Faraday to William Vernon Harcourt   10 September 1833

Royal Institution | 10 Septr. 1833

My dear Sir

The experiments you refer to are not exactly what you say but very nearly so. I will state the principles & facts to you as shortly as I can. Every thing depends upon the very curious relation of lime, carbonic acid, and water but it is probably that for lime you may need other alkaline earths, perhaps even alkalies - & for water, certain other fluids or vapours[.] But to confine myself to lime, carbonic acid, & water. If carbonate of lime be heated the vapour of water being present it is decomposed with extreme facility the carbonic acid is evolved the lime left caustic & anhydrous . If the carbonate be heated vapour of water being absent then it is decomposed with extreme difficulty. I prepared a tube of platina foil in which was placed some very dry carbonate of lime being pulverised chalk. I prepared carbonic acid & making a gazometer of a bell glass confined by sulphuric acid instead of water put the carbonic acid into it & there left it for 24 hours that it might be perfectly dry. I then connected the platina tube with the gazometer & allowed the dry carbonic acid to pass over the lime & escape in very small quantities at the extremity the whole intention being to exclude the vapour of water or any other vapours & gases than carbonic acid[.] An oxy alcohol flame was now used to heat the platina tube & its contents & this was continued perhaps a quarter of an hour until at last one part of the tube gave way by fuzion. Yet this heat had not been sufficient to calcine the carbonate of lime[.] It came out very hard like limestone – not fuzed – but with scarcely a trace of caustic lime. When put into water an alkaline effect was produced on [word illegible] but on adding acid it was found not a fiftieth of the lime had been rendered caustic. This expt was repeated several times. On putting a drop of water into the platina tube a far lower heat was sufficient to render all the lime caustic in less than a minute[.]

I had not time to carry these expts further but think I could have fuzed carb lime by a little attention[.]

You are probably aware on the other hand that Lime & Carbonic acid will not combine at common temperatures without water is present [sic][.] I have kept dry quick lime in dry carbonic acid over mercury for months together without the least combination occurring.

I have often told lime burners of the advantag<<e>> they would gain by letting water in small quantity into the kilns or ovens[.]

Your proceedings with regard to the furnace inclosed I think all I could suggest in the first instance. I have no doubt some valuable results will come out – I have written to Dr Turner but am not quite sure he is in town¹.

I am My dear Sir | Very Truly Yours | M. Faraday

Revd W.V. Harcourt | &c &c &c

Address: Revd William V. Harcourt | &c &c &c | Bishop Thorpe | York