Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as a free element in nature; it is often found in minerals in combination with iron.
Historically, manganese is named for various black minerals (such as pyrolusite) from the same region of Magnesia in Greece which gave names to similar-sounding magnesium, Mg, and magnetite, an ore of the element iron, Fe. By the mid-18th century, Swedish chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine. Scheele and others were aware that pyrolusite (now known to be manganese dioxide) contained a new element, but they were unable to isolate it. Johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon.
Manganese phosphating is used for rust and corrosion prevention on steel. Ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions.
Although manganese metal is almost never used, manganese is an important alloy in the manufacture of stainless steel. Manganese compounds have wide use and manganese dioxide is a common redox media.
Manganese can be removed by water softening resins, provided oxygen is excluded from the water so that manganese remains a divalent cation.
Manganese dioxide is used as a redox media to enhance the oxidation of iron and (soluble) manganese.
Permanganate is used as a disinfectant in potable waters because it produces much lower levels of disinfection by-products than does chlorine or bleach. Permanganate is also used as an oxidant in redox filters for the removal or iron and manganese.