Coronic acid

Coronic acid was a type of acid that was harmful to Sontarans, causing damage to their bodies and their armour, killing them on contact. The substance produced large showers of white sparks, similar to burning magnesium.

It was used against them in 1985 by Chessene of the Franzine Grig (DW: The Two Doctors), and in 2370 by Raghi defence forces. (MA: Lords of the Storm)