Explanatory notes
… with other elements more than 10 % by weight of copper, not usefully malleable and commonly used as an additive in the … necessary to drive off excess sulphur and smelted in a furnace to produce copper matte or regulus. In some cases … to produce fire‑refined copper and, where required, may be further refined by electrolysis. For oxide ores and also for …Legal note
… with other elements more than 10 % by weight of copper, not usefully malleable and commonly used as an additive in the …