Thermodynamic properties and ordering in liquid NaK alloys |
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Authors: | Fred A Cafasso Vishwa M Khanna HM Feder |
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Institution: | 1. Argonne National Laboratory , Argonne, Illinois;2. Department of Chemistry , Rice University , Houston, Texas |
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Abstract: | The thermodynamic activities of sodium and potassium were determined by vapour-phase absorption spectrophotometry of atomic resonance lines. Both components exhibit significant positive deviations from ideality. Excess Gibbs energies computed from the activity data were combined with available heat-of-mixing data to yield values for excess entropies. The entropy of mixing which was found to be ideal in the sodium-rich liquid alloys provides no support for the earlier speculations about the existence of Na2K molecules therein. The partial molar excess entropy of sodium in dilute solution in potassium was found to be surprisingly large and negative for a system of this type. A plausible model, involving sodium-sodium pairing, is proposed to account for the loss of configurational entropy. |
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