I am making a synthetic solution to imitate a real life situation. I am adding calcium nitrate to the solution to meet a target calcium level of $\pu{334 ppm}$. However, using excel calculations the amount of calcium nitrate that is needed imparts a total of $\pu{522 ppm}$ calcium. I am also adding $\pu{100 ppm}$ calcium carbonate which will increase the levels of calcium. My supervisor said I need to add nitric acid to lower the calcium imparted by the calcium nitrate. How and why does that work? and what calculation do I need to do to figure out how much nitric acid I need to add?

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    $\begingroup$ Hi, and welcome to Chemistry SE. In order for us to help you, it would be useful for us to see your any work you have done and where you are having trouble. $\endgroup$ – Michael Lautman Jun 3 '19 at 1:23
  • $\begingroup$ I don't think nitric acid is the solution. I think your supervisor meant oxalic acid. In that way, excess $\ce{Ca^2+}$ ions may precipitate as calcium oxalate. Phosphoric acid may work as well. $\endgroup$ – Mathew Mahindaratne Jun 3 '19 at 2:10
  • $\begingroup$ Could you list all the concentrations you would like to achieve in this solution? Right now it is not clear what is "forcing" you to add more calcium than you need. $\endgroup$ – Karsten Theis Jun 3 '19 at 22:03