Intelligence and Miscellaneous Articles, 411 



experiment au blanc ; when he is to prepare a special reagent for 

 a special test, he is told to prepare that reagent ex tempore. But 

 perhaps it is scarcely fair to condemn the style of a book which is 

 not written in the native tongue of the author. The well-known 

 skill of Mr. Dittmar as an analyst is a guarantee of the general 

 correctness of the methods given in the book. In the statement 

 of so many reactions it is almost impossible that no mistake should 

 occur. On page 229 the action of nitric upon hydrochloric acid 

 is said to produce the substance ]^OCl 2 ; Tilden has, however, 

 shown that no such substance exists, and that the reaction in ques- 

 tion results in the formation of JNTOCl. 



Hitherto we have been looking at the work before us as a text- 

 book for the ordinary chemical student. If, however, we view it as 

 a book of reference for the very advanced student, or for the 

 chemical teacher, it must appear worthy of the highest praise. In 

 no other English manual is there gathered together such stores of 

 information on all matters connected directly or indirectly with 

 chemical analysis ; nowhere are the difficulties which beset the 

 complete analysis of a complex substance so fully pointed out and 

 so carefully guarded against. In no book, we may add, is there 

 presented so complete a scheme of analysis for detecting the non- 

 metallic radicals. The reader is directed in the right way; but it is 

 left to himself whether he shall walk in it or not. This want of 

 authoritative instruction, while rendering the book unsuited to the 

 ordinary student, makes it admirably adapted for bringing out any 

 latent power of scientific reasoning which may be possessed by the 

 more advanced analyst. 



The author has not contented himself with detailing the ordinary 

 methods of analysis ; he has brought together a host of facts 

 about the general reactions of classes of chemical substances, 

 metallic and non-metallic ; and from these reactions he has 

 sketched out methods of analysis which are theoretically, and, we 

 should suppose, in general practically available. From his own 

 view-point, which includes the whole range of analytical reactions, 

 it cannot be but that the author should see difficulties in the ap- 

 plication of almost every method. These difficulties he has nowhere 

 attempted to hide. Where he can suggest a method for over- 

 coming them he makes such a suggestion ; otherwise he leaves 

 them to be overcome, if possible, by the student himself. To the 

 truly scientific analyst who has already an extensive knowledge of 

 chemical reactions and general principles, this book will be simply 

 invaluable ; but to the student it will be distracting. 



L. Intelligence and Miscellaneous Articles, 



THE INFLUENCE OF TEMPEEATUKE ON MAGNETIZATION. 



BY J.-M. GAUGAIN. 



[" HAD the honour of presenting to the Academy the results of 



-*- some previous researches on this subject, in a Note inserted in the 



Comptes IlenduSj^eb, 1, 1875, which I will briefly recapitulate ;— > 



