To project acid from the hands or the mouth
Fear, Hatred, Anger
Acid Secretion is the ability to generate corrosive acid from the hands or mouth that can severely burn people or melt objects.
A Demonic Power Broker infected the mortal Karen Young with a power ball which contained this power, allowing her to project acid from her hands. Karen accidentally burned Paige and then melted a computer monitor in her office before Piper and Phoebe forced her to drink a power stripping potion to rid her of this power.
Cole returns from the Wasteland
When Cole returned from the Wasteland, Phoebe cut him with a blade when he refused to leave her alone. She was shocked to discover that his blood was melting through a paper. Also the blade she used had its tip eaten away because of his blood.
Scabbar Demons attack Chris
Scabbar Demons have this power. It allows them to shoot strings of acid from their mouth. While attacking Chris, their acid secretion damaged the scrying crystal, map and partial area of an oak table. Paige safely rescued the Book from possibly melting. Later Paige changed Rick's appearance so that he looks like Chris. When the demons shimmered in, they were able to kill him easily with their power and Rick melted onto the floor. 
List of beings who use(d) Acid Secretion
- Original power
- Scabbar Demons
- Through power stealing, etc.
- Cole Turner (After returning from the Demonic Wasteland, Cole blood turned acidic)
- Karen Young (While infected by Demonic Power Brokers)
- Season 4, "The Fifth Halliwheel"
- Season 5, "A Witch's Tail, Part 1"
- Season 6, "Hyde School Reunion"