My Science School

               Dry ice is frozen carbon dioxide. When this gas is cooled to a temperature of -78.50C (-109.30 F) it becomes a solid without first becoming a liquid. This is why it is called dry ice. 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 -110o C (-166O F).