602 



SCIENCE. 



[X. S. Vol. IX. No. 226. 



indicate, in a rough way, the actual rela- 

 tions of the atoms in space ; j'et, with all 

 this, a most important part of the problem 

 has been almost neglected. To use a bio- 

 logical expression, chemistry has been enor- 

 mously developed on the morphological, 

 and but little on the physiological side. 

 Chemists have concerned tliemsel ves greatly 

 with the products of chemical reactions, and 

 but little with the nature of the reactions 

 themselves. The molecule has been treated 

 as a dead, rigid body is treated by the 

 anatomist, hut its study as a living, moving 

 mass, filled with energy and capable of re- 

 acting by virtue of this energy, has been 

 largely left to the future. Even as late as 

 1882 the German physiologist Emil du 

 Bois -Reymond used the words which have 

 since been in the mouth of every physical 

 chemist : 



" In contradistinction to modern chem- 

 istry, we maj' call pliysical chemisti'y the 

 chemistry of the future." 



Since 1882, thanks to the labors and in- 

 spiring influence of Ostwald, van't Hoff, 

 Arrhenius, Nernst and others, physical 

 chemistry is no longer the chemistry of the 

 future merel}', but of the present, and apart 

 from the quickening influence which it is 

 exerting in nearly all branches of chemistry 

 proper, both pure and applied, we aie be- 

 ginning to perceive tliat we are entering a 

 period in which chemistry will be of greater 

 service to tlie allied sciences. Geological 

 chemistry is showing signs of reviving un- 

 der the stimulus of physico-chemical con- 

 ceptions, and we are finding, too, that as 

 physiological chemistry is not merely the 

 chemistry of sugar, or urea, or albumin, 

 but preeminently a science of moving and 

 ■changing molecules, it can only progress by 

 the aid of a knowledge of the laws of chem- 

 ical en erg}'. 



The achievements of physical chemistry 

 f<trm, perhaps, the most interesting phase of 

 the recent history of our science, but its 



followers have spoken for themselves so 

 often of late years, and have presented the 

 subject so much better than I could do it, 

 that I feel compelled to consider a perhaps 

 humbler, but j^et not unimportant, field of 

 research, which, in a sense, may also be 

 called a part of the chemistry of the future, 

 the field of Inorganic Chemistry. The rela- 

 tions of phj'sical and inorganic chemistry 

 have recently been discussed by van't Hoff 

 in his admirable address delivered last 

 summer before the Society of German 

 Scientists and Physicians, and I shall, there- 

 fore, limit myself to the consideration of a 

 few points of a more strictly chemical na- 

 ture, touching the relations of physical and 

 inorganic chemistry only incidentally. 



The aim of phj'sical chemistrj' will have 

 been accampliahed when it has established 

 a mathematical equation which, by proper 

 substitution, will enable us to predict the 

 nature of every possible chemical system or 

 reaction, and the properties, physical and 

 chemical, of every possible element or com- 

 pound. Until he has reached this chem- 

 ical millennium, unless he will risk falling 

 into the pit which has received so many 

 philosophers in the past, the chemist must 

 continue to advance by the route by which 

 our understanding of everj' other branch of 

 physical science has been reached. Not- 

 withstanding all that physical chemistry 

 can do with this material at present in 

 hand, the experimenter miist long continue 

 to take the short cut to knowledge and find 

 out what his elements and compounds will 

 do by first actually getting them in hand, 

 by precipitation, filtration, distillation, crys- 

 tallization and the like. It may be ques- 

 tioned whether our present knowledge of 

 facts would ever suffice to enable us to pre- 

 dict, for example, a single atomic weight 

 with accuracy, or to explain that wonderful 

 relation between properties and atomic 

 weights known as the Periodic Law. A 

 few enthusiastic physical chemists have 



