164 SCIENCE PROGRESS 



account of the theory and technique of X-ray work. Very few investigations 

 bearing on the theoretical aspects of the subject have been carried out since the 

 previous edition was published, and from this point of view the changes are few 

 and far between. There is now a full description of Rutherford's and Andrade's 

 experiments on the reflexion of y-rays ; a short reference to the application of the 

 quantum theory to the nature of the rays, and an account of Barnes's, Rutherford's, 

 and Richardson's work on the absorption of X-rays from a Coolidge tube by 

 aluminium. On the technical side, however, there are notable additions in the 

 descriptions of new forms of apparatus, and an entirely new chapter on X-ray 

 equipment and technique written by Mr. W. F. Higgins, who is responsible for 

 much of the X-ray equipment at the National Physical Laboratory. This section 

 contains a full account of the arrangement and use of the apparatus required for 

 a modern X-ray installation, and has been added mainly to meet the needs of 

 hospital workers who would find it difficult to pick out for themselves the practical 

 hints scattered throughout the book. The recommendations for the protection of 

 X-ray operators, issued by the Rontgen Society, have been printed as an appendix. 

 The index remains, as before, a model of its kind. 



D. O. W. 

 CHEMISTRY 



A Text-Book of Thermo-chemistry and Thermodynamics. By Prof. Otto 

 SACKUR, Ph.D. Translated by G. E. Gibson, Ph.D. [Pp. xvi + 439, with 

 44 illustrations.] (London : Macmillan & Co., 1917. Price 12s. net.) 



The recognition which chemistry has received as a result of the events of the past 

 two years is one of the most important matters with which the chemist himself has 

 to deal. What is true of chemistry as a whole is equally true of that important, 

 and indeed fundamental, part of it which we call physical chemistry. At such a 

 time, any worthy contribution to the literature of physical chemistry, which helps 

 to bring into prominence its essential significance for both pure and applied 

 science, is particularly welcome. In the late Prof. Sackur's book we find such a 

 contribution. The author's point of view is clearly expressed in the opening 

 sentence : " Everyone will admit that a thorough understanding of physical 

 chemistry, and of the success of its applications in science and in technology, can 

 only be obtained on the basis of thermodynamics." The book itself is a com- 

 mentary on that statement, which will bring conviction to any serious student. 



Perhaps the most striking feature of the book is its clearness. Admittedly the 

 subject is a profound one, taking us down to principles and laws which underlie 

 all chemical processes. Prof. Sackur does not hesitate to bring the reader into 

 early contact with some of the most recent advances in physico-chemical thinking, 

 but the matter is put in an exceedingly lucid way. The general thermodynamical 

 considerations are never allowed to become too abstract. The student has his 

 attention called continually to the experimental material available. The effect of 

 this is to give a certain concreteness to the treatment, which is eminently desirable 

 in view of the fact that the book is a contribution to an essentially experimental 

 science. 



Coming to points of detail, one is struck by the number of very useful tables of 

 data which the book contains, data which serve to illustrate the conclusions 

 arrived at. Certain subjects are particularly well treated, e.g., liquid mixtures 

 and fractional distillation, the deduction of the law of mass action, Helmholtz's 

 theory of the E.M.F. of a cell, and the proof of the Stefan radiation law. 



Dr. Gibson is to be congratulated on the excellence of the translation. 



\V. C. McC. Lewis. 



