Iodine was discovered by a French chemist when he was manufacturing potassium nitrate for gunpowder and accidentally added too much acid to potassium carbonate. This resulted in a beautiful violet vapor that condensed into dark, lustrous crystals. It was suspected to be a new element, confirmed by chemists, and named from the Greek word for 'violet'.
A visual chronology of Asimov's ~1500 scientific inventions and discoveries.
