Chemical agent and Drying agent

Chemical agent noun - An agent that produces chemical reactions.

Drying agent and chemical agent are semantically related. In some cases you can replace phrase "Drying agent" with "Chemical agent", this phrases are similar.

Drying agent noun - A substance that promotes drying (e.g., calcium oxide absorbs water and is used to remove moisture).

Chemical agent and drying agent are semantically related. You can use "Chemical agent" instead a noun phrase "Drying agent".