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Strontium Carbonate

SrCO3 salt
Molar Mass
147.628 g/mol
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Properties

StateSolid
ColorWhite
SolubilityPractically insoluble in water (11 mg/L at 25 °C, Ksp 5.6 x 10 -10); dissolves in dilute acids with CO2 evolution
Melting Point1494 °C (under 60 atm CO2); decomposes to SrO and CO2 above 1340 °C in air

About Strontium Carbonate

Strontium carbonate (SrCO3, 147.628 g/mol) is the dominant commercial strontium compound and the source from which essentially every other strontium chemical is derived. Mineralogically it occurs as strontianite — named after the Scottish village of Strontian on Loch Sunart, where Adair Crawford and William Cruickshank first noted it as a distinct mineral in 1790, and where Humphry Davy isolated metallic strontium by electrolysis of fused SrCl2 in 1808. Crystallographically SrCO3 is isostructural with aragonite (orthorhombic, Pmcn), one of CaCO3's two main polymorphs, with Sr 2+ substituting for Ca 2+ in the same nine-coordinate site. The Ksp of 5.6 x 10 -10 makes it essentially insoluble in pure water (11 mg/L at 25 °C), but it dissolves readily in dilute mineral acids with effervescence of CO2 — the test-tube reaction SrCO3 + 2HCl -> SrCl2 + H2O + CO2 is identical in form to limestone with vinegar. The compound's old commercial dominance — for decades, the largest single use was as the X-ray-absorbing 'getter' material in the leaded face-plate glass of color cathode-ray-tube televisions — vanished essentially overnight in the early 2000s with the LCD/plasma transition. The current uses are smaller in volume but more diverse: hard ferrite permanent magnets (SrFe12O19) for loudspeakers and DC motors, the crimson-red emitter in pyrotechnic flares and fireworks (Sr 2+ resonance line at 605.6 nm), iridescent ceramic glazes, and as the precursor to other strontium chemistry including SrO, Sr(NO3)2, and SrTiO3.

Where you'll encounter it

If you have watched a Fourth of July fireworks display and seen the deep crimson stars in the burst — that color is the 605.6 nm atomic resonance emission of excited Sr 2+ ions, almost always sourced from strontium carbonate or strontium nitrate in the pyrotechnic composition. Strontium chloride and oxalate work too but the carbonate is cheapest and stable to store. In a loudspeaker disassembled on the workbench, the heavy black ceramic ring magnet behind the voice-coil is strontium ferrite (SrFe12O19) — made by sintering SrCO3 with Fe2O3 at 1300 °C in air to form the hexagonal magnetoplumbite structure, then powdering it, pressing the powder in an oriented magnetic field, and sintering again to produce the final ceramic magnet. Strontium ferrite has slightly higher coercivity than the barium analog, which is why it dominates the loudspeaker, refrigerator-magnet, and small-DC-motor markets. Glaze chemists use SrCO3 as a low-toxicity replacement for lead and barium in art-pottery glazes, where it gives a satin to matte finish at 1180 to 1240 °C and contributes the slight iridescence prized in some Raku and Mediterranean styles.

Common Uses

  • Hard ferrite permanent magnet manufacture as SrFe12O19 for loudspeakers, DC motors, and refrigerator magnets
  • Crimson-red color emitter in pyrotechnic flares, fireworks, and railroad signal flares via the 605.6 nm Sr 2+ resonance line
  • Iridescent matte ceramic glazes at 1180 to 1240 °C as a low-toxicity replacement for lead and barium
  • Precursor for production of strontium oxide, strontium nitrate, and strontium titanate
  • Toothpaste additive in desensitizing formulations as a desensitizing strontium source
  • Cathode-ray-tube faceplate glass X-ray getter (historical, obsolete since the early 2000s LCD transition)
  • Iron-oxide-pigment modifier and color stabilizer in ceramic and glass pigments
  • Production of strontium aluminate phosphors used in long-afterglow glow-in-the-dark paints

Safety Information

Low systemic toxicity. GHS: H315 (skin irritation, Category 2), H319 (serious eye irritation, Category 2A). No OSHA PEL specifically for strontium compounds; ACGIH does not list a TLV for strontium carbonate. Stable strontium is chemically similar to calcium and is incorporated into bone with about 0.04% of dietary intake retained — pharmacologically used as strontium ranelate for osteoporosis. The dust is a moderate irritant to skin, eyes, and respiratory tract; standard nuisance-dust PPE (safety glasses, dust mask) is adequate. Critically, the radioactive isotope Sr-90 (a high-yield 235U fission product, half-life 29 years) is a wholly different hazard — it is a bone-seeking beta emitter responsible for much of the long-term radiation burden from atmospheric nuclear weapons testing, and its chemistry is identical to natural Sr but its biological hazard is severe. Stable SrCO3 from a chemical supplier is not radioactive.

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.

Constituent Elements

Sr — Strontium C — Carbon O — Oxygen

Frequently Asked Questions

What is the molar mass of strontium carbonate?
SrCO3 has a molar mass of 147.628 g/mol: Sr (87.62) + C (12.011) + 3 O (3 x 15.999 = 47.997). Strontium has four stable isotopes (84Sr, 86Sr, 87Sr, 88Sr) with 88Sr at 82.6% abundance, which gives the IUPAC standard atomic weight of 87.62 — the 87Sr/86Sr ratio is the basis for strontium isotope geochemistry used to trace the origins of archaeological human and animal remains by their childhood drinking water.
Why does strontium produce red fireworks?
When a strontium compound is heated to flame temperatures (1500 to 2000 °C in a typical pyrotechnic), thermal energy excites valence 5s electrons to higher energy levels. As the excited electrons relax back to the ground state, they emit photons at characteristic wavelengths — the dominant Sr 2+ emission is at 605.6 nm (deep red), with secondary lines at 460 nm and 670 nm contributing minor blue and crimson components. The result is the crimson-red color that distinguishes strontium-based pyrotechnics from the orange of calcium (606 nm but with strong yellow Ca emissions diluting the red), the green of barium (524 nm), and the blue of copper (450 nm). SrCO3, Sr(NO3)2, and SrCl2 are the most common red-color formers in flare formulations; the choice depends on the binder system and burn-rate requirements.
How are ferrite magnets made from SrCO3?
Strontium ferrite SrFe12O19 (hexagonal magnetoplumbite structure, M-type) is made by ball-milling SrCO3 and Fe2O3 in 1:6 molar ratio, then calcining the mixture at 1200 to 1300 °C in air for 4 to 8 hours: SrCO3 + 6 Fe2O3 -> SrFe12O19 + CO2. The resulting black ceramic chunks are crushed and milled into single-domain particles roughly 1 micrometer across, mixed with a small amount of binder, pressed in an oriented magnetic field of 0.8 to 1.2 T (this aligns the c-axis of each crystallite with the field direction so the final magnet has a defined easy axis), and sintered at 1180 to 1230 °C to densify. Strontium ferrite is preferred over the barium analog (BaFe12O19) for slightly higher coercivity (~300 kA/m vs 270 kA/m) and lower raw-material cost; together they account for over 70% of all permanent magnets sold by mass worldwide.