As an alternative, the voltage data of Kurita et al. recently published on galvanic cells with commercial alpha-Al2O3 as a solid electrolyte and with O-2, H2O/alpha-Al2O3 as well as H-2, H2O/alpha-Al2O3 as electrodes can be quantitatively described by assuming that alpha-Al2O3 represents a mixed sodium ionic-electronic conductor rather than a protonic-electronic conductor. From the evaluation of the experimental data, numerical values for the p-type electronic conduction parameter are obtained that agree sufficiently well with the data known to date for the sodium ion conductor Na-beta-Al2O3.