AbstractAn experimental investigation has been made of the regeneration of phenol and caustic soda simultaneously by the electrolysis of aqueous sodium phenoxide in a cell using a cation exchange membrane as diaphragm. Current efficiencies close to 100% for both anodic and cathodic processes have been obtained for short periods of electrolysis but with prolonged operation considerable inefficiency arises due to adsorption and oxidation of phenol and loss of ion selectivity of the diaphragm. The presence of solid manganese dioxide in the electrolyte has been found to be useful in partially inhibiting the adsorption or oxidation of phenol at the anode.