816 THE POPULAR SCIENCE MONTHLY. 



especially in the case of water solutions of salts, acids, and bases, 

 and the stronger solutions altogether. It must be recognized that 

 many important relations between electrical conductivity and 

 chemical action have been brought out in this way by Arrhenius * 

 and his followers, and many discrepancies between the laws of 

 Van 't Hoff and Raoult and the observed facts have been ex- 

 plained. But it is also evident that, once a partial dissociation of 

 molecules is admitted, the whole takes a chemical aspect, and ref- 

 erence to such an unknown cause as electricity does not simplify 

 the matter. All kinds of chemical reactions take place in solu- 

 tions. Some molecules of the dissolved body simply exchange 

 their atoms in succession, while maintaining the same grouping 

 of atoms, and consequently the same chemical composition. In 

 other molecules the grouping only of the same atoms is changed, 

 and we have reactions of replacement, or isomerism. But, at the 

 same time, new and more or less stable combinations between the 

 atoms of both solvent and dissolved body take place in various 

 proportions ; double decompositions most probably occur as well ; 

 while the physical phenomena of sliding of undecomposed parti- 

 cles continue at the same time the physical movements of the 

 particles being impressed by, and acting upon, the chemical move- 

 ments of the atoms within the molecules. 



It must be confessed that neither theory has as yet succeeded 

 in following this multitude of movements and of catching the 

 moment when the movements of particles are transformed into 

 atomic movements and redistribution ; and though we may name 

 several equally important works which have been published on 

 this subject during the last twelve months, we can mention none 

 which have thrown new light on the subject, f Let us only add 

 that the subject itself has been immensely widened of late by the 

 wonderful researches of Heycock and Neville on the lowering of 

 the temperature of solidification of metals, by the addition of other 

 metals, and of Roberts- Austen upon alloys that is, metals dis- 

 solved in metals which behave very much like all aqueous solu- 

 tions. However, a new departure in this branch has been made, 

 quite recently, by Messrs. Harold Picton and S. E. Linder. They 

 studied the structure of solutions of sulphide salts which offer the 

 advantage of giving a whole series of gradations between real so- 

 lutions (that is, liquids which seem to consist of liquid particles 

 only) and such as contain extremely small particles of solid mat- 

 ter in suspension. By submitting the series to various tests, it 



* Svenska Vetenskaps Academiens Handlingar, 1863. 



j- Besides the leading chemical periodicals, an excellent analysis, by W. Nernst, of all 

 the chief work done during the year 1891, and its bearing upon the theory of solutions, will 

 be found in a chemical year-book which was started this year by Richard Meyer, the Jahr- 

 buch der Chemie. Frankfort, 1892. 



