Iron(III) sulfate

Iron(III) sulfate, is a compund of Iron and sulfate (made of sulfur and oxygen atoms). The compound is different from the more common Iron(II) sulfate in that the ratio of sulfate ions to iron ions is larger.

Usually yellow, it is a rhombic crystalline salt and soluble in water at room temperature. It is used in dyeing as a mordant, and as a coagulant for industrial wastes. It is also used in pigments, and in pickling baths for aluminum and steel. Medically it is used as an astringent and styptic.

Ferric sulfate is produced on a large scale by reacting sulfuric acid with a hot solution of ferrous sulfate, using an oxidizing agent (such as nitric acid or hydrogen peroxide).

In sewage plants it is used to assist in settling minute particles of untreated sewage in tank water.