produced by Platinum. 43 



notice of chemists, that in more than one case platinum acts 

 exactly like common electricity, both of them determining at 

 the common temperature, for instance, the oxidation of free 

 hydrogen. Now it being well known that nitric acid is formed 

 if electrical sparks are made to pass through moist air, it 

 seemed to me within the reach of possibility, that the same 

 acid might be produced by platinum, if that metal in a state 

 of minute mechanical division were placed in contact with 

 moist atmospheric air. With the view of ascertaining the 

 correctness of that conjecture, I put a piece of moist litmus 

 paper in close contact either with spongy platinum, or with 

 platinum black. In some cases part of the paper exhibited 

 a slight reddish coloration, part of it proved to be entirely 

 bleached, or nearly so. I must, however, not omit to state, 

 that in the great majority of my experiments I obtained bleach- 

 ing effects only, and no reddening of the litmus paper what- 

 ever. I am unable to account for the difference of the results 

 mentioned. Was the reddening of the litmus paper caused 

 by some traces of nitric acid formed under the circumstances 

 indicated ? I am not prepared at all to answer that question. 

 If nitric acid should however happen to be produced under 

 the circumstances mentioned, it would be a fact, in my opinion, 

 not very difficult to be accounted for. In whatever state the 

 oxygen surrounding platinum may be, certain it is that that 

 state is such as to render oxygen very apt to combine at the 

 common temperature with a number of oxidable substances 

 that would not be oxidized by common oxygen without the 

 presence of platinum. The formation of nitric acid taking 

 place under the circumstances mentioned, would indeed be a 

 fact very similar to the combustion of detonating gas caused 

 by platinum. I repeat, however, that I consider the genera- 

 tion of nitric acid brought about by the agency of platinum, as 

 far from being established by decisive facts. 



The voltaic character of bodies being so intimately con- 

 nected with their chemical nature, that in most if not in all 

 cases we may infer the one from the other, the fact I am 

 going to state merits our attention. Chlorine, bromine, iodine, 

 ozone, and a number of metallic peroxides, enjoy consider- 

 able electro-motive powers, which are of such a kind as to 

 render those bodies what is commonly called electro-negative. 

 Hence it comes that a piece of metal being covered with any 

 one of the bodies named, bears to another common piece of 

 the same metal the same voltaic relation as copper does to 

 zinc. According to the experiments of De la Rive and some 

 other philosophers, platinum foil being covered with some 

 spongy platinum, is negative to common platinum plate, a 



