THE EFFECT OF SHORT-RANGE HYDROGEN-BONDED INTERACTIONS ON THE NATURE OF THE CRITICAL-POINT OF IONIC FLUIDS .1. GENERAL-PROPERTIES OF THE NEW SYSTEM ETHYLAMMONIUM NITRATE -OCTANOL WITH AN UPPER CONSOLUTE POINT NEAR ROOM-TEMPERATURE(N)

We report on an unusual liquid-liquid miscibility gap with an upper co nsolute point at 315.2 K in the ionic system ethylammonium nitrate+n-o ctanol at a mole fraction x1 = 0.773 of the salt. Similar phase separa tions of 1 : 1-electrolytes in solvents of low dielectric constant wer e only found in the solvent-rich regime at low ion densities, as predi cted for charged hard spheres in a dielectric continuum. In analogy to other low-dielectric constant systems the equivalent conductance exhi bits a minimum at low salt concentrations due to the specific features of the ion distribution under these conditions. The pair association constant is however one to two orders of magnitude larger than predict ed theoretically and expected by comparison with data for similar syst ems. This additional stability of the ion pair may be due to hydrogen- bonds between C2H5NH3+ and NO3-. Possible mechanisms for phase separat ion are discussed.