Abstract: Calcium hypochlorite is produced by admixing a slurry of lime containing soluble impurities with a saturated calcium hypochlorite solution in a crystallizing zone. An impure slurry of coarse and small dibasic calcium hypochlorite crystals and fine insolubles in a mother liquor is formed and fed to the intermediate section of a separation zone. An aqueous sodium chloride elutriant is fed to the lower section of the separation zone to separate a slurry of fine insolubles, which is conveyed in the elutriant to the upper section of the separation zone, and small crystals of dibasic calcium hypochlorite, which can be recycled to the crystallizing zone or destroyed by chlorination, from the dibasic calcium hypochlorite solution. A slurry of purified coarse dibasic calcium hypochlorite crystals in the elutriant is removed from the lower section of the separation zone at a rate controlled to maintain a rising velocity in the lower section of the separation zone of from about 0.5 to about 7 centimeters per minute.