铌的极谱催化波——Ⅲ.铌（Ⅴ）—氯酸钾—杏仁酸体系

铌的极谱催化波——Ⅲ.铌（Ⅴ）—氯酸钾—杏仁酸体系 STUDIES OF POLAROGRAPHIC GATALTTIG WAVES OF NIOBIUM Ⅲ. THE SYSTEM OF NIOBIUM（V）-POTASSIUM CHLORATE-AMYGDALIC ACID 佘培柱 first-author 焦根基 周性尧 曾云鹗 在弱酸性的杏仁酸底液中,铌（Ⅴ）能在滴汞电极上还原,产生一个极谱波;当有氯酸钾存在时,则在还原波上出现峯现象,并有催化电流产生,可用于测定濃度低至1×10 -9 M的铌。于0.08M杏仁酸、0.55M氯酸钾、0.05M四甲基溴化铵及pH2.2的最宜条件下,铌（Ⅴ）濃度在1×10 -8 —1×10 -6 M区间,峯电流与铌濃度成直线关系;而当实验条件为0.08M杏仁酸、0.55M氯酸钾、0.05M四甲基溴化铵及pH3时,则可测定1×10 -9 —1×10 -8 M濃度的铌g（Ⅴ）、铁（Ⅲ）及少量的钨（Ⅵ）、钼（Ⅵ）、钛（Ⅳ）、锆、铀（Ⅵ）和釷等离子存在时,不干扰铌的测定。经催化电流的性质分析及机理研究,证明畸峯现象的产生系铌（Ⅴ）—杏仁酸的络阴离子还原时,在滴汞电极上的吸附所致;在氯酸钾存在下,则还原产物铌（Ⅳ）被其氧化而再生五价铌,产生催化电流。故催化电流且有吸附性质。本法可用于纯钽中痕量铌的测定。 In a medium of weak acidic amygdalic acid, niobium（Ⅴ） can be reduced at dropping mercury cathode and then a polarographic wave is observed. When chlorate is present, a maxima is occurred and catalytic wave takes place. Surface-activesubstances effect an increase in the catalytic current.For analytical purposes an electrolyte of the following composition is recommended: 0.08M amygdalic acid, 0.55M potassium chlorate, 0.05M tetramethylammonium bromide and pH 2.2, then a linear relation exists between the peak currents and the concentrations of niobium (1×10 -8 -1×10 -6 M). In solutions of 0.08M amygdalic acid, 0.55M potassium chlorate, 0.05M tetramethylammonium bromide and pH 3, niobium can be determined in the concentration range from 1×10 -9 M to 1×10 -8 M. No interference from tantalum（Ⅴ）, iron（Ⅲ） and small amounts of tungsten（Ⅵ）, molybdenum（Ⅵ）,titanium（Ⅳ）, zirconium, uranium（Ⅵ） and thorium ions can be detected.The nature of the catalytic wave has been investigated. The mechanism of maxima is caused by the absorption of electroreduction of niobium（Ⅴ）-amygdalic acid complex anion on the surface of dropping mercury electrode and the catalytic current produced is due to the reduction of chlorate catalyzed by the amygdalic acid complex of niobium.This method has been applied to the determination of trace amounts of niobium in pure tantalum. 1965-01-01 2021-04-01 Z1