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The variation of the infrared reflection spectrum of acid stain films on X‐ray shield glass has been studied as a function of leaching time in HCl. This work supports the conclusion that the major process involved in film formation on this glass is the diffusion of lead (in modifier position) out of the glass surface. It is indicated that a small portion of the lead is in the original glass network in definite coordination with oxygen. The spectra reveal that this lead is removed with considerably more difficulty than the lead in modifier positions. If it is postulated that the modifying lead ions can diffuse more readily through the skeleton network of the film when the coordinated units are present than after they are removed, it is found that the rate of stain formation should proceed initially along a straight line followed by a growth proportional to t 1/3 . This agrees with the observed rates.
Anderson et al. (Mon,) studied this question.