478 SCIENCE PROGRESS 



which, if extrapolated to high temperatures, would give still another reversal 

 of the sign of Q. 



Some fifty pages are devoted to the chemistry of the nitrides and about 

 a dozen pages to active nitrogen. Our knowlegde of the nitrides is at present 

 very incomplete, but a fairly complete summary of what is known is to be 

 found in these pages. 



All through the book, full references are given to original papers and good 

 indexes are included. We can recommend the book to all who are at all 

 interested in the synthesis of ammonia or in the chemistry of the nitrides. 



R. E. Slade. 



Chemical Technology and Analysis of Oils, Fats, and Waxes. Vol. I. By 

 J. Lewkowitsch, M.A., F.I.C., edited by George H. Warburton. 

 Sixth edition, entirely rewritten and enlarged. [Pp. xviii + 682, 

 with illustrations and numerous tables.] (London : Macmillan & 

 Co., 1912. Price 365. net.) 



Although this is a standard work, necessary to all those interested in oils, 

 fats, and waxes, it is not incapable of improvement. It is to be regretted, 

 therefore, that the present volume differs so little from the previous edition 

 as to render the description " entirely rewritten " hardl}'- justifiable as applied 

 to vol. i. The editor points out that the greatest advances have been made 

 on the technological side, so that vol. ii, when it appears, may show greater 

 signs of rewriting. He considers that the purely scientific side has, during 

 the last few years, been somewhat neglected ; but it would seem that some 

 of the scientific work which has been done since the publication of the last 

 edition had been overlooked in the preparation of the present one. 



A table of melting-points of the amides, anilides, etc., of the fatty acids 

 is given, but no mention is made of the redetermination of these constants 

 by Robertson. M'Bain's work receives but a few lines, whereas much older 

 work of doubtful value takes up a disproportionate amount of space. More- 

 over, one would have thought that the prominence of explosives during 

 the past few years would have prevented the statement that nitroglycerine 

 forms the chief ingredient of almost all modern high explosives. 



The present volume could have been greatly improved by thorough revision, 

 careful selection of data, and the introduction of modern chemical concep- 

 tions ; indeed, it suffers from a complaint common to many works with an 

 established reputation. Further matter is added from time to time, but the 

 outlook and arrangement of the first edition is retained, with the result that 

 the book becomes a repository for a mass of information collected from the 

 literature presented in a very indigestible form. O. L. B. 



A Textbook o£ Practical Chemistry. By G. F. Hood, M.A., B.Sc, and 

 J. A. Carpenter, M.A. [Pp. xii + 527, with 161 illustrations.] 

 (London : J. & A. Churchill, 192 1. Price 21s. net.) 



The mison d'etre of this book is, according to the Preface, " an attempt to 

 place in the student's hands a Manual of Practical Chemistry which shall 

 be a reference-book in a convenient form " ; it aims " at giving a thorough 

 knowledge of general methods," and an " attempt has been made to indicate 

 the best methods of doing everything." By avoiding unnecessary verbiage, 

 the authors have been successful in confining a very large amount of instructive 

 and suggestive matter between the covers of the volume . Sufficient theoretical 

 explanations and notes are included to make the various experimental opera- 

 tions intelligible and to render the book very readable. References are made 

 throughout to standard textbooks, and, in many cases, to original papers. 

 The scope of the book may be reaUsed from the following brief notes on the 



