Oct. 7, 1880] 



NA TURE 



531 



mode of arrangement of atoms in a molecule, sometimes 

 only as condensed statements of facts of formation and 

 decomposition. If the former view be adopted it becomes 

 a question whether the " structure " represented by the 

 formula is that of the molecule when unacted upon by 

 the molecules of foreign bodies, or only when a certain 

 disposition of its parts has been induced by the action of 

 the molecules of another substance. 



Facts are certainly known which are best explained by 

 supposing that a change of some kind precedes that 

 process of complete molecular decomposition usually 

 called a chemical reaction ; indeed almost the only 

 feasible hypothesis of chemical action supposes that 

 chemical change — that is, change among the parts of the 

 molecule — may be proceeding without a permanent mole- 

 cular decomposition taking place. In the section on 

 " Aldehydrols " the authors apparently admit some such 

 hypothesis as this ; they do not regard the non-isolation 

 of a compound as proof of the non-existence of that com- 

 pound ; they explain processes of chemical change by 

 supposing the existence of unstable molecular configura- 

 tions intermediate between more stable and isolable 

 configurations. 



Recent work in chemical physics appears to lend some 

 countenance to the idea that structural formulas may 

 roughly represent the configuration of molecules just 

 previous to their passage into phases of " absolute insta- 

 bility" rather than their configuration when in phases 

 which are themselves "absolutely stable." 



Quite recently a distinct advance has been made in 

 molecular theories by the recognition of what might be 

 called atomic inductio7i, that is, the influence exerted 

 by one part of a molecule in modifying the chemical 

 function of another part, or other parts, of the same 

 molecule. Illustrations of this "orientation" are to be 

 found in the production of the substituted derivatives of 

 benzene and of the phenols ; the generalisations made in 

 these cases are clearly stated by the authors. 



A very valuable section on the Van't Hof Le-Bel 

 hypothesis of isomerism is to be found from pp. 983 to 

 993. (There is evidently an omission of part of a sen- 

 tence at the top of p. 993.) The authors suggest a slightly 

 modified form of this hypothesis. The fundamental 

 assumption is made in these hypotheses that chemical 

 energy is entirely potential, and that it is wholly due to 

 the arrangement of the parts of the molecules. It seems 

 possible however that chemical energy may be partly 

 potential and partly kinetic, and that if any means could 

 be found for measuring the change of entropy as well as 

 the change of total intrinsic energy of chemical systems 

 in their passage from one standard state to another, some 

 light might be thrown on the question of isomerism. 



In their general classification of carbon compounds the 

 authors have adopted a scheme founded on the chemical 

 function of these compounds ; they group together hydro- 

 carbons, alcohols, aldehydes, &c. They do not fail to 

 indicate how function is associated with "structure." 

 But in each of these great groups of compounds a classi- 

 fication founded more upon genetic relations is adopted ; 

 they consider a group of hydrocarbons, then the haloid 

 derivatives of these hydrocarbons, and so on. 



Most admirable tables are appended to all the more 

 important groups ; the usefulness of these tables may be 



illustrated by reference to that on pp. 458-459, wherein 

 the ethylic alcohols are arranged in really homologous 

 series. 



The acids are classified into various sub-groups, and 

 the dependence of the function of the " acid hydrogen " 

 on the "structure" of the other part of the molecule is 

 indicated. 



In speaking of the higher aromatic or "benzenoid" 

 hydrocarbons, the happy expression is used of a closed 

 chain containing '■'loops," and it is pointed out that "the 

 formation of each new loop in the chain of carbon atoms 

 tends to reduce the combining power by two units." 



The proof (p. 399) that the carbon atoms in the olefines 

 are not arranged in a closed chain is noteworthy, and 

 may be taken as typical of the authors' method of dealing 

 with such questions ; basing a generalisation on carefully 

 collected facts, and then applying their generalisation 

 boldly, but without dogmatism. 



The nomenclature of the work before us is much more 

 self-consistent than that adopted in any other treatise on. 

 organic chemistry. Certain new names are introduced : 

 thus, the bodies supposed to exist in aqueous solutions of 

 many aldehydes— substances characterised by the groups 

 CH(OH)„— are called aldehydrols. A systematic nomen- 

 clature for the carbohydrates is proposed : those of the 

 composition CqHi20|; have names ending in ose, glucose 

 being the best known example of this class ; those of the 

 composition CioHjaOn, which like cane-sugar produce 

 two molecules of glucose on inversion, have names ending 

 in on, e.g., saccharon ; and those which on hydration 

 give rise to the formation of a saccharon have names 

 ending in yn, e.g., amylin. As another instance of the 

 authors' attempt to systematise nomenclature may be 

 noted their rules for the use of the Greek letters a, 3, &c., 

 in distinguishing isomeric derivatives (pp. 861-2, note). 



Finally, I would draw attention to the authors' manner 

 of dealing with physical methods of solving chemical 

 problems : the physical method is so described that one 

 cannot forget that it is to be used by a chemist — there is 

 not first a little physics, and then a little chemistry ; the 

 problem is clearly chemical, the method only is physical. 



A suggestion made in the preface seems most admirable, 

 it is that " Each chemical school " would do well to 

 "make the preparation by its students of certain sub- 

 stances in a state of purity a part of the ordinary course 

 of study, and to give notice that these particular compounds 

 are at the disposal of experts for the determination of 

 physical constants." 



Is there any probability of a treatise being written 

 on Inorganic Chemistry conceived in the same spirit and 

 carried out, as far as possible, on general lines similar to 

 those of this most excellent work by Armstrong and 

 Groves ? M. M. Pattison Muir 



OUR BOOK SHELF 

 An Elementary Treatise on Solid Geometry. By W. 



Steadman Aldis, M.A. (Cambridge : Deighton, Bell, 



and Co., 1880.) 

 The term "elementary" diagnoses this handy book to 

 solid geometry from the more thorough works on the 

 same subject by Messrs. Salmon and Frost. It is, to our 

 mind, exceedingly well adapted to the requirements of 

 that large class of students who, whilst requiring an 

 acquaintance with this branch of study, are unable, either 



