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利用铋碘络阴离子与碱性染料阳离子形成的离子缔合物,萃取光度法测定铋已有报导。但它们均不能在水相中直接显色测定,常需用有毒的苯等有机溶剂萃取,不仅增加了手续,而且灵敏度也不够高,摩尔吸光系数约在4.3×10~4～6.5×10~4之间。本文研究在高浓度的碘化钾存在下的微酸性介质中,铋所形成的〔BiI_5〕~(2-)络阴离子,在与罗丹明B等碱性染料阳离子形成离子缔合物时,当有聚乙烯醇等保护胶体存在下,不产生沉淀,并可观察到溶液颜色发生明显变化,借此可直接在水相中测定铋。方法简便,并具有很高的灵敏度。
The use of ion-association complexes of bismuth iodide anions with basic dye cations to determine bismuth by extraction spectrophotometry has been reported. However, neither of them can be directly measured in aqueous phase, and often need to be extracted with toxic benzene and other organic solvents. Not only the procedures but also the high sensitivity are not obtained. The molar absorptivity is about 4.3 × 10 ~ 4 ~ 6.5 × 10 ~ 4 between. In this paper, the formation of [BiI_5] ~ (2-) complex anions formed by bismuth in a slightly acidic medium in the presence of high concentrations of potassium iodide, when forming an ionic complex with a basic dye cation such as rhodamine B, In the presence of protective colloids such as vinyl alcohol, no precipitation is observed and significant changes in the color of the solution can be observed, whereby bismuth can be measured directly in the aqueous phase. The method is simple and has high sensitivity.