What is Dry Ice?
Dry ice is frozen carbon dioxide, which is the gas that we breathe out and the gas that plants take in for photosynthesis. It is also added to water to produce carbonation in soda water and other fizzy drinks. Dry ice is very cold, measuring -109.3 degrees Fahrenheit or -78.5 degrees Celsius. Because of the extreme temperatures, it must be handled with gloves or tongs. It can cause immediate frostbite if you touch it with your skin.
Uses for Dry Ice
Dry ice is used commercially for cooling food and other products. It gives off two times the cooling energy of water ice by weight and three times by volume, making it highly efficient. It requires no electricity or other power sources to keep cargo cold, and its only byproduct is carbon dioxide gas. Dry ice is also used to create fog at parties and haunted houses. By dropping it in warm water, you can speed the dry ice's natural sublimation process.
Sublimation
Like any cold material, dry ice cannot last forever. It does not melt like normal ice, however. Dry ice sublimates, which means that it transforms from a solid directly into a gas. The benefit of this is that no puddles are left behind as the dry ice slowly disappears. This is how dry ice acquired its name. It typically sublimates at a rate of 5 to 10 lbs. in a 24-hour period when stored in an ice chest.
Dry Ice vs Fridge
Your refrigerator's cool temperature will slow the sublimation process, but only temperatures below -109.3 degrees Fahrenheit can halt it. Neither your fridge nor freezer can reach these temperatures, so dry ice stored in a fridge will eventually disappear. To make your dry ice last as long as possible, delay purchasing it until just before you need it.