Simultaneous Quantification of Hydride Ions and Electrons Incorporated in 12CaO•7Al2O3 Cages by Deuterium-Labeled Volumetric Analysis

An extended volumetric method, combined with quadrupole mass spectroscopy (QMS), is proposed. This method enables us-to distinguish and simultaneously quantify hydride (H-) ions and electrons (e(-)) incorporated in cages of 12CaO center dot 7Al(2)O(3) (C12A7), which is accomplished upon annealing with CaH2. When a sample is dissolved in a deuterium chloride solution, most of the H- ions and electrons released from cages react to form HD and D-2 molecules, respectively. These isotope-labeled molecules are then detected by QMS. We have used this method to follow the concentrations of H- ions and electrons in C12A7-treated CaH2 over the thermal treatment time. We found that during the initial seven days of treatment, both concentrations increased. Thereafter, the electron concentration begins to decrease, while the H- ion concentration continues to increase toward the theoretical maximum. This diverging behavior is due to differences in their diffusion ratios and thermodynamic stabilities.