330 Mr R. Adie's Account of Electrical Experiments. 



but two plates of iron form a water battery, when one is exposed to 

 more absorbed oxygen than the other ; from which we should con- 

 clude that the electrolite of the gas or water battery, is a compound 

 more easily decomposed than the peroxide of hydrogen. Evidence 

 has been given to shew that water does not act until it contains dis- 

 solved oxygen. The whole question, then, rests on the state in which 

 this gas exists in the water : if chemically combined with it, so as 

 to form the solution of a sesquioxide of hydrogen, or some other 

 more easily decomposed oxide than the peroxide, then, in air absorb- 

 ing couples there exists a binary compound capable of obeying all 

 the laws of electrolysis proved by Dr Faraday for acidulated water, 

 where the water undergoes decomposition ; while, in the gas battery, 

 the action of the two plates is to decompose an oxide of hydrogen 

 into water and oxygen, the nascent oxygen uniting with a n.etal or 

 hydrogen at the positive plate. 



The pi'operties of the peroxide of hydrogen, as described in Dr 

 Turner's Chemistry, appeared to me to be very much the same as 

 those possessed by the solution of oxygen in water ; and as the oxide 

 of silver freely decomposes the former body, I wished to try its effect 

 on the latter. 



When a little oxide of silver is thrown into water, gas bells are 

 slowly disengaged, and it changes from brown to a pale lilac colour. 

 Two pieces of silver foil were placed in a horizontal position in 

 water, and attached to a galvanometer. When a little of the oxide of 

 silver was strewed on one of these plates, this converted it into a ne- 

 gative plate, and the bright piece of silver became positive. The 

 current generated from a single pair deposited metallic coppfer from 

 the sulphate. The change in colour of the oxide proceeds slowly, as 

 befoi'e, and both plates were oxidized ; the negative one, of course, 

 through local action. An oxidized piece of silver acts as a negative, 

 like the plate on which oxide of silver was strewed. 



I have often been baffled while trying the effect of the rays of 

 the sun on the action of oxygen absorbing couples, chiefly, I think, 

 through the up-rising currents of water produced by the sun's rays. 

 With the above arrangement of silver audits oxide I had no difficulty 

 in obtaining the following effects : when the rays were allowed to fall 

 on the positive plate only, the indication in the galvanometer rose ; 

 when they fell on the negative plate covered with the oxide of silver, 

 and the positive side screened, the indication declined ; when both 

 plates of equal size were exposed to the solar rays, there was no de- 

 cided change. 



The following experiments on the effect of the changes of the sec- 

 tional area of the exciting fluid in a galvanic couple, had their origin 

 in some trials I made of the remarkable power of the earth for con- 

 ducting electricity, as shewn by Professors Mattuecci and Belli's 

 published results. See Phil. Mag. No. clxix, p. 540, where an 



