Gold extraction the purity of gold. The parting of gold from silver has been done since ancient times starting in Lydia in the 6th century BC. Various techniques have been practised; salt cementation from ancient times, parting using distilled mineral acids from medieval times, and in modern times using chlorination using the Miller process and electrolysis using the Wohlwill process. Gold extraction Gold extraction refers to the processes required to extract gold from its ores. This may require a combination of comminution, mineral processing, hydrometallurgical, and pyrometallurgical processes to be performed on the ore. Gold mining from alluvium ores was once achieved
Ultra-high-purity steam for oxidation and annealing and is both less expensive and safer. An effective passivation of the rear surface of industrial solar cells is a prerequisite to considerably improve the conversion efficiency. An excellent level of surface passivation on lowly doped p-type surfaces is provided by thermal grown silicon oxides. However, dry thermal oxidation processes require relatively high temperatures (>1000 °C) and, due to the low growth rate, long process times. To decrease both oxidation temperature and process time the dry oxidation process can be replaced by a wet oxidation followed by nitrogen annealing. Best cell performance requires a forming gas anneal after firing. Ultra-high-purity