Name a drying agent for ammonia gas.

1. In the laboratory preparation method, the Ammonia gas(${\mathbf{NH}}_{\mathbf{3}}$) contains water vapor.
2. So for removing water vapor, is allowed to pass through a drying tower that contains Quick lime or Calcium Oxide($\mathit{C}\mathit{a}\mathit{O}$).
3. Thus, Calcium oxide absorbs the water content and pure Ammonia gas is obtained.
4. So the drying agent is Calcium oxide or quick lime.