Nitric acid
From Memory Alpha, the free Star Trek reference
Nitric acid (HNO3) was a nitrogenous chemical compound which was a colorless, corrosive liquid. It was a toxic, highly acidic oxidizing agent which could cause severe burns.
In the holodeck program Insurrection Alpha, as rewritten by Seska, the Doctor applied 20 ccs of nitric acid to a wound Tom Paris had received, noting it as "a little proverbial salt in the wound." (VOY: "Worst Case Scenario")
