[Blue212]

Hey, I did an experiment to reduce vanadate from a solution of ammonium vanadate with sulfruic acid, ammonium sulfite, and bubbling SO₂ though the process.

I know it produces VO²⁺ because it produces a green color but I am not sure why bubbling the SO₂ was necessary. Anyone have any ideas?

[Borek]

From your description it is not clear to me as well.

What is the reducing agent? What was initial concentration of vanadate? Ammonium sulfite?

[zolarpwr]

The reaction may generate water which could dilute the sulfite and limit its effectiveness. The gas addition is probably just to maintain a high sulfite concentration.

As another example when you see a procedure that calls for fuming acid, that's really just the concentrated acid plus excess of the anhydrous vapor, like sulfuric acid and SO3, nitric and NOx, or hydrochloric and HCl. Your case is the same with sulfurous acid and SO2 but in basic conditions.