By the method of liquification CO is separated from the mixture of CO and CO2. The process of liquefication occur at Critical temperature and pressure. Critical temperature is the temperature above which the gas exist only as liquids. The pressure related to critical temperature is called critical pressure. As CO and CO2 possess different critical temperature, (Critical temperature of CO : -140.29 °C, Critical pressure of CO: 34.48 atm and ​Critical temperature of CO2 : 31 °C, Critical pressure of CO2: 72.94 atm) CO is separated from the mixture