— 159 — 



duplicates of both these tables have been specially inserted in each 

 copy for practical laboratory purposes. 



The contents of the work are divided into the following sections: — 

 Historical introduction; — The preparation of odoriferous substances from 

 flowers, by extraction, enfleurage and maceration; — Principal constituents 

 of the essential oils, natural and artificial odoriferous bodies; — The 

 examination of essential oils. 



No. 21 of the Monographs on chemico-technical methods of manu- 

 facture, edited by L. M. Wohlgemuth (Wilhelm Knapp, Halle a. S. 1910) 

 consists of a work by Robert Leimbach, entitled u Die dtherischen OW' 

 (The Essential Oils) with a sub-title showing it to contain a short account 

 of the preparation and examination of these substances, and a classi- 

 fication of their more important characteristics. The book of about 

 300 pp. opens with a short historical review of the distillation of the 

 oils and an account of their chemical structure, and also touches upon 

 the part played by the oils in the organism of the plants, — a subject 

 to which but little attention has been paid so far, — as well as the 

 importance from the economic and cultural standpoint of the essential oil 

 industry. Next follows an account of the preparation of the oils by 

 distillation, separate chapters being devoted to the theory of the subject 

 and to certain peculiarities of the practice of distillation. The physical 

 and chemical examination of the oils is treated in detail. Then comes a 

 chapter containing a detailed statement of the known constituents of 

 essential oils, with their principal properties, and after that an enumeration, 

 in tabular form, of the oils themselves, giving for each oil the botanical 

 origin, the character of the raw material, the yield, the more important 

 constants and constituents, and the leading references in technical literature. 

 This section occupies about one-half of the book. The table as well as 

 the other information contained in the book represents the point at which 

 the chemistry of essential oils stood about the year 1907. 



Analytical Notes. 



Harvey and Wilkie 1 ) have published a paper on the index of refraction 

 of essential and fixed oils. They take up the correct point of view that 

 the determination of this constant is vastly more important in fixed oils 

 than in the very changeable essential oils, but that in certain circumstances 

 it may also be useful in the case of the latter, and deserves the more 

 recommendation because it is easy to carry out and requires only very 

 little material. But the incorporation of the index of refraction among the 

 requirements of a Pharmacopoeia is not to be advocated, in view of the 

 fact that this constant only plays a very subordinate part so far as the 

 determination of value is concerned. 



r ) Chemist and Druggist 76 (1910), 442, 



