1911.] 



The Properties of Colloidal Systems. 



35 



The velocity of production of sulphuric acid in the method of platinum 

 catalysis has been shown by Bodenstein and Fink* to be controlled by the 

 adsorption of SO3 on the surface of the platinum. 



Denhamf has made a detailed investigation of the catalytic influence of 

 platinum on the reduction of titanic sulphate by hydrogen, and is led to the 

 conclusion that the chief part in the reaction is played by surface conden- 

 sation, in the sense of Willard Gibbs. 



The work of Lewis already referred to demands further notice in the present 

 connection. The amount of aniline condensed on the surface of mercury 

 •was found to be in agreement with that given by the formula of Gibbs 

 deduced from thermodynamic considerations. When, however, colloids or 

 electrolytically dissociated salts were concerned, the Gibbs formula ceased to 

 apply. It would seem that surface energy of a kind other than that dealt 

 with by Gibbs plays a part in these cases. In all probability the origin of 

 this form of surface energy is to be looked for in electrical forces. 



The toxic action of salts on living protoplasm,^ and the action of mercuric 

 chloride as an antiseptic,§ have been found to be proportional to the amount 

 deposited on the- surfaces of the organisms or of their constituent colloids ; 

 in other words, the exponential equation is found to apply. It is possible 

 that chemical reactions in the strict sense of the word follow adsorption. 



It has been suggested by Wo. Ostwald || that the taking up of oxygen by 

 haemoglobin is conditioned by a surface adsorption process, since the curve of 

 percentage saturation in relation to oxygen tension is best expressed by an 

 exponential formula. The work of Barcroft and Hill IF has shown that heat 

 in definite proportion is given out when haemoglobin combines with oxygen, 

 so that it appears that chemical combination follows adsorption as a further 

 stage. At the same time it should not be forgotten that the condensation of 

 a gas is associated with the liberation of heat and in direct ratio to the amount 

 condensed. 



Findlay and Creighton** have shown that the solubility of certain gases in 

 water is affected considerably by the presence of surfaces therein, and are 

 inclined to attribute the phenomena to adsorption. 



* ' Zeit. f. physik. Chem.,' 1907, vol. 60, p. 43. 



t ' Zeit. f. physik. Chem.,' 1910, vol. 72, pp. 641—695. 



% Wo. Ostwald and A. Dernoschek, ' Kolloid-Zeit.,' 1910, vol. 6, p. 297. 



§ Hugo Morawitz, ' Koll. chem. Beihefte,' 1910, vol. 1, pp. 317—323. 



|| ' Kolloid-Zeit.,' 1908, vol. 2, pp. 264 and 294. 

 IT ' Journ. of Physiol.,' 1909, vol. 39, p. 411. 

 ** 'Trans. Chem. Soc.,' 1910, vol. 97, p. 560. 



