Strontium sulfate
Chemical compound
From Wikipedia, the free encyclopedia
Strontium sulfate (SrSO4) is the sulfate salt of strontium. It is a white crystalline powder and occurs in nature as the mineral celestine. It is very poorly soluble in water.
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| Names | |
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| IUPAC name
Strontium sulfate | |
| Other names | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.028.955 |
| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties[1] | |
| SrSO4 | |
| Molar mass | 183.68 g·mol−1 |
| Appearance | white orthorhombic crystals |
| Density | 3.96 g/cm3 |
| Melting point | 1,606 °C (2,923 °F; 1,879 K) |
| 0.00138 g/100 mL[2] | |
Solubility product (Ksp) |
3.44×10−7 |
| Solubility | slightly soluble in acids |
| Band gap | 5.92 eV[3] |
| −57.9×10−6 cm3/mol | |
Refractive index (nD) |
1.622[4] |
| Structure[3] | |
| Orthorhombic | |
| Pnma, No. 62 | |
| mmm | |
a = 5.34 Å, b = 6.87 Å, c = 8.36 Å α = 90°, β = 90°, γ = 90° | |
Lattice volume (V) |
306.72 Å3 |
Formula units (Z) |
4 |
| Thermochemistry[1] | |
Std molar entropy (S⦵298) |
117.0 J⋅mol−1·K-1 |
Std enthalpy of formation (ΔfH⦵298) |
−1453.1 kJ⋅mol−1 |
Gibbs free energy (ΔfG⦵) |
−1340.9 kJ⋅mol−1 |
Enthalpy of fusion (ΔfH⦵fus) |
36 kJ⋅mol−1 |
| Hazards | |
| GHS labelling:[5] | |
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| Warning | |
| H302, H315, H319, H335 | |
| P261, P305+P351+P338 | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Other anions |
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Other cations |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure
Strontium sulfate is a polymeric material, isostructural with barium sulfate.[citation needed]
Applications and chemistry
Strontium sulfate is of interest as a naturally occurring precursor to other strontium compounds, which are more useful. In industry it is converted to strontium carbonate (SrCO3) for use as ceramic precursor and strontium nitrate (Sr(NO3)2) for use in pyrotechnics.[7]
The low aqueous solubility of strontium sulfate can lead to scale formation in processes where these ions meet. For example, it can form on surfaces of equipment in underground oil wells depending on the groundwater conditions.[8][9]
Pyrotechnics
Strontium sulfate is used as a high temperature / flash phase oxidizer in some red strobing compositions, along with ammonium perchlorate (NH4ClO4 and treated magnesium or magnalium powder. One theory as to why this occurs is that the ammonium perchlorate sustains combustion at a very low temperature until enough heat has built up for the sulfate combustion reaction to occur. This reaction is extremely rapid and consumes the portion of the composition that was hot enough for the sulfate to act as an oxidizer producing a rapid flash of light, the ammonium perchlorate-metal portion of the composition continues burning with very little flame, and the cycle repeats.[10]
Biological role
Crystallized strontium sulfate is utilized by a small group of radiolarian protozoa, called the Acantharea, as a main constituent of their skeleton.[citation needed]