Web SDK set department programatically.

This is probably a dumb question, but I'm not finding the answer in the docs. 

If I have multiple clients, how do I set the the department, with the web sdk, so that chats get routed to the right agents?  Or so that the agent knows which client they may be answering questions for?

I see where to set the name and email, but department says it is not whitelisted. If that adds any clarification for anyone.