In the penetration test for deep penetration treatment wood which is treated with AZE containing triazole fungicide, synthetic pyrethroid insecticide, and zinc soap as a tracer, 0.1% of 1,5-diphenylthiocarbazone （dithizone） solution which forms red complexes with zinc ions is used as an indicator to recognize the penetrated region. However, after two weeks following the treatment, it is often difficult to distinguish red（i.e. the penetrated region） from dark green （i.e. the unpenetrated region）, as aging progresses. In this study, the authors aimed to improve the method for determination of the penetrated region of AZE. X-ray fluorescent analyses indicated that zinc complex also exists in such unclear regions. Furthermore, the authors observed that a high concentration of dithizone masks the red color of zinc complexes in solution systems. As a result of tests using dithizone solution with different concentrations, it was demonstrated that adjustment of its concentration at between 0.02% and 0.05% makes it possible to distinguish the penetrated region clearly. In addition to such method, the authors found that the precipitation technique with water is usable in the coloring test as a novel method, in the case of application of 0.1% concentration dithizone, in which color determination is otherwise difficult. Consequently, the penetration test for AZE containing zinc soap as a tracer was improved with greater precision.

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