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Three states of Carbon Dioxide

As we all know, our company is a industrial gases manufacturer. We are so familiar to CO2. I want to tell you three states of Carbon Dioxide.


Most of us in the industry associate CO2 with welding as a shielding gas and as a refrigerant in the food industry. Other characteristics make it unique.

The best example is when CO2 comes in contact with water and it forms carbonic acid. Although it is a weak acid, it is an acid nonetheless and can be used to adjust the pH in some processes where the pH is an important system parameter. This is evident in different industries such as paper production, textiles, and water treatment processes. An additional benefit is that carbonic acid is not stored as an acid (such as sulfuric or hydrochloric acids). As mentioned, the CO2 needs water to form the acid so it remains CO2 until needed and is not considered hazardous like other acids.


CO2 is stored as a liquid regardless of the container. The pressure in an uninsulated CO2 cylinder is somewhere around 800 psig depending on the ambient temperature. This means that any application using liquid CO2 has to be under pressure. Workers in the oil industry are aware of CO2 replacing water in enhanced oil recovery (EOR) where the liquid is mixed with sand or sand like substance (proppant) and pumped down an oil well to recover oil that is trapped inside the rock layers. EOR is a blanket term to describe different applications but the most common is fracking. Here the proppant is forced into the oil rich rock through man made fissures. This forces the rock to fracture and release trapped oil. When CO2 is used instead of water, its natural expansion of volume from liquid to gas helps enlarge the fissure and recover an additional amount of oil.

It’s not common knowledge that liquid CO2 is also used in the dry cleaning industry. In a special high pressure washer, liquid CO2 is introduced with a stain remover. The laundry is treated as in a regular washing machine using turbulence to clean the wash. When the cycle is done, the dirt, grime and stain remover are separated from the liquid CO2. The liquid CO2 is then removed for reuse and the laundry is removed clean and dry since no water was used.

Every chemical (element or compound) has a state in which the three phases (gas, liquid and solid) have the same properties and is attained adjusting the pressure and temperature; this is called the supercritical state. The supercritical state of CO2 can be produced in a specially designed processor. The fluid phase of supercritical CO2 is an exceptional solvent and is used to extract fragrances and color from flowers and plants. The process is, of course, performed under high pressure and requires highly specialized equipment.


Solid CO2 or dry ice is used as a coolant in several ways and forms. When liquid CO2 is transported through a high pressure line and discharged through special nozzles, it immediately turns to CO2 snow and is used in the refrigeration or freezing of food. Dry ice pellets replace regular ice in tubs that hold perishables for long over-the-road transport.

Dry ice in very small form (about the size of a grain of rice) is used as an abrasive to remove coatings from surfaces without harming the surface itself by shooting the rice size pellets through a blasting lance. This is popular in the aircraft industry where an airplane’s body has to maintain its integrity and cannot tolerate any damage that would occur with sand blasting. An additional benefit is that the removed coating does not have to be separated from the abrasive as the pellets sublimate to CO2 gas leaving the residue particles for easy cleanup.

Calling CO2 a super-gas may be overstepping the bounds of the definition, but it is definitely the most versatile product available in the industrial gas market. Learn more at :