Britannica Sources used in this answer

How did Humphry Davy explain chlorine’s bleaching action?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

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.

Sir Humphry Davy explained the bleaching action of chlorine by proposing that the gas functions through the liberation of oxygen from water.1

While earlier theories—such as those held by Antoine Lavoisier—incorrectly suggested that all acids contained oxygen, Davy demonstrated that chlorine is a distinct chemical element rather than a compound of oxygen and muriatic acid. By proving that chlorine could not be decomposed to reveal oxygen, he successfully challenged the prevailing chemical theories of his time.1