December 21, 1911] 



NATURE 



239 





mention altogether. The general position of the science 

 was but little advanced beyond where Graham in 

 especial, and others, such as Frankenheim, Liidwig, 

 Cloetta, and Payen, had left it half a century earlier. 

 Outside Prof, van Bemmelen's work a few scattered 

 papers, mainly on the precipitating- power of salts, or 

 on the imbibition of water by organic jellies, made up 

 the literature of the period. Biologists as a class 

 seemed to have forgotten even the name colloid. 



The sixty-two original papers gathered into the 

 volume before us is eloquent testimony to the change 

 which has taken place. The colloidal state has be- 

 come the vogue, and any departure from simple linear 

 relationship in the equilibrium between states of 

 matter is in danger of being called colloidal — sub- 

 class adsorption — and so receiving summary and satis- 

 factory explanation. 



The historical position is, however, strictly logical, 

 as indeed it must be if it is, in fact, a development 

 of ideas. In the 'fifties and 'sixties of last century 

 much work and speculation were devoted to the col- 

 loidal state; Frankenheim 's forgotten paper of 1850, 

 for instance, deserves to rank with Graham's master- 

 work. But the movement soon spent itself for lack 

 of foundations to build upon. 



The present era begins in 1873 with the appearance of 

 the remarkable synthesis which van der Waals effected 

 between the Laplace- Young theory of self-attractive 

 matter, purely statical in character, and the doctrines 

 of molecular kinematics as Clausius especially had 

 developed them ; and in 1875, with the equally re- 

 markable extension of the theory of energy to include 

 cliemical potential which was made by Willard Gibbs. 

 These, together with van 't HolT's extension of the 

 gas laws to solutes and Arrhenius's conception of 

 electrolytic dissociation, opened the way for a great 

 mass of work on the equilibrium between different 

 states and different kinds of matter which expanded 

 molecular physics into what is now called physical 

 chemistry. This movement in turn has largely spent 

 itself, unfortunately before it has given us a trust- 

 worthy specification of the distribution of energy in the 

 fluid and solid states, and the study of the equilibria of 

 matter in mass has, in one direction, been largely 

 replaced by the study of heterogeneous systems in 

 which one at least of the states is not present in mass 

 at all, for this is the distinctive feature of what is 

 called the colloidal state. 



The papers in the memorial volume are forcible 



evidence of the multitude of problems connected with 



the colloidal state. Surface energy, the condensation 



of matter on to interfaces, osmotic pressure and 



r. dialysis, the physical state of soils, colloids in 



Jgeology, viscosity, precipitation, and contact potential 



all are dealt with. The subject-matter of the paper 



by M. Duhcm, which opens the series, must have 



been peculiarly grateful to van Bemmelen, for it is a 



protest against the application of thermodynamics to 



colloids on the assumption that they are multiphase 



systems. Twelve years ago the writer of this notice 



received from Prof, van Bemmelen a long letter of 



^protest against any attempt to apply the phase rule 



to colloids, and the protest was in the main just. 



JEqually favourable must have been his reception of 



NO. 2199, VOL. 881 



Malfitano's protest against certain arbitrary dis- 

 tinctions which have become current, chiefly the dis- 

 tinction between chemical combination and adsorption. 

 The distinction may have to be made, but it needs 

 more subtle treatment than it usually receives. 



Van Bemmelen's first work on colloids was his 

 paper of 1877 on the absorptive property of soil, his 

 last the paper, "Die Absorption, X.," of 1909. He 

 was nearly fifty, an age when many cease active 

 research, before he began his life-work. As 

 van Bemmelen was led to colloids by his study 

 of soils, it is but fitting that the volume should contain 

 an important group of papers on colloids of the soil 

 and in geology. Rohland, Hissink, Leopold, van 

 Baren, Ehrenberg and Pick, Holwerda and Hudig 

 write on these subjects. M. le Chatelier deals with 

 the mechanical properties of mixtures of solid and 

 liquid in a paper which is remarkable in that it makes 

 no mention of Osborne Reynolds's work. 



It is not possible to accord even the briefest notice 

 to all, and contributions by Pappada, Tamman, Barus, 

 Jordis, Freundlich, Spring, Svendburg, Bredig, 

 Ringer, Schreinemakers, Lorentz, and others must be 

 passed by with the remark that, as many of them 

 will not appear in print elsewhere, the volume must 

 be consulted by all workers on colloids. 



His eightieth birthday saw van Bemmelen stricken 

 with what proved to be his last illness. His modest 

 soul was, above all whom the writer has known, 

 superior to the need of praise. Thirty years' patient 

 labour in a neglected field of science proves this. Yet 

 one likes to think that so abundant testimony to 

 regard and esteem brought joy and courage in those 

 last hours. W. B. Hardy. 



lUE ANALYSIS OF DYES AND DYED 

 MATERIALS. 

 Identification of the Commercial Dyestuffs : being 

 vol. Hi. of a Method for the Identification of Pure 

 Organic Compounds by a Systematic Analytical Pro- 

 cedure based on Physical Properties and Chemical 

 Reactions. By Prof. S. P. MuUiken. Pp. vi + 274. 

 (New York : John Wiley and Sons ; London : Chap, 

 man and Hall, Ltd., 1910.) Price 21s. net. 



THE identification of natural or artificial dyestuffs 

 either as such or in association with textile 

 fibres, colour lakes, paper, food, or other articles, is 

 a problem which at the present day presents many 

 difficulties. Twenty or thirty years ago the number 

 of dyestuffs was so small that their identification by 

 an expert was a simple enough matter, but the enor- 

 mouslv greater number of artificial dyestuffs now in 

 use and the rapid rate at which this number is daily 

 augmented, has not only greatly increased the diffi- 

 culty, but also the need of trustworthy means 

 of analysis. The dyer with many hundreds 

 of dyestuffs now at his command is able to 

 match any particular shade in a variety of 

 different ways, but since the fastness for the purpose 

 in view depends entirely upon a suitable choice of 

 colouring matters, it becomes particularly important 

 that in matching an approved pattern it should bo 

 possible not only to reproduce the shade, but also to 



