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本文研究了半二甲酚橙(SXO)与铁(Ⅲ)的显色反应。在0.03-0.09mol/L的盐酸介质中显色,铁(Ⅲ)与SXO形成1∶2的稳定络合物,其最大吸收峰位于545-550nm,摩尔吸光系数为3.98×10~4,铁量在0-30μg/mL服从比尔定律,络合物5min内能显色完全,并且至少稳定20h。方法已用于金属锌、镁、氧化镁及硅石等试样中微量铁的测定。常见离子及化合物的影响:在试验条件下允许存在下列离子(以mg计):Mg(Ⅱ)、Zn(Ⅱ)(25);Pb(Ⅱ)、Cd(Ⅱ)(5);Cr(Ⅲ)(1);Ca(Ⅱ)(0.5);Pt(Ⅱ)、Sn(Ⅳ)、∑RE、W(Ⅵ)(0.1);As(Ⅴ)、Hg(Ⅱ)、Sb(Ⅴ)、Ti(Ⅳ)(0.05);Be(Ⅱ)(0.025);
In this paper, the color reaction of hemi-xylenol orange (SXO) with iron (Ⅲ) was studied. The complex of iron (Ⅲ) with SXO formed a stable complex with the maximum absorption at 545-550nm, the molar extinction coefficient of 3.98 × 10 ~ 4 and the iron Beer’s law was obeyed in the range of 0-30μg / mL. The complex developed completely within 5 minutes and was stable for at least 20 hours. The method has been applied to the determination of trace iron in the samples of zinc, magnesium, magnesia and silica. Effects of Common Ions and Compounds: The following ions (in mg) are allowed to exist under the experimental conditions: Mg (II), Zn (II) (25); Pb (1), Ca (Ⅱ) (0.5), Pt (Ⅱ), Sn (Ⅳ), ΣRE, W (Ⅵ) (0.1) (Ⅳ) (0.05); Be (Ⅱ) (0.025);