The article presents a study on the polythermal solubility of the NaClO3–H2SO4·N(C2H4OH)3–H2O ternary system, aiming to develop a new effective defoliant with mild action. The research used the visual-polythermal method to investigate the system's solubility across a temperature range of -28.5 to 70.0°C. A polythermal solubility diagram was constructed, delineating the crystallization fields of ice, sodium chlorate, triethanolammonium sulfate, and a new compound, sodium sulfate triethanolammonium. The system was found to be of the complex eutonic type. The study highlights the importance of understanding solubility and phase equilibrium in salt systems for various applications, including agriculture. Sodium chlorate is primarily used for defoliation and desiccation, but its "hard" effect on plants limits its use. To mitigate this, researchers suggest adding substances with physiological activity, such as triethanolammonium sulfate, to the defoliant composition. The study also emphasizes the role of solubility data in the physicochemical substantiation of new defoliant synthesis. The experimental methods involved the use of liquid nitrogen to freeze solutions and determine crystallization temperatures, as well as various analytical techniques for quantifying the components. The results showed that the eutectic point of the H2SO4·N(C2H4OH)3–H2O system occurs at -24.0°C, with the components present in a specific ratio. The study contributes to the understanding of the NaClO3–H2SO4·N(C2H4OH)3–H2O system's solubility behavior, which is crucial for developing an effective and mild defoliant. The findings have implications for agriculture, where the use of synthetic products is increasing, and there is a need to enhance crop yields and reduce production costs.The article presents a study on the polythermal solubility of the NaClO3–H2SO4·N(C2H4OH)3–H2O ternary system, aiming to develop a new effective defoliant with mild action. The research used the visual-polythermal method to investigate the system's solubility across a temperature range of -28.5 to 70.0°C. A polythermal solubility diagram was constructed, delineating the crystallization fields of ice, sodium chlorate, triethanolammonium sulfate, and a new compound, sodium sulfate triethanolammonium. The system was found to be of the complex eutonic type. The study highlights the importance of understanding solubility and phase equilibrium in salt systems for various applications, including agriculture. Sodium chlorate is primarily used for defoliation and desiccation, but its "hard" effect on plants limits its use. To mitigate this, researchers suggest adding substances with physiological activity, such as triethanolammonium sulfate, to the defoliant composition. The study also emphasizes the role of solubility data in the physicochemical substantiation of new defoliant synthesis. The experimental methods involved the use of liquid nitrogen to freeze solutions and determine crystallization temperatures, as well as various analytical techniques for quantifying the components. The results showed that the eutectic point of the H2SO4·N(C2H4OH)3–H2O system occurs at -24.0°C, with the components present in a specific ratio. The study contributes to the understanding of the NaClO3–H2SO4·N(C2H4OH)3–H2O system's solubility behavior, which is crucial for developing an effective and mild defoliant. The findings have implications for agriculture, where the use of synthetic products is increasing, and there is a need to enhance crop yields and reduce production costs.