Carbon dioxide is an, odourless, colourless and slightly toxic gas with a slightly pungent, acidic taste. It will not burn or support combustion.Carbon dioxide has many applications based on its varied properties. It is widely used in food processing for cooling, preservation and pH control. It is also used to blanket chemicals, control of pH in water treatment, as a shield gas in metal welding, to stimulate biological growth and as a fire-extinguishing agent.
Carbon dioxide is used as gas, in liquid and solid form. Its sublimation temperature is -79 oC and so dry ice, solid carbon dioxide, will have that temperature before sublimating into gas without passing liquid phase. Carbon dioxide based freezing systems can be designed for a convenient range of temperatures down to -54 oC, making it a useful refrigerant for applications such as storage, chilling and freezing of food products.
Carbon dioxide is highly soluble in water at moderate pressure, and in oils and plastics at elevated pressures. This leads to its use in e.g. beverage packaging before closing the containers and to carbonated soft drinks and mineral water.
In its liquid form, carbon dioxide is a selective solvent for a number of substances, and at supercritical pressure it is an even stronger solvent. Its dryness prevents damage to sensitive materials.
Liquid carbon dioxide forms solid dry ice when expanded to atmosphere pressure, which is used at cryocleaning. Small dry ice pellets are blasted with pressurized air at surfaces to be cleaned from oil dust and dirt. The method is also used with ultra high purity carbon dioxide (UHP) to clean optical systems, semiconductor devices and LCD screens.