The Practice of Iron Determination in By-Products with a High Copper Content Using Redox Titration: Waelz Slag Case Study

The classical methods of determining total iron are widely used in laboratory practice. The most common technique is redox titration. The approach standardized in ISO 2597-1 (GOST 32517) provides for digestion of the sample to dissolve it, reduction of Fe³⁺ using SnCl₂ to Fe²⁺, and its titration with K₂Cr₂O₇ in the presence of an indicator—sodium or barium diphenylamine sulfonate. We propose an approach to determine the total iron content through titration using potassium tetrahydride borate as a reducing agent instead of SnCl₂. The parameters of the known and suggested methods are investigated using sintering to decompose samples when a large number of samples is analyzed. The developed method to analyze standard samples and real industrial materials with a high copper content taking the Waelz slag as an example has a satisfactory accuracy and reproducibility of the values obtained for the total iron content. The results indicate the potential of applying this technique to measure iron content in samples rich in copper without the copper reduction step. As a result, the performance of the method has been improved: the technique can be carried out at room temperature, there is no need to control the amount of reducing agent added, and to titrate the solution immediately after iron reduction. These advantages, along with no need to use toxic mercury compounds, make this method promising to analyze a large number of samples.