dry ice
"Dry ice," or solid carbon dioxide, is a substance that sublimes at atmospheric pressures. Dry ice is very cold 78C and so is used as a coolant for goods such as ice cream that must remain frozen during shipment. Because the dry ice sublimes rather than melting, there is no liquid mess associated with its change of state as the dry ice warms. As you may have seen in demonstrations, dry ice merely transforms from a solid to a cold, steamy looking gas. Ferrocene an iron-containing compound is usually purified by sublimation by gentle warming at atmospheric pressure. In the Figure below , you can see the reddish ferrocene crystals deposited on the outside of that tube. Deposition is the change of state from a gas to a solid.