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What is Dry Ice?

Batul Nafisa Baxamusa May 12, 2019
Have you ever wondered what dry ice is, the stuff that is used to transport frozen or extremely chilled products? Here is more on that...
More than a hundred years ago, dry ice was discovered accidentally. In 1834, Charles Thilorier opened a canister containing liquid carbon dioxide under pressure. This caused quick evaporation of the carbon dioxide due to the pressure.
This leads to a chilling effect that caused some amount of carbon dioxide to freeze in the container. The uses of this frozen carbon dioxide were not commercially tapped in America until the 1920s. The term was trademarked by the Dry Ice Corporation of America in 1925.

What is Dry Ice Made of?

It is made of frozen carbon dioxide (CO2). The gas is frozen at -109.3 °F, and forms a solid, white, opaque mass. It is interesting to note that it does not melt. Instead, dry ice tends to sublimate. Sublimation is a chemical phenomenon wherein a solid does not melt into liquid, but directly forms gas and evaporates.
This occurs when there is a rise in temperature causing dissipation of the solid. Therefore, you must have observed a thick fog or steam surrounding a block of dry ice. It sublimes at the rate of 5 to 10 pounds in 24 hours. It is manufactured in two forms―small pellets and huge blocks of dry ice that weigh over 50 pounds.

How is it Made?

Dry ice is made from raw carbon dioxide, that is compressed, purified, liquefied, and then made to undergo solidification. Gaseous carbon dioxide is obtained from other industries, where it is released as a by-product. This carbon dioxide is liquefied under 870 pounds per sq inch of pressure under room temperature.
After the gas is liquidized, the pressure is released. This causes some of the gas to solidify and some amount evaporates. The part that remains as solid is pressed to form blocks of dry ice or small pellets.

What is it Used for?

Dry ice does not melt like normal ice, therefore, does not create a mess in the area where it is stored. Thus, it has many applications in several industries where products are to be kept chilled.
The first use is in the food industry. It is used to store and transport food and other perishable items. It is also very useful in transportation and storage of biological samples, like tissues, organs, etc.
When using it to store food, you need to bring Food Grade dry ice. This is used for transportation and making food, as well as in soda fountains. It is also used to keep crushed ground beef cold when it is being processed.
The fog and smoke created in a spooky scene are made from dry ice. It is added to water. This causes water vapor condensation, leading to formation of fog. It is also used to freeze mixtures of chemicals in laboratories. This helps in carrying out cold chemical reactions and condensation of solvents.
It also has a very important application in cloud seeding. It helps in carrying out altering cloud precipitation. This helps in altering the amount of precipitation that falls from the clouds.

Is it Toxic?

Dry ice is not toxic, however, it should not be stored in a closed area without ventilation. This is because, it tends to sublimate into carbon dioxide. Carbon dioxide is not toxic when in lesser concentrations. However, in a closed room, when the carbon dioxide concentration level exceed 5%, it has a poisonous effect.
One should never ever eat, swallow, or taste it. It can lead to severe internal injuries. Never try to touch it with your bare hands. When handling, make sure you wear gloves. This is because, the temperature is very low, and it can cause severe skin tissue damage. When carrying out experiments, make sure children are under adult supervision at all times.
Dry ice had many industrial and commercial uses. Do not attempt to make it at home unless you are sure about what you are doing. If you have brought over some dry ice for some use, and need to discard the leftover ice, do not worry. Just place it in an open area. It will sublimate into carbon dioxide, discarding itself.