In matters of chemical nomenclature Davy was a great latitudinarian. All that he contended for was that names should be independent of all speculative views, and should rather be derived from some simple and invariable property. It is remarkable, however, that he who invented the happy term “chlorine” should have objected to the word “cyanogen.” At the close of the short paper “On the Prussic Basis and Acid,” in which he first made known the existence of the cyanides of phosphorus and of iodine, he said:-- “I wish M. Gay Lussac could be prevailed upon to give up the inexpressive and difficult names of cyanogen and hydrocyanic acid, and to adopt the simple ones of prussic gas and prussic acid.” By treating the potassium hyper-oxymuriate of Berthollet (potassium chlorate) with hydrochloric acid, a greenish-yellow explosive gas is obtained which Chenevix had referred to as “hyper-oxygenised muriatic acid,” and as indicating the existence of a compound of oxymuriatic gas and oxygen in a separate state. Davy, as we have seen, was at first inclined to doubt the existence of this substance, and to consider the gas as simply chlorine. But on comparing it with chlorine prepared in other ways he perceived a difference; its solution in water was of lemon yellow or orange colour; when treated with mercury it becomes of a brilliant yellow green. It is, moreover, highly explosive, especially when heated, even at the warmth of the hand, when it loses its vivid colour, and is resolved into a mixture of oxygen and chlorine. Metals, arsenic, phosphorus, charcoal, nitric oxide, act upon it in a manner different from that of chlorine. Davy makes use of these differences as a proof of the correctness of his views of the nature of chlorine. “If the power of bodies to burn in oxymuriatic gas depended upon the presence of oxygen, they all ought to burn with much more energy in the new compound; but copper and antimony, and mercury and arsenic and iron and sulphur have no action upon it, till it is decomposed; and they act then according to their relative attractions on the oxygen, or on the oxymuriatic gas. There is a simple experiment which illustrates this idea. Let a glass vessel containing brass foil be exhausted, and the new gas admitted, no action will take place; throw in a little nitrous gas [nitric oxide], a rapid decomposition occurs, and the metal burns with great brilliancy.