Solidified carbon dioxide (CO2) is commonly called Dry ice. It looks similar to generic ice, but is much colder and has other properties. It is widespread in space and is a raw material for meteorites and planetary icing areas. Dry ice is artificially created on Earth because it does not occur naturally here. But how is dry ice made? Let’s find out.
How is Dry Ice Made?
Dry ice is produced by first liquefying gaseous carbon dioxide under pressure. The liquid carbon dioxide is released very quickly. A part of the carbon dioxide evaporates and cools the rest of the CO2 by evaporative cooling to such an extent that it freezes and the carbon dioxide snow is formed. Depending on the application, this is then pressed into the desired shape.
Dry ice pellets consist of liquid CO2 (Carbon Dioxide), which is stored in a pressure vessel. When the liquid CO2 expands, it forms snow. This snow is pressed into pellets with the appropriate diameter. The plant that produces the pellets is called a pelletizer. The dry ice pellets are stored and transported in well-insulated containers. High-quality containers limit the evaporation of the pellets to a few percent per day.
Under the normal air pressure of 1 atmosphere, dry ice does not melt but instead changes directly into gaseous carbon dioxide. Dry ice does not get warmer than -78.4 degrees Celsius on earth. Dry ice is white and odorless. If you breathe in the resulting vapors, it tingles because carbonic acid is formed in contact with the water of the mucous membranes.
The use of Dry ice
1. Dry ice is used in the food industry for cooling, often in the form of large blocks
2. Dry ice can be used for cleaning as fine granules. The granules are blown onto the surface to be cleaned at high speed. Contaminants become hard and brittle due to the cold and flake off.
3. Dry ice underwater creates the impression of boiling water that is why it is occasionally used in films. The process differs from real boiling water because it contains CO2 filled water bubbles.
4. In motorsport, dry ice is used to cool the engines. Fans with dry ice are installed before the race. If the frozen carbon dioxide gets into the engine compartment, it is harmless to the machine because of dry ice sublimes.
5. In cooling mixtures for cooling down to -90 ° C
6. In restaurants and hotels to slow down the melting of ice sculptures
7. In medicine for freezing warts
8. In mechanical engineering, when joining hard metal sleeves on steel shafts, because the steel shrinks more at low temperatures than hard metal.
Hazards of Dry Ice
1. Dry ice is relatively safe to handle compared to other low-temperature substances since it is solid and cannot flow anywhere uncontrollably. It also sublimates and forms a thin protective gas layer on its surface, which prevents direct contact with the skin. However, improper handling can cause accidents.
2. When handling dry ice, gloves, and especially goggles are strongly recommended. If dry ice nevertheless comes into firm contact with the skin for several seconds, sublimation stops and the ice sticks to it. It causes cold burns, in which the tissue dies within seconds. This process is used medically in the treatment of warts, but the amounts applied are so small that only the top layers of skin die.
3. When stored in closed rooms, the resulting carbon dioxide gas displaces the air on the floor due to its higher density. In high concentrations it can be suffocating, symptoms are loss of mobility and awareness, the person does not even notice the suffocation.
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4. Dry ice must not be used for cooling drinks that emit fog and vapor. Ingestion of dry ice is life-threatening.
Now you know how dry ice is made. Next time you are watching a movie and see someone jump into boiling water, don’t be surprised.