catalyst

in solvent extraction
https://doi.org/10.1351/goldbook.C00877
A substance included in the solvent to increase the rate of transfer without affecting the position of equilibrium. The term accelerator may also be used but @K03408@ is not recommended.
Source:
PAC, 1993, 65, 2373. (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2380 [Terms] [Paper]