226 Intelligence and Miscellaneous Articles. 



has made out a good case in support of its applicability to the 

 ordinary processes of analysis. The key-note is struck on p. 47 

 in the following extract, which we paraphrase : — 



"In aqueous solutions of electrolytes the ions are generally 

 partly combined and partly uucorabined. In neutral salts the 

 uucombiued portion is by far the greater, and is in fact the more 

 in preponderance the more dilute the solution. The properties of 

 dilute salt-solutions are consequently determined, not so much by 

 the properties of the dissolved salt as such or by the combined ions, 

 but rather by the properties of its free ions. Through this con- 

 ception the analytical chemistry of saline matter (salzartigen Stoffe) 

 at once undergoes an enormous simplification : it is not the ana- 

 lytical properties of salts as a whole, but only those of their ions 

 which have to be established. Supposing that 50 anions and 

 50 kations are driven, these can form with each other 2500 salts ; 

 and supposing these salts to possess individual reactions, the pro- 

 perties of 2500 kinds of matter must be individually enunciated. 

 But since the properties of the dissolved salts are simply the sums 

 of the properties of their ions, it follows that the knowledge of 

 50 + 50=100 cases is sufficient to predominate over the whole 

 possible number of 2500 cases. As a matter of fact, analytical 

 chemistry has long made use of this simplification. It has long 

 been known, for example, that the reactions of the copper salts 

 are the same with respect to copper, whether we examine the 

 sulphate, nitrate, or any other salt ; the scientific formulation and 

 the cause of this behaviour have, however, been reserved for the 

 dissociation theory." 



Any polemically disposed chemist might feel inclined to traverse 

 the last statement, but we have said enough to show T that we have 

 at any rate a work on chemical analysis which can in reality be 

 called a new work. It is worthy of the most careful study, and 

 its pages will be found interesting both by veterans and novices ; 

 an opinion which is tantamount to the highest praise that can be 

 bestowed upon a book devoted to a subject in which there has 

 been practically no scope for a new departure since the time of 

 Liebig. 



XXII. Intelligence and Miscellaneous Articles. 



ON THE CHANGE OF LENGTH IN SOFT IRON WIRE PLACED IN A 

 UNIFORM MAGNETIC FIELD. BY B. ROSING. 



To the Editors of the Philosophical Magazine. 



Gentlemen, 



IN No. 224 (vol. xxxvii.) of your esteemed Magazine was pub- 

 lished a paper by Mr. Nagaoka on " Hysteresis attending the 

 Change of Length by Magnetization in Nickel and Iron." (Since 

 the autumn of 1891 I have been investigating the same question, 



