Esquathriel
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Salts in Vapor?
Hey, ScienceMadness! This is my first post, so forgive me if it's placed incorrectly.
I observed something interesting while growing crystals of Cu(SO4): crystals began growing first up, and then down the side of my beaker,
margarita-salt style. I thought this was peculiar. It began above the top of the saturated Cu(SO4) solution, and grew down until about that same level
on the outside. It even began growing on the glass rod suspending the seed. I cleaned it off before it could consume the entirety of the beaker
because I thought it actually might and it'd be more of a pain than this already was to clean up.
I'm wondering if there really are copper and sulfate ions floating around in the vapor? And enough to crystallize on the side of the beaker should be
dangerous to breathe, no?
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j_sum1
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This is called creep. I have not observed it much with copper sulfate but it can be a pain with some crystallisations. I have seen urea climb out of
a beaker and form a "frost" all over the bench.
It happens due to capillary action and not vapour. The newly-formed crystals draw solution away from the rest of the liquid by capillary action:
forces related to the surface tension of the liquid. Then the solvent evaporates forming additional crystals at quite some distance from where the
liquid started from.
This phenomenon is sometimes used in novelty items that are sold commercially as "crystal gardens" or "christmas trees". In these situations there is
supplied a shaped piece of porous cardboard to aid the capillary action and cause the final product to conform to a particular shape.
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j_sum1
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Thread Moved
6-6-2018 at 17:20 |
fusso
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Actually is there any ways to prevent crystals creeping up and out of the container? It's rly pita to lose product crystal due to this.
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MrHomeScientist
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j_sum1 summed it up nicely. I had one extreme case where I forgot about a beaker at the back of the bench, and when cleaning up I discovered crystals
had crept up the side of the beaker, down the outside, and across the table for about 8 inches. It looked just like I had spilled the liquid and let
it evaporate; it just happened a lot slower!
One way to prevent this that I've heard of but never tried is a thin layer of petroleum jelly, around the rim or somewhere above the water line.
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DoctorPhilosophy
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Must be related to hydrophobia and hydrophilia.
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walruslover69
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I grew copper sulfate crystals in my gen chem lab and similar to what homescientist said used a wax pencil to trace a line a couple inches above the
water line to prevent creep. I think I remember it working well.
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