A nonflammable,
colorless, odorless gas. Found in air at concentrations of about
0.03%, carbon dioxide may exist simultaneously as a solid,
liquid and gas at a temperature of –69.9°F (-56.6°C) and a
pressure of 60.4 psig (416 kPa). At a temperature of –110°F
(-79°C) and atmospheric pressure, carbon dioxide solidifies
forming “dry ice” at a density of 97.4 pounds per cubic foot.
Because of its low concentration in the atmosphere, air is not a
suitable feedstock for carbon dioxide production. Instead, CO2
is obtained from by-product streams from various manufacturing
processes. Bulk quantities of carbon dioxide are usually stored
and shipped as liquid under pressure and refrigeration.
Although not an inert, carbon dioxide is non-reactive with many
materials and is often used for inerting purposes, such as
blanketing and purging of tanks and reactors. It’s also used as
a shielding gas in the arc welding process. Carbon dioxide is
the source of the bubbles in soft drinks and other carbonated
beverages. It’s used to fill certain types of fire extinguishers
that rely on its inert properties, density, and low temperature
when released from high-pressure storage. In addition to its
“inert” properties, carbon dioxide, as dry ice, is used to
freeze a variety of foods.
