Calcium hypochlorite exists as a white granular powder and has a
formula of Ca(OCl)2. It has a strong scent of chlorine and the chlorine atoms
are more labile as compared to sodium hypochlorite. It exists in both anhydrous
and hydrated forms, giving a basic aqueous solution.
The basicity of the solution arises from the hydrolysis
reaction, where calcium hypochlorite is broken down into hypochlorous acid and
calcium hydroxide. The basicity outweighs the acidity property since calcium
hydroxide is a strong base and hypochlorous acid is a weak acid.
Calcium hypochlorite is a good chlorine derivatives and it can
release chlorine upon reactions. Calcium hypochlorite can react with carbon
dioxide to form calcium carbonate, releasing dichloride monoxide. Similarly,
calcium hypochlorite can also react with hydrochloric acid to form calcium
chloride, water and gaseous chlorine.
Calcium hypochlorite is manufactured using calcium process,
where chlorine is added to calcium hydroxide, yielding calcium hypochlorite,
calcium chloride and water. However, this method was not very effective and was
soon obsoleted. It was replaced by Sodium process, which accounts for 70% of
the total production of calcium hypochlorite.
Calcium hypochlorite can also be manufactured using sodium
process, where chlorine is added to calcium hydroxide and sodium hydroxide,
yielding calcium hypochlorite, calcium chloride, water and sodium chloride. All
these products (calcium hypochlorite, calcium chloride and water), together
with calcium hydroxide, react and form bleaching powder.
Calcium hypochlorite is an active component in bleaching powder.
It is used to bleach cellulosic fabrics such as cotton and linen. It cannot be
used to bleach wool, nylon and acrylics as these fibers will become yellow in
color due to the formation of chloramines Fabrics bleached with hypochlorite
develop a distinctive chlorine odor.
Disinfectant and cleaning agent
Calcium hypochlorite is used for the disinfection of drinking
water or swimming pool water. Generally it is sold as 68% calcium hypochlorite
combined with calcium chloride and other salts. It is used as a sanitizer in
outdoor swimming pools in combination with a cyanuric acid stabilizer, which
reduces the loss of chlorine due to ultraviolet radiation. The calcium content
hardens the water and tends to clog up some filters; hence, some products
containing calcium hypochlorite also contain anti-scaling agents.
Calcium hypochlorite is used in place of gaseous chlorine and
bleach for purifying drinking water. It is also used for treatment of
wastewater effluents and pool water. Calcium hypochlorite is used to
manufacture chloroform. In addition, calcium hypochlorite is used for
sanitizing food and beverage containers, and equipment used in production of
dairies and hospitals.