'Ammonia in an aqueous solution can be expelled by boiling' - how exactly is this done, how would one do it in a lab?

It's just distillation. But a particularly stinky one (ammonia vapors are smelly and dangerous! Make sure to read the Ammonia MSDS (click here!) before starting.).

 

So, in the lab, you certainly do it in a fume hood... but you may want to ask for some extra advice.

But I wouldn't know any reason why any ordinary distillation setup would not work.

 

NB: the product will not be anhydrous ammonia. It will contain water vapor, but at a lower concentration than in the liquid phase.

 

The bigger question is: what do you need the ammonia gas for? Do you need to store it (I hope not!)?

Make sure to keep the temp as low as you can and still collect ammonia. You want to keep the vapor pressure of water as low as you can.

does it not redissolve in the water when you condense the water?

 

and i don't actually need it for anything i was just reading and was curious

If you just want the water, just boil it and you don't need a distillation apparatus (you'll need that much more ventilation though). The distillation apparatus is to capture the more volatile substance, which in this case would be the ammonia.