酸碱滴定法间接测定重晶石中的硫酸钡

<title>Indirect determination of barium sulfate in barite by acid-base titration

利用偏磷酸与重晶石在400℃时的复分解反应,将硫酸钡转化为聚偏磷酸钡,同时生成的H2SO4在高温下可挥发除去。在强碱性溶液和过氧化氢的作用下,聚偏磷酸钡转化为有确定磷钡比的磷酸钡。将磷酸钡用盐酸溶解后,在CaCl2存在下,以甲基红和酚酞为指示剂,用氢氧化钠标准溶液滴定磷酸,以间接测定重晶石中硫酸钡的含量。本法所需时间6h,分析结果与标准方法(SN/T0480.5 95)吻合,RSD为0.33%～0.68%。

<Abstrcat>Barium sulfate was transfered to barium polymetaphosphate and H2SO4(g) by double decomposition reaction between metaphosphoric acid and barite at 400 ℃. The barium polymetaphosphate was depolymerized by hydrogen peroxide in alkaline solution to barium phosphate which had definite chemical composition. The barium phosphate was dissolved in hydrochloric acid to yield phosphoric acid and barium(Ⅱ) which could be precipitated by adding sulfate. Second and third protons of the phosphoric acid were titrated by NaOH in the presence of CaCl2. The whole analysis process took only 6 h. The determination results obtained by this method were consistent well with those obtained by the standard method (SN/T0480.595). The relative standard deviations were 0.3%～0.68 %.