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to practical application in the laboratory, for example, although the dehydra- 

 tion of alcohol by making use of the minimum-boiling ternary mixture 

 benzene-alcohol-water is described, no mention is made of the application 

 of this principle to the removal of water during esterification. 



The technical application of distillation processes is new matter, and 

 each branch has been dealt with by one or more \vriters who have special 

 experience in the particular field under consideration. A fairly uniform 

 method of treatment has been maintained throughout this section ; a short 

 introduction dealing with the sources of raw material is followed by a descrip- 

 tion of the distillation methods commonly in use with diagrams of the 

 various types of plant, tables of relevant data, and some account of special 

 difficulties and problems which have to be considered. Chapter XL, on 

 Steam Distillation, in the section on Essential Oils, rectifies an important 

 omission in the general part of the book where this subject is very much 

 neglected. The wisdom of adding descriptions of plant is perhaps open to 

 doubt. This occupies more than half of the book, and it is doubtful if the 

 honours student of chemistry gains much from such information ; a few 

 days in the works w^ould be of more value than much reading, especially as 

 exigencies of space, etc., often lead to modifications in plant design, and 

 change is so rapid that any textbook is soon out of date. One feels the 

 particular force of this objection in the very large increase in cost of the 

 book over the original Fractional Distillation. The theoretical part should 

 be read by every student of chemistry, but the price of the new edition has 

 placed it beyond the reach of many who have not ready access to a good 

 chemical library. On the other hand, as with most technical textbooks, 

 insufficient details of plant are given to make this part of any great value 

 to the specialist in technical distillation. 



O. L. B. 



The Volatile Oils. Vol. III. By E. Gildemeister and Fr. Hoffmann. 

 Second Edition by E. Gildemeister. Authorised translation by 

 Edward Kremers. [Pp. xx + 777, with 5 maps, i table, and 

 numerous illustrations.] (London : Longmans, Green & Co., 1922. 

 Price 32s. net.) 



This volume completes the English translation of the second edition of 

 Gildemeister and Hoffmann's well-known book, compiled under the auspices 

 of Schimmel & Co., and concludes the description of the individual essential 

 oils begun in the second volume. The work, now grown to three large 

 volumes, is a wonderful repository of information on the origin, production, 

 properties, and composition of the essential oils, not only those of com- 

 mercial importance, but of practically all those which have been extracted 

 even if only on an experimental scale. It is difficult, therefore, to imagine 

 how anyone interested in this branch of chemistry can deny himself the 

 convenience of having these volumes on his shelves. The large number of 

 references to work carried out in Schimmel & Co.'s laboratories indicate 

 the thoroughness of the research organisation of this firm, and the making 

 of their information available in so convenient a form is a custom which 

 might well be followed elsewhere to the advantage of the progress of chemistry. 

 Although each volume is indexed separately. Vol. Ill contains a general 

 index to the whole work extending to 100 pages; this greatly facilitates 

 reference. The general get-up of the book might be described as sumptuous, 

 but unfortunately the English, though not actually incorrect, is far from 

 idiomatic. Though this does not detract from the value of the book in the 

 scientific sense, it is a pity that so painstaking a work should be marred by 

 a fault so easily remedied. 



O. L. B. 



