The Vapor Pressure of Solutions of Potassium in Liquid Ammonia

Johnson, W. Curtis; Meyer, Albert W.

doi:10.1021/j150306a006

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“…Applying this procedure under conditions of equilibrium and controlled temperature, Kraus and Johnson (13) and Johnson (14), and Johnson and Meyer (15,16) have determined the composition of saturated solutions of lithium, sodium and potassium at several temperatures. These results are given in table 1, and are expressed in terms of gram-molecules of ammonia per gram-atom of metal.…”

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confidence: 99%

The Properties of Solutions of Metals in Liquid Ammonia.

Johnson¹,

Meyer²

1931

Chem. Rev.

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Liquid ammonia is an excellent solvent for a large number of different types of substances (1). Although it does not surpass water as a solvent for most inorganic substances, it appears to excel as a medium for organic compounds; in this it resembles alcohol. It exhibits a distinct advantage over water in that it dissolves the alkali and alkaline earth metals without appreciable reaction with them. The fact that reaction does not proceed is undoubtedly due to the extremely low concentration of the amide ions present in liquid ammonia. This condition is substantiated by the low conductivity of pure ammonia and also by the small tendency for ammonolytic reactions to proceed as compared to hydrolytic reactions in water. Substances which are readily hydrolyzed in water are, as a rule, not ammonolyzed in liquid ammonia. Thus it is possible to study the chemical and physical properties of the strongly electropositive elements in a comparatively inert medium possessing a high dielectric constant. In the present discussion we shall confine ourselves to the physical properties of these solutions and shall attempt to give a critical account of the results of the numerous investigations. SOLUBILITY RELATIONSSolutions of the alkali metals in liquid ammonia were first investigated by Weyl in 1864 (2). He observed that sodium and potassium were soluble in this medium, producing highly colored solutions. At the time of his studies the radical theory domi-

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confidence: 99%

The Properties of Solutions of Metals in Liquid Ammonia.

Johnson¹,

Meyer²

1931

Chem. Rev.

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Metal‐Ammonia Solutions

Jolly

1959

Progress in Inorganic Chemistry

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Thermodynamics of the Nonmetal‐Metal Transition of Sodium‐Ammonia Solutions

Schindewolf

Werner

1977

Ber Bunsenges Phys Chem

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Losunyeti 1 M i~~u l l cI Nic.litmetrrll-Metcill-Uheryany 1 Thermodynamik binarer SystemeMetal-ammonia solutions (MAS) pass with increasing metal concentration through a nonmetal-metal transition (NMT). Determination of the ammonia vapour pressure of sodium-ammonia solutions around -40°C and its temperature dependence and application of the Gibbs-Duhem equation lead to the chemical potentials and the partial molar enthalpies and entropies of both components. Whereas the chemical potentials are almost concentration independent in the concentration range of the NMT, the other partial molar quantities display pronounced extrema. The evaluation of the data leads to the conclusions. a) the N M T is accompanied by an increase of enthalpy and entropy of the dissolved metal. due to the transition of the electrons from the solvated to the free state; b) the N M T is favoured by temperature increase; c) the miscibility gap at lower concentrations is a consequence of the NMT. Introduction Metal-ammonia solutions (MAS) which contain dissolved or excess electrons behave at low metal concentrations (<0.5 mol percent metal (MPM)) like an electrolyte solution, whereas the high concentrated solutions ( > 10 MPM) display the characteristics of a liquid metal [l]. Somewhere in the intermediate concentration range the nonmetal-metal transition (NMT) occurs. An NMT has been observed also in other systems, e.g. in supercritical mercury by increasing the mass density [2] or in solid binary mixtures, e. g. tungsten bronzes [3] by changing the composition. Metall-Ammoniaklosungen (MAS) durchlaufen mit steigender Metallkonzentration einen Nichtmetall-Metalliibergang (NMTAlthough the NMT is of increasing interest, e.g. with respect to semiconductors, little is known about its thermodynamics. This should be mainly due to experimental difficulties because the thermodynamic measurements have to be done at high pressures and temperatures, as with supercritical mercury, or with solid multicomponent mixtures, as with tungsten bronzes which mostly are not in an equilibrium state. Only for MAS a few thermodynamic data have been published : precision vapour pressure measurements by Marshall [4] at only one temperature ( -35 "C) from which

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The Vapor Pressure of Solutions of Potassium in Liquid Ammonia

Cited by 11 publications

References 0 publications

The Properties of Solutions of Metals in Liquid Ammonia.

The Properties of Solutions of Metals in Liquid Ammonia.

Metal‐Ammonia Solutions

Thermodynamics of the Nonmetal‐Metal Transition of Sodium‐Ammonia Solutions

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