Chemistry and Physics. 93 



The increase in the atomic weight seems very small when it 

 is considered that Harkins supposes the heavier isotope to have 

 the atomic weight 37.00, but it appears that the small increase is 

 a definite one, and the authors say that this seems to be the first 

 separation of isotopes reported from which there is any definite 

 evidence. 



The work on the diffusion of chlorine and hydrogen chloride 

 was begun in 1915, and Harkins has been aided by several 

 co-workers in the investigation. Several previous announce- 

 ments of successful results have also been made previously. — ■ 

 Jour. Amer. Chem. Soc, 43, 1803. h. l. w. 



3. Qualitative Chemical Analysis; by Olin Freeman Tower. 

 8vo, pp. 89. Philadelphia, 1921 (P. Blakiston's Son & Co. 

 Price, $1.50 net). — This is the fourth edition, revised, of a labora- 

 tory manual for use in inorganic qualitative analysis. It gives 

 unusually clear and full directions, together with numerous 

 explanatory notes, in connection with the analytical processes. 

 While many teachers of qualitative analysis use the course as an 

 opportunity to give a thorough drill in the writing of chemical 

 equations, the author of this book does not appear to favor such 

 a plan, for, besides a few equations given in the theoretical intro- 

 duction, scarcely any others are given, although the chemical 

 formulas of products formed in the operations are mentioned. 

 In connection with descriptive matter the student is frequently 

 given references to text-books of general chemistry. 



In conclusion it may be said that the book gives a very good 

 course of analysis, with well-selected methods very satisfactorily 

 presented. h. l. w. 



4. A Course of Instruction in Quantitative Chemical Analy- 

 sis; by George McPhael Smith. 8vo, pp. 218. New York, 

 1921 (The Macmillan Company). — This is a revised edition of 

 a work which first appeared about two years ago. It presents a 

 course of laboratory work for beginners in the subject, with very 

 full and clear directions, copious explanatory notes, and an excel- 

 lent list of questions. There are also 100 analytical problems 

 without answers, equally divided between gravimetric and vol- 

 umetric analysis. 



The book in general gives a very good impression, but it is 

 unfortunate that it teaches a slow and difficult method of weigh- 

 ing, including the finding of the "rest-point" of the balance by 

 the use of long swings. This is likely to discourage the beginner 

 and to handicap him greatly in his subsequent analytical work. 

 It is far easier and quicker, as well as decidedly more accurate to 

 employ the shortest swings that can be seen readily, and to use 

 the center of the graduated scale as the basis, since any deviation 

 from equilibrium in the balance is eliminated in the practically 

 invariable practice of weighing by difference. H. l. w. 



