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Updated: Jul 15, 2026

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Using UCODE_2005 and PHREEQC to determine thermodynamic constants from experimental data
Magnus E Skold1, Geoffrey D Thyne, John E McCray
1Arcadis G&M, Inc., Highlands Ranch, CO 80129, USA. mskold@arcadis-us.com
Abstract:
This article presents a method for estimating chemical thermodynamic constants from experimental data using the two computer programs UCODE_2005 and PHREEQC. As an example, the conditional stability constant for lead (Pb) complexation by a remediation agent (carboxymethyl-beta-cyclodextrin) is estimated, but the method can be applied to estimate other thermodynamic parameters such as sorption constants and degradation rate constants. Advantages of this technique include estimation of uncertainties associated with estimated parameters, evaluation of information content of observations, statistical evaluation of the appropriateness of the conceptual model, and statistical-based comparison of different models.
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