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

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.