To clarify the thermochemical and thermionic properties of saline hydrides, a small amount (ca. 1 mg) of powdery NaH or LiH deposited on a molybdenum ribbon was heated up to ca. 1000 K either stepwise at ca. 10 K intervals or continuously at a constant rate (ca. 2-20 K/s) in vacuum (ca. 10(-4) Pa), and the desorption rates of H-2, electron (e(-)) and/or H- were measured mass spectrometrically as a function of the sample temperature (T), the introduced hydrogen gas pressure (P-H) or the time (t) after a change in T or P-H Theoretical analysis of the data thus achieved yields the following results: (1) In the temperature-programmed desorption spectra observed with NaH, both e(-) and H- showed a single peak at ca. 800 K while a broad peak of H-2 appeared around ca. 750 K. (2) The activation energies (E- and E-0) for the desorption of H- and H-2 from NaH were 172 +/- 18 and 61 +/- 7 kJ/mol, respectively, whilst the work function (phi) of NaH at those temperatures corresponding to the leading edge of an electron desorption peak was 261 +/-19 kJ/mol. (3) In the case of LiH, E-, E-0 and phi were 940 +/-89, 97 +/- 12 and 747 +/- 41 kJ/mol, respectively. (4) By the thermal dissociation such as LiH(solid) -> Li(solid) + H-2(gas)/2, phi was decreased by 20 kJ/mol or much more depending upon t or T, but the active spots (mainly Li) thus produced was destroyed by admission of H-2 up to ca. 10(-1) Pa. (5) The deactivation (Li + H-2/2 --> LiH) depending upon both T and P-H was readily recovered (reactivated) after stopping the admission. (6) Our new method of monitoring e(-) was very convenient and useful for studying the thermal decomposition of saline hydrides.