Why is a liquid nitrogen canister not cold on the outside when inside the temp of the sealed liquid is -320F? ...or IS the inside temperature ambient temperature? Surely the insulation of the container is not sufficient to seal in that cold? I.e. if you had an unsealed bowl of liquid nitrogen with the same thickness of the sealed canister surely the temperature of that bowl on the outside would be cold? 
 A: Liquid nitrogen is usually kept in a Dewar flask.  This flask protects the liquid nitrogen against all three kinds of heat transfer, as follows:


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*Convective heat transfer is largely eliminated because there is a hollow space inside the flask, between the outer and inner walls (or "containers") of the flask.  This hollow space often is vacuumed out to eliminate heat convection via air.

*Conductive heat transfer is largely eliminated because the inner container only touches the outer container at the very top of the flask, so any heat conduction from the mouth of the flask must travel the maximum path length to get to the liquid nitrogen.  Accordingly, the rate of conductive heat transfer is minimized by doing this.

*Radiative heat transfer is largely eliminated by putting a mirror finish on the outside of the inner container.
All of these techniques mean that heat transfer from the outside of the Dewar flask to the inside of the flask is minimized, and as a consequence, the outside of the flask does not feel cold.
For more info, see the following articles on Wikipedia:


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*Vacuum Flask 

*Cryogenic storage dewar
