This part specifies the method for the determination of ferrous oxidation content by potassium dichromate Titrimetric method. It is suitable for the determination of ferrous oxidation content in titanium concentrates (rocks and minerals), and the determination range is 20.00% to 40.00%. The sample is dissolved with muriatic acid and sodium fluoride under the condition of isolation from air, and mixed with thiophosphorus acid. With sodium dianiline sulfonate as the indicator, it is titrated with potassium dichromate standard volume to determine the oxidation ferrous content. In the analysis, approved analytical pure reagents and distillation water or water of equivalent purity shall be used, in accordance with the provisions of GB/T 6682.