HXC

Copyright Jrgen Prenzel 2001,2005
The program is licenced through the GPL (see LICENCE)

A program to calculate exchangeable H-ions from pH and Al
concentrations in salt extracts of soil samples.

Theory
======

The calculation is based on the idea that exchangeable H-ions acidify
the extract solution. But part of the observed acidification may stem
from hydrolysis of exchangeable Al-ions. The program tries to figure
out the correction for the latter effect. For this purpose the
hydrolysis of Al is calculated according to the stability constants as
given in the book by Baes and Mesmer. The calculation is done by
numeric iteration.


This theory has obvios shortcomings. The most important is that
organic complexing of Al is not included. An other is that all Al in
the extract is assumed to stem from 3-valent Al at the exchange
complex. Due to the shortcomings the correction term may be greater
than the amount of H-ions present, in this case a negative value for
exchangeable H results.

Usage
=====

There is a C subroutine that does the computation:

int akeh(double ph0, double ph1, double ctal, double str, double* exh);

There is also a main program HXC.c and, for Windows XP,
in compiled form: HXC.exe

The programs are published under the GPL (see file LICENCE).

There is some documentation in German in HXC.pdf.
