REVIEWS 571 



more of the topics of intermolecular linkage, interatomic linkage, and the intra- 

 atomic origins of these. The last variety is best left to the physicist to elaborate ; 

 inorganic chemists are striving with the first, but it is from organic chemistry 

 that we derive most light both on this and on interatomic linkage. 



Most of the first chapters of the book, and the first fifty pages of the second, 

 deal with unsaturated carbon. The student who can think for himself will be 

 both stimulated and provoked into doing so as he reads this part of the work ; 

 he will be stimulated by several very lucid accounts such as that of Thiele's views 

 on double linking, and he will be provoked into thinking for himself by the 

 absence of more than a slight correlation between the divers theories. This is 

 due rather to the present condition of the subject itself than to faults of treatment, 

 and although one could wish for more blending of the theories than the author 

 has shown, the fact stands out that the day of the all-embracing theory is 

 not yet. 



Broadly speaking, there are two views respecting the nature of unsaturated 

 carbon atoms, of which one is that the atoms are in a "carbonous" state of 

 di- or of trivalency. In Chapter I. is to be found a survey of the work of Nef 

 and others on divalent carbon, which is clear and concise. The controversial 

 topic of triphenylmethyl is impartially reviewed ; but it is not clear why the 

 existence of ions of triphenylmethyl in solution should imply the existence 

 of molecules of the single radicle, nor is the probability of union with the solvent 

 pointed out. In passing, attention may be directed to a misprinted equation on 

 p. 7. Hinrichsen's and Thorpe's extensions of the " carbonous " idea to ethylenic 

 compounds are well treated. In the first portion of Chapter II. the nature of 

 addition and substitution processes is discussed ; and here we meet the second 

 kind of idea of unsaturation, that of partial valencies, which lies at the root of 

 many hypotheses besides Thiele's. The whole section is an interesting one, and 

 the author's criticisms are valuable. 



Then follows a section devoted to "dry" catalytic actions such as those of 

 Sabatier and Senderens. This is perhaps a digression, dealing, as it does, 

 for the most part with practical methods and results ; but it is followed by the 

 best part of the book, namely, that on chain and ring formation. This is really 

 a revision and amplification of the chapter on Condensation in Vol. I., and 

 without doubt the improvements justify its inclusion here. The simple classi- 

 fication of condensations which the author introduces on pp. 109-10 will 

 greatly help the student to cope with this huge subject, and the historical mode 

 of treatment adopted at the same time is of much educational value. The only 

 criticism which is called for is that, in discussing " Grignard " reactions, the 

 author might have taken the opportunity to abandon the usual text-book basis of 

 treatment, which regards Grignard reagents merely as useful aids in preparing 

 otherwise difficultly obtainable compounds. All applications of these reagents 

 fall under one or other of two headings — double decomposition, or addition 

 followed by hydrolysis or other suitable double decomposition ; and some such 

 treatment as this, perhaps in connection with Lapworth's views, would have been 

 welcome. 



Coming to the third chapter ("The Dynamics of Organic Reactions"), written 

 by Dr. H. M. Dawson, the reader must readjust his standpoint ; in fact, excellent 

 though the chapter is, it is not quite in harmony with the rest of the book. Here 

 again, however, the fault lies with the subject and less with the author ; for 

 dynamical studies in organic chemistry have not yet fulfilled their early promise, 

 except in comparatively few cases of systematic researches. This being so, the 



