Silver from lead ores

Of interest also is the high-temperature liquid-liquid extraction of molten silver dissolved in molten lead, the extraction solvent being molten zinc (Parkes process) this process is analogous to the familiar extraction of bromine from water using carbon tetrachloride, and is used to recover silver from lead ores. 

In the presence of oxygen, aqueous sodium cyanide dissolves most metals in the finely divided state, with the exception of lead and platinum. This is the basis of the MacArthur process for the extraction of gold and silver from their ores that, in the case of gold, may be represented as follows ... 

Precious metals such as silver and gold, which are seldom oxidized even at high temperatures, are often refined by cupellation, a process for removing from them base metal impurities such as lead and tin, with which they are associated in many ores. Hot lead and tin are easily oxidized. In the cupellation process, a crude, impure precious metal is placed in a shallow cup or crucible made of bone ash, known as a cupel, and is then heated by a blast of hot air. At high temperatures, the base metal impurities are oxidized by oxygen in the hot air, and the oxides thus formed are absorbed by the porous bone ash. The Chaldeans are said to have been the first to have utilized (ca. 2500 b.c.e.) cupellation to remove lead and purify silver from lead-silver ores. 

Brittania A process for removing silver from lead, operated by Brittania Refined Metals in England, using ore from the Mount Isa mine in Australia. After initial concentration by the Parkes process, and removal of the zinc by vacuum distillation, the mixture, which contains silver (70 percent), lead, and some copper is treated in a bottom blown oxygen cupel in which lead and copper are removed by the injection of oxygen through a shielded lance. 

Tainton A metallurgical process in which sulfides are converted to sulfates by heating in a controlled quantity of air, and the sulfates so produced are dissolved out in water. Used for removing zinc from silver and lead ores. 

The actual isolation of zinc metal on an appreciable scale seems to have occurred first in China in the 10th Century AD (Xu, 1990), using an upwards distillation procedure from secondary (oxidized) zinc minerals. Earlier finds of metallic zinc (such as that at the Agora, noted above) are possibly explained by the chance condensation of small quantities of zinc in the furnace during the production of lead and silver from mixed ores. Much attention has been focused in recent years on northern India, particularly the Zawar region,... 

Preparation.3—The methods employed in the manufacture of silver from its ores can be classified in three main divisions (1) amalgamation, employed in countries where fuel is scarce (2) Imviation (3) smelting, the metal being subsequently separated from metallic lead or copper. 

Nine of ten ornaments found at Allahdino have a lead isotope composition similar to that of silver-containing lead ore from South Balochistan (Figure 20-20), which is near Allahdino. Five ornaments from Mohenjo-daro and one of ten from Allahdino do not match any known mining sites in Pakistan but are similar in isotopic composition to ore from South Rajasthan in India and a site across the Arabian Sea in Oman. It is possible that the silver came from these more distant sites. Archaeologists make increasing use of the most sophisticated analytical techniques to address question in anthropology. 

In Sweden a silver-rich lead ore was mined in Sala from the beginning of the 16 century but lead was not taken care of until the middle of the 18 century. Today Sweden is the largest lead producer in Europe, mainly due to the great deposit in Laisvall in the north of the country. Mining there began in 1943. 

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