December 9, 1920] 



NATURE 



465 



Kinetic Theory. 



1 Kinetic Theory of Gases and Liquids. U\ Prof. 

 R. D. Kleeman. Pp. xvi + 272. (.New York: 

 John Wiley and Sons, Inc. ; London : Chapman 

 and Hall, Ltd., 1920.) I'rii e i6s. 6d. net. 



THIS book deals mainly with the "free path 

 phenomena " in the kinetic theory of gases, 

 but this department of the subject is compre- 

 hensively treated. Whether the chief object of 

 such a work — namely, to gain some information 

 about the intermolecular forces — can ever be at- 

 tained without taking account of the other parts 

 I till Mibject seems somruhat doubtful, 

 i'hc Ixxiy of the book is concerned with the 

 various forms of transfer which occur in gases 

 and liquids — transfer of energy or heat conduc- 

 tivity, transfer of momentum measured by the 

 viscosity, and transfer of matter as evidenced in 

 liffusion. Some ten years ago it might have 

 ~<emed that it was in these properties, which are 

 : measure of the free path, that the key to the 

 riddle of molecular interaction was to be found. 

 'I'o-day, one is inclined to feel, they have l>een over- 

 emphasised when such a subject as the law of 

 i((uipartition of energy is given only a couple of 

 pages, and the fundamental problem of the reason 

 why it breaks down is not considered at all. In 

 particular, a statement (pp. 32-33) that "it 

 - unnecessary and futile to endeavour to estab- 

 lish the law of equipartition of energy on assump- 

 tions relating to the interaction of molecules, when 

 the law follows directly from the fact that a mole- 

 r nif is lontinually radiating heat energy," should 

 II i!i\ ; .1 occur in a modern book intended for 

 iiiiiversliy readers. The statement entirely 

 begs the question of defining the temperature. 

 The "fact," if such it be, should be established 

 l)y more adequate proof than by a reference to the 

 hot air rising from a surface, and the main point 

 -namely, that the law which is represented as 

 -') obvious, in reality does not hold — should be 

 cntioned. Far from being "unnecessary and 

 t utile," it is one of the most urgent problems in 

 physics to examine why a law which can be proved 

 lo be a necessary consequence of the most general 

 -sumptions in dynamics should not hold in actual 

 act ice. 



Apart from these and allied problems — e.g. the 



iiemical constants of substances and the change in 



ii- ratio of the specific heats of hydrogtin at low 



inperatures the kinetic theory is admirably 



. atcd. Mvcn the kinetic theory of electrons in 



ii-tals is developed, though it is to be regretted 



it the essential fallacy of treating these as n 



rfect gas is not emphasised, and the uninitiated 



NO. 2667, VOL. 106] 



reader is left to believe that there are 2- 10^* free 

 electrons per unit volume, when such a number 

 would involve a specific heat about fifteen times 

 a.s great as is actually observed. 



In spite of these omissions, however, the book 

 is certainly to be recommended, especially to those 

 who are interested in free path phenomena, 

 although these alone are scarcely able to throw 

 light on the process of molecular interaction until 

 the quantum problem has been solved. 



A Monograph on Margarine. 



Margarine. By W. Clayton. (Monographs on 

 Industrial Chemistry.) Pp. xi+187. (London: 

 I-'jngmans, Green, and Co., 1920.) Price 14.V. 

 net. 



CURIOUSLY enough, the introduction of arti- 

 ficial butter dates from the early days of the 

 Franco-Prussian War, and, while the butter and 

 lard substitute industry has been carried on on a 

 small scale since then, margarine, as an industry, 

 became ot prime importance to the nation only 

 during the Great War, Many important improve- 

 ments have been made, and these are set forth in 

 the book under review. 



In the first part a brief account of the oils em- 

 ployed in the manufacture of margarine is given, 

 and some less known oils, such as Cohune oil, tea- 

 seed 'oil, and Babassu kmul diI, are mentioned. 

 Later chapters deal with hydrogenised oils, and 

 for the present writer's views on this subject 

 reference may be made to the notice of I't. <'i. 

 Martin's book on "Animal and V'egetablc IJiLs, 

 Fats, and W^axes " in Xmirk of September 9 

 last. 



Interesting chapters treating bacteriologically of 

 the pasteyrisation of milk and of the production 

 of " starters " for the ripening of the milk follow. 

 .\ brief description of the actual manufacturing 

 operations of forming an emulsion between the 

 mixed oils and the milk is then given. The theory 

 of emulsiiication is, of course, very well stated, as 

 Mr. Clayton is an authority on colloid chemistry. 

 His opinions are therefore of great interest, and 

 when they have been digested bv technical 

 chemists, very valuable results shuulil arise in 

 their industrial application. 



In regard to the causes of rancidity in fats, 

 Mr. Clayton seems inclined to accept the view that 

 they result from bacterial actions on the glycerides. 

 We believe that rancidity is due, in the first in- 

 stance, to (he formation of supcr-oxides of the 

 unsaturated glycerides and their sub.sequcnt de- 

 composition with the production of aldehydes and 

 aldo-acids by the action of moisture, aided, per- 



