HISTORY OF CHLORINE DIOXIDE

In the very early 1800s, researchers reported independently on a reaction of sulphuric acid with potassium chlorate [Cruickshank 1801; Chenevix 1802]. The yellow gas produced gave indications of the existence of a compound of oxygen and chlorine, which Chenevix called hyper oxygenic muriatic acid. For several years, researchers thought the gas was a mixture of gases rather than a single chemical species [Soubeiran 1831]. 

About a decade later, Sir Humphry Davy gave the name “euchlorine” to a mixture of gases arising from a reaction of various chemicals, including potassium chlorate and hydrochloric acid [Davy 1811]. The name came from the Greek: eu, meaning “very,” and chloros, meaning “green,” describing the gas’s deeper greenish-yellow color compared to chlorine. 

Then in 1815, Davy presented a paper titled “On the Action of Acids on the Salts Usually Called Hyperoxymuriates, and on the Gases Produced from Them,” before the Royal Society of London [Davy 1815]. In this, he described experiments determining the nature of the yellow gas. He wrote: 

“…and it appears reasonable to conclude that the deep yellow gas is in reality composed of two volumes of oxygen and one of chlorine, condensed into the space of two volumes…” 

This statement credited Davy with the discovery of chlorine dioxide. 

In 1814, Davy also produced the gas by pouring sulphuric acid (H₂SO₄) on potassium chlorate (KClO₃), later replacing sulphuric acid with hypochlorous acid (HOCl). This reaction was later scaled using sodium chlorate (NaClO₃), yielding: 

2NaClO3 + 4HCl ® 2ClO2 + Cl2 + 2NaCl + 2H2O. 

In 1816, von Stadion independently discovered the same gas, naming it “deutoxide of chlorine” [von Stadion 1816]. Many early researchers working with chlorates and acids

noted the gas’s instability, as small explosions frequently shattered glassware [Jacquelain 1825; Soubeiran 1831; Davy 1834; von Mons 1835; Millon 1843]. 

In 1843, Millon reported the reaction of potassium chlorate with hydrochloric acid to produce a green-yellow gas. Absorbed in an alkaline solution, this yielded chlorite and chlorate. The gas was later referred to as “Millon’s gas.” 

In 1858, Calvert and Davies discovered a new method of producing “peroxide of chlorine” by heating potassium chlorate with oxalic acid. By 1875, Pebal showed that euchlorine was a mixture of chlorine dioxide and chlorine, confirmed independently in 1881 by Garzarolli-Thurnlackh. 

Today, chlorine dioxide is widely used in: