excited hy Chemical Tendencies, 315 



dergoes when voltaically associated with platina and put either 

 into nitric acid or a solution of blue vitriol. In the first case 

 nitrate of lead is formed, in the second sulphate of lead. The 

 said peroxide and platina being substances each separately 

 quite indifferent to any of the fluids named in a chemical point 

 of view, how are we to account for the deoxidation of the 

 peroxide ? No doubt can be entertained that in the circum- 

 stances mentioned a decomposition of water takes place, and 

 that the hydrogen of the latter unites with one of the two 

 equivalents of the oxygen contained in the peroxide. But by 

 what means is water decomposed ? It seems to be effected 

 by a current. As stated in my last letter to Dr. Faraday, 

 there is, indeed, a current in the case ; but in the beginning 

 at least it is a current of tendency, and as such, according to 

 the preceding statements, incapable of causing chemical decom- 

 position. Upon the first view of the matter we can hardly 

 help thinking the case in question to be analogous to that 

 which is offered by distilled or amalgamated zinc, platina, 

 and dilute sulphuric acid, that is to say, we are inclined to 

 suppose that the hydrogen of water bears in one case the same 

 relation to some part of the oxygen of the peroxide, as the 

 zinc does in the other case to the oxygen of water, and that 

 the incipient currents in both instances are due to similar 

 causes. But upon a nearer view, I think, we must give up 

 such an opinion. In the first place, it can hardly be denied 

 that there is some sensible chemical action taking place be^ 

 tween distilled zinc and acidulated water, previously to any 

 sort of a circuit being established ; such, however, is decidedly 

 not the case with regard^to nitric acid and peroxide of lead. 

 In the second place, one is really at a loss to imagine any 

 reason, why the hydrogen of water should tend to unite with 

 the oxygen of the peroxide, in order to form water again. 

 The affinity of hydrogen for oxygen being satisfied, it would 

 be, if I am allowed to speak in a metaphorical manner, on the 

 part of the former a most wanton capriciousness and ground- 

 less love of change, should it try to leave one particle of oxy- 

 gen to combine with another one of precisely the same kind. 

 As to zinc, which is in a single state, its tendency to unite with 

 the oxygen of water is quite natural, and as it were legiti- 

 mate. According to my opinion, there is only one way left 

 to account for the very remarkable decomposition which per- 

 oxide of lead undergoes in the above-mentioned circumstances. 

 By putting a voltaic association of peroxide and platina into 

 nitric acid, a current of tendency is excited, which, as already 

 stated, passes from platina through the fluid to the peroxide. 

 This current, though it be too weak to cause any electrolyza- 



