gen ▁flu or ide ▁structure , ▁before ▁dis order ▁begins ▁to ▁prev ail ▁as ▁the ▁temperature ▁is ▁raised . ▁A que ous ▁hydro gen ▁b rom ide ▁is ▁known ▁as ▁hydro b rom ic ▁acid , ▁which ▁is ▁a ▁strong ▁acid ▁( p K a ▁= ▁− 9 ) ▁because ▁the ▁hydro gen ▁b onds ▁to ▁b rom ine ▁are ▁too ▁weak ▁to ▁in hib it ▁dis soci ation . ▁The ▁H Br / H 2 O ▁system ▁also ▁involves ▁many ▁hyd r ates ▁H Br · n H 2 O ▁for ▁n ▁= ▁ 1 , ▁ 2 , ▁ 3 , ▁ 4 , ▁and ▁ 6 , ▁which ▁are ▁essentially ▁sal ts ▁of ▁b rom ine ▁an ions ▁and ▁hyd ron ium ▁c ations . ▁H ydro b rom ic ▁acid ▁forms ▁an ▁a ze ot ro pe ▁with ▁bo iling ▁point ▁ 1 2 4 . 3   ° C ▁at ▁ 4 7 . 6 3   g ▁H Br ▁per ▁ 1 0 0   g ▁solution ; ▁thus ▁hydro b rom ic ▁acid ▁cannot ▁be ▁concentr ated ▁beyond ▁this ▁point ▁by ▁dist ill ation . ▁ ▁Un like ▁hydro gen ▁flu or ide , ▁an h yd r ous ▁liquid ▁hydro gen ▁b rom ide ▁is ▁difficult ▁to ▁work ▁with ▁as ▁a ▁sol vent , ▁because ▁its ▁bo iling ▁point ▁is ▁low , ▁it ▁has ▁a ▁small ▁liquid ▁range , ▁its ▁die lect ric ▁constant ▁is ▁low ▁and ▁it ▁does ▁not ▁dis soci ate ▁appreci ably