434 



NATURE 



[April 8, 1922 



not only very exhausting, but also frightfully expensive, 

 and greatly weakening the moral of our students." 



There is certainly an element of truth in this criti- 

 cism. In many universities students get so much 

 direct teaching by lecture, by tutorial expansion, and 

 by the performance of routine experiments to printed 

 orders, that they have little time or energy left for real 

 effective thinking. There is a tendency to forget that 

 a mere knowledge of apparatus and of methods of 

 experimenting does not make a physicist. The 

 physical imagination should be trained, and the highest 

 powers of mind called into play, and the student should 

 be encouraged to get into living touch with the creative 

 literature of the subject. This, of course, is not easy, 

 especially when the classes are large. What is wanted 

 is an accessible reading-room fully supplied with the 

 journals and other publications in which progressive 

 work is recorded. Students, if not overburdened by an 

 excess of class and laboratory attendance, would soon 

 come to appreciate the value and delight of thus getting 

 into touch with the vital problems of the day. 



Nevertheless, in the hands of a good teacher there is 

 nothing to compare with the lecture as a means of giving 

 a systematic theoretic view of the whole science treated, 

 and there is no better corrective to the extreme and un- 

 scientific utilitarianism which makes many a student 

 think that he is being taught what will be of no value 

 to him. Technical schools may narrow their teaching 

 to what seem at the time to be the absolute necessities, 

 but a university is intended to give engineering students 

 an all-round training in the fundamental sciences of 

 mathematics, natural philosophy, and chemistry. 

 Without these an engineer is only half equipped for his 

 calling. 



The Principles of Distillation. 



Distillation Principles and Processes. By Prof. Sydney 

 Young, with the collaboration of various authors. 

 Pp. xiv + 509. (London : Macmillan and Co., Ltd., 

 1922.) 405. net. 



THIS book is a new and amplified edition of the 

 author's well-known treatise on " Fractional 

 Distillation," first published in 1903. Prof. Sydney 

 Young is an acknowledged authority on the subject on 

 which he writes, and for many years prior to the appear- 

 ance of the first edition of his work, the principles under- 

 lying the separation of substances by distillation had 

 been investigated by him and the results communicated 

 to various scientific societies. But his book embodied 

 not only his own experience. Everything that was 

 known at that period concerning the science and art of 

 distillation was duly recorded and discussed, and the 

 relative merits of the various still-heads and other 

 NO. 2736, VOL. 109] 



forms of apparatus employed in the processes of 

 fractional distillation were carefully inquired into and 

 compared . The rapid development of organic chemistry, 

 pure and applied, during the latter half of the nineteenth 

 century was the immediate cause of the attention 

 which the subject then received. Distillation was 

 practically the only means available for the isolation 

 of the constituents of mixed liquids. The art of dis- 

 tillation is, of course, as old as any chemical process, 

 but the principles upon which its efficient appHcation as 

 a method of separation of complex liquids depend, were 

 very imperfectly understood. Prof. Young's book was 

 the first systematic attempt to explain these principles 

 and to illustrate their bea'-ing upon laboratory and 

 technical procedure. It has not only been of great 

 use to operative chemistry, but it has served to indicate 

 many points of theoretical interest concerning the 

 thermal behaviour of substances which, although they 

 may have no immediate utilitarian value, are certain to 

 influence practice in the future. 



During the two decades which have elapsed since the 

 appearance of the first and second editions of this work, 

 a considerable body of additional information has 

 been accumulated concerning its subject-matter, not, 

 perhaps, so much in the elucidation of fundamental 

 principk s as in the compilation of accurately observed 

 thermal values upon which the various mathematical 

 formulae which seek to generalise the facts of distilla- 

 tion depend. The present edition differs from its 

 predecessor in one important feature : it deals more 

 particularly with the technical applications of distilla- 

 tion. The book, in fact, is divided into two main 

 sections. The first is practically a reprint of the first 

 edition on " Fractional Distillation," extended and 

 brought up to date by the inclusion of all material facts 

 which have been made known during the last twenty 

 years. For much of this information we are indebted 

 to British workers, and the results of the valuable 

 investigations of Wade and Finnemore and of Wade and 

 Merriman are described in adequate detail. Wade's 

 unfortunate death in the full tide of his intellectual 

 vigour, when all his energies were concentrated upon 

 the development of an inquiry with which by training 

 and aptitude he was specially fitted to cope, was a 

 serious loss to science. 



An important addition to the work is a chapter on 

 sublimation. As the author points out, there is no 

 essential distinction between distillation and sublima- 

 tion, although at first sight the dissimilarity of the two 

 operations would seem to imply a difference. The 

 term distillation denotes the volatilisation of a sub- 

 stance and its condensation and recovery, drop by 

 drop : by subUmation is usually understood the direct 

 passage from the gaseous to the solid state without 



