26 Mr. W. Sutherland on Ionization in Solutions 



from the trend of his experiments. A similar explanation 

 applies to his experiments with globulin dissolved in alkali, 

 and to the earlier ones of Sackur on casemates of alkalies 

 (Zeits. f. pliys. Chem. xli.). There is therefore considerable 

 promise that the coefficients of (y^)* arising from the 

 viscosity J in X, when investigated by appropriate experi- 

 ments, will help to determine v and A for large ions by 

 (24), and thus supplement the methods which I have pro- 

 posed for determining large molecular masses by ionic 

 conductivities and diffusivities. 



7. Comparison of the Equation for the Coefficient of Diffusion 

 in Non-electrolytic Solutions with that for Specific 

 Molecular Conductivity in Electrolytic Solutions. 



In electrolytic solutions the connexion between ionic 

 velocities and diffusion is given at once by the theory of 

 .Nernst. In a diffusion column one ion moves faster than 

 another until the unequal distribution of ions produces an 

 electric force which causes both ions to diffuse with the same 

 steady velocity. Let ed'E/dx be the amount of this force on 

 one ion, then —edFt/dxis that on the other. Let the velocity 

 of diffusion of each ion be w at a place where the concentra- 

 tion of the solute is n gram-molecules per cm. 3 , and dnjdos is 

 its rate of variation per cm. along the stream of diffusion. 

 Then the resistance to the diffusion of each ion is F^ or 

 F 2 w, where F x and F 2 are coefficients connected with ionic 

 velocities in the following way : — The actual velocity of an 

 ion where the fall of potential is one volt per cm. is 

 obtained from Kohlrausch's ionic conductivity A 01 , which 

 as a part of X is expressed in ohm -1 cm. -1 by multiplying 

 by 0*00001035, which is the electrochemical equivalent of 

 hydrogen per coulomb. The velocity 0*00001035 A 0l is 

 acquired under an electric intensity of one volt per cm. 

 acting on an electron charge e. If e is measured in electro- 

 static units, the force acting on the ion is 10 8 ^/3 X 10 10 dynes. 

 Hence ^ = ^3x0-001035 A 01 and F 2 = <>/3 x 0-001035 A 02 . 

 For the motion of diffusion of the two ions we have the sum 

 of frictional resistance and electric force for all the ions of 

 one sort in unit volume, namely n/h, equal to the rate of 

 change of its osmotic pressure dpjdx = lftidnldx, where R is 

 the usual gas-constant. 



(F lW + edE/dx)ri/h = dp/da = (F 2 iv - edE/dx)n]h. (26) 



nw 2dpldx = dn 2A 01 A 02 3 x q.qq^ 



h .bi + Fg d;e e(A 01 -i-A Q2 ) 



