1911.] 



The Properties of Colloidal Systems. 



97 



and action for large and small concentrations of substrate, are readily 

 explained by the slight effect of sugar on surface tension. 



A similar view to that advocated in the preceding pages as to the nature 

 of the combination between enzyme and substrate is described by 

 Ireundlich* as applying to the process of tanning leather. The amount of 

 tannin taken up is conditioned by an adsorption process in the first instance. 

 This is followed by a chemical reaction in the true sense, which takes place 

 slowly and results in the formation of insoluble bodies. In the case of 

 enzymes, the chemical reactions subsequent to adsorption are more rapid 

 than in the above process. 



The temperature coefficient of enzyme action as a whole is known to be a 

 high one, whereas that of adsorption is, so far as investigated up to the 

 present, a low one. In the case of Congo red and paper, I have foundf 

 that the rate at which equilibrium is attained is accelerated by rise of 

 temperature, but that the coefficient is only T36 for each 10 degrees 

 between 10° and 50° C, thus corresponding closely with that found by 

 BrunnerJ for a diffusion process, viz., 1*5. It seems then that the effect of 

 temperature on the rate of adsorption is merely on the rate of diffusion of 

 the bodies concerned. In the case of Congo red and paper it is of interest 

 to note that the actual amount adsorbed is diminished by rise of tem- 

 perature, although the rate at which the smaller amount is taken up is 

 increased. 



In the case of enzyme action the chemical change, being the slowest 

 member, is the factor governing the rate of the reaction as a whole, so that 

 the temperature coefficient is the high one of a chemical reaction. As far 

 as the effect of temperature on the actual amount of the adsorption of 

 enzyme and substrate is concerned, it will be seen that, if this effect is 

 similar to that when Congo red and paper are in question, the velocity of 

 the reaction as a whole, since it depends on the amount of enzyme adsorbed, 

 will be a very complex function of temperature. 



Summary. 



The existence of an " adsorption-compound " containing acid and base 

 uncombined chemically, and which can be isolated, is described, together 

 with the manner of its conversion into the true chemical compound or salt. 



It is shown that a similar kind of compound is formed between an enzyme 



* ' Kapillarchemie,' Leipzig, 1909, p. 532. 

 t 'Biochem. Journ.,' 1906, vol. 1, p. 187. 

 % ' Zeitsch. f. physik. Chem.,' 1904, vol. 47, p. 62. 

 VOL. LXXXIV. — B. H 



