Calcium sulfate dihydrate
| Formula | CaO4S*2H2O |
| Chemical formula | CaSO4*2H2O |
| Molar mass | 172.17 g/mol |
| Bulk Density | ~400 – 600 kg/m3 |
| CAS number | 10101-41-4 |
| HS Code | 28332990 |
| EC number | 231-900-3 |
| Storage | Without limitation |
| SDS | available |
| RTECS | EW4150000 |
| Odour | odourless |
| Form | solid |
| Color | colourless |
| p H | 7.0 (50 g/l 20 °C ) |
| Solubility in water | 2 g/l(20°C) |
| Thermal decomposition | >140°C |
| Assay | 98.0 – 102.0 | % | |
| Description | Conforms | ||
| Identification | Conforms | ||
| Solubility | Conforms | ||
| Appearance of solution | Conforms | ||
| Selenium | ≤ | 0.03 | % |
| Fluride | ≤ | 0.003 | % |
| Heavy metals | ≤ | 0.02 | % |
| Loss on ignition | 18.0 – 22.0 | % | |
| Loss on drying | ≤ | 23 | % |
Calcium sulfate dihydrate is a naturally occurring white crystalline inorganic compound commonly known as gypsum. It is widely used in construction materials, agriculture, and medical fields due to its excellent binding and moisture-retaining properties.
🏭⚗️ Production
Calcium sulfate dihydrate is mainly obtained from natural gypsum deposits through mining. It can also be produced industrially by hydrating calcium sulfate hemihydrate (plaster of Paris), a process that restores the two water molecules in the crystal structure. Additionally, it is generated as a byproduct in flue gas desulfurization during power plant operations.
🔬 Properties
The chemical formula is CaSO₄·2H₂O with a molar mass of approximately 172.17 g/mol. It appears as white or colorless crystals or fine powder with slight solubility in water. Upon heating, it loses water molecules in stages, first forming calcium sulfate hemihydrate and then the anhydrous form, which alters its physical properties. It is stable under normal storage conditions but can dehydrate in dry or heated environments.
🧪 Applications
Calcium sulfate dihydrate is extensively used to manufacture plaster and drywall panels due to its ease of shaping and quick setting when mixed with water. In agriculture, it acts as a soil conditioner, improving aeration and reducing soil compaction. It is also employed in dentistry and orthopedics for making molds and casts, benefiting from its biocompatibility and dimensional stability. Moreover, it serves as a food additive (E516) for controlling acidity.
⚠️ Safety
Generally, calcium sulfate dihydrate is considered non-toxic and safe for most uses. However, inhalation of fine dust particles can irritate the respiratory tract and mucous membranes, so adequate ventilation and protective masks are recommended during handling. Prolonged exposure to dust should be avoided, and the material must be stored in a dry environment to prevent premature dehydration and loss of functional properties.
