How to Get Ultra-low Temperature Like -196 C

Try this.

Liquid Nitrogen, it boils at -195.79C.

That's good unless you need -196 C to make liquid nitrogen...

You are right of course, but the OP doesn't state what he needs -196C for. For all I know, he trying to get a record for overclocking an old AMD cpu.

Homemade liquid nitrogen generator

Very interesting. I have a wafer of "high" temperature superconductor that I've always wanted to play with but have never located a supply of liquid N₂ and I have wondered about making it.

However, 3500 psi sounds like it should be treated with respect!

Praxair sells LN. I don't know if you can rent a cryostat but you probably can for a nominal fee and a deposit. I used to bring my LN home years ago in a good vacuum-bottle-type Thermos, for my high-temp superconductor. Just make damn sure you don't tighten the cap.

note to self: don't tighten cap on boiling liquid! whew, I feel we've dodged a bullet there....

This is a public forum which any visitor can read. You know as well I do a lot of people come here who have no common sense and wouldn't know not to do this, some of whom may have access to LN on the job and may want to bring some home for whatever reason. To you it may seem I am unnecessarily pointing-out the obvious, but to someone else this may not be obvious at all, they tighten the lid - and end up with shrapnel in their guts.

Are we now clear on this, Mr. Snarky, seeing as this aspect wasn't obvious to you at all?

note to self: Andrew has no sense of humor....and a thin skin

Justify your comments however you like. I couldn't care less.

What I do care about are readers maiming themselves because they don't know to take certain precautions when dealing with materials of this sort.

You definitely need some more precautions if you feel your suggestion of obtaining through Praxair gives you liability (moral or legal).

It would be good to advise against swallowing.

It would be good to caution about frostbite.

It is very important to note suffocation hazard in spaces not well vented.... if they just loosen the cap, they might die sooner than had the thermos exploded.

Reader take note ⇑

..not so ridiculous after all..

I wasn't going for ridiculous, just thinking of accidents. There was an instructor who was going to demonstrate Leidenfrost effect by holding ln in his mouth. He got confused and swallowed some which landed him blacked out in the ER in short order.

Can't find that particular 1st person essay, but here is indication of at least two more.

A professor? That's ridiculous in and of itself.

Perhaps he should have been honest and said he was doing a demonstration of how to be a contender for the Darwin award.

Maybe he was trying to demonstrate how to make ice cream in the stomach.

Nothing like a near death experience to motivate one to educate one's self about the materials one is dealing with....

I do appreciate your concern, but given some of the questions I have seen asked on this forum...

I think he was being ultraliteral....as in dodging shrapnel....or bullets from an exploding sealed container.

Rixter, how long have you had your HT superconductor? I'm asking because I noticed that mine began to crumble some years after I bought it. You may wish to vacuum-seal yours until you're ready to use it. Also to dry it thoroughly (by baking at a low temperature) after use as it will quickly become covered in frost.

I've had it for a long time. I'm not sure where it is right now, but the last time I saw it, it seemed OK. (I believe it's YBCO, Yttrium Barium Copper Oxide.)

To reduce the temperature below n2 boiling point at atmospheric pressure, the boiling point of n2 can be reduced with a decrease in pressure via vacuum pump.

The heat removed by evaporation of n2 at reduced pressure can bring the temp low enough to freeze n2 solid.....somewhere around -210° C.

I tried this with a Styrofoam cup filled with LN, which I placed inside a vacuum desiccator (whose lid I replaced with a 1"-inch-thick slab of Plexiglas so I could see what was going on). About 2/5 of the LN boiled away before the rest froze.

You can also do it with liquid helium.

Several years ago one job I had involved inspection of two MRI installations.

LN2 was used to cool down the magnet windings to about 77 deg K, then LHe introduced and run through the whole assembly until no N2 was detected in outlet stream.

when I asked the installer if the the LHe would freeze the LN2 solid, he xplained that that's exactly what could happen.