Phosphoric acid? It's used to supplement the use of malic acid (Magnesium malate) for preparing to do a flush.
It's advised to brush your teeth after using phosphoric acid. I think it's a bit much, and I only use malic. Malic will do the trick. You can buy it in powder form as Magnesium malate, or drink apple juice or cranberry or sour cherry or red grape, etc.