Chlorine dioxide was discovered in 1814 by Sir Humphrey Davy. He produced the gas by pouring sulphuric acid (H2SO4) on potassium chlorate (KClO3). Than he replaced sulphuric acid by hypochlorous acid (HOCl). In the last few years this reaction has also been used to produce large quantities of chlorine dioxide. Sodium chlorate (NaClO3) was used instead of potassium chlorate.
2NaClO3 + 4HCl ® 2ClO2 + Cl2 + 2NaCl + 2H2O
