Strontium hydroxide, Sr(OH)2, is a caustic alkali composed of one strontium ion and two hydroxide ions. It is synthesized by combining a strontium salt with a strong base. Sr(OH)2 exists in anhydrous, monohydrate, heptahydrate, and octahydrate form.
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| Identifiers | |
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3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.038.501 |
| EC Number |
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| 847042 | |
PubChem CID |
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| UNII |
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CompTox Dashboard (EPA) |
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| Properties[1] | |
| Sr(OH)2 | |
| Molar mass |
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| Appearance | colourless orthorhombic crystals, hygroscopic |
| Density |
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| Melting point | anhydrous: 535 °C (995 °F; 808 K) |
| Boiling point | 710 °C (1,310 °F; 983 K)
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| 2.25 g/100 g | |
| Basicity (pKb) |
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| −40.0×10−6 cm3/mol | |
| Structure[3] | |
| Orthorhombic | |
| Pmc21 [26] | |
| mm2 | |
a = 3.997 Å, b = 6.078 Å, c = 10.072 Å α = 90°, β = 90°, γ = 90° | |
Lattice volume (V) |
244.677 Å3 |
Formula units (Z) |
4 |
| Thermochemistry[1] | |
Std enthalpy of formation (ΔfH⦵298) |
−959.0 kJ⋅mol−1 |
Enthalpy of fusion (ΔfH⦵fus) |
23 kJ⋅mol−1 |
| Hazards | |
| 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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Preparation
editBecause Sr(OH)2 is only slightly soluble in cold water, its preparation can be easily carried out by the addition of a strong base such as NaOH or KOH drop by drop to a solution of any soluble strontium salt, most commonly Sr(NO3)2 (strontium nitrate), which forms the octahydrate. This must be done in the absence of CO2 to prevent formation of the nearly insoluble carbonate which would complicate purification:
- Sr(NO3)2·4H2O + 2 KOH + 4 H2O → Sr(OH)2·8H2O + 2 KNO3
The Sr(OH)2 will precipitate out as a fine white powder. From here, the solution is filtered, and the Sr(OH)2 is washed with a large excess of ice cold water and dried.[2]
The anhydrous form or any of the hydrates may be prepared by adding one molar equivalent of water to strontium oxide (SrO). The hydrates may be prepared by adding the required amount of water (one, seven, or eight more molar equivalents) to the anhydrous form.[2]
Applications
editStrontium hydroxide is used chiefly in the refining of beet sugar and as a stabilizer in plastic. It may be used as a source of strontium ions when the chlorine from strontium chloride (SrCl2) is undesirable. Strontium hydroxide absorbs carbon dioxide (CO2) from the air to form strontium carbonate (SrCO3).
Safety
editStrontium hydroxide is a severe skin, eye and respiratory irritant. It is harmful if swallowed.
References
edit- 1 2 Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). Boca Raton, Florida: CRC Press. pp. 4–88, 4–130, 5–36, 6–161. ISBN 9781498754293.
- 1 2 3 4 5 Ehrlich, P. (1963). "17. Alkaline Earth Metals - Strontium Hydroxide". In Brauer, Georg (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1. Translated by Riley, Reed F. (2 ed.). New York, NY: Academic Press. p. 935. Retrieved 18 June 2026.
- ↑ "Materials Data on Sr(HO)2 by Materials Project". legacy.materialsproject.org. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA: LBNL Materials Project. doi:10.17188/1278328. OSTI 1278328. DOE Contract AC02-05CH11231, mp-625184. Retrieved 18 June 2026.