Calcium sulfate
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| Calcium sulfate | |
|---|---|
| Image:Calcium sulfate hemihydrate.jpg | |
| General | |
| Other names | Plaster of Paris Gypsum Drierite® whiskers crystal |
| Molecular formula | CaSO4 |
| Molar mass | 136.142 g/mol (anhydrous) |
| Appearance | white solid see also text |
| CAS number | [7778-18-9] (anhydrous) |
| Properties | |
| Density and phase | 2.96 g/cm3, solid |
| Solubility in water | 0.24 g/100 ml (20 °C) |
| Melting point | 1460°C (anhydrous) |
| Refractive Index | 1.57 |
| Mohs hardness | 3.5 |
| Structure | |
| Coordination geometry | ? |
| Crystal structure | orthorhombic |
| Thermodynamic data | |
| Standard enthalpy of formation ΔfH°solid | -1434.5 kJ/mol |
| Standard molar entropy S°solid | ? J.K–1.mol–1 |
| Heat of fusion | 205.668 |
| Specific Heat Capacity | 0.732324 J/g-°C (anhydrous) |
| Safety data | |
| PEL-TWA (OSHA) | 15 mg/m3 |
| RTECS number | WS6920000 |
| NFPA 704 | |
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other cations | Magnesium sulfate Strontium sulfate |
| Related desiccants | Calcium chloride Magnesium sulfate |
| Related compounds | Plaster of Paris Gypsum |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references | |
Calcium sulfate is a common laboratory and industrial chemical. In its anhydrous form, it is sold as a laboratory desiccant under the name Drierite®. The hemihydrate is better known as plaster of Paris, while the dihydrate occurs naturally as gypsum. Depending on the method of calcination of calcium sulfate dihydrate specific hemihydrates are obtained: alpha-hemihydrate and beta-hemihydrate. Alpha-hemihydrate crystals are more prismatic than beta-hemihydrate crystals and when mixed with water form a much stronger and harder superstructure.
Natural, unrefined calcium sulfate is a translucent, crystalline white rock. After being heated and crushed into a powder, it is often used as the coagulant in soy processing, such as making tofu. Its most common use is in blackboard chalk.
[edit] External links
- International Chemical Satefy Card 1215
- NIOSH Pocket Guide to Chemical Hazards
- Drierite information from its manufacterer
he:סידן גופרתי lv:Kalcija sulfāts pl:Siarczan wapnia ru:Сульфат кальция th:แคลเซียมซัลเฟต uk:Сульфат кальцію zh:硫酸钙
