ABOUT DRY ICE

Physical properties of dry ice

Dry ice is the popular name of carbon dioxide (CO2) in its solid state. Dry ice is non-flammable, non-conductive and contains no water.

History

In 1835, the French chemist Charles Thilorier published the first ever description of dry ice. Upon lifting the lid of a large cylinder full of liquid carbon dioxide, he noticed that the carbon dioxide was evaporating fast and leaving a thick layer of dry ice in the cylinder. Over the next 60 years, dry ice was observed and tested by a number of scientists for the purpose of exploring all of its useful properties and potential applications.

Dry ice applications

Dry ice has multiple practical applications:

• Dry ice directly converts to gas when melting and absorbs heat in the thawing process, thus reducing ambient temperature around it. This process means that dry ice can be used as a refrigerant. To induce artificial precipitation, water vapour in the air can be condensed by scattering dry ice into the upper layers of the atmosphere.
• Dry ice can be utilised in dry cleaning as it removes residues, colloids and stains, e.g. oil stains.
• Dry ice is also applied in medicine and cosmetics. Some dermatologists use dry ice to treat acne; this is known as cold therapy as it delicately freezes the skin. A mixture of ground dry ice and dimethyl ketone, at times blended with a little sulphur, is a frozen material used for treating acne. It is also used to remove unwanted skin formations. Liquid nitrogen and dry ice can also be used as materials for cold therapy, which can reduce inflammation.
• Dry ice also finds application in the food industry. It creates an impressive visual effect when added to wine, a cocktail or a beverage. Add dry ice to ice cream as an experiment and you will find it very difficult to melt the ice cream afterwards. It can also be used as a source of carbon dioxide and to produce carbonated water and other liquids such as beer.
• When dry ice is placed in water, sublimation is accelerated. This leads to the formation of thick low-lying smoke-like vapour. This is used in fog machines in theatres and nightclubs to create a mystical, dramatic effect.
• Dry ice is used in large quantities in the refrigerated transport of frozen fruit, vegetables, meat and seafood at low temperature. Dry ice is also used for transporting special medication, organs, blood plasma and vaccines.
• Dry ice is also an indispensable cleaning agent used for cleaning up contaminated surfaces without the use of any detergents, chemicals or organic solvents. When a contaminated surface is blasted with microscopic granules of dry ice and when they evaporate into the atmosphere, the sublimation effect is achieved, in which the contaminated layer vaporises simultaneously with the frozen granules of CO2 and ‘vanishes’ with no damage done to the surface.

 

Preparation and recommendations for handling dry ice

Step 1
Preliminary preparation for handling industrial quantities of dry ice

Plan ahead when you are going to need the dry ice as you will have to use it as quickly as possible. Dry ice changes from its solid to its gaseous state in the course of time. Ensure that the transportation vehicle or the room where you intend to work are well-ventilated.

When you work with large quantities of dry ice, as it converts back to its gaseous state it releases carbon dioxide into the atmosphere. This may present a hazard if work is carried out in a small and/or confined space. If you experience any sudden symptoms such as a headache, difficulty in breathing or blue lips or fingernails, you must immediately leave the room and/or let in some fresh air. In this case, getting fresh air is absolutely imperative as recirculated air will not be safe.

Ensure that you are wearing gloves while holding dry ice as it may cause frostbite. Keep an eye on any children nearby and never leave dry ice unattended.

Step 2
Choose a proper container

Store the dry ice in a thick isolated container, e.g. made of expanded polystyrene, but remember not to seal the container as carbon dioxide evaporation may cause the pressure to rise inside the vessel. Store the container in a well-ventilated space and do not place dry ice in a freezer or refrigerator. Its thermostat will shut down due to the extremely low temperature dry ice can create.

Step 3
Handle dry ice with caution

Put on your gloves and carefully open the dry ice container. Then, using your hands or a suitable instrument, take out the pellets or block of dry ice and place them/it on a soft surface, e.g. fabric, a plastic surface or a concrete floor (tiled flooring or other hard surfaces may be damaged by the cold temperature).

Step 4
Safe disposal

When you are ready to dispose of the dry ice, just take it out of the insulated container and leave it unpacked on a soft surface so that it can be aerated. It will then evaporate (sublimate). Ensure in advance that the room is well ventilated. Ventilate all storage spaces and rooms where you store dry ice, as carbon dioxide is heavier than air and sinks to low-lying parts of non-ventilated spaces.