FLUIDITY AND DIFFUSION

195

In ordinary electrolytic solutions, the dissociation is incom-
plete, hence it is necessary to introduce into our formula the
dissociation factor a in order that we may always be dealing
with an equivalent number of ions, thus

= •—- = const.

Ac»

(67)

where <pv and Av are the fluidity and conductivity at the volume
v. This formula is of use in obtaining the percentage of dissocia-
tion by the conductivity method, as indicated by Sutherland
(1902) Bousfield (1905) and Pissarevski and Lempke (1905).
Working with mixtures of alcohol and water, Doroshevskii and
Rozhdestvenskii (1909) found that the ratio D<p/A was a constant
over a considerable range of concentrations of alcohol, D being
the dielectric constant of the mixture. There is of course a rough
proportionality between the dielectric constant and the dis-
sociating power of the solvent.

Hartley, Thomas, and Applebey (1908) have applied the
Eq. (67) to solutions of lithium nitrate in mixtures of nicotine and
water. These mixtures resemble ethyl alcohol and water in
exhibiting a pronounced minimum in fluidity. The coefficient
of ionization, calculated by formula (67), shows a maximum.
The molecular conductivities of solutions at infinite dilution of
the salt show a minimum, closely resembling the fluidity curve,
whereas the molecular conductivities of an eighth normal solution
show a point of inflection, due to the small ionization in the pure
solvent.

Heber Green (1908) has started considerable discussion
by the discovery that in water-sucrose mixtures, the conductivity
varies, not directly as the fluidity, but

A00 = ^^ (68)

where m = 0.70 for lithium chloride and potassium chloride and
0.55 for hydrochloric acid. In the case of lithium chloride no
single value for m can be found which will give entirely satis-
factory results. As a matter of fact, Washburn (1911) has found
that for the first six sucrose concentrations, a value of m of 0.94
gives better concordance than Green's 0.70. Johnston (1909)
has determined the values of m for a number of other solvents
using the data of Dutoit and Duperthius (1908) for sodium

m