Dry Ice Facts

Learn about solid carbon dioxide

Pellets of dry ice sublimating
Jasmin Awad / EyeEm / Getty Images

Dry ice is the solid form of solid carbon dioxide, CO2. Here are some facts about dry ice that can help keep you safe when working with it—and are just fun to know.

Dry Ice Facts

  • Dry ice is solid carbon dioxide. It is sometimes called "cardice".
  • Dry ice is extremely cold (-109.3°F or -78.5°C). At this temperature, it sublimates from the solid state into the gaseous state or undergoes deposition from gas to solid. In order for dry ice to form liquid carbon dioxide, it needs to be placed in a high-pressure environment.
  • The first published observation of dry ice was in 1835 by French chemist Charles Thilorier. He noted the formation of dry ice when a container of liquid carbon dioxide was opened.
  • Dry ice resembles snow or water ice. It's usually sold as chunks or pellets, which appear white because water vapor from the air readily freezes onto the surface. While it looks somewhat like ordinary water ice, it's called "dry" because there's no intermediate liquid phase.
  • Dry ice density usually ranges between 1.2 and 1.6 kg/dm3.
  • The molecular weight of dry ice is 44.01 g/mole.
  • Dry ice is nonpolar, with a dipole moment of zero. It has low thermal and electrical conductivity.
  • The specific gravity of dry ice is 1.56 (water = 1). Dry ice sinks in water and to the bottom of drinks.
  • The white vapor released when dry ice sublimates does contain carbon dioxide, but it's mostly water fog produced when the cool gas condenses water from the air.
  • When dry ice is added to food, as when making ice cream or freezing fruit, the carbon dioxide carbonates the liquid and can react with water to form dilute carbonic acid. This adds an acidic or sour flavor.
  • When dry ice sublimates, some of the carbon dioxide gas immediately mixes with air, but some of the cold dense gas sinks. Carbon dioxide concentrations increase near the floor of a room where a lot of dry ice is being used.

Dry Ice Safety

  • Contact with dry ice can result in frostbite and cold burns. Avoid allowing contact between dry ice and the skin, eyes, or mouth.
  • Use insulated gloves when handling dry ice.
  • Although dry ice and carbon dioxide are not toxic, the use of dry ice may present a respiratory hazard because it can sink and displace air near the ground. Also, when it mixes with the air, there is more carbon dioxide (less oxygen) in each breath. Use dry ice in a well-ventilated area.
  • Do not eat or swallow dry ice.
  • Do not seal dry ice in glass or other closed containers, since the pressure buildup may result in breakage or bursting.