碱熔-蒸馏-滴定法测定萤石中的氟化钙含量

采用碱熔-蒸馏-滴定法测萤石中氟含量,计算得到氟化钙含量。萤石试样首先用碳酸钠碱熔消解,然后经硫酸-水蒸气蒸馏分离氟,以茜素磺酸钠作指示剂,用硝酸钍溶液滴定测出其中氟含量,并计算得到氟化钙含量。利用X射线衍射光谱(XRD)法验证了萤石中氟的存在形式,并通过实验确定了碳酸钠使用量、硫酸溶液加入量、蒸馏温度和蒸馏时间等的最佳实验条件。采用国家标准样品对方法进行了准确度和精密度验证,几个标准样品的碱熔-蒸馏-滴定法结果均在标准值允许误差范围内,相对标准偏差(RSD)均小于0.5%,方法准确可靠,值得推广。

Determination of CaF2 content in Fluorspar by Alkaline Fusion-Distillation-Titration Method

In this paper, the content of fluorine in fluorspar was determined by alkaline fusion-distillation-titration method, and the content of CaF2 was calculated. The fluorspar sample is first dissolved by sodium carbonate, then separated by sulfuric acid steam distillation. The fluoride content is determined by titration of thorium nitrate solution with sodium alizarin sulfonate as indicator, then CaF2 calculated. The fluorine form in fluorspar was determined by XRD, and through the test of the using amount of sodium carbonate and sulfuric acid solution, the distillation temperature and time differences, the suitable experimental conditions were determined. The accuracy and precision of this method were also verified by using national standard samples. The RSD of alkaline fusion-distillation-titration method of all samples are less than 0.5%, indicating the method is accurate and reliable, which is worth promoting.