The extration equilibrium of Co(II) from Na2SO4 solution with P538 in kerosene was studied had a mechanism is proposed as follows: Co2+ + 2Na+ + 4(H2A)j(0) = Co(HA)2.(NaHA)2.4(j-1)H2A(0) + 4H+ and Co2+ + 23(H2A)f(0) = Co(HA)2.2(j-1)H2A(0) + 2H+. Equilibrium constants for the reactions are 10-4.70 and 10-1.86, resp.

Key words: COBALT, EXTRACTIVE AGENT, HIGHER ALKANE P, EQUILIBRIUM CONSTANT, PHOSPHORIC ACID ESTER, SODIUM SULFATE, KEROSENE, PHOSPHORIC ACID EXTRACTION, P538