Extraction of lactic acid from its aqueous solution was carried out at 30.0°C in a mixed solvent electrolyte system containing water, 1-butanol and ammonium sulfate ((NH 4 ) 2 SO 4 ). The salt appeared to reduce mutual solubility between water and 1-butanol leading to an enlarged two-phase region of the mixture. The effect was more pronounced at high salt concentration. In view of extraction, ternary mixture containing water, 1-butanol and lactic acid, (NH 4 ) 2 SO 4 effectively salted-out 1-butanol and lactic acid leading to a reduced concentration of these two components in the aqueous phase. Distribution coefficient and degree of lactic acid extraction were significantly improved with increasing concentration of the salt. Additionally, (NH 4 ) 2 SO 4 helped lessen the transfer of one solvent into the other, which is the problem normally encountered in extraction when partially miscible solvents are employed. It also advantageously allowed the extraction to be carried out at a high solvent-to-aqueous phase volume ratio, where large recovery of the acid was achieved. Extraction of lactic acid in this mixed solvent electrolyte system could be further improved by operating it in a stage-wise mode rather than a batch one.