ABSTRACT
This chapter discusses the chemistry of iron oxides, hydroxides, and carbonates together with the research conducted towards the understanding of the mechanism of reduction. Iron ores of sedimentary origin account for nearly 80% of the world's reserves; the remaining 20% is of magmatic origin such as magnetite. Limonite is a geologic term signifying certain deposits of hydrated iron oxides which vary in color from brown to yellow. It is formed by the weathering and alteration of other iron-bearing compounds. The reduction of iron oxide ores takes place at an appreciable rate only at temperatures above 900°C. Ferric oxide, Fe2O3, is generally reduced with a higher velocity than Fe3O4. Swelling is due to the formation of whiskers which in turn is related to the phenomena of nucleation and crystal growth. Shrinkage is due to volume change when the oxide is reduced to metal as well as due to sintering.
