Acid

Acid is a chemical compound that is caustic in nature.

The seas of Marinus were of acid. (DW: The Keys of Marinus)

The planet Vortis had pools of acid on its surface. (DW: The Web Planet)

The Doctor defeated the Krotons by using sulphuric acid against them. (DW: The Krotons)

After being returned to Kastria, Eldrad fell victim to an acid trap. (DW: The Hand of Fear)

Cessair was allergic to citric acid. (DW: The Stones of Blood)

On Jaconda, Mestor's body was destroyed with a beaker of acid. (DW: The Twin Dilemma)

On Varos, the Doctor escaped from being dissolved in an acid bath. (DW: Vengeance on Varos)

On Earth, coronic acid was used against the Sontarans Stike and Varl. (DW: The Two Doctors)

Cassandra O'Brien's surgeons used moisturisers filled with acid to defend her. (DW: The End of the World)

The calcium-based bodies of Raxacoricofallapatorians were vulnerable to acetic acid. On Raxacoricofallapatorius, criminals were executed by being dissolved in a vat of acetic acid while still alive. (DW: Aliens of London, World War Three, Boom Town)

The seas of 16 Alpha Leonis One were of sulphuric acid. (NA: Eternity Weeps)

The seas of Endpoint were of acid. (EDA: Hope)