ChatterBank0 min ago
Cold Fingers, Vacuums and Liquid Nitrogen
Why is lquid nitrogen used to cover the cold finger in a vacuum set up?
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The idea is that you have a vacuum and sometimes heat to draw off volatile components from a mixture. You use the cold finger to ensure any volatile components drawn off condenses on the cold finger and are not sucked off down the vacuum line. You want the cold finger to be as cold as possible hence the use of cardice/acetone (-78 oC) or, better still, liquid nitrogen (-196 oC).
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