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.