236 Mr. C. F. Varley on the Discharge of Electricity [Jan. 12, 



of bromine vapour, a portion of its fluorine being expelled and a portion 

 corroding the platinum and forming an insoluble compound of fluoride of 

 platinum and bromide of silver. In carbon boats at the same temperature 

 the whole of the silver-salt was converted into bromide, the boat being cor- 

 roded and the fluorine escaping in chemical union with the carbon. The 

 action of bromine on an aqueous solution of argentic fluoride was similar to 

 the action of chlorine. A solution of argentic fluoride yielded copious pre- 

 cipitates both with hydrobromic and bromic acids. 



Under the influence of a temperature of 200° to 600° Fahr. in closed 

 platinum vessels, iodine very slowly and incompletely decomposes argentic 

 fluoride without corroding the vessels, and produces a feeble compound of 

 argentic iodide, fluorine, and iodine, from which the two latter substances 

 are expelled at a red heat. At a red heat in platinum vessels, iodine pro- 

 duces argentic iodide, and in the presence of free argentic fluoride corrodes 

 the vessels in consequence of formation of platinic fluoride ; iodine and 

 fluorine pass away together during the reaction. In vessels of carbon at 

 the same temperature argentic iodide is formed, the vessels are corroded, 

 and a gaseous compound of fluorine and carbon is produced. By treating 

 an aqueous solution of argentic fluoride with iodine, similar results are 

 produced as with bromine and chlorine ; a similar solution yields copious 

 precipitates both with hydriodic and iodic acids. 



A mode of analysis of iodine is also fully described in the paper. A 

 known weight of iodine was dissolved in absolute alcohol, a strong solution of 

 argentic nitrate of known strength added to it, in portions at a time, with 

 stirring until the colour of iodine exactly disappeared. The mixture was 

 evaporated, the free nitric acid expelled by careful heat, and the residue 

 weighed. The residue was then heated to fusion, to convert the iodate of 

 silver into iodide, and again weighed. Two experiments of this kind yielded 

 accurate results, and the process was easy and expeditious. 



II. "Some Experiments on the Discharge of Electricity through 

 Rarefied Media and the Atmosphere." By Cromwell Fleet- 

 wood Varley. Communicated by Prof. Stokes, Sec. U.S. 

 Received October 5, 1870. 



After the labours of Mr. Gassiot, one approaches this subject with diffi- 

 dence, lest he should appear to be attempting to appropriate the glory 

 which so justly belongs to that gentleman and to Professor Grove. The 

 nature of the action inside the tube is at present involved in considerable 

 mystery, but some light is thrown upon the subject by the following 

 experiments. Before describing them, however, the author wishes to ob- 

 serve that he has seen Mr. Gassiot's last paper*, and finds that, so far 

 as regulating the strength of the current is concerned, he has been pro- 

 ceeding in a similar manner to the author. 



* Proceedings of the Koyal Society, vol. xii. p. 329. 



