538 



SCIENCE. 



[N. S. Vol. XV. No. 379. 



The classification according to components 

 and degrees of freedom is known as the phase- 

 rule classification. It is broad enough to in- 

 clude all facts pertaining to equilibrium and 

 yet clearly enough defined so that everything 

 has its own place. It is therefore an ideal 

 classification, or perhaps the ideal classifica- 

 tion for chemical equilibrium. It is more 

 comprehensive than the periodic law or con- 

 stitution formulas, and chemistry as a whole 

 will some day be presented from this point of 

 view. The phase rule is to the science of 

 chemistry what the steel frame is to a build- 

 ing, the periodic law, constitution formulas, 

 the mass law, the laws of electrochemistry, 

 etc., being the brick walls. Just as we can 

 build a small building safely of bricks and 

 wood, while the steel construction is the only 

 wise one for a sky scraper, so we have man- 

 aged to get along satisfactorily hitherto with- 

 out the phase-rule classification ; but the rapid 

 development of quantitative chemistry neces- 

 sitates a new arrangement. 



The book by Professor Eoozeboom does not 

 claim to revolutionize chemistry in the man- 

 ner just outlined. Our ignorance is still too 

 great to permit such a scheme being carried 

 through to-day, though the direction in which 

 we are tending and must tend is very clear. 

 This book deals chiefly with the qualitative 

 side of equilibrium and this first volume with 

 systems containing one component only. It 

 is, however, a conscious and deliberate step in 

 the direction of the goal I have indicated and 

 no one is better qualified to take this step 

 than Roozeboom. We owe the phase rule to 

 Gibbs; but it was Roozeboom who brought 

 out the significance of it; who changed it 

 from an interesting but apparently unimpor- 

 tant mathematical generalization to the safe 

 guide in all matters of equilibrium and to 

 the future basis of systematic chemistry. In 

 this first volume the author begins with the 

 discussion of the boundary curves for liquid 

 and vapor, solid and vapor, solid and liquid. 

 The triple point at the intersection of these 

 three curves is next considered. We then 

 pass back to the equilibrium between two 

 stable solid phases and to the triple point with 

 solid, solid and vapor in equilibrium. A 



chajjter on flowing crystals follows, in which 

 it is shown that these are properly to be con- 

 sidered as a solid phase and that the first in- 

 version point is one for solid, solid and vapor. 

 Next comes a chapter on instable triple points 

 in the case of enantiotropic systems, and then 

 one on the behavior of monotropic substances. 

 The volume closes with a chapter on the triple 

 point, solid, solid liquid; one on the triple 

 point, solid, solid, solid; and a final chapter 

 in which the general question of uniform and 

 non-uniform pressure is considered. 



Wilder D. Baxckoft. 



Die wissenschaftlichen Grundlagen der analy- 

 tischen Ghemie, elementar dargestellt. Von 

 W. OsTWALD. Dritte, vermehrte Auflage. 

 Leipzig, Wilhelm Engelmann. 1901. 13x21 

 cm. Pp. xi-|-221. Price, bound, 7 Marks. 

 The book is divided into two nearly equal 

 parts, the first containing general theory and 

 the second the application. The first chapter 

 deals with the conditions for recogTiizing a 

 substance and might well have been fuller. 

 AVhen two or more properties of two sub- 

 stances coincide, the other properties usually 

 do and the substances are identical. This is 

 true, but not complete. For instance, the con- 

 verse does not follow. We can have sub- 

 stances, notably some of the radio-active sub- 

 stances where certain properties can differ 

 markedly and yet the two substances be the 

 same from a chemical point of view. This 

 raises the question as to what properties, if 

 any, are to be considered fundamental. 



The second chapter gives the methods of 

 mechanical separation, together with the 

 theory of washing a precipitate. The third 

 chapter treats of separation by distillation or 

 solution. The fourth chapter is devoted to 

 the electrolytic dissociation theory and the 

 fifth to the question of measurement. In the 

 second portion of the book the author takes 

 up the different elements in the usual analyt- 

 ical groups and discusses them. In an ap- 

 pendix are given a number of interesting 

 lecture experiments. 



The opinion one forms of this book will 

 depend on one's point of view. If one looks 

 upon it as a book for those beginning analyt- 



