Reflux in Counter-Current Distribution. I. The Acid-Base Process

Abstract

A method for separating weak acids or bases is described based on counter-current distribution between an organic solvent and an aqueous phase containing their salts. The process is carried out in a Craig tube system modified to permit solvent flow in both directions. By means of stripping sections the system is run under total or partial reflux. This process is closely analogous to fractional distillation, each tube being equivalent to two theoretical plates. The separation attainable in such a system at equilibrium and the rate of approach to equilibrium are discussed quantitatively and optimum operating conditions evaluated. As an example the separation of o- and p-toluic acids is described.