Overview
Calcium sulfate hemihydrate (CAS 10034-76-1 ), also known as gypsum hemihydrate, is a partially dehydrated calcium sulfate produced by controlled calcination of natural gypsum.
It reacts with water to form a rigid, dimensionally stable set mass, making it a core binder and setting agent across construction, industrial, and pharmaceutical manufacturing.
In building and construction, it is the primary binder in plaster, drywall compounds, and prefabricated gypsum boards, where controlled set time and surface hardness are critical.
Pharmaceutical manufacturers use it as a tablet diluent and binder, where its compressibility and inert profile support high-volume solid dosage production for various medications.
In pulp and paper operations, it functions as a filler and surface treatment agent to improve sheet formation, opacity, and printability for high-quality paper products.
Dental and orthopedic casting applications also rely on it for precision mold fabrication, where dimensional accuracy after setting is the primary requirement for the user.
The material is supplied as a fine white powder in both alpha and beta crystal forms, with alpha-hemihydrate offering higher density and compressive strength than the beta form.
Standard grades include USP , Ph. Eur. , and food-grade ( FCC ) for regulated applications, alongside technical and construction grades for industrial use.
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Physical Properties
| Density | 2.7 g/cm³ |
| Appearance | white or slightly off-white powder or granules |
| Color | White with a blue, gray or red hue |
| Form | Solid |
| Water Solubility | sets to hard mass when mixed with H2O [MER06]; g/100g solution H2O: 1.23 (0°C), 0.71 (25°C), 0.189 (100°C); solid phase, CaSO4 · 1/2H2O [KRU93] |
Safety & Handling
Warning GHS07 Hazard Statements H335 May cause respiratory irritation Precautionary Statements P261 Avoid breathing dust/fume/gas/mist/vapours/spray. P271 Use only outdoors or in a well-ventilated area. P319 Get medical advice/attention if you feel unwell. P405 Store locked up. P501 Dispose of contents/container in accordance with local regulations. P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing. P403+P233 Store in a well-ventilated place. Keep container tightly closed.
Trade & Regulatory
| WGK (Germany) | 1 |
Other Names
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Chemical Properties
- CAS Number
- 10034-76-1
- EC Number
- 600-067-1
- Mol. Weight
- 290.3
- Category
- Salts & Minerals