association constants for undefined organic soluble species

[joannadziadkowiec]

Hello PhreeqC users,

I am trying to define a new solution species. But I am confused with the log_k parameter. The literature I have is providing thermodynamic association constants as logBeta. Not sure if I can use it in PhreeqC?
(the reaction is the formation of Ca-succinate complex).

Would be grateful for the help!

[dlparkhurst]

I assume you can use log10(beta) as log10(K) in PHREEQC for the association reaction. There may be some subtleties as to whether beta refers to activities or concentrations, molal or molar scale, or refers to a specific ionic strength. Unless you are trying to be very accurate, I would just use the values from the literature, preferably from the lowest ionic strength medium; ideally, the log10 K is that for infinite dilution.