchangeable relation of particles which we call electrolysis. 

 The necessity for this interchange is, however, removed when 

 the gases are in a state of such intimate admixture that it is 

 .not requisite to convey the action through a chain of particles ; 

 in the gas battery this chain is supplied by the intervening 

 electrolyte, and thus the same action which is local in the ex- 

 periments of Dobereiner is circulating in the gas battery ; the 

 latter bears the same relation to the former as the action of 

 the ordinary voltaic battery does to the normal phenomena 

 of chemical affinity. This relation is confirmed by the facts 

 detailed in the paper of Dr. Henry, as the gases which he 

 there found would combine by the presence of spongy plati- 

 num, are precisely those which will combine in the gas bat- 

 tery ; thus oxygen and hydrogen combine rapidly, oxygen and 

 carbonic oxide much more slowly, and oxygen and defiant 

 gas very feebly, so much so, as, in Henry's experiments, to 

 require heat to induce combination. Of course chlorine and 

 hydrogen, which will unite without platinum, will, a fortiori, 

 unite with the aid of platinum, or they may in the gas battery 

 occasion secondary action ; the oxygen evolved by the decom- 

 position of water by the chlorine combining with the free hy- 

 drogen in the tube. As oxygen and ammonia will, when at 

 a slightly elevated temperature, combine by the influence of 

 spongy platinum, forming water and leaving nitrogen, I now, 

 in order further to test this relation, tried 



Experiment 26. — Ten cells of the gas battery were charged 

 with oxygen and solution of ammonia, with a little sulphate 

 of ammonia added to improve its conducting power. This 

 arrangement produced a moderate effect upon the iodide, 



