What is colder than Liquid Nitrogen?
The dark side of the moon (Thank you, Pink Floyd). More exactly, large areas of the moon's south pole appear to be permanently dark. It has been calculated that temperatures in these permanently dark areas may be as cold as 40° to 50° Kelvin (-230° to -220° C), only a few tens of degrees above absolute zero. Not to mention the surface temperature on Pluto. Temperatures on the surface of the planet range from -387° Fahrenheit to -369° Fahrenheit, about -233° Celsius to -223° Celsius. And so on.
Which is colder, liquid helium or liquid nitrogen?
Nitrogen condenses at 77.36 K and solidifies at 63.15 K (at standard pressure). Apart from helium (which condenses around 4 K) there is liquid hydrogen, liquid argon, (by logical extension also liquid neon) and even liquid oxygen which condenses at lower temperatures. It might be possible to keep nitrogen in a liquid state below 63.15 K at higher pressure, so you cannot rule out that non-boiling liquid nitrogen is colder than 77.36 K.
Where can i get liquid nitrogen?
Generally speaking it's not hard to buy liquid nitrogen from a welding supply shop, gas supplier or cryogenics company, but you have to bring your own Dewar and they won't fill anything other than the proper kind (at least they shouldn't). You might find a welding shop that rents Dewars, or you can buy one for about $300. You can contact your nearest gas supplier or cryogenics company. Price depends on quantity but for smaller quantities it usually costs around three dollars a litre.
Is liquid nitrogen or liquid oxygen colder?
nitrogen bp: -194°C oxygen bp: −183°C