What is Dry Ice
Dry Ice is the frozen form of the naturally occurring Carbon Dioxide. It is also known as ‘cardice’ in some parts of the world. The main use of dry ice over the normal ice is due to its lower temperature that makes it an important component when it comes to cold storage and deep freezing of perishable food items. The temperature of dry ice is -78.5 degree Celsius, thereby, making it ideal for deep freezing. The property of sublimation of dry ice, wherein it directly changes into gaseous state at temperatures below -56.4 degree Celsius and 5.13 atm pressure, ensures that there is no liquid left behind in the cold storage.
However, one has to ensure that he does not touch the dry ice with bare hands as it can lead to injuries termed as ‘frostbite’. Good quality gloves are hence a must while handling dry ice. It is important that the dry ice is kept in a room that is well ventilated to avoid situations of displacement of oxygen from the room and problems of any kind to the people in the room due to the process of asphyxiation. It is to be noted that the thermal and electrical conductivity of dry ice is very low, thereby, making it safe to use.
Though Thomas B Slate is said to be the first person to have manufactured dry ice in 1924, it is worth noting here that observations regarding the occurrence of dry ice were made as early as 1834 by French scientist, Charles Thilorier. The process of manufacture of dry ice is also relatively easy. The simple steps involved in the manufacture of dry ice are as follows. In the first step, mixtures that have high concentration of carbon dioxide are produced and subjected to high pressure at very low temperatures until the liquid form of CO2 is achieved. In the next step, the pressure applied is reduced, leading to the vaporizing of some part of the liquid and rapid fall in the temperature of the remaining liquid carbon dioxide, thereby, leading to the formation of dry ice in the container.
The obtained snow like dry ice is then compressed into desired forms. While the industries make use of dry ice in large scale prefer large blocks of dry ice; the small scale industries make use of the pellets of dry ice. Dry ice is used for a variety of purposes in addition to deep freezing. It is used for blast cleaning in industries and as an organic solvent for reactions that operate at very low temperature. However, prime importance needs to be given to safety while using dry ice to avoid the undesirable phenomenon of asphyxiation.