Abstract: In the known process of preparing a slurry of calcium hypochlorite by reaction of chlorine with a slurry of calcium hydroxide and sodium hydroxide, we provide the improvement consisting of continuously pumping into a first stirred reactor an aqueous slurry of calcium hydroxide and sodium hydroxide optionally partially chlorinated and simultaneously passing chlorine gas into the reaction mixture at such a rate that the redox potential is in the range from 650-850 mV and allowing the contents of the first reactor to overflow continuously into a second stirred reactor and simultaneously passing chlorine gas into the second reactor at such a rate that the redox potential is in the range from 750-950 mV and allowing the contents of the second reactor to overflow and be removed as product; the temperature of the contents of the first and second reactor are independently maintained at a temperature in the range 15.degree. to 35.degree.C.