Chemistry:Cobalt(II) sulfate

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Short description: Inorganic compound
Cobalt(II) sulfate
Cobalt(II) sulfate Xray
IUPAC name
Cobalt(II) sulfate
Other names
Cobaltous sulfate
3D model (JSmol)
EC Number
  • 233-334-2
RTECS number
  • GG3100000 (anhydrous)
    GG3200000 (heptahydrate)
CoSO4·(H2O)n (n=0,1,6,7)
Molar mass 154.996 g/mol (anhydrous)
173.01 g/mol (monohydrate)
263.08 g/mol (hexahydrate)
281.103 g/mol (heptahydrate)
Appearance reddish crystalline (anhydrous, monohydrate)
pink salt (hexahydrate)
Odor odorless (heptahydrate)
Density 3.71 g/cm3 (anhydrous)
3.075 g/cm3 (monohydrate)
2.019 g/cm3 (hexahydrate)
1.948 g/cm3 (heptahydrate)
Melting point 735 °C (1,355 °F; 1,008 K)
36.2 g/100 mL (20 °C)
38.3 g/100 mL (25 °C)
84 g/100 mL (100 °C)
60.4 g/100 mL (3 °C)
67 g/100 mL (70 °C)
Solubility anhydrous:
1.04 g/100 mL (methanol, 18 °C)
insoluble in ammonia
54.5 g/100 mL (methanol, 18 °C)
+10,000·10−6 cm3/mol
1.639 (monohydrate)
1.540 (hexahydrate)
1.483 (heptahydrate)
orthorhombic (anhydrous)
monoclinic (monohydrate, heptahydrate)
Safety data sheet JT Baker MSDS
GHS pictograms GHS07: HarmfulGHS08: Health hazardGHS09: Environmental hazard
GHS Signal word Danger
H302, H317, H334, H341, H350, H360, H400, H410
P201, P202, P261, P264, P270, P272, P273, P280, P281, P285, P301+312, P302+352, P304+341, P308+313, P321, P330, P333+313, P342+311, P363, P391, P405, P501
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
424 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
Tracking categories (test):

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.[1] The heptahydrate is a red solid that is soluble in water and methanol. Since cobalt(II) has an odd number of electrons, it salts are paramagnetic.

Preparation, and structure

It forms by the reaction of metallic cobalt, its oxide, hydroxide, or carbonate with aqueous sulfuric acid:[1]

Co + H2SO4 + 7 H2O → CoSO4(H2O)7 + H2
CoO + H2SO4 + 6 H2O → CoSO4(H2O)7

The heptahydrate is only stable at humidity >70% at room temperature, otherwise it converts to the hexahydrate.[2] The hexahydrate converts to the monohydrate and the anhydrous forms at 100 and 250 °C, respectively.[1]

CoSO4(H2O)7 → CoSO4(H2O)6 + H2O
CoSO4(H2O)6 → CoSO4(H2O) + 5 H2O
CoSO4(H2O) → CoSO4 + H2O

The hexahydrate is a metal aquo complex consisting of octahedral [Co(H2O)6]2+ ions associated with sulfate anions (see image in table).[3] The monoclinic heptahydrate has also been characterized by X-ray crystallography. It also features [Co(H2O)6]2+ octahedra as well as one water of crystallization.[2]

Uses and reactions

Cobalt sulfates are important intermediates in the extraction of cobalt from its ores. Thus, crushed, partially refined ores are treated with sulfuric acid to give red-colored solutions containing cobalt sulfate.[1]

Hydrated cobalt(II) sulfate is used in the preparation of pigments, as well as in the manufacture of other cobalt salts. Cobalt pigment is used in porcelains and glass. Cobalt(II) sulfate is used in storage batteries and electroplating baths, sympathetic inks, and as an additive to soils and animal feeds. For these purposes, the cobalt sulfate is produced by treating cobalt oxide with sulfuric acid.[1]

Being commonly available commercially, the heptahydrate is a routine source of cobalt in coordination chemistry.[4]

Natural occurrence

Rarely, cobalt(II) sulfate is found in form of few crystallohydrate minerals, occurring among oxidation zones containing primary Co minerals (like skutterudite or cobaltite). These minerals are: biebierite (heptahydrate), moorhouseite (Co,Ni,Mn)SO4.6H2O,[5][6] aplowite (Co,Mn,Ni)SO4.4H2O and cobaltkieserite (monohydrate).[7][8][6]

Health issues

Cobalt is an essential mineral for mammals, but more than a few micrograms per day is harmful. Although poisonings have rarely resulted from cobalt compounds, their chronic ingestion has caused serious health problems at doses far less than the lethal dose. In 1965, the addition a cobalt compound to stabilize beer foam in Canada led to a peculiar form of toxin-induced cardiomyopathy, which came to be known as beer drinker's cardiomyopathy.[9][10][11]

Furthermore, cobalt(II) sulfate is suspected of causing cancer (i.e., possibly carcinogenic, IARC Group 2B) as per the International Agency for Research on Cancer (IARC) Monographs.[12]


  1. 1.0 1.1 1.2 1.3 1.4 Donaldson, John Dallas; Beyersmann, Detmar (2005). "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. 
  2. 2.0 2.1 Redhammer, G. J.; Koll, L.; Bernroider, M.; Tippelt, G.; Amthauer, G.; Roth, G. (2007). "Co2+-Cu2+ Substitution in Bieberite Solid-Solution Series, (Co1−xCux)SO4 · 7H2O, 0.00 ≤ x ≤ 0.46: Synthesis, Single-Crystal Structure Analysis, and Optical Spectroscopy". American Mineralogist 92 (4): 532–545. doi:10.2138/am.2007.2229. Bibcode2007AmMin..92..532R. 
  3. Elerman, Y. "Refinement of the Crystal Structure of CoSO4 · 6H2O" Acta Crystallographica Section C 1988, volume 44, p599-p601. doi:10.1107/S0108270187012447
  4. Broomhead, J. A.; Dwyer, F. P.; Hogarth, J. W. (1950). "Resolution of the Tris(ethylenediamine)cobalt(III) Ion". Inorganic Syntheses 6: 183–186. doi:10.1002/9780470132371.ch58. ISBN 9780470132371. 
  5. "Moorhouseite". 
  6. 6.0 6.1 "List of Minerals". 21 March 2011. 
  7. "Cobaltkieserite". 
  8. "Bieberite". 
  9. Morin Y; Tětu A; Mercier G (1969). "Quebec beer-drinkers' cardiomyopathy: Clinical and hemodynamic aspects". Annals of the New York Academy of Sciences 156 (1): 566–576. doi:10.1111/j.1749-6632.1969.tb16751.x. PMID 5291148. Bibcode1969NYASA.156..566M. 
  10. Barceloux, Donald G.; Barceloux, Donald (1999). "Cobalt". Clinical Toxicology 37 (2): 201–216. doi:10.1081/CLT-100102420. PMID 10382556. 
  11. 11.1.5 The unusual type of myocardiopathy recognized in 1965 and 1966 in Quebec (Canada), Minneapolis (Minnesota), Leuven (Belgium), and Omaha (Nebraska) was associated with episodes of acute heart failure (e/g/, 50 deaths among 112 beer drinkers).
  12. "Cobalt in Hard Metals and Cobalt Sulfate, Gallium Arsenide, Indium Phosphide and Vanadium Pentoxide". IARC Monographs on the Evaluation of Carcinogenic Risks to Humans.