Page 40 - Curriculum Visions Dynamic Book

Manganese
Manganese is a grey metal that looks very much like iron. Pure manganese is rarely used because it is hard and brittle. Its main use is as an alloying and purifying metal in the iron and steel industry.
Manganese is more reactive than iron
(it is higher up the reactivity series), so when it is added to a furnace, the iron oxides react with the manganese, removing the oxygen from the iron and adding it to the manganese. Manganese oxide is one of the constituents of slag.
Manganese also reacts with sulphur impurities to form manganese sulphide, which then adds
to the slag.
Manganese can be added to purified iron to make an alloy. The alloy is tougher, yet easier to work into shape, than pure steel. It also gives added corrosion resistance. Manganese steel contains just over one-tenth manganese.
The alloy has the added advantage of being nonmagnetic. Its toughness means that it is used for the buckets and scoops of heavy lifting machinery and many other uses within the construction industry.
When manganese makes the main component of an alloy with nonferrous metals like copper,
it produces metals that expand and contract readily with temperature. As a result they are used in bimetal strips as heat-sensitive switches.
EQUATION: Using manganese to help refine iron
Iron oxide + manganese ➪ manganese oxide + iron Fe2O3(s) + Mn(s) ➪ MnO3(s) + 2Fe(s)
 A Venetian glass vase coloured using compounds of manganese.
Manganese oxide in glass-making
The Venetians were
the first people to use manganese compounds in glass-making. In the Middle Ages they discovered that manganese oxide would oxidise the iron impurities in the glass that gave it
a green or brown tint.
The result was a much clearer, and therefore more popular, glass.
 Garnet is a silicate in which manganese and iron are often important constituents, producing dark red–brown crystals. Garnet is widely regarded as a semiprecious stone.
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