Method of extracting copper values from copper bearing mineral sulphides

Claim 1

IN A METHOD OF PRODUCING COPPER METAL POWDER FROM COPPER BEARING MINERAL SULPHIDES IN WHICH FINELY DIVIDED COPPER BEARING MINERAL SULPHIDES ARE LEACHED WITH A STRONG AQUEOUS AMMONIA LEACH SOLUTION UNDER A PARTIAL PRESSURE OF OXYGEN TO PRODUCE A LEACH SOLUTION WHICH CONTAINS DISSOLVED COPPER VALUES, FREE AMMONIA, AND AT LEAST ONE OXIDIZABLE SULPHUR COMPOUND OF THE GROUP CONSISTING OF POLYTHIONATES AND THIOSULPHATE, UNDISSOLVED RESIDUE IS SEPARATED FROM THE LEACH SOLUTION AND THE CLARIFIED SOLUTION IS REACTED WITH A SULPHUR-FREE REDUCING GAS TO PRECIPITATE COPPER METAL POWDER, THE IMPROVEMENT WHICH COMPRISES THE STEP OF REACTING THE CLARIFIED COPPER BEARING LEACH SOLUTION PRIOR TO REACTING IT WITH A SULPHUR-FREE REDUCING GAS WITH AN OXYGEN BEARING, OXIDIZING GAS FOR A PERIOD OF TIME SUFFICIENT TO CONVERT SUBSTANTIALLY ALL THE OXIDIZABLE SULPHUR COMPOUNDS TO AN OXIDIZED SULFUR COMPOUND OF THE GROUP CONSISTING OF AMMONIUM SULPHATE AND AMMONIUM SULPHAMATE.