NATURE 



433 



THURSDAY, MARCH 7, 1889. 



TOLLENS'S " CARBOHYDRA TES." 

 Kurses Hatidbuch der Kohlenhydrate. By B. Tollens. 

 (Breslau : Maruschke and Berendt, 1888.) 



THIS admirable /n'V« of the chemistry of the carbo- 

 hydrates is a model work of its kind. It is not 

 merely a lucid account of this well-marked group of 

 carbon compounds, but has the rare merit of preserving 

 its facts and conclusions in their original guise — that is, 

 as the offspring of research. Too often, the authors of 

 treatises on experimental science, more especially of the 

 genus text-book, are compelled to present their subject 

 in such a way as to produce the impression that pheno- 

 mena follow from laws, rather than that laws have 

 followed from the phenomena which they generalize. 

 This is no doubt justifiable, and in the end perhaps not 

 seriously harmful, since the student is soon brought by 

 his laboratory work to an appreciation of the perspective 

 of his science, and to the correction of any superstitions 

 which may have been engendered in his mind as to its 

 origin and up-building. In the book before us, on the other 

 hand, every fact is stamped and recorded as the contri- 

 bution of a worker. A specialist, such as the author, 

 engaged in active research in the field which he pauses, 

 as it were, to describe, must write from the point of view 

 of the worker ; and hence it is that in the 330 short pages 

 into which his account is condensed, we have over 1300 

 references to original memoirs. The impression produced, 

 moreover, is that he has submitted this huge mass of 

 experimental evidence to a searching examination, of 

 which the matter of the book is the valid survival. It is 

 to be hoped that the author's example will be generally 

 followed. It is becoming less and less possible to keep 

 pace with research in the many special branches into 

 which chemistry is diverging. But if specialists will, as 

 the author has done, unburden themselves to an imagin- 

 ary interviewer, the task, which is laid upon us all, of 

 keeping up with the progress of discovery and research 

 will be both sweetened and lightened. 



In proceeding to notice more particularly the contents 

 of the work, we are struck, first, with its method of classi- 

 fication. The treatise is divided into two parts, the first 

 dealing with the carbohydrates proper, together with 

 such other comparatively inert compounds, e.g. arabinose, 

 as stand in close connection with them ; the second is 

 an account of the derivative acids and their lactones 

 (" saccharines "). 



The first section sets forth the general or typical pro- 

 perties and characteristics of the group, with an account 

 of their origin in the plant, the evidence as to their 

 molecular weight and constitution, their synthetical 

 formation in the laboratory (phenose, acrose), their iso- 

 lation in the pure state, their optical properties, and 

 the various methods adopted for the determination of 

 specific rotation. Then follows in outline the scheme 

 of classification. The various groups under which the 

 compounds are ranged are: (i) monosaccharides, or 

 glucoses, CoHjuOg (dextrose, laevulose, &c.) ; (2) disac- 

 charides, or saccharoses, CjjHjoOu (cane-sugar, maltose. 

 Vol. xxx;x.— No. ioio. 



&c.) ; (3) polysaccharides — {a) crystalline (raffinose, 

 C36HB4O32 • ioH.,0, and lactosin, CjgHgoOj,) ; {b) non- 

 crystalline or saccharocolLoids, «&c., CgHj^Oj ± MH3O 

 (starch, inulin, gums, celluloses, pectone substances) ; (4) 

 the somewhat miscellaneous group of substances which, 

 although lacking some one or more of the group charac- 

 teristics, are yet closely related to the carbohydrates — 

 {a) in which H : O = 2 : I (arabinose, cerasinose, inosite, 

 formose) ; {b) in which H : O > 2 : i (quercite, pinite, 

 mannite). 



Having thus forecast the order of treatment, the author 

 plunges at once into the work of particular description. 

 Beginning with dextrose, we have at the outset {a) a terse 

 but minute account of the laboratory method of isolation 

 from saccharose, also of the method of manufacture from 

 starch ; {b) certain physical properties of the anhydride 

 and monohydrate, with solubilities and a table of specific 

 gravities of aqueous solutions ; {c) behaviour towards 

 polarized light, — after a brief discussion of the variations 

 between the numbers of different observers and their 

 cause, we have the author's final selection of the 

 formulae, (i) for the anhydride (a)^ = 52*5 -|- O'oi 8796 P 

 + 0-00051683 Pj, and (2^ for the monohydrate (a^, 

 = 4773 + 0-015534 P 4- 0-0003883 P2, P being the per- 

 centage of substance in solution ; {d) the results of 

 heating at various temperatures ; {e) actions of acids ; 

 (/) actions of alkalies ; {g) action of nascent hydrogen 

 (conversion into mannite) ; ill) action of the halogens and 

 various forms of oxygen ; it) action of oxidizing (metal- 

 lic) oxides ; and {k) its several fermentations. Then 

 follows a detailed account of the derivative compounds 

 of dextrose : (a) with bases ; (b) with negative radicles ; 

 (c) ethereal compounds ; (d) hydrazine derivatives ; (e) 

 compounds with aromatic amines ; (f) with metallic 

 salts ; (g) with hydrocyanic acid (conversion into normal 

 heptoic acid). The author then gives a detailed account 

 of analytical methods, i.e. (i.) identification by qualitative 

 reaction ; (ii.) estimation by polarization of the various 

 oxidation methods (Cu, Hg, and Ag salts), and by fermenta- 

 tion. We have reproduced these heads, under which the 

 chemistry of dextrose is treated, as characteristic of the 

 method of the book. The typical saccharose, cane-sugar, 

 is dealt with in even greater detail, the author giving a 

 complete though brief account of the process of prepara-' 

 tion from beet, with illustrated descriptions of the manu- 

 facturing plant, as also of the polarization instruments 

 commonly employed for sugar estimation, viz. the Soleil- 

 Ventzke-Scheibler, and that of Schmidt and Hausch, 



Of the amorphous polysaccharides or saccharocolloids, 

 starch is treated at considerable length. The views of 

 physiologists as to its origin in the plant are briefly dis- 

 cussed. Its resolutions by the various hydrolytic reagents 

 are dealt with in detail, and due prominence is given to 

 the results of the researches of O'Sullivan and of Brown 

 and Heron. Special details are given of the methods of 

 estimation of starch in farinaceous raw materials, with a 

 description of the Lintner-Soxhlet apparatus for carr)'- 

 ing out the acid hydrolysis. As the starch group is 

 characterized by resolution into dextrose, so the inulin 

 group, next described, appear to be poly-derivatives of 

 laevulose. A third is composed of substances yieldiiVg 

 galactose as a product of resolution (laivulan, galactan. 

 Carragheen mucilage), while a fourth comprises such 



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