Copper(II) sulfate, also known as cupric sulfate, copper sulfate, blue vitriol, or bluestone, is a chemical compound. Its chemical formula is CuSO. It contains copper in its +2 oxidation state. It also contains sulfate ions. It is a blue solid that can kill fungi. It is also used to purify copper metal. It is common in chemistry sets and chemistry demonstrations, and practical lessons at high school.