# Looking for a very "cold" compound

**URL:** <https://boards.straightdope.com/t/looking-for-a-very-cold-compound/113744>\
**Category:** Factual Questions\
**Created:** [June 12, 2002, 11:22pm UTC](https://boards.straightdope.com/t/looking-for-a-very-cold-compound/113744 "2002-06-12T23:22:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Belgarath](https://avatars.discourse-cdn.com/v4/letter/b/278dde/32.png) [@Belgarath](https://boards.straightdope.com/u/Belgarath)\
**Post date:** [June 12, 2002, 11:22pm UTC](https://boards.straightdope.com/t/looking-for-a-very-cold-compound/113744/1 "2002-06-12T23:22:47Z")

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Something along the lines of nitrous, however would not be used in the same manner. It just needs to be a very cold gas that can be released into the atmosphere. Also I need it to be fairly inexpensive and with decent availability. I wan tot use it as a pressurized cooling agent.

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**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\
**Post date:** [June 12, 2002, 11:59pm UTC](https://boards.straightdope.com/t/looking-for-a-very-cold-compound/113744/2 "2002-06-12T23:59:29Z")

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How so ? The proper choice of coolant depends on what you intend to do. Liquid nitrogen is cheap and easy to get in large cities. It readily turns into a _very_ cold gas. Dry ice + acetone (or isopropanol) can be had nearly anywhere, but falls a bit short on your requirement that the coolant be a gas. Freons are another possibility. If you don’t want to specify further, here’s a whole pile of information on [Gases and Refrigerants](http://www.google.com/search?site=swr&hl=en&lr=&safe=off&as_qdr=all&q=refrigerants&as_q=gases).

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**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\
**Post date:** [June 13, 2002, 4:22am UTC](https://boards.straightdope.com/t/looking-for-a-very-cold-compound/113744/3 "2002-06-13T04:22:55Z")

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Any gas is cold if you lower it’s temperature enough. Do you want a gas with a high Joules-Thompson coeficient? (The higher the JT coeficient the colder the gas gets as it expands. Freon is used in refrigerators because of this.) Or are you simply ineterested in getting a cold gas no matter what the energy cost of cooling it. In this case, choose anything you want. Helium will get the coldest, but good luck obtaining it.

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**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\
**Post date:** [June 13, 2002, 1:22pm UTC](https://boards.straightdope.com/t/looking-for-a-very-cold-compound/113744/4 "2002-06-13T13:22:40Z")

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> [@](#):
>
> \*Originally posted by Christopher \*  
> **Any gas is cold if you lower it’s temperature enough.**

For that matter, any _thing_ is cold if you lower its temperature enough.

Some people think liquid nitrogen is “cold.” This is incorrect; the temperature of liquid nitrogen depends on its environment. As an example, we have lots of LN[sub]2[/sub] containers where I work. The LN[sub]2[/sub] inside the container is _not_ cold! It’s at room temperature and under high pressure. Only when you vent it and allow it to boil does the immediate surrounding environment become cold.