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How is chlorine used to make bleaching powder?

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A labeled diagram of the chlorine element from the periodic table shows its atomic number 17, symbol Cl, electron configuration, and atomic weight range. The box is shaded green to indicate chlorine is a halogen, with icons for orthorhombic crystal structure, gas state at room temperature, and strong acidity. A key explains the icons and colors used. — chlorine Properties of chlorine.

Bleaching powder is produced by reacting chlorine gas with slaked lime.1

In the industrial manufacturing process, this is typically achieved in one of two ways:
* Slaked lime is spread across the floors of large rectangular chambers made of lead or concrete and then exposed to chlorine gas.1
* Alternatively, lime is propelled through horizontal tubes that are continuously fed with the gas.1

Introduced in 1799 by Charles Tennant, this solid compound—which consists primarily of calcium hydroxide, calcium chloride, and calcium hypochlorite—offered a more stable and easily transportable alternative to using chlorine gas directly for bleaching textiles and paper. While it served as the standard bleaching agent for over a century, it was eventually replaced in the 1920s by liquefied chlorine and sodium hypochlorite solutions.12