Accurate Determination of Total Iron in Ores by Automatic Potentiometric Titration without Potassium Dichromate

For iron ores, this paper discusses an alkali fusion method of sodium peroxide to resolve the ores without splash and complete decomposition. Four methods of reducing Fe³⁺ to Fe²⁺ are also discussed, using stannous chloride and titanium trichloride as this not only avoids the use of toxic reagents, but also has a clearly potential jump at the end of the titration. Finally, the manual titration method is replaced by an automatic potentiometric titration to avoid manual errors, such as the judgement of the end of titration by colour and the level of experience of the analyst. The relative error can be reduced to 0.13% and the relative standard deviation is 0.22%. A new SnCl₂-TiCl₃-K₂Cr₂O₇ automatic potentiometric titration method has been developed. It has been applied to detect six National Standard Reference iron ore samples where the content of iron is higher than 30% and the relative error is lower than 0.2%, the relative standard deviation being lower than 0.3% (n=10). The magnetite GBW 07226a and GBW 07224 with high vanadium and titanium can be determined directly in one step. This new method is suitable to determine iron ores especially high content iron ores which require higher accuracy and is simple and fast to perform.