Fe2SO43nH2O

Fe2(SO4)3·nH2O, often written as Fe2SO43nH2O, refers to the ferric sulfate hydrates, a family of compounds in which iron is in the +3 oxidation state and sulfate is the counterion. The general formula Fe2(SO4)3·nH2O covers hydrates with varying numbers of water molecules, depending on crystallization conditions. In practice, these hydrates appear as crystalline solids that are typically pale yellow to tan and may be hygroscopic, losing or absorbing water with changes in humidity and temperature.

Preparation and occurrence: Ferric sulfate hydrates are produced industrially by reacting iron sources (such as iron metal or iron oxides) with sulfuric acid and carefully controlling evaporation or cooling to crystallize the desired hydrate. They can also be obtained by crystallizing ferric sulfate from aqueous solution under specific conditions.

Physical and chemical properties: They are soluble in water to give acidic solutions. In aqueous media, ferric sulfate rapidly hydrolyzes, forming ferric hydroxide and releasing acidity, which can lead to a colloidal or gelatinous ferric hydroxide suspension. On heating, the hydrates decompose, releasing sulfur oxides and leaving iron oxides or basic iron salts.

Applications: The hydrates are widely used as coagulants and flocculants in water and wastewater treatment, helping to remove suspended solids. They have historical and contemporary roles as mordants in dyeing and printing processes and can serve as catalysts or reagents in various chemical syntheses.

Safety: Ferric sulfate hydrates are corrosive and can irritate skin, eyes, and the respiratory tract. They should be handled with appropriate personal protective equipment, stored in a dry place, and kept away from incompatible materials. Contact with moisture can intensify acidity and corrosion.