Strontium Hydroxide
Properties
| State | Solid at room temperature (typically as octahydrate) |
| Color | White crystalline solid (deliquescent) |
| Solubility | Soluble in water — strongly temperature-dependent: 1.8 g/100 mL at 20°C, 21.8 g/100 mL at 90°C |
| Melting Point | 375°C (anhydrous); octahydrate loses water above 100°C |
| Boiling Point | 710°C (decomposes to SrO) |
About Strontium Hydroxide
Strontium hydroxide, Sr(OH)2 (121.632 g/mol), is the alkaline earth hydroxide that sits between calcium hydroxide and barium hydroxide on every periodic-trends graph students draw. It is a strong base — fully dissociated in dilute solution to give Sr2+ and 2 OH⁻ — but its solubility behavior is the more interesting property. Unlike most salts, Sr(OH)2 follows the alkaline earth pattern of increasing solubility with rising temperature: about 1.8 g/100 mL at 20°C climbing past 21 g/100 mL at 90°C. The compound usually crystallizes from water as the octahydrate Sr(OH)2·8H2O, which loses water stepwise (8H2O → monohydrate → anhydrous) when heated above 100°C and finally decomposes to SrO above 700°C. The defining industrial use is sugar beet refining via the Steffen process: hot sugar liquor is dosed with Sr(OH)2, which precipitates an insoluble strontium saccharate complex, the cake is filtered off, and CO2 is bubbled through to liberate sucrose and regenerate SrCO3 for recycling. The Steffen process recovers an extra 5–8% sugar from molasses that would otherwise be sold as low-value cattle feed. Other uses include lubricating-grease thickeners (strontium soaps tolerate higher operating temperatures than calcium or lithium soaps) and as a precursor to other strontium chemicals.
Where you'll encounter it
If you've ever wondered why beet sugar producers can extract sucrose down to lower concentrations than cane sugar refiners, the Steffen process running on strontium hydroxide is the reason. The German sugar industry deployed it heavily through the 20th century and a handful of European refineries still run it. In the lubrication world, if you've serviced heavy industrial gearboxes or aluminum hot-rolling mills running above 200°C, the grease in those housings is often a strontium-complex soap thickener built on Sr(OH)2 — it holds structure at temperatures where lithium-12-hydroxystearate softens and slumps. Lab-scale, anyone preparing reference solutions of saturated strontium hydroxide for CO2 absorption (Sr(OH)2 + CO2 → SrCO3 + H2O is the basis of one of the older methods for measuring respiration in plant chambers) deals with the same temperature-dependent solubility quirk that makes the Steffen process work.
Common Uses
- Sucrose recovery from beet molasses via the Steffen process (strontium saccharate precipitation)
- Thickener for high-temperature strontium-complex lubricating greases used in steel and aluminum mills
- Precursor for synthesizing strontium ferrites used in permanent magnets
- Stabilizer added to PVC and other polymers to scavenge HCl during processing
- Precipitating reagent for CO2 in plant respiration and gas-stream analysis (forms SrCO3)
- Source of Sr2+ in specialty optical glass and ceramic glaze formulations
- Laboratory base for titration of weak organic acids when carbonate-free strong base is needed
Safety Information
GHS Category 1B skin corrosive (H314) and serious eye damage (H318). Causes chemical burns on contact and severe respiratory tract irritation if inhaled as dust or mist. No specific OSHA PEL for strontium hydroxide; treat as an alkaline corrosive and follow PEL of 2 mg/m³ used for caustic potash and caustic soda. Saturated solutions have pH around 13–14. Store sealed under dry conditions because the octahydrate slowly absorbs CO2 from air to form SrCO3 surface coating, which degrades the assay. Spill response is the same as for NaOH: neutralize with dilute acetic acid after physical containment, then flush with copious water. Ingestion produces severe esophageal and gastric burns — get medical attention immediately, do not induce vomiting.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.