Abstract：The lead fire assaying gravimetry is an old and classical method. It is one of most commonly used and most effective methods for the separation and analysis of precious metals due to strong representativeness, high accuracy and good stability. However, the lead fire assaying gravimetry also has some disadvantages such as long analytical procedure and systemic lower analytical results (especially for silver). If the second or secondary assaying is used (e.g., national and industrial standard), the analytical procedure will be longer and the operation cost will be higher. The fundamental principles in lead fire assaying analysis (such as slagging enrichment and lead-removal refining) were explored and analyzed. When the smelting and cupellation conditions were well controlled, the mathematic model for correction of silver loss amount in smelting and cupellation process was theoretically established according to the silver content in composite granule and the mass of lead button in first assaying. Thus, a determination method of silver was proposed by lead fire assay gravimetry combined with mathematic correction, which completely avoiding second assaying. The content of silver in three representative samples (including crude copper, copper concentrate and copper anode slime) was determined by the experimental method and lead fire assaying-recovery correction method. In the latter method, the lost silver in residue and cupel was determined by second fire assaying to obtain the corrected ralue of silver. The results showed that the relative difference between two methods were within ±0.5%. The relative standard deviation(RSD, n=11) with proposed method was 0.9%. In addition, the optimal lead button mass with various samples and assay ingredient schemes was obtained by higher mathematics derivation, and the lead button mass in related analysis standards was reasonably and scientifically reviewed.
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SHENG Jian-lin. Determination of silver by lead fire assaying gravimetry combined with mathmetic correction. , 2016, 36(9): 9-18.
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