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How did chlorine replace sunlight as a major bleaching agent?

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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.

Sunlight was the primary bleaching agent until the discovery of chlorine in 1774 by Karl Wilhelm Scheele and the subsequent demonstration of its bleaching properties by Claude Berthollet in 1785.1

Chlorine replaced sunlight because natural bleaching techniques—which relied on sunlight, rain, sour milk, and urine—were a significant bottleneck for the rapidly growing textile industry, as they required a long time to complete. The modern chemical industry was essentially developed to create more efficient, rapid bleaching methods to meet this industrial demand.2

In 1799, Charles Tennant introduced bleaching powder, a solid combination of chlorine and slaked lime. This innovation allowed for the mass production of a bleaching agent that was easier to handle and ship than chlorine gas, effectively meeting the requirements of the cotton-textile industry. Bleaching powder remained the standard agent until the 1920s, when it was gradually superseded by liquefied chlorine and sodium hypochlorite solutions.12