$25.$ The $\_$ coefficient model is an advanced approach for predicting phase equilibria in mixtures with non$-$ideal behavior.

$26.$ In the limit of low concentrations, the fugacity of a solute in a solution approaches its $\_$ pressure.

$27.$ The $\_$ method involves graphically determining the interaction parameters for the Margules or Van Laar equations.

$28.$ Non$-$linear regression analysis is often used for the $\_$ determination of interaction parameters in thermodynamic models.