August 4, 1923] 



NATURE 



157 



a detailed account of the new National Physical 

 Laboratory standard spectrometer. Spectrophoto- 

 metry forms the subject of another article by Dr. 

 K. S. Gibson^ of the Bureau of Standards. 



Major E. O. Henrici deals with spirit-levels and 

 surveying. A recent development which does not find 

 a place is the shaping of the level-tube so that the 

 length of the bubble becomes independent of tempera- 

 ture changes. Prof. Horace Lamb contributes a short 

 note on the vibrations of strings. 



Prof. R. A. Sampson^ Mr. T. Smith, and Dr. J. S. 

 Anderson give between them an excellent and up-to-date 

 treatment of telescopes, while Sir Richard Glazebrook 

 himself is responsible for a number of short articles on 

 optics. The volume concludes with an uninitialled con- 

 tribution dealing comprehensively with the measure- 

 ment of wave-lengths, which we gather from the 

 list of contributors is by Dr. W. F. Meggers, of 

 the Bureau of Standards. Dr. Meggers brings out 

 in a useful summary table the striking fact that the 

 range of electromagnetic waves known to science 

 extends to more than 40 octaves, from the gamma rays 

 of radium on one hand to the wireless and " electric " 

 waves on the other. Since this article was written 

 the gap of four or five octaves between ultra-violet 

 and X-rays has been bridged, and now the only un- 

 explored interval is one of two octaves between the 

 infra-red and wireless waves. 



We have perforce had to omit mention of many 

 excellent contributions, but the reader will perhaps 

 discern from what we have cited the quality of the 

 fare that is set before him. 



In conclusion, we consider that the substantial weight 

 of the various volumes lends support to the view that 

 they could advantageously be divided into two. We 

 wonder, too, whether the " dictionary " mode of inter- 

 polating headings in alphabetical sequence between 

 the various articles has much to justify it. Each 

 volume is provided with an excellent index which 

 could readily be made to serve every requirement, and 

 will normally be the first resort of any reader seeking 

 information. G. W, C. Kaye. 



The Thermal Decomposition of Wood. 



The Destructive Distillation of Wood. By H. M. 

 Bunbury. Pp. xx-i-320. (London: Benn Bros., 

 Ltd., 1923.) 35:?. net. 



ONE hundred and fifty million tons of " wood 

 waste " are produced annually, most of which, 

 it is claimed, finds no useful application. Possible 

 methods for the utilisation of this material are its 

 destructive distillation to give valuable products, its 

 employment directly as a fuel, its use in paper pro- 

 NO. 2805, VOL. I 12] 



duction, or its fermentation to produce ethyl alcohol. 

 The first application, and wood distillation generally, 

 although forming the subject of an ancient industry, 

 has not hitherto been taken as the sole title of an English 

 text-book. On account of the important economic 

 problem involved the author has much to justify his 

 effort, and from many points of view his book is a 

 success. The descriptions of plant and processes for 

 wood distillation and of stills and evaporators em- 

 ployed in the recovery of the distillation products are 

 lucid, and while technical details have been considered, 

 exactness in statement has been maintained. 



From an economic point of view the efficient working- 

 up of the products of distillation is all-important, and 

 naturally this problem has received careful attention. 

 The works chemist is confronted, among other 

 problems, with the isolation of various organic com- 

 pounds from his crude liquor condensate obtained 

 when wood is destructively distilled. This hetero- 

 geneous product contains, in aqueous solution, acids, 

 bases, alcohols, aldehydes, ketones and other sub- 

 stances, and in suspension, tarry matter of a highly 

 complex composition. The author enumerates more 

 than sixty compounds generally present, in addition 

 to many others found in the crude oil from soft wood 

 distillation. On distillation, after the acid products 

 are fixed, various azeotropic mixtures, both binary and 

 ternary, are formed, which makes the isolation of the 

 individual compounds difficult. 



The observations of Guillaume and Sorel on the 

 purification of alcoholic liquors generally by a steam 

 distillation method are not referred to, but develop- 

 ments from these researches are considered in detail, 

 particularly in regard to the production of pure methyl 

 alcohol direct from crude wood spirit. 



Wade and Merriman in their classical work on 

 constant boiling-point mixtures adopt the term azeo- 

 tropic for such mixtures instead of hylotropic as 

 proposed by Ostwald. Young and Lecat also prefer 

 the word azeotropic with its more defined meaning. 

 It is therefore to be regretted that in this volume the 

 older term is again introduced. The author writes of 

 a particular hylotropic mixture of 90 parts by weight 

 of acetone, and 10 parts by weight of methyl alcohol, 

 and later refers to this mixture as the " pure " or 

 " theoretical " methyl acetone. 



The author has given numerous flow sheets, but 

 these, it is hoped, may be developed in a future edition, 

 if possible on more quantitative hues. In the technical 

 records of the Ministry of Munitions the idea of flow 

 sheets and flow diagrams, not only qualitative but 

 also quantitative, have been emphasised, and should 

 set a standard. 



The analytical methods are condensed into a dozen 



E I 



