[tranquility]

Hi I would like to find out whether it is possible to mix two or more gases together to give similar properties to CO2 in the 15 to 40 degree range ?  This new gas mix would ideally have a similar temperature vs. vapour pressure relationship to CO2 (850 PSI @ 20 degrees) with a critical temperature above 30 degrees. Would this be possible and if so could this new gas mixture be made insoluble in water?

Thanks ...