M. Viard on the Electro-chemical Deportment of Oxygen. 257 



Neither of these explanations can be general. Why is it 

 necessary to admit, in batteries where silver and copper are the 

 most oxidable metals, that the effect is due to depolarization, 

 when there are no facts supporting this hypothetical disengage- 

 ment of hydrogen ? 



How is it possible to admit, in batteries where silver and pla- 

 tinum form the negative plates, that the oxidation of these metals 

 can produce the current, when this oxidation in itself is so little 

 known as to be altogether disputed by many philosophers ? How 

 can we conceive that platinum, the least oxidable of metals, can, 

 by its oxidation and deoxidation, make, at the same time, most 

 oxygen disappear ? 



There is, however, little doubt that in batteries where a cur- 

 rent can be produced without the intervention of oxygen, in 

 batteries of zinc and platinum, for example, a deposit of hydrogen 

 may in some points take place, and that the subsequent presence 

 of some molecules of oxygen may serve to depolarize the plates ; 

 experience, too, has long since proved, that if some oxide has 

 been formed upon the negative plate, a current may take place 

 between the positive plate and this oxide, accompanied with 

 reduction of the latter. 



But, inasmuch as there are no grounds for denying that 

 gases absolutely possess the property of conducting electri- 

 city, of acting as electromotors, without which properties, indeed, 

 they would constitute a class distinct from all other bodies, 

 whereas a crowd of experiments, and particularly those of 

 Faraday, tend, on the contrary, to attribute the same properties 

 in different degrees to all bodies, whatever their state, — I think 

 that when the negative plate is covered with oxygen, we must in 

 general admit that a great part of the current, and often the 

 whole, is produced under the influence of the positive plate and 

 the free oxygen. 



We may here remark, too, that in the batteries we have ex- 

 amined, the oxygen of the aerated liquids not only ought to dis- 

 appear by means of the current between the two plates, but that 

 a certain quantity of it would be absorbed at the surface of the 

 plates, either directly, or by the artificial currents. And when 

 we consider that the oxygen of the negative plate can, at the same 

 time, produce currents with the metallic parts of this plate, and 

 currents with the more oxidable plate ; that if the former enjoy 

 a less resistance, the latter exceed in electromotor force, we shall 

 conceive that, according to circumstances, these two kinds of 

 currents would surpass each other alternately, and that in all 

 cases the presence of the most oxidable plate protects the less 

 oxidable one united to it. 



Phil. Mag. S. 4. Vol. 6. No. 39. Oct. 1853. S 



