Dear David Parkhurst, In the PHREEQC database there is two equations for CaCO3: Ca+2 + CO3-2 = CaCO3 log_k 3.224 Calcite CaCO3 = CO3-2 + Ca+2 log_k -8.480 Which one of the equilibrium constants is used by PHREEQC to calculate the solubility constant? If both this constants are used doesn't the model became unstable. Best Regards Pedro Chambel Leitão ~~~~~~~~~~~~~~~~~~~~~~~~~~ IST - MARETEC Taguspark Núcleo Central, Sala 363 2780-920 Oeiras, Portugal Tel.: +351 21 4239016 Fax: +351 21 4211272 URL: http://www.mohid.com
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