[Delphinus]

Actually I think baking soda all by itself is just sodium bicarbonate, and you want a few carbonate ions in there too. (Hmmm. I probably have that backwards, but, you get the idea.) It's the fact that you want both bicarbonate AND carbonate, and baking soda is only the one, and washing soda (yup, Arm & Hammer brand :D ) is the other kind. The exact recipe and the reasoning and explanations can be found on RC, even just do a search in Randy's chem forum, I beleive he has even suggested the "cheapy super buffer solution" in the past.