Extraction of Silver :
(a) `text(Ores)` : Silver glance or argentite `Ag_2S`, Ruby silver `Ag_2S*Sb_2 S_3`, Horn silver `AgCl`
(b) `text(Process)` : Cyanidation or Mac-Arthur-Forrest cynide process : See fig.
(c) `text(Reactions (Leaching))` :
`Ag_2S + 4 NaCN -> 2Na[Ag(CN)_2] + Na_2S`; passing of air causes oxidation of `Na_2S`, there by forward reaction takes place.
`4Na_2S + 2H_2O + 5O_2 -> 2Na_2SO_4 + 4NaOH + 2 S`
`undersettext(sodium argento cyanide)(2Na [Ag(CN)_2]) + Zn -> undersettext(sodium zinco cyanide)(Na_2[Zn(CN)_4]) + 2Ag downarrow`
The precipitated silver is separated and purified by fusion with borax or `KNO_3` to get pure silver.
Electrolytic refining :
Anode : Impure `Ag`
Cathode : Pure `Ag`
Electrolyte : `AgNO_3(aq.) + HNO_3`
(b) `text(Process)` : Cyanidation or Mac-Arthur-Forrest cynide process : See fig.
(c) `text(Reactions (Leaching))` :
`Ag_2S + 4 NaCN -> 2Na[Ag(CN)_2] + Na_2S`; passing of air causes oxidation of `Na_2S`, there by forward reaction takes place.
`4Na_2S + 2H_2O + 5O_2 -> 2Na_2SO_4 + 4NaOH + 2 S`
`undersettext(sodium argento cyanide)(2Na [Ag(CN)_2]) + Zn -> undersettext(sodium zinco cyanide)(Na_2[Zn(CN)_4]) + 2Ag downarrow`
The precipitated silver is separated and purified by fusion with borax or `KNO_3` to get pure silver.
Electrolytic refining :
Anode : Impure `Ag`
Cathode : Pure `Ag`
Electrolyte : `AgNO_3(aq.) + HNO_3`