Potion of acid
A potion of acid may not be #dipped to become water; if it gets wet, it will boil and cause you 1-10 points of damage. However, a potion of acid can be cancelled to turn it into a potion of water. If you quaff a potion of acid when you are turning to stone, you will be cured of your stoning. Otherwise, you will take from 1-16 points of damage and abuse your constitution. They are best used either as an emergency stoning cure (or a primary one, for vegans and vegetarians), or as a thrown weapon.
If a monster throws a potion and hits another monster with it, or you throw an unidentified potion at a monster, and the monster "shrieks in pain" or "writhes in pain", the potion is a potion of acid, unless it is a clear potion, in which case it was holy water.
