Iron(II) sulfate

{{For|the other sulfate of iron, also named ferric sulfate|Iron(III) sulfate}} {{Use dmy dates|date=February 2024}} {{cs1 config|name-list-style=vanc|display-authors=6}} {{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 396496424 | Name = Iron(II) sulfate | ImageFile1 = Fe(H2O)6SO4.png | ImageClass1 = skin-invert-image | ImageName1 = Skeletal formula of iron(II) sulfate | ImageSize1 = | ImageCaption1 = | ImageFile2 = | ImageClass2 = bg-transparent | ImageName2 = Structure of iron(II) sulfate heptahydrate | ImageSize2 = | IUPACName = Iron(II) sulfate | ImageFile3 = Iron(II)-sulfate-heptahydrate-sample.jpg | ImageName3 = Sample of iron(II) sulfate heptahydrate | ImageSize3 = | OtherNames = Iron(II) sulphate; Ferrous sulfate, Green vitriol, Iron vitriol, Ferrous vitriol, Copperas, Melanterite, Szomolnokite, | Section1 = {{Chembox Identifiers | index_label = anhydrous | index1_label = monohydrate | index2_label = dihydrate | index3_label = heptahydrate | index_comment = | index1_comment = | index2_comment = | index3_comment = | testQID = Q288266 | QID1 = Q27276789 | QID2 = | QID3 = | ChemSpiderID = 22804 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID1 = 56459 | ChemSpiderID1_Ref = {{chemspidercite|changed|chemspider}} | ChemSpiderID3 = 22804 | ChemSpiderID3_Ref = {{chemspidercite|changed|chemspider}} | UNII = 2IDP3X9OUD | UNII_Ref = {{fdacite|correct|FDA}} | UNII1 = RIB00980VW | UNII1_Ref = {{fdacite|correct|FDA}} | UNII2 = G0Z5449449 | UNII2_Ref = {{fdacite|correct|FDA}} | UNII3 = 39R4TAN1VT | UNII3_Ref = {{fdacite|correct|FDA}} | CASNo = 7720-78-7 | CASNo_Ref = {{cascite|correct|CAS}} | CASNo1 = 17375-41-6 | CASNo1_Ref = {{cascite|correct|CAS}} | CASNo2 = 10028-21-4 | CASNo2_Ref = {{cascite|correct|CAS}} | CASNo3 = 7782-63-0 | CASNo3_Ref = {{cascite|correct|CAS}} | PubChem = 24393 | PubChem1 = 62712 | PubChem3 = 62662 | ChEBI = 75832 | ChEBI_Ref = {{ebicite|changed|EBI}} | ChEMBL = 1200830 | ChEMBL_Ref = {{ebicite|changed|EBI}} | RTECS = NO8500000 (anhydrous) NO8510000 (heptahydrate) | EC_number = 231-753-5 | UNNumber = 3077 | SMILES = [Fe+2].[O-]S([O-])(=O)=O | SMILES3 = [OH2+][Fe-4]([OH2+])([OH2+])([OH2+])([OH2+])[OH2+].[O-]S(=O)(=O)[O-].O | InChI = 1/Fe.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 | InChIKey = BAUYGSIQEAFULO-NUQVWONBAS | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/Fe.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = BAUYGSIQEAFULO-UHFFFAOYSA-L}} | Section2 = {{Chembox Properties | Formula = FeSO4 | Appearance = White crystals (anhydrous) White-yellow crystals (monohydrate) Blue-green deliquescent<ref>{{cite journal |last1=Li |first1=Renyuan |last2=Shi |first2=Yusuf |last3=Shi |first3=Le |last4=Alsaedi |first4=Mossab |last5=Wang |first5=Peng |title=Harvesting Water from Air: Using Anhydrous Salt with Sunlight |journal=Environmental Science & Technology |date=1 May 2018 |volume=52 |issue=9 |pages=5398–5406 |doi=10.1021/acs.est.7b06373|doi-access=free |pmid=29608281 |bibcode=2018EnST...52.5398L |hdl=10754/627509 |hdl-access=free }}</ref> crystals (heptahydrate) | Odor = Odorless | Density = 3.65 g/cm3 (anhydrous) 3 g/cm3 (monohydrate) 2.15 g/cm3 (pentahydrate)<ref name=webmin2/> 1.934 g/cm3 (hexahydrate)<ref name=webmin3/> 1.895 g/cm3 (heptahydrate)<ref name=crc/> | MolarMass = 151.91 g/mol (anhydrous) 169.93 g/mol (monohydrate) 241.99 g/mol (pentahydrate) 260.00 g/mol (hexahydrate) 278.02 g/mol (heptahydrate) | MeltingPtC = 680 | MeltingPt_notes = (anhydrous) decomposes<ref name=chemister/> {{convert|300|C|F K}} (monohydrate) decomposes {{convert|60-64|C|F K}} (heptahydrate) decomposes<ref name=crc>{{CRC90}}</ref><ref name=fca/> | BoilingPt = | Solubility = Monohydrate: 44.69 g/100 mL (77 °C) 35.97 g/100 mL (90.1 °C) Heptahydrate: 15.65 g/100 mL (0 °C) 19.986 g/100 mL (10 °C) 29.51 g/100 mL (25 °C) 39.89 g/100 mL (40.1 °C) 51.35 g/100 mL (54 °C)<ref name=sioc/> | SolubleOther = Negligible in alcohol | Solubility1 = 6.38 g/100 g (20 °C)<ref name=chemister>{{cite web|last= Anatolievich|first= Kiper Ruslan|url= http://chemister.ru/Database/properties-en.php?dbid=1&id=4387|title= iron(II) sulfate|access-date= 3 August 2014}}</ref> | Solvent1 = ethylene glycol | RefractIndex = 1.591 (monohydrate)<ref name=mindat/> 1.526–1.528 (21 °C, tetrahydrate)<ref name=webmin/> 1.513–1.515 (pentahydrate)<ref name=webmin2/> 1.468 (hexahydrate)<ref name=webmin3/> 1.471 (heptahydrate)<ref name=webmin4/> | VaporPressure = 1.95 kPa (heptahydrate)<ref name="sigma"/> | MagSus = {{val|1.24|e=-2|u=cm3/mol}} (anhydrous) {{val|1.05|e=-2|u=cm3/mol}} (monohydrate) {{val|1.12|e=-2|u=cm3/mol}} (heptahydrate)<ref name=crc/> {{val|+10200|e=-6|u=cm3/mol}}}} | Section3 = {{Chembox Structure | CrystalStruct = Orthorhombic, oP24 (anhydrous)<ref name=cod>{{cite journal|title= The High-temperature β Modification of Iron(II) Sulfate|first= Matthias|last= Weil|journal= Acta Crystallographica Section E|url= http://www.crystallography.net/2216658.html|publisher= International Union of Crystallography|access-date= 3 August 2014|pages= i192|year= 2007|volume= 63|issue= 12|doi= 10.1107/S160053680705475X|bibcode= 2007AcCrE..63I.192W|url-access= subscription}}</ref> Monoclinic, mS36 (monohydrate)<ref name=mindat/> Monoclinic, mP72 (tetrahydrate)<ref name=webmin/> Triclinic, aP42 (pentahydrate)<ref name=webmin2/> Monoclinic, mS192 (hexahydrate)<ref name=webmin3/> Monoclinic, mP108 (heptahydrate)<ref name=crc/><ref name=webmin4/> | SpaceGroup = Pnma, No. 62 (anhydrous)<ref name=cod/> C2/c, No. 15 (monohydrate, hexahydrate)<ref name=webmin3/><ref name=mindat/> P21/n, No. 14 (tetrahydrate)<ref name=webmin/> P{{overline|1}}, No. 2 (pentahydrate)<ref name=webmin2/> P21/c, No. 14 (heptahydrate)<ref name=webmin4/> | PointGroup = 2/m 2/m 2/m (anhydrous)<ref name=cod/> 2/m (monohydrate, tetrahydrate, hexahydrate, heptahydrate)<ref name=webmin3/><ref name=mindat/><ref name=webmin/><ref name=webmin4/> {{overline|1}} (pentahydrate)<ref name=webmin2/> | LattConst_a = 8.704(2) Å | LattConst_b = 6.801(3) Å | LattConst_c = 4.786(8) Å (293 K, anhydrous)<ref name=cod/> | LattConst_alpha = 90 | Coordination = Octahedral (Fe2+)}} | Section5 = {{Chembox Thermochemistry | DeltaHf = −928.4 kJ/mol (anhydrous)<ref name=crc/> −3016 kJ/mol (heptahydrate)<ref name=chemister2>{{cite web|last= Anatolievich|first= Kiper Ruslan|url= http://chemister.ru/Database/properties-en.php?dbid=1&id=459|title= iron(II) sulfate heptahydrate|access-date= 3 August 2014}}</ref> | Entropy = 107.5 J/mol·K (anhydrous)<ref name=crc/> 409.1 J/mol·K (heptahydrate)<ref name=chemister2/> | HeatCapacity = 100.6 J/mol·K (anhydrous)<ref name=crc/> 394.5 J/mol·K (heptahydrate)<ref name=chemister2/> | DeltaGf = −820.8 kJ/mol (anhydrous)<ref name=crc/> −2512 kJ/mol (heptahydrate)<ref name=chemister2/>}} | Section6 = {{Chembox Pharmacology | Pharmacology_ref = | ATCCode_prefix = B03 | ATCCode_suffix = AA07 | ATC_Supplemental = | ATCvet = | Licence_EU = | INN = | INN_EMA = | Licence_US = | Legal_status = | Legal_AU = | Legal_AU_comment = | Legal_CA = | Legal_CA_comment = | Legal_NZ = | Legal_NZ_comment = | Legal_UK = | Legal_UK_comment = | Legal_US = otc | Legal_US_comment = | Legal_EU = | Legal_EU_comment = | Legal_UN = | Legal_UN_comment = | Pregnancy_category = | Pregnancy_AU = | Pregnancy_AU_comment = | Dependence_liability = none | AdminRoutes = | Bioavail = | ProteinBound = | Metabolism = | Metabolites = | OnsetOfAction = 4 days<ref>{{cite web |title=Ferrous sulfate |url=https://go.drugbank.com/drugs/DB13257 |website=go.drugbank.com |access-date=11 December 2023 }}</ref> | HalfLife = | DurationOfAction = 2-4 months with peak activity at 7-10 days<ref>{{cite web |title=Ferrous sulfate |url=https://go.drugbank.com/drugs/DB13257 |website=go.drugbank.com |access-date=11 December 2023 }}</ref> | Excretion = }} | Section7 = {{Chembox Hazards | GHSPictograms = {{GHS exclamation mark}}<ref name="sigma">{{Sigma-Aldrich|sigma|id = f8263|name = Iron(II) sulfate heptahydrate|accessdate = 3 August 2014}}</ref> | GHSSignalWord = Warning | HPhrases = {{H-phrases|302|315|319}}<ref name="sigma"/> | PPhrases = {{P-phrases|305+351+338}}<ref name="sigma"/> | NFPA-H = 1 | NFPA-F = 0 | NFPA-R = 0 | NFPA_ref = <ref>{{Cite web |url=https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-f/S25325A.pdf |title=Safety Data Sheet |access-date=29 May 2022 |archive-date=11 March 2024 |archive-url=https://web.archive.org/web/20240311145558/https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-f/S25325A.pdf }}</ref> | LD50 = 237 mg/kg (rat, oral)<ref name=fca>{{cite web|title= MSDS of Ferrous sulfate heptahydrate|url= https://www.fishersci.ca/viewmsds.do?catNo=I1463|publisher= Fisher Scientific, Inc|place= Fair Lawn, New Jersey|access-date= 3 August 2014}}</ref> | REL = TWA 1 mg/m3<ref>{{PGCH|0346}}</ref>}} | Section8 = {{Chembox Related | OtherAnions = | OtherCations = Cobalt(II) sulfate Copper(II) sulfate Manganese(II) sulfate Nickel(II) sulfate | OtherCompounds = Iron(III) sulfate}} }} '''Iron(II) sulfate''' or '''ferrous sulfate''' (British English: '''sulphate''' instead of sulfate) denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the heptahydrate (''x'' = 7), but several values for x are known. The hydrated form is used medically to treat or prevent iron deficiency, and also for industrial applications. Known since ancient times as '''copperas''' and as '''green vitriol''' (vitriol is an archaic name for hydrated sulfate minerals), the blue-green heptahydrate (hydrate with 7 molecules of water) is the most common form of this material. All the iron(II) sulfates dissolve in water to give the same aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry and is paramagnetic. The name copperas dates from times when the copper(II) sulfate was known as blue copperas, and perhaps in analogy, iron(II) and zinc sulfate were known respectively as green and white copperas.<ref name= "isbn0-19-861271-0">{{cite book |author=Brown, Lesley |title=The New shorter Oxford English dictionary on historical principles |publisher=Clarendon |location=Oxford [Eng.] |year=1993 |isbn=0-19-861271-0 |url=https://archive.org/details/newshorteroxford00lesl }}</ref>

It is on the World Health Organization's List of Essential Medicines.<ref name="WHO23rd">{{cite book | title = The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023) | year = 2023 | hdl = 10665/371090 | publisher = World Health Organization | location = Geneva | id = WHO/MHP/HPS/EML/2023.02 | hdl-access=free }}</ref> In 2023, it was the 89th most commonly prescribed medication in the United States, with more than 7{{nbsp}}million prescriptions.<ref name="Top300Drugs">{{cite web | title=Top 300 of 2023 | url=https://clincalc.com/DrugStats/Top300Drugs.aspx | website=ClinCalc | access-date=12 August 2025 | archive-date=12 August 2025 | archive-url=https://web.archive.org/web/20250812130026/https://clincalc.com/DrugStats/Top300Drugs.aspx | url-status=live }}</ref><ref>{{cite web | title = Ferrous Sulfate Drug Usage Statistics, United States, 2014 - 2023 | website = ClinCalc | url = https://clincalc.com/DrugStats/Drugs/FerrousSulfate | access-date = 18 August 2025 }}</ref>

==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 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 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>

Woodworkers 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 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 ({{circa|588–586 BCE}}) showed the possible presence of iron.<ref>Torczyner, ''Lachish Letters'', pp. 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 dyeing as a mordant. 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>

==Hydrates== [[image:Iron(II)-sulfate-heptahydrate-3D-balls.tiff|thumb|left|120px|portion of the solid ferrous sulfate heptahydrate. One water of crystallization is evident.]] Iron(II) sulfate can be found in various states of hydration, and several of these forms exist in nature or were created synthetically. * FeSO4·H2O (mineral: szomolnokite,<ref name=mindat>{{cite web|first1= Jolyon|last1= Ralph|first2= Ida|last2= Chautitle|title= Szomolnokite|url= http://www.mindat.org/min-3859.html|publisher= Mindat.org|access-date= 3 August 2014}}</ref> relatively rare, monoclinic<ref name=":0">{{Cite journal |last=Meusburger |first=Johannes |date=September 2019 |title=Transformation mechanism of the pressure-induced C2/c-to-P transition in ferrous sulfate monohydrate single crystals |journal=Journal of Solid State Chemistry |volume=277 |pages=240–252 |doi=10.1016/j.jssc.2019.06.004 |s2cid=197070809 |url=https://www.sciencedirect.com/science/article/abs/pii/S0022459619302853|url-access=subscription }}</ref>) * FeSO4·H2O (synthetic compound stable at pressures exceeding 6.2 GPa, triclinic<ref name=":0" />) * FeSO4·4H2O (mineral: rozenite,<ref name="webmin">{{cite web|title= Rozenite Mineral Data|url= http://www.webmineral.com/data/Rozenite.shtml|access-date= 3 August 2014}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-3469.html|title=Rozenite}}</ref> white, relatively common, may be dehydration product of melanterite, monoclinic<ref>{{Cite web |last=Meusburger |first=Johannes |date=September 2022 |title=Low-temperature crystallography and vibrational properties of rozenite (FeSO4·4H2O), a candidate mineral component of the polyhydrated sulfate deposits on Mars |url=http://www.minsocam.org/msa/ammin/AM_Preprints/8502ForbesPreprint.pdf}}</ref>) * FeSO4·5H2O (mineral: siderotil,<ref name="webmin2">{{cite web|title= Siderotil Mineral Data|url= http://www.webmineral.com/data/Siderotil.shtml|access-date= 3 August 2014}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-3643.html|title=Siderotil}}</ref> relatively rare, triclinic<ref name=":1">{{Cite journal |url=https://pubs.geoscienceworld.org/msa/rimg/article-abstract/40/1/303/140666/Metal-sulfate-Salts-from-Sulfide-Mineral-Oxidation?redirectedFrom=fulltext |access-date=18 November 2022|title= Metal-sulfate Salts from Sulfide Mineral Oxidation|journal=Reviews in Mineralogy and Geochemistry|date=2000 |doi=10.2138/rmg.2000.40.6 |volume=40 |issue=1 |pages=303–350 |bibcode=2000RvMG...40..303J | vauthors = Jambor JL, Nordstrom DK, Alpers CN |url-access=subscription }}</ref>) * FeSO4·6H2O (mineral: ferrohexahydrite,<ref name="webmin3">{{cite web|title= Ferrohexahydrite Mineral Data|url= http://www.webmineral.com/data/Ferrohexahydrite.shtml|access-date= 3 August 2014}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-1517.html|title=Ferrohexahydrite}}</ref> very rare, monoclinic<ref name=":1" />) * FeSO4·7H2O (mineral: melanterite,<ref name="webmin4">{{cite web|title= Melanterite Mineral Data|url= http://www.webmineral.com/data/Melanterite.shtml|access-date= 3 August 2014}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-2633.html|title=Melanterite}}</ref> blue-green, relatively common, monoclinic<ref>{{Cite web |last=Peterson |first=RC |date=2003 |title=THE RELATIONSHIP BETWEEN Cu CONTENT AND DISTORTION IN THE ATOMIC STRUCTURE OF MELANTERITE FROM THE RICHMOND MINE, IRON MOUNTAIN, CALIFORNIA |url=https://rruff.info/doclib/cm/vol41/CM41_937.pdf}}</ref>)

thumb|left|Anhydrous iron(II) sulfate The tetrahydrate is stabilized when the temperature of aqueous solutions reaches {{convert|56.6|C|F}}. At {{convert|64.8|C|F}}, these solutions form both the tetrahydrate and monohydrate.<ref name=sioc>{{cite book|last1= Seidell|first1= Atherton|last2= Linke|first2= William F.|year= 1919|title= Solubilities of Inorganic and Organic Compounds|url= https://archive.org/details/solubilitiesino01seidgoog|publisher= D. Van Nostrand Company|place= New York|edition= 2nd|page= [https://archive.org/details/solubilitiesino01seidgoog/page/n368 343]}}</ref>

Mineral forms are found in oxidation zones of iron-bearing ore beds, e.g., pyrite, marcasite, chalcopyrite, etc. They are also found in related environments, like coal fire sites. Many rapidly dehydrate and sometimes oxidize. Numerous other, more complex (either basic, hydrated, and/or containing additional cations) Fe(II)-bearing sulfates exist in such environments, with copiapite being a common example.<ref name=Mindat>{{Cite web|url=https://www.mindat.org/min-1124.html|title=Copiapite}}</ref>

==Production and reactions== In the finishing of steel before plating or coating, the steel sheet or rod is passed through pickling baths of sulfuric acid. This treatment produces large quantities of iron(II) sulfate as a by-product.<ref name=Ull>{{ullmann|first1=Egon|last1=Wildermuth|first2=Hans|last2=Stark|first3=Gabriele|last3=Friedrich|first4=Franz Ludwig|last4=Ebenhöch|first5=Brigitte|last5=Kühborth|first6=Jack|last6=Silver|first7=Rafael|last7=Rituper|title=Iron Compounds}}</ref> :{{chem2 | Fe + H2SO4 -> FeSO4 + H2 }}

Another source of large amounts results from the production of titanium dioxide from ilmenite via the sulfate process.

Ferrous sulfate is also prepared commercially by oxidation of pyrite:<ref>{{cite journal |title= Aqueous oxidation of pyrite by molecular oxygen |first= Richard T. |last= Lowson |journal= Chem. Rev. |year= 1982 |volume= 82 |issue= 5 |pages= 461–497 |doi= 10.1021/cr00051a001 }}</ref> :{{chem2 | 2 FeS2 + 7 O2 + 2 H2O -> 2 FeSO4 + 2 H2SO4 }} It can be produced by displacement of metals less reactive than iron from solutions of their sulfate: :{{chem2 | CuSO4 + Fe -> FeSO4 + Cu }}

===Reactions=== [[File:Ferric sulphate, Kemira.jpg|thumb|left|Iron(II) sulfate outside a titanium dioxide factory in Kaanaa, Pori, Finland.]] Upon dissolving in water, ferrous sulfates form the metal aquo complex [Fe(H2O)6]2+, which is an almost colorless, paramagnetic ion.

On heating, iron(II) sulfate first loses its water of crystallization and the original green crystals are converted into a white anhydrous solid. When further heated, the anhydrous material decomposes into sulfur dioxide and sulfur trioxide, leaving a reddish-brown iron(III) oxide. Thermolysis of iron(II) sulfate begins at about {{convert|680|C|F}}. :{{chem2 | 2 FeSO4 }} {{overset|Δ|→}} {{chem2 | Fe2O3 + SO2 + SO3 }}

Like other iron(II) salts, iron(II) sulfate is a reducing agent. For example, it reduces nitric acid to nitrogen monoxide and chlorine to chloride: :{{chem2 | 6 FeSO4 + 3 H2SO4 + 2 HNO3 -> 3 Fe2(SO4)3 + 4 H2O + 2 NO }} :{{chem2 | 6 FeSO4 + 3 Cl2 -> 2 Fe2(SO4)3 + 2 FeCl3 }} Its mild reducing power is of value in organic synthesis.<ref>{{cite journal|journal=Org. Synth.|year=1948|volume=28|page=11|doi=10.15227/orgsyn.028.0011|title=o-Aminobenzaldehyde|author1=Lee Irvin Smith|author2=J. W. Opie}}</ref> It is used as the iron catalyst component of Fenton's 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.<ref>{{Cite web |url=https://cpha.tu.edu.iq/images/%D8%B9%D9%85%D8%B1_%D8%AD%D8%B3%D9%8A%D9%86/ASSAY_OF_FERROUS_SULPHATE__ali_hussein-%D9%85%D8%AD%D9%88%D9%84_1.pdf |archive-url=https://web.archive.org/web/20230929051907/https://cpha.tu.edu.iq/images/%D8%B9%D9%85%D8%B1_%D8%AD%D8%B3%D9%8A%D9%86/ASSAY_OF_FERROUS_SULPHATE__ali_hussein-%D9%85%D8%AD%D9%88%D9%84_1.pdf |archive-date=2023-09-29 |last=Al-Obaidi |first=Ali Hussein Mustafa|title=ASSAY OF FERROUS SULPHATE }}</ref>

==See also== * Iron supplement * Iron(III) sulfate (ferric sulfate), the other common simple sulfate of iron * Copper(II) sulfate * Ammonium iron(II) sulfate, also known as ''Mohr's 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'<ref>{{cite book |last=Pryce |first=William |title=Mineralogia Cornubiensis; a Treatise on Minerals, Mines and Mining|location=London|url=https://archive.org/details/b30449170|year=1778|publisher=Phillips|page=[https://archive.org/details/b30449170/page/33 33]}}</ref>

==References== {{Reflist}}

== External links == {{Commons category|Iron(II) sulfate}} *{{cite AmCyc |last=Hunt |first=T. Sterry |author-link=T. Sterry Hunt |wstitle=Copperas |short=x}}

Category:Iron(II) compounds Category:Sulfates Category:World Health Organization essential medicines Category:Deliquescent materials Category:Over-the-counter drugs in the United States