In the ancient times a common compound of chlorine and sodium chloride was used. Jan Baptist van Helmont who was the Belgian chemist and physician recognized chlorine as a gas around 1630.
In the year 1774, Swedish chemist, Carl Wilhelm Scheele is credited with the discovery of chlorine. He first prepared and studied the elemental chlorine. Sir Humphry Davy came with a conclusion that Chlorine was an element and not a compound in the year 1810 after trying with the same experiment of Carl Wilhelm.