Potassium?

[Thomas]

I think we shall need a chemist to get you a definitive answer.

I know that potassium tartrate (tartaric acid) is part of grape juice's natural component structure and that some of it remains in wine and forms part of wine's acidic back bone.

Small wineries used to administer sulfite doses in the form of potassium metabisulfite powder, but that practice should be all but dead by now. Sulfites are generally administered as a liquid gas.

Maybe Bucko can help here.