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在聚乙烯醇存在下,W(V)-SCN-孔雀绿(MG)体系在水相有灵敏的显色反应,最大吸收波长在640 nm。摩尔吸光系数为3.5×10~5,0—25μg钨/50mL符合比尔定律,络合物在两小时以内稳定。用摩尔比法和连续变化法测得W:MG=1:4,其可能结构为[WO(SCN)_5]~(2-)·2MG~(+)·2(SCN~7·MG~+)。生成复杂离子缔合物增溶于聚乙烯醇胶束是增敏作用的根本原因。已用于某些矿石和钢铁中钨的测定。对于10μg钨、100mg柠檬酸;50mg草酸、乳酸;10mg钙(Ⅱ)、镁(Ⅱ);5 mg硅(Ⅳ)、硼(Ⅲ);2mg铁(Ⅲ);1mg锰(Ⅱ),铝(Ⅲ)、铬(Ⅲ);0.5 mg铅(Ⅱ)、镉(Ⅱ)、镍(Ⅱ)、铋(Ⅲ)、锑(Ⅴ)、铈(Ⅳ);0.2mg钴(Ⅱ)、铌(Ⅴ),砷(Ⅲ);0.1mg镧(Ⅲ);50μg钒(Ⅴ)、钛(Ⅳ),锆(Ⅳ);20μg银(Ⅰ)、金(Ⅲ)、镓(Ⅲ)、铟(Ⅲ);15μg汞(Ⅱ)锡(Ⅳ);10μg锌(Ⅱ)、钼(Ⅵ)不产生干扰。
The W (V) -SCN-malachite green (MG) system has a sensitive color reaction in the aqueous phase in the presence of polyvinyl alcohol with a maximum absorption wavelength of 640 nm. The molar extinction coefficient of 3.5 × 10 ~ 5,0-25μg tungsten / 50mL Beer’s law, the complex within two hours of stability. The molar ratio and the continuous change method were used to determine the molar ratio of W: MG = 1: 4, which could be expressed as [WO (SCN) 5] ~ (2-) · 2MG ~ (+) · 2 ). The formation of complex ion association solubilization in polyvinyl alcohol micelles is the root cause of sensitization. It has been used for the determination of tungsten in some ores and steel. 100 mg of citric acid, 50 mg of oxalic acid, lactic acid, 10 mg of calcium (II), magnesium (II), 5 mg of silicon (IV), boron (Ⅲ), chromium (Ⅲ), 0.5 mg lead, cadmium, nickel, bismuth, antimony and cerium, 0.2 mg cobalt, ), Arsenic (III), 0.1 mg of lanthanum (III), 50 μg of vanadium (V), titanium (IV) and zirconium (IV) ; 15μg mercury (Ⅱ) tin (Ⅳ); 10μg zinc (Ⅱ), molybdenum (Ⅵ) did not interfere.