As an evaluation of durability of synthetic silica glass under irradiation of KrF excimer laser (5.0 eV) or ArF excimer laser (6.4 eV), degradation of transmission was studied for a sample that contained 4×10¹⁸ molecules/cm³ H₂ but was substantially free of other impurities. First, Khotimchenko’s method of H₂ analysis was examined with specimens whose H₂ contents were varied by vacuum degassing, covering three orders of magnitude down to H₂-free (i.e., less than the instrumental detection limit of 5×10¹⁶). It was shown that this method was quite reliable.
Then the effects of dissolved H₂ were assessed. The hydrogen molecules were decomposed under excimer laser irradiation, and reacted with the E’ center. For KrF excimer laser irradiation, the degradation of transmission was found to be suppressed, when the concentration of hydrogen much increased. Whereas for ArF excimer laser irradiation, there seemed to exist an optimum concentration range.
The author proposes a reaction model for the last observation as:
≡ Si–O–Si ≡+ H₂+hν→≡Si·+·O–Si≡+ H₂→≡+Si–H + H–O–Si ≡,
where ≡Si· is the E’ center, and ·O–Si≡ , the non-bxsridging oxygen hole center.

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Sillenite from Fuka occurs as cubes up to 5 mm across in a calcite vein cutting gehlenite-spurrite skarn, probably as a primary mineral in a new mode of occurrence to this mineral as well as the first description of its idiomorph. The wet and microprobe analyses gave SiO₂ 2.22, 1.85; Bi₂O₃ 97.74, 96.48; totals 99.96%, 98.33%, respectively. The average yields the empirical formula Bi_24.06Si_1.95O₄₀ (basis O = 40), proving the validity of the ideal formulaBi₂₄Si₂O₄₀ advocated after the reference to many synthetic works on Bi₂₄X₂O_39–40 where X = Fe, Al, Ge, Ti, P, As, and V. The single crystal and X-ray powder works verify the symmetry to be cubic, space group I23, a=10.110(2)Å, Z = 1. It is optically isotropic, refractive index >2.50; VHN₅₀=345∼386 kg/mm², density 9.16 g/cm³ (meas.), 9.18 g/cm³ (calc.).

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The grinding of synthetic rhabdophane type RPO₄·nH₂O (R = La, Ce, Pr, Nd or Sm; n∼1/2) for 5 days at 20°C converted them into their monazite type anhydrous analogue, respectively.

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