基体分离-电位滴定法测定高硫金属矿中的微量氯

Determination of Micro-amount of Chloride in Hing Sulfur-Metallic Ores by Matrix Separation-Potentiometric Titration

使用碳酸钠-氧化锌混合碱焙烧样品，将硫化物矿中的低价硫转化为硫酸盐或高价硫，过滤分离基体，采用电位滴定法测定硫化物矿（铜精矿、锌精矿、硫铁矿）中的微量氯，消除由于硫化银沉淀的产生对氯化银测定结果的干扰。通过电位突越，确定滴定终点，消除色度和浊度对滴定终点的影响。采用电极电位-浓度二次微商滴定曲线，计算滴定终点。对混合碱的选择及加入量、焙烧温度、溶液酸度、测定温度、滴定介质以及基体和共存元素的干扰进行了试验。方法精密度（RSD，n=9）均小于9％，回收率为94．1％～105．6％。

A method for the determination of trace chloride in sulphide ores by potentiometric titration was developed. S^2- was oxidized to S^6＋ by wasting the samples mixed with zinc oxide-sodium carbonate in order to eliminate the interference from Ag2 S precipitation on AgC1 measurement. The influence from chromaticity and turbidity on the end point of titration was eliminated by confirming the end point of titration with the potential jump and using the second derivative potentiometric titration curve to calculate the titration end-point, which can avoid the problem from drawing the E-V curve or the △E/△V-V curve. Some important measurement parameters such as selection of mixed alkali and its dosage, roasting temperature, solution acidity, titration medium and the effects of sample matrix and coexisting elements on the measurements were studied. The recovery of the method was in the range of 94.1% - 105.6% with precision of better than 6.83%RSD, 8.70%RSD and 7.53%RSD for iron ores, copper concentrates and zinc concentrates respectively. The method was sensitive, accurate and simple. And good results were achieved for the analysis of trace chloride in sulPhide ores.