The vapor–liquid equilibria and solid phase of the mixed aqueous solutions of sodium and potassium fluorides were studied at different temperatures from 298.15 to 353.15 K. The water activities of {yKF + (1 – y)NaF}(aq) at various ionic-strength fractions y with y = 0.20, 0.50, and 0.80 of KF were measured from dilute to saturation of the solution using the hygrometric method. From these measurements, the related thermodynamic properties were determined using the developed ion interaction model. The mixing ternary parameters θ_NaK and ψ_NaKF of the ternary system were evaluated and used with the ionic parameters of the pure electrolytes to predict the activity and osmotic coefficients at different temperatures. From these results, the behaviors of the mixed KF–NaF in aqueous solutions were described. Indeed, the activity coefficient values could indicate relatively the presence of the ionic association phenomenon manifested in the aqueous solutions. In fact, as the solution becomes more concentrated, the ions are associated to form an ion pairing. The solubility measurements were also performed at various ionic-strength fractions y. The mineral phases formed were detected by X-ray diffraction and show only a single crystalline form of NaF(s).

中文翻译：

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三元体系KF–NaF–H ₂ O在不同温度下的汽液平衡和固相

研究了在298.15至353.15 K的不同温度下氟化钠和氟化钾混合水溶液的气液平衡和固相。{ y KF +（1- y）NaF}（aq）在各种离子下的水活度-Strength馏分ÿ与Ý = 0.20，0.50，和KF为0.80，测定从稀使用吸湿方法将溶液的饱和度。从这些测量中，使用开发的离子相互作用模型确定相关的热力学性质。混合三元参数θ_的NaK和ψ _NaKF对三元体系的电导率进行了评估，并将其与纯电解质的离子参数一起用于预测不同温度下的活性和渗透系数。根据这些结果，描述了混合KF-NaF在水溶液中的行为。实际上，活度系数值可以相对地指示水溶液中表现出的离子缔合现象的存在。实际上，随着溶液变得更浓，离子缔合形成离子对。溶解度测量也在各种离子强度分数y下进行。通过X射线衍射检测形成的矿物相，并且仅显示出NaF的单晶形式。