What Is Dry Ice?
Dry ice is a frozen form of a gas called carbon dioxide. You may be familiar with dry ice as the frosty pellets that ice-cream vendors use to keep their ice cream frozen for hours at a time.
Dry ice is called “dry” because it doesn’t’ melt into a liquid, like ice that is made from water.
Dry ice changes directly back to a gas as it thaws, and disappears into the air. Dry ice is a great deal colder than ordinary ice. This means you have to be careful with it.
Holding it in your bare hands for more than a few moments can cause frostbite, which is very dangerous.
When frozen carbon dioxide is exposed to the air, it evaporates slowly as a gas without going through the melting stage in the way that ice made from water does.
The fact that dry ice has a freezing point much lower than that of water makes it useful as a refrigerant, particularly for the storage of things that need to be kept very cold.
When powdered dry ice is added to such liquids as acetone (used in the manufacture of chloroform) or ether, it is possible to produce a mixture which has a constant temperature of as little as -110 degree C (-166 degree F).