溶融スパイス相, 鉛相間の金の分配

鉛溶錬スパイスに関する基礎的研究 (第3報)

抄録

When the intermediate products such as dust, dross and slime formed in smelting process are melted in a reduction furnace to recover lead, the speiss is often formed because of a presence ofarsenic, and it equilibrates with metallic lead phase in molten state. To clarify the behavior of speiss in the process, the distribution of gold between molten speiss and lead in Pb-Fe-As, Pb-Cu-As and Pb-Fe-Cu-As systems has been determined at 1200°C, following the preceding papers on the miscibility gap and the distribution of silver.
In Pb-Fe-As ternary system, the values between 0.2 and 0.3 were obtained for the distribution ratio of gold, L^sp/Pb_Au defined by [wt%Au in speiss/wt%Au in lead], in the composition range of 25-50 wt%As in speiss phase. In Pb-Cu-As system, gold distributes 3 or 4 times in the speiss phase more than in the lead phase. In quarternary system which is added copper to Pb-Fe-As system, the distribution ratio of gold increases and approaches that of Pb-Cu-As ternary system with increasing copper content in the speiss phase. From the behavior of the distribution ratio of gold and the analysis of speissby EPMA, it is supposed that copper takes part in the dissolution of gold in the spiess.
For the purpose of recovery of precious metals dissolved in the speiss, it is considered that the speiss ismelted with the lead which is free from impurities, then the precious metals dissolve into lead from the speiss phase and those can be recovered in the refining process of lead. The recovery of silver and gold by this method is able to estimate by using the experimental results on the distribution ratio and the miscibility gap. The results of check tests were found to be in good agreement with the estimated values for both silver and gold.