不同基准物质及标准滴定溶液标定亚铁时对测定钒含量的影响

Effect of various reference materials and standard titration solution on the determination of vanadium content during the calibration of ferrous

氧化还原滴定法是钒检测的常用方法,即以N-苯基邻氨基苯甲酸为指示剂,采用硫酸亚铁铵标准溶液(亚铁)滴定钒含量。在国家标准和行业标准中,亚铁的标定主要采用光谱纯五氧化二钒、偏钒酸铵、重铬酸钾和高锰酸钾等基准物质或标准溶液。实验基于亚铁标定的差异性研究,探索其对钒含量检测结果的影响。试验发现,当采用偏钒酸铵或五氧化二钒作为标准物质时,溶液的标定和钒化合物的钒含量检测过程,具有相同的化学反应,指示剂变色电位与化学计量电位差引入的误差将会被部分抵消而降低。相对于偏钒酸铵(或五氧化二钒),高锰酸钾和重铬酸钾标准溶液标定亚铁的结果偏低,这将导致钒的检测结果偏低。

The redox titration was the common method for the determination of vanadium,in which,N-phenyl-o-aminobenzoic acid was used as indicator,and the content of vanadium was titrated using ammonium ferrous sulfate（FAS） standard solution.In national standard and industrial standard,ferrous was calibrated mainly with reference materials or standard solutions such as spectroscopically pure vanadium pentoxide,ammonium meta-vanadate,potassium dichromate and potassium permanganate.Based on the difference study of FAS calibration,its influence on the determination of vanadium was investigated.It was found that,when ammonium meta-vanadate or vanadium pentoxide was used as reference material,the calibration of solution and the determination of vanadium content in vanadium compounds had the same chemical reaction.The error caused by the color change potential of indicator and the difference of stoichiometric potential would be partially offset and decreased.Compared with ammonium meta-vanadate （or vanadium pentoxide）,the calibration results of FAS were lower when potassium permanganate and potassium dichromate were used,so the determination results of vanadium were also lower.