Carbon dioxide is a colorless, odorless, non-flammable, slightly acidic-tasting gas. It is approximately 1.5 times as dense as air and is soluble in water. One gram of liquid carbon dioxide yields 30.5 in3 of gas at standard temperature and pressure (STP).
The specific volume is 8.74 ft3/lb at STP.
The specific gravity is 1.522 at STP. The molecular weight is 44.0.
Gas density (15° C and 100kPa) equals 1.85 kg/m3 (g/l).
Commercial operations collect carbon dioxide from furnace or kiln gases, fermentation processes (Beer!), reaction of carbonates with acids and reaction with steam and natural gas.
The carbon dioxide obtained is purified through dissolution in a concentration of alkali carbonate. Heating is required with steam to evolve and then compressed to a liquid at 900 PSI in the highest quality steel cylinders.
As the liquid CO2 is ejected from the cartridge, it 'boils' and changes phase into its gaseous state.
As more and more liquid boils down, the vapor pressure remains constant until the liquid is boiled off. After this time, the vapor pressure drops precipitously until all the gas is discharged from the cylinder.
Generally, during actuation of CO2 gas delivery systems, if the gas is discharged with the cylinder in the 'up' position, only gas is dispelled from the cartridge.
However, if the gas is discharged with the cylinder in the 'down' position, and with gravity affecting the liquid CO2, along with the gas being dispelled, some liquid CO2 is also ejected.
This liquid CO2 instantly turns to dry ice, sublimating quickly into a gaseous state.
This property of actuation is useful in some applications where increased gas pressure is desired.