Ok, everything's much clearer now. Thanks so much for your help! Great forum you guys got here, I think I might get into this hobby in the future!

Hi all. I'm working on a project that involves filling a chamber with CO2. I came across the thread with the formula for calculating chamber pressure, 4200/cv. This is just what I needed, but I would like to know, where does the number 4200 come from? Can anyone help me out? Thanks in advance.