304 Notices respecting New Books. 



view, which is warmly supported by Ostwald, the Mater or solvent 

 in general, which certainly plays an important part in solutions, 

 and especially dilute ones, is entirely lost sight of, I consider it 

 premature at present to explain the theory of Arrhenius, but think 

 that it contains the seeds lor further development and for its being 

 merged into a fuller theory of solutions " (Yol. I. p. 323, note 29). 

 A similar caution is given when considering the determination of 

 the avidity of acids by the methods now in vogue and of which 

 according to Mendeleeff the results are questionable, owing to the 

 circumstance " that in making investigations in aqueous solutions 

 the affinity to water is generally left out of sight" (Yol. I. p. 377, 

 note 14). 



Although we can only dip here and there into the two bulky 

 volumes, enough has been said to show what wealth of material 

 the author has given to chemists. If it is only for breaking 

 through the threadbare treatment of the elements and their com- 

 pounds arranged under the headings " occurrence," "preparation," 

 and " reactions," which has hitherto formed the mental stock in 

 trade of the average chemical student in this country, Mendeleeff 

 has earned our gratitude. But the originality of the treatment is 

 the most valuable feature of the work, and strikes the reader more 

 and more forcibly as he becomes more familiar with the contents 

 of the volumes. Take for instance Chapter X. of the first volume, 

 in which, after treating in previous chapters of the four typical 

 elements — hydrogen, oxygen, nitrogen, and carbon, the author 

 deals with sodium chloride as a type of salts in general. Begin- 

 ning with a short reference to valency, which is more fully discussed 

 together with specific heat in the last chapter of the same volume, 

 the natural history of common salt is given in detail, its tech- 

 nology is described and illustrated and then, from considering the 

 action of sulphuric acid on the compound, we are led to a remark- 

 ably lucid discussion of the laws of Berthollet and their extension 

 by Guldberg and Waage, which extends over nearly 20 pages. 

 And so throughout the same principle is observed; the broad 

 generalizations are not dogmatically set forth to be learnt as a 

 schoolboy learns a lesson, but are led up to through observations 

 or facts having special reference to the generalization about to be 

 introduced to the student's notice. This method may in many 

 cases lead to an apparent incoherence, but it insures the reading 

 of the book ; the deduction of broad principles in places where the 

 student lias not hitherto been led to expect them is in itself a 

 good mental discipline, and serves well to cement the heterogeneous 

 groups of facts with which chemical science has to deal into one 

 coherent whole. 



Although, as the author states at the outset, the general treat- 

 ment is made to centre round the periodic law, it is not till the 

 second volume that this law is set forth in all its bearings. The 

 fifteenth chapter is entitled "The Grouping of the Elements 

 and the Periodic Law," and this is followed by nine chapters deal- 

 ing with the different groups of elements. The fundamental 

 importance of the law of periodicity is now so widely recognized 



