it was discovered by barnard courtois in 1811. he burned seaweed to get sodium carbonate and reacted the residue with sulfuric acid. one time, he poured too much sulfuric acid on the seaweed and purple vapor came out which made dark blue-black crystals on a cold surface. he did not have enough money to see whether it was a new element or not. he gave samples to several chemists, who identified it as an element in 1813.