Plaster of Paris is made by heating the mineral gypsum. When gypsum is heated to about 150degC it losses water and produces the powder, plaster of Paris. Hemihydrate Calcium Sulfate(2CaSO4.H2O) is commonly known as plaster of paris. It is formed by heating gypsum.

Plaster of Paris is obtained by calcining gypsum.

Calcining:
Calcining is a process of heating a substance to a high temperature to bring about a thermal decomposition or phase transition. In the case of gypsum, calcining involves heating the mineral to a temperature of about 150°C - 190°C (302°F - 374°F).

Gypsum:
Gypsum is a naturally occurring mineral composed of calcium sulfate dihydrate (CaSO4·2H2O). It is a soft and white sedimentary rock that can be found in various parts of the world. Gypsum is commonly used in the construction industry as a building material due to its fire-resistant and sound-absorbing properties.

Plaster of Paris:
Plaster of Paris is a white powder obtained by heating gypsum. When mixed with water, it forms a paste that can be molded into various shapes and then hardens into a solid material. Plaster of Paris is widely used in construction, art, and medical applications.

How is Plaster of Paris obtained?
The process of obtaining Plaster of Paris involves the following steps:

1. Mining: Gypsum deposits are mined from the earth using various mining techniques. The mineral is extracted from quarries or underground mines.

2. Crushing and Grinding: The mined gypsum is crushed into smaller pieces and then ground into a fine powder. This powder is known as raw or natural gypsum.

3. Calcining: The raw gypsum powder is then heated in a calcination kiln or oven to remove the water content. During calcination, the calcium sulfate dihydrate is converted into calcium sulfate hemihydrate, also known as Plaster of Paris. The water molecules are driven off, leaving behind a dry powder.

4. Grinding and Packaging: The calcined Plaster of Paris is further ground into a fine powder to improve its consistency and reactivity. It is then packaged and ready for use.

Properties and Applications of Plaster of Paris:
Plaster of Paris has several properties and applications, including:

1. Setting Time: Plaster of Paris has a relatively fast setting time, making it ideal for casting and molding applications. It can harden within a few minutes to a few hours, depending on the specific formulation.

2. Workability: The paste formed by mixing Plaster of Paris with water has good workability, allowing it to be easily molded into various shapes and forms.

3. Strength: Once hardened, Plaster of Paris exhibits good strength and durability. It can be used for creating decorative elements, sculptures, and architectural details.

4. Medical Uses: Plaster of Paris is commonly used in orthopedics for making casts to immobilize and support fractured bones during the healing process.

5. Construction Applications: Plaster of Paris is used in the construction industry for making decorative elements, such as cornices, ceiling roses, and architectural moldings. It is also used for creating smooth and even surfaces on walls and ceilings.

In conclusion, Plaster of Paris is obtained by calcining gypsum, a naturally occurring mineral. The calcination process involves heating gypsum to remove the water content, resulting in the formation of Plaster of Paris. This versatile material finds applications in construction, art, and medicine due to its unique properties.

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