ISSN 00360236, Russian Journal of Inorganic Chemistry, 2011, Vol. 56, No. 1, pp. 110–112. © Pleiades Publishing, Ltd., 2011. Original Russian Text © L.S. Grigor’eva, 2011, published in Zhurnal Neorganicheskoi Khimii, 2011, Vol. 56, No. 1, pp. 114–116.
PHYSICOCHEMICAL ANALYSIS OF INORGANIC SYSTEMS
The La(CCl3COO)3–NaCCl3COO–H2O System at 298 K L. S. Grigor’eva Moscow State University of Civil Engineering, Yaroslavskoe sh. 26, Moscow, 129337 Russia Received July 14, 2009
Abstract—The ternary lanthanum trichloroacetate–sodium trichloroacetate–water system was studied by the isothermal solubility method at 298 K. The compositions of solid phases were established by the Schkreinemak ers’ wet residue method. The liquid refractive indexes, specific volumes, and viscosities were determined. The system was found to be eutonic. DOI: 10.1134/S0036023611010104
The mutual solubility of lanthanum and sodium trichloroacetates was studied by the isothermal solu bility method at 298 K. Lanthanum trichloroacetate was synthesized as described in [1] without heating a solution to avoid hydrolysis to carbonates. Lanthanum trichloroacetate hexahydrate was used. Its composition was determined by analysis for lantha num via the complexometric titration with Xylenol Orange [2], organoelement analysis for chlorine via the combustion with metallic sodium in a microbomb and further titration of the chloride ion [3], and anal ysis for sodium ions with use of a flame photometer
[4]. The number of water molecules was found by dif ference and derived from differential thermal analysis. The system attained equilibrium after 7 days of continuous stirring with a glass pin, thereafter equili brated phases were separated and analyzed. Solubility data of the system are listed in Table 1, and its solubility diagram is shown in Fig. 1. The Schkreine makers’ rays in the solubility diagram indicate the crys tallization of the initial components in the system, which was found to be eutonic. The solubility isotherm has two branches. The longer branch corresponds to
Table 1. Solubility in the La(CCl3COO)3–NaCCl3COO–H2O system Liquid phase
Solid residues
Point no.
wt % La(CCl3COO)3
NaCCl3COO
Crystallizing phase
La(CCl3COO)3
NaCCl3COO
1 2 3 4 5 6 7 8 9 10
53.60 52.12 50.09 42.52 37.56 36.57 29.64 24.90 21.60 13.80
0 2.07 3.82 9.91 12.60 13.26 23.49 29.38 33.79 46.72
85.26 67.13 69.25 71.15 68.54 69.54 66.49 71.82 71.12 40.07
0 1.15 2.04 2.58 4.67 5.01 7.11 6.95 8.37 48.29
11 12 13 14 15 16
12.99 13.67 13.18 8.70 5.48 0
46.98 46.78 47.40 46.63 48.63 54.60
30.07 18.08 14.34 1.28 0.15 0
54.17 64.72 71.28 87.02 93.07 95.37
110
La(CCl3COO)3 · 6H2O The same '' '' '' '' '' '' '' Mixture La(CCl3COO)3 · 6H2O + NaCCl3COO · 0.5H2O The same NaCCl3COO · 0.5H2O The same ''
THE La(CCL3COO)3–NaCCL3COO–H2O SYSTEM
111
η, cP 10
La(CCl3COO)3, wt % 100
80
5
60
0 V × 10–3, m3/kg 0.7
40
0.6 20 nD 1.44 0
20
40
60
80 100 NaCCl3COO, wt %
1.42 0
20
40
60 80 100 NaCCl3COO, mol %
Fig. 1. Solubility diagram of the La(CCl3COO)3– NaCCl3COO–H2Osystem.
Fig. 2. Liquid property isotherms of the La(CCl3COO)3– NaCCl3COO–H2O system.
the crystallization of lanthanum trichloroacetate, and the shorter branch corresponds to the crystallization of sodium trichloroacetate. The eutonic point has the follow ing composition, wt %: La(СCl3COO)3–13.41 ± 0.62; NaСCl3COO–46.97 ± 0.49; H2O–39.62 ± 0.44. The sol ubility gap is shifted towards sodium, whose cation has the smaller size. This system does not form solid solu tions because of a considerable difference between the radii of the cations, their electronic structure, and lat tice types. Solid phases were identified by the methods of X ray phase analysis and crystal optics. Refractive indexes, specific volumes, and viscosi ties were determined for the liquid phase. The prop erty isotherms of the saturated solutions have a break point corresponding to the composition of the eutonic solution (Fig. 2). The solubility products (SPs) of the solid phases of the system were calculated from the activity coeffi cients γ± in the respective binary systems. The sodium trichloroacetate activity coefficient is known. The La(СCl3COO)3–H2O binary system was studied by the isopiestic method to determine the lanthanum trichloroacetate activity coefficient. The test and standard solutions were poured into stainless steel weighing bottles and placed into copper alloy cabinets used as vacuum desiccators.
The standard solutions used were the solutions rec ommended in [5]. Desiccators were placed into a tem peraturecontrolled cabinet. Equilibrium was attained during 40–60 days. The weighing bottles were weighed after the exper iments were over. The isopiestic concentrations were calculated by the difference between the weights of solutions before and after experiments. The water activity аw was determined using the calibration curve plotted by tabulated data on the water activity in stan dard sodium chloride solutions. The osmotic coefficients of La(СCl3COO)3 solu tions were calculated by the equation
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
ln a w = ν mM ϕ 1000, where ν is the number of ions, М is the water molar weight, and m is the molality of a solution. The activity coefficients were calculated as follows:
ln γ ±s = −s I (1 + A I ) + BI + CI 2. The parameters А = 1.9817, В = –6.5410 × 10–2, and С = 3.28 × 10–3 were derived from the isopiestic studies. The activity coefficients of lanthanum trichloroac etate solutions are given in Table 2. The water activity and the SPs of solid phases (Table 3) were calculated using the experimental data Vol. 56
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GRIGOR’EVA
Table 2. Results of isopiestic studies Point no.
mNaCl
ϕNaCl
m La ( CCl3 COO )
1 2 3 4 5 6
0.384 0.674 1.115 1.411 1.573 2.335
0.920 0.924 0.940 0.953 0.961 1.003
0.249 0.462 0.793 1.051 1.119 1.553
3
ϕ La ( CCl3 COO )
3
0.709 0.676 0.660 0.639 0.675 0.754
γ La ( CCl3 COO )
3
0.238 0.190 0.154 0.141 0.139 0.137
Table 3. Solubility products of the salts in the La(CCl3COO)3–NaCCl3COO–H2O system Molality Point no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
La(CCl3COO)3
NaCCl3COO
0 0.19 0.31 0.53 0.52 0.52 0.56 0.79 0.89 1.02 1.14 1.20 1.41 1.78 1.82 1.85
6.49 5.72 5.64 6.40 6.29 6.34 6.39 4.31 4.31 3.67 2.79 1.27 1.37 1.03 0.58 0
on the salt reciprocal solubilities in the system. A higher saltingout degree of lanthanum trichloroace tate hexahydrate is explained by the fact that it has a lower SP (logSP = –0.88 ± 0.05) in comparison with sodium trichloroacetate (logSP = 2.43 ± 0.16). REFERENCES 1. G. P. Tilley and I. E. Roberts, Inorg. Chem. 2 (4), 745 (1963).
– log a w
Crystallizing phase
0.179 0.158 0.163 0.209 0.204 0.205 0.210 0.140 0.123 0.101 0.061 0.067 0.067 0.072 0.065 0.060
NaCCl3COO · 0.5H2O The same '' '' '' '' '' La(CCl3COO)3 · 6H2O The same '' '' '' '' '' '' ''
log SP 2.38 2.19 2.22 2.57 2.53 2.55 2.58 –0.678 –0.746 –0.865 –1.286 –1.159 –1.043 –0.819 –0.900 –0.965
2. G. Schwarzenbach and H. Flaschka, Die Complexome trische Titration (Stuttgart, 1976; Khimiya, Moscow, 1970). 3. V. A. Klimova, The Basic Methods of Organic Microanalysis (Khimiya, Moscow, 1975) [in Russian]. 4. N. S. Poluektov, Flame Photometry Analyses (Khimiya, Moscow, 1967) [in Russian]. 5. R. Robinson and R. Stokes, Electrolyte Solutions (But terworths, London, 1959; Inostrannaya Literatura, Moscow, 1963).
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