536 



Dr. E. F. Armstrong and Mr. E. J. Caldwell. [Apr. 5, 



In a lengthy paper published 10 years later,* in which the results 

 obtained in the meantime by other workers were discussed, he made an 

 important addition to his theory by showing that the increase in K 

 with concentration is in exact correspondence with the increase of 

 osmotic pressure of the solution. He vaguely referred to the influence 

 of neutral salts as being of the same order as that exercised by an 

 increase in the concentration of the hydrolyte. 



Exception was taken by Lippmann,f in 1900, to the explanation put 

 forward by Arrhenius, on the ground that it was impossible, in the 

 case of sugar, to understand how any change could take place which 

 would render one part more active than another. Lippmann also 

 sharply criticised the attempt made by EulerJ to interpret the hydro- 

 lysis of sugar from a purely ionic standpoint. Euler's§ answer to 

 these criticisms in no way served to remove the difficulties raised by 

 Lippmann, || but rather the contrary. 



There can be no doubt that in discussing hydrolytic changes 

 generally the conception of an active mass cannot be dispensed with ; 

 it remains only to give precision to the conception by defining the 

 precise character of such a mass. On the assumption made in this 

 and the two preceding papers, the active mass postulated by Arrhenius 

 is neither more nor less than the system composed of the hydrolyte, 

 the enzyme or acid and a certain limited number of water molecules. 

 Although the formation of such a system is probably attended with 

 a slight evolution of heat, its immediate breakdown should involve 

 the absorption of heat and this change should be reversible. Etherifi- 

 cation phenomena generally and the change of isodynamic systems 

 into one another all satisfy these conditions. There can be little doubt 

 that the breakdown of complex systems, such as are here contemplated, 

 would be most materially influenced by changes in temperature, and 

 that the rate of change would advance rapidly as temperature rose. 

 The tendency to form such systems would obviously diminish somewhat 

 as temperature rose. 



In conclusion, it is desirable to lay emphasis on the differences 

 noticeable in the behaviour of enzymes and acids respectively as 

 hydrolytic agents : it appears not improbable that this difference is 

 due mainly, if not wholly, (1) to the superior affinity of the enzymes 

 for the carbohydrates, (2) to the very different behaviour of the two 

 classes of hydrolysts towards water — which is a consequence of the 

 colloid nature of the one and the crystalloid nature of the other. It 

 appears possible to explain such differences as are apparent in their 



* ' Zeit. Phys. Chem.,' 1899, vol. 28, p. 317. 

 f ' Ber.,' vol. 33, p. 3560. 



X ' Ber.,' vol. 33, p. 3202, and ' Zeit. Phys. Chem.,' vol. 36, p. 641. 

 § ' Ber., 5 vol. 34, p. 1568. 

 |J ' Ber.,' vol. 34, p. 3747. 



