27.4" Dr. Faraduy'b Experimental Researches m Electricity, 



iieath that degree at which the elements of water, unaided by 

 any secondary force resulting from the capability of combina- 

 tion with the matter of the electrodes, or of the liquid sur- 

 rounding them, separated from each other. 



971. It may be supposed, that the oxygen and hydrog^en 

 had been evolved in such small quantities as to have entirely 

 dissolved in the water, and finally to have escaped at the sur- 

 face, or to have reunited into water. That the hydrogen 

 can be so dissolved was shown in the first vessel ; for after 

 several days minute bubbles of gas gradually appeared upon 

 a glass rod, inserted to retain the zinc and platina apart, and 

 also upon the platina plate itself, and these were hydrogen. 

 They resulted in this way. Notwithstanding the amalgama- 

 tion of the zinc, the acid exerted a little direct action upon it, 

 so that a small stream of hydrogen bubbles was continually 

 rising from its surface; a little of this hydrogen gradually 

 dissolved in the dilute acid, and was in part set free against 

 the surfaces of the rod and the plate, according to the well- 

 known action of such solid bodies in solutions of gases (623. 

 &c.). 



972. But if the gases had been evolved in the second vessel 

 by the decomposition of water, and had tended to dissolve, 

 still there would have been every reason to expect that a few 

 bubbles should have appeared on the electrodes, especially 

 on the negative one, if it were only because of its action as a 

 nucleus on the solution supposed to be formed ; but none ap- 

 peared even after twelve days. 



973. When a few drops only of nitric acid were added to 

 the vessel A, fig. 12., then the results were altogether dif- 

 ferent. In less than five minutes bubbles of gas appeared on 

 the plates P' and V in the second vessel. To prove that 

 this was the effect of the electric current (which by trial at e 

 was found at the same time to be passing,) the connexion at e 

 was broken, the plates P' P" cleared from bubbles and left in 

 the acid of the vessel B, for fifteen minutes: during that time 

 no bubbles appeared upon them ; but on restoring the com- 

 munication at e, a minute did not elapse before gas appeared 

 in bubl)les upon the plates. The proof, therefore, is most 

 full and complete, that the current excited by dilute sulphuric 

 acid with a little nitric acid in vessel A, has intensity enough 

 to overcome the chemical affinity exerted between the oxygen 

 and hydrogen of the water in the vessel B, whilst that excited 

 by dilute sulphuric acid alone has not sufficient intensity. 



974. On using a strong solution of caustic potassa in the 

 vessel A, to excite the current, it was found by the decom- 

 posing effects at e, that the current passed. But it had not 



