Is it possible to calculate the water volume in gallons if you know the pressure, temperature, and cubic footage of the gas such as air?

I have an application where I know that the volume is 505 cubic feet of air at 6000 psig and temperature would be 70 degrees F., in a cylinder but need to know what the water volume of the cylinder.Can this be calculated without having the diameter and length of the cylinder by using the items I do know? I have found examples online such as 3.14 x (radius* x radius*) x Depth = Cubic Feet.

then Cubic Feet x 7.48 = Total Gallons, but this number is way too high based upon a cylinder that I do know the measurements of. I have also used a different calculation: WP of Cylinder in PSIG divide by 14.7= ATM +1 = ATA (pressure in atmospheres absolute) then Cubic foot rating of cylinder divide by ATA above = actual liquid volume of cylinder in gallons, which is closer to the correct value but still too low based upon the manufacturers data sheet of the cylinder. The cylinder that I do know the dimensions of is a 510.37 cubic foot gas (air) volume at 6000 psig it is 52" long and 9.4" diameter with an actual liquid volume of 1.47 gallons. Using the first method I get 26,979.43 gallons, which is way too high and obviously wrong. Using the second closer calculation I get 1.247 which is close to the manufacturer's specification of 1.47 gallon but still not accurate. Does anyone have an example of how to do this if it is possible? Should I be using a compression factor in the calculation somehow to get an accurate result?

**Edited by tm1274, 22 August 2013 - 03:57 PM.**