41a:5 · The old sign for the planet Mars, , also a sign for iron, became, with a horizontal bar added to it, the sign for a compound of iron and sulphur, ferrohydrosulphate. This sign was used both in alchemy and early chemistry. Placed horizontally, , the sign was at times used to represent the metal magnesium.
    Pointed diagonally upward, as , the sign was used for chalybs, or steel in eighteenth-century chemistry.
    See in Group 41:b for more signs for steel.