Blue Vitriol

Cupric sulfate or copper sulphate is the chemical compound with the chemical formula CuSO4. This salt exists as a series of compounds that differ in their degree of hydration.

The anhydrous form is a pale green or gray-white powder, whereas the pentahydrate (CuSO4·5H2O), the most commonly encountered salt, is bright blue. CuSO4·5H2O is in a shade of blue, and very toxic to the environment, irritating to the eyes and skin, and also can be harmful if swallowed.

Copper sulfate pentahydrate is a fungicide. However; some fungi are capable of adapting to elevated levels of copper ions.

Mixed with lime it is called Bordeaux mixture and used to control fungus on grapes, melons, and other berries.