My Rochelle Salt Crystals Won't Grow

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My Rochelle Salt Crystals Won't Grow

Postby love_dust2 » Sun Sep 23, 2012 2:51 am

I'm doing this for a project, but it won't grow. WHY? I've followed the procedure from cover to cover, but it won't work! Any tips?

Also, I'm planning to buy a powdered version of it. Does it exhibit piezoelectricity still? Or do I need to dissolve it in water to make it grow crystals?
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Re: My Rochelle Salt Crystals Won't Grow

Postby John Dreher » Sun Sep 23, 2012 9:00 am

love_dust2 wrote:I'm doing this for a project, but it won't grow. WHY? I've followed the procedure from cover to cover...


Welcome to the Forum love_dust2.

I can't find the project and it's procedure. Could you please provide the URL? (You can copy this from the location field in the toolbar of your browser when you are looking at the project web page.)

Thanks. I hope we will be able to help.
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Re: My Rochelle Salt Crystals Won't Grow

Postby Craig_Bridge » Thu Sep 27, 2012 2:52 pm

Growing any salt crystal usually requires you to start with an excess of disolved salt in solution, filter or decant the solution to remove the excess undisolved material, then let evaporation or reduction in temperature cause the salt to precipitate out of solution. If you don't provide a "seed", you will end up with lots of little crystals instead of a larger ones.

love_dust2 wrote:I'm planning to buy a powdered version of it.

If you didn't start with powdered Rochelle Salt (potassium sodium tartrate), what did you start with to make your super saturated solution?

If you start with Rochelle Salt crystals instead of powder, you can use a mortar and pestle to grind the crystals into a fine powder.

The most common initial mistake in starting a crystal growing experiment is not getting enough disolved at a high enough temperature to create a super saturated solution. Starting with a fine powder reduces the amount of stirring and time it takes to disolve enough salt to get to a super satruated solution instead of ending up with an unsaturated solution and undisolved salt and not waiting long enough for enough evaporation to super saturate the solution.

At room temperature, a saturated solution is 63 g/100 ml (20 °C). The melting point is 75°C. So if heat 126 g/100 ml until it disolves, you will definitely have a super saturated solution that will quickly cause crystals to form as it cools below 75°C. If you cast a pinch of some crystals into the mix as lots of small crystals are forming, they are likely to act as seeds and grow as they fall to the bottom. You can the remove the largest crystals, reheat the remainder until it melts/disolves and the start the cooling process, wait for crystals to start forming and cast in the crystals you saved from the first time and to form some even larger crystals.
-Craig
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Re: My Rochelle Salt Crystals Won't Grow

Postby rkpingali » Thu Nov 08, 2012 6:52 pm

To summarize, crystal making is as much as an art as it is science. Three important points to remember for good crystal growth:
1. Super Saturated solution
2. Slow evaporation
3. Seed

You can google and find out more on each of these points.

Good Luck! and send us a picture of your biggest crystal :-)

Raji Pingali
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