Notices respecting New Books. 225 



drawn with centre H, we have the sectional view of the optical 

 convex mirror which will give the same position of image as 

 the magnetic convex mirror shown by the circle CED. 



In conclusion, it may be remarked that the construction of 

 fig. 14 affords a new and simple graphic method of finding the 

 position of optical images, by the device of using the auxiliary 

 circle whose diameter is the radius of the spherical surface. 



XXI. Notices respecting New Boohs. 



The Scientific Basis of Analytical Chemistry. 



Die ivissenschaftliclien Grundlagen der Analytischen Chemie. Ele- 

 mental* dargestellt von W. Ostwald. (Leipzig: Wilhelm 

 Engelmann. 1894.) 



I T has been so long the custom with a certain class of teachers in 

 -*- this country to regard analytical chemistry as synonymous with 

 chemical science that the very title of this book will come as a 

 surprise. Prof. Ostwald, in the present little volume of 187 pages, 

 has attempted to present the subject of chemical analysis in a 

 popular form and in a new T way. Whether he has succeeded in 

 his objects in his own country it is difficult to say, but so far as 

 English chemists are concerned the book is certainly not likely to 

 achieve popularity : first, because it is not arranged in accordance 

 with our examinational notions of chemical analysis ; and, secondly, 

 because it bases the analytical properties of the elements and their 

 compounds on a theory which has not found general acceptance in 

 this country, viz. the theory of ionic dissociation. But in calling 

 attention to these two points we are really bestowing praise upon 

 the work ; because any novelty of treatment in such a well-worn 

 field is to be cordially welcomed, and all attempts to approach the 

 subject from a different scientific aspect to that generally adopted 

 are bound to help in the " depolariz£ition " of cut and dried dogmas 

 which are so baneful to true progress in science. 



Of the two parts into which the book is divided, the first, con- 

 sisting of five chapters, deals with theory, and the second, consisting 

 of eight chapters, deals with applications. The theoretical part, 

 where concerned with the ordinary operations, is lucidly put 

 together, and forms quite pleasant reading as compared with the 

 purely cookery-book kind of directions that the student in this 

 country is expected to follow. We doubt much whether the 

 average " certificated teacher " knows that there is any scientific 

 theory behind the processes which he has been drilled into carrying 

 out. It is in the fourth chapter, under the heading Die chemische 

 Scheidung, that the new theory of solutions is first broached, and 

 from that part onwards everything connected with the subject is 

 treated of from the point of view of ionic dissociation. Whether 

 this view is accepted or not, it must be conceded that Prof. Ostwald 



Phil Mag. S. 5. Vol. 39. No. 237. Feb. 1895. Q 



