A modification of the Bunnett-Olsen equation of the form
lg ([SH+])/[S]) - lg[H+] = m*X + pKSH+
where X is the activity function lg(
S
H+)/
SH+) for an arbitrary reference base. The function X is called the excess acidity because it gives a measure of the difference between the acidity of a solution and that of an ideal solution of the same concentration. In practice X = - (Ho + lg[H+]) and m* = 1 -
. COX and YATES (1978, 1981); LUCCHINI, MODENA, SCORRANO, COX and YATES (1982). See also Bunnett-Olsen equations.