Gallic Acid
The Flask with Gallic Acid is a flask containing gallic acid, which is used to restore ancient documents. This bottle is coloured yellow, blue and red.
Twinsen first hears about gallic acid from his elderly neighbour, when he tells him he needs such acid in order to restore a map of the Citadel Island sewers. He also tells him that none is left on the island. Twinsen can get the acid from either Ker'aooc's house in Port Ludo, or from the narby bazaar for 50 kashes. After Twinsen's neighbour receives the acid, he uses it to restore the map, which reveals a pyramid-shaped key. He then gives the key to Twinsen, who later uses it to enter the room in the sewers where Sendell's Ball is concealed in an icy cage.
Additionally, Twinsen learns from the racer in Von Kournil Tour that it is possible to boost his car with gallic acid, although this does not appear in the game.
