372 Messrs. C. R. A. Wright and C. Thompson. [June 20, 



XVII. "Note on the Development of Voltaic Electricity by 

 Atmospheric Oxidation of combustible Gases and other 

 Substances." By C. R. Alder Wright, D.So., F.R.S., 

 Lecturer on Chemistry and Physics, and C. THOMPSON, 

 F.I.C., F.C.S., Demonstrator of Chemistry, in St. Mary's 

 Hospital Medical School. Received June 20, 1889. 



About fourteen months ago we had the honour of communicating 

 to the Society (' Roy. Soc. Proc.,'vol. 44, p. 182) the results of a large 

 number of experiments made with electromotor cells, of which a 

 special feature was that one of the plates of the combination consisted 

 of an "aeration plate," or layer of conducting material exposed to the 

 atmosphere, and consequently superficially charged with a film of 

 condensed air, which served as a means of indirectly effecting the 

 oxidation of the other plate (when made of oxidisable metal), or of 

 the fluid surrounding it (when the plate is of non-oxidisable material 

 immersed in an oxidisable fluid). We showed that the E.M.F. of a 

 given combination varies very considerably with the nature of the 

 material of which the aeration plate is made, surfaces of platinum 

 sponge, and especially platinum black, yielding the highest results 

 when the electrolyte is dilute sulphuric acid; a convenient way of 

 constructing the plates being to apply the spongy metal to the surface 

 of unglazed earthenware, or other similar porous non-conducting 

 material, so as to form a conducting film, the electrolytic fluid being 

 absorbed in the porous material and so making contact. We also 

 found that the substitution of pure oxygen for air only increased the 

 E.M.F. by inconsiderable amounts, and that somewhat analogous cells 

 are obtainable by employing combustible gases, e.g., hydrogen, to sur- 

 round the aeration plate, the opposed plate being either an incorrodible 

 one immersed in a fluid capable of supplying oxygen (permanganate or 

 chromic acid solution, nitric acid, &c), or one itself capable of parting 

 with oxygen (compressed lead peroxide, &c). By employing two 

 aeration piates, one in contact with the air and one with the oxidis- 

 able gas, a form of gas battery was obtained which, like all other gas 

 batteries, furnished a current considerably less powerful than that 

 due to the chemical action taking place, even under the most favour- 

 able conditions. 



The most convenient form of simple cell of this class examined by 

 us consisted of a thin plate of unglazed earthenware, such as that 

 used for the porous pots of a Grove's battery, both sides of which 

 were coated over with spongy platinum to within a short distance of 

 he edges, contact being made by means of thin strips of platinum 

 foil pressed against the coated earthenware by means of the clamping 



