-884 



SCIENCE. 



[N. S. Vol. XV. No. 388. 



kinetic theory of ga.ses, and his theory of 

 electrolysis is derived from an application 

 to solutions of the ideas involved in this 

 kinetic theory. He supposes that the 

 molecules of the electrolyte move through 

 the solution as the molecules of a gas move, 

 that they collide with one another as the. 

 gas molecules do, and that it must happen 

 that here and there ions get separated and 

 remain separated for a time, cation again 

 uniting with anion when two of them meet 

 under favorable conditions. There will thus 

 always be some detached ions moving about 

 just as molecules do. They will not always 

 be the same ions that are thus detached, 

 and a very small i^roportion of such loose 

 ions will suffice to explain the phenomena. 

 These loose ions retain in their separate 

 condition the charges of electricity which 

 they had when united, the cations being 

 positively and the anions negatively 

 charged. This is assumed to be the state 

 of matters in any solution of an electrolyte. 

 If now into such a solution we place two 

 electrodes with any, however small, differ- 

 ence of potential, the cathode, being nega- 

 tive, will exercise an attraction upon the 

 positively charged cations, and the positive 

 anode will exercise a similar attraction on 

 the negatively charged anions, and thus 

 the loose ions, which before the introduc- 

 tion of the electrodes moved about in the 

 liquid with no definite preferred direction, 

 will on the whole, now that the electrodes 

 have been introduced, move preferably, the 

 cations towards the cathode, and the anions 

 towards the anode, and those ■ which are 

 near the electrodes will be drawn to them 

 and discharge their electric charge. This 

 theory seems therefore to explain the phe- 

 nomena. The essential difference between 

 it and all previous theories is that Clausius 

 does not attribute the decomposition to the 

 current or to the attraction of the elec- 

 trodes ; what the attraction of the electrodes 

 does is to separate the ions already dis- 



engaged from one another, and this the 

 smallest electromotive force can do. The 

 theory is so far adequate, but is it ad- 

 missible? Can we suppose that hydrogen 

 and chlorine atoms can move uncombined 

 through the solution? It is to be noted 

 that while Clausius does not give any 

 opinion as to the proportion of loose ions 

 to the total ions in any case, he assumes that 

 this proportion increases as the tempera- 

 ture rises, on account of the greater brisk- 

 ness of the movements of the particles, and 

 points out that this is in accordance with 

 the fact that electrolytes conduct better as 

 the temperature is liigher. But he says, 

 'to explain the conduction of the electricity 

 it is sufficient that in the encounters of the 

 molecules an exchange of ions should take 

 place here and there, and perhaps com- 

 paratively rarely.' 



In this connection we may look at the 

 views expressed by Williamson in his paper 

 on the theory of etherification.* He says : 

 "We are thus forced to admit that in an 

 aggregate of molecules of anj^ compound 

 there is an exchange constantly going on 

 between the elements which are contained 

 in it. For instance, a drop of hydrochloric 

 acid being supposed to be made up of a 

 great number of molecules of the composi- 

 tion CIH, the proposition at which we have 

 just arrived would lead us to believe that 

 each atom of hydrogen does not remain 

 quietly in juxtaposition with the atom of 

 chlorine with which it first united, but, on 

 the contrary, is constantly changing places 

 with other atoms of hydrogen, or, what is 

 the same thing, changing chlorine. " Wil- 

 liamson founded this opinion on the ob- 

 served facts of double decomposition. He 

 made no application of this view to the 

 case of electrolysis, and indeed does not 

 explicitly mention the temporary detach- 

 ment of the atoms during the process of ex- 



* Williani.soii, Chein. Soc. Journ., TV., p. Ill 

 (18o2). 



