Modern Copper Smelting / being lectures delivered at Birmingham University, greatly extended and adapted and with and introduction on the history, uses and properties of copper.

by Donald M. Levy

Or, combining (i.) and (ii.)—

FeS + 3,O ➡ FeO + SO₂.

This sulphur oxidation is an important source of heat, and in the early stages of roasting, sulphur is seen burning with the familiar blue flame, and the mass becomes red hot; stirring being required to prevent the material from sintering by the heat generated within itself.

The oxidation of the iron generally proceeds further, yielding higher and more stable oxides—

	2FeO + O ➡ Fe2O3.
	3FeO + O ➡ Fe3O4.

The SO₂ in the presence of oxygen and in contact with strongly heated material further tends to form SO₃, which is a powerful oxidising agent, and plays a considerable part in the various oxidising reactions which occur.

Pyrrhottite behaves in much the same way; it may be regarded as consisting of xFeS + a little extra sulphur. It does not roast quite so easily as pyrites, partly on account of physical characteristics, and partly because, in the case of pyrites, the greater amount of excess sulphur which is first driven off, tends to leave the mass more porous and so assists oxidation.

Copper Sulphide.—Its characteristics on oxidation have already been indicated in [Lecture III., p. 36]. It melts easily, often at roasting temperatures, hence careful heating and attention are required when much is present.

The reactions are probably analogous to those of FeS oxidation, in the primary oxidation of the sulphur and the instantaneous oxidation of the nascent copper—

	Cu2S + O2 ➡ (2Cu) + SO2
	(2Cu) + O ➡ Cu2O,