REVIEWS 167 



. happening in such molecular weight measurements the author very properly insists 

 upon the necessity of examining the solid which separates out, as otherwise quite 

 erroneous conclusions may be drawn. As regards the physical properties of 

 solvents in relation to association of the solute it is pointed out that although 

 association is almost general in solvents of low dielectric constant, it is far from 

 absent when the dielectric constant is high. Thus quite a number of substances, 

 such as certain acids, phenols, amides, and anilides, are believed to be markedly 

 associated in water, a solvent of exceptionally high dielectric constant ; and again 

 it is found that those substances which are least soluble in water exhibit the 

 greatest tendency to associate. This chapter is extended by a very complete list 

 of molecular weight determinations given in the form of an appendix. 



When we come to the problem of molecular complexity in the pure liquid state 

 we enter the field of greatest uncertainty. Dr. Turner has made the best of it, 

 but the impression which remains is that our knowledge here is utterly unsatis- 

 factory. About a dozen methods which have been employed are quoted and 

 illustrated. In many cases the results are roughly concordant, in many cases they 

 are not. The methods are empirical or at best semi-empirical. The reviewer is 

 inclined to think that by paying less attention to capillary methods (with the ex- 

 ception possibly of Bennett's) and by concentrating on latent heat measurements 

 some hope of success is held out, but even here, as Dr. Turner points out, before 

 any real advance can be made we must have a clearer conception of the pheno- 

 menon of condensation. " To accumulate empirical methods of testing liquids is 

 fruitless." The chapters devoted to this subject are, however, full of suggestiveness 

 and the general review with which they include is specially important. 



Several other points might be commented upon, but enough has been said to 

 illustrate the scope and nature of the book. 



W. C. McC. Lewis. 



Directions for a Practical Course in Chemical Physiology. By W. Cramer, 

 Ph.D., D.Sc. [Pp. viii + 102. Second edition.] (London : Longmans, 

 Green & Co., 191 5. Price 3^. net.) 

 This is an essentially practical book, for, as explained in the preface, the subject- 

 matter is limited to experiments and deductions from the experiments, and is not 

 meant to supply the full and ordered information obtainable from a text-book of 

 physiological chemistry. The book is divided into three parts dealing respectively 

 with animal and vegetable tissues and fluids, digestion, and metabolism ; the 

 experiments are well chosen and instructive, and are very clearly set forth, and 

 even the complex question of the coagulation of blood has been dealt with in a 

 lucid manner. The plan adopted by the author of following the descriptions of 

 experiments by questions supposed to be answered by the student is disappointing ; 

 would it not have been better to supply the correct answers as well ?— for the 

 student who can do this for himself is not likely to be benefited much by the 

 questions, whereas the other type of student would have acquired useful instruction 



from the solution of problems which he himself was unable to solve. 



P. H. 



The Chemistry of Colloids and some Technical Applications. By W. W. 



Taylor, M.A., D.Sc. [Pp. viii + 328, with 7 illustrations.] (London : 



Edward Arnold, 1915. Price 7s. bd. net.) 

 Although much has been written about colloids, especially during the last few 

 years, some confusion still remains with regard to the true conception of the term 



