Chlorine dioxide was discovered in 1814 by Sir Humphrey Davy. He produced the gas by pouring sulphuric acid (H2SO3) on potassium chlorate (KClO3). Than he replaced sulphuric acid by hypochlorous acid (HOCl).
Read more: http://www.lenntech.com/processes/disinfection/chemical/disinfectants-chlorine-dioxide.htm#ixzz4Jrv67tWg