It will be noted that amongst the entries cited above there are two of absolutely capital importance, one foreshadowing the great discovery of magneto-electric induction, the other indicating how the existence of electro-optical relations was shaping itself as a possibility in Faraday’s mind. An entry in his laboratory book of September 10 is of great interest:—
Polarised a ray of lamp-light by reflection, and endeavoured to ascertain whether any depolarising action [is] exerted on it by water placed between the poles of a voltaic battery in a glass cistern; one Wollaston’s trough used; the fluids decomposed were pure water, weak solution of sulphate of soda, and strong sulphuric acid: none of them had any effect on the polarised light, either when out of or in the voltaic circuit, so that no particular arrangement of particles could be ascertained in this way.
AN UNSUCCESSFUL EXPERIMENT.
It may be added that no such optical effect of electrolytic conduction as that here looked for has yet been discovered. The experiment, unsuccessful at that day, remains still an unsuccessful one. A singular interest attaches to it, however, and it was repeated several times by Faraday in subsequent years, in hope of some results.
In 1823 Faraday read two papers to the Royal Society, one on Liquid Chlorine, the other on the Condensation of several Gases into Liquids. No sooner was the work completed than he dashed off a letter to De la Rive to tell him what he had accomplished. Under date March 24, 1823, he writes:—
I have been at work lately, and obtained results which I hope you will approve of. I have been interrupted twice in the course of experiments by explosions, both in the course of eight days—one burnt my eyes, the other cut them; but fortunately escaped with slight injury only in both cases, and am now nearly well. During the winter I took the opportunity of examining the hydrate of chlorine, and analysing it; the results, which are not very important, will appear in the next number of the Quarterly Journal, over which I have no influence. Sir H. Davy, on seeing my paper, suggested to me to work with it under pressure, and see what would happen by heat, &c. Accordingly I enclosed it in a glass tube hermetically sealed, heated it, obtained a change in the substance, and a separation into two different fluids; and upon further examination I found that the chlorine and water had separated from each other, and the chlorine gas, not being able to escape, had condensed into the liquid form. To prove that it contained no water, I dried some chlorine gas, introduced it into a long tube, condensed it, and then cooled the tube, and again obtained fluid chlorine. Hence what is called chlorine gas is the vapour of a fluid....
* * * * *
I expect to be able to reduce many other gases to the liquid form, and promise myself the pleasure of writing you about them. I hope you will honour me with a letter soon.
I am, dear Sir, very faithfully, your obedient servant,
M. Faraday.