The protonation-dehydration equilibria of several diaryl, triaryl, and diarylalkylcarbinols leading to carbenium ions have been investigated by the excess acidity method. The results are firstly employed for an assessment of the acidity functions (H-R and H-R) determined from those data. It is shown that both acidity functions are faulty in several respects, e.g. because they were determined from indicators for which parallelism of plots was hardly attained. In contrast, the excess acidity method is shown to yield protonation parameters (m* and pK(R+)) which can be interpreted in terms of structural and solvation effects on the stability of carbenium ions. The relationship of these parameters with enthalpies of reaction with FSO3H is also discussed
