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. No OSHA PEL is established for strontium compounds, but ACGIH treats soluble strontium salts as nuisance dust at 10 mg/m³ TWA. 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.