Robert John Kane to Faraday   26 March 1834

26th March 1834 | 28 Lower Gloucester St Dublin

Sir,

Colonel Colby having had the goodness to announce to you that I had obtained a Brown Matter possessing properties attributable only to fluorine¹ I take the liberty of submitting to you a short statement of the manner in which I had been lead to that conclusion and of the results afforded by subsequent and more accurate examination[.]

I had prepared tubes of chloride of lead and of common salt in order that the fluorine when disengaged from the fluoride of Potassium by chlorine, should be in contact with a substance on which it could not exert any action. These chlorides however melting at comparatively low temperatures I was anxious to ascertain by trial in a glass vessell, at what heat the decomposition is effected. In performing the experiment I found that the mass of chloride of potassium left in solution a Brown powder, while in the Experiment the glass tube was not much cor[r]oded and but little fumes of fluosilica acid made their appearance. This brown powder heated in a glass tube corroded it, white fumes, and a trace of oxygen were given off, and a little fluosilicate of Potash remained behind. The latter I attributed to the difficulty of separating by washing from its different solubility. The Brown powder moreover gave out chlorine with Muriatic acid and common salts, and Iodine with Hydroiodic acid and ioduret of potassium, while a fluoride remained in solution. From these circumstances I consider that its properties were such as should characterize fluorine and mentioned the above facts and my inference at a Meeting of the Royal Irish Academy. I have subsequently repeated the Experiments on a larger scale and in vessells of Earthen Ware and of Common Salt; in none of these was the brown matter develloped; it only appeared in glass vessells and on preparing a quantity proper for accurate examination, I found it to be a mixture of fluosilicate of potassium with peroxide of Lead, derived from the corroded glass.

To you alone therefore belongs the honor of having isolated that treacherous element, but though I have failed in the principal object of my researches, I have been successful in some others though of inferior interest.

When the current from 200 pair of 1 1/2 inch plates is passed through solution of Fluoride of Silver, metallic silver separates at the negative, and a Black, crystalline matter at the positive pole. This black matter contains fluorine and silver, and evidently more than 1 atom of fluorine for with muriatic acid, it gives chloride of silver & free chlorine while fluoric acid is formed.

When Bromine is digested in solution of fluoride of silver, no Bromide of silver is formed but a white matter in fine crystals separates, which contains silver and boiled with sulphuric acid in a glass gives off copious white fumes.

By the action of heat, on fluoride of silver and by passing chlorine through a solution of fluoride of silver, some very interesting effects are produced, which I hope to have the honor of describing to you in detail on some future occasion.

I am very anxious to know the nature of the train of experiments in which you are engaged on fluorine, for, judging from a passage in your letter to Colonel Colby, I believe that one matter I was about (passing a galvanic current through melted fluoride of Potassium) forms a portion of your present investigations². I shall therefore feel much favoured by any information on the subject that you shall think proper to send me and

I Remain with great Respect | Your obedient Servant | Robert J. Kane

Endorsed by Faraday: I wrote to him (11 April 1834) describing the plate tube I had used with fluoride lead³ & also telling him of the soluble & sub fluoride of silver & their changes⁴. MF