Abstract: The extraction method based on the reversible chemical complexation is highly effective and selective for separating polar organic solutes from dilute solutions, and the basicity of the extractant is one of the most important parameters affecting the extraction equilibrium. In this paper, the determination of basicity of Lewis basic extractant and its mixture solvent was first proposed on the basis of extraction behavior of HCl and the appropriate stoichiometric ratio of solute to extractant. The basicities of two Lewis basic chemicals, n-octy-lamine and di-n-butylamine, and some basicity of typical Lewis basic extractant mixture, trioctylamine(TOA)/1-octanol and trialkylphosphine oxide(TRPO)/kerosene, were measured at 25 ℃ by using this me-thod. The results show that this method was more accurate and simple, the basicity of Lewis basic chemicals was in agreement with the values reported in the literature, and the basicity of the mixture solvent depended on the extractant type and concentration.

Key words: Lewis basic extractant, Lewis basic extractant mixture, Basicity, Determination