Ores and minerals: Commonly occurring ores and minerals of
Extractive metallurgy: Chemical principles and reactions only (industrial details excluded);
Carbon reduction method (iron and tin);
Self reduction method (copper and lead);
Electrolytic reduction method (magnesium and aluminium);
Cyanide process (silver and gold).
Ores and minerals of iron
Haematite is the principal ore.
Ores and minerals of Tin
Ores and minerals of Copper
Cuprite or ruby copper
Minerals of Lead
Minerals of Magnesium
Minerals of Alumium
Feldspar, Mica, Kaolinite
Alunite or Alumstone
Aluminates of Magensium, Iron and Manganese
Minerals of Silver
Minerals of Zinc
(from X book by Viraf Dalal)
Minerals of Gold
Mainly native gold
The reduction of the ore
At the high temperature at the bottom of the furnace, carbon dioxide reacts with carbon to produce carbon monoxide.
It is the carbon monoxide which is the main reducing agent in the furnace.
Extraction of Tin
The ore is tin stone that contains 10% of the metal as SnO2.
SnO2 + 2C = Sn + 2CO
The moltenmetal is collected from the bottom of the blast furnace.
The metal may be purified elctrolytically
The concentrated ore is heated strongly with silicon dioxide (silica) and air or oxygen in a furnace or series of furnaces.
Electrolysis of magnesium
• Dolomite and seawater is precipitated
as insoluble magnesium hydroxide
Mg(OH)2 which is subsequently treated
with HCl to give MgCl2.
• MgCl2 is fed into electrolysis cell to
produce Mg metal at cathode and Cl2
Conversion of the aluminium oxide into aluminium by electrolysis
The aluminium oxide is electrolysed in solution in molten cryolite, Na3AlF6. Cryolite is another aluminium ore, but is rare and expensive, and most is now made chemically.
It is now the most important and widely used process for extracting gold from ores.
The ore is first finely ground and concentrated by flotation.
To remove certain impurities, it may be roasted.
It is then mixed with a dilute solution of sodium cyanide (or potassium or calcium cyanide) while air is bubbled through it.
Soluble aurocyanide complex ion, Au(CN)-2^-1 is formed .
Silver, usually present as an impurity, also forms a similar soluble ion.