What is pure calcium carbonate?
1. Definition and Chemical Composition
Pure calcium carbonate (CaCO₃) is an inorganic chemical compound composed of calcium (Ca²⁺) ions and carbonate (CO₃²⁻) ions in a 1:1 molar ratio. It is one of the most abundant natural minerals on Earth and serves as a fundamental building block in geological, biological, and industrial processes.
Chemical Formula: CaCO₃
Molecular Weight: 100.09 g/mol
Crystal Structures: alcite (trigonal,moststable,form),Aragonite(orthorhombic, metastable),Vaterite (rare, hexagonal)
2. Physical and Chemical Properties
Pure calcium carbonate exhibits several key characteristics that determine its applications:
Description
| Appearance | Fine white powder |
| Density | 2.71 g/cm³ (calcite), 2.93 g/cm³ (aragonite) |
| Melting Point | Decomposes at ~840°C (forms CaO + CO₂) |
| Solubility | Nearly insoluble in water (0.0014 g/100 mL at 25°C), but dissolves in acids (e.g., HCl) with effervescence (CO₂ release) |
| PH (in water) | 9-10 (weakly alkaline) |
| Refractive Index | 1.49 (calcite), 1.53 (aragonite |
3. Industrial and Commercial Uses
Pure calcium carbonate is widely utilized across multiple industries due to its:
Low cost
Non-toxicity
Alkalinity
High brightness & opacity
Industry
Applications
| Pharmaceuticals | Antacids (Tums), calcium supplements |
| Food & Beverage | Additive (E170), dough conditioner, acidity regulator |
| Construction | Cement, mortar, limestone aggregates |
| Paper & Pulp | Filler & coating to improve brightness |
| Plastics & Rubber | Reinforcing agent, improves stiffness |
| Agriculture | Soil PH adjuster (lime substitute) |
| Environmental | Flue gas desulfurization (removes SO₂) |
| Cosmetics | Bulking agent in toothpaste, face powders |
4. Differences Between Pure and Commercial Grades
Pure calcium carbonate (Lab/Pharma Grade):
≥99% purity, minimal impurities (e.g., Mg, Fe, Sr).
Used in sensitive applications (medicine, food).
Industrial/GCC Grade:
90-98% purity, may contain silica, clay, or metal traces.
Cheaper, used in construction, paints, and plastics.
5. Safety and Handling
Non-toxic (GRAS status by FDA).
Dust inhalation risk (may irritate lungs in powder form).
Incompatible with strong acids (releases CO₂ gas).
6. Analytical Testing Methods
To verify purity, techniques include:
X-ray Diffraction (XRD) – Identifies crystal structure.
Thermogravimetric Analysis (TGA) – Measures decomposition temperature.
Titration – Quantifies Ca²⁺ content via EDTA complexation.
Pure calcium carbonate is a versatile compound with critical roles in nature and industry. Its unique properties—alkalinity, low solubility, and abundance—make it indispensable in healthcare, manufacturing, and environmental management. Understanding its forms, production methods, and applications helps optimize its use across different sectors.
