Mercury and copper, which belong to the least
reactivity series, are often found in the form of their sulphide ores.
Cinnabar (HgS) is the ore of mercury. Copper glance (Cu2S) is the ore of copper.
Extraction of mercury metal: Cinnabar (HgS) is
first heated in air. This turns HgS [mercury sulphide or cinnabar] into
HgO (mercury oxide); by liberation of sulphur dioxide.
Mercury oxide so obtained is again heated strongly. This reduces mercury oxide to mercury metal.
2HgS + 3O2 ⇨ 2HgO + 2SO2
2HgO ⇨ 2Hg + O2
Extraction of copper metal: Copper glance (Cu2S)
is roasted in the presence of air. Roasting turns copper glance (ore of
copper) into copper (I) oxide. Copper oxide is then heated in the
absence of air. This reduces copper (I) oxide into copper metal.
2Cu2S + 3O2 ⇨ 2Cu2O + 2SO2
2Cu2O + Cu2S ⇨ 6Cu + SO2