Quote Originally Posted by albada View Post
One difficulty is ascorbate is hard to find, so to clone XTOL, one must separately convert some ascorbic acid into ascorbate by adding sodium bicarbonate (baking soda). The problem with that is if the correct amounts of both ingredients are mixed, it will theoretically take a nearly infinite amount of time to convert all the ascorbic acid. To see why, suppose there is one molecule remaining of each ingredient. It will require perhaps years of stirring before those two molecules touch each other. So to complete the conversion in reasonable time, an excess of bicarbonate is needed. But what will that do to the developer?
Mark Overton
Mark, I know you wrote this a while ago, but I've been meaning to comment on it. I would be very surprised if (in general when reacting chemicals together), one needs to place greater quantities of one chemical in order to ensure sufficient reaction completion (assuming reaction rate time constants are not in the order of hours or days). I'm going to assume that the percent of reactant and product both change exponentially w.r.t. time. If so then the reaction will have a time constant (k), such that for a first order reaction,
[A(t)] = [A(0)] exp(kt)

unless k is in the order of hours or days (lets say it is in the order of seconds) then surely you will have sufficient equilibrium after a matter of minutes ? OK I just read here (Summary for reaction orders 0, 1, 2, and n) , that perhaps you have a zero order reaction. Is that the case ? In which case the product concentration only rises linearly not exponentially. Even then I don't imagine you would gain much time advantage by upping a reactant.

Disclaimer: I'm a mathematician and electrical engineer, not a chemist !