Freezing liquid Nitrogen.

4C20.40 • C+80+2

diagram for demo

Solid Nitrogen: Liquid Nitrogen freezes under vacuum. Liquid Nitrogen is placed in a shallow pyrex dish inside a heavy-walled black aluminum cylinder with a thick flat glass top. The vacuum pump lowers the pressure, causing the nitrogen to freeze in about 3 minutes. TV monitor shows Nitrogen freezing. TRIPLE POINT.

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