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基于甲醛法无法准确测定氟化氢铵产品中氟化铵杂质的缺点,用双指示剂法对甲醛法进行改进。先以中性红-溴百里酚蓝为指示剂滴定溶液氟化氢铵的含量,再用酚酞为指示剂甲醛法测溶液中总NH4+量从而得出氟化铵含量,由此可实现氟化氢铵及其中氟化铵含量的分别测定。该方法操作简单,准确度高,加标回收率为99.7%~101.0%,最大相对偏差在±2.0%左右,具有较高的实用性。
Based on the formaldehyde method can not accurately measure the ammonium fluoride ammonium fluoride impurities shortcomings, with double indicator method formaldehyde method to be improved. First with neutral red - bromothymol blue as the indicator titration solution ammonium bifluoride content, and then using phenolphthalein as indicator formaldehyde method to measure the total amount of NH4 + in the solution to obtain the ammonium fluoride content, which can achieve ammonium bifluoride and One of the ammonium fluoride content were determined. The method has the advantages of simple operation, high accuracy, recoveries of spiked standards of 99.7% -101.0% and maximum relative deviation of about ± 2.0%, which has high practicability.