ON THE PHYSICAL VIEW OF NATUEE. 



171 



Willard Gibbs l in America. They seem to have been the 

 first to approach the question of chemical equilibrium, 

 the result of the action of various conflicting chemical 

 forces, termed affinities, from a general comprehensive 

 point of view ; recognising that the theory then com- 

 monly adopted on the Continent the thermo-chemical 

 theory of affinity was incorrect or incomplete. This 

 theory, which had been principally elaborated by Julius 

 Thomsen in Copenhagen and by Berthelot in France, 

 was supported by the large amount of valuable ex- 

 perimental research for which we are indebted to 

 these two eminent men and their numerous followers. 



whilst chemists persisted in the ex- 

 clusive use of atomistic conceptions, 

 which, as Horstmann pointed out, 

 are of no avail in problems of that 

 nature (see Helm, ' Energetik, ' p. 

 143). 



1 More fundamental than the 

 labours of Horstmann were those of 

 Gibbs, which began with the year 

 1874, and were for a long time 

 buried in the ' Transactions of the 

 Connecticut Academy.' They were 

 known to Maxwell, but remained 

 generally unknown, partly owing 

 to their abstract nature, partly 

 to the fact that the majority of 

 Continental chemists were not 

 prepared to appreciate the mathe- 

 matical form in which his exposi- 

 tions were clothed. Previous to 

 the study of questions of chemical 

 equilibrium, Gibbs had successfully 

 developed an idea of James Thom- 

 son's viz. , the graphical represen- 

 tation of the different thermo- 

 dynamic quantities in three instead 

 of merely in two dimensions. Thom- 

 son had represented the properties 

 of a body or system by referring 

 them to volume, pressure, and tem- 

 perature. Gibbs refers them to 



volume, energy, and entropy, the 

 former quantities being always de- 

 finable by the latter, but not vice 

 versd. The advantages of this rep- 

 resentation were demonstrated to 

 English students in Maxwell's 

 ' Theory of Heat. ' In Germany it 

 was Prof. Ostwald who, by collect- 

 ing and translating the memoirs 

 of Gibbs, first made them accessible 

 to students ('Thermodynamische 

 Studien,' von Willard Gibbs, Leipzig, 

 1892). Subsequently both Ostwald 

 and Helm have done much to pro- 

 mote an understanding of Gibbs's 

 methods. See Ostwald, 'Allg. 

 Chemie,' vol. ii. part 2, p. 114, 

 &c. ; Helm, ' Grundziige der mathe- 

 matischen Chemie' (Leipzig, 1894), 

 and 'Energetik,' passim. Subse- 

 quently Gibbs also introduced the 

 very general and useful term 

 "phase" to denote the different 

 states in which a substance can 

 exist. This term denotes not only 

 such differences as were formerly 

 called in German Aggregatzustdnde, 

 but likewise conditions of dis- 

 sociation, allotropic and isomeric 

 modifications. 



