Main composition is calcium hypochlorite bleaching powder, calcium hypochlorite with hundreds of CO₂ and water vapor in the air to generate hypochlorous acid and calcium carbonate (the reaction degree 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 (known as acid or salt), then failed.

Step 1: Ca(ClO)₂+H₂O+CO₂===CaCO₃↓+2HClO

Step 2:2HCLO===2HCl+O₂↑ exactly this step deactivates the bleaching powder

Industrial bleaching powder is chlorine gas with Ca(OH)₂?

(rewrites the equation)

2Ca(OH)₂+2Cl₂=CaCl₂+Ca(ClO)₂+2H2O

The bleach ingredient is

CaCl₂· Ca (ClO) ₂

1. Equation of bleaching powder's failure in air

Ca(ClO)₂+CO₂+H₂O=CaCO₃(sediment)+2HClO

2. Equation of excess CO₂ into the bleach solution

Ca(ClO)₂+2CO₂+2H₂O=Ca(HCO₃)₂+2HClO

3. Add dilute hydrochloric acid to the bleach solution

Ca(ClO)₂+2HCl(diluent)=CaCl₂+2HClO

After the test found that bleaching powder powder powder open storage, the content of the effective component of chlorine will change, under normal circumstances, effective loss of chlorine within 9 days should reach more than 50%, after 18 days, basically has no disinfection effect.