More thanof likely you have R134A freon, if you do have a slow leak, I suggest that you have a professional inject a yellow dye detected by a black light. If you have a visable leak it will show with an inspection, and repair properly.
You'll have to take it in for service to do this. In order to buy freon you need to have a license and the tools to install it.
Call around to local shops and ask for a cost to charge your system. I know near me there have been a lot of coupons in the paper for this service. It's best to let a professional do it.
〉 Answered on Jul 9th, 2012 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines