Ammonium sulfate is an inorganic compound with the chemical formula  (NH₄)₂SO₄ . It is a product of the reaction between sulfuric acid and ammonia, containing 20–21% nitrogen and 24% sulfur. The pure form appears as colorless, transparent crystals in the orthorhombic system. Its aqueous solution is acidic, and it is insoluble in alcohol, acetone, and ammonia water. It has hygroscopic properties, which cause it to solidify into lumps when it absorbs moisture. It is mainly used