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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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