In order to evaluate the solubility of hydrogen in polycrystalline alpha-alumina used as a proton conductor, the amount of absorbed or desorbed hydrogen based on the change in the polarization conditions of the specimen was measured by a coulometric method based on an electrochemical cell using CaZrO3 (+In2O3). The hydrogen chemical potential profile in the specimen was calculated for various states of imposed voltage. The solubility of hydrogen was evaluated from the measured amounts of the absorbed or desorbed hydrogen on the changes in the imposed voltage and the corresponding change in the potential profile. The obtained value of the maximum solubility in the hydrogen atmosphere was (2.0 +/- 1.6) x 10(-7) mol cm(-3) and found to be independent of temperature in the experimental range of 1273-1573 K. (c) 2011 Elsevier B.V. All rights reserved.