110 Conductivities and Viscosities in Pure and in Mixed Solvents. 



Spohr 1 finds that cane sugar is inverted 5 times as rapidly at 55 as 

 at 25. Various attempts have been made to explain the effect of rise 

 in temperature on the velocity of chemical reactions. A decrease in 

 the viscosity of the medium with rise in temperature, allowing the 

 ions to move more rapidly, a decrease in the mass of the ion with rise 

 in temperature, and the increased kinetic energy of the molecules and 

 ions, have been cited as the causes of the great increase, with rise in 

 temperature, in reaction velocity. None of these theories seems suffi- 

 cient to account for such an increase in the velocity of reactions as was 

 noticed by Berthelot and others. 



From the solvate theory of solution we see that ions and molecules 

 attract to them molecules of the solvent. We should expect these ions 

 to react more slowly, especially if the solvate were very complex, since 

 the solvate would act as a protective covering around the ions and 

 diminish the velocity with which they would react with one another. 

 But suppose the temperature is raised; the solvate would become less 

 and less complex, until finally the ions would not have any appreciable pro- 

 tective covering. In such a case, where the ions are in direct contact, 

 we should expect the velocity of the reaction to be greatly increased. 



We therefore offer this tentative suggestion as one of the most 

 important causes of the increase in the velocity of chemical reactions 

 with rise in temperature. 



In conclusion, we can say that the chemical differences between free 

 and combined water, brought out in the study of this problem, are 

 strictly analogous to the physical differences between free and combined 

 water, as shown by their power to absorb light, which led us to inves- 

 tigate this problem. 



SUMMARY. 



The following conclusions have either been confirmed or brought 

 out in this investigation: 



(1) The reaction involving the decomposition of an ester proceeds 

 slowly at ordinary temperatures, and therefore can be readily and 

 accurately studied. 



(2) The hydrolysis of the chlorides and nitrates, etc., of calcium, mag- 

 nesium, strontium, and barium employed in the study of this problem 

 is so small that it can not account for the differences observed. 



(3) Salts with water of crystallization increase the velocity of the 

 saponification of an ester to a greater extent than salts with no water 

 of crystallization. 



(4) On dilution, the effect with salts having water of crystallization 

 decreases more rapidly than with salts without crystal water. 



J Zeit. phys. Chem., 2, 195 (1888). 



