Critical Point
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The critical point (critical temperature and critical pressure) is that above which there is no longer a boundary between liquid and gas.
A substance above its critical point is always in the gaseous state.
At temperatures below the critical point, all types of refrigerant in pressure containers exhibit both a liquid and a gas phase, for example there is a layer of gas above the liquid.
As long as both liquid and gas are present in the container, the pressure is governed by ambient temperature. Refer to REFRIGERANT R134A VAPOR PRESSURE TABLE "vapor pressure table".
NOTE:
Different types of refrigerant are never to be mixed. Only the refrigerant designated for the corresponding A/C system may be used.