Solubility of KH₂PO₄ in KCl, H₃PO ₄, and their mixture solutions

The solubility data of KH₂PO₄ in the mixed solution of KCl and H₃PO₄ is basically required for designing and optimizing the preparation process of KH₂PO₄ from KCl and H₃PO₄ using solvent extraction. In this study, the solubility of KH₂PO₄ in KCl, H₃PO₄, and their mixture solutions has been measured respectively at temperatures of (288.2, 298.2 and 308.2) K. In KCl solutions, the solubility of KH ₂PO₄ decreases as the concentration of KCl increases before KCl begins to precipitate. In H₃PO₄ solutions, the solubility of KH₂PO₄ increases as the concentration of H₃PO₄ increases. In mixed solutions of approximately equimolar KCl and H₃PO₄, the solubility of KH ₂PO₄ decreases a little first and then increases remarkably with the increase of KCl (H₃PO₄) concentration. In the three systems studied, the solubility of KH₂PO₄ always increases with increasing temperature.