Handbook of Solvents - George Wypych - ChemTech - Ventech!

9.3 Physical properties of mixed solvents 515
of permittivity, α ε , of the equivolume mixture of two chemically non-interacting associated
solvents is carried out using the equation identical in its form to [9.26].
where
( )
Δα = 05 . α − α + α −Δα
[9.27]
1 2 2
ε, V= 05 . ε ε ε ε,
V=
05 .
( )
Δα = 0. 043 α −α/
α
[9.28]
1 2
ε, V= 05 . ε ε ε,
V=
05 .
9.3.1.2 Viscosity
There are a great number of equations available in literature intended to describe viscosity
of mixtures of chemically non-interacting components. All these equations, regardless of
whether they have been derived theoretically or established empirically, are divided into
two basic groups. The first group includes equations relating mixture viscosity,η, to viscosity
of initial components, ηi, and their content in mixture, c, (c in this case is an arbitrary
method of concentration expression):
( , , ; , , )
η f η η �η c c � c
[9.29]
= 1 2 i 1 2 i−1
The equations of the second group include various constants k 1,k 2, etc., found from
experiment or calculated theoretically
( , , ; , , ; , , )
η f η η �η c c �c k k � [9.30]
= 1 2 i 1 2 i−1
1 2
The accuracy of calculation of solvents mixture viscosity from [9.30] type of equations
is not higher than from equations of [9.29] type. We, thus, limit discussion to equations
[9.29].
The comparison of equations of type [9.29] for binary liquid systems 3 has shown that,
in most cases, viscosity of systems with chemically non-interacting components is described
by the exponential function of molar-fractional composition
i
xi
=∏ i
η η
1
or for binary solvent:
η= η η
x 1−x
1 2
[9.31]
[9.31a]
where:
xi molar fractions of components of the binary system
Empirical expressions for calculation of viscosity of the system of a given type, which
permit more precise calculations, are given in monograph. 3
From [9.31], it follows that the relative temperature coefficient of viscosity
βη = ∂η/ η∂T= ∂ln η/ ∂Tfor
mixtures of chemically non-interacting liquids is described by
equation:
( )
β = xβ + 1 −x
β
[9.32]
η η1 η2