What is the Difference Between Calcium Sulfate and Plaster of Paris?

The main difference between calcium sulfate and Plaster of Paris lies in their chemical composition and physical properties. Calcium sulfate is an inorganic compound with the chemical formula CaSO4, while Plaster of Paris specifically refers to the hemihydrate form of calcium sulfate (CaSO4·0.5H2O) used in construction, art, and medical applications.

Some key differences between calcium sulfate and Plaster of Paris include:

• Chemical Composition: Calcium sulfate occurs in its hydrated forms, such as calcium sulfate dihydrate (CaSO4·2H2O), which is also known as gypsum. Plaster of Paris, on the other hand, is produced by heating gypsum to a temperature of about 150°C, turning it into calcium sulfate hemihydrate.
• Mode of Production: Gypsum, which is composed of calcium sulfate dihydrate, is a naturally occurring soft-sulfate mineral deposited from lake and sea water. Plaster of Paris is produced by heating gypsum to a high temperature, causing three-quarters of the crystallized water to evaporate.
• Physical Properties: Calcium sulfate is a white solid that is poorly soluble in water. When Plaster of Paris is mixed with water, it forms a solid that can be used for molding and shaping.
• Applications: Calcium sulfate has various applications in industry and is used to cause permanent hardness in water. Plaster of Paris is commonly used in medical laboratories and artistry for molding and casting, as well as in construction for false ceilings, wall surfaces, and fireproof agents.

Comparative Table: Calcium Sulfate vs Plaster of Paris

Here is a table comparing the differences between calcium sulfate and plaster of Paris:

Calcium sulfate is an inorganic compound with the chemical formula CaSO4 and can occur in various hydrated forms, including the dihydrate found in gypsum and the hemihydrate found in plaster of Paris. Plaster of Paris is a material containing calcium sulfate hemihydrates, which is prepared by heating gypsum to a temperature of about 150°C (120-180°C) and adding certain additives. The main difference between calcium sulfate and plaster of Paris lies in their chemical composition and physical properties.