However, for other purposes they are distinct. Removing the second proton from carbonic acid (H₂CO₃), to form washing soda, takes more oomph than removing the first--which forms baking soda. Since these reactions are reversible, this means that washing soda is a stronger base than baking soda, and in fact is considered a caustic (which means that, among other things, you DON'T want to use it for baking!) If you rub a little washing soda on your hands, then rinse it off, your hands feel soapy; baking soda doesn't do that, and the reason is that baking soda is too mild a base.