March 12, 1903] 



NA TURE 



437 



presently renders untenable. As examples in point, 

 one need only recall the testing of foodstuffs for arsenic, 

 and the alleged conversion of this element into anti- 

 mony. Wherefore, when the chemist buys his chemi- 

 cals let him remember the legal tag above quoted, and 

 not trust too implicitly to the manufacturer who sup- 

 plies them. 



The book before us will help to minimise the labour 

 involved in satisfying oneself on this matter. It deals 

 with some hundreds of reagents used by the chemist, 

 and with a few of those generally employed by the 

 microscopist. As regards its plan, the substances are 

 arranged in alphabetical order, beginning with " acetic 

 acid " and ending with " zinc sulphate." Under each 

 heading are described, very briefly, a few of the more 

 prominent characters - of the reagent, such as its 

 formula, molecular weight, boiling point, specific 

 gravity, or crystalline form. Then follow, as a rule, 

 a number of " tests for impurities," in which are indi- 

 cated the probable foreign substances to be met with in 

 the article under examination, and the characteristic 

 methods of detecting them. A paragraph or two deal- 

 ing with the " quantitative estimation " of the reagent 

 is added in those cases where the addition is applicable. 

 Following this come notes upon " uses " or " uses 

 and storage," in which mention is made of the purpose 

 for which the reagent is generally required, and hints 

 given as to how it should be kept — e.g. whether pro- 

 tected from light, in a cool place, under oil, and so on. 

 Finally the " commercial varieties " of the substance 

 are shortly indicated. 



On account of the number of articles dealt with, 

 the information afforded is necessarily for the most 

 part very brief, and is always concisely put. Fairly 

 full descriptions, however, are given in the case of 

 some of the more important reagents : thus ten pages 

 are devoted to alcohols, six to ether, and eight to hydro- 

 chloric acid ; whilst tables of the strengths correspond- 

 ing to various values of specific gravity are appended 

 to the sections dealing with such reagents as acetic 

 acid, ammonia, alcohol, and the mineral acids. Refer- 

 ences, and useful ones, are frequently given to litera- 

 ture in which further information is to be found ; and 

 in place of the original German sources the trans- 

 lators have very considerately indicated abstracts and 

 papers to be found in English journals and text-books. 

 All the ordinary reagents are described, and also a 

 number of those less frequently used. As regards the 

 inclusion of the latter, the present writer has tested 

 the volume in respect of a few of the less common re- 

 agents, such as the persulphates, iodeosin, and nitroso- 

 /3-naphthol (which latter, by the way, can be re- 

 commended for the separation of cobalt from nickel), 

 and finds them duly mentioned except in the case of 

 the persulphate. 



The book is hardly one which calls for much criti- 

 cism. The value of such a work consists in its bringing 

 conveniently together the chief data pertaining to the 

 various substances, so far as they are criteria of purity. 

 If a good selection is made, and if the information is 

 accurate, the book saves labour and fulfils its purpose. 

 Judged by this standard the volume can be unre- 

 servedly commended. C. Simmonds. 

 no. 1 74 1, VOL. 67] 



OUR BOOK SHELF. 



Text-book of Electrochemistry. By Svante Arrhenius. 

 Translated by John McCrae. Pp. xi + 344. 

 (London : Longmans and Co., 1902.) Price 95. 6d. 

 net. 



This work, by the chief founder of modern electro- 

 chemical theory, is worthy of a hearty welcome in its 

 English form. It is distinguished from other works 

 on the same subject by being at once more thorough 

 and more simple, the difference being specially 

 apparent in the chapters dealing with potential and 

 electromotive force. Too often the treatment of this 

 branch of the subject leaves the impression (on the 

 student of chemistry at least) that a simple and im- 

 portant result is arrived at from no premisses in par- 

 ticular by. some unconvincing mathematical hocus- 

 pocus, wholly devoid of concrete meaning. Prof. 

 Arrhenius is necessarily somewhat mathematical, 

 but the physical significance of each step is so care- 

 fully explained that no attentive student of physics or 

 chemistry, with the most rudimentary knowledge of 

 the calculus, can fail to gain a clear idea of the pro- 

 cess of reasoning, and, if need be, to reproduce it with 

 understanding. Whilst we have this very desirable 

 treatment of theoretical matters, the practical side of 

 the subject is no less satisfactorily dealt with. In 

 small compass, an immense amount of well-selected 

 and clearly-put information is conveyed; for example, 

 in the two pages which are devoted to the electric arc, 

 the essential features of the phenomenon are given 

 with a precision and conciseness infrequent in physical 

 text-books. The chapter on electroanalysis affords 

 a similar instance of happy exposition. Throughout 

 the book, and especially where matters of recent con- 

 troversy are under discussion, there is manifested a 

 temperateness of language and sobriety of judgment 

 which cannot be too highly commended. 



The first two chapters of the volume give an 

 account of fundamental physical and chemical con- 

 ceptions, and of the older electrochemical theories. 

 The next five chapters are chiefly concerned with 

 osmotic pressure and the thermodynamical deductions 

 from it, the general conditions of equilibrium, and the 

 velocity of chemical actions. Chapters viii.-xii. are 

 devoted to electrolytic dissociation and the deductions 

 to be drawn from that theory. In chapters xiii.- 

 xv., electromotive force is dealt with; and in the 

 last two chapters are taken up the practical subjects 

 of electroanalysis and the development of heat by 

 the electric current. 



The present translation has been made from the 

 German edition, which is a somewhat expanded form 

 of the Swedish original. The English version is well 

 done, and we have to thank Dr. McCrae in addition 

 for an excellent index and a very useful appendix 

 of references. J- W. 



A Manual of Indian Timbers. By T. S. Gamble, 

 M.A., CLE., F.R.S., F.L.S. Pp. xxiii 4- 856 ; illus- 

 trated by photographs of wood sections. New (second; 

 and revised edition. (London : Sampson Low, Mar- 

 ston and Co., Ltd., 1902.) 



The first edition of this important work appeared in 

 188 1, giving the results of investigations made by Sir 

 Dietrich Brandis and his assistants, Messrs. Gamble and 

 Smythies. It was edited by Mr. Gamble, and it con- 

 tained descriptions of 906 species of Indian timbers. 

 The new edition has been entirely prepared by Mr. 

 Gamble ; it deals with about 1450 species, including all, 

 or nearly all, really important timber-woods. The total 

 number of species of trees, shrubs and climbers found in 

 India and Ceylon is estimated to amount to about 5000, 



