In order to understand the reaction in a continuous mercury analyzer with the dry-type reduction process, the surface of granular tin metal in a dry-type reduction process was characterized by X-ray photoelectron spectroscopy (XPS). First, the method for chlorinating the surface of tin metal was investigated. It was found that the surface of tin metal was more deeply chlorinated by impregnating with 1 mol/1 hydrochloric acid for 2 hours than by passing 600 ppm hydrochloric acid gas through the reactor for the number of same hours. Subsequently, the change on the surface of granular tin metal by impregnating with 1 mol/1 hydrochloric acid was observed in the case of passing air with mercury(II) chloride gas and moisture through the reactor. Tin (II) chloride on tin metal changed into tin (II, IV) oxide upon exposure to air or moisture. Depth profiles indicated that a tin(IV) oxide layer was formed on a tin(II) oxide layer. These results suggested that the reducibility of tin metal depended on the ratio of the chlorinated surface. As for the reaction on the surface of tin metal pre-coated with 1 mol/1 hydrochloric acid, the resulting X-ray photoelectron spectra were in good agreement with the reaction estimated from the mass balance in the actual experiment.
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