towards a Dynamical Theory of Solutions. 65 



that has its origin in the mutual electric energy of neighbour 

 ions. The other viscosity derived from the energy of ion 

 and molecules of solvent is implicitly taken into account in 

 the values of X which it helps to determine. In all catalytic 

 actions these electric fields must play a prime part. Take 

 such an instance as the optimum strength of solution of HC1 

 for the digestion of protein by pepsin. It looks very much 

 as if this strength determined the best adjustment of electric 

 fields between the ions of HC1 to promote the catalytic 

 action of the enzyme on the protein. In a similar way 

 Emil Fischer's likening of the relation between enzyme and 

 substrate to that between key and lock may perhaps be made 

 more definite by replacing both key and lock by electric 

 fields adjustable to one another in the manner of key and 

 lock. 



In the present section I have tried to bring the theoretical 

 conception of the mode of action of weak electrolytes into 

 line with the theory of strong electrolytes given in previous 

 papers. 



6. Summary and General Conclusions. 



Section 4 contains a summary of the part of the paper 

 previous to it. In section 5 it is shown how Ostwald's 

 dilution law for the molecular conductivity of weak electro- 

 lytes, such as the fatty acids, expresses the equilibrium 

 between the double molecules and the ions of these acids in 



water. A formula (\r]y—ap 2 p is developed for molecular 

 conductivity in strong solutions (20 to 90 per cent.) and is 

 shown to merge continuously into the formula of Ostwald 

 with a short region of transition near p 1 = , 15. This region 

 is not investigated, but it is argued from the continuity and 

 from the close equality of the values of a for different acids 

 that single molecules of the acids do not exist in aqueous 

 solutions of any strength, only double molecules and ions 

 being present. Thus the study of conductivity confirms the 

 basis of the rest of the present investigation, namely the 

 assumption that when alcohols and fatty acids are mixed 

 with water their molecules are double those represented by 

 the usual chemical formulas. In the case of the acids the 

 ions are too few to affect the other physical properties of 

 the mixtures to an extent worth investigating without 

 specially delicate experiments. The outcome of the whole 

 inquiry is that the changes in most of the physical properties 

 occurring when alcohol or fatty acid is mingled with water 

 happen in the water through changes of its trihydrol into 

 Phil. Mag. S. 6. Vol. 22. No. 127. July 1911. F 



