1889.] Electricity developed by Oxidation of Gases, fyc. 375 



coal, and such, like forms of comparatively cheap sources of energy, 

 but we are far from being convinced that such actions are impractic- 

 able. 



Our reason for bringing this note before the Society is that at 

 the Conversazione of the Society last night (June 19th) there was 

 exhibited by Mr. Ludwig Mond and Dr. Carl Langer an elegant and 

 compact " dry gas battery," said to have been invented by them, bat 

 substantially identical in principle with one of those experimented 

 with by ourselves some two years ago, chiefly differing in being 

 far larger and more neatly finished, and in consequence capable of 

 producing much more current than any arrangement constructed by 

 us. It consisted of a battery of fourteen double aeration plates of 

 films of platinum leaf and platinum black, supported by porous 

 material impregnated with dilute sulphuric acid ; when fed with 

 hydrogen and air, as the gases introduced into the compartments 

 formed by the parallel plates arranged in a trough or box, it furnished 

 a current powerful enough to keep alight for a long time a small 

 incandescent lamp, and was stated to be capable of giving a current 

 of 2 amperes per element, with an E.M.F. of about 0'7 volt, the total 

 effective surface of each element being 774 square centimetres. 



[Note. — Since the above was written, we have had the opportunity of 

 seeing an uncorrected proof of a paper by Mr. Mond and Dr. Langc r 

 entitled On a New Form of Gas Battery " (re'ad before the Society 

 on June 20th, 1889) in which the dry gas battery above referred to 

 is described, as well as various experiments on aeration cells ; and the 

 causes discussed which prevent the E.M.F. of such combinations from 

 being as large in practice as it theoretically ought to be, calculating 

 from the heat developed during the chemical actions taking place. 

 From the internal evidence of this paper, as well as from Mr. Mond's 

 assurances to us, we are convinced that the form of gas battery 

 described by Mr. Mond and Dr. Langer was not, as might perhaps be 

 supposed, in any way suggested to them by our previous work (with 

 which indeed they appear to have been entirely unacquainted), but 

 was arrived at by them quite independently. In this paper the 

 authors have repeated unknowingly various of our former experi- 

 ments on aeration cells, with substantially the same results, as the 

 following figures indicate, obtained with cells where the aeration 

 plates were layers of platinum sponge and black resting on porous 

 plates moistened with dilute sulphuric acid, and opposed to various 

 metals immersed in the acid. 



The theoretical values being Zinc == 2*281: Cadmium = T924: 

 Copper = 1-203. 



