Formation of Yellow Precipitate in Ammoniacal Buffer Oxime with Mg(2), Ca(2), Ba(2), and Sr(2)

Ammoniacal buffer oxime is a complexing agent that forms a yellow precipitate with certain metal ions. The following is an explanation of how the yellow precipitate forms with Mg(2), Ca(2), Ba(2), and Sr(2).

Ammoniacal Buffer Oxime

Ammoniacal buffer oxime, or 8-hydroxyquinoline, is a chelating agent that forms stable complexes with metal ions. In solution, it exists in equilibrium between the neutral and protonated forms:

HOC9H6N = H+ + OC9H6N

When ammonia is added to the solution, it reacts with the protonated form to form the ammonium salt:

HOC9H6N + NH3 → NH4+OC9H6N

This ammoniacal buffer oxime is used to test for the presence of certain metal ions.

Precipitation with Mg(2)

When ammoniacal buffer oxime is added to a solution containing Mg(2), a yellow precipitate forms. This is due to the formation of a complex between the ammoniacal buffer oxime and the Mg(2) ion:

Mg2+ + 2OC9H6N → Mg(OC9H6N)2

This complex is insoluble in water, which is why a precipitate forms.

Precipitation with Ca(2)

When ammoniacal buffer oxime is added to a solution containing Ca(2), a yellow precipitate also forms. This is due to the formation of a complex between the ammoniacal buffer oxime and the Ca(2) ion:

Ca2+ + 2OC9H6N → Ca(OC9H6N)2

This complex is also insoluble in water, which is why a precipitate forms.

Precipitation with Ba(2)

When ammoniacal buffer oxime is added to a solution containing Ba(2), a yellow precipitate forms as well. This is due to the formation of a complex between the ammoniacal buffer oxime and the Ba(2) ion:

Ba2+ + 2OC9H6N → Ba(OC9H6N)2

This complex is also insoluble in water, which is why a precipitate forms.

Precipitation with Sr(2)

When ammoniacal buffer oxime is added to a solution containing Sr(2), a yellow precipitate forms too. This is due to the formation of a complex between the ammoniacal buffer oxime and the Sr(2) ion:

Sr2+ + 2OC9H6N → Sr(OC9H6N)2

This complex is also insoluble in water, which is why a precipitate forms.

In conclusion, the yellow precipitate formed when ammoniacal buffer oxime is added to a solution containing Mg(2), Ca(2), Ba(2), and Sr(2) is due to the formation of insoluble complexes between the ammoniacal buffer oxime and the metal ions. These complexes are yellow in color and thus form a visible precipitate.