NATURE 



221 



THURSDAY, NOVEMBER 22, 1917. 



CLASS-BOOKS ON ELEMENTARY 



CHEMISTRY. 



(i) A Class-hook of Organic Chemistry. By Prof. 



J. B. Cohen. Pp. viii + 344. (London: Mac- 



millan and Co., Ltd., 1917-) Price 45. 6d. net, 



{2) Practical Chemistry for Medical Students. By 



Dr. A. C. Cumming-. With preface by Prof. 



J. Walker. Second edition. Pp. 8+165. 



(Edinburg-h : James Thin, 1917.) 



(i) "F^ESPITE the systematic basis of organic 



■L/ chemistry, it is always difficult to initiate 



students in the study of the subject, and especially 



I to g-et them to grasp the general prin- 



[ ciples of the science as a precedent to 



\ further study. The majority of elementary 



[ text-books are burdened with far too much 



[ preliminary detail of an abstract charajcter, so 



, far as the beginner is concerned, before he is 



brought into touch with the materials and methods 



of the science, with the result that he finds his 



studies lacking in interest and objective. This 



defect is very successfully avoided in Prof. Cohen's 



book. It bears, in every respect, the mark of the 



experienced teacher, and is most suitably adapted 



lo the requirements of first-year medical students 



and of senior science students in schools, for 



whom it is designed. 



The volume is divided into three parts, in the 

 first of which the principles of the subject are 

 illustrated by a detailed elementary study of ethyl 

 and methyl alcohols. By means of these examples [ 

 typical methods of experiment and investigation 

 employed in the examination of organic compounds 

 and in the determination of their structure are 

 described. A more systematic account of the chief 

 aliphatic comjjounds forms the second portion of 

 the book, which is concluded with a brief descrip- 

 tion of the more important cyclic compounds. A 

 series of practical exercises is included in each 

 section, and a set of questions appended to each 

 chapter. These exercises are well chosen, and do 

 much to keep the theoretical work within the scope 

 ■ of experimental knowledge. A few fuller explana- 

 tions of some reactions and structural relations 

 might be usefully added — for instance, in regard 

 to the acidity of aniline hydrochloride, the relation 

 of azo-colours to their mother-substance, azo- 

 hcnzene, the diazonium formula, and the proof of 

 ilic presence of the two hydroxyl groups in ali- 

 zarin. Also, in view of the book being designed 

 for the use of medical students, their interest would 

 have been stimulated by a little more specific detail 

 of the therapeutic properties of such substances as 

 salicvlic acid, salol, antifebrin, and phenacetin. 



(2) Although a course of practical chemistry for 

 midical students need not differ in character from 

 the instruction required for other students in the 

 more elementary stages of the subiect, it is advan- 

 fai^^eous if the material selected is restricted to 

 such methods of experiment and to descriptions 

 of the properties of such substances as will serve 

 NO. 2508, VOL. 100] 



as a helpful introduction to subsequent medical 

 study. From this point of view the experiments 

 described in Dr. Cumming 's book are very suit- 

 ably selected and their sequence is well arranged. 

 The first exercises deal with the manipulation of 

 apparatus, solubility, crystallisation and its value 

 in the purification of compounds. These are fol- 

 lowed by an account of the properties of the 

 commoner acids and alkalis, of the preparation 

 and properties of the more important gases, and 

 of the properties of sulphur, iodine, and carbon. 

 These descriptions are accompanied by a series 

 of instructions for qualitative experiments, to 

 which a few simple quantitative exercises — for 

 instance, in the case of carbon dioxide and of 

 hydrogen — might have been added with advan- 

 tag-e. 



The succeeding sections deal with the prepara- 

 tion of salts, elementary volumetric analysis, and 

 the qualitative reactions of inorganic and of the 

 commoner organic compounds, including- the more 

 important alkaloids. In this new edition the 

 subject-matter of the previous issue has been care- 

 fully revised and a few additional experiments 

 with bread, potatoes, and fats, the fermentation 

 of glucose, and the action of saliva on starch have 

 been introduced. The descriptions of the experi- 

 ments and of the associated details of manipula- 

 tion are throughout direct and concise, so that the 

 course should form a really practical help to the 

 study of the general principles of chemistrv. 



C. A. K. 



AMERICAN GUNNERY. 

 Stresses in Wire-wrapped Guns and in Gun- 

 carriages. By Lt.-Col. Colden L'H. Ruggles. 

 Pp. xi + 259. (New York : John Wiley and 

 Sons, Inc.; London: Chapman and Hall, Ltd., 

 1916.) Price 135. 6d. net. 



THE preface to this the second edition explains 

 that the text was originally prepared for the 

 cadets of the U.S. Military Academy. The title does 

 not fully indicate the contents. The elastic stresses 

 in wire-wrapped guns are the subject only of 

 chap, i., pp. 1-36. Chaps ii. and iii., pp. 37-105, 

 deal with the forces which the firing of the gun 

 occasions in the principal parts of the carriage, 

 the 3-in. field carriage^ the 5-in. barbette carriage, 

 and the 6-in. disappearing carriage being taken 

 as examples. The problems are dealt with in these 

 two chapters as problems in ordinary statics and 

 dynamics. Chap, iv., pp. 106-73, treats of the 

 elastic stresses in parts of gun-carriages. Chap, 

 v., pp. 174-227, if not very obviously connected 

 with the professed subject of the book, gives a 

 clear descriptive account of "toothed gearing." 

 The subject of the last chapter, vi., counter recoil 

 springs, has more connection with guns than 

 mitrht appear at first sight. 



The numerous illustrations, which form a great 

 feature of the book, are generally very clear. 

 Some, especially those relating to toothed gearing- 

 — for instance, Figs. 78, 80, 89, and 93 — are 

 quite works of art. If scarcely necessary for the 



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