Your friend doesn't get it, the active ingredient is chlorine dioxide, which you only get from combining sodium chlorite (verrrry alkaline) with an acid such as citric acid or hydrochloric acid.... then you get the perfect PH of 7.5. Yes, you start to loose the chlorine dioxide when it is mixed.... but if you have ever drank any you would know that not much is lost in the half minute it takes to get it to your mouth as you can taste and smell it for quite a few minutes (guess I'll have to test it to see how long it lasts), but if you know you aren't drinking all of it down it's best to keep it in a bottle with a lid.
And you don't need to rinse your mouth after drinking it unless you didn't mix it properly, there's a toothpaste you can buy - FDA approved - it is two tubes that you mix. It is safe, just need to follow instructions, equal parts of each. And wow, stops gum disease, no more cavities and when you wake up have to remind yourself to brush your teeth as you don't have that morning slime anymore.
When you said to drink it unactivated - that is dangerous.... it is pure sodium chlorite, top of the alkaline charts, it won't do anything good for you. Jim Humble would be beside himself to read your post.
But yes, acid is what digests your food, and it's hydrochloric acid which is in your tummy doing the work... the very same that you should mix the miracle mineral with....so when you mix it with sodium chlorite - that is two things that your body already knows and loves.