450 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



ing this lengthened period, not the slightest appearance of a bubble upon either of the 

 plates in that vessel occurred. From the results of the experiment, I conclude that 

 a current had passed, but of so low an intensity as to fall beneath that degree at 

 which the elements of water, unaided by any secondary force resulting from the 

 capability of combination with the matter of the electrodes, or of the liquid surround- 

 ing them, separated from each other. 



971. It may be supposed, that the oxygen and hydrogen had been evolved in such 

 small quantities as to have entirely dissolved in the water, and finally to have escaped 

 at the surface, or to have reunited into water. That the hydrogen can be so dis- 

 solved 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 amalgamation 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, accord- 

 ing 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 sup- 

 posed to be formed ; but none appeared 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 different. In less than five minutes bubbles of gas ap- 

 peared on the plates P' and P" 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 communication at e, a minute did not elapse before gas 

 appeared in bubbles 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, wliilst 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 decomposing effects at e, that the current passed. But 

 it had not intensity enough to decompose the water in the vessel B ; for though left 

 for fourteen days, during the whole of which time the current was found to be pass- 

 ing, still not the slightest appearance of gas appeared on the plates P' P", nor any 

 other signs of the water having suffered decomposition. 



975. Sulphate of soda in solution was then experimented with, for the purpose of 



