Refining of the Lead Buttons from Nickel and Antimony Impurities in Fire Assay of Gold and Silver

Abstract

A new technique of refining lead buttons from nickel and antimony impurities in fire assay of gold and silver is developed. The technique is based on low-temperature (700°C) alkaline melting of lead buttons with a saltpeter oxidant present. The proposed method of lead buttons purification is more time-efficient and rather easy to use compared to traditional melting in a scorifying dish: refining at a lower temperature does not require an air blow through the furnace and permanent change of scorifying dishes. Stainless crucibles appeared resistant to alkali-induced damage upon low temperature melting and can be used multiple times. The developed technique is recommended for purification of lead buttons from nickel and antimony impurities as an alternative to traditional melting in scorifying dish.