This liquid is not actually a potion to be drunk (though if it is drunk it will taste good), but it is to be added to other liquids in order to change them to pure, drinkable water. 

It will neutralize poison and ruin magic potions (no saving throw). 

The contents of the container will change up to 100,000 cubic feet of polluted or salt or alkaline water to fresh water. 

It will turn up to 1,000 cubic feet of acid into pure water. 

The effects of the potion are permanent, but subject to later contamination or infusion after an initial period of 5-20 rounds.