Bleaching powder is a mixed salt of hydrochloric acid and hypochlorous acid. It has the formula, ${\mathrm{CaOCl}}_2.{\mathrm{H}}_2\mathrm{O}$ It is manufactured by the action of chlorine on dry slaked lime at $40°C.$ There is also a view that the bleaching powder is a mixture of calcium hypochlorite and basic calcium chloride
$[\mathrm{Ca}{\left(\mathrm{OCl}\right)}_2+{\mathrm{CaCl}}_2.\mathrm{Ca}{\left(\mathrm{OH}\right)}_2.{\mathrm{H}}_2\mathrm{O}]$ 
The amount of chlorine obtained from a sample of bleaching powder by the treatment with excess of dilute acids or ${\mathrm{CO}}_2$ is called available chlorine. A good sample of bleaching powder contains 35-38% of available chlorine. On long amount of available chlorine decreases. The estimation of available chlorine is done volumetrically by iodometric method. In textile industry, the cotton cloth is mainly bleached with the help of bleaching powder.