October 6, 192 1] 



'NATURE 



171 



The delay in a majority of cases would prevent 

 skilled disinfection from being effective. From 

 an economic and efficiency point of view, there- 

 fore, we are of opinion that the Health Depart- 

 ment of Pennsylvania has wisely adopted " self- 

 disinfection " as one means of controlling 

 venereal disease, and it is to be regretted that the 

 offer of the Society for Prevention of \'enereal 

 Disease, backed by the names of so many dis- 

 tinguished physicians and surgeons, should have 

 met with a curt refusal from the Ministrv of 

 Health. 



L'Espace dans la Chimin. 



The Principles of the Phase Theory. Hetero- 

 geneous Equilibria bet-ween Salts and their 

 Aqueous Solutions. By Dr. Douglas A. 

 Clibbens. Pp. xx + 382. (London: Macmillan 

 and Co., Ltd., 1920.} 255. net. 



AMONG the gifts which the older science of 

 physical chemistry gave to chemists, un- 

 doubtedly the graphical treatment of heterogene- 

 ous equilibria, founded on the phase law of 

 Gibbs, will always occupy a prominent position. 

 Begun and extensively developed by Roozeboom 

 and van't Hoff, this most valuable and elegant 

 branch of science has been carried on in a masterly 

 fashion by Schreinemakers. Special and most 

 important developments of it are due also to 

 Cohen and to Smits. 



So great and conspicuous is the work of these 

 rive Dutch physical chemists that we may fairly 

 call the science of heterogeneous equilibria a 

 Dutch science. This statement is all the more 

 justified when we recollect that the theoretical 

 and experimental physics of the simpler systems 

 is very largely due to the work of the Dutch 

 physicists, van der Waals, Kamerlingh Onnes, 

 Kuenen, Keesom, and Crommelin, . etc. The 

 Dutch nation is indeed to be congratulated on 

 the splendid work which their men of science have 

 done in this field, and it is pleasant to observe 

 that Dr. Clibbens has dedicated the present 

 volume to Prof. Schreinemakers. 



The great power of the graphical treatment of 

 heterogeneous equilibria lies in its ignoration of 

 co-ordinates. In order to apply it we do not 

 require to know the co-ordinates which define the 

 inner mechanism of equilibrium in any phase. It 

 is not even necessary that the constituents of any 

 phase should be in perfect inner equilibrium. All 

 that is necessar>' is that the various phases should 

 be in equilibrium with each other — that is to say, 

 that the chemical potential of each component 

 should have the same value in all the phases, and 

 that the same thing should hold good for tem- 

 XO. 2710, VOL. 108I 



perature and hydrostatic pressure (at least in all 

 ordinary applications). 



We may say that what cartography is to the 

 geographer and land traveller, practical astro- 

 nomy to the navigator, and engineering drawing 

 and graphics to the engineer, the graphics of 

 heterogeneous equilibria is to the chemist. With- 

 out the maps made by other chemists and the 

 knowledge of how to do his own surveying and 

 map-making, the chemist of to-day will do much 

 useless wandering, and probably lose his way 

 entirely. 



It is a strange thing that, even after the lapse 

 of some thirty years, so little real attention is 

 devoted to the science of heterogeneous equilibria 

 in our instructional courses in chemistry at the 

 universities and higher technical schools. The 

 only people who take it seriously are the metal- 

 lurgists. From their closer connection with the 

 outside world they know that it spells business, 

 and very good business too ; but in reality it is 

 just as important for the chemist. Whatever 

 chemical work he does in the world, he will have 

 at some stage or other to separate heterogeneous 

 mixtures into pure constituents by crystallisation, 

 distillation, sublimation, and phase-distribution. 

 In designing chemical processes and plant he will 

 be asked by the engineer to specify what phases 

 will be present and in what amounts, under speci- 

 fied conditions of pressure, temperature, and con- 

 centrations of initial materials. The engineer, 

 accustomed to quantitative data and calculations, 

 will want the answer in figures. He does not 

 want any of the "tricky" work of Mary Ann 

 making the Sunday rice pudding, although that is 

 just what he gets at present from the majority 

 of chemists — even highly trained ones, who can 

 tell you what the inside of an atom looks like, 

 or what the camphor molecule would be like if it 

 would keep quiet and stand at attention. These 

 learned gentlemen resemble an engineer who has 

 " jumped " all his engineering drawing and 

 graphical statics, and taken to the study of rela- 

 tivity. Even the members of the "Argonaut " ex- 

 pedition had some sort of map in their great 

 quest. 



No man can really claim to be a well- 

 trained chemist nowadays unless he can handle 

 the theory and practice of a four-component 

 system as he would an ABC railway-guide. Alas, 

 how many of us can say that? We mean well, 

 but when it comes to the test we fall back 

 on the methods of Mar\- Ann. Every university 

 chemical institute should have a special laboratory 

 and a special drawing-office for the study of 

 heterogeneous equilibria. The reason for this is 



