Miscibility Gap in the System Cesium Amide/Ammonia, CsNH 2 /NH 3 — Thermodynamic Investigations

The system CsNH 2 /NH 3 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 CsNH 2 is stable up to 17 °C. Dilute solutions (≤ 30 mole % CsNH 2 ) 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   2 —ions as acceptors and NH 3 molecules both solvating cesium ions.