"In 1774, Scheele obtained a yellow gas by digesting marine acid with manganese (manganese dioxide). As Scheele supposed that the manganese withdrew phlogiston from the acid, he called the new gas dephlogisticated marine acid. When, at a later time, phlogiston was regarded by some chemists as identical with hydrogen, Scheele's view of the relation between the compositions of marine acid and the gas he obtained by the reaction of that acid with manganese oxide was interpreted to mean that the gas was produced by removing hydrogen from the acid. In accordance with his conception of the composition of acids, Lavoisier regarded muriatic acid to be a compound of oxygen; and in order to trace a likeness between the supposed composition of this acid and the compositions of other acids, he asserted that muriatic acid is formed by the union of oxygen with a hypothetical substance which he named radical muriatique. Lavoisier described the reaction between muriatic acid and manganese oxide as an oxidation of the acid; he said that the addition of a second dose of oxygen made the acid more volatile, but less acidic. He named Scheele's yellow gas acide muriatique oxygéné."