Role Of Purification In SA Precious Metals (SA Pty) Ltd.

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Introduction
Silver, like gold, is found in a native state; frequently too it occurs as an alloy containing gold, which is recognized, when the silver is dissolved in nitric acid, as the black sediment or oxide of gold. Arsenic and antimony are found also alloyed with it. Several of the ores of lead and copper contain silver. As silver is a precious metal often used for coins, its mining has historically often been lucrative. As with other precious metals such as gold, newly discovered deposits of silver ore have sparked silver rushes of miners seeking their fortunes.
Silver is a precious metal well known for its singular beauty as well as for its utilization in electronic technology, photography and medical purposes. The most popular electrolytes
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Literature Review (Feasibility of the process)
Nitric Acid leaching of silver is a proposed alternative to cyanide, thiourea or thiosulphate leaching for certain types of refractory silver ores and secondary sources. (source)
Solubility rules state that nitrate salts are soluble in water, and silver nitrate is no exception. When the soluble silver (I) nitrate salt solution is combined with the soluble sodium chloride salt solution, a white precipitate of silver (I) chloride is produced. (Source)
Silver can also be dissolved using thiosulfate solution. However, studies have shown that the resultant AgNO3 electrolyte is considered to be ideal for further silver recovery via electrolysis or precipitation processes is due to its high recovery performances than that of the silver thiosulfate electrolytes. AgNO3 would seem to overcome the existing problems encountered during direct electrolysis and precipitation of silver from thiosulfate electrolytes where pH and sulfite controls have usually affected the precipitation and electrolytic efficiency and
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in pH meters
• Infrared windows where it can be used in contact with many aqueous solutions e.g. in FTIR spectrometers, in which case it can be an alternative to KBr, which is attacked by water.

Materials and Experimental Procedure
A stock solution was prepared using 99.27 g of sodium thiosulphate (Na2S2O3•5H2O), sodium hydroxide (for pH adjustment) and 145 mg of silver sulphate (Ag2SO4). The sodium thiosulphate was dissolved in distilled water to produce a 0.4 M solution in slightly less than 1000 ml volume. The pH was adjusted to 9.5 by sodium hydroxide. Distilled water was added to bring the final volume of 1000 ml. The mentioned amount of silver sulphate was dissolved in this solution. Atomic absorption spectroscopy indicated that the silver concentration was 100 µg/ml in the final stock solution
In the process of leaching silver harmful gases emitted, therefore the experiment should be carried out in environment that consent with gas emission such as fume hoods and scrubber.
Feed materials
• Silver grain samples (1.85 kg)
• Nitric Acid
• De-ionized water
• Hydrochloric

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