The liquid nitrogen in a Dewar absorbs heat slowly from the surroundings, resulting in pressurized gaseous nitrogen forming inside. This higher-than-the-surroundings pressure keeps the air (and oxygen) out of the Dewar and also is used to push the liquid nitrogen out when the valve marked LIQUID (draws from bottom of tank) is opened. A pressure relief valve limits pressure to safe levels.
When liquid nitrogen flows through uninsulated tubing or piping, a layer of water ice and dry ice form. I used to work in a lab where we used liquid nitrogen to cool gas chromatograph tubes and never had an explosion. I can see where liquid nitrogen in an open container would absorb oxygen, but I can't imagine dunking an operating chip in that sort of container anyway.
And now for some verse:
Sir James Dewar Is a better man than you are None of you asses Can liquify gases.
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The liquid nitrogen in a Dewar absorbs heat slowly from the surroundings, resulting in pressurized gaseous nitrogen forming inside. This higher-than-the-surroundings pressure keeps the air (and oxygen) out of the Dewar and also is used to push the liquid nitrogen out when the valve marked LIQUID (draws from bottom of tank) is opened. A pressure relief valve limits pressure to safe levels.
When liquid nitrogen flows through uninsulated tubing or piping, a layer of water ice and dry ice form. I used to work in a lab where we used liquid nitrogen to cool gas chromatograph tubes and never had an explosion. I can see where liquid nitrogen in an open container would absorb oxygen, but I can't imagine dunking an operating chip in that sort of container anyway.
And now for some verse:
Sir James Dewar
Is a better man than you are
None of you asses
Can liquify gases.