The preparation of sulfuric acid (oil of vitriol) by the distillation of green vitriol (Iron(II) sulfate) has been known for at least 700 years. Medical use
Plant growth
Iron(II) sulfate is sold as ferrous sulfate, a soil amendment for lowering the pH of a high alkaline soil so that plants can access the soils nutrients.In horticulture it is used for treating iron chlorosis. Although not as rapid-acting as ferric EDTA, its effects are longer-lasting. It can be mixed with compost and dug into the soil to create a store which can last for years. Ferrous sulfate can be used as a lawn conditioner. It can also be used to eliminate silvery thread moss in golf course putting greens. Pigment and craft
Ferrous sulfate can be used to stain concrete and some limestones and sandstones a yellowish rust color.Woodworkers use ferrous sulfate solutions to color maple wood a silvery hue. Green vitriol is also a useful reagent in the identification of mushrooms. Historical uses
Ferrous sulfate was used in the manufacture of inks, most notably iron gall ink, which was used from the middle ages until the end of the 18th century. Chemical tests made on the Lachish letters (c. 588–586 BCE) showed the possible presence of iron. It is thought that oak galls and copperas may have been used in making the ink on those letters. It also finds use in wool dyeing as a mordant. Harewood, a material used in marquetry and parquetry since the 17th century, is also made using ferrous sulfate.
For example, it reduces nitric acid to nitrogen monoxide and chlorine to chloride:

6 FeSO4 + 3 H2SO4 + 2 HNO3 → 3 Fe2(SO4)3 + 4 H2O + 2 NO
6 FeSO4 + 3 Cl2 → 2 Fe2(SO4)3 + 2 FeCl3Its mild reducing power is of value in organic synthesis. It is used as the iron catalyst component of Fentons reagent. Ferrous sulfate can be detected by the cerimetric method, which is the official method of the Indian Pharmacopoeia. This method includes the use of ferroin solution showing a red to light green colour change during titration. See also
Iron(III) sulfate (ferric sulfate), the other common simple sulfate of iron. Copper(II) sulfate
Ammonium iron(II) sulfate, also known as Mohrs salt, the common double salt of ammonium sulfate with iron(II) sulfate. Chalcanthum
Ephraim Seehl known as an early manufacturer of Iron(II) sulfate, which he called green vitriol. References
External links

"Ferrous sulfate". Drug Information Portal. U.S. National Library of Medicine.