During the qualitative analysis of salt with cation Ni2+, addition of a reagent Dimethylglyoxime to alkaline solution of the salt gives a bright red precipitate according to the following reaction. So, The reagent (X) and the cation (y2+) respectively are Dimethylglyoxime and Ni2+
Ni2++dmg→AmmonicalSolutionRedcolur[Ni(dmg)2]↓,