Indirect determination of chlorine in zinc oxide dust by flame atomic absorption spectrometry

The sample was dissolved in diluted nitric acid. Then, excessive Ag⁺ standard solution was added into the sample solution. Trace Cl^- in sample solution would quantitatively reacted with Ag⁺ to form silver chloride colloid. The solution was heated and boiled to agglutinate rapidly and completely precipitate silver chloride colloid. The residual Ag⁺ content in filtrate was determined by flame atomic absorption spectrometry. Then, the content of chlorine in zinc oxide dust could be indirectly obtained. The interference of coexisting ions, the dissolution conditions of sample, the reaction time of precipitation and determination medium were discussed to obtain the optimal experimental conditions. The proposed method was applied to the determination of chlorine content in zinc oxide dust of fuming furnace and rotary kiln. The results were basically consistent with those obtained by silver chloride turbidimetry. The relative standard deviations (RSD, n=5) were 0.65%-0.89%. The recoveries were between 99% and 101%.