modifier

in solvent extraction
https://doi.org/10.1351/goldbook.M03965
A substance added to a solvent to improve its properties e.g. by increasing the @S05740@ of an @E02299@, changing interfacial parameters or reducing adsorption losses. Additives used to enhance @E02301@ rates should be called accelerators or catalysts.
Source:
PAC, 1993, 65, 2373. (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2381 [Terms] [Paper]