The solubility of 5,5-dimethylhydantoin (DMH) in 12 pure solvents including water, methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, isobutyl alcohol, 2-butanol, 1-pentanol, ethyl acetate, propyl acetate, and acetonitrile was measured at temperatures from 283.15 to 323.15 K under atmospheric pressure by a gravimetric method. The values of the mole fraction solubility of DMH in these solvents increase with increasing temperature and present the following order at a fixed temperature: methanol > ethanol > 2-butanol > isopropyl alcohol > 1-propanol > isobutyl alcohol (1-butanol) > 1-pentanol > water > acetonitrile > ethyl acetate > propyl acetate. They were mathematically correlated by the modified Apelblat equation, van’t Hoff equation, λh equation, and the Wilson model. The results showed a satisfactory correlation for each model.

The solid–liquid equilibrium solubility of isatoic anhydride in 12 pure solvents (methanol, ethanol, 1-propanol, isopropyl alcohol, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, acetone, 2-butanone, acetonitrile, and 1,4-dioxane) at T = 288.15 to 328.15 K was measured by the gravimetric method under atmospheric pressure. Experimental results demonstrate that the mole fraction solubility of isatoic anhydride in these selected solvents increased with the increase of temperature, and the dissolution behavior is affected by multiple factors like polarity, H-bond interaction, cohesive energy density, etc. The modified Apelblat model, the van’t Hoff model, the nonrandom two-liquid model, and the λh model were used to correlate the experimental solubility data. The maximum values of the relative average deviation and root-mean-square deviation were no more than 4.23 × 10–2 and 5.31 × 10–4, respectively. Furthermore, the thermodynamic properties including the mixing Gibbs energy, mixing enthalpy, and mixing entropy were calculated, which indicates that the dissolution of isatoic anhydride was a spontaneous and entropy-favorable process.