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

(a) To allow of the formation, from the mixture of sulphides and oxides in the roasted materials from the calciners, of a copper matte and a slag.

(b) To maintain such a high temperature as to render these products perfectly fluid, and thus to allow the matte and slag to settle and separate thoroughly.

In spite of the neutral atmosphere, however, the smelting of the roasted materials usually results in a higher concentration than would be expected from the calculation of the sulphur, copper, and iron in the charge. The reason of this is that the smelting operation results in some further elimination of the sulphur, which causes the production of a higher grade matte. This additional elimination of sulphur in the reverberatory furnace smelting of the roasted charge is due to the reactions which take place on melting, between the oxides, sulphates, and sulphides of copper, all of which exist in the products from the roasters. These reactions are expressed by the equations—

Cu₂S + 2Cu₂O ➡ 6Cu + SO₂
Cu₂S + CuSO₄ ➡ 3Cu + 2SO₂,

which indicate a further addition of copper to the matte, and a corresponding loss of sulphur. Thus a typical reverberatory charge of the following composition:—

Silica,	27·2	per cent.
Iron,	31·0	"
Lime,	2·3	"
Sulphur,	8·4	"
Copper,	8·3	"

should theoretically yield, on melting down, a matte running—

[8]Cu (8·3) ➡ Cu2S  10·4				Cu 8·3				Cu 30	per cent.
		=		S 8·4		or		S 30	"
S (8·4−2·1) ➡ FeS  17·6				Fe 11·3				Fe 40	"

In actual practice however, the matte resulting from the reverberatory smelting of the charge had the composition—

	Cu	45	per cent.
	S	27	"
	Fe	28	"