Simultaneous quantification of hydride ions and electrons incorporated in 12CaO·7Al 2O 3 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·7Al 2O 3 (C12A7), which is accomplished upon annealing with CaH 2. 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 CaH 2 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. © 2012 American Chemical Society.