January 5, 2004
A: FROM MENTOR MAYLING WONG IN IL
Dry ice is the unscientific name for frozen carbon dioxide. Carbon
dioxide is in gas form when at room temperature (70 deg F). It is in ice
form at the low temperature of -109.3 deg F at atmospheric pressure (1
atm). From the webpage www.howstuffworks.com:

To make dry ice, you start with a high-pressure (on the order of a few
atm) container full of liquid carbon dioxide. When you release the liquid
carbon dioxide from the tank, the expansion of the liquid and the
high-speed evaporation of carbon dioxide gas cools the remainder of the
liquid down to the freezing point, where it turns directly into a solid.
If you have ever seen a carbon dioxide fire extinguisher in action you
have seen this carbon dioxide snow form in the nozzle. You compress the
carbon dioxide snow to create a block of dry ice.

Why is it dangerous? Dry ice is COLD! When working with dry ice, never
touch it directly. If skin is in direct contact with dry ice, skin will
freeze to the same temperature as dry ice: -109.3 deg F. It is important
to have proper protection (gloves) when working with dry ice. (Have you
seen the movie _Christmas Story_ when the kid in the playground touches
the frozen metal pole with his tongue and gets his tongue stuck to the
pole? It is the same idea, only much colder!) Also, as dry ice sublimes
(goes from ice directly to gas without turning into liquid) if there is
not enough ventilation, then the buildup of carbon dioxide gas will
displace oxygen and there is a danger of suffication. Both of these are
concerns whenever we work with cold matter (liquid nitrogen, liquid
helium, dry ice, etc) and we have the appropriate setups in our
laboratories.
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A: FROM MENTOR MINI VARUGHESE IN MD
All your answers are on this website: http://www.dryiceinfo.com/

Thank you,
Mini