If I have 1 ft3 of ammonia at 15 psia, 60 F how much mass is that?
Ammonia
Psat = 107.64 psia at 60 F so superheated vapor.
v = 21.5641 ft3/lbm under subheading 15 psia
m = V/v = 1 ft3/21.5641 ft3/lbm = 0.0464 lbm