In dilute aqueous solution hydrogen fluoride behaves as a weak acid, Infrared spectroscopy has been used to show that, in solution, dissociation is accompanied by formation of the ion pair ·F−. : + 2<unk>  + F− + ⋅F−pKa = 3.17 This ion pair has been characterized in the crystalline state at very low temperature. Further association has been characterized both in solution and in the solid state. :HF + F− log K = 0.6 It is assumed that polymerization occurs as the concentration increases. This assumption is supported by the isolation of a salt of a tetrameric anion and by low-temperature X-ray crystallography. The species that are present in concentrated aqueous solutions of hydrogen fluoride have not all been characterized; in addition to which is known the formation of other polymeric species, , is highly likely. The Hammett acidity function, H0, for 100%<unk>  is estimated to be between −10.2 and −11. which is comparable to the value −12 for sulfuric acid.
Hydrofluoric acid
Dichloroacetic acid
Hydrochloric acid
Tetrachlorodecaoxide
Benzoyl peroxide
Denatured alcohol
Perchloryl fluoride
Diiodohydroxyquinoline