铁(Ⅱ)-铈(Ⅳ)双中间体库仑法测铬(Ⅵ)

DETERMINATION OF CHROMIUM(Ⅵ)BY DUAL-INTERMEDIATE[Fe(Ⅱ)-Ce(Ⅳ)]COULOMETRIC METHOD

本文研究了 Fe(Ⅱ)-Ce(Ⅳ)双中间体库仑法测定水体及废水中微量 Cr(Ⅵ)的条件。方法是在3.5M H_2SO_4,0.015M Fe_2(SO_4)_3和4mg/mlCe_2(SO_4)_3混合液中,并有少量 Ag^+离子存在下,以铂片为发生电极,铂丝为辅助电极电生 Fe(Ⅱ)定量还原样液中的 Cr(Ⅵ),过量的 Fe(Ⅱ)以电生 Ce(Ⅳ)回滴。铂片为指示电极,钨丝为参比电极,平衡电位法指示终点。在大气下不用通氮除氧,测定0.5和5.0μgCr(Ⅵ),相对误差分别小于10%和1%,标准偏差分别为0.02和0.07。43种干扰物质试验表明,除 S~=,VO_3^-等少数物质干扰测定外,其余均不影响。该法简便快速,并能在同一电解液中连续测定多次。已将此法用于多个水样中 Cr(Ⅵ)的测定并与二苯碳酰肼比色法对照,结果基本一致。

A method of determinating of Cr(Ⅵ)using dual-intermediate coulom- etric method has been presented in this paper.This process may be carried out under atmosphere without passing N_2.The base electrolytic solution is a mixture of 3.5M H_2SO_4,0.015M Fe_2(SO_4)_3 and 4mg/ml Ce_2(SO_4)_3.A small amount of silver salt is added,which will depress the interference of the dissolved oxygen.Compared with the dipbenyl carbazide colorimetric method,the relative errors of the measuring of 0.5μg and 5.08 Cr(Ⅵ) are less than 10% and 1% respectivily.The standard deviation are 0.02 and 0.07 respectivily. The interference of 43 ions has heen tested,the results are satisfied, except S^(2-),VO_s ions. This method is easily manipulated,fast,and the sample may be added in continously.