Surface pressure (pi)- and surface potential (Delta V)-area (A) isotherms for monolayers of alkylammonium perfluorohexanoates of four different alkyl chains (m) on water and 4.4 M NaCl solutions were measured at various temperatures by the Langmuir and the ionizing electrode methods. As for the octadecylammonium perfluorohexanoates (C18F11) of this long-hydro-short-fluoro chain salt pi-A curves showed three phase transition points. There exists a triple point on the phase diagram at which three phases(E, C-I, and C-I’) coexist. From the surface pressure and surface potential measurements, the orientation of long-hydro-short-fluoro chain salts in the monolayer state was discussed.