I wish it was that simple rb1957. Check out the extract below from Fundamentals of Cryogenic Engineering by Mukhopadhyay. This is based on the Epstein paper but doesn't seem to like large temperature differentials.
The saturation temperature at 1 psia is -104F. At 14 psia it is -29F. I think that the real gas law (compressibility drops below 0.9 at 114 psia and 63F) is probably more appropriate than cryo calculations.
