Metallurgy

$$ \begin{aligned} 4 \mathrm{Ag}(s)+8 \mathrm{CN}^{-}(a q) & +2 \mathrm{H}_2 \mathrm{O}(a q)+\mathrm{O}_2(g) \longrightarrow 4\left[\mathrm{Ag}(\mathrm{CN})_2\right]^{-}(a q)+4 \mathrm{OH}^{-}(a q) \end{aligned} $$

The above reaction represents the process of concentration of ore in the extraction of silver. The process is