Characteristics and Important Uses of Carbon Dioxide and Dry Ice

Carbon dioxide is an inorganic gaseous carbon compound. As early as the 1600s, people had started to think about this gas, although they didn't know what it really was and what to call it. Flemish chemist Jan Baptist van Helmont made observations which hinted about the existence of carbon dioxide, setting the stage for breakthrough work in the 18th century by Joseph Black, a Scottish chemist who identified carbon dioxide and explored many of its properties. By the 1800s, scientists had succeeded in creating and studying other forms of carbon dioxide, such as its solid form.

At room temperature, carbon dioxide takes the form of an odorless, colorless gas which is incombustible in normal conditions. Carbon dioxide can be forced into a solid form, in which case it is known as dry ice, and the gas is toxic to animals in high concentrations. People who happen to inhale too much carbon dioxide essentially suffocate, ultimately falling into unconsciousness as their oxygen saturation level drops.

The gas has a wide range of commercial uses, from the production of lasers to the carbonation of soft drinks. This compound exists naturally in the Earth's environment, and is produced in a variety of ways. Commercial carbon dioxide is usually derived from the byproducts of industrial processes. In addition to its production through respiration and combustion, the compound is produced through decomposition of organic materials as well. This gas is used for things like creating an inert environment for fire suppression, and the carbonation of beverages, among many other things.  

Amounts of carbon dioxide in the environment prior to the advent of the 20th century were kept stable by plants, which were capable of absorbing carbon dioxide. While this gas is entirely natural, some people realized about rising carbon dioxide levels towards the end of the 20th century and became concerned having found that humans were producing too much carbon dioxide for plants to process, a practice which could potentially lead to serious environmental problems. Now this humble gas has become a topic of interest for humans because it is classified among the offensive gases, gases which impact the Earth's environment when they reach high concentrations in the atmosphere.

Dry ice is very useful as a coolant because of its low temperature, -109.3°F (-78.5°C). It is also relatively easy to make.  Scientists sometimes need just a small quantity of dry ice which can be achieved easily. A mixture of gaseous carbon dioxide and dry ice is produced when part of the escaping gas condenses on the cloth. This approach is the most straightforward way to produce a small amount of dry ice for laboratory use.

To produce larger quantities of dry ice, evaporative cooling is necessary. First, liquefied carbon dioxide is produced by compressing carbon dioxide gas. Because the temperature of a substance increases as it is compressed, the gas must be cooled throughout the compression process to encourage the formation of a liquid. If the gas inside the vessel is roughly at room temperature, liquefaction starts when the pressure is about 870 pounds per square inch (ppsi), or about 6,000 kilopascals.

The next step is pretty simple. In any given chunk of matter, there will be certain molecules moving very fast, and some moving much more slowly. Their average velocity is what we call the temperature. After enough heat evaporates, the temperature of the liquid drops below freezing, a phase transition occurs, and we are left with solid carbon dioxide – dry ice. Dry ice is usually stored in insulated containers. When exposed to air, it starts to give off carbon dioxide gas immediately, because the temperature difference between the dry ice and the environment is sufficiently large that it mostly skips the liquid phase and just turns into gas. Some carbon dioxide is turned into vapor. Dry ice is used all the time to produce artificial fog for stage performances. It can also be used in combination with light shows, scattering the light so that it can be easily seen. It  has become increasingly popular in respect of its uses in the past few years.  The most common use of dry ice is in the food industry, where it's used to preserve perishable items and to carbonate liquids. Adding dry ice to any fruit juices or water will result in a sparkling drink. Dry ice also prevents the growth of bacteria, so it can be used to preserve dry seeds, grains.

A simple use of dry ice is to freeze fruits. Fruits frozen with dry ice will thaw firm, not soggy. Pop Rocks, a carbonated candy that "explodes" when put in the mouth, is made with pressurized dry ice. Campers have another use for dry ice: they can keep food fresh for a longer period of time without having to worry about sogginess.  Another use for dry ice has to do with medicine, where it's commonly used to preserve and ship biological samples. Cosmetic surgeons use dry ice to freeze warts for easy removal. The entertainment industry also has a popular use for dry ice. When dry ice comes in contact with water, it condenses and forms a thick white fog. Because dry ice can shrink metal, a common use of dry ice is to pop out small dents and to shrink machine parts before assembly.

A lesser known use for dry ice has to do with keeping mosquitoes and some other insects away. Mosquitoes are attracted to CO2 and naturally flow towards dry ice. We can place some pieces of dry ice around a mosquito trap to keep mosquitoes away. Wood beetles can be eliminated from furniture by placing the piece inside a sealed freezer with several pounds of dry ice. The insects and eggs will suffocate within 24 hours.  However, dry ice can be dangerous if not handled properly as with a temperature of -109.3°F (-78.5°C), it can severely burn the skin and cause suffocation if inhaled. The use of special gloves is highly recommended when handling dry ice. If working with dry ice indoors one must ensure that the space is well ventilated.