Heat capacity of some liquid Zintl compounds: Equiatomic alkali-lead alloys
Enthalpies for equiatomic APb (A = Na, Rb, and Cs) have been measured by high- temperature drop calorimetry over a temperature range covering solid and liquid phases.Thermodynamic information on the solid state transitions and the melting process is derived.With the exception of NaPb, the heat capacities of the liquid alloys show a remarkably strong negative temperature dependence above the melting point.It is suggested that this behavior is a consequence of the dissociation of molecular entities present in the liquid state related to the Zintl structures detected in the corresponding solid compounds.Thermodynamic calculations based on the presence of polyvalently charged anions yield valuable information on the temperature dependence of the concentration of these species.
Saboungi, Marie-Louise,Reijers, H. T. J.,Blander, M.,Johnson, G. K.
Experimental applicatios of sodium-containing alloys in molten alkali halides
Sodium-bismuth alloys were used as reference electrodes in contact with molten alkali halides to establish sodium activities. Electronic conductivity versus sodium activity was obtained for molten sodium halides using such alloys (~ 5 mol% Na) in polarization experiments. Results are presented for molten Nal. Also concentration versus activity data for Na in Na-Bi alloys were determined as uefunction of composition (xNa: 0.01-0.15) and temperature (700-900°C) by using a simple coulometric titration technique. Sodium-lead alloys (~8 mol% Na) were used to study the kinetics of the sodium electrode in molten NaCl using ac impedance spectroscopy combined with galvanostatic perturbation. Results from potential measurements between aluminium and a sodium ailoy electrode performed in cryolite-alumina melts to study the effects of electrolyte composition are also presented. WILEY-VCH Verlag GmbH, 1998.
Haarberg,Egan
p. 1298 - 1303
(2007/10/03)
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