Carbon Dioxide

Synonyms: Carbonei dioxidum; carbonic acid gas; carbonic anhydride; E290.

Description: Carbon dioxide occurs naturally as approximately 0.03% v/v of the atmosphere. It is a colorless, odorless, noncombustible gas with a faint acid taste. Solid carbon dioxide, also known as dry ice, is usually encountered as white-colored pellets or blocks.

Chemical Name: Carbon dioxide

Aerosol propellant; air displacement.

• Carbon dioxide and other compressed gases such as nitrogen and nitrous oxide are used as propellants for topical pharmaceutical aerosols.

• They are also used in other aerosol products that work satisfactorily with the coarse aerosol spray that is produced with compressed gases, e.g. cosmetics, furniture polish, and window cleaners.

• The advantages of compressed gases as aerosol propellants are that they are less expensive; are of low toxicity; and are practically odorless and tasteless.

• Also, in comparison to liquefied gases, their pressures change relatively little with temperature.

• However, the disadvantages of compressed gases are that there is no reservoir of propellant in the aerosol and pressure consequently decreases as the product is used.

• This results in a change in spray characteristics. Additionally, if a product that contains a compressed gas as a propellant is actuated in an inverted position, the vapor phase, rather than the liquid phase, is discharged.

• Most of the propellant is contained in the vapor phase and therefore some of the propellant will be lost and the spray characteristics will be altered.

• Also, sprays produced using compressed gases are very wet. Valves, such as the vapor tap or double dip tube, are currently available and will overcome these problems.

• Carbon dioxide is also used to displace air from pharmaceutical products by sparging and hence to inhibit oxidation.

• As a food additive it is used to carbonate beverages and to preserve foods such as bread from spoilage by mold formation, the gas being injected into the space between the product and its packaging.

Carbon dioxide is generally compatible with most materials although it may react violently with various metal oxides or reducing metals such as aluminum, magnesium, titanium, and zirconium. Mixtures with sodium and potassium will explode if shocked.

In formulations, carbon dioxide is generally regarded as an essentially nontoxic material.

Handle in accordance with standard procedures for handling metal cylinders containing liquefied or compressed gases. Carbon dioxide is an asphyxiant, and inhalation in large quantities is hazardous. It should therefore be handled in a well-ventilated environment equipped with suitable safety devices for monitoring vapor concentration. It should be noted that carbon dioxide is classified as a greenhouse gas responsible for global warming. At the present time there are no restrictions on its use for aerosols and other pharmaceutical applications.

Nitrogen; nitrous oxide.