Abstract: An improved process is provided for the production of chlorine dioxide and chlorine wherein a chlorine dioxide generator may be operated interchangeably in either sulfuric acid or hydrochloric acid mode without changing acidity levels or evacuating the liquor of one mode and refilling with liquor of the second mode before continuing generation. The versatile process for production of chlorine dioxide comprises maintaining saturated solutions of both alkali metal chloride and alkali metal sulfate in the generator at an acid normality of from about 2 to about 11 in the presence of a small amount of catalyst selected from the group consisting of vanadium pentoxide, silver ions, manganese ions, dichromate ions and arsenic ions. Thus, the instant process provides high yields of chlorine dioxide even at high acidities making it possible to manufacture balanced quantities of saltcake and alkali metal chloride by-products as may be required.