Sitpplciiiciit to " Nat!i7-e" November 14, 1901. 



announced from time to time by v. Kostanecki and his 

 colleagues. It is not improbable that before many years 

 have elapsed the above statement concerning the benzo- 

 •y-pyrones will have to be modified so as to read in the 

 exactly opposite sense. 



In calling the attention of English chemists to the 

 present edition we cannot too strongly emphasise 

 the point that the eminently readable character of the 

 original " Roscoe and .Schorlemmer" has been greatly 

 enhanced by the revision which it has undergone in 

 Germany. It is not only the historical treatment which 

 makes the book such interesting reading, but the 

 logically coherent way in which the descriptive facts 

 and theoretical deductions are marshalled so as to lead 

 the reader step by step from the first discovery of a 

 compound up to the latest constitutional formuhc for the 

 whole group. The evidence which has led to the adop- 

 tion of any particular formula is given in detail, with biblio- 

 graphical references in the foot-notes. If educationists 

 of the old school should at any time challenge (as they 

 have before now) the value of modern science as a mental 

 discipline, we may confidently ask them to place this 

 book in the hands of a student who has mastered the 

 elementary principles of chemistry and request him to 

 read conscientiously through any one of the sections and 

 follow the work which the investigators have carried out 

 in arriving at the results given. If after this he is not 

 inspired with a desire to become a worker himself, or if 

 he fails to see the logical connection of the various dis- 

 coveries which have culminated in the present state of 

 knowledge, his case may be dismissed as hopeless, and 

 some non-chemical career recommended.' 



The general plan of the English original is, of course, 

 well known in this country ; but it may be useful in con- 

 nection with the above eulogistic statements to invite 

 attention to the details of treatment of one or two 

 groups taken at random. On p. 80, for example, there 

 commences the section dealing with six-atom rings con- 

 taining one nitrogen atom. This section comprises 

 seven groups, viz. pyridine and homologues and iso- 

 merides ; hydropyridines ; quinoline and homologues and 

 hydro-derivatives ; the acridine group ; phenanthridine 

 and chrysidine group ; quino-quinoline and naphthino- 

 line group ; and the isoquinoline group. The first only 

 of these need be taken by way of illustration. The 

 occurrence of the pyridine bases from the historical 

 point of view is first considered, and a summary of the 

 early work of Runge, Hofmann, Thomas Anderson and 

 other investigators of " Dippel's oil" and the coal-tar 

 bases is given in chronological order. A short para- 

 graph on the mode of formation of pyridine bases by the 

 destructive distillation of animal matter explains the 

 theory first promulgated by Weidel and Ciainician that 

 the bases originate in this process from unsaponified fats, 

 the glycerol complex being essential for the pyrogenic 

 synthesis of the bases. Then follows a section on the 

 separation of the bases from bone-oil and from coal-tar, 

 the so-called " light oil " of the latter being at present 

 the chief source of pyridine and its homologues. 



lown to ihe writer used to t.ilce gre.-il 

 _ _ \ organic chemistry, althuugl) be had 



no practical acquaintance with the science. He considered the methods 

 of arriving al constitutional fortnuix as masterpieces of scientific reasoning. 



1 A distinguished mathematit 

 pleasure inre.-idmg original paper: 



The discussion of the constitution of pyridine occupies 

 nine pages, full consideration being given to this subject 

 on account of the important position which this base 

 holds as the type of a series which comprises so many 

 members and to which many natural alkaloids are re- 

 lated. The first formula considered is that of Korner 

 and Dewar, corresponding to KekuM's benzene ring 

 formula. Of the various formuhe proposed as alterna- 

 tives, that of Riedel and of Lieben and llaitinger, in 

 which there is cross linkage between the nitrogen and 

 the opposite y-carbon atom, is alone considered as having 

 any serious claim. The formuUe corresponding to the 

 "prismatic " and "diagonal" benzene formuhu are dis- 

 missed in very brief paragraphs, the latter being con- 

 sidered as disproved by the (unpublished) spectrometric 

 researches of BrUhl. The "centric" formula proposed 

 by Bamberger, and corresponding with the centric 

 formula of benzene, is regarded as beyond the possi- 

 bility of experimental proof, and, like the corresponding 

 benzene formula, is considered to be outside all analogy. 

 On the whole, while admitting that a decisive proof of the 

 constitution is yet wanting, the original formula of Korner 

 is shown to be inost in harmony with the known facts 

 and is adopted throughout the work. 



The constitutional formula of pyridine — the parent 

 compound of the series — having been thus threshed out, 

 the following section is devoted to the question of 

 isomerism and orientation among the derivatives. The 

 synthetical formation of pyridine compounds is next dealt 

 with. Taking the various methods in the order given, we 

 have the formation of pyridine homologues by heating 

 aldehydes or ketones with aldehyde-ammonia, acetamide, 

 ammonium phosphate, &c,, as first observed by v. Baeyer 

 and Ador in 1S70; then follows the general method of 

 Hantzsch (18S1), which consists in condensing /^-keto- 

 compounds (such asacetoacetic ester) with aldehydes and 

 ammonia, and the extension of this method to diketones 

 by Beyer and Knoevenagel (1891 and 1898). Another 

 general method, discovered by Claisen in 1893, consists 

 in the condensation of methenyl derivatives of certain 

 3-diketo-conipounds with ammonia. Ladenburg's intra- 

 molecular formation of the a- and y-homologues by the 

 action of heat on pyridinium methyl iodide and the 

 formation of oxypyridines by the action of ammonia on 

 a- and y-pyrone derivatives are next considered, and 

 attention is directed finally to the remarkable formation 

 of pyridine derivatives from pyrrole and its homologues 

 by the action of halogen-derivatives of methane on the 

 potassium or sodium derivatives of the pyrroles as ob- 

 served by Ciamician and his colleagues (1885-1887). 

 The mechanism of all these synthetical processes is, of 

 course, explained as far as known and illustrated by 

 formula'. After a few pages devoted to the general 

 properties of the bases of the series, the description of 

 the individual member? is given in exhaustive detail. 

 Beginning with pyridine itself and ending with dipyridyl, 

 this descriptive part extends over 157 pages. 



The chemistry of any of the groups dealt with in the 

 present work can be systematically followed out by those 

 who make use of these volumes either for the purposes of 

 reference or in order to make themselves acquainted with 

 the actual state of knowledge down to the date of pub- 



NO. 1672, VOL. 65] 



