MadSci Network: Chemistry

Re: please explain to me how dry ice is made

Date: Thu Oct 12 10:31:05 2000
Posted By: Lon Brouse, Faculty, Chemistry, Challenge Charter School
Area of science: Chemistry
ID: 971302443.Ch

Dear Mark,

Dry ice is made by compressing gaseous carbon dioxide to between 900 and 
1,000 pounds per square inch.  The compressed gas is cooled to remove the 
heat generated during compression.  It turns to liquid CO2 during this 
step.  The cooled liquid carbon dioxide is then sprayed into an enclosed 
expansion chamber where it expands to atmospheric pressure.  At this point 
it is about -70 deg. F.  

Some of the expanding CO2 is flash cooled during the process to about 
-110 deg. F.  This portion solidifies into 'snow' which is removed from 
the chamber and mechanically compressed into standard 50-pound blocks 
which measure 10 inches on a side.  This part of the process is much like 
making snowballs out of regular water snow.

I hope this helps.

The McGraw Hill Encyclopedia of Science and Technology, 5th Edition, 1982.

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