CO2 or Carbon Dioxide is a colorless, odorless, and slightly
acid-tasting gas, sometimes called carbonic acid gas, the molecule of which
consists of one atom of carbon joined with two atoms of oxygen (CO2). Carbon
dioxide is produced in a variety of ways; by combustion, or oxidation of
materials containing carbon, such as coal, wood, oil, or foods; by
fermentation of sugars; and by decomposition of carbonates under the
influence of heat or acids. Commercially, carbon dioxide is recovered from
furnace or kiln gases; The carbon dioxide is purified by dissolving it in a
concentrated solution of alkali carbonate or ethanolamine and then heating
the solution with steam. Then evolved and is compressed into steel
cylinders. The atmosphere contains carbon dioxide in variable amounts,
usually 3 to 4 parts per 10,000. and has been increasing by 0.4 percent a
year. It is used by green plants in the process known as photosynthesis, by
which carbohydrates are manufactured.