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Dry
ice is frozen carbon dioxide (CO2) which is a natural
part of the earth's atmosphere. We exhale CO2 during
breating, and it is used by plants for their photosynthesis process.
Dry ice is solidified
carbon dioxide (CO2). Dry ice is extremely cold, -109°F (-79°C) and does not melt.
Instead, it sublimates (changes directly from solid to gas), releasing CO2.
Also, dry ice is pure CO2 making it colorless, tasteless,
odorless and bacteriostatic. Because of these qualities, dry ice
creates an inert atmosphere that is neither flammable nor poisonous.
Because of its organic makeup, dry ice is effective in a number
of different applications including being used with water to make
soda water or for freezing foods.
How
Dry Ice Is Made
The first step in making dry ice is to convert
CO2 into a liquid by compressing the CO2 and removing any excess heat. The CO2 liquifies at approximately 870 PSI
at room temperature. The gas is cooled until it is condensed into a liquid. The pressure is then reduced over the liquid CO2 by processing
it through an expansion valve.
As
the temperature drops to -109°F, a portion of the liquid sublimates
resulting in the remainder to cool into snowflakes. The dry ice
snow is then compacted under a large press to form blocks. From
the blocks, various sized pellets can also be extruded.
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