so that the sodium sulfate component of the feed solution 38 is a dead load cycling between the cell 40 and the chlorine dioxide generator 12 oxygen is vented from the anode compartment 44 by line 56 alternatively the product stream may be recycled by line 58 with oxygen being vented from a gas liquid separator 60 by line 62 wherein recycle of anolyte is required to achieve the desired acid normality of the acidified solution 54 the sodium hydroxide produced in the cathode compartment 46 is recycled by line 64 through a gas liquid separator 66 from which hydrogen is vented by line 68 until the desired concentration of sodium hydroxide solution is achieved the resulting aqueous sodium hydroxide solution is removed as an aqueous product stream in line 70 this solution has considerable utility in a pulp mill particularly as a chemical employed in the purifying and bleaching operations effected in the bleach plant of the pulp mill the gaseous by products namely hydrogen and oxygen also can be utilized in the pulp mill high current efficiency for the electrolytic process effected in the cell 40 as described above can be attributed to the high na h molar ratio in the anode compartment 44 and also to the buffering effect of so 4 2 ions towards hydrogen ions.