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A safe compound/solution with a melting point around -80 C

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juul:
I'm looking for a compound or solution with a melting point at, or close to, -80 C. It should remain liquid up to at least 50 C and should not be flammable or especially toxic.

I'm not really sure how to approach this problem so I'm not so much looking for someone to hand me the answer and more for a bit of guidance in what I need to understand and where I can learn more.

(btw I tried to read the rules first but clicking the link toward the top gives "Access denied for user ''@'localhost' (using password: NO)")

Mitch:
Try typing freezing points for common solvents into your preferred search engine. Here is a list I found.

https://www.chemistry.mcmaster.ca/mcnulty/Solvent%2520Properties.pdf

Thank you for pointing out the forum rules link is broken, we'll investigate.

Enthalpy:
Some silicone oils may fit your request. Wacker's AK10 has -80°C pour point, I didn't find its flash point immediately.

Alkanes are less easy, but phytane and farnesane fit. One expensive, farnesane was produced experimentally in kg quantity by
https://amyris.com/
Whether they went to mass production and sales? Or would you produce it, say from nerolidol or citronellal?
https://www.chemicalforums.com/index.php?topic=56069.msg338107#msg338107
https://www.chemicalforums.com/index.php?topic=56069.msg326163#msg326163
JP-10 = exo-tetrahydrodicyclopentadiene, a rocket and jet fuel used among others by cruise missiles, has mp=-79°C or -85°C and fp>+55°C
http://webbook.nist.gov/cgi/cbook.cgi?ID=2825-82-3&Units=SI
My frenzy about alkanes and amines with a wide liquid range, there:
https://www.chemicalforums.com/index.php?topic=56069.0

You might have a look at brake fluids and hydraulic fluids, but -80°C is uncommon for them. Airliners need such hydraulic fluids.

Some fluorocarbons would answer the request nicely but they are in the process of legal banning.

Could you detail the use or the additional desired properties? Good lubricant, insulator, cheap, transparent, long-lasting under sunlight and air, water-repellent, non-corrosive, good coolant...? Make or buy?

juul:

--- Quote from: Enthalpy on March 15, 2019, 08:06:58 AM ---Could you detail the use or the additional desired properties? Good lubricant, insulator, cheap, transparent, long-lasting under sunlight and air, water-repellent, non-corrosive, good coolant...? Make or buy?

--- End quote ---

Wow thanks for all that info! I'll look into your suggestions immediately. The use is as a thermal buffer to prevent biomedical samples from rising much above -80 for some time during power loss for areas with unreliable power. Large enthalpy of fusion would be good. It will be sealed from sunlight and air. It doesn't have to be non-corrosive. The safer it is for humans and environment the better. No preference for make vs. buy.

Thanks again!

juul:
Oh and I should mention that keeping the cost down is important. We'll need at least 1000 ml of this per freezer backup unit.

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