Trioctylphosphine oxide (TOPO), tributyl phosphate (TBP) and equimolar TOPO/TBP were used, each as a 0.1 M solution in toluene, to extract Fe from aq. 4.40, 10.87, and 19.3-g/L FeCl3, solutions ([Cl] kept fixed at 5 M). TOPO extracted 8-10 and 100-350 times as much Fe as did TOPO/TBP and TBP, resp. The Fe extracted rose with the Fe concentration in the aq. phase, except for TOPO which extracted max. Fe already from the leanest Fe solution. With TBP in toluene and stirring applied, 50-160 rpm, extraction rate was directly related to stirring speed. At 120 rpm, with TOPO and toluene, the Fe extracted was directly related to extraction time (0-40 min) and the extraction rate rose with the increasing FeCl3 concentration, 0. 70, 0.96 and 1.14 g/(m(2).min). TBP as co-extractant suppressed the rate to 1/10(th) of the TOPO rate. Equilibrium interfacial tensions (gamma) measured in octane as the org. phase, showed gamma to be reduced in the ascending order., TBP < TOPO+TBP < TOM With TOPO/TBP, the molecules adsorbed at the interface monolayer were 1:3.