Strontium Chloride
Properties
| State | Solid (white crystalline powder; hygroscopic) |
| Color | White |
| Solubility | Very soluble in water (538 g/L at 20°C); slightly soluble in ethanol |
| Melting Point | 874°C (anhydrous); 61°C (hexahydrate) |
| Boiling Point | 1250°C |
About Strontium Chloride
Strontium chloride is a white crystalline salt with formula SrCl2 (158.526 g/mol), usually shipped as the hexahydrate SrCl2·6H2O because the anhydrous form is aggressively hygroscopic. Two things make it interesting outside the inorganic textbook: the Sr2+ ion fluoresces a brilliant crimson when excited in a flame (peak emission around 605–680 nm from atomic Sr lines plus the SrCl molecular bands), and Sr2+ has an ionic radius close enough to Ca2+ to substitute for calcium in several biochemical contexts. Solubility is high — 538 g/L at 20°C — and aqueous solutions are nearly neutral. Industrially it shows up as the red colorant in marine flares, road flares, and the deep-red stars in pyrotechnic shells, where it is usually combined with potassium perchlorate or potassium chlorate as the oxidizer and shellac or red gum as the fuel/binder. Old Sensodyne formulations relied on 10% strontium chloride hexahydrate to occlude open dentinal tubules and reduce hypersensitivity, though most current formulations have moved to potassium nitrate or stannous fluoride. Sr-90 cleanup chemistry, sulfate gravimetry, and bacterial transformation protocols round out the working uses.
Where you'll encounter it
If you've ever lit a road flare on the shoulder after a flat tire, that deep red glow is mostly strontium chloride or strontium nitrate burning with a chlorate or perchlorate oxidizer. In a molecular biology lab, SrCl2 is the reagent you reach for when the standard CaCl2 heat-shock transformation of E. coli isn't giving you the colony counts you need — Sr2+ permeabilizes the outer membrane slightly differently and sometimes recovers a finicky strain. Analytical chemists running gravimetric sulfate determinations as an alternative to barium chloride (when Ba waste disposal is a hassle) precipitate SrSO4 instead. And if you've ever seen the old Sensodyne Original Flavor tube with the orange-red label, the active ingredient panel listed strontium chloride hexahydrate at 10%.
Common Uses
- Crimson colorant in road flares, marine signal flares, and pyrotechnic shell stars
- Active ingredient in older desensitizing toothpaste formulations (10% hexahydrate)
- Alternative to CaCl2 for heat-shock transformation of competent E. coli
- Precipitating reagent for gravimetric sulfate determination as SrSO4
- Co-precipitation carrier for removing radioactive Sr-90 from contaminated solutions
- Source of Sr2+ for substituting calcium sites in bone mineralization studies
- Glass and ceramic colorant for cathode ray tube faceplates (legacy use)
Safety Information
GHS Category 2 skin and eye irritant (H315, H319). LD50 oral rat is roughly 2,250 mg/kg, so acute toxicity is low for an inorganic salt. Soluble strontium salts are handled as a nuisance dust rather than a specifically toxic aerosol, so airborne control is about dust generation, not systemic toxicity. The hexahydrate is hygroscopic and clumps in humid storage, so keep the bottle tightly capped with desiccant. Chronic high-dose exposure interferes with calcium metabolism and can cause rachitic-type bone changes in animals, though dietary intake at typical pyrotechnic or pharmaceutical levels is not a concern. Strontium-90 from nuclear fallout is the radiological hazard people confuse this stable isotope salt with — they are unrelated.
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. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.