<p>The solubility of the 2HNIW∙HMX co-crystal was experimentally determined in nine mono solvents (methyl acetate, ethyl acetate, acetonitrile, butanone, toluene, m-xylene, methanol, dichloromethane, and 1,2-dichloroethane) over the temperature range 283.15–313.15 K at atmospheric pressure using the gravimetric method. The solubility decreased with increasing temperature in methyl acetate and ethyl acetate, while an increasing trend was observed in the other seven solvents. Among all solvents, methyl acetate exhibited the highest average solubility (0.02687, mole fraction), whereas methanol showed the lowest (0.0004103, mole fraction). Analysis of solvent properties indicated that the dissolution behavior involves a complex interplay of factors such as polarity and cohesive energy density. The experimental solubility data were correlated with four thermodynamic models (the van’t Hoff equation, the modified Apeblat equation, the Yaws model, and the polynomial empirical equation). The modified Apeblat equation and Yaws model provided the best agreement with the measured data. Thermodynamic dissolution parameters, including the standard enthalpy change (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\Delta {H}_{\text{sol}}^{^\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mi>H</mi> <mrow> <mtext>sol</mtext> </mrow> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation>), the standard entropy change (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\Delta {S}_{\text{sol}}^{^\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mi>S</mi> <mrow> <mtext>sol</mtext> </mrow> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation>), and the standard Gibbs free energy change (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\Delta {G}_{\text{sol}}^{^\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mi>G</mi> <mrow> <mtext>sol</mtext> </mrow> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation>), were derived based on the van’t Hoff equation and Gibbs equations. The positive values of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\Delta {G}_{\text{sol}}^{^\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <mmultiscripts> <mi>G</mi> <mrow> <mtext>sol</mtext> </mrow> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation> across all solvents indicate that the dissolution process is non-spontaneous. This study provides essential solubility data, model parameters, and thermodynamic insights that support the optimization of crystallization processes and further theoretical investigations of the 2HNIW∙HMX co-crystal.</p>

Solubility Measurement and Modeling of 2HNIW·HMX Co-Crystal in Nine Mono Solvents

期刊论文
发表日期：

2026年1月4日

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Qian Jia,
Hong Liu,
Yuxin Liu,
Tao Ding

摘要

The solubility of the 2HNIW∙HMX co-crystal was experimentally determined in nine mono solvents (methyl acetate, ethyl acetate, acetonitrile, butanone, toluene, m-xylene, methanol, dichloromethane, and 1,2-dichloroethane) over the temperature range 283.15–313.15 K at atmospheric pressure using the gravimetric method. The solubility decreased with increasing temperature in methyl acetate and ethyl acetate, while an increasing trend was observed in the other seven solvents. Among all solvents, methyl acetate exhibited the highest average solubility (0.02687, mole fraction), whereas methanol showed the lowest (0.0004103, mole fraction). Analysis of solvent properties indicated that the dissolution behavior involves a complex interplay of factors such as polarity and cohesive energy density. The experimental solubility data were correlated with four thermodynamic models (the van’t Hoff equation, the modified Apeblat equation, the Yaws model, and the polynomial empirical equation). The modified Apeblat equation and Yaws model provided the best agreement with the measured data. Thermodynamic dissolution parameters, including the standard enthalpy change ( $\Delta {H}_{\text{sol}}^{^\circ }$ $Δ H_{sol}^{^{\circ}}$ ), the standard entropy change ( $\Delta {S}_{\text{sol}}^{^\circ }$ $Δ S_{sol}^{^{\circ}}$ ), and the standard Gibbs free energy change ( $\Delta {G}_{\text{sol}}^{^\circ }$ $Δ G_{sol}^{^{\circ}}$ ), were derived based on the van’t Hoff equation and Gibbs equations. The positive values of $\Delta {G}_{\text{sol}}^{^\circ }$ $Δ G_{sol}^{^{\circ}}$ across all solvents indicate that the dissolution process is non-spontaneous. This study provides essential solubility data, model parameters, and thermodynamic insights that support the optimization of crystallization processes and further theoretical investigations of the 2HNIW∙HMX co-crystal.