Oxides

Oxides. The term oxyde was first introduced by the great French chemist Lavoisier to indicate compounds which consisted of oxygen united to some other element. With the exception of fluorine, all elements form oxides, which differ greatly in their physical and chemical characteristics. Many elements also form more than one oxide, and the different compounds with the same element are distinguished by prefixes - as wtwoxide, dioxide, suboxide, etc. Some of these compounds are gaseous, as the oxides of carbon, and sulphur-dioxide; some are liquid - e.g. water - but by far the greatest number are solid bodies. Many of the oxides of the metals occur naturally and form important ores, as the oxides of iron, or of manganese. Some of the oxides are soluble, and may give rise to either acid or alkaline solutions. Thus oxides of chromium and of sulphur form powerful bases; those of potassium and sodium are strongly alkaline. Many of the insoluble oxides dissolve in acids to form salts, the oxides being termed basic oxides; others dissolve in and neutralise alkalies, and so play the part of acid oxides. Some oxides, as alumina, can act either as an acid or as a base, forming aluminium salts and aluminates. All acts of combustion, either rapid or slow, which take place in air or in oxygen consist of the union of the burning substance with the oxygen of the air and the formation of a corresponding oxide. [Oxygen, Combustion.]