Mac arther forest process/cyanide process

$\mathrm{Ag}_{2} \mathrm{S}+4 \mathrm{NaCN} \stackrel{\mathrm{O}_{2}}{\longrightarrow} 2 \mathrm{Na}[\mathrm{Ag}(\mathrm{CN})_2]+\mathrm{Na}_{2} \mathrm{SO}$

$2 \mathrm{Na}[\mathrm{Ag}(\mathrm{CN}),] \stackrel{\mathrm{Zn}}{\longrightarrow} \mathrm{Na}_{2}\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]+\mathrm{Ag}(\downarrow)$

Soluble complex $Ag$ extracts by displacement with $Zn$