Thermodynamic analysis and correlation of cyromazine in three (acetic acid, propanoic acid or ethylene glycol + water) binary solvents at different temperatures

The solubility of cyromazine in three binary solvent mixtures (acetic acid + water, propanoic acid + water, ethylene glycol + water) were measured by a gravimetric method from 278.15 K to 333.15 K under atmospheric pressure. The experimental results reveal that the mole fraction solubility of cyromazine increased with the increase of temperature in the three solvents. The Apelblat equation, the λh equation, the general single model (GSM) equation and the modified Jouyban-Acree model equation were all applied to correlate the experimental solubility of cyromazine well. Moreover, the dissolution thermodynamic properties: ΔsolH0 (the apparent standard enthalpy change), ΔsolS0 (the apparent standard entropy change), ΔsolG0 (the apparent standard Gibbs energy change), ζH (relative contribution of enthalpy) and ζTS (relative contribution of entropy) of the dissolution of cyromazine in the selected solvents were calculated. The positive values of ΔsolH0, ΔsolG0, ζH ≥ 0.5984 and ζTS ≤ 0.4016 indicated that the dissolution of cyromazine in the three binary solvents was enthalpy-driving and endothermic process. The experimental solubility of cyromazine in this work can provide good guidance and fundamental data for the crystallization, purification and application of cyromazine.