Extraction of silver.
The extraction of silver is carried out yesteryear diverse techniques which normally depend upon the type of ore. The next processes are normally used:
- Cyanide Process.
Mostly Ag is forthwith extracted yesteryear this procedure. The regulation of the physical care for is to larn Ag+ into solution every bit dicyanoargentate ion, [Ag(CN2] ¯ in presence of CN ¯ ions. Silver metallic element too its compounds are easily soluble inwards alkali cyanide solutions inwards the presence of air. The metallic element Ag is deposited from cyanide solution inwards the presence of reducing agents such every bit zinc or aluminum (hydroquinone may likewise last used every bit investigated yesteryear authors).
The finely dissever ore, normally Ag sulfide, is agitated alongside most 1% NaCN solution for most 48 hours inwards a electrical flow of air. Silver gradually goes into solution every bit sodium dicyanoargentate, Na [Ag(CN)2].
If the ore contains AgCl, the reaction is:
The Ag is normally deposited from Na [Ag(CN)2] yesteryear handling alongside Zn.
The precipitated Ag is filtered, washed too so melted alongside KNO3 to oxidize whatsoever zinc.
The physical care for of extraction of silver may last shown schematically as:
- Amalgamation Process.
The ore (Ag2S) is soil to a glue alongside H2O too treated alongside cupric chloride (or NaCl too (CuSO4) when Ag2S is converted into AgCl.
The products are mixed alongside metallic element mercury when Ag is deposited.
The Ag thence obtained may shape am amalgam inwards presence of excess mercury. Excess mercury may last removed yesteryear distillation inwards retorts.
- Extraction from Commercial Lead.
Small quantities of Ag acquaint inwards Pb or Pb ores tin last economically extracted yesteryear Parkes’ process. This physical care for is based upon the partitioning Law. According to that, molten Pb dissolves most 1 % Zn too molten zinc dissolves most 1% pb. But Ag is completely soluble inwards molten zinc. Thus, yesteryear adding molten zinc to the fused lead-silver alloy, Ag goes inwards molten zinc forming Zn – Ag alloy which solidifies too floats on the surface of molten lead. Silver is obtained pure yesteryear distilling zinc. This physical care for is likewise called the desilverization of lead.
The modest quantity of Pb which may stay inwards Ag is removed yesteryear Cupellation process. The mixture is placed inwards a cupellation furnace ( Figure 1.1) too a boom of hot air passed over it. Lead is converted PbO. PbO is blown off leaving behind Silver.
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