Is Strontium Carbonate Soluble in Water? — A Short Overview

Strontium carbonate (SrCO₃) is a white ionic solid used widely as a colorant precursor (strontium for red flames), in ceramics, glass, and other industrial applications. When people ask “is it soluble in water?” the short answer is: no — it is sparingly soluble, but the measured solubility depends strongly on the conditions (especially whether the water is in contact with atmospheric CO₂).

What “sparingly soluble” means for SrCO₃

At 25 °C, SrCO₃ dissolves only a little in pure water because the dissolution equilibrium

SrCO₃(s) ⇌ Sr²⁺(aq) + CO₃²⁻(aq)

has a very small equilibrium constant (low Ksp), so only trace amounts enter solution. Published Ksp and solubility values vary in the literature (different methods and experimental conditions), but they consistently show very low intrinsic solubility in CO₂-free water.

Typical measured values and why they differ

For water that has equilibrated with atmospheric CO₂, the carbonate ion is partially converted to bicarbonate and carbonic acid, which increases apparent solubility. One careful study reports a solubility of ≈ 42.7 mg·L⁻¹ (0.0427 g·L⁻¹) for water in equilibrium with air at 25 °C.

For CO₂-free water (no dissolved atmospheric CO₂), the same study gives a much lower solubility of ≈ 8.95 mg·L⁻¹ (0.00895 g·L⁻¹) at 25 °C. This shows how CO₂ drives additional dissolution by converting CO₃²⁻ to HCO₃⁻.

Solubility-product (Ksp) values reported in reference tables vary (different compilations show values in the 10⁻¹⁰ to 10⁻⁹ range), but all indicate a very low solubility consistent with the numbers above.

Practical implications

In neutral or basic pure water, expect only milligrams per liter of SrCO₃ to dissolve — it is effectively insoluble for many practical purposes.

In acidic solutions, SrCO₃ reacts with acid to form soluble strontium salts and release CO₂ (so it is readily converted to soluble forms when acid is present).

In carbonated or CO₂-containing waters, apparent solubility increases because carbonate equilibria shift, an important point when measuring or using SrCO₃ in aqueous systems.

Safety and handling notes (brief)

Strontium carbonate is handled routinely in industrial and laboratory settings. It is not highly toxic, but like any fine powder it should be handled to avoid dust inhalation and contact — follow the supplier’s Safety Data Sheet for PPE, storage and disposal instructions.