Abstract：Chrome ore samples were melted by Na2O2 at 800℃,dissolved by H2SO4 and H3PO4,then oxidized by (NH4)2S2O8. Then,a method for determination of Cr2O3 in chrome ore was developed by automatic potentiometric titrimetry with (NH4)2S2O8 reduction-KMnO4 back titration. The electrodes and titration parameters were investigated,and the various factors affecting the determination of the titration end point were discussed. Finally,213 type Pt electrode was selected as indicator electrode; (NH4)2Fe(SO4)2 and KMnO4 standard solution were calibrated respectively with signal drift as 15 mV/min,the speed for adding liquid as 10 mL/min and the maximum and recognition criteria of equivalent point as 80 and 70; the sample was back titrated with signal drift as 20 mV/min,the speed for adding liquid as the maximum and recognition criteria of equivalent point as 70.The method was applied to determination of chromium ore certified reference materials GBW07201 and GBW07202. The relative standard deviations (RSD,n=10) were 0.14% and 0.09%,respectively,and the relative errors were 0.04% and 0.06% respectively compared with the certified values. The method was applied to determination of chromium oxide in actual chromium ore samples from different producing areas,and the results were consistent with those obtained by national standard method GB/T 24230-2009.
