酸碱中和滴定法测定萤石中碳酸盐量

Determining the content of carbonate in fluorite by neutralization titration method

本方法在气体发生装置中用盐酸处理试料,Ba(OH)2溶液吸收产生的CO2,过量的碱用盐酸中和,加一定体积过量的盐酸标准滴定溶液以溶解BaCO3沉淀,再以甲基橙为指示剂,用NaOH标准滴定溶液返滴定测量碳酸盐量。通过进行氮气流量、氟离子干扰、硫离子干扰、盐酸对测量的干扰、BaCl2用量、标准物质回收等试验,确定最佳分析条件。该方法可直接反映萤石样品中碳酸盐的量,测量精度较好,可用于日常分析。

A new method for determining the content of carbonate in fluorite samples, named neutralization titration method has been studied. In this method the fluorite samples are firstly dealt with the hydrochloric acid in a gas generator. The product, carbon dioxide, is absorbed by barium hydroxide solution, and the excessive barium hydroxide is neutralized by hydrochloric acid with a phenolphthalein indicator. Subsequently, a certain volume of standard hydrochloric acid solution is used to dissolve the barium carbonate sediment. Finally, the excessive hydrochloric acid is titrated by the standard sodium hydroxide solution with a methyl orange indicator. The content of carbonate can be calculated according to the volumes of the standard sodium hydroxide solution and standard hydrochloric acid solution. In this paper, the analysis conditions including the nitrogen flow rate, interference of fluoride ion, sulfur ion and hydrochloric acid, the amount of barium chloride and the recovery ratio, are also discussed carefully. Our result indicates that this method can directly get the content of carbonate in fluorite samples with good accuracy, so it can be applied to the daily analysis.