Solubility product of a sulphide MS is 3 × 10−25 and that of another sulphide
NS is 4 × 10−40. In ammonia solution
Both sulphides precipitate
The concentration of S2− ions in group II is lowered by maintaining acidic
medium in the presence of NH4Cl. The ionization of H2S is supressed due
to common ion effect. So the ionic product is less than solubility product.