Not sure if Anybody's found this yet, but after drinking the white phial from the quest, you can go to your MISC and select it, it will say "You cannot equip this item" but the phial duplicates as you try to use/equip it! (Not sure if the other non-original phials will refill, but I know atleast one does )

You have eto do it just after you've drank the potion and if you leave the room/town/whatever you're in you can't duplicate it anymore....until of course one refills an you drink it!