An experimental study of inversion has been made with mixer designs similar to those used industrially for metals extraction in mixer-settler equipment. The impellers were fitted with retreat, curved blades. Double-shrouded, centrally located impellers (with and without impeller blades on the shrouds) and a single shrouded bottom located impeller were compared. The impeller diameters were 177 mm. The mixing tank was an unbaffled closed tank of square cross-section (300 x 300 mm). The liquid-liquid systems studied were an aqueous phase containing 1% by weight sodium sulphate and cumene as the organic phase and a system made from cumene/isobutyric acid/1% aqueous sodium sulphate. Phase inversion under well-mixed conditions has been studied by variation of the organic/aqueous input flow ratios to establish the limiting values for stable operation. Phase inversion under poorly mixed conditions has been studied by determination of the minimum power input necessary to maintain an organic-continuous phase.