Extraction of Hydrochloric Acid by Tri-n-octylamine in Benzene

The equilibria involved in the extraction of HCl by tri-n-octylamine (TOA) in benzene have been investigated as a function of the HC1 and TOA concentrations. Two distinctly different extractions were observed for two different acidity ranges. From the extraction in the low acidity range (<0.001 m HCl), it has been found that two complexes of TOA·HCl and (TOA·HCl)2are formed in the organic phase and that the equilibrium constants for the two reactions, TOA(org)+H+(aq)+Cl−(aq)=TOA·HCl(org) and 2TOA(org)+2H+(aq)+2Cl−(aq)=(TOA·HCl)2(org), are K11=(1.51±0.02)×104 and K22=(2.92±0.07)×109 respectively. For higher concentrations of HCl>3 m, it seems probable that two major complexes of (TOA·HCl)2HCl and (TOA·HCl)3-(HCl)2 besides the monomer and the dimer, and three minor complexes of (TOA·HCl)2(HCl)2, (TOA·HCl)3HCl, and (TOA·HCl)3(HCl)3 are formed in the organic phase.