Viscosity and Molar Volume of Potassium Thiocyanate + Sodium Thiocyanate + Acetamide Melt Systems

Kalita, Gautam; Rohman, Nashiour; Mahiuddin, Sekh

doi:10.1021/je970117b

Cited by 15 publications

(20 citation statements)

References 11 publications

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“…From Figure 2 it is apparent that the conductivity iso-therms showed significant negative deviation (∼11-15%) and may be considered as the onset of the mixed anion effect, whereas viscosity isotherms (Figure 3) do not show any detectable mixed anion effect as lithium nitrate is progressively replaced by lithium bromide. In our earlier mixed Na/K thiocyanates in acetamide medium (Mahiuddin, 1996;Kalita et al, 1998c) we reported both positive (∼4.6% in K + rich region) and negative (∼27% in Na + rich region) deviations in electrical conductivity isotherms and ∼27-55% negative deviation in the viscosity isotherms. Plowiec et al (1985) reported that Na + in acetamide melt medium form a polymeric type solvated ion.…”

Section: Resultsmentioning

confidence: 69%

Electrical Conductivity, Viscosity, and Sound Velocity of Lithium Bromide + Lithium Nitrate + Acetamide Melt Systems

1999

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Densities, electrical conductivities, viscosities, and sound velocities of 0.22[xLiBr + (1x)LiNO 3 ] + 0.78CH 3 CONH 2 were measured as functions of temperature (296.75 e T/K e 343.15) and composition (x ) 0.0-1.0 mole fraction). Electrical conductivity, viscosity, and structural relaxation time were found to have non-Arrhenius temperature dependence and were analyzed by using the Vogel-Tamman-Fulcher equation. A significant mixed anion effect has been found in the electrical conductivity isotherms. Viscosity and structural relaxation time vary linearly with composition. The variation of electrical conductivity is governed by the mobility of Brand NO 3ions and the competitive polarization exerted by anions on Li + , whereas the polymeric and rigid structure formed between Li + and acetamide primarily govern the viscosity process.

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Section: Resultsmentioning

confidence: 69%

Electrical Conductivity, Viscosity, and Sound Velocity of Lithium Bromide + Lithium Nitrate + Acetamide Melt Systems

1999

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“…These interesting solvent properties coupled with a wide thermal window have made molten mixtures of (acetamide + electrolyte) to be used not only as reaction media in chemical industry but also as materials for electrochemical applications at elevated temperatures. 20,21 These molten mixtures (or simply, melts) are characterized by estimated glass transition temperatures (T g ) ∼190 < T g /K < 250 range, [22][23][24][25] and are termed as supercooled mixtures as they remain in the liquid phase at temperatures much below the respective melting temperatures of the constituents. This "supercooling" phenomenon and the associated importance for chemical industry have motivated much of the research on the basic scientific aspects, because developing these melts into useful dielectric materials 13,26 requires deeper understanding of medium structural and transport properties.…”

Section: Introductionmentioning

confidence: 99%

Medium decoupling of dynamics at temperatures ∼100 K above glass-transition temperature: A case study with (acetamide + lithium bromide/nitrate) melts

Guchhait

Daschakraborty

Biswas

2012

The Journal of Chemical Physics

126

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Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in [0.78CH(3)CONH(2) + 0.22{f LiBr + (1-f) LiNO(3)}] melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ∼50-100 K above the glass transition temperatures of the above melt at various anion concentrations (f(LiBr)). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times (<τ(s)> and <τ(r)>, respectively): <τ(x)> ∝ (η∕T)(p) (x being solvation or rotation), with p covering the range, 0.20 < p < 0.70. Although this is very similar to what is known for deeply supercooled liquids, it is very surprising because of the temperature range at which the above decoupling occurs for these molten mixtures. The kinship to the supercooled liquids is further exhibited via p which is always larger for <τ(r)> than for <τ(s)>, indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 < Δν(t)/cm(-1) < 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated.

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“…The choice of this system is further motivated by the fact that density and viscosity of this mixture as a function of KSCN fraction have already been studied for a reasonably large temperature range. 44 These studies have revealed significant MAE for the composition dependent viscosity where a Vogel-Fulcher-Tammann (VFT) type of description has been found to be suitable for the temperature dependence of viscosity in these mixtures. 44 For the sake of completeness, we present in Figure S1 (Supporting Information) a plot of solution viscosity as a function of KSCN concentration, measured at ∼318 K. 44 Note also that the molten mixtures at six different fractions of KSCN considered here at 318 K are always in the liquid phase and far away from the respective glass transition temperatures.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Spectroscopic Studies of (Acetamide + Sodium/Potassium Thiocyanates) Molten Mixtures: Composition and Temperature Dependence

et al. 2010

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Steady state and time-resolved fluorescence spectroscopic techniques have been used to explore the Stokes' shift dynamics and rotational relaxation of a dipolar solute probe in molten mixtures of acetamide (CH(3)CONH(2)) with sodium and potassium thiocyanates (Na /KSCN) at T approximately 318 K and several other higher temperatures. The dipolar solute probe employed for this study is coumarin 153 (C153). Six different fractions (f) of KSCN of the following ternary mixture composition, 0.75 CH(3)CONH(2) + 0.25[(1 - f)NaSCN + fKSCN], have been considered. The estimated experimental dynamic Stokes' shift for these systems ranges between 1800 and 2200 cm(-1) (+/-250 cm(-1)), which is similar to what has been observed with the same solute probe in several imidazolium cation based room temperature ionic liquids (RTIL) and in pure amide solvents. Interestingly, this range of estimated Stokes' shift, even though not corresponding to the megavalue of static dielectric constant reported in the literature for a binary mixture of molten CH(3)CONH(2) and NaSCN, exhibits a nonmonotonic KSCN concentration dependence. The magnitudes of the dynamic Stokes' shift detected in the present experiments are significantly less than the estimated ones, as nearly 40-60% of the total shift is missed due to the limited time resolution employed (full-width at half-maximum of the instrument response function approximately 70 ps). The solvation response function, constructed from the detected shifts in these systems, exhibits triexponential decay with the fastest time constant (tau(1)) in the 10-20 ps range, which might be much shorter if measured with a better time resolution. The second time constant (tau(2)) lies in the 70-100 ps range, and the third one (tau(3)) ranges between 300 and 800 ps. Both these time constants (tau(2) and tau(3)) show alkali metal ion concentration dependence and exhibit viscosity decoupling at higher viscosity in the NaSCN-enriched region. Time dependent rotational anisotropy has been found to be biexponential at all mixture compositions studied. Both the average solvation () and rotation () times of C153 in these mixtures exhibit fractional power law dependence on medium viscosity ( is proportional to eta(p), x being solvation or rotation). For solvation, p is found to be 0.46, which is very different from that obtained for common polar and nonpolar solvents, and RTILs (p approximately = 1). For rotation, p approximately = 0.65, which is again different from the value (p approximately = 1) obtained for common polar solvents and RTILs but very similar to that (p approximately = 0.6) found for nonpolar solvents. In addition, experimentally measured average rotation times in these mixtures are found to exhibit slip behavior in the low eta/T region, which gradually transforms to subslip as eta/T increases. Calculations using a recently developed semimolecular theory predict a total dynamic Stokes' shift for C153 (dipolar solute) in these molten mixtures near approximately 1600 cm(-1) where the...

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Viscosity and Molar Volume of Potassium Thiocyanate + Sodium Thiocyanate + Acetamide Melt Systems

Cited by 15 publications

References 11 publications

Electrical Conductivity, Viscosity, and Sound Velocity of Lithium Bromide + Lithium Nitrate + Acetamide Melt Systems

Electrical Conductivity, Viscosity, and Sound Velocity of Lithium Bromide + Lithium Nitrate + Acetamide Melt Systems

Medium decoupling of dynamics at temperatures ∼100 K above glass-transition temperature: A case study with (acetamide + lithium bromide/nitrate) melts

Fluorescence Spectroscopic Studies of (Acetamide + Sodium/Potassium Thiocyanates) Molten Mixtures: Composition and Temperature Dependence

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