Copper(II) sulfate, also known as cupric sulfate, or copper sulphate, is the inorganic compound with the chemical formula CuSO4.xH2O, where x can range from 0 to 5. The pentahydrate (x = 5) is the most common form. Older names for this compound include blue vitriol, bluestone, vitriol of copper and Roman vitriol.
The pentahydrate (CuSO4.5H2O), the most commonly encountered salt, is bright blue.