在HG/T 4311—2012《工业氯化铬》滴定法测定三价铬含量的基础上，通过多步氧化法，将铁铬混合物中Cr³⁺完全氧化成Cr⁶⁺，实现了较大浓度范围内 Cr³⁺含量的精确稳定测试，解决了铁离子干扰；同时，对影响测定结果准确度的主要条件（蒸馏水添加量、氢氧化钠溶液添加量和盐酸溶液添加量）进行了实验验证对比分析，优化了实验条件。测定步骤主要为：先在酸性环境中用过量的氯酸钠溶液把Fe²⁺氧化成Fe³⁺，然后加氢氧化钠溶液在碱性环境下用双氧水初步把Cr³⁺氧化成Cr⁶⁺。此时由于部分被铁络合物包裹的Cr³⁺未被氧化，所以加盐酸溶液调节到合适的pH后，使被络合物包裹的Cr³⁺完全释出，再用双氧水完全氧化成Cr⁶⁺，然后添加硫酸溶液和磷酸掩蔽铁离子，用硫酸亚铁铵标准溶液滴定。结果表明，测定的Cr³⁺含量相对标准偏差为0.12%~0.51%，加标回收率为95.0%~99.2%，且测定结果与分光光度法测定结果基本一致，满足铁铬液流电池电解液中三价铬含量的测定要求。

The determination of trivalent chromium content was based on the titration method of “HG/T 4311—2012 Industrial Chromium Chloride”.By using a multi-step oxidation method，Cr³⁺ in the iron chromium mixture was completely oxidized to Cr⁶⁺，achieving accurate and stable testing of Cr³⁺ content within a large concentration range，and solving the interference of iron ions.At the same time，the main conditions that affected the accuracy of the measurement results，including the amount of distilled water，the amount of sodium hydroxide solution and the amount of hydrochloric acid，were experimentally verified and compared，and the experimental conditions were optimized.The main measurement steps of this method were as follows：firstly，in an acidic environment，Fe²⁺ was oxidized to Fe³⁺ with an excess sodium chlorate solution，then a sodium hydroxide solution was added，and in alkaline environment，Cr³⁺ was preliminarily oxidized to Cr⁶⁺ with hydrogen peroxide.At this point，as some of the Cr³⁺ encapsulated by the iron complex was not oxidized，a hydrochloric acid solution was added to adjust to the appropriate pH value to completely release the Cr³⁺ encapsulated by the complex.Then，hydrogen peroxide was used to completely oxidize it to Cr⁶⁺.Then，sulfuric acid solution and phosphoric acid were added to mask the iron ions，and titrated with ammonium ferrous sulfate standard solution.The results showed that the relative standard deviation of Cr³⁺ determined by this method was 0.12%~0.51%，and the recovery rate of the added standard was 95.0%~99.2%.The determination results were basically consistent with those determined by spectrophotometry，meeting the requirements for the determination of trivalent chromium content in the electrolyte of iron chromium flow batteries.