An ammoniacal metal salt solution gives a brilliant red precipitate on addition of dimethylglyoxime. The metal ion is :Cu2+Ni2+Fe2+Co2+

Analysis of the Problem

To determine which metal ion corresponds to the formation of a brilliant red precipitate upon the addition of dimethylglyoxime, we need to know the characteristic reactions of dimethylglyoxime with various metal ions.

Relevant Concepts

1. Dimethylglyoxime Reaction: Dimethylglyoxime (DMG) is a reagent that specifically forms colored complexes with certain metal ions, notably nickel(II) ions (Ni²⁺).
2. Metal Ion Identification:
   • Cu²+: Forms a complex with DMG but does not produce a brilliant red precipitate.
   • Ni²+: Forms a bright red precipitate known as nickel dimethylglyoxime.
   • Fe²+ and Co²+: Typically do not give a bright red precipitate with DMG.

Conclusion and Final Answer

Based on the known reaction of dimethylglyoxime with metal ions, the ammoniacal metal salt solution that gives a brilliant red precipitate upon the addition of dimethylglyoxime is most likely Ni²+ (Nickel ions).