PROPERTIES OF ORES USED IN MAKING CAST IRON.
A brief description of elements in ores will point out varying qualities in the material from which cast iron is made, and also help impress one with the great difference ores can and do make in the different brands of iron. The ores from which cast iron is made are largely oxides of iron, containing other elements and impurities, among which generally exist more or less manganese, sulphur, phosphorus, alumina, and silica. It is called '' rich ore '' when high in iron, and '' lean ore,'' when low. The oxides of iron are known as '' ferric oxide '' and '' ferrous oxide.'' The former, theoretically, contains 70 per cent of iron and 30 per cent of oxygen, the latter 77.78 per cent of iron and 22.22 per cent oxygen. Percentages of iron and oxygen vary in these ores, but the above percentages are generally recognized as constituting distinct proportions in defining their composition.
Many soils and rocks contain more or less oxide of iron, but such material is not generally considered suitable to make cast iron unless it contains more than 30 per cent of iron. Ores are now very rarely used for making cast iron or pig metal unless they contain more than. 40 per cent of iron. The ore used in the manu-as, see " American Foundry Practice " and " Moulder's Text Book."g coke in cupolas it is very important to note > \^f