manganese

Hard, brittle, grey-white metallic element, atomic number 25, relative atomic mass 54.9380. It resembles iron (and rusts), but it is not magnetic and is softer. It is used chiefly in making steel alloys, also alloys with aluminium and copper. It is used in fertilizers, paints, and industrial chemicals. It is a necessary trace element in human nutrition. The name is old, deriving from the French and Latin forms of Magnesia, a mineral-rich region of Italy.

In addition to acting as a bivalent metal forming salts and alloys, manganese also forms the permanganate anion (MnO₄⁻), which can be used in analytical titration, serving as a reactant and as a colour indicator at the same time.