Calcium hypochlorite exists as a white granular powder and has the formula of Ca(OCl)2. It has a strong scent of chlorine but is more stable than chlorine. It exists as 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 derivative and 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 became obsolete. 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. 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 dairy product and hospitals.