DISPERSOIDOLOGY AND THE THEORY 

 OF von WEIMARN 1 



By S. C. BRADFORD, B.Sc. 



The Science Museum, South Kensington, London 



Since Graham laid the first foundation stones of the structure, 

 many significant additions have been made to our knowledge 

 of the chemistry and physics of colloids. The invention of the 

 ultra-microscope by Siedentopf and Zigmondy led to the in- 

 vestigation of Brownian movement by Smolukhovski, Svedberg, 

 and Einstein, and the demonstration of the actual existence 

 of molecules by Perrin. The theory recently elaborated by 

 v. Weimarn is an important extension of the main framework 

 of the science. Although Graham originally distinguished be- 

 tween crystalloid and colloid as distinct classes of substances, it 

 has gradually become evident that these terms should rather 

 be applied to differing states of matter, since, under suitable 

 circumstances, many typically crystalline substances can be 

 obtained in a colloid state. And it further appears that this 

 condition is characterised by the development of a relatively 

 enormous amount of surface, to which the distinctive properties 

 of colloids are traceable. 



V. Weimarn's researches completely demonstrate this view, 

 and his theory defines the main conditions which determine the 

 form in which a given substance shall occur. So that, provided 

 the necessary circumstances can be realised, it should be 

 possible to obtain a given substance in either desired condition. 

 The study of colloids therefore develops increasingly into a 

 consideration of specific surface, and the modifications of 

 physical and chemical properties produced by its variation. For 

 even chemical affinity appears as a function of the grain- 

 size of solid and liquid bodies, as may be exemplified by the fact 

 that gold in the finest state of subdivision is soluble in hydro- 



1 P. P. v. Weimarn, Zur Lehre von den Zustanden der Materie. Leipzig, 

 1914. 2 Bde. 



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