During the estimation of nickel,we prepare nickel dimethylglyoxime,a scarlet red solid. This compound is . . . . . . .

The deep blue colour produced on adding excess of ammonia to copper sulphate is due to the presence of:

The compound $ZnFe_2O_4$ is:

$[Cu(CN)_4]^{2-}$ is colourless as it absorbs light in

Aqueous copper sulphate solution (blue in colour) gives:
$(i)$ a green precipitate with aqueous potassium fluoride,and
$(ii)$ a bright green solution with aqueous potassium chloride
Explain these experimental results.

Dimethyl glyoxime forms a coloured complex with