Manganese was identified as an element by researchers such as Scheele and Bergman, but it was not until 1774, when Gahn was able to isolate it by reducing manganese dioxide using carbon.
Sources of Manganese
Manganese-bearing minerals are quite common, with oxides, silicates and carbonates being the most common. Minerals such as Pyrolusite (MnO2) and Rhodochriste (MnCO3) rank amongst the most common manganese-bearing minerals. In addition to these sources, many large nodules of manganese (containing about 24% manganese) have been found on ocean floors and could provide another source of manganese.
The main sources of manganese come from the former U.S.S.R, Brazil, South Africa, Australia, Gabon and India.
Production of Manganese
Manganese is most commonly produced by the reduction of the oxide with sodium, magnesium or aluminium. Alternatively it can be produced by electrolysis.
Forms of Manganese
Pure manganese exists in four different allotropes. Of these:
• The alpha phase is stable at room temperature.
• The gamma phase which transforms to the alpha phase at room temperature. It is characteristically flexible, soft, easy to cut and can be bent
• Manganese metal is a grey-white metal that resembles iron
• It is harder then iron, but very brittle
• It is chemically reactive
• It decomposes slowly in water
• Becomes ferromagnetic after suitable treatments
Manganese is an important alloying agent.
• In steels, manganese improves the rolling and forging qualities, as well as strength, toughness, stiffness, wear resistance, hardness and hardenability.
• In aluminium and antimony, manganese additions forms highly ferromagnetic compounds, especially in the presence of small amounts of copper.
It can also be used to produce an amethyst colour in glass
Manganese dioxide or pyrolusite is used for:
• To depolarise dry cells
• To decolourise green glass containing iron
• To prepare oxygen and chlorine
• To assist the drying of black paints
Manganese permanganate is a powerful oxidising agent used in:
• Quantitative analysis techniques