| Lead assay method is an important tool used for enriching precious metal. Lead assay method has been found wider application due to the development of instrumental analysis technique. However, the presence of some elements can interfere the process of lead assay, resulting in lower gold test result. In this work, the interference elements were expounded, and the commonly used methods for eliminating interference were summarized. Moreover, The interference level of the elements and the interference removal method were also explored.The traditional roasting method was modified in order to eliminate the interference caused by sulfur, arsenic and selenium etc. Compared to the traditional method, the modified method is able to solve the problem of lower test result caused by cacking and loss of Au. In addition, the modified method possess some advantages over niter method, such as removal of reducing capacity test and simpler operation. Compared to wet-pyrogenic method, the procedure of the modified method was shorten by a large margin. The modified method have higher roasting efficiency than direct roasting method in the process of sulfur removal. Investigation suggested that the optimum roasting time of 1.5h and the temperature of 600℃ were the best conditions on the sulfur removal result and cost. The results from modified roasting method, direct roasting method and niter method were compared, which indicate that the modified roasting method with the RSD below 3.5% possess higher accuracy and precision. The modified method was used to measure the content of Au in the sample with high arsenopyrite, and the result is satisfying.The effects of Cu, Sb, Ni and Sn were also investigated. The cupellation process containing Cu was analyzed in detail, and the mechanism of Au loss caused by Cu was presented: the cupric oxide and the lead oxide formed a mutually soluble body during the process of the cupellation, the surface of the mutually soluble body had the highest content of cupic oxide and was absorbed firstly; Some gold was dissolved in it and absorbed together.The previous conclusion that obvious influence on the recovery of Au was observed when lead button contains 2.5g of Cu was enriched: In a lead button of about 25 g, Cu below 1.5g doesn’t cause obvious influence; the higher content of Au between 0.6mg and 6mg and the lower content of Cu, the higher percent recovery could be got when the Cu was between 1.5g and 2.5g. Another previous conclusion that the addition of 30 folds of lead oxide can eliminate the influence of Cu was demonstrated: investigation suggested that the addition of 30 folds of lead oxide could made a lead button with about 1.25 g of Cu, which wouldn’t cause obvious influence according to the cupellation test.The critical content of Cu, Sb, Ni and Sn influencing the recovery of Au were determined. Also the required lead oxide added into the smelting process for removing interference was determined. The phenomenon and features of cupellation process under the presence of Cu, Sb, Ni and Sn was summarized and compared with each other. That would be significative in analytical work.
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