Koppel–Palm solvent parameters

Parameters to measure separately the ability of a solvent to enter into non-specific solvent–solute interactions (permittivity ɛ and refractive index η D) and specific solvent–solute interaction (solvent basicity or nucleophilicity B and solvent acidity or electrophilicity E) as contributing to overall solvent polarity.
PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1134 (https://doi.org/10.1351/pac199466051077)