The study investigates the polythermal solubility of the NaClO3-H2SO4·N(C2H4OH)3-H2O ternary system to develop a new effective defoliant. The solubility was determined using the visual-polythermal method across a temperature range of -28.5 to 70.0°C. A polythermal solubility diagram was constructed, delineating crystallization fields for ice, sodium chlorate, triethanolammonium sulfate, and a new compound, sodium sulfate triethanolammonium. The system is classified as a complex eutonic type. The research aims to create a defoliant with mild action based on sodium chlorate and triethanolammonium nitrate, which has physiological activity. The study used a visual-polythermal method, involving liquid nitrogen to freeze solutions to their crystallization temperature. A thermometer was used to measure crystallization temperatures. The production of triethanolammonium sulfate involved neutralizing triethanolamine with sulfuric acid using a stirrer. Quantitative analysis of the system components was performed using various methods, including permanganometric, flame photometry, gravimetric, and elemental analysis. Each sample was analyzed three times to minimize human error, and bidistilled water was used for solution preparation. The solubility of the NaClO3-H2O binary system was previously studied, and results were consistent. The study of the H2SO4·N(C2H4OH)3-H2O binary system revealed a eutectic point at -24.0°C with specific component ratios. The ternary system's solubility was analyzed using seven internal cuts, with sections studied from different sides of the system. The results provide insights into the system's behavior and contribute to the development of a new defoliant with improved properties.The study investigates the polythermal solubility of the NaClO3-H2SO4·N(C2H4OH)3-H2O ternary system to develop a new effective defoliant. The solubility was determined using the visual-polythermal method across a temperature range of -28.5 to 70.0°C. A polythermal solubility diagram was constructed, delineating crystallization fields for ice, sodium chlorate, triethanolammonium sulfate, and a new compound, sodium sulfate triethanolammonium. The system is classified as a complex eutonic type. The research aims to create a defoliant with mild action based on sodium chlorate and triethanolammonium nitrate, which has physiological activity. The study used a visual-polythermal method, involving liquid nitrogen to freeze solutions to their crystallization temperature. A thermometer was used to measure crystallization temperatures. The production of triethanolammonium sulfate involved neutralizing triethanolamine with sulfuric acid using a stirrer. Quantitative analysis of the system components was performed using various methods, including permanganometric, flame photometry, gravimetric, and elemental analysis. Each sample was analyzed three times to minimize human error, and bidistilled water was used for solution preparation. The solubility of the NaClO3-H2O binary system was previously studied, and results were consistent. The study of the H2SO4·N(C2H4OH)3-H2O binary system revealed a eutectic point at -24.0°C with specific component ratios. The ternary system's solubility was analyzed using seven internal cuts, with sections studied from different sides of the system. The results provide insights into the system's behavior and contribute to the development of a new defoliant with improved properties.