【摘要】 <正> 我们注意到:在pH=9.3-10.0的氨性介质中,锰（Ⅱ）在加热条件下会使兰色的铬黑T很快地转变成黄色的产物。在试剂空白的最大吸收峰λ=611nm处,以加入不同量锰（Ⅱ）的试样为参比,来测定试剂空白的吸光度,在0-0.25μg Mn （Ⅱ）/25ml的范围内遵从Beer定律,其Sandell灵敏度达1.07×10（-5）μg/cm²,是高锰酸钾法的2500余倍,成为目前测定锰灵敏度最高的光度法。 （一）仪器及主要试剂 721型及751型分光光度计。铬黑T,0.1％水溶液。蒸馏水,须陈放数日。锰标准液,把含锰（Ⅱ）1mg/lml的标准液稀释至0.05μg/ml。 （二）实验方法取0.2μg锰（Ⅱ）于25ml容量瓶中,依次加入4.0ml铬黑T溶液,3.0ml NH₄Cl-NH₄OH更多还原

【Abstract】 A new and very sensitive method has been developed for the spectrophotometric determination of trace Mn. It is based on the decreasing in the absorbance of eriochrome black T with Mn(Ⅱ)on heating in the pH range of 9.3—10. 0 at 611 nm. Beer＇s law is obeyed in the range of 0—0.25μg Mn(Ⅱ) /25ml and Sandell＇s sensitivity is 1.07×10~-5 μg/cm~2. The method has been used to determine trace amounts of Mn(Ⅱ)in natural water and small amounts in iron after suitable separation with satisfactory results.更多还原