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Slow precipitation of calcium carbonate.

by duke656
Tags: calcium, carbonate, precipitation, slow
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Jan30-14, 11:13 PM
P: 15
Hello Everyone,

I am working with CaCO3. I want to have the precipitated CaCO3 in the laboratory. The easy way is to mix Na2CO3 and CaCl2. It gives CaCO3 and NaCl but this reaction takes place in a flash. As the reaction rate is high the produced CaCO3 forms powder like substance (the syze of crystals are very small) and they do not bond well with each other.

I want to increase the size of the crystals. I think I need to reduce the rate of reaction to get the bigger crystals. I have tried mixing at the lower temperature but the reaction again takes place in a flash and the product is always in the form of powder.

Now I am thinking of some new chemicals that will decompose slowly to give either calcium ion of carbonate at a slow pace. Do you know any such chemicals?

Urea can also give carbonate ion slowly. Do you know how to dissociate urea?

Thank you all for your support.

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Jan31-14, 02:45 AM
Borek's Avatar
P: 23,731
First of all, try if aging the precipitate doesn't help - keep the solution warm for several hours. Small crystals are thermodynamically less stable than the larger ones, so they should disappear and the large ones should grow.
Feb2-14, 10:37 PM
P: 15
Thank you Borek, I will try it.

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