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Q & A: Liquid immiscible in water and oil

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Most recent answer: 10/22/2007
Q:
Is there a liquid that dissolves niether in water and oil?
- Syeda Khadija Fatima Zaidi (age 13)
Luther Jackson Middle School, Fairfax,VA
A:
Sure! Mercury is a liquid at room temperature and has a very low solubility in both water and oil -- the cohesive forces between mercury atoms are much stronger than those between water molecules and mercury atoms, and the same goes for the oil.

Be careful though -- mercury is poisonous.

There are some liquids which won't dissolve in either for a reason rather unrelated to miscibility. For example, liquid nitrogen is only a liquid at very low temperatures (below 77 Kelvin). Water and oil are frozen solid at those temperatures, and so dissolving is not an option (well, you can get a few molecules of nitrogen stuck inside the crystal lattice of water, so maybe that counts). The same goes for substances which are liquids only at very high temperatures , where neither the water nor the oil are liquid.

Tom

(published on 10/22/2007)

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