Thermodynamic properties of ammonium haloplatinates: II. Heat capacity and thermodynamic functions of deuterated ammonium hexachloroplatinate (ND 4) 2PtCl 6 at temperatures from 5 K to 350 K

Abstract

The heat capacity of deuterated ammonium hexachloroplatinate (ND 4 ) 2 PtCl 6 was measured at temperatures from 5 K to 350 K by adiabatic calorimetry. One λ-shaped anomaly, absent in the undeuterated salt, was found in the curve for heat capacity against temperature. This λ-shaped transition reaches its maximum C p,m ≈ 59.3· R at (27.2±0.05) K with Δ trs S o m = (1.216±0.004)· R , characteristic of an order-disorder transition. Smoothed values of the standard thermodynamic quantities for pure (ND 4 ) 2 PtCl 6 are tabulated at temperatures up to 350 K.