水蒸汽蒸馏-EDTA滴定法测定氟化镝中氟

Determination of fluorine in dysprosium fluoride by steam distillation-EDTA titrimetry

探讨了水蒸汽蒸馏分离-富集氟的条件,建立了EDTA滴定法测定氟化镝中氟量的方法。试样经高氯酸分解后,在140～170℃的温度下进行水蒸汽蒸馏,溶液中的氟富集于馏分中,在较低的pH值条件下煮沸馏分使氟离子与过量的氯化镧充分反应,待溶液冷却后,以二甲酚橙为指示剂,六次甲基四胺-盐酸为缓冲溶液,用EDTA标准溶液滴定溶液中剩余镧离子,计算得出氟量。干扰试验证明,样品中的稀土、铁、钙、铝、硅等干扰元素可有效与氟分离,对实验结果无影响。方法用于氟化镝中氟量的测定,结果的相对标准偏差(RSD,n=10)为0.48%。对氟化镝实际样品进行分析,结果同碱熔融-EDTA滴定法一致。

The separation-enrichment conditions of steam distillation were studied to establish a determination method of fluorine in dysprosium fluoride by EDTA titrimetry.The sample was decomposed by perchloric acid.Then,the solution was distilled by steam at 140-170 ℃.The fluorine in solution could be enriched in the fraction.Under low pH,the fraction was boiled to realize complete reaction between fluoride and excessive lanthanum chloride.After cooling,the residual lanthanum ions in solution were titrated by EDTA standard solution in hexamethylenetetramine-hydrochloric acid buffer solution with xylenol orange as indictor.Then,the content of fluorine could be calculated.The interference test indicated that,the interference elements（such as rare earths,iron,calcium,aluminum and silicon）in sample could be effectively separated from fluorine and had no influence on the experimental results.The proposed method was applied to the determination of fluorine in dysprosium fluoride.The relative standard deviation（RSD,n=10）of determination results was 0.48%.Actual dysprosium fluoride sample was analyzed,and the results were consistent with those obtained by alkali fusion-EDTA titrimetry.