The meaning of logK in the database

[Mr.white]

In the database, does the definition of logK refer to the solubility data of a species at different temperatures under 1 atmosphere, fitted into this formula?  logK=A1+A2*T+A3/T+A4*logT+A5/T2

[dlparkhurst]

Yes. It is called an "analytical expression" in the documentation, and it is used whenever it is defined for an aqueous species or phase. If there is no analytical expression, the delta_H is used in the Van't Hoff expression to determine the temperature dependence of the log_k. If neither Van't Hoff nor analytical expression are defined, the log_k is constant at all temperatures.