July 6, 1893] 



NA TURE 



221 



juate treatment. In discussing neutralisation, however, 

 he author has fallen into a serious error. On page 178 

 ve find in italics the statement that " when a base and 

 in acid are mixed in equivalent proportions in aqueous 

 iolution they are transformed entirely, no matter how 

 veak they may be, into a salt and water." This is 

 itKloubtedly«rroneous. A solution of potassium cyanide, 

 or example, is never neutral, but always contains free 

 )o;ash and free prussic acid. The author has been led 

 nto this error by assuming in the construction of his 

 ■nuations that water is a perfect non-electrolyte, i.e. is 

 at all dissociated into ions. 



he chief defects of the book are the want of propor- 



already alluded to, and the too bare formal mode 



reatment. Fewer formulae and more text would better 



the requirements of the average student. The 



i^raphy and clear arrangement of the mathematical 



ions of the work are admirable. It is to be regretted, 



lo.vever, that the text has not had the advantage of 



evision by a German proof-reader. The Dutch com • 



tor is presumably responsible for some quaint speci- 



is of German, and oscillates in his spelling between 



mtiquated forms like " dasz," " nahmlich," and painfully 



)honetic renderings such as "grafisch" and " Kwadrat- 



■el." 



; he book may be confidently recommended to those 



A ho already know the elements of thermodynamics and 



ire desirous to learn the applications of that science to 



he problems of general chemistry. J. W. 



OUR BOOK SHELF. 



ussion oj the Precision of Measurements. By Silas 

 .. Holman. (London: Kegan Paul, Trench, Tiiibner, 

 '.lid Co., Ltd., 1892.) 



In IS book deals with a subject that becomes more 

 important every year, and its applications in nearly every 

 science are both numerous and necessary. That our 

 means of accurate measurement have reached a very fine 

 stage, which is difficult to exceed, at any rate to a great 

 extent, is well known, but results can be made of far 

 j;reater value when subjected to a thorough discussion. 

 in astronomy one may, perhaps, say that such discus- 

 sions are carried through to their fullest extent and 

 'King problems by the methods of least squares — a 

 ins of obtaining the most accurate values for the 

 iitities sought after — is the rule and not the exception. 

 je able to find out the precision with which measure- 

 ts have been made, whether by means of a yard- 

 isure, the circle of a meridian instrument, or any other 

 ns, is at all times of great interest to the student of 

 lice, and the present work is intended especially as a 

 rse of study to engineers and for students of pure sci- 

 :s,to present in a clear manner the principles on which 

 :i questions as. What accuracy is desired in the result? 

 li what accuracy must each individual measure be 

 uned? and How trustworthy is the final result when 

 lined ? &c., can be answered. The material here used 

 IS the author informs us, the outcome of several 

 ; i ..1 s' teaching of the subject, and a study of the volume 

 htself indicates that he has presented it in a form that 

 will commend itself to its readers. The book is divided 

 {mainly into three parts. The first deals with the treat- 

 'ment of direct measurements, the second with indirect, 

 land the third with the determination of the best magni- i 

 tudes of components. In the beginning the various sources 1 

 MO. 12^6. VOL. 4.8] 



of error, in different kinds of measurement, are pointed 

 out, and the reader is made familiar with determinate 

 and indeterminate errors, deviations, general laws of 

 deviations, &c., terminating with two fully-worked out 

 examples relating to the balance and voltmeter calibra- 

 tion. Part ii. gives in a clear way the methods of 

 procedure with regard to indirect measurements, several 

 examples being interpolated illustrative of the rules de- 

 scribed. The third and last part is devoted to the solution 

 of a certain class of problems, which deal more with the 

 use of the instruments with which the observations are 

 ma e, than with the observations themselves. Thus, for 

 instance, in using a tangent galvanometer to find the 

 best anuleof the needle which will give the least errors of 

 reading. This and several other problems, taking the 

 cases when there are one, two, three, or more components, 

 are thoroughly worked out. The book concludes with a 

 series of illustrative examples. 



Traitc Pratique d' Analyse Chimique et de Recherches 



Toxicologiques. Par G. Gudrin. (Paris : Georges 



Carre, 1893.) 

 This book differs in several important respects from 

 ordinary works on analytical chemistry. 



The first three parts are concerned with the ordinary 

 processes of qualitative analysis— wet and dry reactions, 

 the separation of group precipitates, &c. As special fea- 

 tures of these sections it may be noted that coloured re- 

 presentations of borax beads and of beads of microcosmic 

 salt are supplied, and that the reactions of the rare meials 

 and of acids such as bromic, selenic, butyric, malic, 

 meconic, &c , which are but seldom introduced into 

 text- books, are fully discussed. 



After a short section dealing with the qualitative 

 analysis of gaseous substances, the author deals with 

 spectroscopic methods of analysis. In this part are 

 described the various forms of spectroscope, and the 

 modes of obtaining and observing both emission nnd 

 absorption spectra. A table is given of the characteristic 

 rays in the emission spectra of the different elements 

 arranged in order of their wave-lengths. In connection 

 with absorption spectra, chlorophyll, salts of didymium 

 and erbium, potassium permanganate, and blood, includ- 

 ing the treatment of blood-stains, are considered. Both 

 emission and absorption spectra are illustrated by means 

 of coloured charts. 



Part vi., which is by far the most extensive, is devoted 

 to toxicology. The conduct of chemico-legal inquiries in 

 cases of suspected poisoning by arsenic, phosphorus, 

 hydrocyanic acid, chloroform, and chloral are first given 

 in detail. Then are considered the general reactions 

 and, where devised, the modes of separation of ihe 

 vegetable alkaloids and the alkaloids of animal origin, 

 the ptomaines and leucomaines. This section is com- 

 pleted by a full and historical account of the charac- 

 teristic chemical properties and physiological action of 

 the principal alkaloids. 



Quantitative methods only find a place in the last part 

 of the book, where the author introduces the examination 

 of potable and mineral waters, and the estimation of 

 clays, irons, and steels. In this part the apparatus and 

 methods used in the bacteriological study of water are 

 also included. An appendix relating to the preparation 

 and concentration of reagents and a full index are 

 supplied. 



The prominence given to the reactions of the rare 

 metals, the introduction of spectroscopic methods, and in 

 particular the chapters on toxicology, make the work a 

 valuable addition to the literature on analysis. It may 

 be noted, however, that when dealing with the constitu- 

 tion of substances like the alkaloids, the author occasion- 

 ally uses formute which are as yet far from being 

 definitely established. 



