Automatic Potentiometric Titration of Water Soluble Chlorides in Iron Ores

Water soluble chlorides in iron ores were determined by automatic potentiometric titration in weakly acidic solution of pH>2 and containing ethanol and water in the ratio of 4 to 1,using 0.002 mol·L-1 AgNO3 standard solution as titrant.Soluble chlorides in the sample were extracted with water at 95 ℃.Interference of sulfides was eliminated by boiling the slightly alkalified sample solution with H2O2 until ceasing of gaseous bubbles.Methods of pretreatment of sample,and various parameters affecting the titration (i.e.titration medium,acidity and temperature of the titrate,as well as the rate of stirring and titration) were tested and optimized.Detection limit of the method was found to be 2.0 μg.Recovery test was performed by standard addition method,and the results obtained were in the range of 99.9%-100.4%.