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VI. Some simple Deformations of Homogeneous Partitioning s 

 of Space and the Increase of Internal Surface generated 

 thereby. By Emil Hatschek *. 



THE investigation to be described here was originally 

 undertaken with the object of determining whether the 

 generally received theory of the structure of gels (jellies) 

 was compatible with the elastic properties of these bodies. 

 This theory assumes that gels are systems of two liquid 

 phases having interfacial tension. 



Since a number of gels show marked, and within narrow 

 limits perfect, elasticity of form, it follows at once that, if 

 the theory is correct, this elasticity can be due only to the 

 interfacial tension of the phases, since either phase considered 

 singly possesses elasticity of volume only. Deformation of a 

 gel must lead to an increase of the interface or internal sur- 

 face, and the tendency of the system to return to its minimum 

 interface shows itself as elasticity. We can 5 therefore, with- 

 out at present, making any assumptions as to the geometric 

 character of the interface, at once say that — for, say, a tensile 

 strain W and elongation L — 



WdL = CtfS or W=C4|, 



dh 



where S is the interface and a constant containing both its 

 absolute size and the interfacial tension. If, therefore, we 

 can determine the function connecting elongation and in- 

 crease of surface, we can find the stress-elongation curve by 

 differentiation and can compare the curve so found with 

 experimental data. If the curves show marked disagreement 

 the theory of two liquid phases is at once untenable. 



As regards the shape of the interface, we have, of course, 

 to make assumptions, which, however, are very strictly 

 defined. If a system of two liquid phases is to have 

 npproximately the appearance and some of the properties of 

 a solid, we know from the behaviour of emulsions made by 

 Pickering and others that the disperse phase must occupy 

 almost the total volume — 98-99 per cent., — leaving only 

 1-2 per cent, for the continuous phase, which therefore can 

 form only a thin film separating polyhedra of the continuous 

 phase. Although such a structure can hardly be in stable 

 equilibrium, it can be shown by microscopic examination 



* Communicated by Dr. L. Silberstein. 

 G2 



