99chemicals
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Crystal Growing problems
About 2 months ago I decided to do some crystal growing experiments. I made saturated solutions of Sodium Tetraborate, Potassium chloride, and Sodium
acetate.
I made the solutions concentrated enough that they started to crystalize after around 6 hours.
I have left them undisturbed in my basement for 2 months. As they crystalized the solution climbed out of the jar and on to the sides. I think this
is called "creep". It happened on my KCl and sodium acetate. Picture below is the KCl. You can see the white crystals on the outside of the jar. They
are easily removed just by touching the jar.
This picture below is the sodium acetate.
And this is the sodium tetraborate, it was left next to the KCl jar. The KCl appears to have climbed on to the Borax jar
even though they were only touching. I did not observe any creep from the borax it self.
Any body have suggestions on how to prevent this "Creep" and why it happens.
The KCl crystals were not very good but the Borax turned out ok.
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sargent1015
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I usually place or dangle seed crystals while the solution is crystallizing which typically works pretty well at preventing the creep. Also, a bigger
container for the volume of solution you're using should work too.
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Endimion17
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Evaporative creeping is usually considerably reduced or even eliminated by smearing the insides of the vessel with heavy inert grease because it's not
polar. In fact, if you smear the string holding the seeding crystal right next to the crystal, too, there's a little chance of crystals forming
anywhere in the vessel except at the seeding point.
Everything is concentrated at the seeding crystal, allowing you to make extremely large monocrystals, compared to the usual sloppy methods school kids
do for homework.
It's an old trick. It's not perfect because of the atmospheric dust which induces crystalization at the surface of the solution, but if you're
freakishly careful, you get great results.
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99chemicals
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Quote: Originally posted by Endimion17  | Evaporative creeping is usually considerably reduced or even eliminated by smearing the insides of the vessel with heavy inert grease because it's not
polar. In fact, if you smear the string holding the seeding crystal right next to the crystal, too, there's a little chance of crystals forming
anywhere in the vessel except at the seeding point.
Everything is concentrated at the seeding crystal, allowing you to make extremely large monocrystals, compared to the usual sloppy methods school kids
do for homework.
It's an old trick. It's not perfect because of the atmospheric dust which induces crystalization at the surface of the solution, but if you're
freakishly careful, you get great results. |
Thanks. I will try that sometime soon and hopefully get some nice crystals. Do you think that Vasaline (petrolium jelly) will work? If not what
kind of grease should I use?
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nerdalert226
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I believe Vasaline should work pretty well, But if you are leaving it for 2 months you may need to re apply every 2-3 weeks or so.
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Endimion17
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| Quote: Originally posted by 99chemicals | | Thanks. I will try that sometime soon and hopefully get some nice crystals. Do you think that Vasaline (petrolium jelly) will work? If not what
kind of grease should I use? |
It should work. I never used it for this purpose because I had a quantity of some other grease available, but I think it should work just as fine
because it's inert towards most inorganic compounds.
Be sure to apply it generously, i.e. don't just smear it in a thin layer like when you lubricate glassware stopcocks.
And of course, remember not to pour in the hot solution. The "melting" poing of white petrolatum is lower than 40 °C, so the best is to pour a room
temperature solution in the vessel, and to do it carefully, to avoid disrupting the layer.
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