Calcium hypochlorite
It represents a white dry powder with a sharp chlorine odor. When in contact with air, calcium hypochlorite easily decomposes; it must be stored in closed packaging and in darkness. Solutions of calcium hypochlorite lose their activity during storage, so they should be prepared no more than six days in advance. Periodically, the activity of calcium hypochlorite is determined, which is expressed as a percentage of active chlorine. Calcium hypochlorite containing not less than 15% active chlorine is suitable for disinfection.
Source: "Sanitary Rules for Margarine Industry Enterprises" (approved by the Chief State Sanitary Doctor of the USSR on December 30, 1971 No. 946-А-71)