### Mixed Solvent Electrolyte (MSE)

### Thermodynamic Model

The Mixed-Solvent Electrolyte (MSE) model is an advanced excess free energy theory that expands the prediction range for solutions containing electrolytes and non-electrolytes. MSE is the product of theoretical advances made from strong-electrolyte theories. The result of this advancement is elimination of the ionic strength limits and the requirements that the continuous solvent phase is water. Now, calculations are possible when the process is a wet salt or when the solvent is an acid, alcohol or other material.

MSE is now the model of choice where extreme compositions or conditions are encountered, and is critical when modelling the following systems:

### Mixed Solvent Electrolyte contructs

### Speciation

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Speciation, including ion pair and complex formation, is quantiﬁed using chemical equilibrium equations.The intrinsic equilibrium constants are calculated using the Helgeson-Kirkham-Flowers-Tanger equation of state. This equation accurately quantiﬁes the standard-state thermodynamic properties as functions of temperature and pressure. In its implemented form, this equation of state reproduces standard-state properties up to 1000 C and 5 kbar.

To predict speciation in organic or mixed-solvent electrolyte solutions,the aqueous standard-state properties are combined with Gibbs energies of transfer between aqueous and non aqueous environments.

### Transport and interfacial properties

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MSE contains sub-models to calculate viscosity, electrical conductivity,self-diﬀusivity,thermal conductivity, and surface and interfacial tension

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### Validation materials

OLI has extensive Excel-based validation plots for solutions that MSE model parameters have been established. These plots are available to clients upon request.