Faraday to Charles Babbage   22 September 1831

Royal Institution | Septr 22 1831

My dear Sir

I returned to town only yesterday and hasten to answer your letter[.]

The number for Bromine in uncertain. Balard¹ made it 9.326². - Liebig³ 9.411⁴. Berzelius nearly 9.94⁵. Oxygen being 1. I have no experiment of my own to quote but knowing the general accuracy of Berzelius in experiment I should trust him most[.]

Chlorine. I believe to be 36. Hydrogen being 1. i.e. 4 1/2 oxygen being 1. Such is the result of my experiments on former occasion[s] as well as of other persons and I know of no reason at present to doubt it[.]

Iodine judging of its number from Expt (analytical) only doubt would hang about it[.] Berzelius makes it nearly 16.06. Gay Lussac 16.2 & Prout⁶ 16.473. I have no quantitative experiment to quote. I made many formerly with Sir H. Davy but have not the notes. He had them[.] The number 15.8 is perhaps a mean of results deduced from the S.G of its vapour & of hydriodic acid[.]

I am not aware of any thing specific which Serullas⁷ has done relating to solid liquid & gasiform bi-carbonated hydrogen. Having done a little myself that way I should be glad to be referred to any views of that clever & active chemist[.]

I am | Dear Sir | Very Truly Yours | M. Faraday

Charles Babbage Esq | &c &c &c

Address: Charles Babbage | &c &c | Dorset Street Manchester Square