354 Mr. Adie's Experiments with Galvanic Couples 



these two plates, either decomposes it with the aid of oxygeil 

 in solution, or that oxygenated water forms a binary com- 

 pound, capable of acting as an electrolyte. 



The fact of iron and oxygen uniting together at ordinary 

 temperatures when moisture is present, is well known. It is 

 the office performed by the water during this union, wherein 

 lies the true ground of the theory of gas-absorbing batteries. 

 A single plate of iron exposed to water and oxygen gas, has 

 local differences on its surface which act in the same way as 

 if the iron had been in two halves and placed in a stream in 

 the manner described : the oxidation of the iron is developing 

 a voltaic current which passes through the fluid from one 

 point of the plate to another, either by a process of decompo- 

 sition and re-composition of water, or by the decomposition 

 of the compound formed by the solution of the gas in water. 



The first of these views can only be supported by holding 

 that the solution of oxygen so changes the affinities, that iron 

 with its aid can at ordinary temperatures decompose water. 

 I see no evidence sufficient to give probability to this hypo- 

 thesis, while, if the second supposition be admitted to meet 

 all the facts shown by experiment, it will establish the exist- 

 ence of an electrolyte more easily decomposed than water, 

 and as universal in nature ; and account for the very reduced 

 action of zinc and copper elements excited by pure water 

 freed from absorbed air or from oxygen gas, the active prin- 

 ciple derived from the air. 



I may here take occasion to add, that a saturated solution 

 of carbonate of potash and soda in an open cylindrical vessel 

 has so shut out the oxygen of the atmosphere from some 

 pieces of iron immersed in it, that now, after two years and 

 four months immersion, there is no rust on the surface of the 

 iron. 



The experiments with two similar pieces of zinc or of iron 

 placed in a running stream, as already described, were per- 

 formed during the cold weather of winter, with the tempera- 

 ture varying from 32° F. to 42°. On the return of a little 

 warmer weather I recommenced the experiments with iron 

 plates, from a wish to try if two similar pieces of iron could 

 be made to develope a voltaic current of the same electro- 

 motive force as that derived from a platinum and iron couple 

 excited by still water. 



A piece of iron- wire M'as cut into two equal lengths; each 

 of those was bent into the form of a flat spiral (fig. 2), and a 

 copper wire well-varnished was soldered to the iron at A, 

 for connecting the plate with a small decomposing apparatus 

 in the usual manner. 



