Slow precipitation of calcium carbonate.


by duke656
Tags: calcium, carbonate, precipitation, slow
duke656
duke656 is offline
#1
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.

Duke
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Borek
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#2
Jan31-14, 02:45 AM
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P: 22,708
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.
duke656
duke656 is offline
#3
Feb2-14, 10:37 PM
P: 15
Thank you Borek, I will try it.


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