Copper II sulphate water 5 on watch glass. Copper II sulfate pentahydrate fine powder; CuSO4?H2O; Molar mass 249.685 g/mol. Also known as copper sulphate, blue vitriol, ??luestone, vitriol of copper, ??oman vitriol, It is an inorganic compound, exothermic as it dissolves in water. It is used as a fungicide. in the laboratory it is a component of Fehling's and??enedict's solutions??o test for??educing sugars. In a??iuret reagent??t is used to test for proteins. Heating will convert it to its grey/white anhydrous state and adding water to anhydrous powder will convert it back to pentahydrate. There are several methods to grow large copper sulphate crystals.