ESSAY-REVIEWS 



SOME NEW ASPECTS OP COLLOID CHEMISTRY, by Ingvar 

 Jorgensen, Cand. Phil., D.I.C., on : Proteinstudier, I.-V., by Prof. 

 S. P. L. Sorensen, Meddelelser fra Carlsberg Laboratoriet. Vol. n. 

 [Pp. 364.] (H. Hagerup, Copenhagen, 1917. Price 8 kr. 25 ore. 

 English edition in the Press.) 



COLLOID chemistry is one of those unfortunate subjects in which textbooks appear 

 to be in advance of research. A perusal of recent continental works (I. Wo. 

 Ostwald : Grundriss der Kolloidchemie, Dresden, 1909. II. An Introduction to 

 Theoretical and Applied Colloid Chemistry, translated by Martin H. Fischer ; 

 London : Chapman & Hall, 1917. III. H. Freundlich : Kapillarchemie, Leipzig, 

 1909. IV. Kapillarchemie und Physiologie, Leipzig, 1914) gives the impression 

 that progress in the subject has been hindered by premature classification and 

 organisation. Too much stress has been laid on the colloidal condition ; " colloid 

 chemistry is not the science of colloidal substances, but the science of the col- 

 loidal condition of substances" (Wo. Ostwald), and the tendency has been to 

 generalise from experiments with suspensoids. Prof. Sdrensen's researches 

 on the proteins constitute a much-needed corrective to these tendencies of the 

 German school. 



The fundamental difference between suspensoids and emulsoids lies, according 

 to Sorensen, in the relation between the disperse phase and the dispersion medium 

 in the two classes. The properties of typical suspensoids depend essentially on 

 the surface relations between dispersion medium and disperse phase. The same 

 phenomena are met with also in emulsoids, but here surface action is only of 

 secondary importance, because the disperse phase of emulsoids reacts at the same 

 time in a purely chemical way with the dispersion medium. The fundamental import- 

 ance of Sdrensen's work lies in the way in which it is shown that the experimental 

 results obtained with emulsoids can be interpreted by exactly the same laws which 

 hold for true solutions. The degree of dispersion probably does not play the all- 

 important part which for example Wo. Ostwald assumes for it, and in any case it 

 cannot give a satisfactory explanation of the difference between suspensoids and 

 emulsoids. The explanation that this difference should be due to a solid disperse 

 phase in suspensoids and a liquid disperse phase in emulsoids, is insufficient in 

 view of the fact that colloidal systems are known with a suspensoid character but 

 with the disperse phase liquid (G. S. Walpole, Biochem. Journ. 8, 1914, P- 170). 

 It is possible that in emulsoids the degree of dispersion plays an important part in 

 regard to whether the capillary or purely chemical properties are dominant. If 

 the degree of dispersion is small the capillary properties may play an important 

 part, but in emulsoids with a high degree of dispersion the purely chemical pro- 

 perties are dominant and determine the character of the system. In the opinion 

 of Sorensen it is thus impossible to draw a sharp line of distinction between true 

 solutions, emulsoids, and suspensoids. The emulsoids in a way occupy an inter- 

 mediate position between true solutions and suspensoids. Suspensoids are 

 characterised by having a viscosity not very different from that of the pure 

 dispersion medium. There is a distinct difference of charge between disperse 



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