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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/cm~2,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 NH_4Cl-NH_4OH
We note that manganese (II), in the ammoniacal medium at pH 9.3-10.0, rapidly converts blue chrome black T to a yellow product under heating. The absorbance of the reagent blank was measured with the addition of different amounts of manganese (II) at the maximum absorbance peak of the reagent blank at λ = 611 nm. The absorbance of the blank was determined in the range of 0-0.25 μg Mn (Ⅱ) / 25 ml Law, its Sandell sensitivity of 1.07 × 10 (-5) μg / cm ~ 2, is more than 2,500 times the potassium permanganate method, has become the highest sensitivity of the spectrophotometric method for the determination of manganese. (A) of the instrument and the main reagents 721 and 751 spectrophotometer. Chrome black T, 0.1% aqueous solution. Distilled water must be put for a few days. Manganese standard solution, the standard solution containing manganese (Ⅱ) 1mg / lml diluted to 0.05μg / ml. (B) Experimental Method Take 0.2μg manganese (Ⅱ) in a 25ml volumetric flask, followed by adding 4.0ml chrome black T solution, 3.0ml NH_4Cl-NH_4OH