Liquid carbon dioxide is the liquid state of

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

(), which cannot occur under atmospheric pressure. It can only exist at a pressure above , under (temperature of critical point) and above (temperature of

triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at which the sub ...

). Low-temperature carbon dioxide is commercially used in its solid form, commonly known as "

dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...

". Solid sublimes at at Earth

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

— that is, it transitions directly from solid to gas without an intermediate liquid stage. The uses and applications of liquid carbon dioxide include decaffeinating coffee, extracting virgin olive oil from olive paste, in fire extinguishers, and as a coolant.

Properties

Liquid carbon dioxide is a type of liquid which is formed from highly compressed and cooled gaseous carbon dioxide. It does not form under atmospheric conditions. It only exists when the pressure is above 5.1 atm and the temperature is under (temperature of critical point) and above (temperature of

). The chemical symbol remains the same as gaseous carbon dioxide (). It is transparent and odorless and the density of it is 1101 kg/m³ when the liquid is at full saturation at . The

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solub ...

of water in liquid carbon dioxide is measured in a range of temperatures, ranging from to . At this temperature, the pressure is measured in a range from 15 to 60 atmospheres.

Uses

Uses of liquid carbon dioxide include the preservation of food, in fire extinguishers, and in commercial food processes. For food preservation, liquid carbon dioxide is used to refrigerate, preserve, store and soften. In a fire extinguisher, the is stored under pressure as a liquid to act as an anti-flammable. The liquid carbon dioxide not only reduces combustion by displacing

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

, but also cools the burning surface to avoid further damage.

Solvent extraction A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

using compressed liquid can be used in industrial processes such as removing

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is mainly used recreationally as a cognitive enhancer, increasing alertness and attentional performance. Caffeine acts by blocking binding of adenosine to ...

from

coffee Coffee is a drink prepared from roasted coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content. It is the most popular hot drink in the world. Seeds of ...

or improving the yield of olive oil production. Liquid carbon dioxide is being considered as a means of CO₂ transportation for underground or subsea storage purposes. Due to its high density as a liquid, it is much more feasible to ship than as a gas.

References

{{Oxides Carbon dioxide

Properties

Uses

See also

References