344 SCIENCE PROGRESS 



An omission which can be urged against this, as indeed against most other 

 volumes on analysis, is the absence of any exact details as to the degree of 

 accuracy of a particular method of analysis. Such terms as " accurate," " very 

 accurate," or "only empyrical" are much too indefinite for a scientific work, 

 and it is quite time they should be dropped and exact data substituted whenever 

 possible. By experience in analysis one arrives at a time when such terms may 

 have a more or less exact meaning, but the inclusion of a few details from actual 

 practice or from the original papers, on the order of accuracy likely to be 

 experienced in each particular method, is very much to be desired, and most 

 particularly for junior students. Another point which could with advantage 

 receive more attention than it does at present, is the exact degree of chemical 

 purity of the commoner substances used in preparing standard solutions. Very 

 often, in the absence of any exact data, many solutions have to be standardised 

 by working back through various standard solutions to some solution, usually 

 sodium carbonate, which can be prepared accurately by weighing out the 

 chemically pure solid. To have to do this generally involves a considerable 

 amount of time and labour, which could be obviated to a large extent if the 

 exact analysis of the starting substance were known. The best British and 

 foreign firms supplying chemicals for analytical purposes now give an accurate 

 analysis of many of the commoner substances, and these ought to be available 

 in the text or as an appendix. 



As to the methods, the author has selected most of those which are thoroughly 

 sound and proved by practice. Besides these there are several useful so-called 

 " empyrical " methods which are not usually to be found in this type of book. 

 On p. 44 the volumetric determination of SO? in aqueous solution by iodine is 

 outlined, and the usual explanation is offered for the discrepancies w hich occur when 

 titrating more concentrated solutions of the gas, unless the solution is run into 

 excess of iodine solution, and the iodine back-titrated with thiosulphate. Even 

 with the precaution of vigorous stirring as the SO., solution is being run in, which 

 the author does not mention, we doubt if the improved method is altogether free 

 from irregularities. 



The book contains a very full chapter, illustrated by a few diagrams, on the 

 theory of indicators, and containing a table of the dissociation constants for the 

 majority of indicators, both basic and acidic. The ionic view is fully dealt with 

 and the other theories are touched upon, but whilst the ionic theory has doubtless 

 thrown very much light upon the mechanism of indicators, the author rightly 

 points out that it by no means precludes the presence of other phenomena as 

 essential adjuncts. 



On p. 20, in connection with the reduction of iron and vanadium salts, the 

 author takes to task the existence of the supposedly potent "nascent" state. 

 It is very proper that such chemical fallacies should not become stereotyped 

 and handed on to students with each new text-book. Again, it is satisfactory 

 to find, as on p. 60, the theory of errors in indirect analyses clearly expounded, 

 and further, on p. 10, that the uselessness of working out results to a decimal 

 place, which can have no meaning, is pointed out. This latter is a fault to which 

 young students are very prone, and one which very seldom receives any treatment 

 in books intended for their use. 



In a later chapter mention is made of useful applications of volumetric 

 analyses, such as determinations of solubility, partition coefficients, and velocities 

 of reaction. 



C. S. G. 



