Copper(II) sulfate pentahydrate is a sulfate salt of copper. It is a potent emetic and is used as an antidote for poisoning by phosphorus. It also can be used to prevent the growth of algae. Physical Description: Blue crystalline granules. Melting point 110°C (with decomposition). Non-combustible. Nauseating metallic taste. Odorless. White when dehydrated.