98 Mr. Grove Ofi the Decomposition of Water by Heat. 



affinity ; thus, as we say when employing the voltaic battery, 

 that we decompose water by electricity, so here we should say 

 that we decompose it by heat. 



If it be said that heat so weakens or antagonizes the affinity 

 of the elements of water as to enable catalytic action to sepa- 

 rate them, this amounts to the same theory, as heat is then 

 regarded as the antagonizing force, and in this case the action, 

 both thermic and catalytic, is the reverse of the normal action. 

 I have thought it desirable shortly to discuss this question as 

 likely to lead to further investigation, though I liave been 

 somewhat embarrassed by the want of definite meaning in the 

 term catalysis; I must plead guilty to have frequently used 

 the term, but notwithstanding, or perhaps on account of, its 

 convenience, it has I fear had an injurious effect on scientific 

 perspicuity. 



The following experiments were made to ascertain whether 

 platinum was the only substance by which the effect could be 

 produced. A knob or button of the native alloy of iridium 

 and osmium of the size of a small pea was formed by the vol- 

 taic battery; to this was attached by fusion another smaller 

 knob of the same metal one-fourth the size of the former, and 

 to this smaller one was attached a stout platinum wire ; the 

 object of the second knob was both to prevent the fusion of the 

 platinum wire and also to avoid the possibility of any surface 

 of platinum being exposed to the recipient tube or alloyed with 

 the metal to be heated. The preparation of this simple in- 

 strument was very troublesome, but when made it answered 

 the purpose well ; the larger button could be fully ignited to 

 an intense glow, while on account of the narrow neck which 

 united them, the smaller was barely red-hot, and the platinum 

 wire not perceptibly ignited. An experiment having been 

 made with this metallic button and prepared water, similar to 

 that previously made with platinum, gas was given off which 

 averaged 0*3 of mixed gas ; the residue was nitrogen mixed 

 with varying small quantities of oxygen. The effect, upon the 

 whole, was decidedly inferior to that of the platinum. Indeed 

 as platinum is the most dense and unalterable of all known 

 substances, it would be likely, upon any received theory of 

 heat, to produce the greatest effects. 



I tried palladium in the same manner ; the gas yielded was 

 hydrogen with small quantities of oxygen, and the water was 

 stained with the oxide of the metal. 



I now tried silica and other oxides, but the results were 

 not very satisfactory. A spheroid of silica was formed by 

 fusing pulverized silica on to a platinum wire, so as to cover 

 it for the length of 0*4; of an inch ; when this was plunged into 



