Ask A Scientist Chemistry Archive

Question:  I am a student in Japan and for a Science project I am 
doing how crystals are formed using epson salts and other materials.  
Could I please have some information on how the process works?
 mark c amlin

Answer:
Basically you start with a solution (dissolve the material in some solvent)
or a melt (heat the material until it melts).  If you are working with a
solution you need a saturated solution, that is, you slightly heat the
solvent and add material (epson salts), with stirring, until no more will
dissolve.  At this point you have a little bit of the solid left in the
container and you heat it a little more so that that dissolves too.
Now you let the container cool slowly.  As it cools it reaches a temperature
at which the solution cann't dissolve as much material as you dissolved in
it at the higher temperature and the epson salts begin to crystallize out.
(You may need to add a "seed" crystal to get it started.)  To get large,
high quality crystals you want to keep the solution close to the equilibrium
temperature as the crystallization proceeds (this means you control how
quickly it cools so that it doesn't all crystallize out -- in many small
crystals -- at once).
Hope this helps.
 gregory r bradburn