[Borek]

I haven't checked it. I relied on Certificate of Analysis of 99.5% pure CaCO3 that I dissolved in Nitric Acid.

Sounds reasonable.

Could be your water content is not what you expect it to be, I am afraid I can't be of help any further.

[BluRay]

I haven't checked it. I relied on Certificate of Analysis of 99.5% pure CaCO3 that I dissolved in Nitric Acid.

Did you boil the solution after having dissolved CaCO₃ with HNO₃? Otherwise you can have HCO₃^- ions which could keep Ca⁺⁺ ions in solution (if I remember well). Boiling the solution eliminates dissolved CO₂ and so H₂CO₃ and HCO₃^- ions.

[covek11]

No, I didn't boil it.

[Borek]

Otherwise you can have HCO₃^- ions which could keep Ca⁺⁺ ions in solution (if I remember well). Boiling the solution eliminates dissolved CO₂ and so H₂CO₃ and HCO₃^- ions.

In the presence of excess sulfuric acid HCO₃^- won't survive long enough in the solution.

Besides, I think you may be mixing two things - HCO₃^- doesn't 'keep' Ca²⁺ in solution, but Ca(HCO₃)₂ is much better soluble in water. Thus water kept over solid CaCO₃ will have higher concentration of Ca²⁺ when saturated with CO₂.

[BluRay]

In the presence of excess sulfuric acid HCO₃^- won't survive long enough in the solution.

Yes, but he said to have adjusted the pH to 7.

Besides, I think you may be mixing two things - HCO₃^- doesn't 'keep' Ca²⁺ in solution, but Ca(HCO₃)₂ is much better soluble in water. Thus water kept over solid CaCO₃ will have higher concentration of Ca²⁺ when saturated with CO₂.

You're right.