Isopiestic determination of the osmotic and activity coefficients of Rb 2SO4 (aq) and Cs 2SO 4(aq) at T = (298.15 and 323.15) K,and representation with an extended ion-interaction (Pitzer) model

Isopiestic vapor-pressure measurements were made for Rb ₂SO ₄(aq) from molalitym =  (0.16886 to 1.5679 )mol · kg ^− 1atT =  298.15 K and from m =  (0.32902 to 1.2282 )mol · kg ^− 1at T =  323.15 K, and for Cs ₂SO₄ (aq) from m =  (0.11213 to 3.10815 )mol · kg ^− 1at T =  298.15 K and fromm =  (0.11872 to 3.5095 )mol · kg ^− 1atT =  323.15 K, with NaCl(aq) as the reference standard. Published thermodynamic information for these systems were reviewed and the isopiestic equilibrium molalities and dilution enthalpies were critically assessed and recalculated in a consistent manner. Values of the four parameters of an extended version of Pitzer`s model for osmotic and activity coefficients with an ionic-strength dependent third virial coefficient were evaluated for both systems at both temperatures, as were those of the usual three-parameter Pitzer model. Similarly, parameters of Pitzer`s model for the relative apparent molar enthalpies of dilution were evaluated at T =  298.15 K for both Rb ₂SO ₄(aq) and Cs ₂SO ₄(aq) for the more restricted range of m⩽ 0.101 mol · kg ^− 1. Values of the thermodynamic solubility product K_s(Rb₂ SO ₄, cr, 298.15 K )  =  (0.1392  ±  0.0154) and the CODATA compatible standard molar Gibbs free energy of formationΔ_fG_m^o (Rb ₂SO ₄, cr, 298.15 K )  =  − (1316.91  ±  0.59)kJ · mol ^− 1, standard molar enthalpy of formationΔ_fH_m^o (Rb ₂SO ₄, cr, 298.15 K )  =  − (1435.07  ±  0.60)kJ · mol ^− 1, and standard molar entropy S _m^o(Rb₂ SO ₄, cr, 298.15 K )  =  (199.60  ±  2.88)J · K ^− 1· mol ^− 1were derived. A sample of one of the lots of Rb ₂SO ₄(s) used for part of our isopiestic measurements was analyzed by ion chromatography, and was found to be contaminated with potassium and cesium in amounts that significantly exceeded the claims of the supplier. In contrast, analysis by ion chromatography of a lot of Cs ₂SO ₄(s) used for some of our experiments showed it was highly pure.     

Isopiestic Measurement of the Osmotic Coefficients of Aqueous {xH 2 SO 4 + (1− x)Fe 2 (SO 4 ) 3 } Solutions at 298.15 and 323.15 K

This study measures the osmotic coefficients of {xH₂SO₄ + (1−x)Fe₂(SO₄)₃}(aq) solutions at 298.15 and 323.15 K that have ionic strengths as great as 19.3 mol,kg⁻¹, using the isopiestic method. Experiments utilized both aqueous NaCl and H₂SO₄ as reference solutions. Equilibrium values of the osmotic coefficient obtained using the two different reference solutions were in satisfactory internal agreement. The solutions follow generally the Zdanovskii empirical linear relationship and yield values of a _w for the Fe₂(SO₄)₃–H₂O binary system at 298.15 K that are in good agreement with recent work and are consistent with other M₂(SO₄)₃–H₂O binary systems.     

Osmotic and Activity Coefficients of {yKCl+(1−y)MgCl2}(aq) at T=298.15 K

Isopiestic vapor-pressure measurements were made at the temperature 298.15 K for aqueous KCl + MgCl₂ solutions using KCl(aq) as the reference standard. The measurements for these ternary solutions were made at KCl ionic strength fractions of y=0.0, 0.1989, 0.3996, 0.5993, 0.7925 and 1.0 (with two additional sets at y=0.0, 0.2021, 0.3998, 0.6125, 0.8209 and 1.0) for the ionic strength range from 0.4014 to 6.2790 mol?kg^?1. Our results, and those from two previous isopiestic studies, were combined and used with previously determined parameters for KCl(aq) and those determined here for MgCl₂(aq) to evaluate mixing parameters for the Clegg-Pitzer-Brimblecombe model. These combined data were also used to determine the mixing parameters of the Scatchard model. Both sets of model parameters are valid for ionic strengths of I≤12.8 mol?kg^?1, where higher-order electrostatic effects have been included in the Clegg-Pitzer-Brimblecombe mixture model. The activity coefficients for KCl and MgCl₂ were calculated from these models and the results for KCl were compared to experimental data from Emf measurements. The Scatchard model interaction parameters were used for calculation of the excess Gibbs energy as a function of the ionic strength and ionic strength fraction of KCl. The Zdanovskii-Robinson-Stokes rule of linearity for mixing of isopiestic solutions was tested.     

Thermodynamic Properties of {NaCl-CsCl-LiCl}(aq) at T=298.15 K: Water Activities, Osmotic and Activity Coefficients

A hygrometric method has been used to measure water activities for the quaternary aqueous system NaCl-CsCl-LiCl-H₂O as a function of the solutes concentrations at T=298.15 K. The measurements were performed by measuring the diameter of solution droplets as a function of the surrounding relative humidity. The total ionic strength range covered in this study was about 0.6 to 6 mol?kg^?1 for different ionic strength fractions y of one of the three solutes ranging from y=1/3 to 1/2, whereas the constant ratio r of molalities of the two other solutes was fixed at unity. The osmotic coefficients of these aqueous mixtures were calculated over this ionic strength range. The obtained data were treated by the ECA I and ECA II rules, and the Pitzer and Kim, and Pitzer-Dinane models. The solute activity coefficients of components in the studied mixtures were also determined for different ionic strength fractions of the different solutes.     

298.15K下Li2B4O7-H2O体系水蒸汽分压及渗透系数的等压测定和离子相互作用模型

在已有研究含硼体系的文献中仅考虑了硼酸根B4O7^-2或B(OH)4^-和H3BO3的存在，而对Li2B4O7-H2O体系具有多种硼物种聚合平衡体系的热力学性质的研究尚未见报道．本文用等压法研究了Li2B4O7-H2O体系于298．15K下浓度由稀到过饱和溶液的平衡气相蒸汽压及渗透系数．考虑了水溶液中多种硼物种的存在，以Pitzer方程为基础，建立了可描述该含硼体系的离子相互作用模型。     

Thermodynamic properties of {(NH4)2SO4(aq) + Li2SO4(aq)} and {(NH4)2SO 4(aq) + Na2SO4(aq)} at a temperature of 298.15 K

The water activities and osmotic coefficients of aqueous solutions of {(NH₄ )₂SO ₄ +  Li ₂SO ₄} and {(NH₄ )₂SO ₄ +  Na ₂SO ₄} have been determined at a temperature of 298.15 K with a hygrometric method, at molalities in the region 0.2 mol · kg ^− 1 to saturation of the solutes for different fractional ionic-strengthsy =  0.2, 0.5, and 0.8 of (NH ₄)₂SO ₄. The experimental results are compared with the predictions obtained from our extended compared additivity model, as well as the models reported by Zdanovskii, Stokes and Robinson, Pitzer, and Lietzke-Stoughton. From these measurements, parameters of Pitzers model have been determined. These were used to predict solute activity coefficients in the mixture and calculate the excess Gibbs function at total molalities for different y for these systems.     

Mutual Diffusion Coefficients and Refractive Index Increments of K2SO4(aq) at 298.15 K from Rayleigh Interferometry

Journal of Solution Chemistry - Isothermal mutual diffusion coefficients (interdiffusion coefficients) were measured for K2SO4(aq) at 298.15?±?0.005 K, at numerous...     

等压法测定298.15K下LiCl-CaCl2-H2O体系的活度系数

The isopiestic method was used to determinate isopiestic molality and osmotic coefficients in single-salt solutions of LiCl-H2O(molality range from 0.5 to 9.0 mol· kg-1),CaCl2-H2O(molality range from 0.35 to 5.2 mol· kg-1) and multisalt solution LiCl-CaCl2-H2O(ionic strength range from 0.5 to 15.7 mol· kg-1) at 298.15K,from which Pitzer's interaction parameters of single salt ,mixed salts of the systems were obtained.The mean ionic activity coefficients of LiCl、 CaCl2 in pure and mixed solutions were reported.     

NaOH-Na2H2SiO4-H2O体系渗透系数的等压法测定及离子作用模型

采用等压法测定了313.15 K下NaOH-Na₂H₂SiO₄-H₂O体系在0.5695～6.4775 mol•kg^－1的离子强度范围及0.1461～0.3158的模数(SiO₂与Na₂O的物质的量比)范围内的等压平衡浓度, 计算了该混合体系的渗透系数和水活度. 用Pitzer离子相互作用模型对实验结果进行了参数化研究, 拟合求取了Pitzer离子相互作用参数. 用Pitzer模型计算的渗透系数值与实验结果一致, 说明该模型能较好的描述NaOH-Na₂H₂SiO₄-H₂O体系的热力学性质. 用Pitzer模型计算得到了该体系的各组分平均活度系数随离子强度及模数的变化规律, 并与Mckay-Perring方程计算得到的NaOH的平均活度系数进行了比较, 指出Mckay-Perring方程的适用性.     

Li2B4O7-MgCl2(B)-H2O体系热力学性质的等压研究及离子相互作用模型

采用等压法测定了298.15 K下Li-Mg-Cl-borate-H2O体系离子强度范围为0.0581～0.6320 mol*kg-1, MgCl2不同离子浓度分数的等压摩尔平衡浓度、水活度,计算了Li2B4O7和MgCl2混合溶液的饱和水蒸汽压、渗透系数等热力学性质.考虑了在不同的总硼浓度范围的硼酸(H3BO3)和硼氧配阴离子[B(OH)-4, B3O3(OH)-4, B4O5(OH)2-4]的不同生成反应平衡.由实验结果对修正的Pitzer渗透系数方程进行了参数化研究,提出了一简化的参数化模型,减少了模型的经验参数量,获得了锂、镁、氯离子与硼物种组合之间、及不同硼氧配阴离子之间的组合相互作用参数,用该模型计算的渗透系数值与实验结果取得合理的一致性,从而将离子作用模型扩展到对含硼、锂、镁的复杂体系的表述.对完善含锂、硼的盐湖卤水体系的热力学模型和盐湖资源的综合开发利用具有重要意义.     

NaOH-NaAl(OH)4-H2O溶液体系渗透系数的测定及离子作用模型

用等压法测定了在303.15 K时总碱质量摩尔浓度mNaOH(T)从0.61 mol/kg到5.72 mol/kg, 苛性比αK从1.98到7.04的NaOH-NaAl(OH)4-H2O溶液体系的等压平衡浓度和渗透系数, 并得到该溶液体系的水活度. 用Pitzer模型对实验结果进行了参数化研究, 拟合求得了离子相互作用参数. 用Pitzer模型计算的渗透系数值与实验结果一致. 用获得的参数计算了NaOH和NaAl(OH)4在NaOH-NaAl(OH)4-H2O溶液体系中的活度系数, 其值随总碱质量摩尔浓度的增加呈增加的趋势.     

Apparent molar heat capacities and apparent molar volumes ofY2(SO4)3(aq),La2(SO4)3(aq),Pr2(SO4)3(aq),Nd2(SO4)3(aq),Eu2(SO4)3(aq),Dy2(SO4)3(aq),Ho2(SO4)3(aq), andLu2(SO4)3(aq)atT = 298.15 K andp = 0.1 MPa

The apparent molar heat capacities C_{p, φ} ^∘ and apparent molar volumes V_φ ^∘ of Y₂(SO₄)₃(aq), La₂(SO₄)₃(aq), Pr₂(SO₄)₃(aq), Nd₂(SO₄)₃(aq), Eu₂(SO₄)₃(aq), Dy₂(SO₄)₃(aq), Ho₂(SO₄)₃(aq), and Lu₂(SO₄)₃(aq) were measured at T =  298.15 K and p =  0.1 MPa with a Sodev (Picker) flow microcalorimeter and a Sodev vibrating-tube densimeter, respectively. These measurements extend from lower molalities of m =  (0.005 to 0.018) mol ·kg ^− 1to m =  (0.025 to 0.434) mol ·kg ^− 1, where the upper molality limits are slightly below those of the saturated solutions. There are no previously published apparent molar heat capacities for these systems, and only limited apparent molar volume information. Considerable amounts of the R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are present, where R denotes a rare-earth, which complicates the interpretation of these thermodynamic quantities. Values of the ionic molar heat capacities and ionic molar volumes of these complexes at infinite dilution are derived from the experimental information, but the calculations are necessarily quite approximate because of the need to estimate ionic activity coefficients and other thermodynamic quantities. Nevertheless, the derived standard ionic molar properties for the various R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are probably realistic approximations to the actual values. Comparisons indicate that V_φ ^∘ {RSO₄ ⁺ , aq, 298.15K}  =  − (6  ±  4)cm³· mol ^− 1and V_φ ^∘ {R(SO₄)₂ ⁻ , aq, 298.15K}  =  (35  ±  3)cm³· mol ^− 1, with no significant variation with rare-earth. In contrast, values of C_{p, φ} ^∘ { RSO₄ ⁺ , aq, 298.15K } generally increase with the atomic number of the rare-earth, whereas C_{p, φ} ^∘ { R(SO₄)₂ ⁻ , aq, 298.15K } shows a less regular trend, although its values are always positive and tend to be larger for the heavier than for the light rare earths.     

Water activity,osmotic and activity coefficients of aqueous solutions of Li2SO4, Na2SO4, K2SO4, (NH4)2SO4, MgSO4, MnSO4, NiSO4, CuSO4, and ZnSO4 at T=298.15 K

The water activities for aqueous solutions of Li₂SO₄(aq), Na₂SO₄(aq), K₂SO₄(aq), (NH₄)₂SO₄(aq), and sulphates MgSO₄(aq), MnSO₄(aq), NiSO₄(aq), CuSO₄(aq), and ZnSO₄(aq) were determined experimentally at a temperature of 298.15 K with a hygrometric method, at molalities in the range from 0.1 mol·kg⁻¹ to saturation. The osmotic coefficients are calculated from these results. The coefficients of Pitzer’s model was used to fit the osmotic coefficients for each salt solution. These parameters were used to predict solute activity coefficients for the salts studied.     

Li2SO4-K2SO4-MgSO4-H2O体系及次级体系298.15K时的热化学研究

用连续滴定量热法研究Li2SO4-K2SO4-MgSO4-H2O体系及次级体系Li2SO4-K2SO40H2O、Li2SO4-MgSO4-H2O和K2SO4-MgSO4-H2O 298.15K时在离子强度为15-0.1范围内的比热容和稀释热, 并结合Debye-Huckel焓极限公式研究离子强度在15-0.0001范围内的表观摩尔焓。     

The low-temperature (5 to 310 K) heat capacity and thermodynamic functions of cesium fluoroxysulfate (CsSO4F) and the standard potential at 298.15 K for the half-reaction: SO4F−(aq) + 2H+(aq) + 2e− = HSO4−(aq) + HF(aq)

The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO₄F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity C_p^o(T) and standard entropy S^o(T) are (163.46±0.82) and (201.89±1.01) J · K^?1 · mol^?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔH_f^o the Gibbs energy of formation ΔG_f^o(CsSO₄F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol^?1. For the half-reaction: SO₄F^?(aq)+2H⁺(aq)+2e^? = HSO₄^?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V.     

等压法测定298.15K下LiCl-CaCl2-H2O体系的活度系数

电解质水溶液热力学性质的研究一直是一个很活跃的研究领域.对含锂水盐体系热力学性质的研究不仅对电解质水溶液理论,而且对盐湖锂资源的开放利用都有非常重要的意义.姚燕等对ＬｉＣｌＫＣｌＨ2Ｏ[1],ＬｉＣｌＭｇＣｌ2Ｈ2Ｏ[2],ＬｉＣｌＭｇＳＯ4Ｈ2Ｏ[3,4],ＬｉＣｌＬｉ2ＳＯ4Ｈ2Ｏ[5]体系多温下热力学性质进行了研究,应用Ｐｉｔｚｅｒ电解质水溶液理论模型进行处理,计算出ＬｉＣｌ在不同体系中,很大的浓度范围内的活度系数.但在盐湖卤水中,ＣａＣｌ2的存在很普遍.对ＬｉＣｌＣａＣｌ2混合物在水溶液中的热力学性质研究对理解ＬｉＣｌ在盐…