The Effect of Short‐Range Hydrogen‐Bonded Interactions on the Nature of the Critical Point of Ionic Fluids. Part I: General Properties of the New System Ethylammonium Nitrate+n‐Octanol with an Upper Consolute Point Near Room Temperature

Abstract We report on an unusual liquid‐liquid miscibility gap with an upper consolute point at 315.2 K in the ionic system ethylammonium nitrate+n‐octanol at a mole fraction x 1 = 0.773 of the salt. Similar phase separations of 1:1‐electrolytes in solvents of low dielectric constant were only found in the solvent‐rich regime at low ion densities, as predicted for charged hard spheres in a dielectric continuum. In analogy to other low‐dielectric constant systems the equivalent conductance exhibits 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 predicted theoretically and expected by comparison with data for similar systems. This additional stability of the ion pair may be due to hydrogen‐bonds between C 2 H 5 NH + 3 and NO − 3 . Possible mechanisms for phase separation are discussed.

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