NATURE 



60 1 



THURSDAY, APRIL 28, 1892. 



THE ORE TIC A L CHE MIS TR V. 

 Otttlines of Theoretical Chemistry. By Lothar Meyer, 

 Professor of Chemistry in the University of Tubingen. 

 Translated by P. Phillips Bedson, D.Sc, and W. 

 Carleton Williams, B.Sc. Pp. 220. (London : Long- 

 mans, Green, and Co., 1892.) 

 ^< /"^ OOD wine needs no bush," but a well-known bush 

 vJ makes one look for good wine. The translation of 

 Prof. Lothar Meyer's " Die Modernen Theorien der 

 Chemie," made by Messrs. Bedson and Williams, is so 

 well known and so appreciated by all English-speaking 

 chemists, that everyone welcomes a new book by the 

 author of " Modern Theories," and expects the book to 

 be a good one. The " Outlines of Theoretical Chemistry" 

 is a translation, by the translators of the " Modern 

 Theories," of a book published in German in the course 

 of last year. The translation is exceedingly well done ; 

 the English runs smoothly and lucidly ; the book reads 

 as if it were composed in English, rather than as a trans- 

 lation from another tongue. 



The subject-matter of this book is very similar to that 

 of " Modern Theories " ; details are avoided wherever the 

 author thought this could be done with advantage, and 

 the treatment is made as general as possible. In his 

 preface to the English translation the author says : — 



"The general — I may say the philosophical — review 

 of the subject has been my chief aim, to which the details 

 should be subordinated." 



The book is not divided into chapters, but runs 

 on from paragraph to paragraph. Beginning with a 

 statement of the province of chemistry, the author 

 passes in review the stoichiometric laws, sketches the 

 atomic hypothesis, considers the various aspects of 

 chemical equivalents, states and applies the law of 

 Avogadro, refers to Prout's notions about the relations 

 between the values of atomic weights, and states and 

 briefly illustrates the periodic law ; he then considers in 

 several paragraphs the constitution of compounds in the 

 light of the molecular and atomic theory, and, through a 

 short discussion of physical isomerism, he passes to the 

 consideration of such physical properties of bodies as 

 melting and boiling point, capillarity, solubility, evapora- 

 tion, &c., and the connexions between these and the 

 molecular weights and constitutions of bodies. Finally 

 the author devotes some fifty or sixty paragraphs to the 

 treatment of the thermal and electrical aspects of chemical 

 changes, and the subject of chemical affinity. 



At the outset the essential character of chemical 

 phenomena is emphasized : — 



" Chemistry deals with the changes which affect the 

 material nature of the substance. Chemistry, then, is the 

 science which treats of matter and its changes" (p. 2). 



It is to be wished that all writers of books, whether 

 elementary or advanced books, on chemistry, and all who 

 endeavour to help others to learn this science, would keep 

 steadily before them the characteristic feature of all 

 chemical events, viz. that they are those which occur 



NO. II 74, VOL. 45] 



when changes of composition accompany changes of 

 properties in definite kinds of matter. If this were done 

 we should not be deluged with those catalogues of the 

 properties of innumerable disconnected substances which 

 are frequently sold under the misleading name of text- 

 books of chemistry. 



The paragraphs on the determination of atomic weights 

 from stoichiometric values (pp. 11-13) seem to me ex- 

 tremely lucid and apposite, provided the reader will give 

 his close attention to them. I do not think the subject of 

 chemical equivalents is treated sufficiently fully to make 

 it clear (pp. 13-16). Paragraph 13 does not make 

 perfecdy intelligible the process whereby atomic weights 

 are determined from the crystallographic relations of 

 compounds. I am much taken by the order in which 

 the author arranges his treatment of combining weights^ 

 equivalents, thermic equivalents, crystallographic equiva- 

 lents, &c., culminating in Avogadro's law. The deter- 

 mination of atomic weights by the application of the law 

 of Avogadro is made very clear in a couple of paragraphs 

 (pp. 39-42) ; and the author is especially to be congratu- 

 lated, in my opinion, on paragraph 26, wherein he most 

 skilfully and gracefully avoids the popular error of making 

 a stumbling-block of so-called " abnormal vapour-densi- 

 ties." 



Paragraph 28, which deals in about thirty lines with 

 " nascent state," would much better have been omitted ; 

 the treatment is neither interesting nor accurate. It 

 seems to me that paragraphs 34-40, which are supposed 

 to give a clear general conception of the periodic law, 

 quite fail to enable the student to grasp this all-important 

 generalization. I think that much too little space is 

 given to the periodic law, which comprises in itself all 

 other schemes of chemical classification ; and that too 

 much space is devoted to valency, which, at the best, is 

 a conception that is of very limited application. Anyone 

 who turns from the study of Mendeleeff's great work on 

 "The Principles of Chemistry" to the paragraph on 

 p. 76 will be greatly astonished ; the paragraph reads 

 thus :— 



" Formerly it was more or less explicitly assumed that 

 a chemical compound was held together by the total 

 attractive force of the affinities of all the atoms contained 

 in it ; but, as our knowledge increased, it was gradually 

 recognized that the connexion is between atom and 

 atom, and that the atoms are attached to each other like 

 the links in a chain, the continuity ceasing if even a 

 single link of the chain is removed." 



This sentence seems to imply that no one now looks 

 on a molecule as held together by the interactions between 

 all the atoms ; but if one says this view is held by none, one 

 must make a few exceptions, such as Mendeleeff and the 

 chemists of his school. The treatment of atomic linkage 

 on pp. 80-83 seems to me to be very one-sided and un- 

 satisfactory. We are told (p. 81) that such a formula as 

 HoO . SO3 is inadmissible because it represents the com- 

 pound as made up of atomic groups which are already 

 saturated, and " therefore have no free affinities for 

 mutual combination"; but on p. 107 we are informed 

 that, in substances which crystallize with water, " every 

 molecule is united with a definite number of molecules of 

 water." But how can water molecules unite with, say, 

 dehydrated alum, if the group HoO is saturated and " has 



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