Whose work first revealed that iodine is a chemical element, not a compound?

Bernard Courtois discovered iodine accidentally in 1811 during the manufacture of saltpeter from seaweed ash. He noticed unusual violet vapor when the material was heated and recognized that it came from a new substance. Iodine was later shown to be a distinct element and was named for its violet color. Its discovery helped expand the halogen family and improved understanding of chemical elements. Iodine later became essential in medicine, nutrition, and disinfection.