A single-chamber, filtration press-type poly(methyl methacrylate) flow electrolyzer (Fig. 1) equipped with a (TiOx + RuOx)-activated Ti sheet [Ti/(TiOx + RuOx)] anode, (i) an electrolytic Cu, (ii) an Ag-coated (70 mum) Cu [Cu/Ag], or (iii) a (Pt+Ir)-on-Ag coated Cu [Cu/Ag/(Pt+Ir)] cathode, and a foamed or a woven PVC or a glass-roving diaphragm, was used to electrolyze (60degreesC) waste similar to22% HCl at flow rates (V-o) of 0.23, 0.49, or 0.72 L/h and current densities (j) 5, 10,..., 35 A/dm(2). The electrodes were 90 x 180 mm in size (0.7 dm(2) in active area). The effluent was sampled every 15 min until 3 subsequent outlet acid concentrations (C) were constant. Clamp voltage was recorded, electrode gases were washed, anode gas was Or-sat-analyzed, Cl-2 was determined, and current efficiency and unit power consumption (Z(j)) were evaluated. To establish corrosion resistance, the diaphragm material was boiled for 40, 80 and 120 h in aq. 22% HCl; the electrodes were weighed before and after each series of runs (Table 1). Decomposition voltages (DeltaE(R),) (vs. NCE, with Pt as auxiliary electrode) were determined at HCl concentrations of 20-280 g/L (Table 2). With each cathode and diaphragm, the current vs. voltage relationships were linear. The overall process resistance was believed to be due to diaphragm resistance, electrolyte layer resistance and gas holdup. Over the experimental j-range, Cl-2 in anode gas remained unrelated to j (the gas was believed to contain only H2O, HCl and H-2). With pressed PE as diaphragm, Cl-2 was as pure as 97-99%. Glass roving was found to dissolve in pure HCl at elevated temperatures; it was inefficient as a separation of the electrode spaces. HCl conversion (alpha) was related neither to process temperature nor V-o nor electrode material. High j and low V-o resulted in high a (Fig. 7). With cathodes (ii) and (iii), Z(j) was resp. maximum and minimum; cathode (ii) was most resistant, but its overpotential to evolution of H-2 was high; cathode (i) was too liable to corrosion. The Ti/(TiOx + RuOx) resisted the process conditions and is worth studying. The effluent concentration, always similar to11%, and no decomposition of H2O at 60degreesC, indicate that input HCl concentrations could be even lower than 20%.