应用自动电位滴定法,在pH>2的微酸性乙醇-水(4+1)溶液中,用0.002 mol·L-1硝酸银标准溶液为滴定剂,测定了铁矿石样品中水溶性氯化物.试样用水在95 ℃温度条件下浸取使其水溶性氯化物溶出,共存的硫化物的干扰采用在微碱性条件下加入过氧化氢并煮沸至无小气泡产生可予以消除,对试样的预处理方法,以及各项影响测定的参数(如溶液介质,被滴定液的酸度及温度,滴定速度及搅拌速度等)做了试验并予以优化.方法的检出限(S/N=3)为2.0 μg,用标准加入法做了回收率试验,结果在99.9%~100.4%之间.

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%.