- Email: [email protected]
Thermodynamic study of the NaCl Na2SO4 Na2Cr2O7 H2O system at the temperature 298.15 K
Calphad, Vol. 25, No. 1, pp. 11-17, 2001 0 2001 Elsevier Science Ltd All rights reserved 0364-5916/01/$ - see front matter
Pergamon
PII: SO364-5916(01)00025-6
THERMODYNAMIC STUDY OF THE NaCl - NasSOd- Nad&O, - Hz0 SYSTEM AT THE TEMPERATURE 298.15 K Christomir Christov Department of Chemistry, University of California, San Diego, La Jolla, CA 92093-0340, USA ABSTRACT The Pitzer ion-interaction model has been used for thermodynamic simulation of the ternary NaClNa2Cr207-HZ0 and NazS04-NazCrz07-Hz0, and the quatemary NaCl-Na#04-Na&07-Hz0 systems at T=298.15 K. The necessary thermodynamic functions (binary and ternary parameters of inter-ionic interaction and thermodynamic solubility products) have been calculated and the theoretical solubility isotherms have been plotted. Good agreement between experimentally determined and calculated solubilities has been found. 1. Introduction The study of the quatemary NaCl-Na#04-Na&rz07-Hz0 system and the corresponding ternary subsystems is of great practical importance above all in association with the choice of optimum preparation conditions of sodium bichromate. For that reason, systems with the participation of Na&O7 have been the subject of many experimental investigations over a wide temperature range (l-6). Robertson (l), Gerassimow (2) and Jukow and Shutova (3) have studied the system NaCl-Na$Zrz07-Hz0 at temperatures T=298.15 K and 293.15 K and established a solubility isotherm consisting of a very narrow crystallization field of sodium bichromate dihydrate and a broad field of sodium chloride. According to data available in the literature (3-5), the solubility isotherm of the NazS04-Na&07-Hz0 system contains crystallization fields of NazCr207.2Hz0, Na#Od. 10HZOand Na2S04 within the range from T=293.15 K to T=298.15 K. Jukov and Shutova (3) have established the composition of the invariant point (NaCl+Na,SO,+Na&O,.2HzO) in the quatemary system NaCl-Na$Oa-Na&YrzO,-Hz0 at T=293.15 K. In the literature we have found no data on the thermodynamic simulation of ternary and multicomponent solutions with the participation of sodium bichromate. In a previous study (7) the Pitzer ion-interaction model was used for simulation of the ternary KCl-KzCrz07-HzO,KBr-K2Cr207-H20 and KzS04-K2Crz07-HzO, and the quatemary KC1-KzS04-K&Z0,-HZ0 systems at T=298.15 K. It was shown that the Pitzer equations can be used to obtain a sufficiently exact description of the properties of solutions with the participation of bichromate salts. The purpose of the present paper is a thermodynamic simulation, on the basis of Pitzer model, of the ternary systems NaCl-NazCrz07-Hz0 and Na#04-Na&07-HzO, and the quatemary system NaC1-Na2S04-NazCrz07-H20at T=298.15 K. 2. Solubility calculations In agreement with the aim formulated above, the Pitzer ion-interaction model (8-l 1) was used, which allows the determination of the activity coefficients in saturated and unsaturated electrolyte Received on 27 August 1999 11
12
C. CHRISTOV
solutions with an accuracy of 2 to 6 per cent (12). The theoretical basis of an ion-interaction model has been presented in previous papers (7, 13). The basic Pitzer model has been successfully used for the solution of many theoretical and practical problems. It has been proved that the model can be used for sufficiently exact descriptions of the properties of saturated and unsaturated binary (68), ternary (7, 12-15) and multicomponent (7, 16-18) electrolyte solutions. In this paper the systems were investigated using an approach which had already been applied to other systems from which phases with a constant stoichiometric composition (simple and double salts) crystallize (7, 13-17). This approach consists of: determination of Pitzer binary parameters (p(O), p(l), p(2), C$; determination of the Pitzer ternary parameters (@MN and MM); calculation of the solubility isotherms of the three-component systems; calculation of the solubility isotherm of the quatemary system. 2.1. Binary Systems The values of the binary parameters of the systems NaCl-Hz0 and NazS04-HzO at T=298.15 K have been determined by many authors (8, 16, 18). Since the calculation of the compositions of saturated ternary solutions is the main purpose of the simulation, the applicability of the binary parameters to high concentrations of the binary solutions up to saturation at the lowest value of the standard deviation (6) is a very important criterion for the choice of the binary parameters. The p(O), p(l), p(2), and C$ values used here are given in Table 1. They are valid up to saturation or almost to saturation of the binary solutions. Their applicability has been proved by simulation of the multicomponent seawater system (18). TABLE 1 Pitzer Binary Parameters at T=298.15 K where CFis the Standard Deviation of the Osmotic Coefficients System
m_
p’0’
$1)
p(2)
NaCl-H20”
0.07650
0.26640
-
0.00127
6.0000
0.00100
Na#04-H20”
0.01958
1.11300
-
0.00497
4.0000
0.00300
NazCr207-HzOb
0.13513
-8.94435
-0.00495
3.8792
0.00268
2.03150
moL kg-’
cs
aReference 18. bReference 6. Calculated with al=2 and (XQ =l. In a previous study the isopiestic method has been used to determine the osmotic coefficients of binary Na&O,-Hz0 solutions at T=298.15 K (6). Optimum values of the binary parameters have been calculated (Table 1). On the basis of the data concerning p(O), B(l) p(2) and CQ and the concentration (m’) of the saturated binary solutions, the logarithm of the thermodynamic solubility product InK”,, for the solid phases (Table 2) was calculated. The small differences between the lnK”sp
THE NaCI-Na+O~-Na2Cr207-H20
SYSTEM
13
Jalues for NaCl and Na2S04. 10HzO obtained in this paper and those presented in refs. (16, 18) are nainly due to the different
ms values used for the calculation.
On the basis of lnK'&values and
Ising initial thermodynamic data of aqueous species (19) the standard molar Gibbs energy of formation AC”,,, of simple salts crystallizing from saturated binary solutions (Table 2) was :alculated. The A@,,, values obtained are compared with those proposed by Wagman et al. (19). The differences ‘are within error limits of an ion-interaction model. TABLE 2
Calculated Values of the Logarithm of the Thermodynamic Solubility Product Kospand of the Gibbs Energy of Formation AIG”, of Solid Phases Crystallizing from Saturated Binary Solutions
“Calculated using thermodynamic
data of Wagman et al. (19).
TABLE 3
Pitzer Ternary Parameters at T = 298.15 K System
0MN
Y’MNX
NaCl-Na2S04-HzOa
0.02
0.0014
NaCl-NazCrz07-HzO
0.10
-0.0100
NazS04-NazCrz07-H20
0.09
-0.0100
aReference 18.
14
C. CHRISTOV
2.2. Ternary Systems The ternary parameters were obtained from the experimental data on the solubilities in the ternary systems (7, 13-16). The thermodynamic model was built on the basis of Robertson’s results (1) for the system NaCl-NazCrz07-HzO, and of Rakovskii and Nikitina’s (4) and Borovskih and Vilnjanskii’s (5) for the system Na#04-Na&07-H20. The choice of the parameters is based on the minimum deviation of the logarithm of the solubility product lnK& for the whole crystallization curve of the component, from its value for the saturated binary solution. In addition, the InKi+, value for Na#Od crystallizing in the Na#04-Na2Crz07-Hz0 system had to be constant along the whole crystallization and ~Nx
the unsymmetrical
branch of sodium sulphate. In our calculations
of @IN
mixing terms Et3 and E8’, were included according to reference
(9). The lnK:p value found in this study for Na2S04 is equal to that of Harvie and Weare (18). Simulating the systems KCl-K$&O,-Hz0 and K$04-K&rZ07-H20 (7) the following parameter values: 8ci,cr207=0.10 and 8 so4,,crzo7=0.09 are proposed. Since the parameters 8c1,,crZo7and take into account only the ionic interactions of the type Cl-Crz07 and S04-Cr207, 8S04,CrZ07 respectively in ternary solutions, their values have to be constant for the potassium and sodium solutions. The WM( values only have been varied. The calculated ternary parameters are presented in Table 3. The solubility isotherms of the ternary systems at T=298.15 K are calculated on the basis of the thermodynamic properties obtained. A method described in previous works (7, 13- 16) has been used. The calculated solubility isotherms are presented in Figs. 1 and 2. Table 4 summarizes the predicted and experimentally found compositions of eutonic solutions. The calculated results agree very well with the experimental data. 2.3. Quaternary System The calculated thermodynamic functions (binary and ternary parameters of interionic interaction and thermodynamic solubility products) are used for the simulation of the system NaCl-Na$OdNazCrz07-H20 in the range of higher CrZ07’- concentrations. The values of Pitzer ternary parameters for the N&l-Na#04-H,0 system were taken from the literature (18) (Table 3). The composition of the invariant point (NaC1+NazS04+Na2Crz07) was calculated as a point where the chemical potential of all three components is constant. Table 4 shows the composition of the calculated and the experimentally determined [Jukow and Shutova (3)] eutonics. The composition calculated at T=298.15 K has been compared with those obtained experimentally at T=293.15 K. The type of the solubility diagrams of the ternary subsystems at T=293.15 K and T=298.15 K is the same, i.e. the same solid phases crystallize in them (l-5). This fact has permitted the above comparison. The calculated results agree very well with the experimental data. 3. Conclusion The theoretical solubility isotherms of the systems NaCl-NazCrz07-Hz0, Na2S04-NazCrz07-Hz0 and NaCl-Na2S04-NazCr207-Hz0 at T=298.15 K have been plotted. The agreement with the experiment is very good. This permits conclusions concerning (i) the applicability of the thermodynamic approach used to obtain a sufficiently precise description of the properties of
THE NaCI-Na2S04-Na2Cr207-H20
-7----
-
WJ
I
/
‘-,
/
15
SYSTEM
NalCrz0,.2H,0
%rJhoLkg”)
FIG. 1 system at T = 298.15 K: -
Molality m’ solubilities in NaCl-Na&O,-H,O experimental data: l, from reference 1.
, calculated values;
i i I
1 o.ooL__-__L___L 0.00
0.50
\_
-L_
_L-~‘-_L 1
.oo
1.so
_..\”
j
2.00
FIG. 2 Molality m’ solubilities in Na,SO.,-Na,Cr,O,-Hz0 system at T = 298.15 K:--, experimental data: o, from reference 4, l, from reference 5.
calculated values;
16
C. CHRISTOV
binary, ternary and multicomponent solutions with the participation of sodium bichromate, (ii) the correctness of the thermodynamic functions calculated in this paper, and (iii) the correctness of the experimental data on the solubilities available in the literature.
TABLE 4
Experimental and Predicted Compositions of Invariant Points for the Quaternary System NaCl - Na$304 - NazCrzO, - Hz0 and for the Ternary Subsystems. Solid Phases
NaC1+Na2S04 0.69
6.87
0.57
7.19
0.80
6.66
0.83
6.67 0.11
7.07
0.12
7.12
0.05
6.92
0.06
7.06
0.82
2.63
0.83
2.70
0.90
2.68
Calculated
0.84
0.09
6.57
Experimentalb
0.79
0.05
6.62
NazCrz07.2Hz0+ NaCl
NazCrz07.2Hz0+ Na2S04
Na2S04. lOH*O+ Na$SO,+
NaC1+Na2S04+ Na$Zrz07.2H20 I
aExperimental data of Robertson (1) at T=298.15 K; bExperimental data of Jukow and Shutova (3) at T=293.15 K; “Experimental data of Gerassimow (2) at T=293.15 K; dExperimental data of Rakovskii and Nikitina (4) at T=298.15 K; eExperimental data of Borovskih and Vilnjanskii (5) at T=298.15 K.
Acknowledgements This investigation Technology.
was supported in part by the German Ministry of Education,
Research
and
THE NaCI-Na2S04-Na$r207-H20
17
SYSTEM
References 1.
J. Robertson, J. Sot. Chem. Zmf. 43,334 (1924).
2.
J. Gerassimow, Z. Anorg. Chem. 187,321 (1930).
3.
A. Jukow and V. Shutova, Trudy Uralskogo Nauchno-Technicheskogo Goshimizdat,
4.
1, 1959, pp. 29-35.
A. Rakovskii and E. Nikitina, Trudy Instituta Chistqh. Himich. Reaktivov, Gosud. NauchnoTechnich. Izdattelstvo,
5.
L. Borovskih, Proizvodstva
6.
Znstituta,
11, 193 1, pp. 5- 14.
J. Vilnjanskii, hromovqh Iftoristqh
Trudy
Konferenzii
po
Usovershenstvovaniy
Tehnologii
solei, Goshimizdat, 1959, pp. 46-54.
C. Christov, S. Velikova, K. Ivanova and STanev,
Coil. Czech. Chem. Commun. 64, 595
(1999). 7.
C. Christov, CALPHAD 22,449 (1998).
8.
K. Pitzer, J. Phys. Chem. 77,268 (1973).
9.
K. Pitzer, J. Solution Chem. 4, 249 (1975).
10.
K. Pitzer and G. Mayorga, J. Phys. Chem. 77,230O (1973).
11.
K. Pitzer and G. Mayorga, J. Solution Chem. 3,539 (1974).
12.
K. Pitzer and J. Kim, J. Am. Chem. Sot. 96,570l
13.
C. Christov, CALPHAD 20,501 (1996).
14.
C. Christov, J. Chem. Thermodynamics
26, 1071 (1994).
15.
C. Christov, J. Chem. Thermodynamics
3 I,71 (1999).
16.
C. Christov, J. Chem. Thermodynamics
32,285 (2000).
17.
C. Christov, S. Petrenko, C. Balarew and V. Valyashko, Monatsh. Chem. 125,137l
18.
C. Harvie and J. Weare, Geochim. Cosmochim. Acta 44,981 (1980).
19.
D. Wagman, W. Evans, V. Parker,
(1974).
R. Schumm, I. Halow, S. Bayler, K. Chumey
Nutall, J. Phys. Chem. Re$ Data 11 (1982) (Suppl.2).
(1994).
and R.
Pergamon
PII: SO364-5916(01)00025-6
THERMODYNAMIC STUDY OF THE NaCl - NasSOd- Nad&O, - Hz0 SYSTEM AT THE TEMPERATURE 298.15 K Christomir Christov Department of Chemistry, University of California, San Diego, La Jolla, CA 92093-0340, USA ABSTRACT The Pitzer ion-interaction model has been used for thermodynamic simulation of the ternary NaClNa2Cr207-HZ0 and NazS04-NazCrz07-Hz0, and the quatemary NaCl-Na#04-Na&07-Hz0 systems at T=298.15 K. The necessary thermodynamic functions (binary and ternary parameters of inter-ionic interaction and thermodynamic solubility products) have been calculated and the theoretical solubility isotherms have been plotted. Good agreement between experimentally determined and calculated solubilities has been found. 1. Introduction The study of the quatemary NaCl-Na#04-Na&rz07-Hz0 system and the corresponding ternary subsystems is of great practical importance above all in association with the choice of optimum preparation conditions of sodium bichromate. For that reason, systems with the participation of Na&O7 have been the subject of many experimental investigations over a wide temperature range (l-6). Robertson (l), Gerassimow (2) and Jukow and Shutova (3) have studied the system NaCl-Na$Zrz07-Hz0 at temperatures T=298.15 K and 293.15 K and established a solubility isotherm consisting of a very narrow crystallization field of sodium bichromate dihydrate and a broad field of sodium chloride. According to data available in the literature (3-5), the solubility isotherm of the NazS04-Na&07-Hz0 system contains crystallization fields of NazCr207.2Hz0, Na#Od. 10HZOand Na2S04 within the range from T=293.15 K to T=298.15 K. Jukov and Shutova (3) have established the composition of the invariant point (NaCl+Na,SO,+Na&O,.2HzO) in the quatemary system NaCl-Na$Oa-Na&YrzO,-Hz0 at T=293.15 K. In the literature we have found no data on the thermodynamic simulation of ternary and multicomponent solutions with the participation of sodium bichromate. In a previous study (7) the Pitzer ion-interaction model was used for simulation of the ternary KCl-KzCrz07-HzO,KBr-K2Cr207-H20 and KzS04-K2Crz07-HzO, and the quatemary KC1-KzS04-K&Z0,-HZ0 systems at T=298.15 K. It was shown that the Pitzer equations can be used to obtain a sufficiently exact description of the properties of solutions with the participation of bichromate salts. The purpose of the present paper is a thermodynamic simulation, on the basis of Pitzer model, of the ternary systems NaCl-NazCrz07-Hz0 and Na#04-Na&07-HzO, and the quatemary system NaC1-Na2S04-NazCrz07-H20at T=298.15 K. 2. Solubility calculations In agreement with the aim formulated above, the Pitzer ion-interaction model (8-l 1) was used, which allows the determination of the activity coefficients in saturated and unsaturated electrolyte Received on 27 August 1999 11
12
C. CHRISTOV
solutions with an accuracy of 2 to 6 per cent (12). The theoretical basis of an ion-interaction model has been presented in previous papers (7, 13). The basic Pitzer model has been successfully used for the solution of many theoretical and practical problems. It has been proved that the model can be used for sufficiently exact descriptions of the properties of saturated and unsaturated binary (68), ternary (7, 12-15) and multicomponent (7, 16-18) electrolyte solutions. In this paper the systems were investigated using an approach which had already been applied to other systems from which phases with a constant stoichiometric composition (simple and double salts) crystallize (7, 13-17). This approach consists of: determination of Pitzer binary parameters (p(O), p(l), p(2), C$; determination of the Pitzer ternary parameters (@MN and MM); calculation of the solubility isotherms of the three-component systems; calculation of the solubility isotherm of the quatemary system. 2.1. Binary Systems The values of the binary parameters of the systems NaCl-Hz0 and NazS04-HzO at T=298.15 K have been determined by many authors (8, 16, 18). Since the calculation of the compositions of saturated ternary solutions is the main purpose of the simulation, the applicability of the binary parameters to high concentrations of the binary solutions up to saturation at the lowest value of the standard deviation (6) is a very important criterion for the choice of the binary parameters. The p(O), p(l), p(2), and C$ values used here are given in Table 1. They are valid up to saturation or almost to saturation of the binary solutions. Their applicability has been proved by simulation of the multicomponent seawater system (18). TABLE 1 Pitzer Binary Parameters at T=298.15 K where CFis the Standard Deviation of the Osmotic Coefficients System
m_
p’0’
$1)
p(2)
NaCl-H20”
0.07650
0.26640
-
0.00127
6.0000
0.00100
Na#04-H20”
0.01958
1.11300
-
0.00497
4.0000
0.00300
NazCr207-HzOb
0.13513
-8.94435
-0.00495
3.8792
0.00268
2.03150
moL kg-’
cs
aReference 18. bReference 6. Calculated with al=2 and (XQ =l. In a previous study the isopiestic method has been used to determine the osmotic coefficients of binary Na&O,-Hz0 solutions at T=298.15 K (6). Optimum values of the binary parameters have been calculated (Table 1). On the basis of the data concerning p(O), B(l) p(2) and CQ and the concentration (m’) of the saturated binary solutions, the logarithm of the thermodynamic solubility product InK”,, for the solid phases (Table 2) was calculated. The small differences between the lnK”sp
THE NaCI-Na+O~-Na2Cr207-H20
SYSTEM
13
Jalues for NaCl and Na2S04. 10HzO obtained in this paper and those presented in refs. (16, 18) are nainly due to the different
ms values used for the calculation.
On the basis of lnK'&values and
Ising initial thermodynamic data of aqueous species (19) the standard molar Gibbs energy of formation AC”,,, of simple salts crystallizing from saturated binary solutions (Table 2) was :alculated. The A@,,, values obtained are compared with those proposed by Wagman et al. (19). The differences ‘are within error limits of an ion-interaction model. TABLE 2
Calculated Values of the Logarithm of the Thermodynamic Solubility Product Kospand of the Gibbs Energy of Formation AIG”, of Solid Phases Crystallizing from Saturated Binary Solutions
“Calculated using thermodynamic
data of Wagman et al. (19).
TABLE 3
Pitzer Ternary Parameters at T = 298.15 K System
0MN
Y’MNX
NaCl-Na2S04-HzOa
0.02
0.0014
NaCl-NazCrz07-HzO
0.10
-0.0100
NazS04-NazCrz07-H20
0.09
-0.0100
aReference 18.
14
C. CHRISTOV
2.2. Ternary Systems The ternary parameters were obtained from the experimental data on the solubilities in the ternary systems (7, 13-16). The thermodynamic model was built on the basis of Robertson’s results (1) for the system NaCl-NazCrz07-HzO, and of Rakovskii and Nikitina’s (4) and Borovskih and Vilnjanskii’s (5) for the system Na#04-Na&07-H20. The choice of the parameters is based on the minimum deviation of the logarithm of the solubility product lnK& for the whole crystallization curve of the component, from its value for the saturated binary solution. In addition, the InKi+, value for Na#Od crystallizing in the Na#04-Na2Crz07-Hz0 system had to be constant along the whole crystallization and ~Nx
the unsymmetrical
branch of sodium sulphate. In our calculations
of @IN
mixing terms Et3 and E8’, were included according to reference
(9). The lnK:p value found in this study for Na2S04 is equal to that of Harvie and Weare (18). Simulating the systems KCl-K$&O,-Hz0 and K$04-K&rZ07-H20 (7) the following parameter values: 8ci,cr207=0.10 and 8 so4,,crzo7=0.09 are proposed. Since the parameters 8c1,,crZo7and take into account only the ionic interactions of the type Cl-Crz07 and S04-Cr207, 8S04,CrZ07 respectively in ternary solutions, their values have to be constant for the potassium and sodium solutions. The WM( values only have been varied. The calculated ternary parameters are presented in Table 3. The solubility isotherms of the ternary systems at T=298.15 K are calculated on the basis of the thermodynamic properties obtained. A method described in previous works (7, 13- 16) has been used. The calculated solubility isotherms are presented in Figs. 1 and 2. Table 4 summarizes the predicted and experimentally found compositions of eutonic solutions. The calculated results agree very well with the experimental data. 2.3. Quaternary System The calculated thermodynamic functions (binary and ternary parameters of interionic interaction and thermodynamic solubility products) are used for the simulation of the system NaCl-Na$OdNazCrz07-H20 in the range of higher CrZ07’- concentrations. The values of Pitzer ternary parameters for the N&l-Na#04-H,0 system were taken from the literature (18) (Table 3). The composition of the invariant point (NaC1+NazS04+Na2Crz07) was calculated as a point where the chemical potential of all three components is constant. Table 4 shows the composition of the calculated and the experimentally determined [Jukow and Shutova (3)] eutonics. The composition calculated at T=298.15 K has been compared with those obtained experimentally at T=293.15 K. The type of the solubility diagrams of the ternary subsystems at T=293.15 K and T=298.15 K is the same, i.e. the same solid phases crystallize in them (l-5). This fact has permitted the above comparison. The calculated results agree very well with the experimental data. 3. Conclusion The theoretical solubility isotherms of the systems NaCl-NazCrz07-Hz0, Na2S04-NazCrz07-Hz0 and NaCl-Na2S04-NazCr207-Hz0 at T=298.15 K have been plotted. The agreement with the experiment is very good. This permits conclusions concerning (i) the applicability of the thermodynamic approach used to obtain a sufficiently precise description of the properties of
THE NaCI-Na2S04-Na2Cr207-H20
-7----
-
WJ
I
/
‘-,
/
15
SYSTEM
NalCrz0,.2H,0
%rJhoLkg”)
FIG. 1 system at T = 298.15 K: -
Molality m’ solubilities in NaCl-Na&O,-H,O experimental data: l, from reference 1.
, calculated values;
i i I
1 o.ooL__-__L___L 0.00
0.50
\_
-L_
_L-~‘-_L 1
.oo
1.so
_..\”
j
2.00
FIG. 2 Molality m’ solubilities in Na,SO.,-Na,Cr,O,-Hz0 system at T = 298.15 K:--, experimental data: o, from reference 4, l, from reference 5.
calculated values;
16
C. CHRISTOV
binary, ternary and multicomponent solutions with the participation of sodium bichromate, (ii) the correctness of the thermodynamic functions calculated in this paper, and (iii) the correctness of the experimental data on the solubilities available in the literature.
TABLE 4
Experimental and Predicted Compositions of Invariant Points for the Quaternary System NaCl - Na$304 - NazCrzO, - Hz0 and for the Ternary Subsystems. Solid Phases
NaC1+Na2S04 0.69
6.87
0.57
7.19
0.80
6.66
0.83
6.67 0.11
7.07
0.12
7.12
0.05
6.92
0.06
7.06
0.82
2.63
0.83
2.70
0.90
2.68
Calculated
0.84
0.09
6.57
Experimentalb
0.79
0.05
6.62
NazCrz07.2Hz0+ NaCl
NazCrz07.2Hz0+ Na2S04
Na2S04. lOH*O+ Na$SO,+
NaC1+Na2S04+ Na$Zrz07.2H20 I
aExperimental data of Robertson (1) at T=298.15 K; bExperimental data of Jukow and Shutova (3) at T=293.15 K; “Experimental data of Gerassimow (2) at T=293.15 K; dExperimental data of Rakovskii and Nikitina (4) at T=298.15 K; eExperimental data of Borovskih and Vilnjanskii (5) at T=298.15 K.
Acknowledgements This investigation Technology.
was supported in part by the German Ministry of Education,
Research
and
THE NaCI-Na2S04-Na$r207-H20
17
SYSTEM
References 1.
J. Robertson, J. Sot. Chem. Zmf. 43,334 (1924).
2.
J. Gerassimow, Z. Anorg. Chem. 187,321 (1930).
3.
A. Jukow and V. Shutova, Trudy Uralskogo Nauchno-Technicheskogo Goshimizdat,
4.
1, 1959, pp. 29-35.
A. Rakovskii and E. Nikitina, Trudy Instituta Chistqh. Himich. Reaktivov, Gosud. NauchnoTechnich. Izdattelstvo,
5.
L. Borovskih, Proizvodstva
6.
Znstituta,
11, 193 1, pp. 5- 14.
J. Vilnjanskii, hromovqh Iftoristqh
Trudy
Konferenzii
po
Usovershenstvovaniy
Tehnologii
solei, Goshimizdat, 1959, pp. 46-54.
C. Christov, S. Velikova, K. Ivanova and STanev,
Coil. Czech. Chem. Commun. 64, 595
(1999). 7.
C. Christov, CALPHAD 22,449 (1998).
8.
K. Pitzer, J. Phys. Chem. 77,268 (1973).
9.
K. Pitzer, J. Solution Chem. 4, 249 (1975).
10.
K. Pitzer and G. Mayorga, J. Phys. Chem. 77,230O (1973).
11.
K. Pitzer and G. Mayorga, J. Solution Chem. 3,539 (1974).
12.
K. Pitzer and J. Kim, J. Am. Chem. Sot. 96,570l
13.
C. Christov, CALPHAD 20,501 (1996).
14.
C. Christov, J. Chem. Thermodynamics
26, 1071 (1994).
15.
C. Christov, J. Chem. Thermodynamics
3 I,71 (1999).
16.
C. Christov, J. Chem. Thermodynamics
32,285 (2000).
17.
C. Christov, S. Petrenko, C. Balarew and V. Valyashko, Monatsh. Chem. 125,137l
18.
C. Harvie and J. Weare, Geochim. Cosmochim. Acta 44,981 (1980).
19.
D. Wagman, W. Evans, V. Parker,
(1974).
R. Schumm, I. Halow, S. Bayler, K. Chumey
Nutall, J. Phys. Chem. Re$ Data 11 (1982) (Suppl.2).
(1994).
and R.