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硫酸高铈或硫酸高铈铵标准溶液的标定,通常以草酸钠为基准物,利用铈(Ⅳ)本身具有的黄色指示滴定终点的方法,因其颜色变化不够敏锐而影响终点的判断,本文采用邻菲咯啉-亚铁指示剂,使溶液颜色由桔红色变成浅蓝色为终点,变化敏锐,提高了方法的精密度和准确度。为确保终点变化敏锐,至少需加2滴指示剂,滴定时溶液的适宜温度范围为5—55℃;本指示剂属环元形,要消耗硫酸高铈或硫酸高铈铵标准溶液,故在标定时须做相应的试剂空白以校正其浓度。主要试剂邻菲咯啉-亚铁指示剂:称取0.695gFeSO_4·7H_2O于小烧杯中。加入30mL pH2—3硫酸酸性溶液溶解。再称入1.5g邻菲咯啉,待完全溶解后移入100mL容量瓶中,以pH 2—3硫酸酸性溶液定
Cerium sulfate or ceric ammonium sulfate standard solution calibration, usually sodium oxalate as the base, the use of cerium (IV) itself has the yellow end point of the method of titration, because of its color change is not sensitive enough to determine the end point, this article uses Phenanthroline - ferrous iron indicator, the color of the solution from orange to light blue as the end point, sharp changes, improve the precision and accuracy of the method. In order to ensure sharp changes in the end point, at least 2 drops of indicator should be added, the titration solution temperature is appropriate for the 5-55 ℃; This indicator is a ring element, to consume ceric sulfate or ceric sulfate ammonium standard solution, so in Calibration should be done when the reagent blank to correct its concentration. The main reagent o-phenanthroline - ferrous indicator: Weigh 0.695gFeSO_4 · 7H_2O in a small beaker. Add 30mL pH2-3 sulfuric acid solution dissolved. Then weighed 1.5g o-phenanthroline, to be completely dissolved into 100mL volumetric flask to pH 2-3 sulfuric acid solution