Slow precipitation of calcium carbonate.

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SUMMARY

The discussion centers on the precipitation of calcium carbonate (CaCO3) in a laboratory setting, specifically the challenge of producing larger crystal sizes. The reaction between sodium carbonate (Na2CO3) and calcium chloride (CaCl2) occurs rapidly, resulting in small, powdery CaCO3 crystals. To address this, participants suggest methods to slow down the reaction rate, including the use of urea to release carbonate ions gradually and the technique of aging the precipitate to promote crystal growth. The importance of maintaining a warm solution during this process is emphasized to enhance the stability of larger crystals.

PREREQUISITES
  • Understanding of chemical precipitation reactions
  • Familiarity with calcium carbonate and its properties
  • Knowledge of reaction kinetics and temperature effects
  • Basic chemistry of urea and its dissociation
NEXT STEPS
  • Research methods for controlling reaction rates in precipitation reactions
  • Explore the use of urea in chemical processes and its dissociation mechanisms
  • Investigate techniques for aging precipitates to enhance crystal growth
  • Study the thermodynamics of crystal formation and stability
USEFUL FOR

Chemists, laboratory technicians, and researchers involved in materials science or chemical engineering, particularly those focused on crystal growth and precipitation processes.

duke656
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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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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.
 
Thank you Borek, I will try it.
 

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