Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 4, pp. 686−688.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © I.B. Sladkov, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 4, pp. 681−683.
A Simple Method for Calculation of the Surface Tension
of Molecular Inorganic Liquids
I. B. Sladkov
St. Petersburg State Polytechnical University, St. Petersburg, Russia
e-mail: ofﬁ email@example.com
Received November 28, 2011
Abstract—A method was proposed for calculation of the temperature dependence of the surface tension using a
single experimental characteristic of a substance, its boiling point.
Methods for calculating the surface tension of molecu-
lar inorganic liquids are developed very poorly . Here,
a technique is proposed for calculating the temperature
dependence of the surface tension based on information
about a single easily accessible experimental character-
istic of a substance, its boiling point.
The surface tension σ, critical temperature T
critical volume V
can be combined into a fundamental
dimensionless group σV
), where R is univer-
sal gas constant. The temperature dependence of this
group can be expressed via a dimensionless parameter
. According to the law of corresponding
states, these two dimensionless parameters for similar
substances are interconnected as
) = K(1 – Т/Т
where K is a constant or a function of some properties
of the substance.
The experimental surface tension data suggest that,
for molecular inorganic liquids, the coefﬁ cient K varies
within a narrow range. This allows conversion of R and
K into a single constant K
, whereby the following equa-
tion can be obtained for calculation of the surface tension
σ = K
(1 – Т/Т
The critical temperature and critical volume rank
among the difﬁ cult to determine properties. In order that
Eq. (2) may be suitable for application in the case of
little-studied substances, the critical parameters should
be calculated using a minimum of easily accessible input
data. To this end, the necessary equations were taken from
[3, 4], speciﬁ cally, those for the critical temperature, K,
/(0.667 – 0.055f
and for the critical volume, cm
where f is the thermodynamic similarity criterion which
can be calculated by the formula
f = ln T
– 1.1ln P – 4, (5)
where P is the parachor.
Two easily accessible parameters, the boiling point
and the parachor, serve as the input data for Eqs. (3–5).
It should be noted that the parachor P, J
determined by calculation using the parachor increments
for different elements. For the technique and tabular
information to be used for parachor calculation, see .
As suggested by the experimental surface tension data,
the coefﬁ cient K
for molecular inorganic liquids varies
within narrow limits: The average K
value for 40 mo-
lecular inorganic liquids was estimated at 5.05. Therefore,
the surface tension, mJ m
, can be calculated by the