544- Prof. Schoenbein on the peculiar Voltaic 



As I refer to my own papers as the only answer which I 

 mean to give to the other parts of M. Melloni's memoir, I 

 will add that \hefast appeared in the Edinb. Trans., vol. xiii., 

 and Lond. and Edinb. Phil. Mag., vol. vi. ; the second (con- 

 taining the more accurate measures) in the Edinb. Trans., same 

 volume, but it has not been reprinted. 



I am, my dear Sir, yours very faithfully, 

 Edinburgh, 15th Nov. 1837- James D. Forbes. 



LXXVIII. On the peculiar Chemical Inactivity of Bismuth, with 

 reference to the researches of Dr. Andrews ; and on the action 

 qfSeawater on Iron, Sfc. By Professor Schcenbein.* 



f T , HE short notice contained in the last number of the Bi- 

 -*- blioth. Univers. respecting Dr. Andrews's researches on 

 the action of nitric acid upon bismuth, f has induced me to make 

 some experiments on the same subject, and I now take the 

 liberty to give you a short account of the results obtained 

 from them. It certainly cannot be denied that there exists 

 some analogy between the peculiar condition of iron and that 

 of bismuth, but my impression at present is, that the cases are 

 similar, but not identical. This opinion is founded upon the 

 following facts : The chemical action of iron upon nitric acid, 

 as is now well known, can be entirely stopped by a variety of 

 ways, whilst according to my experiments it is impossible to 

 obtain such a result with bismuth. I voltaically associated this 

 metal with all the substances known to be capable of rendering 

 iron completely inactive, but by so doing I could never succeed 

 so far as to prevent bismuth from being chemically acted upon 

 by nitric acid. It is true, by putting in contact the metallic 

 body in question with platinum, the chemical action of nitric 

 acid, sp. gr. 1 '4-, may be reduced to such a low degree of in- 

 tensity that no visible disengagement of binoxide of nitrogen 

 takes place, and the piece of bismuth (immersed in nitric acid) 

 assumes a bright appearance. 



But the oxidable metal being in this state is nevertheless 

 uninterruptedly attacked by the acid fluid, as may be easily 

 shown by having recourse to the galvanometer. There are 

 besides some other facts, which put the continuance of che- 

 mical action in the circumstances mentioned beyond any doubt. 

 L think I have first ascertained the remarkable fact, that iron 

 can be rendered thoroughly inactive, not only towards the 

 oxygen of nitric acid (of any degree of dilution), but also to 



• Extracted from a Letter to Dr. Faraday, and communicated \>y him. 

 t See the present Number, p. 554. — Edit. 



