A method in pH and b calculation is algebraic
method under specific assumptions for each system.
This assumption-dependent algebraic method is
inconvenient to predict pH of a multi-component
solution. Butler (1964) described a unified concept
to calculate pH of a solution by writing and solving
two equations from three possible equations, i.e.,
proton balance equation (PBE), mass balance
equation (MBE) and charge balance equation
(CBE). The variables appeared in these equations
relate to each other by dissociation constant of
solutes in a solvent. If these relationships could be
solved and as long as no constraints were involved,
pH prediction of a solution containing various acids,
P. Boonme et al. Silpakorn U Science & Tech J Vol.6(2), 2012
21
bases and/or ampholytes would be possible. If in the
situation with constraints, other parameters should
be mutually considered. Nevertheless, solving
simultaneous equations would be ending up with
high-degree nonlinear-multivariate polynomial
equations. Since the root of the equation must be
solved with numerical method, it may not be suitable
for database purpose due to the complexities in the
calculation process.