Editing Iron(II) sulfate (section)

==Uses==
Industrially, ferrous sulfate is mainly used as a precursor to other iron compounds. It is a [[reducing agent]], and as such is useful for the reduction of [[Chromate ion|chromate]] in [[cement]] to less toxic Cr(III) compounds. Historically ferrous sulfate was used in the textile industry for centuries as a [[dye fixative]]. It is used historically to blacken leather and as a constituent of [[iron gall ink]].<ref>''British Archaeology'' magazine. http://www.archaeologyuk.org/ba/ba66/feat2.shtml ([https://web.archive.org/web/20141017234401/http://www.archaeologyuk.org/ba/ba66/feat2.shtml archive])</ref> 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===
{{Main|Iron supplement}}

===Plant growth===
Iron(II) sulfate is sold as ferrous sulfate, a soil amendment<ref>{{cite news|url=http://homeguides.sfgate.com/use-ferrous-sulfate-lawns-83484.html|title=Why Use Ferrous Sulfate for Lawns?|access-date=14 April 2018 }}</ref> for lowering the pH of a high alkaline soil so that plants can access the soil's nutrients.<ref>{{cite web|url=https://www.sunset.com/garden/garden-basics/acid-alkaline-soil-modifying-ph|title=Acid or alkaline soil: Modifying pH - Sunset Magazine|website=www.sunset.com|date=3 September 2004|access-date=14 April 2018}}</ref>

In [[horticulture]] it is used for treating iron [[chlorosis]].<ref>Koenig, Rich and Kuhns, Mike: ''Control of Iron Chlorosis in Ornamental and Crop Plants''. ([[Utah State University]], Salt Lake City, August 1996) [http://extension.usu.edu/files/publications/publication/AG-SO-01.pdf p.3]</ref> 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.<ref name=Handreck>{{cite book|last=Handreck|first=Kevin|title=Gardening Down Under: A Guide to Healthier Soils and Plants|publisher=CSIRO Publishing|location=Collingwood, Victoria|year=2002|edition=2nd|pages=146–47|isbn=0-643-06677-2}}</ref> Ferrous sulfate can be used as a [[lawn]] conditioner.<ref name=Handreck/> It can also be used to eliminate [[Bryum argenteum|silvery thread moss]] in golf course putting greens.<ref>[https://www.gcsaa.org/docs/default-source/research-and-information/weeds/controlling-moss-in-putting-greens.pdf#page=2/ Controlling moss in putting greens by Cook, Tom; McDonald, Brian; and Merrifield, Kathy.]</ref>

===Pigment and craft===
Ferrous sulfate can be used to stain concrete and some limestones and sandstones a yellowish rust color.<ref name="concrete1">[http://www.stainedfloor.com/Iron_Recipes.html How To Stain Concrete with Iron Sulfate]</ref>

[[Woodworker]]s use ferrous sulfate solutions to color [[maple]] wood a silvery hue.

Green vitriol is also a useful reagent in the identification of mushrooms.<ref name="Svrček">{{cite book|last=Svrček|first=Mirko|title=A color guide to familiar mushrooms.|publisher=Octopus Books|location=London|year=1975|edition=2nd|page=[https://archive.org/details/colourguidetofam00svrc/page/30 30]|isbn=0-7064-0448-3|url=https://archive.org/details/colourguidetofam00svrc/page/30}}</ref>

===Historical uses===
Ferrous sulfate was used in the manufacture of [[ink]]s, 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]] ({{circa|588–586&nbsp;BCE}}) showed the possible presence of iron.<ref>Torczyner, ''Lachish Letters'', pp.&nbsp;188–95</ref> It is thought that oak galls and copperas may have been used in making the ink on those letters.<ref>Hyatt, ''The Interpreter's Bible'', 1951, volume V, p. 1067</ref> It also finds use in [[wool]] [[dye]]ing as a [[mordant]]. [[Harewood (material)|Harewood]], a material used in [[marquetry]] and [[parquetry]] since the 17th century, is also made using ferrous sulfate.

Two different methods for the direct application of [[indigo dye]] were developed in England in the 18th century and remained in use well into the 19th century. One of these, known as ''china blue'', involved iron(II) sulfate. After printing an insoluble form of indigo onto the fabric, the indigo was reduced to ''leuco''-indigo in a sequence of baths of ferrous sulfate (with reoxidation to indigo in air between immersions). The china blue process could make sharp designs, but it could not produce the dark hues of other methods.

In the second half of the 1850s ferrous sulfate was used as a photographic developer for [[collodion process]] images.<ref>{{cite book |last1=Brothers |first1=Alfred |title=Photography: its history, processes |url=https://archive.org/details/b24886853 |date=1892 |publisher=Griffin |location=London |oclc=558063884 |page=[https://archive.org/details/b24886853/page/257 257]}}</ref>