Solid–Liquid Equilibria in the Quaternary System KCl–KBr–K2B4O7

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Solid−Liquid Equilibria in the Quaternary System KCl−KBr−K2B4O7− H2O at 323 K Yong-Xia Hu,†,‡ Shi-Hua Sang,*,†,‡ Rui-Zhi Cui,†,‡ and Yuan Wang†,‡ †

College of Materials, Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, P. R. China Mineral Resources Chemistry Key Laboratory of Sichuan Higher Education Institutions, Chengdu 610059, P. R. China

‡

ABSTRACT: Solid−liquid equilibria in the quaternary system KCl−KBr−K2B4O7− H2O at 323 K were measured by isothermal solution saturation method. The equilibrium solid phases, solubilities of salts, and densities of saturated solutions in the system were determined. The experimental data were used to plot the phase diagram of the quaternary system KCl−KBr−K2B4O7−H2O at 323 K. It was found that the system contains solid solution K(Cl,Br), their solubility diagram has no invariant point, but has a univariant dissolution curve, and two crystallization regions corresponding to K(Cl,Br) and potassium borate quahydrate (K2B4O7·4H2O). Density values in the equilibrium solution increase with an increase of the potassium bromide concentration but decrease with an increase of the potassium chloride concentration. On the basis of the solubility data of salts and corresponding to the solid solution composition data for the quaternary system, the solid solution compositions were fitted with quadratic equations for the equilibrium liquid composition. The calculated results for the solid solution K(Cl,Br) are discussed briefly.

1. INTRODUCTION Nowadays, more and more attention and care are given to the high-salinity liquid mineral resources because of the gradual exhaustion of solid resources. However, not so long ago, many underground gasfield brines were found in the west of Sichuan Basin, China.1 The brines, with an average salinity up to 377 g· L−1, contain many chemical components such as potassium, bromine, sulfates, boron, and sodium chloride, as well as high contents of lithium, strontium, iodine, and rubidium. Besides NaCl, the K and B contents of the brines are unusually high, up to 53.3 g·L−1 and 4.994 g·L−1, respectively. These minerals generally meet the grades required for mining and would have very good exploitation prospects.2 Therefore, it is essential to study their relevant thermodynamic data, particularly the solubilities of salts in the brines at different temperatures with the aid of phase equilibria and phase diagrams, which are the theoretical basis of the exploitation and utilization of underground brine resources. In recent decades, a lot of research work for underground salt lake brines and gas field brines has been carried out in experimental study. For example, Li et al. measured the salt solubilities in the quinary Li−Na−K−Mg−SO4−H2O system at 298 K, and the calculated results using Pitzer model are in good agreement with experimental data.3 Aiming at borate-bearing brines, there were a large number of experimental studies, such as the ternary system Na−Li−B4O7−H2O at 288 K and the quaternary system Na−Br−SO4−B4O7−H2O at 323 K,4,5 as well as the quinary systems Li−Na−CO3−SO4−B4O7−H2O at 288 K, Na−K−Cl−SO4−B4O7−H2O at 323 K, and the stable equilibrium system Li−Mg−Cl−SO4−borate−H2O at 298 K.6−8 In addition, Felmy and Weare predicted the borate © 2014 American Chemical Society

mineral equilibria with the system (Na−K−Ca−Mg−H−Cl− SO4−CO2−B(OH)4−H2O) and made the application to Searles Lake, USA.9 Study on phase equilibria with Br-bearing systems have received more and more attention in recent years. Christov has made a considerable amount of research work in predicting the solubilities of bromides and solution behavior in solid−solution aqueous−solution equilibrium systems, and the thermodynamic models were made with Pitzer equations, having comparatively high calculating precision and favorable practicability.10−15 Beyond that, the Br-bearing phase equilibria of some ternary, quaternary, and quinary subsystems of the underground gasfield brines in Western Sichuan basin have been studied in a systematic research program by our group: K−B4O7−Br−H2O at 298 K,16 Na−Br−SO4−B4O7−H2O, and Na−K−Br−SO4− H2O at 323 K,5,17 Na−Cl−Br−B4O7−H2O at 348 K,18 Na− Cl−Br−SO4−H2O at 323 K and 348 K,19,20 and K−Cl−Br− SO4−H2O at 323 K, 348 K and 373 K,21−23 By intensive research on these Br-bearing systems, we have found that they can form solid solutions while containing Cl− and Br−. The solid phases in saltwater systems are usually pure salts, salt hydrates, or complex salts, but solid solutions are rarely met. 24 Since chlorine and bromine have similar ion radii, their chemical properties as salts are closely related. When the coexistence of Cl− and Br− precipitates a concentrated salt solution, the bromine does not form an independent mineral, and most of it cannot remain in the mother liquor; only a small Received: January 15, 2014 Accepted: April 22, 2014 Published: May 5, 2014 1886

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Table 1. Solubilities, Densities, and Equilibrium Solids of the Quaternary System KCl−KBr−K2B4O7−H2O at 323 Ka composition of dry salt composition of liquid phase 100·w(B)b

[m(KBr) + m(KCl) + m(K2B4O7) = 100 (g/100 g)]

solution density

no.,point

KBr

KCl

K2B4O7

m(KBr)

m(KCl)

m(K2B4O7)

m(H2O)

equilibrium solids

ρ/(g·cm−3)

1,G 2 3 4 5 6 7 8 9,F 10 11 12 13 14 15 16 17,H

0.00 2.14 5.45 7.56 9.97 12.46 17.45 18.81 20.50 20.89 23.15 24.56 27.07 30.43 33.36 36.76 39.47

26.67 25.62 24.70 22.87 21.54 20.73 17.03 16.35 15.60 15.25 13.87 12.63 10.87 8.42 5.93 3.27 0.00

5.83 5.68 5.41 5.11 4.94 4.65 4.29 3.96 3.89 3.76 3.45 3.47 3.51 3.55 3.56 3.58 3.71

0 6.4 15.33 21.27 27.35 32.93 45.01 48.08 51.26 52.36 57.20 60.40 65.31 71.77 77.85 84.29 91.41

82.06 76.61 69.46 64.35 59.09 54.78 43.93 41.79 39.01 38.22 34.27 31.06 26.22 19.86 13.84 7.50 0.00

17.94 16.99 15.21 14.38 13.55 12.29 11.07 10.12 9.73 9.42 8.52 8.53 8.47 8.37 8.31 8.21 8.59

207.69 199.04 181.13 181.37 174.35 164.27 157.96 155.62 150.06 150.65 147.12 145.97 141.25 135.83 133.37 129.31 131.59

KCl + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB K(CB) + KB KBr + KB

1.2817 1.2865 1.2892 1.3092 1.3310 1.3759 1.3870 1.4004 1.4076 1.4132 1.4695 1.4786 1.4829 1.5093 1.5186 1.5215 1.5586

a Standard uncertainties: u(T) = 0.1 K, u(ρ) = 0.0002 g·cm−3, u(w) = 0.005. bw(B) is the mass fraction of liquid phase component. K(CB) = K(Cl,Br), KB = K2B4O7·4H2O.

equilibrium liquid phase and the solid phase composition data with regression equation.

number replace the chlorine ion in the form of isomorphism, entering the lattice of salt and other chloride.25 In earlier studies on solid solution saltwater system, the scholars mainly measured the solubility data of salts in solution at room temperature under condition of 298 K, such as KCl−KBr− H2O.26 For NaCl−NaBr−H2O system, the solubilities had been reported from −20 °C to 70 °C.27 The equilibrium data of these systems containing Cl− and Br− are also presented;28−30 the kinetic results of these studies show that it is possible to predict qualitatively the effect of solution composition by considering the phase relationships in the formation of solid solutions. However, the solubility data involving solid solutions have not been reported very frequently, especially at the quaternary system. Hence, it is very necessary to conduct more in-depth study. The main components in the underground brines in Western Sichuan Basin can be approximately described with the Na−K− Cl−Br−SO4−B4O7−H2O system. In early studies for solid solutions, the corresponding solid phase composition data have seldom been reported and are even less probable for the quaternary system. Aiming at those solid solution phase systems, we inferred that there is correlation between the solid solution composition and the liquid phase composition. For this reason, our research work focuses on the quaternary system KCl−KBr−K2B4O7−H2O at 323 K, which is one quaternary subsystem of the underground brines. So far, the quaternary system KCl−KBr−K2B4O7−H2O at 373 K has been reported by us,23 but there is no report about the phase equilibrium of the subsystem at 323 K, which is the object of this work. It is worth noting that the relationship equations of equilibrium liquid phase and the solid phase composition data were given by regression equations. Consequently, the research work reported in this article includes three parts: (1) measure the densities and solubilities in the equilibrium solution for the quaternary system at 323 K, (2) identify the equilibrium solid phases, give the composition of dry salts, and plot the experimental phase diagram of the quaternary system, and (3) fit the relationship equation of

2. EXPERIMENTS 2.1. Reagents and Instruments. Deionized water, with a conductivity less than 1.2·10−4 S·m−1 and pH = 6.60 at 298.15 K, was used to prepare synthesized brines and for chemical analysis. The chemicals used in this work were all analytically pure (ChengDu KeLong Chemical Reagent Factory). They are KCl (100 w = 99.5), KBr (100 w = ≥ 99.0), and K2B4O7·4H2O (100 w = ≥ 99.0). An SHA-GW type oil-bath thermostatted vibrator (Jintan Guowang Instrument Factory) was used for equilibrium measurements. Its temperature control accuracy is ± 0.1 K after secondary calibration using a higher precise thermometer. A standard analytical balance of 110 g capacity and 0.0001 g resolution (AL104, the Mettler Toledo Instruments Co., Ltd.) was used to determine the solution densities. 2.2. Experimental Methods. The solid−liquid equilibria were studied using an isothermal solution saturation method. The system points were prepared by gradually adding the third salt to the solution containing the other two salts from low to high until the third salt is saturated. For example, in our system, from the invariant point of the ternary system K2B4O7−KBr− H2O at 323 K, we began to add the salt of KCl gradually. The prepared salts were dissolved into 50 mL of water in a sealed glass bottle; then, the bottles were placed in the oil-bath vibrator to make the system uniform and reach equilibrium in a gradual manner. Experimental results demonstrated that the equilibrium states can be established in 14 days under continuous vibration at 323 K. The sealed glass bottles were kept in the vibrator, which was controlled at 323 ± 0.1 K. The solutions were taken out periodically for chemical analysis. When the solution concentration did not change any more, thermodynamic equilibrium was established in the system. The sealed glass bottles needed to remain still for some time. After the liquid was clarified, the solution and wet crystals were taken out for physicochemical analysis. The pure solid phases were 1887

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solution densities are plotted in Figures 2 and 3. The X-ray diffraction photograph at point F of this system is presented in Figure 4, which indicates that the quaternary system KCl− KBr−K2B4O7−H2O at 323 K has no complex salt, but contains K2B4O7·4H2O and solid solution K(Cl,Br). It can be found from Table 1 and Figure 1 that the quaternary system KCl−KBr−K2B4O7−H2O at 323 K belongs to the solid solution system, which only contains one univariant curve (GH) and has no quaternary invariant point. The stable phase diagram has two crystallization regions [solid solution K(Cl,Br) and K2B4O7·4H2O]. According to Figure 2 and 3, it can be said that both solution density and m(H2O) change monotonically with the Br-concentration, or w(KBr). Otherwise, as the potassium chloride concentration decreased in solution, the potassium bromide concentration increased at the univariant curve, which indicated that potassium bromide has a strong salting-out effect on potassium chloride. Compared with the stable solubility data from the quaternary system KCl− KBr−K2B4O7−H2O at 373 K, 23 it can be found that the solubilities of KCl and KBr in the solution increase with an obvious increase in temperature. Potassium borate has a low solubility and is easy to crystallize from the equilibrium solution. Those results demonstrate that the system belongs to solid solution system and that has no quaternary invariant point at 323 K and 373 K. From Table 1 and Figure 2, we can find that the density values of solution are decreasing with the increase of the content of potassium chloride, and the density values of solution are increasing with the gradually increase of the content of potassium bromide. The minimum density of the solution is 1.2817 g·cm−3 when the potassium chloride concentration is 26.67% at point G, and correspondingly the maximum density of the solution is 1.5586 g·cm−3, where the potassium bromide concentration is 39.47% at point H. 3.2. Discussion. The solid phase compositions of the quaternary system KCl−KBr−K2B4O7−H2O at 323 K are in the two crystallization fields of K(Cl,Br) and K2B4O7·4H2O. We can infer from the experimental results given in Table 1 that the compositions of the solid solution and the corresponding equilibrium solution compositions are closely related. Mathematical software is used to analyze the data and determine a regression model among the parameters. A typical multiple regression model is shown in equation (1).

obtained by taking out the wet crystals from the sealed glass bottles, filtering the liquid phase, and washing first with an alcohol−water mixture and finally with pure alcohol, followed by air drying. The compositions of the solutions were analyzed quantitatively, and the solid phases were analyzed by the wet slag method supplemented X-ray diffraction (XRD; Siemens D500 X-ray diffractometer). The densities were measured with a density bottle, which has an uncertainty of 0.0002 g·cm−3. 2.3. Analytical Methods. The K+ concentration was evaluated from an ion charge balance, and assisted by sodium tetraphenylborate−hexadecyl trimethyl ammonium bromide titration (precision: 100 w = ± 0.5). The B4O2− 7 concentration was measured by basic titration (0.05 M NaOH) in the presence of mannitol with a phenolphthalein solution as indicator (precision: 100 w = ± 0.3). The total concentration of Cl− and Br− was determined by Mohr’s method with a silver nitrate standard solution (precision: 100 w = ± 0.3). The Br− concentration was determined by iodometry with a sodium thiosulfate standard solution (precision: 100 w = ± 0.5). The Cl− concentration was determined by subtraction method. The above analytical results are all averaged over two or several parallel samples, where the parallel samples in the same group have a blank sample as reference. Moreover, the components of the solid phase were determined by the wet residue method and were further identified by X-ray diffraction.

3. RESULTS AND DISCUSSION 3.1. Results. The experimental results of the solubilities, densities, and equilibrium solids of the quaternary system KCl− KBr−K2B4O7−H2O at 323 K are tabulated in Table 1. The ion concentration values are expressed in mass fraction in the equilibrium solution. The solution densities were given in grams per cubic centimeter. The composition of dry salts are expressed in m(B), which can be defined as follows: m(B) = 100

w(B) ws

ws = w(KCl) + w(KBr) + w(K 2B4O7 )

where subscript “s” means “all dry salts”, and component B can be K2B4O7, KCl, KBr, or H2O. On the basis of the experimental results in Table 1, the phase diagram of the quaternary system at 323 K is plotted in Figure 1, the density-composition and water content diagram of the

y = a0 + a1x1 + a 2x 2 + a3x3 + a4(x1)2 + a5(x 2)2 + a6(x3)2

(R2)

(1)

where a0, a1, a2, ..., a6 are regression coefficients, y is the concentration of KBr of solid solution [mass %], x1 is the concentration of KBr of liquid phase [mass %], x2 is the concentration of KCl of liquid phase [mass %], x3 is the concentration of K2B4O7 of liquid phase [mass %], and R2 is the coefficient of determination. The main concern in this work is the effect of the concentration of KBr, KCl, and K2B4O7 of the liquid phase on the KBr mass percentage of the solid solution. The regression equation is presented as follow: y1 = 187.646 + 1.085x1 − 2.441x 2 − 49.547x3 − 0.009(x1)2 + 0.002(x 2)2 + 4.836(x3)2 Figure 1. Equilibrium phase diagram of the quaternary system KCl− KBr−K2B4O7−H2O at 323 K.

(R2 = 0.9989) 1888

(2)

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Figure 2. Density-composition diagram of the quaternary system KCl−KBr−K2B4O7−H2O at 323 K.

Table 2. Experimental Composition and Calculated Composition of Solid Solution of the Quaternary System KCl−KBr−K2B4O7−H2O at 323 Ka experimental composition of solid solution 100·w(B)b

calculated composition of solid solution 100·w(B)c

relative deviation

relative deviation

no.,point

KBr(y0)

KCl

KBr (y1)

KBr (y2)

|y0 − y1|

|y0 − y2|

1,G 2 3 4 5 6 7 8 9,F 10 11 12 13 14 15 16 17,H

0.00 2.91 7.23 12.50 18.51 25.54 38.61 45.55 49.38 52.05 58.36 66.42 71.32 77.41 83.79 91.93 100

100 97.09 92.77 87.50 81.49 74.46 61.39 54.45 50.62 47.95 41.64 33.58 28.68 22.59 16.21 8.07 0.00

−0.52 3.30 7.71 13.65 19.17 24.20 39.29 45.12 48.95 51.70 61.09 64.66 69.79 76.97 84.32 92.01 99.19

−1.69 2.56 6.91 14.59 20.68 25.65 41.38 45.02 49.54 50.82 57.48 61.87 69.21 78.78 86.35 94.72 97.66

0.52 0.39 0.48 1.14 0.66 1.34 0.69 0.42 0.42 0.35 2.73 1.76 1.52 0.44 0.53 0.08 0.81

1.69 0.35 0.32 2.09 2.17 0.11 2.77 0.53 0.16 1.23 0.88 4.55 2.11 1.37 2.56 2.79 2.34

Figure 3. Water content diagram of the quaternary system KCl−KBr− K2B4O7−H2O at 323 K.

Standard uncertainties: u(T) = 0.1 K, u(ρ) = 0.0002 g·cm−3, u(w) = 0.005. bw(B) is the mass fraction of solid solution component. cw(B) is the mass fraction of calculated solid phase component by equation; y1 is the mass fraction of calculated solid phase component by equation 2; y2 is the mass fraction of calculated solid phase component by equation 3. a

Figure 4. X-ray diffraction photograph at point F of the quaternary system KCl−KBr−K2B4O7−H2O at 323 K [solid solution K(Cl,Br) + K2B4O7·4H2O].

considering the concentration of K2B4O7 in the solution. The other regression equation is given in mathematical equation 3. y2 = 16.807 − 0.227x1 + 3.009x 2 + 0.058(x1)2 − 0.139(x 2)2

The regression equation 2, expresses the relationship equation of equilibrium liquid phase and the solid phase composition data, and the coefficient of determination (R2) is 0.9989. According to Table 2, the maximum relative deviation is 2.73% and the average relative deviation is 0.84%. Although the calculated results from the regression equation 2 are credible, multiple regression analyses show that the concentration of K2B4O7 of the liquid phase has a small contribution to the model. And therefore, the influence of the concentration of KBr and KCl are included in our modeling, without

(R2 = 0.9958)

(3) 2

The coefficient of determination (R ) is 0.9958 in regression equation 3, According to Table 2, the maximum relative deviation is 4.55 %, and the average relative deviation is 1.64 % in the quaternary system KCl−KBr−K2B4O7−H2O at 323 K, the calculated results from the regression equation 3 are reliable. Based on the independent equation 2 and equation 3, potassium borate should prove to be a relatively small contribution to the formation of solid solution, that is, K(Cl,Br). 1889

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solution behaviour and (solid + liquid) equilibria in the MgBr2(aq), and (m1KBr + m2MgBr2)(aq) systems to high concentration and temperature. J. Chem. Thermodyn. 2011, 43, 344−353. (12) Christov, C. Temperature variable chemical model of bromide− sulfate solution interaction parameters and solid−liquid equilibria in the Na−K−Ca−Br−SO4−H2O system. CALPHAD 2012, 36, 71−81. (13) Christov, C. Study of bromide salts solubility in the (m1KBr + m2CaBr2)(aq) system at T = 323.15 K. Thermodynamic model of solution behaviour and (solid + liquid) equilibria in the ternaries (m1KBr + m2CaBr2)(aq), and (m1MgBr2 + m2CaBr2)(aq), and in the quinary (Na + K + Mg + Ca + Br + H2O) systems to high concentration and temperature. J. Chem. Thermodyn. 2012, 55, 7−22. (14) Christov, C. Isopiestic investigation of the osmotic coefficients of aqueous CaBr2 and study of bromide salt solubility in the NaBr− CaBr2−H2O system at 50°C: Thermodynamic model of solution behavior and solid−liquid equilibria in the CaBr2−H2O, and NaBr− CaBr2−H2O systems to high concentration and temperature. CALPHAD 2011, 35, 42−53. (15) Christov, C. Study of bromide salts solubility in the (m1NaBr + m2MgBr2)(aq) system at T = 323.15 K, Thermodynamic model of solution behavior and solid−liquid equilibria in the (Na + K + Mg + Br + H2O) system to high concentration and temperature. J. Chem. Thermodyn. 2012, 47, 335−340. (16) Sang, S. H.; Yin, H. A.; Ni, S. N.; Zhang, C. J. A study on the equilibrium solubilities of salts and properties of solutions in the ternary system K2B4O7−KBr−H2O at 298 K. J. Chengdu Univ. Tech. 2006, 33, 414−416 in Chinese. (17) Zeng, X. X.; Sang, S. H.; Wang, D.; Zhang, J. J. Theoretical calculation of phase equilibria in the reciprocal quaternary system Na+, K+//Br−, SO42−−H2O at 323 K. Chem. Eng. 2012, 40(5), 32-35 (in Chinese). (18) Li, T; Sang, S. H; Cui, R. Z.; Zhang, K. J. Phase equilibria of quaternary system NaCl−NaBr−Na2B4O7−H2O at 348 K. Chem. Res. Chin. Univ. 2013, 29 (2), 311−313. (19) Sang, S. H.; Cui, R. Z.; Hu, J. W.; Wang, D. Measurements of the solid−liquid equilibria in the quaternary system NaCl−NaBr− Na2SO4−H2O at 323 K. J. Solution Chem. 2013, 42, 1633−1640. (20) Zhang, Y. G.; Sang, S. H.; Zhang, K. J.; Hu, F. M.; Cui, R. Z. Equilibria in the quaternary system NaCl−NaBr−Na2SO4−H2O at 348 K. J. Salt Chem. Ind. 2013, 42 (2), 12−15 in Chinese. (21) Wang, D.; Sang, S. H.; Zeng, X. X.; Ning, H. Y. The phase equilibria of quaternary system KCl−KBr−K2SO4−H2O at 323 K. Petrochem. Technol. 2011, 40 (3), 285−288 in Chinese. (22) Zhang, K. J.; Sang, S. H.; Li, T.; Cui, R. Z. Liquid−solid equilibria in the quaternary system KCl−KBr−K2SO4−H2O at 348 K. J. Chem. Eng. Data 2013, 58 (1), 115−117. (23) Cui, R. Z.; Sang, S. H; Hu, Y. X. Solid−liquid equilibria in the quaternary systems KCl−KBr−K2B4O7−H2O and KCl−KBr−K2SO4− H2O at 373 K. J. Chem. Eng. Data 2013, 58 (2), 477−481. (24) Niu, Z. D.; Cheng, F. Q. The Phase Diagrams of Salt-Water Systems and Their Applications; Tianjin: Tianjin University Press, 2002 (in Chinese). (25) Voloshin, A. E.; Kovalev, S. I.; Rudneva, E. B.; Glikin, A. E. Phenomena and mechanisms of mixed crystal formation in solutions II. Mechanism of interface processes. J. Cryst. Growth 2004, 261, 105− 117. (26) Silcock, H. L. Solubilities of inorganic and organic compounds, ternary and multicomponent systems of inorganic substances. Oxford Pergamon Press: U.K., 1979; Vol. 3, pp 593−598. (27) Silcock, H. L. Solubilities of inorganic and organic compounds, ternary and multicomponent systems of inorganic substances. Oxford Pergamon Press: U.K., 1979; Vol. 2, pp 1051−1055. (28) Putnis, C. V.; Mezger, K. A mechanism of mineral replacement: Isotope tracing in the model system KCl−KBr−H2O. Geochim. Cosmochim. Acta 2004, 68 (13), 2839−2848. (29) Putnis, A.; Putnis, C. V. The mechanism of reequilibration of solids in the presence of a fluid phase. J. Solid State Chem. 2007, 180, 1783−1786.

4. CONCLUSION The quaternary system KCl−KBr−K2B4O7−H2O at 323 K was studied by the isothermal solution saturation method. The equilibrium solid phases, solubilities of salts, and densities of saturated solutions were measured experimentally. On the basis of the experimental data, a phase diagram was plotted. The experimental results show that the solid solution K(Cl,Br) is found and no double salts are formed in the quaternary system. In the phase diagram of KCl−KBr−K2B4O7−H2O at 323 K, there is one univariant curve and two regions of crystallization, i.e. solid solution K(Cl,Br) and K2B4O7·4H2O. Potassium borate has a relatively small contribution to the formation of solid solution, that is, K(Cl,Br) using the regress analysis method.

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AUTHOR INFORMATION

Corresponding Author

*Tel: 13032845233. E-mail: [email protected]. Funding

The project was supported by the National Natural Science Foundation of China (41373062, 40973047), the Specialized Research Fund (20125122110015) for the Doctoral Program of Higher Education of China, and the youth science and technology innovation team of Sichuan Province, China (2013TD0005). Notes

The authors declare no competing financial interest.

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REFERENCES

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(30) Durham, G. S.; Rock, E. J.; Frayn, S. F. Solid solutions of the alkali halides. 1. The systems KBr−KCl−H2O, RbBr−RbCl−H2O1 RbBr−KBr−H2O2 at 25°. J. Am. Chem. Soc. 1953, 75, 5793−5794.

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dx.doi.org/10.1021/je500051e | J. Chem. Eng. Data 2014, 59, 1886−1891