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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: rep353 on February 28, 2011, 07:14:56 PM

Title: Making good crystals - tips?
Post by: rep353 on February 28, 2011, 07:14:56 PM

My chemistry class are hoping to enter into a crystal growing competition. We will be making crystals from alum. We will also use pure water in the process.

What is the best procedure to make the best quality crystal and with good aesthetic quality?

Title: Re: Making good crystals - tips?
Post by: Fluorine on February 28, 2011, 11:07:07 PM

Don't shake/disturb the container and be patient. Also depending on how much time you have consider redissolving the solution and evaporating again. I got fair size crystal by doing this but we had an extended duration to turn them in.

Title: Re: Making good crystals - tips?
Post by: opti384 on March 01, 2011, 12:09:08 AM

You should not definitely shake or disturb it. Also, leave it where it's cool.

Title: Re: Making good crystals - tips?
Post by: rep353 on March 01, 2011, 12:31:05 PM

Are there any good procedures?

Title: Re: Making good crystals - tips?
Post by: jeffrey.struss on March 01, 2011, 01:56:02 PM

Slow evaporation, undisturbed works the best for high school level stuff.

There are more advanced techniques for when you crystals for x-ray diffraction. Things like solvent vapor diffusion, using an NMR tube that has been thinned and freezing your solvent with the analyte and layering an opposite polarity solvent on top to allow gradual diffusion. Heavily cooling down the reaction mixture and just letting it sit. etc. etc. etc.

Title: Re: Making good crystals - tips?
Post by: Borek on March 01, 2011, 02:40:56 PM

http://lmgtfy.com/?q=how+to+grow+crystals