NA TURE 



145 



THURSDAY, DECEMBER 16, 1897. 



MENDELEEFF'S PRINCIPLES OF 

 CHEMISTRY. 



The Principles of Chemistry. By D. Mendeldeflf. Trans- 

 lated from the Russian (sixth edition) by George 

 Kamensky, A.R.S.M. Edited by T. A. Lawson, B.Sc, 

 Ph.D. Two vols. Pp. xviii + 621 and 518. (London: 

 Longmans, Green, and Co., 1897.) 



AN English translation of the earlier (fifth) edition 

 of this remarkable book was prepared by Mr. 

 Kamensky, and edited by Mr. A. J. Greenaway, in 1891. 

 It is therefore familiar to the English chemical world ; 

 and that a second edition of the English version should 

 be called for in a comparatively short time, is a proof 

 that the views of the author have a fascination which 

 secures for the book a wide circle of readers. The 

 author speaks of it modestly " as an elementary text- 

 book of chemistry " ; but it is probable that the previous 

 edition has been exhausted less by a demand on the 

 part of beginners in the subject, for whom, to say truly 

 it is little adapted, than as a consequence of the interest 

 which has been excited among advanced students and 

 professed chemists by the exposition of the doctrine 

 embodied in the so-called " Periodic Law," which is the 

 principal feature of the work. Enough has already been 

 said in the pages of Nature (see vol. xlv. p. 529) con- 

 cerning the characteristics of the book itself — the extra- 

 ordinary development of the foot-notes, which often 

 expand to such dimensions as almost to drive the text 

 out of the page, and which in many cases contain far 

 more interesting matter ; the strange inequality in the 

 materials collected, many processes, especially those 

 connected with manufactures, being quite antiquated ; 

 and others which need not be recalled. The confusion 

 of proper names, owing to errors of spelling, is not so 

 conspicuous as in the former editions, though one ludicrous 

 substitution occurs in the chapter on spectrum analysis, 

 where Huggins is three times over transformed into 

 Huyghens ! Such defects, however, do very little to 

 impair the real value of the book, or obscure the genius 

 of the author. Turning from the attitude of the literary 

 critic to that of the scientific inquirer, it is much more 

 profitable to see what such a chemist as Mendel^efF has 

 to say about special questions of fundamental or primary 

 importance. 



In chemistry the word element is in constant use in 

 the sense originally taught by Boyle, that is, signifying 

 something which has up to the present remained un- 

 decompounded. At the present day the majority of 

 chemists have probably settled down to the belief that 

 our seventy or eighty " elements " represent limiting 

 material, and that, so far as terrestrial affairs are con- 

 cerned, so they will always remain. Others — probably 

 however, a minority — conceive that relations among their 

 atomic weights hint that they may be compounded of 

 finer matter united in various ways, and though they 

 may not expect to rupture the bond which unites the 

 subatomic constituents together by any laboratory 

 process, yet they see in the spectral phenomena of the 

 stars evidence that under other conditions this rupture 



NO. 1468, VOL. 57] 



may actually be accomplished. Mendeldeff seems to 

 believe in the permanence of the terrestrial elements, for 

 not only in the two foot-notes on p. 20, vol. i., but in a long 

 digression upon the subject of Prout's hypothesis (p. 

 439-441, vol. ii.), he emphatically rejects the idea that 

 the atomic weights of other elements have any definite 

 numerical relation to that of hydrogen, and he points out 

 that attempts at transmutation of one element into 

 another have been hitherto fruitless. " All such ideas 

 and hopes," he says, " must now, thanks more especially 

 to Stas, be placed in a region void of any experimental 

 support whatever, and therefore not subject to the dis- 

 cipline of the positive data of science." Now and again, 

 even at the present day, there is a recrudescence of 

 alchemistic pretensions, but it may be noticed that the 

 discovery for which a claim is put forward always relates 

 to the transmutation of a base metal into silver or silver 

 into gold. If any one suggested that he had succeeded, 

 for example, in extracting lead from thallium, he would 

 be laughed at for his pains, but if he boldly asserts that 

 by a long and secret process he has succeeded in making 

 gold out of silver, he generally finds a few people at least 

 ready to take him seriously. 



Chemical affinity is another expression still freely used^ 

 though with widely different meanings by different 

 chemists ; and here again a definite expression of the 

 author's views is fortunately to be found in the pages of 

 his book. He says (p. 27) : 



" For a long time, and especially during the first half 

 of this century, chemical attraction and chemical forces 

 were identified with electrical forces. There is certainly 

 an intimate relation between them, for electricity is 

 evolved in chemical reactions, and has also a powerful 

 influence on chemical processes — for instance, com- 

 pounds are decomposed by the action of an electric 

 current. And the exactly similar relation which exists 

 between chemical phenomena and the phenomena of 

 heat (heat being developed by chemical phenomena, and 

 heat being able to decompose compounds) only proves 

 the unity of the forces of nature, the capability of one 

 force to produce and to be transformed into others. For 

 this reason the identification of chemical force with 

 electricity will not bear experimental prdof." 



He then goes on in a characteristic foot-note to refer 

 to the facts of substitution or " metalepsy," in which 

 hydrogen, a "positive" element, may be exchanged for 

 chlorine, a " negative " element, without altering the chief 

 chemical characters of the compounds in which the 

 exchange occurs. On a later page, also in a foot-note 

 the author gives an account of the electro-chemical 

 theories of Davy and Berzelius, and their relation to 

 successive hypotheses of the constitution of salts ; and 

 here again he seems to reject all modifications of Ber- 

 zelius' polar doctrine. It must be admitted, however, 

 that the book is not strong in this direction. After much 

 research we have not succeeded in finding a definite 

 statement of such imjiortant facts as are embodied in 

 Faraday's laws of electrolysis, the-nearest approach to it 

 being found on p. 581, but followed by an apologetic 

 foot-note in which it is stated that the plan and dimen- 

 sions of the book prevent the author from "entering 

 upon this province of knowledge." This is to be re- 

 gretted, considering the importance to the chemical 

 student of a good acquaintance with the facts, methods 



II 



