Ferrous sulphate is a pale green crystalline solid that is highly soluble in water, with a melting point of approximately 64 °C (heptahydrate). It is typically manufactured as a byproduct of steel pickling or by reacting iron with diluted sulphuric acid. In this process, iron is treated with sulphuric acid, producing ferrous sulphate and hydrogen gas. The solution is then filtered to remove impurities, and ferrous sulphate heptahydrate is recovered by cooling, allowing it to crystallize into pale green crystals. It is widely used in water treatment, as a soil conditioner, and in the production of iron-based pigments.