NATURE 



597 



THURSDAY. OCTOBER 20, 1904. 



ODORIFEROUS SUBSTANCES USED IN 

 PERFUMERY. 

 Die Riechstoffe. By Georg Cohn, of Gorlitz. Pp. 

 viii + 2ig. (Brunswick: Vieweg und Sohn, 1904.) 

 Price 6 marks. 



THIS useful little monograph is a section, published 

 in separate form, of Bolley-Engler's " Handbuch 

 der chcmischen Technologie." It is not easy to find 

 ;i single expression in English which could be re- 

 garded as the precise equivalent of the German " Riech- 

 sloff " in the sense used by the author. The term as 

 here employed is meant to apply to odorous substances 

 of a pleasant smell and of definite chemical composition 

 —in other words, to chemical individual compounds 

 h.iving a more or less fragrant odour. It is obvious 

 tliat the word perfume does not apply, because a per- 

 fume is generally a mixture of various odorous and 

 non-odorous compounds, this being invariably the case 

 with natural perfumes or fragrant plant oils. 



The information contained in the present work is to 

 be found in the larger treatises dealing with this sub- 

 ject, the works of Gildemeister and Hoffmann in 

 Germany, of Charabot and his colleagues in France, 

 .•md of Sawer in this country being familiar to all 

 who are interested in this branch of chemical tech- 

 nologv. The arrangement of the subject-matter by 

 Herr Cohn. however, and the inclusion of the later 

 discoveries entitle the little work under notice to take 

 rank as an original contribution to the literature of 

 this branch of applied organic chemistry. In fact, 

 taking into consideration the large amount of inform- 

 .-ition compressed into the volume, and the completeness 

 with which the ground has been covered within a 

 comparatively small compass, it may be fairly claimed 

 that the treatment is more scientific and less technical 

 than in the standard treatises referred to, and chemists 

 w ho wish to get a general idea of the development of 

 their science in this newer field will find the work of 

 Herr Cohn a very valuable compendium. 



The book is divided into ten chapters and an 

 appendix. After defining the term " Riechstoff " in 

 the sense above indicated, the literature of the subject 

 is given in the second chapter, not the least valuable 

 portion of which is a tabulated list of German patents 

 classifii'd under the chemical families to which the 

 patents relate, such as alcohols, ethers, esters, alde- 

 hydes, ketones, &c. In the third chapter the historical 

 development of the industry is dealt with, and it is 

 pointed out that while perfumery as an art is of 

 extreme antiquity, the scientific, i.e. chemical, history 

 of the compounds employed is a comparatively recent 

 development. The same may be said, it is perhaps 

 hardly necessary to point out, of the tinctorial industry, 

 which existed as an art ages before it came within the 

 province of chemical science. The parallelism between 

 these two branches of technology does not, however, 

 end with this historical analogy, since the development 

 of synthetical chemistry has enabled many natural 

 odorous compounds to be made more economically than 

 I hey can be obtained from natural sources, while many 

 NO. 1825, VOL. 70] 



such compounds unknown in nature have been 

 synthesised in the laboratory and transferred to the 

 factory. The author gives (pp. 20-21) a list of twenty- 

 one firms 'which are engaged partially or wholly in 

 the manufacture of natural or synthetical perfumes. 

 Of these, three are French, and the remainder German 

 and Swiss. It is not apparent why English and other 

 manufacturers have been excluded. The writer of 

 this notice has a very distinct recollection, when ex- 

 amining the chemical products at the Paris Inter- 

 national Exhibition in 1900, of seeing some very good 

 exhibits of perfumes by English and colonial manu- 

 facturers. It is true that in the application of chemical 

 science to the industry Germany and France are far 

 ahead of this country, but this does not do away with 

 the fact that we have a few factories here which ought 

 at any rate to figure in any list having for its object 

 the instruction of the public as regards the present 

 state of any particular industry. 



The fourth chapter, dealing with the occurrence of 

 odorous compounds in nature and with plant physi- 

 ology, is of particular interest. A list, occupying 

 nearly nine pages, contains the names of all the plants, 

 arranged under their botanical orders, which yield 

 ethereal oils. Another set of tables, occupying twenty- 

 one pages, gives at a glance the name of the ethereal 

 oil, the part of the plant from which it is obtained, 

 the botanical source, the yield per cent., the physical 

 constants (sp. gravity and rotatory power), and the 

 chemical constituents. These tables thus summarise 

 in synoptical form the present state of knowledge of 

 plant oils, and in view of their importance it is much 

 to be regretted that the printing has not been arranged 

 in a less confusing way. The entries, as read horizon- 

 tally, run across both pages, and by the time the eye 

 has reached the last column, containing the chemical 

 constituents of the oil — to many readers the most 

 important item of information — the connection with the 

 particular oil named in the first column is lost or 

 rendered ambiguous, and the entry has in many cases 

 to be traced back again to make sure which oil con- 

 tains such or such constituents, ^^'e are all familiar 

 with, and have often been led astray by, this want of 

 precise correspondence between the horizontal entries 

 running across both pages of a railway time-table. If 

 in future editions the horizontal entries could be 

 divided by horizontal lines running across both pages 

 there would be no ambiguity, and the tables would be 

 very much enhanced in value. 



An interesting point to which the author directs 

 attention is the rarity of the ethyl group in natural 

 ethereal oils. Methyl, propyl, allyl, propenyl, are all 

 of widespread occurrence in the molecules of natural 

 organic compounds — ethyl occurs but in a few ex- 

 ceptional cases, and some of these are doubtful. We 

 could add many to the few cases of the occurrence 

 of ethyl in natural products given by the author, but 

 his general statement is nevertheless correct so far as 

 our present knowledge goes. Extreme advocates of 

 the temperance movement might even find scientific 

 justification for their position in this fact, which is 

 stated by Herr Cohn in the form of an aphorism : — 



" Die Natur hat einen horror vor dem Alkohol " 

 (p. 28). 



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