Miscibility Gap in the System Cesium Amide/Ammonia,CsNH2/NH3 — Thermodynamic Investigations

The system CsNH₂/NH₃ is investigated between —50 °C and 120 °C: Partial pressures of ammonia, DTA and density measurements are given as a function of concentration and temperature. Thermodynamic interpretations of the data show that the solutions deviate strongly from the behaviour of ideal mixtures. A monoammoniate of CsNH₂ is stable up to 17 °C. Dilute solutions (≤ 30 mole % CsNH₂) have a miscibility gap above 79 ± 5 °C with an almost colourless solution of lower density clearly separated from a yellow one. Phase separation is discussed on the basis of hydrogen bonds between NH ions as acceptors and NH₃ molecules both solvating cesium ions.