1) Masking agnets :-
A masking agent is a reagent used in chemical analysis which reacts with chemical species that may interfere in the analysis.
Potassium cyanide is an effective masking agent for large quantities of cations.
2) Demasking agnets :-
Demasking agents are chemical reagents that are useful in introducing the impurities which were masked before the reaction mixture.
The masking by CN– can be removed by mixture of formaldehyde, acetic acid on addition of demasking agent to [Zn (CN)4]2- Zn is liberated and titrated.
