590 



SCIENCE. 



[N. S. Vol. XVI. No. 406. 



development which modern physical chemis- 

 try has experienced in the past fifteen years 

 has been in very large measure due to advances 

 made in electrochemistry. The explanation 

 of the many conflieting results, such as the con- 

 ductivities of solutions, electromotive force 

 of primary cells, etc., which the modern theory 

 attempts, makes the section very interesting 

 and instructive — almost comparable to the 

 small text-book of LeBlanc. 



The chapter on photochemistry deals with 

 actiiiometry and gives the results of photo- 

 chemical measurements and an interesting 

 section on the action of the newly discovered 

 radium and polonium. The next chapter, on 

 chemical dynamics and equilibrium, has among 

 its topics the law of mass action and the phase 

 rule of Gibbs, both of which are of modern 

 development. The idea of chemical affinity 

 and activity as affected by modern theories 

 forms the theme of the final pages. 



The author is an ardent supporter of the 

 theory of electrolytic dissociation. He states 

 (p. 299) : ' We shall see that this theory is 

 fundamental if we hope to raise chemistry 

 from empiricism to the rank of an exact 

 science.' Such is the unfortunate idea which 

 pervades the work. This theory explains more 

 or less satisfactorily various phenomena con- 

 nected with dilute solutions, mainly aqueous; 

 but it is extremely unfortunate that the con- 

 centrated solutions of our daily experience are 

 ignored. So long as authors of texts on phys- 

 ical chemistry take the position that the part 

 is greater than the whole, so long will critical 

 observers be justified in declaring that the sub- 

 ject may be of theoretical importance only. 



The method of presentation calls frequently 

 for forward references which will embarrass 

 the student. The theory of electrolytic dis- 

 sociation is given before the chapter oil elec- 

 trochemistry, the law of mass action is used 

 before it is presented, critical phenomena dis- 

 cussed apart from the phase rule relation for 

 one-component systems, distillation before 

 two-component, etc. This leads to duplication, 

 examples of which are to be found in para- 

 graphs on the thermochemical and volume- 

 chemical methods. 



The discussion of the physical properties of 

 bodies even when presented historically should 

 not be restricted to relations connected with 

 constitution. An extension of this chapter to 

 include more of the properties of gases, such 

 as refractive index, viscosity, thermal and 

 electrical conductivity, etc., would be welcomed. 

 A few paragraphs indicating modern work on 

 solid solutions, isohydric solutions, fused salts, 

 decomposition voltages, alloys, velocities of 

 phase formation, false equilibria, crystalliza- 

 tion, etc., would have added materially to the 

 interest and value of the book. 



A few of the errors must be noted. Ethyl 

 alcohol and water are not separable by frac- 

 tional distillation (p. 175). All calcium salts 

 are not more soluble in cold than in hot water 

 (p. 179). The freezing-point of a solvent is 

 not always lowered on the addition of another 

 substance (p. 203). The following statements 

 are open to objection or proof : ' A eutectic is 

 the lowest freezing-mixture of two metals: a 

 cryohydrate is the lowest freezing-mixture of 

 two substances ' (p. 222) ; ' the best conductors 

 of heat energy, however, as compared with the 

 worst hardly exceed the ratio of 100 to 1 ' (p. 

 320) ; ' the potential of the normal electrode 

 is 0.56 volt,' and ' a solution has a smaller 

 vapor pressure than the pure solvent ' (p. 499). 

 There is no excuse for having given the Ost- 

 wald-Nernst proof of free ions (p. 367) nor for 

 assuming that sodium chloride and potassium 

 nitrate cannot exist together (pp. 506-508). 



In some places loose definitions or descrip- 

 tions are given, e. g., the volume of one gram 

 of hydrogen (p. 326), the silver voltameter 

 (p. 325), unit of resistance (p. 337), concen- 

 tration of zinc chloride (p. 329), etc. 



The apparatus and methods employed in the 

 laboratory are frequently described. Trans- 

 lations of pertinent sections from classical 

 papers are inserted and reference made to 

 some of the prominent contributors to the 

 science, the name of Jones not being forgot- 

 ten. 



' The book will find its public' In the 

 hands of a discriminating and very careful 

 teacher it may be of considerable value. 



H. R. Carveth. 



