Cryoscopic comparison of nitric and deuteronitric acids as solvents

Abstract

DNO₃ is found to have a freezing-point of –42.07°C, only 0.46 K lower than that of HNO₃, and a molar enthalpy of fusion of 9917 ± 40 kJ mol^–1(2370 ± 10 kcal mol^–1), which is 5 % smaller than that of HNO₃. The curvature of the freezing-point against molality of D₂O (H₂O) curve shows, however, that the extents of self-dissociation of the two acids are very similar, the total molality of dissociation products being about 0.85 in each case. As expected, KNO₃ exhibits similar cryoscopic behaviour in the two solvents. Some results for other solutes in HNO₃ are also reported: H₂SO₄ probably yields NO⁺₂+ HSO^–₄+ H₂O, while CH₃COOH behaves as a non-electrolyte.