calcium sulphate and calcium carbonate 1

[NMLS]

At what temperature does calcium sulphate and calcium carbonate deposit (precipitate)from water?

From my knowledge, calcium sulphate solubility increases as the temperature increases. Therefore, it wouldn't be the temperature of the water that would cause the CaSO4 to precipitate, but rather its saturation point. Is that correct?

Heating water that containes calcium bicarbonate, causes the formation of carbonate from the bicarbonate and thus calcium carbonate precipitates out of solution. Is it correct to say that calcium carbonate deposits around 100°C (boiling point of water at atmospheric pressure)?

 

[NMLS]

I have found some information on the internet. Calcium sulphate precipitates at 300°F or 149°C, which is a high temperature found in the boiler. Can anyone confirm this?
Thank you.

 

[kenvlach]

You are asking for a simple answer to a slightly complex problem without providing sufficient information.

Calcium sulfate can precipitate out at any temperature provided that the concentration product [Ca⁺²][SO₄^-2] exceeds the solubility product K_sp for that temperature. The solubility of calcium sulfate decreases as temperature increases above 38^oC. See 'Figure 3-4. CaSO4 solubility vs. temperature' (page 23, pdf page 33):

http://www.energy.ca.gov/2005publications/CEC-500-2005-170/CEC-500-2005-170.PDF