State the methods by which hydrated salts can be made anhydrous?

Hydrated salts can be made anhydrous by heating or by exposing to dry air.
For example, Glauber’s salt when exposed to dry air, water molecules get evaporated from it and powdery anhydrous sodium sulphate is formed.
$N{a}_{2}S{O}_4.10H_{2}O+Dryair\to N{a}_{2}S{O}_4+10H_{2}O$