About Dry Ice

zaveri
Member • Oct 14, 2013

About Dry Ice

Here are a few questions about dry ice:

1) how exactly is it prepared ?

2) how long can it remain in solid state once exposed to room temperature ?

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Sarathkumar Chandrasekaran

Member • Oct 15, 2013

1)Dry ice is a solid form of CO2 and it is usually dangerous and cannot be handled without any precaution because it can burn hands due to frostbite.It usually employs two phase transitions namely:gas to liquid and liquid to solid.
First a gas rich in CO2 is compressed and refrigerated and it turns to liquid CO2. After this process the pressure is released hence it changes to gas.During this transition there is a sudden decrease in temperature so that SOlid CO2(dry ice) is formed. Used as a preservative and cooling agent.
2)If stored in a cooler it sublimates(changes to gas) at a rate of 5 to 7 pounds(2.25kg to 3.1kg) for every 24hours.

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Ramani Aswath

Member • Oct 15, 2013

Dry ice is solid CO2 as Sarath says. Anyone can make dry ice with a domestic pressure cooker if a CO2 cylinder is available. I have done it myself.
A freely fitting cylindrical wooden plug with a small central hole is put into a pressure cooker. A rubber tube (preferably silicone rubber) from the cylinder outlet after the regulator valve is introduced through this hole to the base of the cooker. The valve is opened and the gas allowed to expand around the plug after a while dry ice collects under the plug. This happens since the ambient temperature is below the inversion temperature of carbon dioxide.

You can allow the gas to expand through a porous material like a multi layer cloth bag. This also produces dry ice with a somewhat larger waste of gas.

The catch? The process wastes a lot of the gas.

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zaveri

Member • Oct 15, 2013

what would happen if it was stored in a hot environment ?

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Ramani Aswath

Member • Oct 15, 2013

It will evaporate and become CO2 gas again.

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zaveri

Member • Dec 9, 2013

Now what would happen if dry ice was kept submerged in a large container of water ? would it remain solid for ever ? or would it melt at a slower rate ? would it cool the water in which it was kept submerged ?

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Ramani Aswath

Member • Dec 10, 2013

It is hazardous if the dry ice is in a sealed container. Water will just evaporate it to CO2 gas. Very high pressures can develop in sealed containers. Water even at 0 deg.C is 80 degC hotter than dry ice and will melt it fast. The water will get cooled as the latent heat of vapourization of dry ice has to come from it.

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