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The effect of pressure on conductivities of molten dihalides and on EMF's of high-temperature galvanic cells

The effect of pressure on conductivities of molten dihalides and on EMF's of high-temperature galvanic cells
The effect of pressure on conductivities of molten dihalides and on EMF's of high-temperature galvanic cells

The electrical conductivities of molten SnX2 and CdX2 salts (X = Cl,Br,I) have been measured as a function of pressure to 100 MPa and at temperatures up to 160K above their normal freezing points. Activation energies Ev, Ep and activation volumes ΔV_Λ/ have been calculated and compared with results previously obtained for molten PbX_2, HgX_2 and alkali nitrate and alkali halide melts. The conductivities of SnX_2 melts decrease with increasing pressure. This behaviour, also obtained with PbX_2 and alkali metal salts, is characteristic of a `fully-ionized' melt. In contrast, the conductivities of the CdX_2 melts increase with pressure up to 100 MPa. This behaviour, also obtained with the HgX_2 melts, indicates a molecular or partially-ionized melt which undergoes self-ionization under pressure. The results for the SnX_2 and PbX_2 melts have been compared with the predictions of the Rice-Allnatt theory and the Transition State (Hole Model) theory of conductance in liquids. The results for CdX_2 melts were compared with predictions from the Born model for solvation of ions in a molecular melt. The EMF of high-temperature galvanic cells incorporating the solid sodium-conducting electrolyte β-alumina was examined to a pressure of 100 MPa maximum. The cells were: ominusNa(1)/β/Na(1)⊕ ominusNa(1)/β/NaCl,AlCl_3 (1)/Al_s ⊕ ominusNa(1)/β/Na(Hg)(1)⊕ p*>Latm. p=1 atmhskip 10mm p*hskip 17mm p*hskip 14mm p=1 atm. p*>latm.hskip 14 mm CELL 1hskip 20mm CELL2hskip 20mm CELL3hskip 13mm Results from cell 1 agreed well with calculated values from the molar volume of liquid sodium. Results from cell 2 were in modest agreement with calculated values. Here the positive electrode was a two-phase liquid system with the upper phase consisting of almost pure liquid AlCl3. Loss of this phase by evaporation was a major problem. Cell 3 consisted of sodium amalgam as the positive electrode, but faults with the experimental cell gave rise to poor results under pressure. The usefulness of all the above systems as a basis for high-temperature pressure measuring device has been assessed. (D71543/87)

University of Southampton
Kumar, Seppo Prem
Kumar, Seppo Prem

Kumar, Seppo Prem (1986) The effect of pressure on conductivities of molten dihalides and on EMF's of high-temperature galvanic cells. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The electrical conductivities of molten SnX2 and CdX2 salts (X = Cl,Br,I) have been measured as a function of pressure to 100 MPa and at temperatures up to 160K above their normal freezing points. Activation energies Ev, Ep and activation volumes ΔV_Λ/ have been calculated and compared with results previously obtained for molten PbX_2, HgX_2 and alkali nitrate and alkali halide melts. The conductivities of SnX_2 melts decrease with increasing pressure. This behaviour, also obtained with PbX_2 and alkali metal salts, is characteristic of a `fully-ionized' melt. In contrast, the conductivities of the CdX_2 melts increase with pressure up to 100 MPa. This behaviour, also obtained with the HgX_2 melts, indicates a molecular or partially-ionized melt which undergoes self-ionization under pressure. The results for the SnX_2 and PbX_2 melts have been compared with the predictions of the Rice-Allnatt theory and the Transition State (Hole Model) theory of conductance in liquids. The results for CdX_2 melts were compared with predictions from the Born model for solvation of ions in a molecular melt. The EMF of high-temperature galvanic cells incorporating the solid sodium-conducting electrolyte β-alumina was examined to a pressure of 100 MPa maximum. The cells were: ominusNa(1)/β/Na(1)⊕ ominusNa(1)/β/NaCl,AlCl_3 (1)/Al_s ⊕ ominusNa(1)/β/Na(Hg)(1)⊕ p*>Latm. p=1 atmhskip 10mm p*hskip 17mm p*hskip 14mm p=1 atm. p*>latm.hskip 14 mm CELL 1hskip 20mm CELL2hskip 20mm CELL3hskip 13mm Results from cell 1 agreed well with calculated values from the molar volume of liquid sodium. Results from cell 2 were in modest agreement with calculated values. Here the positive electrode was a two-phase liquid system with the upper phase consisting of almost pure liquid AlCl3. Loss of this phase by evaporation was a major problem. Cell 3 consisted of sodium amalgam as the positive electrode, but faults with the experimental cell gave rise to poor results under pressure. The usefulness of all the above systems as a basis for high-temperature pressure measuring device has been assessed. (D71543/87)

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Published date: 1986

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Local EPrints ID: 460708
URI: http://eprints.soton.ac.uk/id/eprint/460708
PURE UUID: b4e2d9a6-dcfd-4a79-bfe1-f84a6f76f202

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Date deposited: 04 Jul 2022 18:28
Last modified: 04 Jul 2022 18:28

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Author: Seppo Prem Kumar

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