Historically known by the names blue vitriol, bluestone, or vitriol of copper, cupric sulfate is an inorganic compound whose crystalline salt form is bright blue in color. Dissolving exothermically in water, it produces a copper polymer that is octahedral in nature and bound to no less than four water ligands. Cupric sulfate is manufactured via a process of treating copper metal with a heated concentration of sulfuric acid. Commercial grades are considered to be any cupric sulfate with a purity at or above 98% copper sulfate with very small trace quantities of water.. Cupric sulfate is primarily used in fungicides, generally when combined with slaked lime and applied to grapes, melons, and various species of berries to prevent the plant from being overrun by fungus. It is also a key component in Cheshunt compound, which is a combination of copper sulfate and ammonium carbonate. This compound is used in horticultural settings to prevent damping off in seedlings.