Dry ice: buy dry ice, dry ice experiment, dry ice blasting

Dry ice is solid carbon dioxide.^[1] It is commonly used as a versatile cooling agent.

Dry ice sublimates, changing directly to a gas at atmospheric pressure. Its sublimation and deposition point is -78.5 °C (-109.3 °F). Its enthalpy of sublimation (ΔH_sub) at -78.5 °C (-109.3 °F) is 571 kJ/kg (245.5 BTU/lb). Dry ice density is usually between 1.2 and 1.6 kg/dm³. The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water or ice and leaves no moisture as it changes state.^[2] Dry ice can carbonate food that is nearby.

History

In 1835 the French chemist Charles Thilorier published the first account of dry ice.^[3]^[4] Upon opening the lid of a large cylinder containing liquid carbon dioxide, he noted much of the carbon dioxide rapidly evaporated leaving solid dry ice in the container. Throughout the next 60 years, dry ice was observed and tested by scientists.

Manufacture

Dry ice is typically produced in two standard forms: blocks and cylindrical pellets. A standard block weighing approximately 30 kg is most common. These are commonly used in shipping, because they sublimate slowly due to a relatively small surface area. Pellets are around 1 cm in diameter and can be bagged easily. This form is suited to small scale use, for example at grocery stores and laboratories. Dry ice is also inexpensive; it costs less than US$2 per kilogram.^[7]

Applications

Dry ice is commonly used to package items that need to remain cold or frozen, such as ice cream, without the use of mechanical cooling. In medicine it is used to freeze warts to make removal easier.^[8] In the construction industry it is used to loosen floor tiles by shrinking and cracking them, as well as to freeze water in valveless pipes to allow repair. In laboratories, a slurry of dry ice in an organic solvent is a useful freezing mixture for cold chemical reactions.

Dry ice can be used in theatre productions in order to create the effect of dense fog. Unlike most artificial fog machines, which makes the fog rise up much like smoke, fog from dry ice crawls on the ground.

Dry ice can be used to carbonate water and other liquids such as soft drink and beer.^{[citation needed]} It can be used as bait to trap mosquitoes and other insects^[10]

When dry ice is placed in water sublimation is accelerated, and low-sinking dense clouds of fog (smoke like) are created. This is used in fog machines, at theaters, discoteques, Haunted Houses, and nightclubs for dramatic effects. When used in theatre productions it creates the effect of dense fog. Dry Ice is also used in cloud seeding: the process of altering cloud precipitation.

dry ice blasting

One of the largest alternative uses of dry ice is blast cleaning. Dry ice pellets are shot out of a nozzle with compressed air. This can remove residues from industrial equipment. Examples of materials being removed include ink, glue, oil, paint, mold and rubber. dry ice blasting can replace sandblasting, steam blasting, water blasting or solvent blasting. The primary environmental residue of dry ice blasting is the sublimed CO₂, thus making it a useful technique where residues from other blasting techniques are undesirable.^[11]

Safety

Although useful in a number of contexts, dry ice can cause severe skin damage through cold burns. It is especially dangerous because dry ice produces a lot of fog, which can make it hard to see exactly where the dry ice is. Generally, airline passengers are not permitted to bring packages containing dry ice into an airplane cabin.

Dry ice also evaporates in large quantities of carbon dioxide gas, which could displace oxygen containing air and pose a danger of asphyxiation.

Dry ice

Contents

History

Manufacture

Applications

dry ice blasting

Safety

See also

References

External links