Solid–Liquid Equilibria in the Quaternary System K⁺//H₂PO₄^2–, SO₄^2–,Cl^––H₂O at 298.2 K and 323.2 K

The solubility data of the quaternary system K⁺//H₂PO₄^2–, SO₄^2–, Cl^––H₂O is basically required for the design and optimization of the crystallization process of KH₂PO₄ which is produced by the solvent extraction method using the wet-process H₃PO₄ and KCl as the raw materials. In this study, the solubility data of the quaternary system K⁺//H₂PO₄^2–, SO₄^2–, Cl^––H₂O at 298.2 K and 323.2 K were investigated by the isothermal solution saturation method. The solubilities of salts and equilibrium solid phases were determined. The phase and water content diagrams were constructed based on the experimental results. The appearance of the phase diagram at 323.2 K is similar to that at 298.2 K, while the crystallization area of each salt varies slightly with the changing of temperature. The phase diagrams both contain one quaternary invariant point, three univariant curves, and three crystallization regions corresponding to KH₂PO₄, K₂SO₄, and KCl. The crystallization region of K₂SO₄ is the largest, while that of KCl is the smallest. The order of the three salts solubilities is KCl > KH₂PO₄ > K₂SO₄. The water content reaches its minimum value at the quaternary invariant point at each temperature

Visualization 1: Ultrasonic detection based on polarization-dependent optical reflection

3D visualization of the mouse ear. Originally published in Optics Letters on 01 February 2017 (ol-42-3-439