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Topic: Evaporating salt solution  (Read 2534 times)

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Offline nellocin

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Evaporating salt solution
« on: July 11, 2012, 08:05:34 PM »
I was messing around with a saturated solution of table salt, when I forgot about it and left it in a fume hood over night.  When I came in the next morning the solution had evaporated away, but what surprised me was that there were salt deposits left on the beaker above the initial height of the solution. In fact this is where most of the salt ended up, including some creeping over the top of the beaker.  How do I understand this observation?

My expectation was that the water would evaporate molecule by molecule, leaving the salt in the bottom of the beaker.  However if the solution evaporated drop by drop, then some drops might hit the side of the beaker on their way out where it could condense leaving salt behind - but this doesn't make sense with the way I understand evaporation.

Any ideas?

Offline Arkcon

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Re: Evaporating salt solution
« Reply #1 on: July 11, 2012, 08:52:49 PM »
Sometimes, as crystals form, they function as a wick for more solution to absorb, and ends up creeping along.  This dendritic crystal growth happens sometimes, and chemicals can even creep out past screw threads of a sealed bottle.  This is a way for crystal gardens to grow, a common kid's experiment: http://www.chemicalforums.com/index.php?topic=29210.msg111267#msg111267
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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