1070-4272/05/7808-1209 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 8, 2005, pp. 1209!1212. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 8, 2005,
Original Russian Text Copyright + 2005 by Lembrikov, Volkova, Konyakhina, Korneva, Pokidova.
AND INDUSTRIAL INORGANIC CHEMISTRY
A Study of Viscosity in the Extraction System Constituted by
Tributyl Phosphate and Phosphoric Acid
V. M. Lembrikov, V. V. Volkova, L. V. Konyakhina,
Z. N. Korneva, and O. V. Pokidova
Voskresenskii NIUiF (Voskresensk Research Institute of Fertilizers and Phosphoric Acid)
Open Joint-Stock Company, Voskresensk, Moscow oblast, Russia
Received May 13, 2005
Abstract-Data on the kinematic viscosity of phosphoric acid solutions in technical-grade tributyl phosphate
and in an industrial extract from a technological purification system based on tributyl phosphate, which
contain 0318% phosphoric acid in terms of P
,at10370oC are presented.
One of methods used to obtain pure phosphoric
acid is purification of extraction phosphoric acid
(EPA) with organic solvents. In Russia, Voskresenskii
NIUiF (Voskresensk Research Institute of Fertilizers
and Phosphoric Acid) Open Joint-Stock Company em-
ploys on the industrial scale a purification technique
in which tri-n-butyl phosphate (TBP) serves as an ex-
tracting agent .
When working with the installation used to purify
EPA, it is necessary to improve the quality of the acid
manufactured and to raise the output capacity of
the installation. This is achieved by selecting and de-
veloping a perfect equipment. Doing so requires that
the physicochemical parameters of the extraction sys-
tem, including the viscosity of an extract from the in-
dustrial technological system at various contents of
phosphoric acid in the extract, should be known.
This communication presents data on the kinematic
viscosity of phosphoric acid solutions in technical-
grade tributyl phosphate  and in an industrial ex-
tract from a technological purification system based
on technical-grade TBP, which contain 0318% phos-
phoric acid in terms of P
,at10370oC. The choice
of these temperature and concentration ranges was
governed by real conditions of the industrial pro-
cess for purification of extraction phosphoric acid.
The solutions were prepared by saturating technical-
grade TBP and the extracting agent from the industrial
The kinematic viscosity n of organic solutions
was measured with a capillary glass viscometer of
the VPZh type. The content of phosphoric acid was
determined potentiometrically . The temperature
of the experiments was maintained by thermostating
within +0.5oC. The resulting values of the kinematic
viscosity are listed in Table 1.
A graphical analysis and mathematical processing
of the data obtained demonstrated that the dependence
n = f (c, t) is logarithmic. It can be represented as
ln n = ac + b, (1)
where n is the kinematic viscosity (mm
); c, con-
tent of P
(wt %); and a, b, coefficients of the equa-
Table 2 lists values of the coefficients a and b,
as well as the approximation reliability R
curve. The data of Table 2 were used to plot the tem-
perature dependences of the coefficients a and b
(see figure) for technical-grade TBP and for the ex-
tracting agent from the industrial system. It is note-
worthy that the temperature dependences of the coef-
ficients are similar for both types of solutions.
The temperature dependence of the coefficient a
can be described by the equation
a=kT+ m, (2)
and that of the coefficient b,by
b=nexp ( pT ), (3)
where T is temperature (oC); k, m, coefficients in
Eq. (2); and n, p, coefficients in Eq. (3).