When used intelligently, orthophosphoric acid can do wonders and is great to balance autonomic nervous system and help calcium metabolism and energy production. It is also great to help dissolve gallstones as you mention - I've used it with no problems. Care must be taken after drinking to ensure teeth don't get harmed, but tell that to the millions of people who drinking CocaCola/Pepsi at much higher levels than recommended dosage of phosphood/ortho phos (they are after all phosphoric acid and sugar and will too dissolve a nail). The Coke liver flush uses this knowledge to dissolve gallstones as well.