Isaac Summer - 3-10-2013 at 15:07
I am a newbie here, but I am jumping in without extensive measurement of the depth of the pool. Based on the intelligence I have seen reading some of
the threads I am confident you folks will not be annoyed by my contributions.
Two methods bubble up to the surface when I think of growing crystals.
1. Evaporate a saturated solution.
2. Slowly cool a saturated solution made at elevated temperature.
I have a different idea I would like to submit. First, the apparatus:
A one foot tall three to four inch diameter cylindrical glass container (commonly found in craft stores, Target, etc) is placed in a box constructed
to allow 3 or 4 inches of the bottom of the vessel to be contained in the box and supported within such that a small incandescent appliance bulb can
be placed below it. The box is insulated and the vessel is filled with a saturated solution of the material to be crystallized. Let's use copper
sulfate in this example. A lid is placed on the top, but this should not be a hermetic seal. It should allow exit of higher than atmospheric pressure.
200 grams of coarse CuSo4 are placed into the vessel, A controllable voltage is applied to the light-bulb, a thermometer is placed into the bottom
of the vessel and the system allowed to reach equilibrium.
I am guessing at the target temperature, wattage of the bulb, etc...
These are all ballpark figures. I believe that if we can pad the voltage from zero to 120, we can arrive at a workable system. I am shooting for a
temperature of about 120 degrees F.
After the system is in equilibrium, a seed crystal is immersed in the top few inches of the vessel. The heated solution rises to the top, deposits
some material on the seed, and sinks to the bottom to pick up more material.
The voltage must be adjusted to allow the best rate of growth for good crystals. Once done, we can maintain the system by adding crystals to the
bottom as they are consumed. This should be a sustainable method and would be ideal for systems where the solubility of the solid is low, and the
solvent is expensive.
I would love to hear what you have to say about this idea, and plan to implement such a system soon, and report my success or failure.
Thanks in advance for your thoughts!
Wizzard - 3-10-2013 at 17:31
This is how crystals are grown in slightly more complex, but still common machines.
Here's the same apparatus you describe, which I used to grow sulfur crystals with toluene (when I could still get my hands on that precious paint
thinner).
http://www.sciencemadness.org/talk/viewthread.php?tid=20937
Tilting the vessel provides the flow you'd want for this to occur best. This can allow continual crystal growth, so long as a great amount of inital
material can rest at the "hot bottom" or can be added with another access tube, unvented and kept hot.
Lastly, the better temperature solubility differential you can cause, the better. Some work best hot->warm, some hot-> cold, some even
warm->freeing, and I tried growing my solfur in a freezer as hot->freezing (with limited success). Inverse solubility curves are incompatible -
The warm material will remain at the top!