Here is a detailed explanation of the properties o...

Here is a detailed explanation of the properties of Calcium Sulphate (CaSO₄), a widely used inorganic compound found in both natural and industrial forms. It is most commonly seen as gypsum (CaSO₄·2H₂O), but also exists in hemihydrate (CaSO₄·0.5H₂O) and anhydrite (CaSO₄) forms. 🧪 Calcium Sulphate (CaSO₄) – Detailed Properties 🔹 1. Basic Identification Property Value Chemical Name Calcium Sulphate Chemical Formula CaSO₄ Common Forms Gypsum (CaSO₄·2H₂O), Plaster of Paris (CaSO₄·0.5H₂O), Anhydrite (CaSO₄) Molar Mass 136.14 g/mol (CaSO₄) 172.17 g/mol (gypsum) CAS Number 7778-18-9 🔹 2. Physical Properties Property Description Appearance White or colorless crystalline solid Odor Odorless Taste Slightly salty Density 2.96 g/cm³ (anhydrite), 2.32 g/cm³ (gypsum) Melting Point Decomposes at ~1, 460°C (anhydrite) Boiling Point Not applicable (decomposes) Solubility in Water Slightly soluble (~0.2 g/100 mL at 25°C) Solubility in Acids Soluble in hydrochloric and nitric acid Color White to off-white Crystal Structure Orthorhombic (anhydrite), Monoclinic (gypsum) 🔹 3. Chemical Properties Property Description Nature Inorganic salt pH ~6–7 in water (neutral to slightly acidic) Reactivity Stable under normal conditions, reacts slowly with strong acids Decomposition On heating, gypsum loses water to form hemihydrate (Plaster of Paris), and then anhydrite Hygroscopicity Gypsum is non-hygroscopic; hemihydrate is hygroscopic and sets when mixed with water 🔹 4. Types / Forms Form Chemical Formula Common Name Description Dihydrate CaSO₄·2H₂O Gypsum Naturally occurring form, soft and hydrated Hemihydrate CaSO₄·0.5H₂O Plaster of Paris Made by heating gypsum to 150°C Anhydrous CaSO₄ Anhydrite Completely dehydrated, hard, and dense 🔹 5. Industrial & Practical Applications Application Area Use of Calcium Sulphate Construction Plaster of Paris (walls, ceilings), gypsum boards Agriculture Soil conditioner (improves water penetration), source of calcium and sulfur Medical Bone graft materials, orthopedic casts (Plaster of Paris) Food Industry (E516) Used as a firming agent in tofu, yeast nutrient, flour treatment agent Cement & Concrete Retarder in Portland cement Ceramics & Molding Molding medium in fine arts and crafts Laboratory Use Desiccant in its anhydrous form 🔹 Mechanical & Structural Properties Property Description Mohs Hardness ~2 (Gypsum – soft mineral) Compressive Strength Moderate in set form (Plaster of Paris sets rigidly) Thermal Conductivity Low; used as insulation material in building boards Fire Resistance Excellent; gypsum releases water vapor when heated, acting as a fire barrier 🔹 Safety and Handling Aspect Description Toxicity Non-toxic under normal use Inhalation Fine dust can irritate respiratory tract Skin Contact Mild irritation possible during long exposure Environmental Impact Non-hazardous; large deposits used for eco-friendly applications like soil remediation ✅ Summary Points Calcium sulphate is widely used in construction, agriculture, food, and medicine. Exists in three main forms: gypsum (dihydrate), plaster of Paris (hemihydrate), and anhydrite (anhydrous). Has low solubility, fire resistance, and biocompatibility. Safe for use in food and pharmaceuticals (E516 grade).