41b:3 · A sign for magnesia or manganese in eighteenth-century chemistry.
    It was not until the end of the eighteenth century that the Swedish chemist Scheele proved that the named metals were two different elements. Manganese has the atomic number 25 (iron, , has number 26) and occurs in nature as manganese oxide. It is mostly used in alloys with iron to make special steel.
    Magnesia has also been drawn , , and in different times and systems.