Bleaching powder is not used

Bleaching powder is a versatile compound which is made up of chlorine gas is passing through slaked lime.

$\underset{\text{Slaked\hspace{0.17em}\hspace{0.17em}lime}}{\text{Ca}{\left(\text{OH}\right)}_{\text{2}}}+\text{C}{l}_2\to \underset{\text{Bleaching\hspace{0.17em}\hspace{0.17em}powder}}{\text{CaOC}{l}_2}+{\text{H}}_{\text{2}}\text{O}$

Bleaching powder is used in different industries like textile industry,

Manufacture of chloroform and purification of drinking water. 

Hence bleaching powder not used in manufacture of gases.