"Lavoisier believed that oxygen was the essential constituent in every acid and gave the element its name on that account. ... If muriatic acid contains oxygen then oxymuriatic acid (chlorine) must contain still more, but all Davy's attempts to obtain oxygen from it were equally fruitless. ...Numerous chemists who admired Lavoisier and valued a logical system more than experimental evidence, preferred for some time longer to make this assumption, and Gay-Lussac and Thénard were particularly hard to convince. Indeed, they supported the muriaticum theory with some very ingenious experiments. As fate would have it, however, they soon themselves furnished the most satisfactory evidence against the theory. In 1813 Gay-Lussac published a famous paper upon iodine, then recently discovered by Courtois, and in the following year another paper on cyanogen which is equally noteworthy. These investigations involved a study of hydriodic and hydrocyanic acids; and the important analogies which connect these with hydrochloric, together with the certainty that there is no oxygen in hydrocyanic acid soon satisfied all that there was no oxygen in any of them."