scholarly journals Mixed alkali effect in sodium thiosulfate pentahydrate melt

1988 ◽  
Vol 66 (2) ◽  
pp. 242-245 ◽  
Author(s):  
Shakira S. Islam ◽  
Kochi Ismail
Keyword(s):  
Glass Transition ◽  
Sodium Thiosulfate ◽  
Electrical Conductance ◽  
Molar Conductance ◽  
Polarization Model ◽  
Density Data ◽  
Mixed Alkali ◽  
Mixed Alkali Effect ◽  
Arrhenius Temperature Dependence ◽  
Arrhenius Temperature

Density and electrical conductance measurements of 0.35[XNaNO3 + (1 − X)KNO3] + 0.65Na2S2O3•5H2O melt were made as functions of temperature and X. Molar volume, V, is found to be additive. The percent deviation of Vext (extrapolated V of the pure solute from the plot of V vs. total added alkali ion fraction) from Vcal (calculated V of the pure solute from its high temperature density data) increases monotonically as the amount of NaNO3 in the hydrate melt increases, thereby manifesting a "structure-forming" tendency of NaNO3. The non-Arrhenius temperature dependence of molar conductance, Λ is analyzed in terms of the Vogel–Tammann–Fulcher (VTF) equation. Mixed alkali effect (MAE) has been observed on Λ and T0 (ideal glass transition temperature). A competitive polarization model has been used to explain the MAE on Λ.

Electrical conductance of a mixture of sodium and potassium nitrates in aqueous medium

1990 ◽  
Vol 68 (11) ◽  
pp. 2115-2118 ◽  
Author(s):  
Ratan Lal Gupta ◽  
Kochi Ismail
Keyword(s):  
Aqueous Medium ◽  
Electrical Conductance ◽  
Potassium Nitrate ◽  
Molar Conductance ◽  
Size Parameter ◽  
Mixed Alkali ◽  
Mixed Alkali Effect ◽  
The Difference ◽  
Ion Size ◽  
Sodium And Potassium

Electrical conductance and density measurements of [xNaNO3 + (1 − x)KNO3] + RH2O system were taken as functions of x, R, and temperature. The mixed alkali effect on molar conductance (Λ) was found to be negligible upto R = 25 and becomes significant in the region where R < 25. It has been shown that for mixed electrolytic system in aqueous medium the concentration range at which the mixed alkali effect on Λ starts becoming significant can be predetermined by plotting the difference in Λ of the two pure electrolytic solutions versus R. The concentration dependence of Λ has been described satisfactorily by the expression Λ = ΛFLK exp (Bc + Cc2) where ΛFLK is the Falkenhagen–Leist–Kelbg equation for Λ, B and C are empirical constants, and c is the molar concentration. The observed values of the ion-size parameter have indicated more ionic association in KNO3 solution than in NaNO3 solution. Keywords: electrical conductance, sodium nitrate, potassium nitrate, mixed alkali effect.

Self-diffusion of Ag+ and Na+ in molten Ca(NO3)2-KNO3

1972 ◽  
Vol 25 (8) ◽  
pp. 1613 ◽  
Author(s):  
BJ Welch ◽  
CA Angell
Keyword(s):  
Electrical Conductance ◽  
Ionic Species ◽  
Tracer Diffusion ◽  
Dilute Solution ◽  
Self Diffusion ◽  
Capillary Method ◽  
Arrhenius Temperature Dependence ◽  
Radio Tracer ◽  
Tracer Diffusion Coefficients ◽  
Arrhenius Temperature

In order to explore the behaviour of diffusing ionic species in a molten salt in which non-Arrhenius behaviour of other transport properties is established, the diffusivities in dilute solution of Ag+ and Na+ in 38.1 mol% Ca(NO3)2+ 61.9 mol% KNO3 have been measured. For both ions limited radio-tracer diffusion coefficients, determined using a diffusion-out-of-capillary method, are reported. D(Ag+) has also been measured by chronopotentiometry, by which means the range and reliability of the measurements were considerably extended. Chronopotentiometric and tracer data agree within expected errors of measurement. Both ionic diffusivities show a non-Arrhenius temperature dependence which is indistinguishable in magnitude from that of the electrical conductance of the solvent melt.

scholarly journals The Electrical Conductivity of Some Hydrous and Anhydrous Molten Silicates as a Function of Temperature and Pressure

2021 ◽  
Author(s):  
◽  
John Satherley
Keyword(s):  
Electrical Conductivity ◽  
Quartz Crystal ◽  
Pressure Coefficient ◽  
General Picture ◽  
Water Composition ◽  
Mixed Alkali ◽  
Mixed Alkali Effect ◽  
Temperature And Pressure ◽  
Increasing Temperature ◽  
Arrhenius Temperature

<p>This thesis is concerned with the measurement and interpretation of electrical conductivity in molten silicates. Physicochemical properties and structural models of silica and silicates are reviewed first, to give a general picture of their behaviour. Electrical conductivity was measured as a function of temperature, pressure and water composition. To make these measurements an internally heated pressure vessel, designed to operate at temperatures up to 1200 degrees C and pressures up to 5 kbars was constructed. Conductivity measurements were made on the following anhydrous and hydrous silicate melts: SiO2/Na2O 60/40, 65/35, 75/25, 78/22 mol%; SiO2/Na2O/CaO 72/24/4 mol%; Mt. Erebus lava; SiO2/Na2O 78/22 mol% + ~5 wt% H2O and Mt. Erebus lava + ~4 wt% H2O in the temperature range 850-1000 degrees C and the pressure range 0-1.3 kbar. Arrhenius temperature and pressure dependencies on conductivity were observed. The pressure coefficient of conductivity was zero for the anhydrous melts well above Tg but small and positive for the hydrous silicates. Water caused ~40% reduction in conductivity when added to a melt which was accounted for in terms of the mixed alkali effect. Conductivity isobars for the hydrous silicates passed through a maximum as a function of increasing temperature. The conductivity behaviour as a function of temperature and pressure is analogous to that observed in partially ionised liquids and is intrepretated in an identical way. The range of operation of a piezoelectric alpha-quartz crystal viscometer was extended to allow measurement of viscosity as a function of temperature.</p>

Mixed alkali effect in 0.2[xKNO3 + (1 − x)NaNO3] + 0.8glycerol systems

1994 ◽  
Vol 72 (11) ◽  
pp. 2286-2290 ◽  
Author(s):  
Sekh Mahiuddin
Keyword(s):  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Mole Fraction ◽  
Linear Functions ◽  
Present System ◽  
Polarization Model ◽  
Mixed Alkali ◽  
Temperature Dependence Of Conductivity ◽  
Mixed Alkali Effect

Density, electrical conductivity, and fluidity of 0.2[xKNO3 + (1 − x)NaNO3] + 0.8glycerol systems were measured as functions of temperature (363.15 to428.15 K) and composition (0.0to 1.0 mole fraction). Densities were linear functions of temperature. The temperature dependence of conductivity and fluidity has been analysed by using the Vogel–Tammann–Fulcher (VTF) equation. Deviation from additivity has been observed in the electrical conductivity, fluidity isotherms to a lesser extent, and in electrical conductivity under isofluidity condition. The onset of the mixed alkali effect (MAE) in the present system has been explained by the anion polarization model.

scholarly journals The Electrical Conductivity of Some Hydrous and Anhydrous Molten Silicates as a Function of Temperature and Pressure

2021 ◽  
Author(s):  
◽  
John Satherley
Keyword(s):  
Electrical Conductivity ◽  
Quartz Crystal ◽  
Pressure Coefficient ◽  
General Picture ◽  
Water Composition ◽  
Mixed Alkali ◽  
Mixed Alkali Effect ◽  
Temperature And Pressure ◽  
Increasing Temperature ◽  
Arrhenius Temperature

<p>This thesis is concerned with the measurement and interpretation of electrical conductivity in molten silicates. Physicochemical properties and structural models of silica and silicates are reviewed first, to give a general picture of their behaviour. Electrical conductivity was measured as a function of temperature, pressure and water composition. To make these measurements an internally heated pressure vessel, designed to operate at temperatures up to 1200 degrees C and pressures up to 5 kbars was constructed. Conductivity measurements were made on the following anhydrous and hydrous silicate melts: SiO2/Na2O 60/40, 65/35, 75/25, 78/22 mol%; SiO2/Na2O/CaO 72/24/4 mol%; Mt. Erebus lava; SiO2/Na2O 78/22 mol% + ~5 wt% H2O and Mt. Erebus lava + ~4 wt% H2O in the temperature range 850-1000 degrees C and the pressure range 0-1.3 kbar. Arrhenius temperature and pressure dependencies on conductivity were observed. The pressure coefficient of conductivity was zero for the anhydrous melts well above Tg but small and positive for the hydrous silicates. Water caused ~40% reduction in conductivity when added to a melt which was accounted for in terms of the mixed alkali effect. Conductivity isobars for the hydrous silicates passed through a maximum as a function of increasing temperature. The conductivity behaviour as a function of temperature and pressure is analogous to that observed in partially ionised liquids and is intrepretated in an identical way. The range of operation of a piezoelectric alpha-quartz crystal viscometer was extended to allow measurement of viscosity as a function of temperature.</p>

ORIENTATIONAL GLASS TRANSITION AND STRUCTURAL RELAXATION IN SOLID C60

1993 ◽  
Vol 07 (27) ◽  
pp. 1703-1724 ◽  
Author(s):  
CHRISTOPH MEINGAST ◽  
FRANK GUGENBERGER
Keyword(s):  
Glass Transition ◽  
Temperature Dependence ◽  
Structural Relaxation ◽  
Structural Model ◽  
Local Environment ◽  
Small Deviations ◽  
Thermally Induced ◽  
Orientational Glass ◽  
Arrhenius Temperature Dependence ◽  
Arrhenius Temperature

We review recent experiments and models dealing with glass transition and the associated structural relaxation in solid C 60. This glass transition is thought to result from the freezing-in of thermally-induced dynamic orientational disorder in an otherwise orientationally-ordered crystalline structure. The structural relaxation is shown to be approximately exponential and linear (in the relaxation nomenclature), and the relaxation time nearly follows an Arrhenius temperature dependence over some 15 decades. C 60 is thus an example of an extremely ‘strong’ glass former in the ‘strong-fragile’ classification. The relaxation data are consistent with the simple structural model derived from X-ray and neutron diffraction, in which each C 60 molecule can be in two different, but energetically nearly equivalent (Δ≈10 meV ) orientational states, which are separated by an energy barrier of Ea≈250 meV . Small deviations from this simple picture are attributed to a slight temperature dependence of both Δ and Ea due to a changing local environment.

Equilibrium and transport properties of Ca(NO3)2 + (Li,K)NO3 hydrate melts: Confirmation of a mixed-alkali effect

1981 ◽  
Vol 34 (9) ◽  
pp. 1853 ◽  
Author(s):  
AJ Easteal
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Alkali Metal ◽  
Water Content ◽  
Metal Nitrate ◽  
Mixed Alkali ◽  
Metal Nitrates ◽  
Mixed Alkali Effect ◽  
Alkali Metal Nitrate

Glass-transition temperature, density, electrical conductivity and viscosity have been determined as a function of the relative proportions of the two alkali metal nitrates in the hydrate melts �������������� 0.55[Ca(NO3)2,RH2O]+0.45[XLiNO3+(1-X)KNO3] where X is the mole fraction of LiNO3 relative to total alkali metal nitrate, with mole ratios (R) of water to Ca(NO3)2 of 4.090 and 6.545, at 298.15 K. For both series of melts, molar volume varies linearly with X, i.e. is an additive function of composition. Glass-transition temperature and molar conductivity show negative deviations from additivity, the magnitude of the deviations decreasing with increased water content. Fluidity isotherms show much smaller negative deviations from additivity and the magnitude of the deviations is approximately independent of water content. ��� By analogy with the properties of network oxide melts and glasses, the composition variation of the properties investigated for the hydrate melts is interpreted as being indicative of a significant mixed-alkali effect qualitatively similar to the effect which occurs in network oxide media. The hydrate melts are closely similar in their behaviour to fused anhydrous (Na,Tl)NO3 mixtures, and it is suggested that the observed trends in the properties of the hydrate melts have a similar origin to that which was postulated for the anhydrous melts.

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