Illustrated Glossary of Organic Chemistry

Hydrofluoric acid: An aqueous solution of hydrogen fluoride (HF). Unlike hydrochloric acid, hydrobromic acid, and hydroiodic acid, hydrofluoric acid contains little H₃O⁺ F^-, because HF (pK_a 3.2) is a weaker acid than H₃O⁺ (pK_a -1.78). Hydrofluoric acid is notorious for its ability to dissolve glass. This not because hydrofluoric acid is a strong acid, but instead because the Si-F covalent bond is among the strongest of all covalent bonds known.

Hydrofluoric acid dissolves glass, so it must be stored a container made of plastic (such as Teflon).		Glass that has been etched by hydrofluoric acid.