The ionic transference number of semiconducting Co1-deltaO has been me
asured as a function of oxygen activity in the entire stability range
of the phase at 1000, 1100, 1200 and 1300 degrees C, respectively, via
a modified Tubandt-like electrotransport technique. The transference
number falls in the range of 10(-6)-10(-4) and systematically exhibits
a minimum on each transference-number isotherm. The ionic conductivit
y is extracted by combining with the literature data on the total cond
uctivity of Co1-deltaO. Experimental details are given and the results
are exhaustively compared with the literature data. Non-negligible in
terference between the flows of ionic and electronic carriers is indic
ated.