Phase Equilibria and Solubility Diagram in the Ternary System Sodium Hypochlorite – potassium Chlorate – water

Abstract

Phase equilibria and solubility in the NaClO–KClO₃–H₂O ternary system were investigated over the temperature range from −21 to +18 °C using the visual-polythermal method. Based on experimental data obtained for the boundary binary systems and five internal sections, a complete polythermal solubility diagram was constructed. The diagram reveals the crystallization fields of ice, potassium chlorate, sodium chloride, sodium hypochlorite pentahydrate (NaClO•5H₂O), sodium hypochlorite sesquihydrate (NaClO•2.5H₂O), and anhydrous NaClO. It was established that the system belongs to a simple eutectic type, with no formation of new chemical compounds or solid solutions within the investigated range. A pronounced salting-out effect of sodium hypochlorite on potassium chlorate was observed, leading to a significant decrease in KClO₃ solubility with increasing NaClO concentration. The obtained results provide a physicochemical basis for optimizing crystallization processes and developing efficient chlorate-based defoliant formulations.