Faraday to Edward Daniel Clarke   19 September 1816

Royal Institution Sept 19th 1816

Sir

I have just received your letter of yesterday and hesitate not a moment in writing scarcely an answer to it but an acknowledgement of it. Indeed your Queries appear to be such as can only be answered by experimental investigations for I am not aware of any information that can be quoted i.e. drawn from ascertained knowledge that can apply to them though as my small stock of chemical knowledge necessarily leaves untouched many important branches it is very probable that answers to your queries may be known to some though unknown to me.

As however Sir I judge from the import of your communication you expect an answer from me I shall venture a few observations on the subject. - It has been my intention for some time past to repeat some of your experiments but I have not yet procured a blow pipe from Mr. Newman and have therefore been obliged to defer them. Not having seen the experiments it is possible I may make a wrong judgement of them for there are many little circumstances & changes which arise in the progress of an experiment which materially assist us in forming a conclusion.

Allowing that charcoal causes the vitrification of metals it is evident that it must be owing either to a change in the state of the metal or to the decomposition of the metal a vitrifiable body being left or to a combination of the metal with some other substance forming a vitrifiable compound[.] Not having seen the experiments I have not sufficient means of judging since effects may have been produced in them which are new but reasoning from the habits of the metals as I have met with them I should not think that the pure metal was vitrified or decomposed by the powers you have applied to it and it then follows that it has combined with some thing. It strikes me that you have formed a carburet & if that is the case that carburet may be vitrifiable though the pure metal is not. I have often thought on the probable changes which charcoal might undergo at the heat you possess the means of procuring if its combination with oxygene could be hindered. In some experiments made with the powerful voltaic apparatus here there were apparently evidences of its volatilization when acted on in vacuo and we can scarcely entertain a doubt of its fusibility at some temperature and if we had never seen carbon as charcoal we should not have been much surprised at the idea of diamond forming with metals vitrifiable substances. Carbon has something peculiar in its combinations. It exists but in small proportions in steel yet causes a great change in the properties of the iron combined with it[.] It exists in extraordingly [sic] high proportion in plumbago yet still leaves it possessed of many metallic characters. I find nothing difficult in the idea of believing that it may form with the earthy metals a vitrifiable compound[.]

It is difficult to form an opinion on your second query without knowing every circumstance of the case and they can only be properly ascertained by the operator. The presence of extraneous substances the vitrification before spoken of the more or less perfect reduction & many other circumstances may be present & exert a very extensive influence if the metal which presents those changeable appearances is capable of being vitrified without the addition of other substances than are present then there is strong reason to believe that the variable approaches to this state cause the appearances.

I must however Sir beg your pardon for troubling you with matter so unimportant and so far removed in its nature from [that] which you required but I can only present in excuse my ignorance of those particular facts and indeed of science in general[.]

I am Sir With great respect | Your Obedient Humble Servant | M. Faraday

Address: Revd. Dr. Clarke, Professor of Mineralogy, &c &c &c, Cambridge