A New Look on the Representation of Electrical Conductivities in Mixed Solvents. The Universal Curves of Limiting Conductances of Electrolytes and the Modified and the Excess Walden Products
Alexander Apelblat*
Department of Chemical Engineering, Ben Gurion University of the Negev,
Beer Sheva, Israel
* Corresponding author: E-mail:
apelblat@bgu.ac.il
Abstract
Concepts of the modified and the excess Walden products are introduced and
discussed when applied together with the ordinary Walden product. The existence
of the universal curves of limiting conductances for electrolytes (or for ions)
in a given pair of solvents are further examined for a number of mixtures which
include ethanol, 2-propanol, 1,1,1,3,3,3- hexafluoro-2-propanol, N,N,-dimethylformamide
and 1,4-dioxane with acetone; methanol, 1,4-dioxane, carbon tetrachloride and
toluene with acetonitrile; water, methanol and γ-butyrolactane with
tetramethylene sulfone; methanol, acetonitrile, toluene, dimethoxymethane and
dimethoxyethane with propylene carbonate. Many electrolytes were involved in the
evaluation of the universal curves, but the majority are alkali metal halides
and tetraalkylammonium salts. These universal curves allow to estimate values of
limiting conductances of electrolytes and give an indication about the quality
of the performed conductivity measurements. The existence of universal curves of
limiting conductances indicates that the properties of electrolytes in pure
solvents are, to a great extent, preserved also in the mixture of solvents due
to the simple dilution effect. In some cases, for a limited concentration range,
it was observed that for a given electrolyte, the limiting conductances are
weakly dependent on the type of the second component in the mixture, e.g. in
waterrich– alcohol mixtures. A formal mathematical representation of the
universal curves (two-adjustable parameter equation) and the limiting
conductances (three-adjustable parameter equation) are introduced and for many
electrolytes in numerous mixed-solvent systems these parameters are reported.
Keywords: Electrical conductivity, mixed solvents, limiting conductances, various Walden products, universal curves of limiting conductances of electrolytes and ions, formal mathematical representation of limiting conductances in mixed- solvent systems.