722 



aCIENGE. 



[N. S. Vol. VIII. No. 204. 



subject made by Adam and Eve in the 

 Garden of Eden, it is certain that the phil- 

 osophers and alchemists were as much in- 

 terested in those phenomena which lie on 

 the border-line between physics and chem- 

 istry as in those which were purely physical 

 or chemical. Indeed, the sharp line be- 

 tween the two subjects, drawn with so 

 much emphasis twenty or thirty years ago, 

 did not then exist. It is interesting to note 

 that this sharp line is now rapidly being 

 erased ; we are realizing more and more 

 that the laws which govern one class of 

 phenomena are applicable also to the other. 

 Thus the cosmic working of the mind of 

 man swings back and forth ; will it ever 

 come to rest upon the absolute truth ? 



In the middle of the seventeenth cen- 

 tury, while this country was in an infantile 

 condition, and Harvard College was little 

 more than embryonic, Kobert Boyle dis- 

 covered his law relating to the contraction 

 of gases under pressure — one of our most 

 fundamental conceptions to-day. Lavoisier, 

 before his tragic death in the Eeign of Ter- 

 ror, forced upon a somewhat reluctant 

 world the idea of the conservation of mass 

 — an idea which perhaps had been half as- 

 sumed by some before — and in so doing 

 laid a corner- stone of the great structure 

 which was to follow. Only a few years 

 later, Dalton, Avogadro, Ampere, Gay-Lus- 

 sac, Dulong and Petit, Davy and Faraday, 

 that prince of pioneers, with others less fa- 

 mous, made great additions to the world's 

 thought in a phj'sico-chemical direction. 

 As far back as our forties Julius Robert 

 Mayer and Helmholtz had acquired a clear 

 grasp of the conservation of energy, while 

 the other great law of energy had been par- 

 tially realized by Sadi-Carnot two decades 

 before. Hittorf's classical research on elec- 

 trolytic conductivity, and Wilhelmy's epoch- 

 making study of the speed of a reaction, 

 a research upon the lines laid down by 

 Wenzel and Berthollet so much earlier, 



took place over forty years ago. Only a dec- 

 ade later Guldberg and Waage laid down, 

 in unequivocal and comprehensive terms, 

 the fundamental law of mass-action, which is 

 the basis of Wenzel's, Berthollet's and Wil- 

 helmy's observations, as well as of the prog- 

 ress and equilibrium of every other chem- 

 ical change. 



Why, then, with these foundations laid 

 so far in the past, are we inclined to call 

 physical chemistry a brand-new structure ? 



We all know that a part at least of the 

 retarded development was due to the diffi- 

 culty of dealing with solutions, which / 

 seemed anomalous in so many ways. Van't ^ 

 Hoff, by showing that a substance in solu- 

 tion followed many of the laws Avhich 

 would govern it in the aeriform state, and 

 Arrhenius, by explaining, in a simple way, 

 the differences between solutions conducting 

 electricity and those which are non-con- 

 ductors, cleared the track of these obstruc- 

 tions ; hence, for the last ten years the pace 

 has been rapid. But it seems to me that 

 there is another reason for the tardiness of 

 the recognition of the importance of phys- 

 ical chemistry to be found in an unfortunate 

 tendency observable sometimes in both 

 chemists and physicists, a tendency which 

 I am afraid we must call prejudice. Not 

 only have untenable theories been held long 

 after their time, but whole fields of study 

 have been neglected by most chemists and 

 physicists, because they lie on the border- 

 line between the two sciences. 



The average physicist only half realized 

 that one of the most important relations of 

 his great new force, electricity, is chemical, 

 while the chemist does not always realize, 

 even to this day, that Wheatstone's bridge 

 and the telephone are chemical tools just as 

 legitimate as, and no more ' physical ' than 

 the thermometer, or the time-honored bal- 

 ance, which extricated his predecessors from 

 so hopeless a slough a hundred j'ears ago. 

 The day is fast approaching, however, when 



