Regeneration of hydrochloric acid and sodium hydroxide from sodium chloride solution has been carried out by membrane electrolysis where the anode was replaced by a membrane-electrode assembly (MEA). Hydrogen diffusion electrode and a Nafion (R) 117 membrane were assembled tightly in order to prevent platinum poisoning by chloride ions. The use of this electrode to produce H+ may be compared to the use of metallic electrodes where H+ is produced by water oxidation with oxygen evolution. The reversible cell voltage is reduced by 1.23 V. The current efficiency of hydrogen oxidation in the MEA is 100% if, at least, the stoichiometric flow of hydrogen is insured. Acid production is then only limited by H+ leakage through the anion-exchange membrane. The undesirable flux of H+ through this membrane was found proportional to the acid concentration in the anolyte. The value of the rate constant of proton leakage is about 0.080 dm(3) faraday(-1). The current efficiency decreases when acid concentration increases. Water transfer was also studied. Transfer towards the base solution is higher than transfer to the acidic solution. When a current density of 3 kA m(-2) is applied the anodic voltage remains below 300 mV for acid concentration lower than 3 mol dm(-3) and increases notably for higher acid concentrations probably due to poisoning of platinum by chloride ions that leak through the membrane owing to their high concentration in solution. (c) 2006 Elsevier B.V. All rights reserved.