Dry Ice is a unique substance which has many uses. Essentially, dry ice is frozen carbon dioxide (CO2). The first report of what we now call dry ice came from the French chemist Charles Thilorier, in 1834. In 1924, the DryIce Corporation of America trademarked the solid form of CO2 as “Dry Ice”, which is what it is popularly called today.
The reason that it is called “dry ice” is that is literally is dry – it doesn’t get wet. At normal atmospheric pressures, CO2 changes directly from a solid to a gas. It skips the liquid phase which makes regular ice seem wet.
Frozen CO2 is also much colder than regular ice. Whereas regular ice freezes at 32 degrees Fahrenheit, carbon dioxide changes from a gas to a solid at -109.3 degrees Fahrenheit. This extremely cold temperature makes it very dangerous to handle with bare hands. It can cause frostbite in a very short period of time.
Dry ice has been used for a wide variety of purposes throughout the past century. The primary use is to refrigerate food when electrical refrigeration isn’t available. Through the process of sublimation (when the CO2 changes from a solid to a gas form), it can maintain cold food for a long period of time.
It is also often used in scientific laboratories for a similar purpose. Frozen CO2 can be used to keep cell tissues and other important materials which are sensitive to heat at a cool temperature.
If you’ve ever been to a haunted house or a play and seen heavy fog on the ground, it is likely that you have seen dry ice in action. This effect can be achieved because carbon dioxide is heavier than air, so evaporated CO2 will sink and accumulate on the ground. This is far superior to most artificial fog machines which use other methods, because the artificial fog will often rise like smoke.
It is also often used by doctors and brave individuals to remove warts and other unsightly blemishes on their skin. By applying a small piece of frozen CO2 and some pressure to a wart, it will effectively freeze and kill the tissue, which allows for easy removal.
Another interesting use for this substance is to bait insects like mosquitoes. These insects have sensors which attract them to carbon dioxide. They find the high concentration of CO2 found in dry ice irresistible.
In the 1960’s scientists guessed that the polar ice caps of Mars are made of frozen carbon dioxide. More recent observations have shown that while the topmost layer consists of frozen CO2, the bulk is probably regular frozen water.