October 9, 1896.] 



SCIENCE. 



511 



To review the work of Faraday in electro- 

 chemistry alone, and the influence it had 

 in the development of the more modern 

 theories, would require more time than is 

 alloted to us ; the most important contribu- 

 tion in this subject has alone been men- 

 tioned. 



In 1851 Williamson, from purely chemi- 

 cal evidence in the manner of the formation 

 of some ethers, was led to believe that in 

 solutions there is a constant interchange of 

 atoms or groups of atoms between mole- 

 cules, equivalent to dissociation and recom- 

 bination, a view differing from those previ- 

 ously held, where this condition was supposed 

 to be brought about by the action of the 

 electric current. Williamson made no ap- 

 plication of this conception to electrolysis. 



Clausius, in 1857, applying the ideas grow- 

 ing out of the Kinetic Theory to solutions, 

 points out the weaknesses of previously ad- 

 vocated theories ; he shows that Grothuss' 

 hypothesis, as well as its modifications by 

 Daniell and Faraday, are not in accord 

 with experimental results from accurate 

 measurements. He shows that the hy- 

 pothesis that the decomposition or tearing 

 apart of the groups of atoms in the mole- 

 cule by the electric forces, before transfer of 

 electricity takes place, is untenable. 



Clausius assumes that the molecules in 

 the liquid stored with energy, move with 

 varying velocities ; that collisions will occur 

 which may cause the separation of the 

 molecules into atomic groups for a short 

 time ; that during the period of separation 

 these groups cha,rged with opposite kinds 

 of electricity peculiar to the groups will, 

 under the influence of the electrode, be 

 directed towards the electrodes in their path 

 and thus become carriers of electricity ; he 

 ascribes to the liquid the conditions of disso- 

 ciation due to fortuitous impacts always oc- 

 curring, whether the solution be under the 

 influence of external electrical forces or not ; 

 that the function of the electric forces is but 



directive, the effect being, the disturbance 

 of the internal kinetic equilibrium. 



The principle of the conservation of 

 energy, developed and applied in thermody- 

 namic relations, influenced the manner of 

 looking upon and interpreting electro- 

 chemical processes. The most prominent 

 names associated with the application of 

 this great principle are Joule, Helmholtz, 

 Willard Gibbs, Thomson, Boscha, Favre 

 and others. Much attention was now given 

 to the problem : What is the cause of the 

 electromotive force? The distribution of 

 the energy in the electric circuit, including 

 battery, electrolytic cell and conductors, 

 was investigated in the light of the energy 

 concept and attacked from the mathemati- 

 cal or dynamical side. Weaknesses in 

 older theories were glaringly revealed if 

 searched in the light of this principle. The 

 dependence of the electromotive force upon 

 the entropy term in the equations was 

 shown, and its consequent variation with 

 temperature. 



The contributions of Willard Gibbs in 

 this field are the most important, though 

 scarcely appreciated; published in the Trans- 

 actions of the Connecticut Academy, 1876- 

 78, they were not very accessible and not 

 generally known. This great work antici- 

 pated the many discoveries since made ex- 

 perimentally, in a manner all but final in 

 its comprehensiveness and completeness, 

 opened out and suggested experimental in- 

 vestigations only partially undertaken and 

 beginning to be carried out to-day. Why 

 it was and is not more fully appreciated is 

 probably due to its concentration; in the 

 compass of some 300 pages and in 700 equa- 

 tions the entire subject of molecular dy- 

 namics is treated. The treatise was too rich 

 to be grasped in its day; it is only beginning 

 to be properly estimated twenty years after 

 its first appearance. 



About 1853 Hittorf quantitatively inves- 

 tigated, with great care, the change of con- 



