Solubility Determination and Modeling for Flufenoxuron in Four Mixed Solvents from 278.15–323.15 K

As a common solvent, water cannot dissolve flufenoxuron in this study well; therefore, methanol was added to the water to form a liquid mixture of different compositions. At first, the ratio of methanol mass was 90%, and then, it decreased by 10% until the methanol content was 10%. According to the above method, n-propanol, propylene glycol, and N,N-dimethyl formamide were made into corresponding mixed solvents. Under a pressure of 101.2 kPa, the temperatures of flufenoxuron and the solvent were kept at 278.15 K. Based on the basic principle of the static gravimetric method, the amount of solute diffusion in the above four mixed solvents was obtained. Other conditions remained unchanged, the temperature was increased by 5 K, and the above steps were repeated until the temperature was 323.15 K. There were two variables in the experiment; the temperature changes to a higher level and more flufenoxuron can be detected in the solution. Regardless of the change in temperature variables, the larger the mass of the organic solvent, the more solutes in the solution. Three models were employed to calculate the solubility of flufenoxuron. The maximum results of relative average deviation and the root-mean-square deviation were 0.43% and 4.24 × 10–4.