Copper sulfate, also known as blue alum, with chemical formula CuSO4, is white powder without water, blue powder with water, or light grayish green due to impure. It is a soluble copper salt. The common form of copper sulfate is its crystal. Copper sulfate tetrahydrate ([Cu (H2O) 4] SO4 · H2O, copper sulfate pentahydrate) is a blue solid. Its aqueous solution is blue due to hydrated copper ions, so anhydrous copper sulfate is often used to test the existence of water in the laboratory. In real production and life, copper sulfate is often used to refine refined copper, which can be mixed with hydrated lime to produce pesticide Bordeaux liquid. Copper sulfate is a heavy metal salt, toxic, and the lethal dose for adults is 0.9g/kg. If you eat by mistake, you should immediately eat or drink protein rich foods such as milk and egg white, or use EDTA calcium sodium salt to detoxify. White anhydrous copper sulfate powder is blue after dropping into water