MOSCED

MOSCED (short for “modified separation of cohesive energy density" model) is a thermodynamic model for the estimation of limiting activity coefficients (also known as activity coefficient at infinite dilution). From a historical point of view MOSCED can be regarded as an improved modification of the Hansen method and the Hildebrand solubility model by adding higher interaction term such as polarity, induction and separation of hydrogen bonding terms. This allows the prediction of polar and associative compounds, which most solubility parameter models have been found to do poorly. In addition to making quantitative prediction, MOSCED can be used to understand fundamental molecular level interaction for intuitive solvent selection and formulation. In addition to infinite dilution, MOSCED can be used to parameterize excess Gibbs Free Energy model such as NRTL, WILSON, Mod-UNIFAC to map out Vapor Liquid Equilibria of mixture. This was demonstrated briefly by Schriber and Eckert using infinite dilution data to parameterize WILSON equation. The first publication is from 1984 and a major revision of parameters has been done 2005. This revised version is described here.

MOSCED (short for “modified separation of cohesive energy density" model) is a thermodynamic model for the estimation of limiting activity coefficients (also known as activity coefficient at infinite dilution). From a historical point of view MOSCED can be regarded as an improved modification of the Hansen method and the Hildebrand solubility model by adding higher interaction term such as polarity, induction and separation of hydrogen bonding terms. This allows the prediction of polar and associative compounds, which most solubility parameter models have been found to do poorly. In addition to making quantitative prediction, MOSCED can be used to understand fundamental molecular level interaction for intuitive solvent selection and formulation. In addition to infinite dilution, MOSCED can be used to parameterize excess Gibbs Free Energy model such as NRTL, WILSON, Mod-UNIFAC to map out Vapor Liquid Equilibria of mixture. This was demonstrated briefly by Schriber and Eckert using infinite dilution data to parameterize WILSON equation. The first publication is from 1984 and a major revision of parameters has been done 2005. This revised version is described here. \ln \gamma_2^{\infty } = \frac{\nu_2}{RT} \left[ \left( \lambda_1 - \lambda_2 \right)^2 + \frac{q_1^2 q_2^2 \left( \tau_1^T - \tau_2^T \right)^2}{\psi_1} + \frac{\left( \alpha_1^T - \alpha_2^T \right) \left( \beta_1^T - \beta_2^T \right)}{\xi_1} \right] + d_{12} d_{12} = \ln \left( \frac{\nu_2}{\nu_1} \right)^{aa} + 1 - \left( \frac{\nu_2}{\nu_1} \right)^{aa} aa = 0.953 - 0.002314 \left( \left( \tau_2^T \right)^2 + \alpha_2^T \beta_2^T \right) \alpha^T = \alpha \left( \frac\text{293 K}{T} \right)^{0.8} , \beta^T = \beta \left( \frac\text{293 K}{T} \right)^{0.8} , \tau^T = \tau \left( \frac\text{293 K}{T} \right)^{0.4} \psi_1 = \text{POL} + 0.002629 \alpha_1^T \beta_1^T \xi_1 = 0.68 \left( \text{POL} - 1 \right) + \left[3.4 - 2.4 \exp \left( -0.002687 \left( \alpha_1 \beta_1 \right)^{1.5} \right) \right]^{\left( 293 K/T \right)^2} \text{POL} = q_1^4 \left[ 1.15 - 1.15 \exp \left( -0.002337 \left( \tau_1^T\right)^3 \right) \right] + 1 with Important note: The value 3.4 in the equation for ξ is different from the value 3.24 in the original publication. The 3.24 has been verified to be a typing error. The activity coefficient of the solute and solvent can be extended to other concentrations by applying the principle of the Margules equation. This gives: \ln \gamma_2 = \left( \ln \gamma_2^\infty + 2 \left( \ln \gamma_1^\infty - \ln \gamma_2^\infty \right) \Phi_2 \right) \Phi_1^2 \ln \gamma_1 = \left( \ln \gamma_1^\infty + 2 \left( \ln \gamma_2^\infty - \ln \gamma_1^\infty \right) \Phi_1 \right) \Phi_2^2 where \Phi_i= \frac{x_i \nu_i}{\sum_j \nu_j x_j} is the volume fraction and x_i the mole fraction of compound i. The activity coefficient of the solvent is calculated with same equations, but interchanging indices 1 and 2. ==Model parameters== The model uses five component specific properties to characterize the interaction forces between a solute and its solvent. Some of these properties are derived from other known component properties and some are fitted to experimental data obtained from data banks. === Acidity and basicity parameters=== These parameters describe the effects of hydrogen-bonding during solving and association. ==Further reading== Online Calculation of limiting activity coefficients with MOSCED Desktop Application for MOSCED property calculations. https://sites.google.com/view/mosced

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