41b:10 · This sign stands for blue vitriol, a copper sulphate, one of the most important salts of copper and sulphuric acid. The sign was used by seventeenth-century chemists. See above for a derivation of its graphical structure.
    Compare with the structurally similar below. Note that was one of the signs used by alchemists for sulphur.
    For more information about vitriols and other ways of drawing them, turn to in Group 18.