S'l-G Dr. Faraday's Experimoital Researches in Electricity* 



intensity of the current^ or to the chemical nature of the elec- 

 trodes and the surrounding fluids. 



1026. When the acid was sulphuric acid, increasing its 

 strength in any of the cells, caused no change in the effects ; 

 it did not produce a more intense current in the exciting cells 

 (908.), or cause the current produced to traverse the decom- 

 posing cells more freely. But if to very weak sulphuric acid 

 a few drops of nitric acid were added, then either one or other 

 of those effects could be produced ; and, as might be expected 

 in a case like this, where the exciting or conducting action 

 bore a direct reference to the acid itself, increasing the strength 

 of this (the nitric acid), also increased its powers. 



1027. The nature of the interposed plate was now varied to 

 show its relation to the phaenomena either of excitation or 

 retardation, and amalgamated zinc was first substituted for 

 platina. On employing one voltaic pair and one interposed 

 zinc plate, fig. 28, there was as powerful a current, apparently, 

 as if the interposed zinc plate was away. Hydrogen was 

 evolved against P in cell ii, and against the side of the second 

 zinc in cell i ; but no gas appeared against the side of the zinc 

 in cell ii, nor against the zinc in cell i. 



1028. On interposing two amalgamated zinc plates, fig. 29, 

 instead of one, there was still a powerful current, but inter- 

 ference had taken place. On using three intermediate zinc 

 plates, fig. 30, there was still further retardation, though a 

 good current of electricity passed. 



1029. Considering the retardation as due to the inaction 

 of the amalgamated zinc upon the dilute acid, in consequence 

 of the slight though general effect of diminished chemical 

 power produced by the mercury on the surface, and viewing 

 this inaction as the circumstance which rendered it necessary 

 that each plate should have its tendency to decompose water 

 assisted slightly by the electric current, it was expected that 

 plates of the metal in the unamalgamated state would pro- 

 bably not require such assistance, and would offer no sensible 

 impediment to the passing of the current. This expectation 

 was fully realized in the use of two and three interposed 

 unamalgamated plates. The electric current passed through 

 them as freely as if there had been no such plates in the way. 

 They offered no obstacle, because they could decompose 

 water without the current ; and the latter had only to give di- 

 rection to a part of the forces, which would have been active 

 whether it had passed or not. 



1030. Interposed plates of copper were then employed. 

 These seemed at first to occasion no obstruction, but after a 



