482 The Faraday Centenary, [June 26, 



Probably Faraday's most remarkable discovery in organic 

 chemistry was the fact that naphthalene could be dissolved by strong 

 sulphuric acid, and that when thus dissolved the solution did not 

 precipitate naphthalene on being treated with water. That enabled 

 him to prove combination between sulphuric acid and a hydrocarbon. 

 The body, which he called " sulpho-naphthalic acid," is probably the 

 first of the sulpho-acids now so largely employed in the colour 

 industry. 



Faraday's next important work was an investigation into the 

 properties of combinations of steel with other metals, in the course of 

 which he demonstrated the now well-recognised fact that an ad- 

 mixture of such minute proportions as one-five-hundredth of such 

 metals as silver, nickel, palladium, &c,, will entirely alter the 

 character of the metal. Concurrently with this, he worked on the 

 improvement of optical glass ; and it was observed that although the 

 fruits of his labours in this direction lay dormant for some time, they 

 ultimately resulted in one of his most important discoveries, namely, 

 the rotation of the plane of polarisation in the magnetic field. The 

 glass produced by Faraday by the fusion of oxide of lead with 

 boracic acid was selected by him because of its superior fluidity 

 combined with great density. (Experiments were given illustrating 

 the peculiar physical and electrical properties of the Faraday glass.) 



The next research was that on the liquefaction of gases, which, 

 although carried out by Faraday, was nevertheless done at the insti- 

 gation of Davy. Davy had discovered a substance which proved 

 to be a hydrate of chlorine, and which he found could be kept either 

 in ice or in sealed tubes. Faraday had produced a quantity of this 

 substance during the cold weather, and had made an analysis of it. 

 Davy then suggested that it should be heated in a sealed tube, and, 

 without saying what he really expected to take place, indicated that 

 one of three things would happen, namely, that it would either melt, 

 act on water, or produce liquid chlorine. The latter event happened, 

 and opened up vast possibilities, the prosecution of which Davy left 

 to Faraday. (Experiment on the liquefaction of chlorine given.) 

 The necessity of obtaining tubes strong enough to stand the pressure 

 required for the liquefaction experiments led Faraday to make investi- 

 gations at this time into the production of bottle and other glass. 



Faraday next turned his attention to researches on the electro- 

 chemical relations of bodies, crystallisation, and the action of metals 

 on light. It was in connection with the research on crystallisation 

 in 1856 that Faraday made his interesting discovery of the pheno- 

 menon of regelation, by virtue of which two portions of a piece of 

 ice, after being severed, freeze together again on being brought into 

 contact, even when the temperature of the surrounding medium is 

 higher than the freezing point of water. Although discovered by 

 Faraday, it was not until comparatively recent times that the explana- 

 tion of the phenomenon was given, and its influence on glacial 

 motion clearly established. (Experiment on regelation shown.) 



