What was the principal use of calcium sulfate in hospitals

Answer: Plaster of paris cast

Explanation:

Calcium sulphate, CaSO4, is a odourless, white powder or a colourless, crystallines solid. It exists in as different hydrates: anhydrous (CaSO4), dihydrate (CaSO4.2H2O) and hemihydrate (CaSO4. 1/2 H2O).

The main use of calcium sulphate, specifically in hospitals, is plaster of paris cast. The powdered form of CaSO4 can be formed into a moldable paste upon hydration.