A calorimetric investigation of the low-temperature phase transition in sodium hydroxide-d.

Abstract

The heat capacity of NaOD from 20 to 350 K is reported. An anomaly centered at 153.2 ± 0.1 K (?H = 131.1 ± 0.7 J/mol, ?S = 0.864 ± 0.005 J/K.mol) corresponds to the onset of a low-temp. antiferroelec. phase. This transformation, which likely involves tunneling of the deuterons, does not appear to have an atm. pressure analog in NaOH above 6 K.