Tal'vak acid
From The Stargate Omnipedia
Instrument of torture used by the Goa'uld Baal. In combination with his heavy gravity field technology, Baal would flick small drops of this fluid upon those who possessed information he wanted. Though the acid cauterizes the skin, it can continue to seep into the body and, sometimes, into the bloodstream.
An antidote is administered to those who cooperate by offering withheld secrets. This compound is almost identical in appearance to its deadly counterpart.
KEY EPISODE
Abyss - Baal tortures a captured Jack O'Neill with gravity wells, daggers and tal'vak acid.