dry ice

dry ice, carbon dioxide in its solid form, a dense, snowlike substance that sublimes (passes directly into the vapour without melting) at −78.5 °C (−109.3 °F), used as a refrigerant, especially during shipping of perishable products such as meats or ice cream. In the production of dry ice, advantage is taken of the spontaneous cooling that occurs when compressed, liquefied carbon dioxide at −57 °C (−71 °F) or lower is allowed suddenly to expand to atmospheric pressure: the liquid freezes to a finely divided solid that is compacted into cakes, weighing about 20 kg (45 pounds).