Facts about Frozen Carbon Dioxide

The French chemist Charles Thilorier first recorded frozen carbon dioxide, also known as dry ice or card ice, in 1834. Thilorier observed the formation of frozen carbon dioxide when he opened a container of liquid carbon dioxide, which boiled away to leave a residue of solid carbon dioxide.

Frozen carbon dioxide sublimes at normal atmospheric conditions. Sublimation involves a substance going from a solid to a gaseous state without forming a fluid in between. This property gives the substance its name of dry ice. Normally frozen carbon dioxide will sublimate at a rate of five to ten pounds every 24 hours when contained in a typical ice chest. Dry Ice is much heavier than water ice, and weighs about double traditional ice. When handling this substance the use of insulated gloves and eye protection is recommended.

With a temperature of minus 109.3°F (minus 78.5°C), frozen carbon dioxide is commonly used in refrigeration. When compared to water ice, frozen carbon dioxide gives more than twice the cooling energy per pound by weight and three times the cooling energy per volume. The use of dry ice refrigeration allows the transport of many biological samples for medical and research purposes. It is also of use in sending special deliveries of ice cream.

While useful for maintaining the cold temperature of frozen food in the event of a breakdown of a freezer, dry ice should not be stored in a standard domestic fridge or freezer. The extreme cold of frozen carbon dioxide may cause the thermostats of such devices to cut out.

Perhaps the most common use of frozen carbon dioxide is the production of fog and smoke effects in theatrical and film productions. Dry ice added to warm water causes the sublimation of the frozen carbon dioxide along with bubbling and copious amount of artificial fog. Many an actress has sat around a cauldron of warm water with added dry ice intoning, “Hubble-bubble toil and trouble, fire burn and cauldron bubble”. Calculations for this fog production depend on the temperature of the water and the quantity of dry ice added. According to DryIceinfo.com, “5 pounds of Dry Ice in 4 to 5 gallons of hot water, the greatest amount of fog will be produced the first 5 to 10 minutes. There will be far less fog for the next 5 to 10 minutes as the water cools down and the volume of Dry Ice diminishes. As the water cools, the fog becomes wispier. Dry Ice makes fog because of its cold temperature, minus 109.3°F (minus 78.5°C), immersed in hot water, creates a cloud of true water vapor fog. When the water gets colder than 50°F, the Dry Ice stops making fog, but continues to sublimate and bubble. The fog will last longer on a damp day than on a dry day.”

Persons requiring frozen carbon dioxide may buy it in the form of blocks or pellets or make their own. Production of dry ice from a carbon dioxide cylinder requires a siphon tube within the cylinder, which allows access to the liquid carbon dioxide at the bottom of the cylinder. Normally such a system provides the production of frozen dioxide snow. However, the addition of attachments to the cylinder allows the production of frozen carbon dioxide discs. DryIceinfo.Com gives a detailed methodology for the industrial production of frozen dioxide compressing carbon dioxide removes heat and liquefies the gas. The gas liquefies at approximately 870 pounds per square inch at room temperature. the pressure is reduced over the liquid carbon dioxide by sending it through an expansion valve into an empty chamber. The liquid will flash, with some turning into gas causing the remainder to cool. As the temperature drops to minus 109.3°F (minus 78.5°C), the temperature of frozen carbon dioxide, some will freeze to form snow. The dry ice snow is compressed under a large press to form blocks or extruded into pellets. A commercial system may produce a 55 pound block of frozen carbon dioxide in under 60 seconds.