June 17, 2024
Calcium Sulphate

Calcium Sulphate: An Important Chemical Compound

Calcium sulphate is an inorganic compound with the chemical formula CaSO4. It is a widely used chemical compound with applications across various industries. In this article, we will discuss in detail about calcium sulphate, its various forms, properties, uses and applications.

Forms of Calcium Sulphate

Calcium sulphate exists in different hydrated forms depending on the number of water molecules attached to it. The main forms are:

Calcium Sulphate Dihydrate (Gypsum)

Calcium sulphate dihydrate, commonly known as gypsum, is the most common form that is found naturally. It has a chemical formula of CaSO4.2H2O and contains two water molecules for every one molecule of calcium sulphate. Gypsum is a soft sulfate mineral and is the chief mineral in many sedimentary evaporite deposits.

Calcium Sulphate Hemihydrate

When gypsum is heated above 100 degree Celsius, it loses 3⁄4 of its chemically combined water and forms calcium sulphate hemihydrate, which has the chemical formula of CaSO4.1/2H2O. It contains half the amount of water compared to gypsum. It is less soluble in water than gypsum. Plaster of Paris is a form of calcium sulphate hemihydrate.

Anhydrous Calcium Sulphate

Further heating gypsum at temperature above 280 degree Celsius results in anhydrous calcium sulphate, which has no chemically bound water molecules with a formula CaSO4. It is not commonly found in nature.

Properties and Uses

Calcium sulphate has various important properties that make it suitable for many applications across industries. Some of the key properties and uses are discussed below:

Strength and Hardness: When mixed with water, calcium sulphate hemihydrate forms calcium sulphate dihydrate which sets into a hard material. This property allows its use in construction sector for making plaster, cement and cement boards.

Dimensional Stability: Calcium sulphate sets material maintains its dimensional stability and does not shrink after setting. This makes it suitable for making molds, casts and other products where shape retention is important.

Porosity: The set material obtained from calcium sulphate has minute pores which allow it to be easily coated or receive color, making it suitable for making artistic objects and decorations.

Non-Combustibility: Calcium sulphate is non-flammable and does not support combustion, thus making it a preferred material for fireproofing applications in construction.

Other uses of calcium sulphate include manufacturing of wallboards, manufacturing of cement, production of stucco and joint compound used during drywall installation, refractory cement production, manufacture of ceramic tiles etc. Its dehydrate form gypsum also finds use as a soil conditioner in agriculture.

Applications in Key Industries

Given below are some important applications and uses of calcium sulphate in major industries:

Construction Industry

Calcium sulphate is one of the most widely used inorganic materials in construction sector. Plaster of Paris obtained from calcium sulphate hemihydrate is used for decorative plasterwork, making casts and moulds. Calcium sulphate also forms a key component of wallboards, ceiling tiles, cement boards etc. It is also used as an additive in cement and concrete for specific properties.


The dihydrate form gypsum finds varied applications in agriculture. It is used as a soil conditioner and amendment to improve soil texture and fertility. Addition of gypsum helps reclaim sodic soils and increase infiltration of water. It is also used as a fertilizer and in hydroponics systems.

Ceramics Industry

Calcium sulphate find applications in manufacturing of ceramic tiles, pottery and porcelain goods. It acts both as a binder during shaping as well as contributes to the fired body in vitrified products. The sulphate ion also participates in the formation of ceramic glazes.

Pharmaceutical Industry

Calcium Sulphate is used as a source of calcium and sulphate in pharmaceutical formulations. It is commonly present as a inactive ingredient in tablet coatings, as a disintegrating agent and as a drying agent in powder formulations. Its set plaster forms are also used in orthopedic casts and splints.

In this article, we discussed the importance of calcium sulphate compound, its various forms, key properties and wide ranging applications across industries like construction, agriculture, ceramics and pharmaceuticals. Calcium sulphate is a multipurpose inorganic compound with diverse uses. Its properties of strength, hardness, porosity and dimensional stability have made it an integral part of many industries.