Abstract: In this paper the extraction equilibria of scandium(Ⅲ) and sulphu- ric acid extracted by H(DEHP) in n-heptane from sulphuric acid aqueous medium is studied. Extraction mechanisms of scandium (Ⅲ) and sulphuric acid under different concentrations of sulphuric acid in the aqueous phase are proposed through IR and NMR measurements and saturation extraction study. The effect of temperature on extraction equilibria is (?) and the thermodynamic functions of the extraction reactions are calculated.