The Process of Dry Ice Explained

Dry ice is carbon dioxide, but frozen. The surface temperature of a block of dry ice is -109.3 degrees Fahrenheit and -78.5 degrees Celsius. It also possesses a very amazing feature of sublimation. It turns directly into carbon dioxide gas rather than transforming itself into liquid as the solid form breaks down. The uber-cold temperature and the feature of sublimation deem dry ice great for refrigeration purposes. For instance, if you are considering sending a frozen object to a foreign country, it is advisable to pack it in dry ice. It will still be frozen when it will reach its destination and no messy liquid is left as a residue unlike the normal ice.

Many of us are acquainted with liquid nitrogen which is subjected to boiling at -320 degrees F or -196 degrees C. It is fairly messy and difficult to handle when it comes to liquid nitrogen. You might be curious about the reason why liquid nitrogen is liquid while carbon dioxide is solid. The distinction is because of the solid-liquid-gas characteristics of nitrogen and carbon dioxide.

We are all aware of the solid-liquid-gas behaviour of water. At sea level, the freezing point of water is 32 degrees F or 0 degrees C and the boiling point being 212 degrees F or 100 degrees C. The behavior of water differs when the pressure is changed. When the pressure is low, the boiling point falls with it. If the pressure is lowered enough, water will boil at room temperature. If you detect the solid-liquid-gas behavior of water on a graph which shows both pressure and temperature, you will create a phase diagram of water. It showcases pressures and temperatures at which the water is subjected to change between solid, liquid, and gas.

In order to make dry ice, begin with a high pressure container fully filled with liquid carbon dioxide. When you let the liquid carbon dioxide release from the tank, the liquid expands and the carbon dioxide evaporates at high speed which cools the remainder of the liquid as below as the freezing point where it is subjected to transform into a solid. If you have ever noticed a carbon dioxide fire extinguisher at work, you will notice the carbon dioxide snow formed in the nozzle. You have to compress the carbon dioxide snow in order to create a block of dry ice.

Safety tips

When it comes to handling dry ice, ensure to wear heavy gloves. The uber-cold surface temperature of dry ice and damaged your skin easily when touched directly. For the very same cause, you should never even think of tasting or swallowing the dry ice either.

Another factor your dry ice supplier will advise you about is the ventilation. Ensure that the area you are in is well-ventilated. Carbon dioxide weighs more than the air and it can cause its concentration effects in low areas or enclosed spaces such as a car or a room where the sublimation of dry ice is taking place.

February 2019
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