I'm running a fermentation in Hungate tube, but I don't know how to calculate total gas volume. I can mesure gas pressure and I get that through this equation (Delta n) = (Delta P) .V / RT I can calculate number of gas moles, and after Vgas(l)=  (Delta n). 22.4. But the the V (in first equation) mean the total volume of tube containing medium or only the volume of head space (the space over the medium)?

Thank you!