Below is a picture of a pressure gauge mounted on a Freon (R-134a) cylinder for precise recharging of air conditioning systems. It clearly shows a relation between Pressure and Temperature. Is this relation between P and T always true or it applies only to vapor pressure? If the bottle is filled with gas only, no liquid phase present, would the relationship still valid?
Now let's suppose to fill half of my bottle with liquid Freon at a temperature of 70F, seal it and I cool it off to -15F (note -15F is the boiling point at 14.7 PSI). What happens to its volume, vapor pressure, and boiling point?