Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 2, pp. 222−227.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
I.M. Gusev, M.Yu. Skripkin, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 2, pp. 229−234.
OF SYSTEMS AND PROCESSES
Comparative Analysis of the Solubility in the Systems
O at 25°C
I. M. Gusev and M. Yu. Skripkin
St. Petersburg State University, St. Petersburg, Russia
Received June 25, 2008
Abstract—The solubility in the CuBr
O (R = Me, Et, n-Bu) ternary systems at 25°C was determined
by the isothermal saturation method. Comparative analysis of the phase equilibria diagrams was done. The results
obtained were interpreted in terms of the competition of two processes, association of tetraalkylammonium salts
and copper(II) complex formation in water-salt systems.
Reciprocal interaction of components in heterogeneous
water-salt systems and its manifestation in the solution-
solid phase equilibria is a central problem in modern
solution chemistry. Revealing for new general trends in
the variation of the solubility of substances with their
chemical nature, ﬁ nding new routes of liquid-phase
synthesis of compounds with predictabled properties,
and development of methods for the enrichment of
polymetallic concentrates make urgent the study in this
In this work we present results obtained in studying the
solution−solid phase equilibria in the CuBr
(R = Me, Et, n-Bu) ternary systems.
A systematic study of properties of the systems
containing tetraalkylammonium and copper salts is
topical. Tetra-alkylammonium salts are used in extraction
systems [1, 2] and as phase-transfer catalysts .
Application of the above substances in the given areas
arises from their good solubility in water and, owing to
the presence of lyophilic alkyl radicals, also in nonpolar
organic solvents. Therefore, depending on the conditions,
a tetraalkylammonium cation with a counter ion can
leave the water and pass into the organic phase and vice
versa. Copper(II) compounds, pure or in combination
with the compounds of copper(I) and alkali metal salts,
are effective catalytic systems for a large number of
organic reactions [4−8]. It seems promising to combine
a copper(II) cation and tetraalkylammonium ions in the
same system or substance.
The solubility was studied by the method of isothermal
saturation. Sets of solutions were prepared by successive
dilution of the initial solutions. As initial solutions were
used saturated solutions of CuBr
Br. To them,
a third component was added at a step of 0.2−1 mol kg
O. The solutions were placed into an air thermostat and
kept there at 25.0 ± 0.1°C for 1 day at constant agitation
(magnetic stirrer). Since the solutions formed in the
O system with a tetraalkylammonium
bromide concentration more than 15 mol kg
viscous, the keeping time was 3 days.
The concentrations of copper(II) and bromide ions were
determined by titration (with Trilon B and mercury titrants,
respectively). The concentration of tetraalkylammonium
bromide was calculated as difference. The relative error
of the analysis did not exceed 0.5%. The composition
of solid phase was determined by the Skreinemakers’
method. Experimental data on the solubility isotherms
are given in Tables 1−3 and plotted in Fig. 1.
Noteworthy that the solubility in the binary systems
strongly increases in the order NMe
Br < NЕt
Br (6.24 mol kg
O for tetraalkylammonium
bromide, 16.79 mol kg
O for tetraethylammonium,
and 20.40 mol kg
O for tetrabutylammonium).
Precursors of the solid phase in the systems under study
are electroneutral particles, contact ion pairs (NR
and the condition, at which a solid phase is formed, is
a certain threshold value of their concentration in the
solution . In its turn, the formation of ion pairs is