RECENT SCIENCE. 815 



It is not possible to describe in a few words the impetus given 

 by tbe discovery of these connections to physico-chemical re- 

 search altogether. A school, headed by Ostwald, of most enthusi- 

 astic supporters of what has been termed (not quite properly) the 

 physical theory of solutions, has grown up ; and this school, 

 while bringing out a mass of important researches and widening 

 the field of chemical investigations, has naturally come to con- 

 sider itself as being on the right track for elaborating a complete 

 theory of the subject. Unhappily, this is not the case, because 

 the chemical reactions which undoubtedly take place in solutions 

 are not taken into account in the just-mentioned physical laws. 

 In reality, so long as but small amounts of solids, or liquids, or 

 gases are dissolved in a liquid, and so long as only such bodies 

 are brought into contact as have no strong chemical affinity for 

 each other, the above theories are quite correct. But as soon as 

 the solution is rendered stronger, or the solvent and the dissolved 

 body are endowed with a mutual chemical affinity, chemical reac- 

 tions set in. Part of the molecules of the dissolved body disso- 

 ciate, and the atoms of which they were composed, on being set 

 free, combine with the atoms of the solvent. Chemical forces, 

 much more energetic than the physical forces, enter into play, 

 and most complicated chemical reactions the intensity of which 

 may be judged of from the changes of temperature begin. To 

 deny them is simply impossible, although this has been done in 

 the excitement of polemics. The chemical reactions which take 

 place within the solutions, and especially the formation of defi- 

 nite though unstable compounds of salts, acids, and bases with 

 water, have been rendered evident by so many careful investiga- 

 tions of experienced chemists,* that the secondary importance 

 given to them by most adherents of the physical theory would be 

 simply incomprehensible were it not for the hope which they 

 cherish of ultimately explaining all chemical processes by the 

 above-mentioned molecular movements. At any rate, in order to 

 account for the effects of the chemical reactions, the followers of 

 the physical theory were compelled to seek support in an addi- 

 tional agency electricity. Starting from the familiar fact of 

 solutions being decomposed by an electrical current, they ad- 

 mitted that in every solution part of its molecules dissociate, 

 breaking up into their component parts, which are charged with 

 either positive or negative electricity (the name of " ions " is usu- 

 ally given to those component parts). By means of this admis- 

 sion, they attempted to explain the discrepancies between observa- 

 tion and the conclusions drawn from the above-mentioned laws, 



* We need only mention the names of Armstrong, Etard, Pickering, Mendeleeff, and 

 so on. 



