Ferrous sulfate (copperas or iron sulfate) is popularly used to precipitate dissolved scrap gold out of an aqua regia solution. Use about 2 tablespoons of ferrous sulfate for every ounce of dissolved scrap metal in solution. Other uses include sewage treatment, fertilizers, feed additives, reducing agent, wood preservatives and process engraving. Appears as loose, greenish or yellow-brown, odorless crystals. Soluble in water, insoluble in alcohol.
Used in the following patina formulas:
