164 CHEMICAL DISCOVERY AND INVENTION 



attack on the problem, with the aid of the knowledge acquired 

 by a study of Van 't HofFs researches, is much to be desired, and 

 would probably lead to interesting results. 



CHAPTER X 



ELECTROLYSIS 



IT is little more than a hundred years since the decomposition 

 of water by an electric current was first seen by Nicholson and 

 Carlisle. A few years later Davy, making use of the same agency, 

 isolated potassium and sodium, and with the aid of a battery 

 consisting of 2000 plates first showed to an audience at the 

 Royal Institution the arc light between points of charcoal. 

 Faraday succeeded Davy, and within ten years after the death 

 of the latter the quantitative laws, relating to electro-chemical 

 decomposition, were established by him. The electric deposition 

 of metals from solution is the basis of the beautiful art which 

 gives to every household its silver-plated spoons and forks, and 

 supplies the means of copying with the most minute detail any 

 surface which is, or can be rendered, conductive of electricity. 

 Since the days thus briefly referred to the means of generating 

 electric currents have developed chiefly out of the discoveries of 

 Faraday. The application of the current to the production of 

 heat or motion is familiar but cannot be further described at 

 this point. The question which has occupied chemists for a 

 hundred years is what is the nature of the process of electrolysis ; 

 why does the electric current so easily decompose a solution of 

 common salt or acidified water, while it has scarcely any effect 

 on a solution of pure sugar or alcohol ? 



Around questions like these a revived discussion has raged 

 for more than twenty years, and though practical unanimity on 

 the main part of the modern theory has been reached, many 

 accessory questions have yet to be settled and probably will 

 remain unsolved for many years to come. 



First of all it will be useful to recall the hypothesis which was 

 accepted for the greater part of the nineteenth century. It will 

 be the easier to perceive the profound nature of the change 

 which has been introduced. Imagine, for example, that a 

 solution of hydrochloric acid is submitted to the action of a 



