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试样以氢氧化钠分解,在柠檬酸介质中用EDTA掩蔽铅,加入过量的碘液以氧化亚铁,再以淀粉作指示剂返滴定过量的碘,由此求出亚铁氰化铅的含量。碘标准溶液可用亚铁氰化钾按操作方法标定,条件试验的结果认为:按下述测定步骤进行,即柠檬酸溶液加入50～75毫升,碘标准溶液加入量大于19毫升,加碘后静置时间在15分钟以上(25℃,温度低时须延长静置时间),可得到满意的结果。取样0.7～0.85克(±0.0002克),置于500毫升具塞磨口锥形瓶中,吹入少量水,用力摇动使样品均匀湿润,加入氢氧化钠溶液(10%)15毫升,小心加
The sample is decomposed with sodium hydroxide, lead is masked with EDTA in a citric acid medium, excess iodine is added to ferrous oxide, and excess iodine is back titrated with starch as an indicator to determine lead content. Iodine standard solution available potassium ferrocyanide by operating the method of calibration, the conditions of the test results: According to the following determination steps, namely citric acid solution was added 50 to 75 ml, iodine standard solution was added in an amount greater than 19 ml, after the static iodization Set the time in more than 15 minutes (25 ℃, the temperature is low to extend the rest time), get satisfactory results. Take a sample of 0.7-0.85 g (± 0.0002 g) in a 500 ml Erlenmeyer flask with a small amount of water and shake it vigorously to make the sample even wet. Add 15 ml of sodium hydroxide solution (10%) carefully and carefully