Improvements in Science. 445 



ing as they are good conductors of electricity. 8th. The che- 

 mical changes in the pile are certainly allied to the re- 

 combination by means of the solid bodies in the pile of the 

 electricities set free, but there does not exist between these 

 phenomena any dependence as cause and effect. 9th. In a 

 re-union of the elementary piles (pile of Volta) the opposite 

 electricities are completely neutralized, by the solid bodies 

 of each element, and there is no transmission of electricity 

 from one element to the other.* 



2. Action of nitric acid on the oxidizahle metals. — This 

 curious subject has been well illustrated by the experiments 

 of Herschel and Schonbein, as well as by those of Keir, 

 Wetzlar, Fischer, Fechner, and Faraday. The deduction 

 from their researches is, that iron wire is often exhibited 

 under certain circumstances, as a metal easily acted on by 

 acids, and that sometimes on the contrary, in consequence 

 of slight modifications of the experiment, it resists oxida- 

 tion with the greatest obstinacy. Schonbein accounts for 

 this curious fact, by supposing, that a peculiar action is 

 induced by which the natural affinity of the metal is altered, 

 while Mr Faraday ascribes the cessation of action to the 

 presence of a thin layer of oxide, which, however, is not 

 perceptible to the eye. M. Mousson not satisfied with 

 these explanations, considers the following more satisfac- 

 tory : 1 . It is not necessary in order to explain the pheno- 

 mena of the action and passiveness of iron to have recourse 

 to a new hypothesis. 2. That the phenomena in different 

 metals only differ in degree, not in the nature of the action. 

 3. That they depend essentially on the incapacity of con- 

 centrated nitrous acid to attack several metals, (perhaps 

 even any) and of the double mode of decomposition of 

 which it is susceptible. 4. That the commencement of the 

 state of passiveness is always accompanied with an oxida- 

 tion and corresponding current. 5. That the same current, 

 according to its action on the acids, according as it favours 

 or prevents the formation, and close contact of a layer of 

 nitrous acid produces electro-chemical changes which the 

 metals present in the same nitric acid.f 



3. Negative more readily dissipated in the air than jwsitive 

 electricity. — Professor Belli has made several interesting 



* Bibliotbeque Uuiverselle, September, 1036. p. 165. t lb. \bi. 



