Cobalt Sulfate (10124-43-3) Physical and Chemical Properties
Cobalt Sulfate
Inorganic cobalt(II) sulfate supplied as crystalline salts and hydrates, commonly used as a precursor in materials synthesis, electrochemical formulations and laboratory reagents.
| CAS Number | 10124-43-3 |
| Family | Transition metal sulfates |
| Typical Form | Powder or crystalline solid (anhydrous or hydrated) |
| Common Grades | BP, EP, Reagent Grade, USP |
Cobalt sulfate is an inorganic transition-metal sulfate salt of cobalt in the +2 oxidation state; its simple 1:1 composition is commonly represented as CoSO4 (computed formula CoO4S). Structurally it is an ionic assembly of \( \mathrm{Co}^{2+} \) cations and \( \mathrm{SO}_4^{2-} \) anions. In solid form cobalt(II) sulfate exists in hydrated crystalline forms (heptahydrate, hexahydrate, monohydrate) and an anhydrous form; the hydration state controls color, crystal system and many physical properties. The sulfate anion presents four oxygen donors that coordinate the cobalt ion in typical octahedral or distorted-octahedral arrangements when water of crystallization is present.
Electronically, cobalt(II) in this salt is a first-row transition-metal dication; ligand-field effects and spin state are determined by coordination geometry and hydration. The salt behaves as an acidic inorganic salt: aqueous solutions supply dissolved \( \mathrm{Co}^{2+} \) and sulfate and are mildly to moderately acidic (pH < 7) because metal aquo complexes can release protons. The material is water-soluble and nonvolatile; redox behavior is dominated by cobalt redox chemistry (Co(II) ⇄ Co(III) under oxidizing conditions) and decomposition liberates sulfur oxides on strong heating or in combustion.
Cobalt sulfate is widely used industrially as a water‑soluble source of cobalt for electroplating, pigments and ceramics, driers for inks and paints, battery materials, and as a micronutrient source in agricultural and veterinary formulations (noting regulatory restrictions for food use). Its toxicological profile—sensitization, respiratory effects, reproductive and carcinogenic hazard potential, and aquatic toxicity—strongly dictates industrial hygiene and environmental controls in handling and use. Common commercial grades reported for this substance include: BP, EP, Reagent Grade, USP.
Basic Physical Properties
Density
Reported solid and crystalline densities vary with hydrate form and measurement condition; selected reported values are: - 1.948 at \(68\,^\circ\mathrm{F}\) — denser than water and will sink. - 1.948 \(\mathrm{g}\,\mathrm{cm}^{-3}\). - 2.01 \(\mathrm{kg}\,\mathrm{L}^{-1}\) at \(25\,^\circ\mathrm{C}\) (hexahydrate description). - 3.71 (reported as 3.71 at \(25\,^\circ\mathrm{C}/4\,^\circ\mathrm{C}\) and as 3.71 \(\mathrm{g}\,\mathrm{cm}^{-3}\)).
Interpretation: reported densities cluster by hydration state and measurement conventions; hydrated forms typically show lower apparent bulk density than some anhydrous or differently prepared crystalline specimens. For engineering calculations, use the density value that corresponds to the specific hydrate/form supplied.
Melting or Decomposition Point
Thermal behavior depends strongly on hydration state: - Anhydrous decomposition reported at \(735\,^\circ\mathrm{C}\); heating to decomposition emits toxic sulfur‑oxide vapors. - Stability noted up to approximately \(708\,^\circ\mathrm{C}\) for some forms. - Hydrated forms lose waters of crystallization at much lower temperatures (e.g., dehydration above \(\sim 41.5\,^\circ\mathrm{C}\) to form lower hydrates; monohydrate/anhydrous conversion above \(\sim 250\,^\circ\mathrm{C}\)); reported melting/transition values for hydrates include MP: \(96.8\,^\circ\mathrm{C}\) and MP: \(95\,^\circ\mathrm{C}\) associated with water loss.
Interpretation: the crystalline hydrate stage determines the apparent melting point; anhydrous material decomposes at high temperature releasing SOx rather than showing a simple melting transition.
Solubility in Water
Solubility is highly temperature- and hydration-dependent; representative reported values: - In water, \(330\,\mathrm{g}\,\mathrm{L}^{-1}\) at \(20\,^\circ\mathrm{C}\). - \(38.3\,\mathrm{g}\) per \(100\,\mathrm{g}\) water at \(25\,^\circ\mathrm{C}\). - \(36.2\,\mathrm{g}\) per \(100\,\mathrm{mL}\) water at \(20\,^\circ\mathrm{C}\) (reported as g/100 mL). - \(84\,\mathrm{g}\) per \(100\,\mathrm{mL}\) water at \(100\,^\circ\mathrm{C}\). - Heptahydrate and other hydrated forms have separate solubility listings (e.g., 60.4 g/100 cc water at \(3\,^\circ\mathrm{C}\); 67 g/100 cc at \(70\,^\circ\mathrm{C}\)).
Interpretation: cobalt sulfate is readily water‑soluble; solubility increases substantially with temperature and varies between anhydrous and hydrated salts. Dissolution is accompanied by an enthalpy of solution (reported heat of solution ~ 13 cal/g in one account).
Solution pH (Qualitative Behavior)
Cobalt sulfate is an acidic salt: aqueous solutions are typically mildly to moderately acidic. Reported qualitative behavior: "Acidic salts, such as cobalt sulfate, result in aqueous solutions containing moderate concentrations of hydrogen ions and have pH's of less than 7.0." In practice, the solution pH depends on concentration and the presence of complexing or buffering species.
Chemical Properties
Acid–Base Behavior
Cobalt sulfate behaves as an acidic inorganic salt derived from a weakly basic metal cation and a strong oxoanion. Dissolution produces \( \mathrm{Co}^{2+} \) aquo complexes which can hydrolyze to release protons; thus solutions typically exhibit pH < 7.0 and will neutralize bases with heat evolution. Metal ion complexation with ligands (e.g., water, sulfate, other coordinating anions) influences acidity and speciation.
Reactivity and Stability
- Water reaction: water‑soluble; hydrates interconvert with temperature (efflorescence and dehydration behavior reported).
- Thermal decomposition: on strong heating cobalt sulfate decomposes, producing sulfur oxides and potentially toxic cobalt‑containing fumes.
- Oxidizers and incompatibilities: the dry dust or powder can react with strong oxidizing agents and contribute to fire/explosion hazards; avoid storage with strong oxidants.
- Redox: cobalt(II) can be oxidized to cobalt(III) under sufficiently oxidizing conditions; salts may catalyze oxidation reactions of organics under certain conditions.
- Shelf life/stability: reported stable under normal storage but will evolve waters of crystallization on heating and may effloresce in dry air depending on hydrate.
Molecular and Ionic Parameters
Formula and Molecular Weight
- Computed molecular formula (canonical): CoO4S (commonly represented as CoSO4).
- Reported molecular weight: 155.00.
- Exact/monoisotopic mass: 154.884923.
Constituent Ions
The compound dissociates to give: - \( \mathrm{Co}^{2+} \) (cobalt(II) ion) - \( \mathrm{SO}_4^{2-} \) (sulfate anion)
Computed and structural descriptors available include SMILES: [O-]S(=O)(=O)[O-].[Co+2] and InChI: InChI=1S/Co.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2. The InChIKey is KTVIXTQDYHMGHF-UHFFFAOYSA-L.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS Registry Number: 10124-43-3
- EC Number (reported): 233-334-2
- UNII: H7965X29HX
- ChEBI: CHEBI:53470
- InChI: InChI=1S/Co.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
- InChIKey: KTVIXTQDYHMGHF-UHFFFAOYSA-L
- SMILES: [O-]S(=O)(=O)[O-].[Co+2]
(Only identifiers reported in the available descriptive material are listed above.)
Synonyms and Common Names
Common synonyms appearing in descriptive lists include: - cobalt sulfate - cobaltous sulfate - cobalt(2+) sulfate - Cobalt(II) sulfate - CoSO4 - cobalt monosulfate - Cobalt(II) sulphate - cobaltous sulphate
Use the exact supplier or certificate nomenclature when ordering to ensure the correct hydrate and grade.
Industrial and Commercial Applications
Functional Roles and Use Sectors
Cobalt sulfate serves as a water‑soluble cobalt source and is used across multiple sectors: - Pigments and ceramic/porcelain coloration (glass, glazes, enamels). - Electroplating baths and surface treatment (nickel/cobalt plating additives). - Battery manufacturing and related electrochemical uses. - Driers for paints and inks (as catalytic drying agents). - Agricultural and veterinary uses as a cobalt supplement for ruminants (subject to regulatory limits). - Catalysis and laboratory reagent uses.
Typical Application Examples
Examples of typical uses: - Addition to electroplating baths to modify deposit properties (brightness, hardness, ductility). - Precursor in pigment formulations for ceramic and porcelain coloration. - Formulation of micronutrient feed supplements (regulated use levels). - Industry processes with occupational exposure potential include electroplating, battery manufacturing, pigment and ceramic production, and paint/ink formulation.
If proprietary formulations or feed/food applications are intended, consult regulatory guidance and product-specific specifications to confirm permitted uses and limits.
Safety and Handling Overview
Health and Environmental Hazards
Hazard profile (summary of reported hazard classifications and toxicology): - Sensitization: may cause skin sensitization and respiratory sensitization; occupational exposures have been associated with asthma and contact dermatitis. - Mutagenicity and carcinogenicity: suspected mutagen and classified in various authoritative listings as reasonably anticipated or possibly carcinogenic based on animal data; inhalation exposure is a principal concern. - Reproductive and developmental toxicity: reported potential for reproductive toxicity and effects on fertility in some assessments. - Target organs and systemic effects: repeated or high exposures may affect heart (cardiomyopathy), lungs, thyroid, kidney and bone marrow; acute inhalation can cause respiratory irritation, shortness of breath and coughing. - Acute toxicity examples: LD50 (oral, rat) reported as \(424\,\mathrm{mg}\,\mathrm{kg}^{-1}\); LD50 (ip, mouse) \(143\,\mathrm{mg}\,\mathrm{kg}^{-1}\). These values illustrate significant systemic toxicity by common exposure routes. - Environmental toxicity: very toxic to aquatic life with long‑lasting effects; avoid environmental release.
For emergency and clinical response, standard symptomatic and supportive treatments are indicated; severe exposures require medical evaluation and supportive care.
Storage and Handling Considerations
- Store in tightly sealed containers to avoid moisture ingress or dust dispersion; maintain segregation from strong oxidizers.
- Prevent dust generation and aerosolization; use local exhaust ventilation and containment for processes that can create airborne particulates.
- Personal protective equipment: use chemical-resistant gloves, eye protection, impermeable protective clothing and, if airborne concentrations may exceed occupational limits, appropriately selected respiratory protection (NIOSH‑approved respirator). Avoid ingestion, inhalation and skin contact.
- Spill response: collect dry material with methods that minimize dust (wetting, vacuum with HEPA filter) and dispose of according to local regulations; do not permit release to waterways.
- For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
Concluding safety note: occupational exposure limits and biological monitoring guidance for cobalt (expressed as Co) exist and should be consulted during process design and risk assessment (airborne inhalable fraction limits and biological exposure indices are used in workplace monitoring).
