How did Sir Humphry Davy show that chlorine was a chemical element?

Sir Humphry Davy demonstrated that chlorine was a chemical element by conducting experiments specifically designed to isolate oxygen from the substance, all of which failed.1

At the time, many scientists believed the gas—then known as "oxymuriatic acid"—contained oxygen, consistent with Antoine Lavoisier’s theory that all acids required oxygen. By proving that oxygen could not be extracted from the gas, Davy showed that the earlier name was untenable and established that chlorine was, in fact, a distinct chemical element. His work further clarified the relationship between chlorine and hydrochloric acid, effectively overturning the prevailing chemical theories of the era.12