In his Bakerian Lecture of 1810, entitled, "On some of the Combinations of Oxymuriatic Gas and Oxygen, and on the Chemical Relations of these Principles," he details a number of experiments for the illustration of this subject, and arrives at the conclusion, that the oxygen in the hyper-oxymuriate of potash is in triple combination with the metal and chlorine. He likewise confirms his views, with regard to the elementary nature of this latter body, by a series of new enquiries, and shows that they are not incompatible with known phenomena:--for instance, Scheele explained the bleaching powers of oxymuriatic gas, by supposing that it destroyed colours by combining with _Phlogiston_. Berthollet[87] considered it as acting by imparting oxygen; Davy now proves that the pure gas is wholly incapable of altering vegetable colours, and that its operation in bleaching entirely depends upon its property of decomposing water, and of thus liberating its oxygen.[88] The experiment by which he demonstrated this fact is so simple and satisfactory, that I shall here relate it. Having filled a glass globe, containing dry powdered muriate of lime, with oxymuriatic gas, he introduced into another globe, also containing muriate of lime, some dry paper tinged with litmus, that had been just heated; by which device the intrusion of moisture was effectually prevented. After some time, this latter globe was exhausted, and then connected with that containing the oxymuriatic gas, and by an appropriate set of stop-cocks, the paper was exposed to the action of the gas thus dried: no change of colour in the test paper took place, and after two days, there was scarcely a perceptible alteration; while some similar paper dried and introduced into the gas, that had not been exposed to muriate of lime, was instantly bleached. [87] Berthollet first applied oxymuriatic acid for the purpose of bleaching, in France; from whence Mr. Watt introduced it into England. [88] Dr. Thomson has more recently explained the operation, by supposing that water is decomposed, and that its hydrogen goes to the chlorine, and its oxygen to the water, forming with the latter a deutoxide of hydrogen, or the oxygenated water of Thénard, which he considers as the true bleaching principle. As an illustration of the eagerness with which he seized upon facts, in order to apply them to economical purposes, it may be stated that, on reflecting upon the theory of bleaching, and on the changes which its agents undergo, he was led to propose the use of a liquor produced by the condensation of oxymuriatic gas in water, containing magnesia diffused through it, as superior to the oxymuriate of lime commonly employed.[89]