Temperature and Pressure Dependence of the Electrical Conductivity

Article pubs.acs.org/jced

Temperature and Pressure Dependence of the Electrical Conductivity of 1‑Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)amide Mitsuhiro Kanakubo,*,† Kenneth R. Harris,‡ Noriaki Tsuchihashi,§ Kazuyasu Ibuki,§,⊥ and Masakatsu Ueno§ †

National Institute of Industrial Science and Technology (AIST), 4-2-1 Nigatake, Miyagino-ku, Sendai 983-8551, Japan School of Physical, Environmental and Mathematical Sciences, University of New South Wales, P.O. Box 7916, Canberra BC, ACT 2610, Australia § Department of Molecular Science and Biochemistry, Faculty of Science and Engineering, Doshisha University, Kyo-Tanabe, Kyoto 610-0321, Japan ‡

S Supporting Information *

ABSTRACT: The electrical conductivities of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([BMIM][Tf2N]) have been determined between (273 and 353) K over an extended pressure range up to 250 MPa by both electrochemical impedance spectroscopy and conductance bridge techniques. The results obtained by the two techniques are generally in good agreement, within 3%, though the conductance bridge results yield lower values outside the experimental uncertainties at higher conductivities, that is, at higher temperature and lower pressures where the maximum deviation is −7%. The temperature and pressure dependence of both the conductivity and molar conductivity have been represented by modified Vogel−Fulcher−Tammann equations. The molar conductivity scales with the viscosity, with overlapping isobars and isotherms, so that a Walden plot, the logarithmic projection of molar conductivity versus fluidity (reciprocal viscosity), is a straight line with a similar slope (0.924) to those obtained for other 1,3-dialkylimidazolium ionic liquids.

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INTRODUCTION

published separately, together with high-pressure ion self-diffusion measurements. Recently, the densities of [BMIM][Tf2N] have been determined between (273 and 363) K over an extended pressure range up to 250 MPa by our group.14 This has allowed calculation of the molar conductivity from the present measurements of the electrical conductivity, and hence analysis in terms of viscosity (Walden) scaling. Electrical conductivities for [BMIM][Tf2N] at atmospheric pressure have been reported over a wide temperature range by a number of groups,13,15−23 and these are summarized in Table 1 together with the experimental conditions. It should be noted that the literature conductivities show a scatter of more than 50% (of our data values) at common temperatures. This discrepancy between measurement sets is much larger than that for the viscosity, suggesting that the conductivity results may well be affected by problems of choice of appropriate instrumentation and technique, not just the usual difficulties of sample purity due to water and halide residues. In our published studies of conductivity measurements for the 1,3-dialkylimidazolium hexafluorophosphates and tetrafluoroborates1−3 using a standard conductance bridge,

This paper reports high-pressure electrical conductivities for 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([BMIM][Tf2N]), CAS No. 174899-83-3) as a function of temperature, and compares two experimental techniques for such conductivity measurements. These methods employ a standard conductance bridge and electrochemical impedance spectroscopy (EIS). We have previously published high-pressure conductivities for 1,3-dialkylimidazolium hexafluorophosphates and tetrafluoroborates,1−3 using the conductance bridge technique, as part of a series of measurements of the high pressure transport properties of ionic liquids1−4 and atmospheric pressure measurements for several [Tf2N]− salts with complex cyclic cations5−9 or ammonium-based cations10 using the EIS technique. Highpressure electrical conductivities for ionic liquids (ILs) in the literature seem to be limited to those published by our group, other than the low temperature liquid studies of Paluch et al.11−13 directed at understanding the glass transition. Yet they are essential for the separation of the effects of temperature and density on this property, and for investigations of the relationships between ionic liquid transport properties. Such measurements are also of importance for the investigation of thermodynamic scaling of the transport properties and for viscosity scaling of derived quantities such as velocity cross-correlation coefficients (VCCs) and distinct diffusion coefficients.2−4 These calculations are to be © 2015 American Chemical Society

Received: January 21, 2015 Accepted: April 14, 2015 Published: April 28, 2015 1495

DOI: 10.1021/acs.jced.5b00071 J. Chem. Eng. Data 2015, 60, 1495−1503

Journal of Chemical & Engineering Data

Article

Table 1. Summary of the Electrical Conductivity Measurements for [BMIM][Tf2N]a conditions authors

ref

year

present study

present study Tokuda et al.

15

2004

Widegren et al.

16

2005

Jin et al.

17

2008

Andriola et al.

18

2010

Pan et al.

19

2011

Bulut et al. Rupp et al. Yu et al.

20 21 22

2011 2014 2012

Vranes et al.

23

2014

Wojnarowska et al.

13

2014

measurements

status of sample

T/K and p/MPa

technique, electrode, cell constant, fitting

company, purity, water content, halogen content

T: 273.15 to 353.15 (0.02 K) p: 0.1 to 250 (0.0175 MPa at 70 MPa) T: 273.15 to 353.15 (0.02 K) p: 0.1 to 200 (0.5 MPa) T: 263.15 to 373.15 (n.a.)b p: 0.1 T: 288.15 to 323.15 (n.a.)c p: 0.1 T: 295 (1 K) p: 0.1 T: 298 (n.a.) p: 0.1 T: 298.15 to 353.15 (0.05 K) p: 0.1 T: 298.2 to 343.2 (0.1 K) p: 0.1 T: 293.15 to 353.15 (n/a) p: 0.1 T: 293.15 to 323.15 (0.01 K) p: 0.1 T: 182.15 to 233.15 (0.1 K) p: 0.1 to 460 MPa (0.1 MPa)

impedance (0.1 Hz to 1 MHz), bright Pt, 0.321 and 0.368 cm−1, Nyquist plot

synthesized, > 99 %, < 20 ppm, AgNO3 testing

bridge (0.5 to 5 kHz), bright Pt, 0.320, 0.345, and 0.475 cm−1, R vs 1/f 2

synthesized, > 99 %, < 20 ppm, AgNO3 testing

impedance (5 Hz to 13 MHz), platinized Pt, 1 cm−1, n.a.

synthesized, n.a., < 40 ppm, AgNO3 testing

bridge (0.8 to 5 kHz), platinum black, 0.999 cm−1, R vs 1/f 0.5 or 1/f

commercial, > 99.5 %, 10 to 8850 ppm, AgNO3 testing and Cl-selective electrode

impedance (5 Hz to 10 MHz), n.a., n.a., n.a.

Covalent Associates, > 99.5%, 32 ppm, n.a.

conductivity meter (fixed at 3 kHz), Pt plates, 1 cm−1, −

EMD Chemicals Inc., > 97 %, 0.0 to 0.5 v/v %, n.a.

LCR meter (100 Hz to 100 kHz), Pt flags, n.a., R vs 1/f 0.5

IoLiTec, 99 %, 1 ppm, n.a.

conductivity meter (fixed at 300 Hz or 2.4 kHz), n.a., n.a., −

synthesized, n.a., 14 and 410 ppm, AgNO3 testing

conductivity meter (fixed at 3 kHz), Pt, 1 cm−1, −

EMD Chemicals Inc., > 97 %, n.a., n.a.

conductivity meter, Pt, 1.03 cm−1, n.a

Merck, > 99 %, 100 ppm, n.a.

dielectric spectroscopy, stainless steel, n.a., n.a.

synthesized, > 99 %, 60 ppm, Br− 5 ppm, Li+ 0.8 ppm.

a c

Notation: n.a. = not available. b0.02 K between 283 and 313 and 0.3 K at the other temperatures, estimated from the water and air baths used. Note that the uncertainty in the bath temperature results in a relative standard uncertainty 333 K are off-scale due to large deviations beyond −50 %); ∗, ref 23 (100 ppm).

MVFT 1: κ , Λ(T , p) = exp[a′ + b′p + δ(p)T0/(T − T0)] with δ(p) = (c′ + d′p + e′p2 )/T0

(2)

MVFT 2: κ , Λ(T , p) = exp[a″ + b″p + δT0(p)/(T − T0(p))] with T0(p) = x + yp + zp2

impedance and bridge measurements, the VFT equation reproduces the temperature dependence of κ very well within 2% over the entire temperature range. The relative deviations (experimental−impedance VFT values) of κ for [BMIM][Tf2N] in the conductance bridge measurements are also plotted in Figure 1(b) together with the literature conductivities. The conductivities from the bridge measurements decrease with increasing temperature, more than −5 % at temperatures higher than ∼320 K. This is attributed to the failure of the frequency dependence correction for the solution resistance mentioned above. This also appears to be the case for the literature conductivities from ref 18 and 20. The conductivities determined at fixed frequencies (3 kHz and 300 Hz/2.4 kHz) show markedly smaller values even though the water content of the sample is small (14 ppm to 400 ppm). The measurements of Vranes et al.,23 who employed a similar technique, agree well below 303 K, but trend lower at higher temperatures. Those of Yu et al.,22 calculated from their VFT fitting equation, appear to be at odds

(3)

The fits include both the high pressure isotherms and the atmospheric pressure isobar: fitted coefficients obtained by nonlinear regression are given in Table 5. δ is the so-called Angell strength parameter, generally represented by D (which is not used here as it is the IUPAC symbol for a self-diffusion coefficient, which we also measure).33 For MVFT1 δ is expressed as a function of p with T0 constant, whereas for MVFT2, T0 is expressed as a function of p with δ constant. The qualities of the fits for the MVFT1 equations with the standard uncertainty σ = 0.54 % to 0.61 % are slightly better both for κ and Λ than the MVFT2 equations σ ≈ 0.72 %. Figure 3 shows the deviation plots (experimental − calculated values) for the fits of the MVFT1 (a) and MVFT2 (b) equations for the high-pressure Λ as a function of pressure at different temperatures. The MVFT1 equation reproduces the experimental data within 1 % with having more randomly distributed residuals, whereas the MVFT2 equation fits within 1.5 %, except for a single data point at 250 MPa and 323 K. 1498



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Table 4. Electrical Conductivity κ and Molar Conductivity Λ of [BMIM][Tf2N] from T = (283.15 to 348.15) K and p = (0.1 to 250) MPaa sample C, impedance (Kcell = 0.3683 cm−1) T

p

ρ

κ

b

kg·m

−3

Λ −1

K

MPa

283.15 283.15 283.14 283.14 283.15 283.15 283.15 283.15 283.15 283.15 283.15 283.15 283.15 283.15 283.16 283.15 283.15 283.15

0.10 0.90 1.61 3.36 5.01 9.94 14.97 20.06 25.13 30.21 40.32 50.07 74.7 100.3 125.2 149.4 174.4 200.6

1451 1452 1452 1454 1455 1458 1462 1465 1468 1472 1478 1484 1497 1511 1522 1533 1544 1554

0.2072 0.2053 0.2039 0.1997 0.1955 0.1843 0.1734 0.1632 0.1537 0.1449 0.1287 0.1150 0.08709 0.06494 0.04886 0.03727 0.02812 0.02094

298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15

0.10 1.15 2.09 2.92 4.76 9.89 14.99 19.96 24.51 28.75 40.28 49.15 49.83 70.20 72.1 81.0 92.2 97.9 124.9 150.7 174.7 200.6

1437 1438 1438 1439 1440 1444 1448 1451 1454 1457 1464 1470 1470 1482 1483 1488 1494 1497 1510 1522 1532 1543

0.4025 0.3986 0.3946 0.3911 0.3847 0.3641 0.3453 0.3284 0.3134 0.3002 0.2676 0.2447 0.2433 0.2001 0.1951 0.1801 0.1612 0.1527 0.1173 0.09182 0.07318 0.05717

S·m

T −1

μS·m ·mol 2

K

59.89 59.30 58.87 57.61 56.35 53.00 49.77 46.72 43.91 41.29 36.51 32.50 24.39 18.03 13.46 10.19 7.640 5.650

323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15 323.15

117.5 116.3 115.1 348.15 114.0 348.16 112.0 348.15 105.8 348.15 100.0 348.15 94.92 348.15 90.40 348.15 86.40 348.15 76.63 348.15 69.82 348.15 69.39 348.15 56.62 348.15 55.16 348.15 50.75 348.15 45.25 348.15 42.79 348.14 32.56 348.15 25.30 348.15 20.03 348.15 15.54 348.15 sample D, bridge (Kcell = 0.3479 cm−1)

ρb

p MPa

kg·m

κ −3

S·m

Λ −1

μS·m ·mol−1 2

0.10 1.08 2.02 3.10 5.08 10.07 15.04 20.04 24.99 30.09 40.04 49.97 75.2 100.0 124.8 150.9 175.1 201.3 225.2 250.8

1413 1414 1414 1415 1417 1421 1425 1428 1432 1435 1442 1449 1464 1478 1491 1503 1514 1525 1534 1544

0.9082 0.9005 0.8925 0.8850 0.8714 0.8350 0.8018 0.7689 0.7391 0.7086 0.6535 0.6043 0.4970 0.4100 0.3393 0.2785 0.2325 0.1919 0.1608 0.1332

269.6 267.1 264.6 262.2 257.9 246.5 236.1 225.8 216.5 207.0 190.0 174.9 142.3 116.3 95.46 77.70 64.41 52.77 43.97 36.20

0.10 1.08 1.75 3.12 5.03 9.86 15.09 19.94 25.38 30.09 39.78 49.82 74.9 100.5 125.1 150.6 175.1 200.7 225.5 250.3

1389 1390 1391 1392 1394 1398 1402 1406 1410 1414 1421 1428 1444 1459 1472 1485 1496 1507 1518 1527

1.620 1.611 1.599 1.585 1.564 1.512 1.460 1.411 1.358 1.314 1.233 1.152 0.9792 0.8301 0.7104 0.6048 0.5234 0.4490 0.3874 0.3344

488.9 486.1 482.3 477.6 470.8 453.8 436.6 420.9 403.9 389.8 364.0 338.3 284.4 238.6 202.3 170.8 146.7 124.9 107.1 91.84

T

p

ρb

κ

Λ

K

MPa

kg·m−3

S·m−1

μS·m2·mol−1

298.17 298.13 298.13 298.18 298.15 298.15 298.17 298.16 298.15

0.1 24.5 49.0 73.5 98.1 122.3 147.1 171.6 196.1

1437 1454 1470 1484 1497 1509 1520 1531 1541

0.3872 0.3029 0.2402 0.1898 0.1501 0.1195 0.09552 0.07580 0.06027

113.0 87.36 68.54 53.65 42.05 33.21 26.35 20.76 16.40

323.14 323.13

0.1 24.5

1413 1432

0.8126 0.6853

241.2 200.8

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Table 4. continued sample D, bridge (Kcell = 0.3479 cm−1)

a

T

p

ρb

κ

Λ

K

MPa

kg·m−3

S·m−1

μS·m2·mol−1

323.14 323.14 323.16 323.17 323.13 323.14 323.16

48.7 73.8 98.1 122.6 147.1 171.6 196.1

1448 1463 1477 1490 1501 1512 1523

0.5770 0.4797 0.4019 0.3350 0.2815 0.2360 0.1979

167.1 137.5 114.1 94.32 78.64 65.45 54.50

348.14 348.16 348.13 348.14 348.15 348.16 348.14 348.17 348.17

0.1 24.5 49.0 73.5 98.1 122.6 147.1 171.9 196.1

1389 1410 1427 1443 1458 1471 1483 1495 1506

1.3873 1.1927 1.0378 0.8979 0.7803 0.6748 0.5901 0.5128 0.4453

418.8 354.9 304.9 260.9 224.5 192.4 166.8 143.9 124.0

u(T) = 0.01 K, u(p) = 0.0175 MPa at p ≤ 70 and 0.4 MPa at 70 MPa < p, u(κ), u(Λ) = 2 %. bCalculated based on the Tait equation in ref 14.

Table 5. Coefficients of the Best Fits for eqs 2 and 3 for the Impedance Measurements with Standard Errors in Parenthesesa κ/S m−1

Λ/μS m2 mol−1

MVFT1, eq 2 a′ b′/10−3 MPa−1 c′/K d′/K MPa−1 e′/10−5 K MPa−2 T0/K σb/% a″ b″/10−3 MPa−1 δ x/K y/10−2 K MPa−1 z/10−5 K MPa−2 σb/%

Figure 2. Pressure dependence of the electrical conductivities κ for [BMIM][Tf2N] at different temperatures determined by the EIS (filled) and conductance bridge (open) measurements for sample “A”.

Similar deviation plots are shown for the conductivities κ in Supporting Information, Figure S3. For ILs, we have found that the fractional form of the Walden relation between the molar conductivity (Λ) and the fluidity, that is, the reciprocal of viscosity (1/η), gives a straight line:4

⎛ 1 ⎞t Λ∝⎜ ⎟ ⎝η⎠

3.859 (0.020) 1.748 (0.062) −580.4 (5.3) −1.466 (0.013) 33.49 (1.86) 176.30 (0.59) 0.54 MVFT2, eq 3 4.136 (0.027) −2.131 (0.060) −3.898 (0.065) 168.27 (0.81) 11.326 (0.073) −9.935 (0.248) 0.72

9.718 (0.023) 1.406 (0.071) −615.1 (6.3) −1.517 (0.016) 43.53 (2.13) 173.80 (0.67) 0.61 9.973 (0.028) −2.476 (0.060) −4.120 (0.069) 166.50 (0.82) 11.227 (0.072) −10.409 (0.243) 0.72

a

The standard errors are given in parentheses. bStandard uncertainty of fit.

maximum change of + 0.7 % at 299 MPa. Revised values of MVFT1 and MVFT2 coefficients are given in Table 6.) As is seen from the deviation plots (experimental − calculated values) for ln(Λ) versus ln(1/η) in Supporting Information, Figure S4, except for a few data points at 150 MPa ≤ p and 283 K, all the data points lie on the straight line within 3 %. The value of the exponent t = 0.924 ± 0.002 obtained, which is independent of temperature and pressure, is slightly larger than those for [BMIM]+ salts with other anions, [BMIM][BF4] (t = 0.878) and for [BMIM][PF6] (t = 0.913). The conductivity exponent t is very close to that for Stokes−Einstein−Sutherland plots for ion self-diffusion coefficients, 0.925 (cation) and 0.933 (anion), (given in a preliminary report:4 note that the value of t(Λ) given in that paper was based on conductivity bridge measurements alone).

(4)

with t ≤ 1. For each IL, the data for high-pressure isotherms and atmospheric-pressure isobar scale onto single lines. This is also the case for the present [BMIM][Tf2N], as shown in Figure 4, where the smoothed Λ calculated by eqs 2 and 4 for the atmospheric pressure isobar and the high-pressure isotherms are plotted against the smoothed fluidity (1/η) computed in a similar manner.4,29 (The buoyancy correction for the viscosities has been revised using the new pVT data: the only significant change, greater than + 0.4 %, is at 75 °C above 225 MPa, with a 1500



Article

Figure 4. Plot of ln(Λ) against ln(1/η) for [BMIM][Tf2N] for the high-pressure isotherms at 283 (◇), 298 (○), 323 (△), and 348 (□) K and for the atmospheric pressure isobar (×). The solid line represents the linear least-squares fit: ln[Λ/(μS·m2·mol−1)] = 0.924 ln[(1/η)/(Pa−1·s−1)] − 2.0167.

obtained by the two techniques are in good agreement within 2 % except at high temperatures and low pressures. The discrepancy results from the difficulty of correctly estimating infinite frequency resistance in conductance bridge measurements at low resistances (higher conductivities) due to the marked frequency dependence. The temperature and pressure dependence of the conductivities can be reproduced by modified Vogel−Fulcher−Tammann (VFT) equations. The molar conductivity scales with the viscosity, with overlapping isobars and isotherms, so that a Walden plot is a straight line with a slope (0.924 ± 0.002) similar to that obtained for other 1,3-dialkylimidazolium ionic liquids.

Figure 3. Relative deviations (experimental − calculated values) for the fits of MVFT1 (a) and MVFT2 (b) equations for the high-pressure molar conductivities Λ for [BMIM][Tf2N] as a function of pressure at 283 (diamonds), 298 (circles), 323 (triangles), and 348 (squares) K determined by the EIS measurements for sample “A”. The open symbols refer to the conductance bridge results. The dotted lines represent the standard uncertainties of the fits.

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ASSOCIATED CONTENT

S Supporting Information *

Frequency dependence of the solution resistance R as a function of (a) 1/√f, (b) 1/f, and (c) 1/f 2 in the conductance bridge measurements (Figure S1). Nyquist plots for the EIS measurements for [BMIM][Tf2N] under different conditions: (a) for a wide range of frequency and (b) at higher frequency (Figure S2); relative deviations (experimental − calculated values) for the fits of MVFT1 and MVFT2 equations for the high-pressure molar conductivities Λ for [BMIM][Tf2N] as a function of pressure at (283, 298, 323, and 348) K determined by the EIS measurements (Figure S3); relative deviations (experimental − calculated values) for the plot of ln(Λ) against ln(1/η) for [BMIM][Tf2N] as a function of pressure at (283, 298, 323, and 348) K and for the atmospheric pressure isobar (Figure S4). This material is available free of charge via the Internet at http://pubs.acs.org.

This suggests that the so-called deviation parameter (Δ) in the modified Nernst−Einstein equation is insensitive to temperature and pressure under the conditions studied, as is the case for other 1-alkyl-3-methylimidazolium salts.1−4 This point will be discussed further in a subsequent paper reporting ionic selfdiffusion measurements for [BMIM][Tf2N], together with an analysis of velocity cross-correlation coefficients.

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CONCLUSIONS The electrical conductivities of the ionic liquid 1-butyl-3methylimidazolium bis(trifluoromethanesulfonyl)amide are reported between (273 and 353) K over an extended pressure range up to 250 MPa from electrochemical impedance spectroscopy and conductance bridge techniques. The results

Table 6. Coefficients of the Best Fits for the Viscosity Analogues of eqs 2 and 3 for the Revised Viscosity Data of ref 29a MVFT1, eq 2 a′ b′/10−3 MPa−1 c′/K d′/K·MPa−1 e′/10−4 K·MPa−2 T0/K σb/% a

MVFT2, eq 3 a″ b″/10−3 MPa−1 δ x/K y/10−2 K·MPa−1 z/10−5 K·MPa−2 σb/%

1.7706 (0.034) −0.8923 (0.090) 755.14 (9.6) 1.6899 (0.017) −7.398 (0.23) 165.715 (0.88) 0.78

1.9234 (0.050) 2.7632 (0.086) 4.9551 (0.13) 161.545 (1.3) 11.139 (0.12) −11.037 (0.26) 0.98

The standard errors are given in parentheses. bStandard uncertainty of fit. 1501



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Article

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Corresponding Author

*E-mail: [email protected]. Fax: +81-22-232-7002. Funding

K.R.H. gratefully acknowledges the receipt of a short-term fellowship at AIST from the Japan Society for the Promotion of Science in 2007 and a travel grant from the (Australian) Prime Minister’s Education Assistance Program for Japan, in response to the Great East Japan Earthquake on 11 March 2011, in 2012, in support of this research. Notes

The authors declare no competing financial interest. ⊥ Deceased. Professor Ibuki passed away in May 2012.

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ACKNOWLEDGMENTS It is a pleasure to thank Dr. Lawrie Woolf (UNSW Canberra) for his helpful discussions regarding this project and Ms. Eriko Niitsuma (AIST Sendai) for her careful assistance with the measurements.

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REFERENCES

(1) Kanakubo, M.; Harris, K. R.; Tsuchihashi, N.; Ibuki, K.; Ueno, M. Temperature and Pressure Dependence of the Electrical Conductivity of the Ionic Liquids 1-Methyl-3-octylimidazolium Hexafluorophosphate and 1-Methyl-3-Octylimidazolium Tetrafluoroborate. Fluid Phase Equilib. 2007, 261, 414−420. (2) Kanakubo, M.; Harris, K. R.; Tsuchihashi, N.; Ibuki, K.; Ueno, M. Effect of Pressure on Transport Properties of the Ionic Liquid 1-Butyl3-methylimidazolium Hexafluorophosphate. J. Phys. Chem. B 2007, 111, 2062−2069 correction, 2007, 111, 13867. (3) Harris, K. R.; Kanakubo, M.; Tsuchihashi, N.; Ibuki, K.; Ueno, M. Effect of Pressure on the Transport Properties of Ionic liquids: 1Alkyl-3-methylimidazolium salts. J. Phys. Chem. B 2008, 112, 9830− 9840. (4) Harris, K. R.; Kanakubo, M. High Pressure Studies of the Transport Properties of Ionic Liquids. Faraday Discuss. 2012, 154, 425−438. (5) Kanakubo, M.; Nanjo, H.; Nishida, T.; Takano, J. Density, Viscosity, and Electrical Conductivity of N-Methoxymethyl-Nmethylpyrrolidinium Bis(trifluoromethanesulfonyl)amide. Fluid Phase Equilib. 2011, 302, 10−13. (6) Harris, K. R.; Woolf, L. A.; Kanakubo, M.; Rüther, T. Transport Properties of N-Butyl-N-methylpyrrolidinium Bis(trifluoromethylsulfonyl)amide. J. Chem. Eng. Data 2011, 56, 4672−4685. (7) Makino, T.; Kanakubo, M.; Umecky, T.; Suzuki, A.; Nishida, T.; Takano, J. Electrical Conductivities, Viscosities, and Densities of NMethoxymethyl- and N-Butyl-N-methylpyrrolidinium Ionic Liquids with the Bis(fluorosulfonyl)amide Anion. J. Chem. Eng. Data 2012, 57, 751−755. (8) Harris, K. R.; Horne, M. D.; Kanakubo, M.; Rodopoulos, T.; Rüther, T.; Veder, J.-P.; Woolf, L. A. Transport, Electrochemical and Thermophysical Properties of Two N-donor- Functionalised Ionic Liquids. Chem.Eur. J. 2013, 19, 17733−17744. (9) Makino, T.; Kanakubo, M.; Masuda, Y.; Umecky, T.; Suzuki, A. CO2 Absorption Properties, Densities, Viscosities, and Electrical Conductivities of Ethylimidazolium and 1-Ethyl-3-methylimidazolium Ionic Liquids. Fluid Phase Equilib. 2014, 362, 300−306. (10) Makino, T.; Kanakubo, M.; Umecky, T.; Suzuki, A. Electrical Conductivities, Viscosities, and Densities of N-Acetoxyethyl-N,Ndimethyl-N-ethylammonium and N,N-Dimethyl-N-ethyl-N-methoxyethoxyethylammonium Bis(trifluoromethanesulfonyl)amide and Their Nonfunctionalized Analogues. J. Chem. Eng. Data 2013, 58, 370−376. (11) Wojnarowska, Z.; Swiety-Pospiech, A.; Grzybowska, K.; Hawelek, L.; Paluch, M.; Ngai, K. L. Fundamentals of Ionic Conductivity Relaxation Gained from Study of Procaine Hydro1502



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(29) Harris, K. R.; Kanakubo, M.; Woolf, L. A. Temperature and Pressure Dependence of the Viscosity of the Ionic Liquids 1-Hexyl-3-methylimidazolium Hexafluorophosphate and 1-Butyl-3methylimidazolium Bis(trifluoromethylsulfonyl)imide. J. Chem. Eng. Data 2007, 52, 1080−1085. (30) Benson, G. C.; Gordon, A. R. A Reinvestigation of the Conductance of Aqueous Solutions of Potassium Chloride, Sodium Chloride, and Potassium Bromide at Temperatures from 15 to 45 °C. J. Chem. Phys. 1945, 13, 473−474. (31) Pratt, K. W.; Koch, W. F.; Wu, Y. C.; Berezansky, P. A. MolalityBased Primary Standards of Electrolytic Conductivity. Pure Appl. Chem. 2001, 73, 1783−1793. (32) It is possible to use the same equations to represent both κ and Λ for convenience, despite the logical inconsistency, as ln c is a very much weaker function of T (and p) than is either ln κ or ln Λ for [BMIM][Tf2N]. The form of the VFT equation is particularly flexible. (33) Angell, C. A. Perspective on the Glass Transition. J. Phys. Chem. Solids 1998, 49, 863−871.

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Temperature and Pressure Dependence of the Electrical Conductivity

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