Sciencemadness Discussion Board - Crystal Growing problems

Crystal Growing problems

99chemicals - 5-5-2012 at 08:09

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.

sargent1015 - 5-5-2012 at 08:48

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.

Endimion17 - 5-5-2012 at 09:27

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.

99chemicals - 5-5-2012 at 16:54

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?

nerdalert226 - 9-5-2012 at 16:53

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.

Endimion17 - 10-5-2012 at 05:37

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.