Can anyone show me the reaction of sodium carbonate with water to produce bicarbonate and hydroxide as sodium carbonate dissolves? And if any, what is the reaction of tannins and caffeine with this solution? Thanks loads!

Answer 1

CO3^-2 + HOH ==> HCO3^- + OH^-
Strictly a guess but I suspect tannic acid reacts with the HCO3^-.
Some "tanning" processes use acids and the bicarbonate could be used to neutralize those excess acids. Here is a site, not very technical, but come information can b gleaned from it.
http://home.alltel.net/henryh/Lea&Mat.htm

Answer 2

Thanks Dr. For our intents and purposes I don't believe there to be a reaction. Thank you for your awesome help all the same!