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

A method for the determination of trace chloride in sulphide ores by potentiometric titration was developed. S2-was oxidized to S6+by roasting the samples mixed with zinc oxidesodium carbonate in order to eliminate the interference from Ag2S precipitation on AgCl 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 ΔE/ΔV-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.