Dear Dr. David Parkhurst, I wonder if you can advice about the stability constant used in the PHREEQC.dat database for hydroxyapatite (-3.421). In the data base MINTEQ.dat this constant is much lower (given as -44.333 which corresponds to -7.149 if reaction is written as in PHREEQC.dat). The constant of MINTEQ.dat is similar to the constant given by Lindsay (1979) which is -7.14 (using the same presentation of the dissolution reaction). Data of my research with soils seems to fit well with the constant used in PHREEQC.dat, but I had difficulties to point a reference for this constant. I would appreciate if you could inform me of a reference for this constant. Thanks, Moshe Shenker
************************************************* Dr. Moshe Shenker Department of Soil and Water Sciences Faculty of Agricultural, Food and Environmental Quality Sciences The Hebrew University of Jerusalem, Rehovot 76-100 Israel
Phone - 972-8-9489349 Fax - 972-8-9475181 E-mail - Shenker@xxxxxxxxxxxxxxx *************************************************
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