Under normal atmospheric pressure, carbon dioxide does not have a liquid phase. When the temperature falls below -78.5º C or -109.3º F, the gas transforms directly into solid through deposition. In the other direction, the solid, also known as dry ice, does not melt into a liquid but sublimates directly into a gas. Liquid carbon dioxide only exists at pressures above five times normal atmospheric pressure. Converting between gas and liquid, therefore, depends entirely on pressure. For this calculation, convert between gas at one atmosphere of pressure around the freezing point of water, and liquid at room temperature and 56 atmospheres of pressure.