B.—CHEMISTRY. AT 
equation (1) is of the right order of magnitude if a value is assumed for 
the ionic radii of 10~-* cm. in accordance with X-ray data. But if the 
value of b is calculated from the ionic mobilities at infinite dilution, 
assuming Stokes’s law to hold, the observed and calculated coefficients are 
not in exact agreement, e.g. for potassium chloride solutions in water at 
25° they are 0°461 and 0°547 respectively. This difference is greater than 
the experimental error. 
Onsager, in 1926, pointed out that Debye and Hiickel in calculating 
the effect of the dissymmetry of the atmosphere around a moving ion, 
had neglected the Brownian movement of the ion and that a correcting 
factor of 2— /2 must be introduced on this account. His final equation 
has the same general form as Debye and Hiickel’s, and when numerical 
values are inserted for the universal constants, it becomes for a z-valent 
binary electrolyte 
0:986 x 108 pier 58:0 — 
Ap =A, — ore ¥3 z' No + TI a] Ve gered i) 
where 7 is the viscosity of the solvent. 
For various solvents at 25° this equation becomes for uni-univalent 
- electrolytes : 
: For water A, = A, — (0°228 A, + 59°8) Ve 
2 ,, methyl alcohol A, = A, — (0°957 A, + 1581) Ve 
;, ethyl alcohol A, =A, — (1°256 A, + 87°8) We 
For sodium chloride in each solvent these equations become: 
For water A, = 126°4 — (28°38 + 59°8) Ve 
| ,, methyl aleohol A,= 97-0 — (93, + 158°1) Vc 
» ethy! alcohol A,= 43:0 — (54 + 87°8) Ve 
These equations show that the dissymmetry term and the viscosity 
term (the first and second coefficients of \/c respectively) are of the same 
order. Their relative magnitude varies, however, with the properties of 
the solvent and with the ionic velocities of the ions present. 
The fundamental idea of the new theory, the existence of an ionic 
atmosphere with a finite time of formation and dispersion, has now been 
definitely established by the work of Wien on conductivities at high 
electromotive forces, and of Debye, Falkenhagen and Sack on conductivities 
at high frequencies. With a sufficiently great ionic velocity the atmosphere 
would not have time to form, while with a high enough frequency its 
issymmetry would vanish owing to the negligible displacement of the 
ion. In both cases the experimental results showed a satisfactory agree- 
ent with theory. 
The Debye-Hiickel-Onsager equation enables us to calculate the 
hange in equivalent conductivity with dilution for any electrolyte in any 
solvent provided that we know the ionic mobilities and valencies involved 
and certain physical constants of the solvent, but in comparing the 
