Solid–liquid phase equilibrium for the ternary system urea phosphate + ammonium dihydrogen phosphate + water at 25 and 55 °C

The ternary system of urea phosphate + ammonium dihydrogen phosphate + water at 25 and 55 °C was investigated by the method of isothermal solution saturation and moist residues. Solubility and density data of the system were determined experimentally, and corresponding phase diagrams were constructed on the basis of solubility data. The solid phase in this system was comfirmed by Schreinemaker's method of wet residue. The trajectories at different temperatures are approximately similar, and the crystallization regions of urea phosphate and ammonium dihydrogen phosphate increase as the temperature decreases. The solubility data, density, and the phase equilibrium diagrams for the ternary system can provide the fundamental basis for the preparation of urea phosphate in ammonium dihydrogen phosphate and urea phosphate aqueous mixtures.

► The experimental SLE data of the ternary system were measured at 25 °C and 55 °C.
► Solubility (liquidus) curves have been determined.
► The study of phase diagram shows the eutectic points of the systems.
► Results can be used to separate and purify urea phosphate product from the ternary system.