Solubility determination and thermodynamic modeling of 5-nitro-8-hydroxyquinoline in ten organic solvents from T = (278.15 to 313.15) K and mixing properties of solutions

• Solubility of 5-nitro-8-hydroxyquinoline in ten solvents were determined.
• The solubility were correlated with four models.
• The mixing properties were evaluated.

The solubility of 5-nitro-8-hydroxyquinoline in ten organic solvents including methanol, ethanol, acetone, acetonitrile, acetic acid, n-propanol, toluene, isopropanol, ethyl acetate and 1-butanol was determined experimentally by using the isothermal saturation method over a temperature range from (278.15 to 313.15) K under 101.3 kPa. For the temperature range studied, the solubility of 5-nitro-8-hydroxyquinoline in the solvents increased with a rise of temperature. In general, they obeyed the following order from high to low in different solvents: acetone > ethyl acetate > toluene > acetic acid > acetonitrile > 1-butanol > (n-propanol, ethanol) > isopropanol > methanol. The acquired solubility data of 5-nitro-8-hydroxyquinoline in the solvents studied were correlated by using the modified Apelblat equation, λh equation, Wilson model and NRTL model. The maximum values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 1.10 × 10−4 and 1.39%, respectively. Generally, the RAD   values acquired with the modified Apelblat equation were smaller than those with the other three models for a certain solvent. Generally, the four thermodynamic models were all acceptable for the systems of 5-nitro-8-hydroxyquinoline in these solvents. Furthermore, the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (γ1∞) and reduced excess enthalpy (H1E,∞) were obtained. The solution process of 5-nitro-8-hydroxyquinoline was spontaneous and endothermic in the studied solvents. The obtained solubility and thermodynamic studies would be very helpful for optimizing the purification process of 5-nitro-8-hydroxyquinoline.

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