ɛkspˌɛɹɪmˈɛntəl ˌiːkwɪlˈɪbɹiəm mˈɛʒɚmənts, ɪts æn vˈæljuː ɡˈʌtmənbˈɛkɪt mˈɛθəd æz wˈɛl æz kwˈɔntəmkˈɛmɪkəl kˌælkjʊlˈeɪʃənz ˈɔːl ˈɪndᵻkˌeɪt ðætðə lˈuːɪs æsˈɪdᵻɾi ʌv ɪz slˈaɪtli lˈoʊɚ ðɐn ðæt ʌv ænd sɪɡnˈɪfɪkəntli ɹᵻdˈuːst kəmpˈɛɹd tuː .  fˈɔːɹmz ɐ stɹˈɔŋ lˈuːɪs ɐdˈʌkt wɪð wˈɔːɾɚ, wˌɪtʃ wʌz ʃˈoʊn təbi ɐ stɹˈɔŋ bɹˈɑːnstᵻd ˈæsɪd hˌævɪŋ ɐn æsˈɪdᵻɾi kˈɑːmpɚɹəbəl tə hˌaɪdɹəklˈoːɹɪk ˈæsɪd ɪn ˈæsɪtˌɑːnaɪtɹˌaɪl.
Experimental equilibrium measurements, its AN value (Gutmann-Beckett method) as well as quantum-chemical calculations all indicate that the Lewis acidity of  is slightly lower than that of  and significantly reduced compared to .  forms a strong Lewis adduct with water, which was shown to be a strong Brønsted acid having an acidity comparable to hydrochloric acid (in acetonitrile).