Carbon Dioxide

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A chemical compound that generally exists in its gaseous state, carbon dioxide is made up of one carbon and two oxygen atoms. The gas is uniformly distributed around the planet’s surface at a concentration close to 0.033 per cent or 330ppm. It is a vital gas as it is an important greenhouse gas due to its ability to absorb ultra violet rays emitted by the sun. Side-by-side, it plays a major role in the carbon cycle. The gas can also be found in its solid form and is called dry ice in this state. At normal atmospheric pressure, the gas cannot be found in a liquid state.

The gas in generally a colourless, odourless and neutral gas, and if inhaled in large concentration, it tends to produce a sour taste in the mouth and an irritable sensation in the nose and throat as the gas dissolving in the bodies mucous membrane brings about the formation of carbonic acid. Any concentration of the gas above 5000ppm is considered unhealthy in the long term and those above 50,000ppm pose a threat to animal and human life. Its density at standard temperature and pressure is around 1.98 kg/m³, about 1.53 times that of air. The gases neutral nature comes about due to the fact that it is a fully oxidized compound and thus it is not very reactive or flammable.

1 Industrial Modes of Production
2 Dry Ice
3 Role in Nature
4 Did You Know?
5 References
6 See Also

Industrial Modes of Production

The gas is commonly manufactured through six processes. The gas is a byproduct in ammonia and hydrogen plants. The gas can be derived from the combustion of fossil fuels as well as through fermentation. In some plants carbon dioxide is acquired through the thermal decomposition of CaCO₃. Carbon dioxide is also a byproduct in the production of sodium phosphate. Lastly the gas is acquired from the natural carbon dioxide gas wells.

Dry Ice

The gas has acquired the generic trademark of “dry ice” and is used as highly useful cooling agent. Unlike water which melts into liquid dry ice sublimes changing directly in to gas. Carbon dioxide’s sublimation/deposition point is -78.5°C (-109.3°F). Such low temperatures and direct sublimation make it a rather desired and versatile coolant. Dry ice is also very economical and costs as much as regular ice to manufacture. Dry ice production is usually carried out in two commercial sizes of solid blacks and cylindrical pellets. Most blocks weigh about 30 kilograms and are used by the shipping industry as the sublimation process is retarded by the blocks relatively small surface area. The pellets are usually a centimeter in diameter and come in very handy in grocery stores and labs.

Role in Nature

Carbon dioxide is the end product of a process known as cellular respiration, a process that helps in obtaining energy through the break down of sugars, fats and amino acids with oxygen. This process takes place in most living organisms ranging from all plants, animals and fungi. In higher animals the carbon dioxide travels through the blood stream to be deposited at the lungs where it is exhaled. In plants it is vital for the process of photosynthesis and the gas is absorbed from the atmosphere.

Did You Know?

Human activity is currently responsible for emitting 30 million tons of CO₂ each year, 12 million tons of which accumulate in the atmosphere.
Venus, our planetary neighbour, has an atmosphere that is 98% CO2. Due to the extreme greenhouse effect, temperatures reach 430°C. Similar conditions would exist on Earth if all the carbon stored in rock and vegetation were to be released as CO₂.
Motor vehicle exhaust is the source of nearly 30% of greenhouse gas emissions in the lower Fraser Valley.
A 50% to 60% reduction in present global emissions of carbon dioxide would be required to stabilize atmospheric CO₂ concentrations at current levels.
Under the Kyoto Protocol, participating countries set an average emission reduction target of 5.2% below 1990 levels by approximately 2010.
The average car produces its own weight in CO₂ emissions each year.
Canada has about 0.5% of the world's population but produces 2% of global CO₂ emissions.
Every litre of gas you use in your vehicle produces almost 2.5 kg of CO₂, as well as many other pollutants.
Burning garbage is a major source of greenhouse gas emissions.
About 1/3 of Canada's CO₂ and NO_x emissions come from transportation.

References

Environment Words — A Dictionary in Plain English, published By Images Asia
Change Impacts and Adaptation Program