Iron(II) sulfate when dissolved in water | |
Names | |
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IUPAC name Iron(II) sulfate | |
Other names Iron(II) sulphate; Ferrous sulfate, Green vitriol, Iron vitriol, Ferrous vitriol, Copperas, Melanterite, Szomolnokite, | |
Identifiers | |
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3D model (JSmol) |
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ChEBI |
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ChEMBL |
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ChemSpider | |
ECHA InfoCard | 100.028.867 |
EC Number |
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PubChem CID | |
RTECS number |
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UNII |
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UN number | 3077 |
CompTox Dashboard (EPA) |
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Properties | |
FeSO4 | |
Molar mass | 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) |
Appearance | White crystals (anhydrous) White-yellow crystals (monohydrate) Blue-green deliquescent [1] crystals (heptahydrate) |
Odor | Odorless |
Density | 3.65 g/cm3 (anhydrous) 3 g/cm3 (monohydrate) 2.15 g/cm3 (pentahydrate) [2] 1.934 g/cm3 (hexahydrate) [3] 1.895 g/cm3 (heptahydrate) [4] |
Melting point | 680 °C (1,256 °F; 953 K) (anhydrous) decomposes [5] 300 °C (572 °F; 573 K) (monohydrate) decomposes 60–64 °C (140–147 °F; 333–337 K) (heptahydrate) decomposes [4] [6] |
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) [7] | |
Solubility | Negligible in alcohol |
Solubility in ethylene glycol | 6.38 g/100 g (20 °C) [5] |
Vapor pressure | 1.95 kPa (heptahydrate) [8] |
1.24×10−2 cm3/mol (anhydrous) 1.05×10−2 cm3/mol (monohydrate) 1.12×10−2 cm3/mol (heptahydrate) [4] +10200×10−6 cm3/mol | |
Refractive index (nD) | 1.591 (monohydrate) [9] 1.526–1.528 (21 °C, tetrahydrate) [10] 1.513–1.515 (pentahydrate) [2] 1.468 (hexahydrate) [3] 1.471 (heptahydrate) [11] |
Structure | |
Orthorhombic, oP24 (anhydrous) [12] Monoclinic, mS36 (monohydrate) [9] Monoclinic, mP72 (tetrahydrate) [10] Triclinic, aP42 (pentahydrate) [2] Monoclinic, mS192 (hexahydrate) [3] Monoclinic, mP108 (heptahydrate) [4] [11] | |
Pnma, No. 62 (anhydrous) [12] C2/c, No. 15 (monohydrate, hexahydrate) [3] [9] P21/n, No. 14 (tetrahydrate) [10] P1, No. 2 (pentahydrate) [2] P21/c, No. 14 (heptahydrate) [11] | |
2/m 2/m 2/m (anhydrous) [12] 2/m (monohydrate, tetrahydrate, hexahydrate, heptahydrate) [3] [9] [10] [11] 1 (pentahydrate) [2] | |
α = 90°, β = 90°, γ = 90° | |
Octahedral (Fe2+) | |
Thermochemistry | |
Heat capacity (C) | 100.6 J/mol·K (anhydrous) [4] 394.5 J/mol·K (heptahydrate) [13] |
Std molar entropy (S⦵298) | 107.5 J/mol·K (anhydrous) [4] 409.1 J/mol·K (heptahydrate) [13] |
Std enthalpy of formation (ΔfH⦵298) | −928.4 kJ/mol (anhydrous) [4] −3016 kJ/mol (heptahydrate) [13] |
Gibbs free energy (ΔfG⦵) | −820.8 kJ/mol (anhydrous) [4] −2512 kJ/mol (heptahydrate) [13] |
Pharmacology | |
B03AA07 ( WHO ) | |
none | |
Pharmacokinetics: | |
4 days [14] | |
2-4 months with peak activity at 7-10 days [15] | |
Legal status |
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Hazards | |
GHS labelling: | |
[8] | |
Warning | |
H302, H315, H319 [8] | |
P305+P351+P338 [8] | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 237 mg/kg (rat, oral) [6] |
NIOSH (US health exposure limits): | |
REL (Recommended) | TWA 1 mg/m3 [17] |
Related compounds | |
Other cations | Cobalt(II) sulfate Copper(II) sulfate Manganese(II) sulfate Nickel(II) sulfate |
Related compounds | Iron(III) sulfate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·xH2O. 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. [18]
It is on the World Health Organization's List of Essential Medicines. [19] In 2021, it was the 105th most commonly prescribed medication in the United States, with more than 6 million prescriptions. [20] [21]
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. [22] 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.
Iron(II) sulfate is sold as ferrous sulfate, a soil amendment [23] for lowering the pH of a high alkaline soil so that plants can access the soil's nutrients. [24]
In horticulture it is used for treating iron chlorosis. [25] 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. [26] Ferrous sulfate can be used as a lawn conditioner. [26] It can also be used to eliminate silvery thread moss in golf course putting greens. [27]
Ferrous sulfate can be used to stain concrete and some limestones and sandstones a yellowish rust color. [28]
Woodworkers use ferrous sulfate solutions to color maple wood a silvery hue.
Green vitriol is also a useful reagent in the identification of mushrooms. [29]
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. [30] It is thought that oak galls and copperas may have been used in making the ink on those letters. [31] 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. [32]
Iron(II) sulfate can be found in various states of hydration, and several of these forms exist in nature or were created synthetically.
The tetrahydrate is stabilized when the temperature of aqueous solutions reaches 56.6 °C (133.9 °F). At 64.8 °C (148.6 °F) these solutions form both the tetrahydrate and monohydrate. [7]
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. [41]
In the finishing of steel prior to 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. [42]
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: [43]
It can be produced by displacement of metals less reactive than Iron from solutions of their sulfate:
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 680 °C (1,256 °F).
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:
Its mild reducing power is of value in organic synthesis. [44] 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. [45]
Sulfuric acid or sulphuric acid, known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, and hydrogen, with the molecular formula H2SO4. It is a colorless, odorless, and viscous liquid that is miscible with water.
In chemistry, iron(II) refers to the element iron in its +2 oxidation state. The adjective ferrous or the prefix ferro- is often used to specify such compounds, as in ferrous chloride for iron(II) chloride (FeCl2). The adjective ferric is used instead for iron(III) salts, containing the cation Fe3+. The word ferrous is derived from the Latin word ferrum, meaning "iron".
Magnesium sulfate or magnesium sulphate is a chemical compound, a salt with the formula MgSO4, consisting of magnesium cations Mg2+ (20.19% by mass) and sulfate anions SO2−4. It is a white crystalline solid, soluble in water but not in ethanol.
Copper(II) sulfate is an inorganic compound with the chemical formula CuSO4. It forms hydrates CuSO4·nH2O, where n can range from 1 to 7. The pentahydrate (n = 5), a bright blue crystal, is the most commonly encountered hydrate of copper(II) sulfate, while its anhydrous form is white. Older names for the pentahydrate include blue vitriol, bluestone, vitriol of copper, and Roman vitriol. It exothermically dissolves in water to give the aquo complex [Cu(H2O)6]2+, which has octahedral molecular geometry. The structure of the solid pentahydrate reveals a polymeric structure wherein copper is again octahedral but bound to four water ligands. The Cu(II)(H2O)4 centers are interconnected by sulfate anions to form chains.
Zinc sulfate describes a family of inorganic compounds with the formula ZnSO4(H2O)x. All are colorless solids. The most common form includes water of crystallization as the heptahydrate, with the formula ZnSO4·7H2O. As early as the 16th century it was prepared on the large scale, and was historically known as "white vitriol" (the name was used, for example, in 1620s by the collective writing under the pseudonym of Basil Valentine). Zinc sulfate and its hydrates are colourless solids.
Chalcanthite (from Ancient Greek χάλκανθον (khálkanthon), from χαλκός (khalkós) 'copper' and ἄνθος (ánthos) 'flower, bloom') is a richly colored blue-green water-soluble sulfate mineral CuSO4·5H2O. It is commonly found in the late-stage oxidation zones of copper deposits. Due to its ready solubility, chalcanthite is more common in arid regions.
In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio. Classically, "water of crystallization" refers to water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation.
Copiapite is a hydrated iron sulfate mineral with formula: Fe2+Fe3+4(SO4)6(OH)2·20(H2O). Copiapite can also refer to a mineral group, the copiapite group.
Nickel(II) sulfate, or just nickel sulfate, usually refers to the inorganic compound with the formula NiSO4(H2O)6. This highly soluble blue green coloured salt is a common source of the Ni2+ ion for electroplating. Approximately 40,000 tonnes were produced in 2005.
In ore deposit geology, supergene processes or enrichment are those that occur relatively near the surface as opposed to deep hypogene processes. Supergene processes include the predominance of meteoric water circulation (i.e. water derived from precipitation) with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary (hypogene) sulfide ore minerals and redistribute the metallic ore elements. Supergene enrichment occurs at the base of the oxidized portion of an ore deposit. Metals that have been leached from the oxidized ore are carried downward by percolating groundwater, and react with hypogene sulfides at the supergene-hypogene boundary. The reaction produces secondary sulfides with metal contents higher than those of the primary ore. This is particularly noted in copper ore deposits where the copper sulfide minerals chalcocite (Cu2S), covellite (CuS), digenite (Cu18S10), and djurleite (Cu31S16) are deposited by the descending surface waters.
Manganese(II) sulfate usually refers to the inorganic compound with the formula MnSO4·H2O. This pale pink deliquescent solid is a commercially significant manganese(II) salt. Approximately 260,000 tonnes of manganese(II) sulfate were produced worldwide in 2005. It is the precursor to manganese metal and many other chemical compounds. Manganese-deficient soil is remediated with this salt.
Ammonium iron(II) sulfate, or Mohr's salt, is the inorganic compound with the formula (NH4)2SO4.Fe(SO4).6H2O. Containing two different cations, Fe2+ and NH+4, it is classified as a double salt of ferrous sulfate and ammonium sulfate. It is a common laboratory reagent because it is readily crystallized, and crystals resist oxidation by air. Like the other ferrous sulfate salts, ferrous ammonium sulfate dissolves in water to give the aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry. Its mineral form is mohrite.
Iron(III) sulfate (or ferric sulfate), is a family of inorganic compounds with the formula Fe2(SO4)3(H2O)n. A variety of hydrates are known, including the most commonly encountered form of "ferric sulfate". Solutions are used in dyeing as a mordant, and as a coagulant for industrial wastes. Solutions of ferric sulfate are also used in the processing of aluminum and steel.
Chromium(III) sulfate usually refers to the inorganic compounds with the formula Cr2(SO4)3.x(H2O), where x can range from 0 to 18. Additionally, ill-defined but commercially important "basic chromium sulfates" are known. These salts are usually either violet or green solids that are soluble in water. It is commonly used in tanning leather.
Cobalt(II) sulfate is any of the inorganic compounds with the formula CoSO4(H2O)x. Usually cobalt sulfate refers to the hexa- or heptahydrates CoSO4.6H2O or CoSO4.7H2O, respectively. The heptahydrate is a red solid that is soluble in water and methanol. Since cobalt(II) has an odd number of electrons, its salts are paramagnetic.
Ammonium iron(III) sulfate, NH4Fe(SO4)2·12 H2O, or NH4[Fe(H2O)6](SO4)2·6 H2O, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB(SO4)2 · 12 H2O. It has the appearance of weakly violet, octahedrical crystals. There has been some discussion regarding the origin of the crystals' color, with some ascribing it to impurities in the compound, and others claiming it to be a property of the crystal itself.
Zirconium(IV) sulfate is the name for a family of inorganic salts with the formula Zr(SO4)2(H2O)n where n = 0, 4, 5, 7. These species are related by the degree of hydration. They are white or colourless solids that are soluble in water.
Chvaleticeite is a monoclinic hexahydrite manganese magnesium sulfate mineral with formula: (Mn2+, Mg)[SO4]·6(H2O). It occurs in the oxidized zone of manganese silicate deposits with pyrite and rhodochrosite that have undergone regional and contact metamorphism. It is defined as the manganese dominant member of the hexahydrite group.
Iron(II) selenate (ferrous selenate) is an inorganic compound with the formula FeSeO4. It has anhydrous and several hydrate forms. The pentahydrate has the structure, [Fe(H2O)4]SeO4•H2O, isomorphous to the corresponding iron(II) sulfate. Heptahydrate is also known, in form of unstable green crystalline solid.