a chemical product which appears under the form of greenish or yellow-brown odorless crystals or granules with a saline taste, is soluble in water, and is used as a catalyst (especially for synthetic ammonia), a feed additive, a fertilizer, a flour enrichment, an herbicide, an iron oxide pigment, a reducing agent, a wood preservative, for other iron salts, ferrites, process engraving and for the treatment of water and sewage, an iron salt with a saline taste, usually obtained as greenish crystals of the heptahydrate, which are converted to the white monohydrate above 100°C: used in inks, tanning, water purification, and in the treatment of anaemia, raud(II)hüdroksiidi ja väävelhappe sool