﻿the Adsorption of Ions. 323 



assuming the condition of adhesion, and which occasionally 

 leads under very favourable circumstances, as in the present 

 instance, to the combination of bodies simultaneously sub- 

 jected to this attraction." It is remarked further u that the 

 sphere of action of particles extends beyond those other 

 particles with which they are immediately and evidently in 

 union, and in many cases produces effects rising into con- 

 siderable importance.''' These remarks of Faraday mean, in 

 modern terminology, that there is a sort of combination at 

 the surface and that the transitional layer is more than one 

 molecule thick. The subsequent views are in a way develop- 

 ments of this conception. 



Gribbs treated adsorption from the standpoint of thermo- 

 dynamics. A number of important investigations has been 

 carried on by Milner (Phil. Mag. [6] xiii. p. 96 (1907)), 

 Lewis (PhiL Mag. [6] xv. p. 506 (1908)), ibid. xvii. 

 p. -466 (1909)), and Donnan and Barker (Prpc. Roy. Soc. 

 Ixxxv. A. p. 552 (1911)). The present position is that the 

 amount adsorbed is often considerably greater than what 

 could be expected from Gibbs's equation. 



J. J. Thomson (' Applications of Dynamics to Physics and 

 Chemistry ') showed that it follows from Laplace's theory of 

 capillarity that in the surface layer between two liquids, 

 chemical actions may take place which are absent in the 

 bulk of the liquids. 



Lagergren (Biliang K. Svenska Vet. Hand. xxiv. p. 11, 

 Xo. 115 (1898)) considers that adsorption in the surface of 

 solids in contact with aqueous solutions is due to the com- 

 pressed state of the water in the surface layer. 



On the experimental side the work of Freundlich and his 

 collaborators — [Kapillar-Chemie, 1909 ; Z. Phys. Cheni. 

 lix. p. 284 (1907); Ixvii. p. 538 (1909) ; Ixxiii. p. 399 (1910) ; 

 Ixxxiii. p. 97 (1913) ; Ixxxv. p. 398 (1913) ; xc. p. 681 (1915) ; 

 Koll.-Ch.em. Beihefte,\i. p. "297 (1914) : see also Schmidt, 

 Z. Phys. Chem. lxxiv. p. 689 (1910) ; lxxvii. p. 641 (1911) : 

 lxxviii. p. 667 (1912); Ixxxiii. p. 674 (1913); xci. p. 103 

 (1916). In the last-mentioned paper Schmidt and Hinteler 

 conclude that Freundlieh ; s equation represents their experi- 

 mental data better than that of Schmidt] — and of others, have 

 shown that adsorption-equilibria can be generally expressed 

 in terms of the well-known equation of Freundlich : 



xt)ll = a.C l P (2) 



Freundlich expressed the opinion that adsorption is mainly 

 due to a decrease in surface tension as suggested by Gibbs, 



Y2 



