276 EXPERIMENTAL INVESTIGATIONS. 



many more changes may be rung upon the gases employed, 

 and curious and valuable results obtained ; I have, however, 

 in this paper given a sufficient number of experiments fairly 

 to open the subject ; each appears so suggestive of new ones, 

 that it is difficult to know where to stop. 



The experiments on eudiometry, which I have last named, 

 induced me to refer to Dr. Henry's paper on Gaseous 

 Analysis,* and on reading it I was struck with a coincidence 

 between the action of spongy platinum on mixed gases and 

 the gas battery, a coincidence strongly confirmatory of the 

 views which led me to its discovery. I will endeavour briefly 

 to state these, and I state them, not as being absolutely correct, 

 for differences of opinion may exist on this as on every other 

 scientific matter, but as being those which existed in my mind 

 prior to the experiments, and which are considerably, and to 

 me unexpectedly, strengthened by the results embodied in 

 the above-mentioned paper of Dr. Henry. 



My original deduction may be stated and exemplified as 

 follows : When pure or amalgamated zinc is immersed in 

 acidulated water the oxygen, as is well known, will not com- 

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

 platinum and combination ensues, the platinum being un- 

 altered. 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 catalytic combination, if the platinum be 

 thin and of large extent, or in the form of a sponge, which 

 still more increases its surface, it is ignited. Why, therefore, 

 may we not regard the detonation of gas by platinum as a 

 voltaic effect ? or the combination 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 



* Phil. Trans,, 1824. 



