What is the principle of long-term failure of bleaching powder in air?
Main composition is calcium hypochlorite bleaching powder, calcium hypochlorite with CO2 and water vapor in the air to generate hypochlorous acid and calcium carbonate (the reaction of bleaching powder is in fact the work), if you don't use will be photolysis (long dark also reacts to) produce the oxygen and hydrogen chloride gas (or hydrochloric acid), then failed
The main components of bleaching powder are calcium hypochlorite and calcium chloride, the active component is calcium hypochlorite. The bleaching principle of bleaching powder is the reaction of calcium hypochlorite and acid to produce bleach material hypochlorite:
Hypochlorous acid is a weak acid that can oxidize pigments and thus achieve bleaching purposes.
The effective component of bleaching powder is calcium hypochlorite, and the hypochlorite acid generated by acid has bleaching effect
Failure is hypochlorite calcium acid acid generated hypochlorite, and decomposition.
Ca(ClO)2+CO2+H2O=CaCO3+HClO(Strong acid to weak acid)
Without hypochlorite, of course, it's no longer effective.