Thermodynamic Properties of 1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone: Vapor Pressure, (p, ρ, T) Behavior, andSpeed of Sound Measurements, and an Equation of StateMark O. McLinden,* Richard A. Perkins, Eric W. Lemmon, and Tara J. Fortin

Applied Chemicals and Materials Division, National Institute of Standards and Technology, 325 Broadway, Mailstop 647.07, Boulder,Colorado 80305, United States

*S Supporting Information

ABSTRACT: We report comprehensive thermodynamic prop-erty measurements of 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoro-methyl)-3-pentanone. The (p, ρ, T) behavior was measuredfrom T = (225 to 470) K with pressures up to 36 MPa with atwo-sinker densimeter. These measurements include com-pressed-liquid states and states in the extended critical region.The vapor-phase speed of sound was measured from T = (325 to500) K with pressures up to 1.7 MPa with a spherical acousticresonator. The vapor pressure was measured in the sphericalresonator from T = (325 to 440) K with a static technique. Thedensity and speed of sound of the liquid was measured from T =(278 to 308) K at atmospheric pressure (p = 83 kPa) in abenchtop instrument employing a vibrating-U-tube densimeterand a time-of-flight speed-of-sound technique. These data, together with selected data from the fluid manufacturer, have beenused to develop an equation of state explicit in the Helmholtz energy covering the fluid region. The equation of state representsthe present experimental vapor-pressure data with an RMS deviation of 0.066 %, the (p, ρ, T) data to 0.067 %, and the speed-of-sound data to 0.029 %. This fluid is of interest as the working fluid in Rankine-cycle power applications and as a fire extinguishingagent; it is also known by the trade names Novec-649 and Novec-1230.

1. INTRODUCTION

The compound 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluorometh-yl)-3-pentanone (CAS registry number 756-13-8) is afluorinated ketone with the empirical formula C6F12O, structureCF3CF2C(O)CF(CF3)2, and a molar mass of (316.0444 ±0.0090) g·mol−1.1 A 3-D representation of the molecule isshown in Figure 1. This fluid is of interest as the working fluidin Organic-Rankine-Cycle (ORC) power applications and as a

fire extinguishing agent; it is also known as FK-5-1-12 and bythe trade names Novec-649 and Novec-1230. (Certain tradenames are identified only to adequately document theexperimental material. This does not constitute a recommen-dation or endorsement of these products by the NationalInstitute of Standards and Technology, nor does it imply thatthe products are necessarily the best available for the purpose.)(Novec-649 is used by the manufacturer for ORC applications,and Novec-1230 is used for fire-suppression applications; weuse “Novec-649” as a shorthand nomenclature throughout thispaper.) This fluid has a zero ozone-depletion potential (ODP)and a global warming potential (GWP) of one.2 The expectedatmospheric lifetime is reported to be 5 days (0.014 years).This fluid has been approved by the U.S. EnvironmentalProtection Agency as a total flooding agent for firesuppression.3

Special Issue: Memorial Issue in Honor of Anthony R. H. Goodwin

Received: July 20, 2015Accepted: September 14, 2015Published: September 30, 2015

Figure 1. 3-D representation of 1,1,1,2,2,4,5,5,5-nonafluoro-4-(tri-fluoromethyl)-3-pentanone (also known as Novec-649 and Novec-1230).

Article

pubs.acs.org/jced

This article not subject to U.S. Copyright.Published 2015 by the American ChemicalSociety

3646 DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

2. EXPERIMENTAL SECTION

2.1 . Exper imental Sample . The sample o f1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone(Novec-649) was analyzed by the supplier, 3M, and reported tohave a mole fraction purity of 0.998 with a nonvolatile residueof 1·10−6 mole fraction. Our own analysis by gas chromatog-raphy/mass spectrometry (carried out according to theprotocols of Bruno and Svoronos4) indicated a molar purityof 0.9995 with an identified impurity of 1,1,1,2,3,3,3-heptafluoropropane at a level of 0.0005 mole fraction. A KarlFischer titration indicated a water content of less than 25·10−6

mole fraction. For all measurements the sample was used asreceived, except that it was degassed with multiple cycles offreezing the sample, evacuating the vapor space, and thawing.The pressure over the frozen material on the final freeze−pump−thaw cycle was 5·10−3 Pa. This purity is summarized inTable 1 along with the purity of the argon sample used tocalibrate the diameter of the spherical resonator for the sound-speed measurements.2.2. Apparatus Description. Three separate experimental

instruments were utilized in the present work.2.2.1. Two-Sinker Densimeter with Magnetic Suspension

Coupling. The measurements utilized a two-sinker densimeterwith a magnetic suspension coupling. This type of instrumentapplies the Archimedes (buoyancy) principle to provide anabsolute determination of the density. This general type ofinstrument is described by Wagner and Kleinrahm,5 and ourinstrument is described in detail by McLinden and Losch-Will.6

Briefly, two sinkers of nearly the same mass and same surfacearea, but very different volumes, were each weighed with a high-precision balance while they were immersed in a fluid ofunknown density. The fluid density ρ is given by

ρ =− − −

−m m W W

V V( ) ( )

( )1 2 1 2

1 2 (1)

where m and V are the sinker mass and volume, W is thebalance reading, and the subscripts refer to the two sinkers.Each sinker had a mass of approximately 60 g; one was made oftantalum (V ≈ 3.6 cm3) and the other of titanium (V ≈ 13.3cm3). A magnetic suspension coupling transmitted the gravityand buoyancy forces on the sinkers to the balance, thusisolating the fluid sample from the balance. In comparison withother buoyancy techniques, the main advantage of the two-sinker method, as developed by Kleinrahm and Wagner,7 is thatsystematic errors in the weighing and from other sourcesapproximately cancel.In addition to the sinkers, two calibration masses (designated

mcal and mtare) were also weighed. This provided a calibration ofthe balance and also the information needed to correct formagnetic effects as described by McLinden et al.8 Theweighings yield a set of four equations that are solved toyield a balance calibration factor α and a parameter β related tothe balance tare (i.e., the magnets and other elements of the

system that are always weighed). This analysis yields the fluiddensity in terms of directly measured quantities:

ρ ρ=− −

− −−

αβ

αβ

−−

−−

⎡⎣⎢ ⎤⎦⎥⎡⎣⎢ ⎤⎦⎥

m m

V V

( )

( )

m W WW

V W WW

fluid

1 2( )

1 2( ) 0

1 1 2

1

1 1 2

1 (2)

where ρ0 is the indicated density when the sinkers are weighedin vacuum. In other words, ρ0 is an “apparatus zero.” Thedensity given by eq 2 compensates for the magnetic effects ofboth the apparatus and the fluid being measured. The efficiencyof the magnetic suspension coupling is characterized by a“coupling factor” ϕ; values of ϕ different than 1 indicate themagnitude of the force transmission error.8 For the presentmeasurements ϕ varied from 1.000 016 in vacuum to 0.999 934for the compressed-liquid measurements.The temperature was measured with a 25 Ω standard

platinum resistance thermometer (SPRT) and a resistancebridge referenced to a thermostated standard resistor. Pressureswere measured with one of three vibrating-quartz-crystal-typepressure transducers having full-scale pressure ranges of 2.8MPa, 13.8 MPa, or 69 MPa. The transducers and pressuremanifold were thermostated at T = 313.15 K to minimize theeffects of variations in laboratory temperature.

2.2.2. The Spherical Acoustic Resonator. The sphericalacoustic resonator is an accurate and reliable methodology forthe determination of the speed of sound in gases. Detaileddescriptions of the design and theory of spherical acousticresonators can be found in Moldover et al.9,10 and Trusler.11

The apparatus used in this work is described by Perkins andMcLinden.12 Only a brief summary is given here.The cell consisted of two flanged, stainless-steel hemispheres,

which were bolted together to form a spherical sample volumewith an internal diameter of 80 mm. It had a workingtemperature range of (265 to 500) K with pressures up to 40MPa. Sound transducer ports were located in the tophemisphere, with an angular separation of 90° to reduce theinterference between the (0, 2) and the (3, 1) modes. Asinusoidal excitation voltage was generated by a synthesizedfunction generator. Measured frequencies for the presentmeasurements were between (1191 and 4976) Hz for the (0,2) through (0, 4) radial modes.The working equation of a spherical resonator relates the

sound speed w to the sphere radius r and measured resonancefrequency f ln:

∑νπ

+ = + Δ +⎜ ⎟⎛⎝

⎞⎠f ig

wr

f ig2

( )ln ln lnj

j(3)

where gln is the half-power bandwidth, the subscript “ln” refersto the resonance mode (l, n), and the eigenvalues νln are the“turning points” (zeros of the first derivatives) of the sphericalBessel functions of order l. The summation accounts forcorrections to the ideal model; the main contributions to thisterm come from the effect of the thermal boundary layer, the

Table 1. Sample Information

chemical name source initial purity/mol fraction purification method final purity/mol fraction analysis method

Novec-649a 3M 0.9995b degassing 0.9995 GC−MSc

argon Matheson 0.999999 nonea1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone; also known as Novec-1230. bOrganic basis. cGas chromatography/massspectrometry.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3647

coupling between gas and shell motion, the fluid dissipation,and the presence of the filling tubes and the drive and detectortransducers. Small variations from a perfect sphere have a smalleffect on the measurements since only radially symmetricmodes were measured.10

The radius of the sphere was determined by measurementson high-purity argon (sample information in Table 1), asdescribed by Perkins and McLinden.12 For the measurementson Novec-649 these calibrations covered a temperature rangeof (320 to 500) K, with pressures to 10 MPa.The cell was thermostated by means of a multilayer, vacuum-

insulated thermostat. A copper sleeve surrounded the resonatorsphere to reduce temperature gradients; it also held eightcartridge-type electric heaters in drilled wells. An isothermalshield with additional heaters at the top and sides of the shieldand a fluid cooling channel at the top surrounded the coppersleeve; it was maintained at a temperature approximately 1 Kbelow the sphere temperature. The temperature of theresonator cell was measured with a 25 Ω SPRT inserted intoa thermowell in the flange of the sphere. Its resistance wasmeasured with an AC resistance bridge referenced to athermostated standard resistor. The temperature inside thesphere was constant within 5 mK.The pressure of the fluid was measured with one of three

vibrating-quartz-crystal-type transducers with full-scale pressureranges of (0.7, 6.2, and 41) MPa. The fluid sample was loadedinto the system by means of a manual, high-pressure, piston-type pump.2.2.3. Bench-Top Instrument for Liquid Density and Speed

of Sound at p = 83 kPa. A commercial density and sound-speed analyzer was used to simultaneously measure bothproperties at ambient pressure. The instrument contained twomeasurement cells in series: a time-of-flight sound-speed cellthat measured the propagation time of ∼3 MHz sound waves,and a vibrating-tube densimeter constructed of borosilicateglass. Both cells were housed in a thermostated copper block,the temperature of which was controlled with a combination ofthermoelectric Peltier elements and an integrated 100 Ωplatinum resistance thermometer. The operating temperaturerange of the instrument was (278 to 343) K, although the fullrange could not be utilized in this work due to the vaporpressure of the sample. Additional details about the density andsound-speed analyzer can be found in Laesecke et al.,13

Fortin,14 and Fortin et al.15

2.3. Measurement Procedures. 2.3.1. Vapor Pressure.Vapor pressures were measured by a static technique in thespherical-resonator apparatus. The measuring cell of theresonator was partially filled with liquid sample and thenthermostated at different temperatures in the range from (325to 420) K. The vapor pressure at each temperature wasobtained as the average of 5 to 11 replicate (T, p) valuesmeasured over the course of several minutes at steadyconditions. Vapor pressures were corrected for the hydrostatichead and for the zero drift of the pressure transducers. Vaporpressures were measured on two separate fillings of the sample.The initial filling mass was determined from the displacedsample volume of the piston pump and knowledge of thesample density at the temperature and pressure of the pump.After filling and before starting the vapor-pressure measure-ments, the vapor head space in the resonator cell was evacuatedseveral times for periods of (10 to 60) s to flush out any volatileimpurities that might have been present. The measuredpressure changed by less than 0.4 % following the evacuation

cycles, indicating that volatile impurities were present at a lowlevel.

2.3.2. (p, ρ, T) Behavior. Density data were measured withtwo separate fillings of the two-sinker densimeter. For the firstfilling, the densimeter cell was cooled to T = 217 K, and wasthen filled with liquid directly from the sample bottle. The cellwas then heated to T = 225 K; this generated a pressure of 6.3MPa and density of 1821 kg·m−3; following an equilibrationtime of 30 min, the first density point was measured. A portionof the sample was vented to p = 1.0 MPa at T = 225 K, and thenext density point was measured at ρ = 1810 kg·m−3. Themeasuring cell was heated in steps, and measurementscontinued along the pseudoisochore at ρ ≈ 1810 kg·m−3 upto T = 260 K and a pressure of 36 MPa. The sample was ventedin several steps along the isotherm at T = 260 K down to apressure of 1.1 MPa. Measurements along alternating pseudo-isochores and isotherms continued up to a maximumtemperature of 450 K, which was above the critical temperature.Three replicate density determinations were measured at eachstate point. A second filling followed a similar procedure exceptthat it started at T = 303 K and concluded at T = 470 K. Thisprocedure minimized the amount of sample required;furthermore, it did not require any pump and thus avoidedany chance for contamination that a pump or compressor mightintroduce.Between the two fillings, and also before and after all of the

Novec-649 testing, the densimeter cell was evacuated for aminimum of 36 h. This was done to clear the previouslymeasured sample and to check the ρ0 of the apparatus eq 2.The ρ0 varied by less than 0.0039 kg·m−3.

2.3.3. Vapor-Phase Sound Speed. Sound-speed measure-ments were carried out in the vapor phase along eightisotherms between (325 and 500) K, with pressures between(0.05 and 1.75) MPa. For each isotherm, fresh sample wasloaded into the spherical resonator by means of a manualpiston-type pump to a pressure of approximately 80 % of thevapor pressure at that temperature. The isotherm was thenmeasured at several pressure steps down to a minimumpressure of (50 to 90) kPa. The resonator was evacuatedbetween isotherms to ensure a completely fresh sample for thefollowing isotherm. The zero drift of the pressure transducerswas also checked during this evacuation, and no significantchanges were observed.After the sample was loaded, the system was allowed to come

to the set-point temperature and pressure; an additional 60 minwas allowed for complete equilibration before starting themeasurements. An initial frequency scan was carried out tolocate the resonance peaks; this procedure is detailed byPerkins and McLinden.12 The five radial modes from (0, 2)through (0, 6) were then scanned. Each scan consisted of 25measurements spanning a frequency range of approximately 1.5times the half-power bandwidth; a settling time of 2 s wasallowed between the measurements at each frequency. Eachmode was scanned twice, with increasing and decreasingfrequencies; this sequence required 20 min. The completesequence was repeated four times to yield a total of 40resonance scans at each (T, p) state point.The raw data from the frequency scans (as well as the

readings from the thermometers, pressure transducers, etc.)were stored to a file for off-line analysis. The calculated speedsof sound from the (0, 5) mode were consistently lower than theother modes, while those from the (0, 6) mode wereconsistently higher than the other modes. These differences

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3648

most likely were due to the influence of the shell resonance orof adjacent, nonradial modes distorting the resonance. Theresults from the (0, 5) and (0, 6) modes were thus droppedfrom further analysis. The corrections for the thermal boundarylayer required knowledge of the transport properties of Novec-649, and these were calculated with a predictive correspondingstates correlation developed by Huber,16 based on the liquidviscosity data of Fortin.17 A small correction due to theresonance of the spherical shell itself was also applied. The sumof these corrections was 0.0031 % or less.For selected state points at temperatures above 400 K,

multiple replicate scans were carried out over the course ofmany hours to check for possible sample degradation at hightemperatures, as discussed in section 3.3.2.3.4. Density and Speed of Sound of Liquid at p = 83

kPa. The vapor pressure of the liquid Novec-649 samplelimited the maximum liquid temperature that could bemeasured at the local atmospheric pressure of 83 kPa. In thisstudy, we found that limiting the maximum temperature to308.15 K reliably avoided bubble formation within the liquidsamples. During measurements, temperature scans wereperformed from the maximum temperature to 278.15 K indecrements of 5 K. A fresh aliquot of sample was injected priorto the start of each temperature scan; a total of seven scanswere performed. Prior to these measurements, the instrumentwas calibrated with air and deionized water. Measurements ontoluene and isooctane served to verify the calibration, and thesemeasurements were taken into consideration in the estimationof uncertainties.

3. RESULTSFigure 2 depicts the state points for the vapor pressures,densities, and sound speeds measured in this work. These data

are reported in Tables 2 to 6 and are described in the followingsections. The relative combined, expanded (k = 2) uncertainties(as discussed in section 3.5) are also given. The tables reportonly an average of the replicate points; data for all the replicatesare available in the Supporting Information. Comparisons ofthe experimental values from the values calculated from thenew equation of state are given in section 4.3.

3.1. Vapor Pressures. The vapor pressures reported in thiswork cover the temperature range from (325 to 420) K. Table2 presents these data together with their relative deviations withthe new equation of state, calculated as

χ χ

χΔ =

−χ

⎛⎝⎜⎜

⎞⎠⎟⎟100 exp EOS

EOS (4)

where χ represents a property (vapor pressure, density, orspeed of sound), and the subscript EOS represents the propertycalculated with the new equation of state. The data presentedare the values of 5 averaged vapor-pressure measurements foreach state point, where each individual vapor-pressuremeasurement was obtained as the average of 5 to 11 replicate(T, p) values measured over the course of several minutes atsteady conditions.

3.2. (p, ρ, T) Behavior. A total of 381 (p, ρ, T) data weremeasured in the temperature range from (225 to 470) K withpressures up to 36 MPa. A total of 321 densities were measuredin the compressed liquid phase (ρ > 1000 kg·m−3); additionaldata were measured along isotherms 8.2 K and 28.2 K abovethe critical temperature. Four replicates were measured at eachstate point. Table 3 reports the average values of the replicatesfor each state point together with their relative deviations indensity from the new equation of state. For the near-criticalpoints, deviations in pressure are reported in Table 4.To investigate the effects of possible sample degradation on

the measured density, the Novec-649 sample was held in themeasuring cell of the densimeter at T = 470 K, p = 2.80 MPa,

Figure 2. State points measured for Novec-649 in the present work: ∗,vapor pressure; □, (p, ρ, T) filling 1; △, (p, ρ, T) filling 2; ○, speed ofsound; ×, density and speed of sound at atmospheric pressure; #,critical point.

Table 2. Experimental Vapor Pressures psat for Novec-649from T = (325 to 420) K, Their Relative, CombinedExpanded (k = 2) Uncertainties, Uc, and Relative Deviationsof the Experimental Data from Values Calculated with theNew Equation of State Developed in This Work, Δp

a

T/K psat/kPa Uc/% Δp/%

Filling 1324.983 111.6 1.187 0.096349.990 242.7 0.538 0.047374.991 467.9 0.281 −0.002374.988 467.6 0.284 −0.051390.032 663.7 0.205 −0.066410.028 1014.3 0.144 −0.134Filling 2324.963 111.4 1.189 0.025324.963 111.4 1.197 −0.038324.969 111.4 1.205 −0.057324.970 111.3 1.213 −0.082339.950 180.3 0.741 −0.071354.978 278.7 0.477 −0.064370.002 413.4 0.323 −0.070400.012 826.0 0.169 0.085400.015 826.0 0.169 0.084400.012 826.0 0.169 0.085410.021 1016.0 0.142 0.052420.016 1238.2 0.122 0.010420.019 1238.3 0.122 0.011420.019 1238.3 0.122 0.012

aTemperatures were measured on ITS-90, and the standarduncertainty in temperature was 20 mK. Data are listed in the ordermeasured. Values averaged over 5 replicates are given here for eachtemperature T; see Supporting Information for all data.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3649

ρ = 560 kg·m−3 for 9 h. Repeated measurements showed asystematic increase of 0.0021 % in the density over this time;this change is only slightly greater than the repeatability of thedensimeter. The conclusion is that the measured densities werenot significantly affected by sample degradation. Analogoustests in the spherical resonator, however, did show an effect, asdiscussed in section 3.3.3.3. Sound Speed of Vapor. Speed-of-sound data were

measured in the gas phase over the temperature range from

(325 to 500) K, with pressures up to 1.75 MPa. Sound-speeddata for each state point were measured for the first five radialmodes (0, 2) to (0, 6), but as noted in section 2.3.3, the (0, 5)and (0, 6) modes were not used in the analysis.The measured sound speed was found to increase with

sample residence time. The increase in sound speed becamemore apparent at temperatures above 400 K and at pressuresbelow 500 kPa (see Figure S1 available in the SupportingInformation). This was likely due to sample degradation since

Table 3. Experimental (p, ρ, T) Data for Novec-649, the Standard (k = 1) Uncertainty in Pressure, up, the Relative, CombinedExpanded (k = 2) Uncertainty in Density, Uc, and Relative Deviations, Δρ, of the Experimental Data from Densities Calculatedwith the New Equation of State Developed in This Worka

T/K p/MPa ρ/(kg·m−3) up/kPa Uc/% Δρ/%

Filling 1225.007 6.3066 1821.024 1.76 0.0064 −0.0198225.006 0.9925 1809.670 2.23 0.0064 −0.0107234.995 11.1554 1806.222 1.50 0.0063 −0.0106240.000 16.1997 1804.640 1.61 0.0065 −0.0143245.000 21.2274 1803.184 1.54 0.0066 −0.0196250.003 26.2084 1801.773 1.76 0.0068 −0.0265260.000 36.0595 1799.134 1.76 0.0074 −0.0445260.000 27.9305 1783.137 1.36 0.0068 −0.0192260.000 18.3924 1762.269 1.24 0.0063 0.0034260.001 12.1217 1746.985 1.20 0.0061 0.0132260.001 6.2422 1731.206 1.07 0.0059 0.0175260.001 1.1451 1716.091 1.08 0.0059 0.0166269.997 8.9222 1713.199 1.16 0.0059 0.0183274.999 12.7914 1711.877 1.19 0.0060 0.0166280.002 16.6358 1710.601 1.18 0.0061 0.0137285.002 20.4560 1709.375 1.31 0.0063 0.0096290.005 24.2546 1708.196 1.33 0.0065 0.0050295.001 28.0258 1707.058 1.50 0.0067 −0.0007303.000 33.9730 1705.207 1.38 0.0072 −0.0106302.999 28.3464 1690.631 1.52 0.0068 0.0001303.000 22.3480 1673.620 1.33 0.0064 0.0082303.000 12.1210 1639.931 1.11 0.0059 0.0130302.999 6.0692 1616.008 1.14 0.0058 0.0103302.999 1.0073 1592.529 1.07 0.0057 0.0058309.997 4.8435 1590.921 1.04 0.0058 0.0075318.004 9.2148 1589.199 1.12 0.0059 0.0084326.006 13.5583 1587.573 1.15 0.0061 0.0089334.009 17.8662 1585.991 1.19 0.0064 0.0092342.009 22.1454 1584.493 1.26 0.0067 0.0097349.999 26.3846 1583.038 1.24 0.0070 0.0096359.999 31.6201 1581.195 1.38 0.0075 0.0092359.999 21.1455 1539.182 1.19 0.0069 0.0134359.998 16.0732 1514.429 1.16 0.0067 0.0111359.996 11.0212 1485.323 1.13 0.0065 0.0073359.998 6.0025 1449.565 1.07 0.0064 0.0080359.997 1.0098 1401.619 1.04 0.0064 0.0353370.001 4.1829 1400.059 1.04 0.0066 0.0150379.999 7.3533 1398.505 1.04 0.0068 0.0070385.985 9.2541 1397.629 1.07 0.0070 0.0067393.978 11.7880 1396.477 1.10 0.0072 0.0105402.000 14.3232 1395.323 1.10 0.0075 0.0174410.014 16.8541 1394.239 1.14 0.0077 0.0267420.001 19.9870 1392.849 1.15 0.0081 0.0404430.019 23.1134 1391.482 1.20 0.0085 0.0554440.013 26.2138 1390.136 1.23 0.0089 0.0705450.008 29.2865 1388.749 1.28 0.0093 0.0847450.009 19.9480 1321.881 1.15 0.0089 0.0652

T/K p/MPa ρ/(kg·m−3) up/kPa Uc/% Δρ/%

Filling 1450.010 15.9542 1283.620 1.11 0.0088 0.0460450.010 12.0099 1235.173 1.07 0.0087 0.0193450.009 8.2152 1169.392 1.06 0.0087 −0.0103450.009 5.9836 1111.424 1.05 0.0086 −0.0213450.010 4.9939 1075.631 1.04 0.0086 −0.0198450.008 3.9971 1026.462 0.69 0.0086 0.0060450.008 1.4784 185.135 0.69 0.0100 0.0076450.006 0.9134 93.929 0.73 0.0110 0.0547450.006 0.3941 35.895 0.76 0.0429 0.1072Filling 2302.995 5.9598 1615.537 1.04 0.0058 0.0092302.996 1.0890 1592.936 1.05 0.0057 0.0051317.995 9.2957 1589.587 1.07 0.0059 0.0083334.023 17.9841 1586.441 1.17 0.0064 0.0094339.997 21.1839 1585.306 1.17 0.0066 0.0096339.997 16.1706 1564.250 1.14 0.0064 0.0093339.998 11.9380 1544.058 1.07 0.0062 0.0075339.998 7.9865 1522.496 1.05 0.0061 0.0058339.996 4.0356 1497.226 1.05 0.0061 0.0073339.997 1.0918 1474.850 1.03 0.0060 0.0155360.005 8.9155 1471.341 1.05 0.0064 0.0067380.038 16.6885 1468.097 1.11 0.0071 0.0163400.010 24.3432 1465.039 1.20 0.0078 0.0340400.007 16.0560 1413.676 1.13 0.0075 0.0216400.006 11.9986 1381.276 1.08 0.0074 0.0117400.005 8.1291 1342.482 1.05 0.0073 0.0036400.005 3.9874 1284.552 1.03 0.0072 0.0122400.005 2.0185 1244.046 1.03 0.0072 0.0381420.025 6.0757 1241.692 1.04 0.0078 −0.0108429.992 8.1177 1240.568 1.04 0.0081 −0.0097439.996 10.1720 1239.425 1.06 0.0084 0.0022449.995 12.2256 1238.266 1.08 0.0087 0.0214459.996 14.2824 1237.166 1.10 0.0091 0.0451469.995 16.3324 1236.023 1.12 0.0094 0.0708469.995 14.0312 1205.915 1.09 0.0094 0.0556469.995 11.9773 1173.863 1.08 0.0094 0.0406469.995 9.7689 1131.109 0.34 0.0093 0.0314469.995 7.9691 1085.600 0.34 0.0093 0.0252469.994 6.0874 1018.112 0.35 0.0093 0.0366469.994 2.1862 306.462 0.64 0.0098 0.1038469.996 1.3564 142.264 0.71 0.0107 0.0381469.995 0.6800 61.543 0.71 0.0107 0.0181

aTemperatures were measured on ITS-90, and the standarduncertainty in temperature was 3 mK. Data are presented in thesequence measured. Only an average value for each (T, p) state pointis given; see the Supporting Information for all data.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3650

measurements on argon gas before and after the measurementson Novec-649 did not indicate any significant shift in theresonator diameter or mechanical properties. Five isotherms at(400, 425, 450, 475, and 500) K were analyzed for the rate ofchange in the measured sound speed of Novec-649. At a fixedtemperature, the relative rate of change of sound speed withelapsed time (∂w/∂t)T was inversely proportional to pressure:

∂∂

=⎜ ⎟⎜ ⎟⎛⎝

⎞⎠⎛⎝

⎞⎠w

wt

ap

1(5)

This behavior is characteristic of gaseous diffusion and wouldbe expected for a diffusion-limited process within the sphere.(Figure S2 in the Supporting Information shows the pressuredependence at T = 500 K.)The empirical coefficient a increased exponentially with

respect to temperature based on an examination of theisotherms from 400 K to 500 K:

=a b cTexp( ) (6)

An exponential increase with respect to temperature ischaracteristic of chemical reactions with first-order kinetics.Thus, the measurements suggest that a surface-catalyzedreaction may have occurred during the speed-of-soundmeasurements on Novec-649. The same behavior would beexpected for the diffusion of a gas out of the sealing gaskets(thereby affecting the sample composition); but the gaspreviously measured in the system was argon, which wouldnot be expected to diffuse into the polyimide gaskets, and theentire system was thoroughly evacuated between the differentsample fluids.The values of a(T) at these five temperatures were fitted to

an exponential function in T (see Plot S3 available in theSupporting Information). The rate of change was found torapidly decrease with temperature for T < 400 K. The values fora(T) given by eq 6 are more reliable than it is possible to obtainfrom an analysis of the data for these lower temperatureisotherms. The corresponding coefficients for Novec-649 are b= 9.36·10−9 kPa·h−1 and c = 0.0281 K−1.For comparison, testing by the manufacturer did not show

“any measurable thermal decomposition until surface temper-atures exceed 500 °C.”18 This was a short-term test in which a

low concentration (500·10−6 mole fraction) of Novec-649 in airwas passed over a heated surface to simulate its use in a fire-suppression application; thus, it is not comparable to the longresidence times of pure Novec-649 in the resonator. Owens18

also reports accelerated aging tests to simulate long-termstorage, which showed an average decomposition of 0.0001mass fraction for sample held at 100 °C for 1514 h or adecomposition rate of 6.6·10−8 mass fraction·h−1. Extrapolatingour results (i.e., eqs 5 and 6) to T = 100 °C and p = 100 kPayields a relative rate of change in the sound speed of 9.6·10−9

%·h−1; if this were due, for example, to the formation of twomoles of decomposition products (with a sound speed twicethat of the Novec-649) for each mole of Novec-649 thatdecomposed, the rate of change in sample purity would be 4.8·10−12 mole fraction·h−1. The much lower rate for our testingindicates that the materials making up our resonator did notcatalyze any unusual sample degradation.Regardless of the mechanism of the sound speed shift, it is

possible to correct for the shift by fitting (for each series ofmeasurements along an isotherm) the measured shift in soundspeed to the two-parameter function of pressure and temper-ature given by eqs 5 and 6. The shift in sound speed for anypressure increment after the initial filling of the resonator for agiven isotherm depended on the temperature−pressure historyof the sample; the corrected sound speed, wcorr, is given by

∑

∑

= −∂

∂−

≈ − −

=−

=−

⎡⎣⎢

⎤⎦⎥

⎡⎣⎢⎢

⎤⎦⎥⎥

w w tw T p

tt t

w tb cT

pt t

( )( , )

( )

( )exp( )

( )

Ni

Ni i

i i

Ni

Ni

ii i

corr meas1

1

meas1

1(7)

where t0 is the time when the (fresh) sample was loaded intothe resonator. The overall correction to sound speed wasgenerally small for the higher-pressure measurements where therate of change was small and less time had elapsed since fillingthe resonator. As the pressure was decreased along theisotherm, the correction to the measured sound speedincreased due to a longer residence time and an increasingrate of change in the sound speed.For example, at T = 500 K and p = 0.5 MPa, the sample was

held in the resonator and measured over the course of 11.4 h tocharacterize possible sample degradation. The maximumchange in the measured sound speed was 0.010 % per hour.After application of the stability correction, the RMS deviationbetween these data is 0.012 %. We thus conclude that thesound-speed measurements at higher temperatures wereaffected by sample degradation, but that the correction tosound speed worked quite well.The corrected sound-speed data for Novec-649 are given in

Table 5 along with their combined, expanded uncertainty ateach measured temperature and pressure. Table 5 also gives thedeviations from the measured values with those calculated fromthe equation of state developed in this work. Details of thestability correction, including plots of data illustrating thechange of sound speed with experimental conditions, are givenin the Supporting Information.

3.4. Density and Sound Speed of Liquid at p = 83 kPa.Measurement results from the density and sound-speedanalyzer are shown in Table 6 for Novec-649. Reported valuesare averaged results for the seven replicate temperature scans.Also included in Table 6 are adiabatic compressibilities (κs),which were calculated from measured quantities via the relation

Table 4. Experimental (p, ρ, T) Data for Novec-649 in thenear-Critical Region (370 kg·m−3 < ρ < 986 kg·m−3), theStandard (k = 1) Uncertainty in Pressure, up, the Relative,Combined Expanded (k = 2) Uncertainty in Density, Uc, andRelative Deviations, Δp, of the Experimental Pressures fromPressures Calculated with the Equation of State Developedin This Worka

T/K p/MPa ρ/(kg·m−3) up/kPa Uc/% Δp/%

Filling 1450.009 2.9982 943.857 0.35 0.0086 −0.2396450.007 2.5006 856.702 0.39 0.0086 −0.3856450.007 2.0426 417.845 0.59 0.0086 −0.2876Filling 2469.995 4.3743 910.538 0.37 0.0093 −0.1849469.994 3.4241 779.472 0.42 0.0093 −0.0382469.994 2.7979 560.840 0.52 0.0093 −0.0775

aTemperatures were measured on ITS-90, and the standarduncertainty in temperature was 3 mK. Only an average value foreach (T, p) state point is given; see the Supporting Information for alldata.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3651

Table 5. Experimental Sound Speed Data for Novec-649 in the Vapor Phasea

T/K p/MPa Δw/(m·s−1) wcorr/(m·s−1) up/kPa Uc/% Δw/%

350.001 0.19103 0.000 88.881 0.29 0.0371 −0.0028350.003 0.15211 −0.002 90.822 0.29 0.0390 0.0262350.003 0.10466 −0.005 93.003 0.29 0.0367 0.0127350.003 0.05394 −0.007 95.198 0.29 0.0347 0.0101375.010 0.31642 −0.002 89.109 0.29 0.0387 0.0032375.011 0.22040 −0.003 93.071 0.29 0.0348 0.0197375.011 0.12345 −0.005 96.638 0.29 0.0327 0.0024375.012 0.05706 −0.007 98.909 0.29 0.0305 0.0018400.049 0.66780 −0.004 81.519 0.30 0.0445 −0.0543400.049 0.55473 −0.007 86.448 0.30 0.0381 −0.0202400.050 0.45142 −0.007 90.396 0.30 0.0350 −0.0028400.050 0.35419 −0.008 93.749 0.29 0.0325 0.0026400.050 0.25299 −0.012 96.943 0.29 0.0310 −0.0040400.051 0.15466 −0.014 99.830 0.29 0.0289 −0.0052400.051 0.05488 −0.019 102.635 0.29 0.0279 0.0501400.052 0.05492 −0.019 102.635 0.29 0.0279 0.0504425.039 1.06169 −0.002 75.845 0.35 0.0511 −0.0057425.038 0.95186 −0.002 80.492 0.35 0.0449 −0.0261425.036 0.84573 −0.002 84.469 0.34 0.0391 −0.0366425.038 0.69635 −0.003 89.446 0.34 0.0372 −0.0350425.038 0.54605 −0.004 93.910 0.30 0.0313 −0.0178425.038 0.39911 −0.008 97.857 0.29 0.0301 −0.0118425.038 0.25800 −0.010 101.356 0.29 0.0285 −0.0033425.037 0.14461 −0.013 103.996 0.29 0.0266 −0.0007425.038 0.06031 −0.021 105.936 0.29 0.0263 0.0546449.975 1.68076 −0.002 66.676 0.37 0.0596 −0.0454449.974 1.49196 −0.003 74.053 0.37 0.0481 0.0324449.975 1.29210 −0.004 80.706 0.35 0.0412 −0.0073449.977 1.10480 −0.005 86.187 0.35 0.0347 −0.0379449.976 0.90163 −0.009 91.502 0.34 0.0316 −0.0530449.975 0.70104 −0.011 96.257 0.34 0.0294 −0.0408449.975 0.49937 −0.013 100.640 0.33 0.0281 −0.0197449.977 0.29698 −0.016 104.717 0.33 0.0267 −0.0009449.975 0.09980 −0.036 108.429 0.32 0.0260 −0.0055475.010 1.68503 −0.002 82.694 0.36 0.0368 −0.0090475.009 1.49658 −0.003 86.779 0.36 0.0346 −0.0278475.010 1.29623 −0.006 90.916 0.35 0.0326 −0.0527475.008 1.15088 −0.008 93.767 0.34 0.0345 −0.0580475.006 0.89852 −0.011 98.512 0.34 0.0286 −0.0543475.008 0.69746 −0.013 102.078 0.33 0.0275 −0.0239475.013 0.50177 −0.018 105.378 0.29 0.0264 −0.0005475.013 0.50176 −0.020 105.379 0.29 0.0264 −0.0008475.013 0.50176 −0.023 105.378 0.29 0.0265 −0.0011475.013 0.50178 −0.025 105.377 0.29 0.0265 −0.0016475.012 0.50180 −0.028 105.380 0.29 0.0314 0.0017475.011 0.50177 −0.031 105.377 0.29 0.0267 −0.0022475.013 0.34950 −0.036 107.829 0.29 0.0262 0.0074475.012 0.14779 −0.051 110.979 0.29 0.0253 0.0053500.017 1.74686 −0.011 91.994 0.36 0.0294 −0.0270500.016 1.74670 −0.012 91.996 0.36 0.0292 −0.0276500.014 1.74646 −0.014 91.998 0.36 0.0292 −0.0273500.014 1.50360 −0.017 95.589 0.35 0.0279 −0.0540500.014 1.30811 −0.020 98.443 0.35 0.0293 −0.0693500.014 1.10083 −0.024 101.422 0.34 0.0291 −0.0658500.012 1.10041 −0.033 101.424 0.34 0.0288 −0.0692500.010 0.89384 −0.038 104.330 0.34 0.0276 −0.0503500.008 0.70351 −0.045 106.946 0.33 0.0266 −0.0267500.013 0.50300 −0.055 109.636 0.29 0.0263 −0.0054500.012 0.50281 −0.060 109.636 0.29 0.0263 −0.0079500.011 0.50270 −0.066 109.634 0.29 0.0264 −0.0101500.010 0.50262 −0.071 109.633 0.29 0.0265 −0.0122

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3652

κρ

=·w1

s 2 (8)

where ρ is density, w is speed of sound, and the subscript sindicates “at constant entropy.”3.5. Uncertainty in Measurements. The measurement

uncertainties of the experimental data presented in this work(vapor pressure, density, and speed of sound) were evaluatedfollowing the law of propagation of uncertainties.19 We statestandard (k = 1) uncertainties in the discussion and apply acoverage factor of 2 to yield a combined, expanded uncertaintywith an approximate confidence interval of 95 %.3.5.1. Uncertainty of Vapor-Pressure Measurements. The

uncertainty in the vapor-pressure measurements carried out inthe spherical resonator arose from the calibration of thetransducers, the repeatability and temporal drift of thetransducers, and the uncertainty in the hydrostatic headcorrection. The pressure transducers were calibrated withpiston gauges. We estimated the standard uncertainty in thepressure measurement to be (20·10−6·p + 0.020 kPa) for the0.7 MPa transducer and (20·10−6·p + 0.15 kPa) for the 6.2 MPatransducer. The uncertainty in the hydrostatic head correctionwas estimated to be 10 % of the head correction, Δphead.

The SPRT was calibrated with fixed-point cells on ITS-90.The uncertainty in the temperature measurement system(SPRT and its calibration, resistance bridge, and standardresistor) was estimated to be 5 mK. The uncertainty in thetemperature of the fluid sample also included the effects oftemperature gradients and oscillations over time; we estimatedthe total temperature uncertainty to be 20 mK.The expanded, combined uncertainty for vapor pressures also

includes the uncertainty in temperature,

σ= · + + ·Δ

+∂∂

⎪

⎪

⎪

⎪

⎧⎨⎩

⎛⎝⎜

⎞⎠⎟

⎫⎬⎭

U p u p p p

p

Tu T

( ) 2 ( ) [ ( )] [0.1 ]

( )

C sat2

transducer2

head2

sat2

2

1/2

(9)

where the first term on the right-hand side represents theuncertainty due to the pressure transducer, σ(p) is the standarddeviation of the replicate pressure readings taken over theduration of a vapor-pressure determination, and the derivativeof vapor pressure is calculated with the present equation ofstate. The relative combined expanded uncertainty in themeasured vapor pressures was as large as 1.21 % at the lowesttemperature measured (325 K), but decreased with increasingtemperature and vapor pressure to 0.12 % at 420 K.

3.5.2. Uncertainty of Density Measurements. The measure-ment uncertainty of the experimental density data measuredwith the two-sinker densimeter has been evaluated in previouswork.6,20,21 Only a brief description of the main uncertaintysources is given here.The main sources of the uncertainty in density, in order of

significance, arose from the sinker volumes (V1, V2), theweighings of the sinkers and the calibration masses (W1, W2,Wcal, Wtare) and the masses of these objects (m1, m2, mcal, mtare),and the apparatus zero ρ0. The density uncertainty includes theeffects of the force transmission error and vertical densitygradients in the measuring cell. The variance in the replicatebalance readings is also considered. The standard uncertainty inthe density measurement is given by

Table 5. continued

T/K p/MPa Δw/(m·s−1) wcorr/(m·s−1) up/kPa Uc/% Δw/%

500.010 0.50255 −0.076 109.631 0.29 0.0267 −0.0148500.008 0.50244 −0.082 109.630 0.29 0.0268 −0.0170500.008 0.30145 −0.097 112.251 0.29 0.0262 −0.0146500.006 0.10324 −0.147 114.768 0.32 0.0278 −0.0419324.970 0.10058 0.000 88.408 0.29 0.0457 0.0060324.971 0.10055 −0.001 88.410 0.29 0.0457 0.0060324.972 0.10055 −0.001 88.410 0.29 0.0457 0.0061324.972 0.10057 −0.001 88.408 0.29 0.0457 0.0053324.970 0.08258 −0.002 89.491 0.29 0.0441 0.0414324.971 0.06534 −0.003 90.450 0.29 0.0427 0.0230349.971 0.19177 0.000 88.849 0.29 0.0412 0.0108349.974 0.15002 −0.001 90.927 0.29 0.0387 0.0387349.975 0.10624 −0.002 92.934 0.29 0.0366 0.0194349.976 0.06183 −0.004 94.862 0.29 0.0349 0.0108

aListed are the measured temperature T and pressure p, the correction for sample degradation effects, Δw, the corrected speed of sound, wcorr, thestandard uncertainty in pressure, up, the relative combined expanded uncertainty in the sound speed, Uc, and relative deviations of the experimentaldata from sound speed calculated with the equation of state developed in this work, Δw. Temperatures were measured on ITS-90, and the standarduncertainty in temperature was 20 mK. The speed of sound listed is an average of the (0, 2), (0, 3), and (0, 4) modes; see the SupportingInformation for all data.

Table 6. Density, Speed of Sound, and AdiabaticCompressibility, and Their Combined ExpandedUncertainties for Liquid Novec-649 at p = 83 kPaa

T ρ Uc(ρ) w Uc(w) κs Uc(κs)

K kg·m−3 kg·m−3 m·s−1 m·s−1 TPa−1 TPa−1

308.15 1571.82 0.37 472.63 0.75 2848.1 4.6303.15 1587.28 0.37 488.11 0.75 2644.3 4.1298.15 1602.48 0.37 503.72 0.75 2459.4 3.7293.15 1617.51 0.37 519.58 0.75 2290.1 3.4288.15 1632.33 0.37 535.45 0.75 2136.7 3.0283.15 1646.79 0.40 551.54 0.75 1996.2 2.8278.15 1660.83 0.40 567.88 0.75 1867.1 2.5

aTemperatures were measured on ITS-90, and the standarduncertainty in temperature was 50 mK. The standard uncertainty inpressure was 0.7 kPa.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3653

ρ

ρ

·

= + − +

· · +

−

− −

u

T p

( )/kg m

[{28} {0.20( /K 293)} {0.63 /MPa} ]

10 /kg m 0.0010

3

2 2 2 1/2

6 3(10)

where the term in brackets is from the sinker volumeuncertainty. The final, constant term includes all otheruncertainties; it is slightly larger than the value reported inref 6, due to the variation in ρ0 observed over the course of thetesting on Novec-649.The SPRT used to measure the fluid temperature was

calibrated with fixed-point cells on ITS-90. The standarduncertainty in temperature was estimated to be 3 mK, includingthe measuring system and possible temperature gradients.The uncertainty in the pressure arose from the uncertainties

in the pressure transducers and the hydrostatic head correction.The pressure transducers were calibrated with piston gauges.The standard uncertainty in pressure was (20·10−6p + 0.03kPa) for the low-pressure range (0.1 to 1.6) MPa, (20·10−6p +0.15 kPa) for the medium-pressure range (1.6 to 8.0) MPa, and(26·10−6p + 1.0 kPa) for the high-pressure range (8.0 to 40.0)MPa. The uncertainty in the head correction was estimated tobe 10 % of the head correction, Δphead.For the development of equations of state it is preferable to

use the expanded, combined uncertainty in density, whichincludes the uncertainties in temperature and pressure:

ρ ρ ρ ρ= · + ∂∂

+ ∂∂

⎪

⎪

⎪

⎪

⎧⎨⎩

⎡⎣⎢

⎤⎦⎥

⎡⎣⎢

⎤⎦⎥

⎫⎬⎭

U up

u pT

u T( ) 2 ( ) ( ) ( )C2

22

22

1/2

(11)

Here UC is the expanded, combined uncertainty, and u is thestandard uncertainty; the uncertainty in pressure includes theeffect of the hydrostatic head correction. The partial derivativeswere estimated with the equation of state presented here.Details of the individual uncertainty terms are listed for eachmeasured point in the Supporting Information.

3.5.3. Uncertainty of Sound-Speed Measurements. Theuncertainty of the measurements in the spherical resonator isdiscussed in detail by Perkins and McLinden,12 and we use thatanalysis here. A tabulation of the individual uncertaintycomponents for each measured point is given in the SupportingInformation, and a summary of the uncertainties is given inTable 7.The uncertainties in temperature and pressure are the same

as those discussed for the vapor-pressure measurements insection 3.5.1. The standard deviations in the observedtemperature and pressure readings taken before, during, andafter a resonance scan were added to these uncertaintyestimates.The purity of our sample was 0.9995 mole fraction, and we

estimated that this would contribute a relative standarduncertainty of 0.01 % to the speed of sound. This includesboth the effect of the impurities identified in section 2.1 and theuncertainty associated with the correction for sampledegradation discussed in section 3.3. It is the largestcontribution to the uncertainty in sound speed. The nextlargest uncertainties resulted from the sphere diameter (i.e., thecalibration with argon) and the pressure measurement. Bycontrast, the boundary layer and shell resonance correctionswere small, as was the uncertainty due to the bandwidth (i.e.,the uncertainty resulting from the fitting of the resonancepeak). Dispersion was expected to be negligible for a complexmolecule, such as Novec-649. The variance for the sound speedbetween the different radial modes was relatively small,indicating that the (0, 2) through (0, 4) radial modes gaveconsistent results. The relative combined expanded uncertainty(k = 2) in the speed of sound ranged from 0.025 % to 0.060 %;it averaged 0.033 %.

3.5.4. Uncertainty of Density and Sound Speed of Liquidat 83 kPa. The expanded uncertainties for density Uc(ρ), speedof sound Uc(w), and adiabatic compressibility Uc(κs) are givenin Table 6. The uncertainty estimates for density and speed ofsound include contributions for the standard deviation ofreplicate temperature scans, instrument resolution, and instru-

Table 7. Summary of Errors and Resulting Uncertainties in the Speed of Sound for Novec-649

uncertainties in sound speed/(m·s−1)(unless otherwise indicated)

source magnitude of error average range

State-Point Uncertaintiestemperature 0.020 K 0.0039 0.0024 to 0.0089pressure a 0.0089 0.0010 to 0.0171sample purity 0.01 % 0.0096 0.0067 to 0.0115

Sphere DiameterD0 (T = 300 K) 0.0040 mm 0.0074 0.0062 to 0.0084D(T) 0.00004 mm · (T/K − 300) 0.0005 0.0000 to 0.0011D(p) 0.00016 mm · p/MPa 0.0012 0.0009 to 0.0054D(t) [time stability] 0.0013 mm 0.0024 0.0020 to 0.0027

Fitting of, and Corrections to, Resonance Peakbandwidth 1 % of bandwidth 0.0001 0.0000 to 0.0032boundary layer 10 % of correction < 0.0001 0.0000 to 0.0001shell resonance 10 % of correction < 0.0001 0.0000 to 0.0001

Combined and Averaged Uncertaintiesuc for a given mode (k = 1) 0.0157 0.0110 to 0.0238standard deviation between modes 0.0033 0.0005 to 0.0198combined expanded (k = 2) uncertainty averaged across all modes 0.0314 0.0220 to 0.0477relative combined expanded (k = 2) uncertainty averaged across all modes 0.033 % (0.025 to 0.060) %

aMagnitude of pressure error is (20·10−6·p + 0.020 kPa) for the 0.7 MPa transducer and (20·10−6·p + 0.15 kPa) for the 6.2 MPa transducer

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3654

ment calibration, as well as the uncertainty in measuredtemperature and pressure. Since adiabatic compressibility is acalculated quantity, its uncertainty is derived from thepropagation of uncertainties for the two measured quantities.Additional details of the uncertainty analysis for this instrumentcan be found in Laesecke et al.,13 Fortin,14 and Fortin et al.15

4. EQUATION OF STATE

The experimental thermodynamic properties of Novec-649presented in this work were fitted to a 17-term equation of stateexplicit in the Helmholtz energy with the density andtemperature as independent variables. The fit started with thepropane equation of state of Lemmon et al.22 In addition to thepresent data, the critical temperature and low-temperaturevapor-pressure data of Stempko and Fayemi23 were included inthe fitting. The fitting process is described by Lemmon andJacobsen.24 This equation of state is valid over the temperaturerange from (168 to 500) K and at pressures up to 50 MPa. Theform of the equation of state will reliably extrapolate outsidethe range of the experimental data, although with increaseduncertainties.4.1. Functional Form of the Equation of State. The

equation of state is of the form

ρ ρ ρ= +a T a T a T( , ) ( , ) ( , )0 r(12)

where a is the Helmholtz energy, a0(ρ,T) represents the idealgas behavior, and ar(ρ,T) accounts for the residual contribution.This form of the equation is the most convenient since all thethermodynamic properties can be obtained by derivatives fromthe Helmholtz energy. This is usually expressed in terms of thedimensionless Helmholtz energy α = a/(RT):

α δ τ α δ τ α δ τ= +( , ) ( , ) ( , )0 r(13)

where δ = ρ/ρc and τ = Tc/T are the reduced density and

inverse reduced temperature relative to Tc and ρc, the critical

temperature and density, respectively, that are given in Table 8.The ideal-gas contribution to the Helmholtz energy in its

dimensionless form is

τ δ τ

ντ

= + + + −

+ −−⎡

⎣⎢⎢

⎛⎝⎜

⎞⎠⎟⎤⎦⎥⎥

a a a c

uT

ln ( 1) ln

ln 1 expc

01 2 0

11

(14)

where c0 = 30.8, v1 = 29.8, and u1 = 1940 K. The terms a1 and

a2 were calculated to set the reference state equal to an

enthalpy of 200 kJ·kg−1 and an entropy of 1 kJ·kg−1·K−1 for the

saturated liquid at 0 °C. The values of these terms are a1 =

−30.661 050 3233 and a2 = 6.830 529 6372. The other values

were derived from the ideal-gas heat capacity equation:

= +−

⎜ ⎟⎛⎝

⎞⎠

c

Rc v

uT

u Tu T

exp( / )[exp( / ) 1]

p0

0 11

21

12

(15)

where c0, ν1, and u1 are the same as those in eq 14, and the

molar gas constant, R, is 8.314 4621 J·mol−1·K−1 (Mohr et

al.25).The functional form of the residual contribution to the

Helmholtz energy is

Table 8. Coefficients and Exponents of the Equation of State eq 16; Coefficients Not Listed Are Zero. Critical Parameters: Tc =441.81 K; ρc = 1.92 mol·L−1; pc = 1.869 MPa

k Nk tk dk lk ηk βk γk εk

1 0.05623648 1.0 4.2 2.973616 0.25 1.3 −6.126970 0.793 1.4 3.440240 1.16 1.5 1.451737 0.75 2.6 −2.837857 1.09 2.7 0.2077767 0.75 3.8 2.168307 1.3 2. 1.9 −2.124648 2.25 1. 2.10 −1.296704 1.9 2. 2.11 −1.010569 0.88 1. 0.32 0.12 1.10 1.1612 2.701505 1.63 1. 1.32 0.83 1.04 0.79313 0.8167202 1.3 2. 1.35 0.19 1.15 1.1314 −1.814579 2.0 2. 1.48 0.95 0.90 0.52715 0.2075389 1.15 3. 0.51 0.10 0.80 1.1916 −1.009347 1.66 3. 1.30 0.11 1.20 0.8317 −0.04848043 1.5 1. 5.15 65.00 1.19 0.82

Table 9. Calculated Values of Properties from the Equation of State to Verify Computer Code

T/K ρ/(mol·L−1) p/MPa CV/(J·mol−1·K−1) Cp/(J·mol−1·K−1) w/(m·s−1)

250.0 5.6 11.459869 277.136 341.656 716.250400.0 4.0 2.9272365 308.183 386.271 245.654442.0 1.92 1.8757729 351.688 45430.0 37.0298250.0 0.001 0.0020718017 254.272 262.743 82.1676450.0 4.6 42.305705 319.295 365.304 512.603

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3655

∑ ∑

∑

α δ τ δ τ δ τ δ

δ τ η δ ε

β τ γ

= + −

+ − −

− −

= =

=

N N

N

( , ) exp( )

exp( ( )

( ) )

kk

d t

kk

d t l

kk

d tk k

k k

r

1

7

8

10

11

172

2

k k k k k

k k

(16)

where the fitted coefficients and exponents are given in Table 8.Pressure, enthalpy, heat capacity, speed of sound, and all otherthermodynamic properties can be obtained from the equationof state by appropriate derivatives as given by Lemmon et al.22

The equation of state was fitted with the experimental datareported in this work. We adopted the critical temperaturereported by Stempko and Fayemi23 and also fitted their low-temperature vapor-pressure data. Other available data arecompared with the equation of state in section 4.3.Values of properties in the liquid, vapor, and supercritical

regions calculated with the equation of state are given in Table9; these values can be used to validate computer codeimplementing the equations and coefficients given in thiswork. The number of significant digits does not represent theuncertainty in the data but are given as an aid for codeverification. The state point at very low density can be used totest the ideal-gas properties. The state at T = 442 K is very closeto the critical point, where the properties of the fluid changerapidly. Calculations that are identical to those given in Table 9will demonstrate the correct implementation of the model.4.2. Ancillary Equations. The boundaries between liquid

and vapor are defined by saturation states, and ancillaryequations can be used to give initial estimates for the pressureand densities required in the iterative procedures necessary tofind the saturation states. These ancillary equations are notrequired when a full equation of state is available, sinceapplication of the Maxwell criteria to the equation of state willyield the saturation states. The ancillary equations were fitted tovalues calculated from the full equation of state given in section4.1.The vapor pressure can be represented with the ancillary

equation

θ θ θ θ θ= + + + +σ⎛⎝⎜⎜

⎞⎠⎟⎟

p

pTT

N N N N Nln [ ]c

c1 2

1.53

2.24

4.45

15

(17)

where N1 = −8.4411, N2 = 2.711, N3 = −3.6354, N4 = −5.3872,N5 = −8.1641, θ = (1 − T/Tc), and pσ is the vapor pressure.The saturated-liquid density can be represented by

ρρ

θ θ θ′ = + + +N N N1c

10.297

20.7

34.4

(18)

where N1 = 1.5545, N2 = 1.149, N3 = 0.51565, and ρ′ is thesaturated-liquid density. The saturated-vapor density can berepresented by the equation

ρρ

θ θ θ θ θ″ = + + + +⎛⎝⎜⎜

⎞⎠⎟⎟ N N N N Nln

c1

0.2912

0.823

2.454

5.55

12

(19)

where N1 = −1.6073, N2 = −5.8095, N3 = −17.824, N4 =−61.012, N5 = −151.3, and ρ″ is the saturated-vapor density.The critical temperature, pressure, and density required in theancillary equations are given in Table 8.

4.3. Comparisons with Experimental Data. Theexperimental data are compared to the equation of state interms of their relative deviations, eq 4. The overall quality ofthe fit is expressed by the relative root-mean-square (RMS)deviation:

σχ χ χ

=∑ −=

⎡⎣⎢⎢

⎤⎦⎥⎥n

[100( )/ ]in

i i i1 exp, EOS, EOS,2 1/2

(20)

where χ is a property and n is the number of points used for thecomparison.

4.3.1. Vapor Pressure. Figure 3 depicts the relativedeviations of the experimental vapor pressures from the values

calculated with the present equation of state. At thetemperatures measured here, the pressure in the resonatorcell is above the dew point at the pressure transducer, and thepressure line is completely filled with liquid; thus, theuncertainty in the hydrostatic head correction is small. Thepoints measured in the first filling of the resonator were veryconsistent with the second filling. The RMS deviation of all thedata is 0.066 %. Data from both fillings show increaseduncertainty at the lowest temperatures measured due to thelimited sensitivity of the pressure transducer and the increasingsignificance of the head correction.Stempko and Fayemi23 report vapor pressures over the

temperature range (270 to 430) K. These data are also plottedin Figure 3. The vapor pressures reported by Stempko andFayemi23 at temperatures below 330 K were determined bystatic measurements of the pressure of the sample in a glasssystem with pressures measured with a mercury manometer.These low-pressure measurements23 have an estimateduncertainty of 1 % and agree with the present data and theequation of state well within their uncertainty (RMS deviationof 0.50 %). Stempko and Fayemi23 also reported vaporpressures at temperatures above 330 K with static pressuremeasurements of the pressure of the sample in a stainless-steelpressure system with a pressure transducer. These measure-ments23 have an estimated uncertainty of 1 % and aresystematically lower than the present measurements with anRMS deviation of 1.09 % and a maximum deviation of −1.76 %.

Figure 3. Deviations between the measured vapor pressure of Novec-649 and the vapor pressure calculated with the equation of statedeveloped in this paper; ⧫, present workfirst filling of resonator; ▲,second filling of resonator; ■, glass-mercury manometer system;23 □,stainless-steel pressure system with pressure transducer.23

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3656

4.3.2. (p, ρ, T) Behavior. The deviations of the experimental(p, ρ, T) data from the equation of state are shown in Figure 4.The RMS deviation for all the points is 0.067 %. The liquidphase data are fitted very well, with an RMS deviation for ρ >1000 kg·m−3 of 0.026 %. The deviations in the vicinity of thecritical point are larger, with a maximum deviation of −0.386 %at (T = 450 K, p = 2.50 MPa, ρ = 417.8 kg·m−3). The data inthe immediate vicinity of the critical point are plotted asdeviations in pressure, rather than density.

The liquid densities measured at atmospheric pressure in thebenchtop instrument are also shown in Figure 4. They agreevery well with the densimeter data and have an RMS deviationwith the new equation of state of 0.010 %.4.3.3. Speed of Sound. The deviations of the experimental

speed-of-sound data from the equation of state are shown inFigure 5. The RMS deviation of the data from the new equationof state is 0.029 %, which is comparable to the averageexpanded (k = 2) uncertainty of the sound-speed measure-ments of 0.033 %. The isotherm at 350 K was measured at thestart of measurements and again at the end of the measure-

ments. There is good agreement, within 0.01 %, between bothsets of measurements at T = 350 K.Deviations between the measured speed of sound of liquid

Novec-649 and the equation of state are shown in Figure 5.The measurements were made at the local atmosphericpressure of 83 kPa over the temperature range from (278 to308) K. These data have an RMS deviation with the equation ofstate of 0.045 %, which is well within their expanded (k = 2)uncertainty of 0.75 m·s−1 (equivalent to 0.13 % to 0.16 %).

4.3.4. Literature Data for ρ and Cp. In addition to thevapor-pressure measurements of Novec-649 described earlier,Stempko and Fayemi23 reported measurements of the densityof liquid and vapor and the isobaric heat capacity of the liquid.Relative deviations between these data sets and the equation ofstate are shown in Figure 6 over their temperature range from(235 to 450) K.Vapor densities were measured with a temperature-

controlled pressure system with a calibrated volume of about1.8 L. Known masses of sample were added and removed fromthe pressure system with a weigh cylinder. The vapor densitydata have an uncertainty of 2 % according to Stempko andFayemi.23 The RMS deviation of these vapor densities overtheir temperature range of (353 to 448) K is 0.80 %.Compressed-liquid densities were measured with a temper-

ature-controlled pressure system with a calibrated volume.Liquid sample was filled at temperatures near 273 K and heatedto reach the desired pressure. Known masses of sample wereadded and removed from the pressure system with a weighcylinder. The liquid-density data have a reported uncertainty of0.5 %. These data show a distinct systematic trend in thedeviations as the temperature increases. The RMS deviation ofthese data is 0.71 % over their temperature range of (280 to398) K.

Figure 4. Relative deviations of the experimental (p, ρ, T) data forNovec-649 from values calculated with the present equation of stateplotted as (a) a function of temperature T, (b) as a function ofpressure p; and (c) as a function of density ρ: +, Filling 1; ▲, filling 2;×, filling 1 near-critical points plotted as deviations in pressure; △,filling 2 near-critical points plotted as deviations in pressure; □, liquiddensity at atmospheric pressure; the dotted vertical lines indicate thecritical point.

Figure 5. Relative deviations of the experimental speed of sound forNovec-649 from values calculated with the present equation of state(a) plotted as a function of temperature T: ○, vapor phase in thespherical resonator; ∗, liquid phase in benchtop instrument. (b)plotted as a function of pressure p: ×, T = 325 K; +, T = 350 K; ▽, T= 375 K; ○, T = 400 K; □, T = 425 K; ◊, T = 450 K; △, T = 475 K; ⧫,T = 500 K; *, liquid phase in the benchtop instrument, T = (278 to308) K).

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3657

Liquid densities at a pressure of 0.1 MPa and at thesaturation pressure were measured with glass volumetric flasksimmersed in an isothermal stirred bath. The volumes of theflasks, up to various expansion marks on their necks, werecalibrated with weighed quantities of water at a fixedtemperature. The thermal expansion was accounted for bythe known thermal expansion of the glass. These liquid densitydata have a reported uncertainty of 0.25 %. The RMS deviationof the saturated liquid densities over their temperature range of(283 to 313) K is 0.13 % from the present equation of state.The RMS deviation of the liquid densities at p = 0.1 MPa overtheir temperature range of (235 to 304) K is 0.16 %.Isobaric heat capacities of the liquid at saturation were

measured from (263 to 333) K. The RMS deviation of thesedata is 0.22 % over their temperature range of (235 to 304) K.4.3.5. Literature Data for the Critical Point. Stempko and

Fayemi23 reported measurements of the critical temperature,pressure, and density of Novec-649 that were obtained with avisual cell apparatus. They found Tc = 441.81 K, pc = 1.865MPa, and ρc = 639.1 kg·m−3. The uncertainty of the reportedcritical temperature was estimated to be 0.5 K, and theuncertainty in the reported critical pressure was estimated to be1 %. These compare to the values adopted in the presentequation of state of Tc = 441.81 K, pc= 1.869 MPa, and ρc =606.81 kg·m−3. We adopted the critical temperature ofStempko and Fayemi in our equation of state, while the criticalpressure and density were adjustable parameters in the EOSfitting process. The relative differences between the EOS valuesand the experimental literature values are 0.21 % for pc and−5.32 % for ρc.

5. DISCUSSION AND CONCLUSIONSAccurate experimental data of density, vapor pressure, andspeed of sound of a high-purity sample of Novec-649 have beenpresented in this work. Densities of the compressed liquid weremeasured with a two-sinker densimeter employing a magneticsuspension coupling over the temperature range from (225 to480) K, with pressures up to 36 MPa. Densities in the vicinityof the critical point were also measured. Speed-of-sound datawere measured in the gas phase with a spherical acousticresonator over the temperature range from (325 to 500) K,

with pressures up to 1.7 MPa. Vapor pressures were determinedover a temperature range from (325 to 420) K. The density andspeed of sound of the liquid at atmospheric pressure weremeasured over the temperature range from (278 to 308) K.These data were sufficient for the development of an accurateequation of state.The time-dependent increase in measured sound speed of

the gas indicated that Novec-649 was subject to slightdegradation that increased at high temperatures and lowpressures, typical of a surface reaction. These changes werecorrected by extrapolating back to t = 0 (i.e., fresh sample) sothat the effect on the reported properties was small. Replicatemeasurements of density on a sample held at high temperatureshowed only very slight changes.An equation of state explicit in the Helmholtz free energy

was fitted to the experimental data reported here together withselected literature data. This new equation of state covers boththe liquid and gas phases, and supercritical states. It is the bestequation of state currently available for this fluid. It has beenincluded in the NIST REFPROP26 database.

■ ASSOCIATED CONTENT*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acs.jced.5b00623.

All measured values from which the average valuesreported in the tables were calculated, and details on theuncertainties for each measured point (PDF)

■ AUTHOR INFORMATIONCorresponding Author*E-mail: markm@boulder.nist.gov. Tel.: +1-303-497-3580. Fax:+1-303-497-6682.

FundingWe acknowledge partial support for this work by U.S.Department of Energy through United Technologies ResearchCenter Agreement DE-EE0002770: Tailored Working Fluidsfor Enhanced Geothermal Power Plants.

NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSWe thank Paul Stempko and Dele Fayemi of 3M for providingthe high-purity sample and data on thermodynamic andtransport properties of Novec-649. We thank our NISTcolleague Marcia Huber for the development of a correlationfor the transport properties of Novec-649. We thank TomBruno and Tara Lovestead of NIST for the chemical analysis ofthe sample and Ian Bell of NIST for providing the 3-Drepresentation of the Novec-649 molecule.

■ DEDICATIONWe thank the JCED Editors for organizing this Memorial Issuefor Dr. Anthony A. H. Goodwin and are honored to contributethis manuscript. Above all we wish to express our appreciationfor many collegial discussions, scientific collaborations, andvalued friendship with Tony Goodwin through the years. Hiscontributions to the knowledge of thermophysical properties asa creative researcher in academia and industry as well as atechnical editor of several books and this Journal will continue

Figure 6. Relative deviations between the property data of Stempkoand Fayemi23 and the equation of state developed in this work: △,liquid density at 0.1 MPa; ▲, saturated liquid density; +, compressedliquid density; ○, vapor-phase density; ▽, saturated liquid heatcapacity.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3658

to inspire and guide many in this area for years to come.Thanks Tony.

■ REFERENCES(1) Wieser, M. E.; Berglund, M. Atomic weights of the elements 2007(IUPAC Technical Report). Pure Appl. Chem. 2009, 81, 2131−2156.(2) Taniguchi, N.; Wallington, T. J.; Hurley, M. D.; Guschin, A. G.;Molina, L. T.; Molina, M. J. Atmospheric chemistry of C2F5C(O)CF-(CF3)2: Photolysis and reaction with Cl atoms, OH radicals andozone. J. Phys. Chem. A 2003, 107, 2674−2679.(3) E.P.A. Halon Substitutes under SNAP as of October 21, 2014.http://www.epa.gov/ozone/snap (accessed 2/17/2015).(4) Bruno, T. J.; Svoronos, P. D. N. CRC Handbook of Basic Tables forChemical Analysis, 3rd ed.; Taylor and Francis, CRC Press: BocaRaton, FL, 2011.(5) Wagner, W.; Kleinrahm, R. Densimeters for very accurate densitymeasurements of fluids over large ranges of temperature, pressure, anddensity. Metrologia 2004, 41, S24−S39.(6) McLinden, M. O.; Losch-Will, C. Apparatus for wide-ranging,high-accuracy fluid (p-ρ-T) measurements based on a compact two-sinker densimeter. J. Chem. Thermodyn. 2007, 39, 507−530.(7) Kleinrahm, R.; Wagner, W. Measurement and correlation of theequilibrium liquid and vapour densities and the vapour pressure alongthe coexistence curve of methane. J. Chem. Thermodyn. 1986, 18, 739−760.(8) McLinden, M. O.; Kleinrahm, R.; Wagner, W. Force transmissionerrors in magnetic suspension densimeters. Int. J. Thermophys. 2007,28, 429−448.(9) Moldover, M. R.; Mehl, J. B.; Greenspan, M. Gas-filled sphericalresonators: Theory and experiment. J. Acoust. Soc. Am. 1986, 79, 253−272.(10) Moldover, M. R.; Trusler, J. P. M.; Edwards, T. J.; Mehl, J. B.;Davis, R. S. Measurement of the universal gas constant R using aspherical acoustic resonator. J. Res. Natl. Bur. Stand. 1988, 93, 85−144.(11) Trusler, J. P. M. Physical Acoustics and Metrology of Fluids; CRCPress: Boca Raton, FL, 1991.(12) Perkins, R. A.; McLinden, M. O. Spherical resonator for vapor-phase speed of sound and measurements of 1,1,1,2,2,3,3-heptafluoro-3-methoxypropane (RE347mcc) and trans-1,3,3,3-tetrafluoropropene[R1234ze(E)]. J. Chem. Thermodyn. 2015, 91, 43−61.(13) Laesecke, A.; Fortin, T. J.; Splett, J. D. Density, speed of sound,and viscosity measurements of reference materials for biofuels. EnergyFuels 2012, 26, 1844−1861.(14) Fortin, T. J. Assessment of variability in the thermophysicalproperties of rocket propellant RP-1. Energy Fuels 2012, 26, 4383−4394.(15) Fortin, T. J.; Laesecke, A.; Freund, M.; Outcalt, S. Advancedcalibration, adjustment, and operation of a density and sound speedanalyzer. J. Chem. Thermodyn. 2013, 57, 276−285.(16) Huber, M. L. Personal Communication; NIST, 2012.(17) Fortin, T. J. Personal Communication; NIST, 2015.(18) Owens, J. G. Understanding the Stability and EnvironmentalCharacteristics of a Sustainable Halon Alternative; Proceedings, 14thHalon Options Technical Working Conference, NIST SpecialPublication 984-2, 2004.(19) Taylor, B. N.; Kuyatt, C. E. Guidelines for evaluating andexpressing uncertainty of NIST measurement results; Technical Note1297, U.S. Government Printing Office: Washington DC, 1994.(20) McLinden, M. O.; Splett, J. D. A liquid density standard overwide ranges of temperature and pressure based on toluene. J. Res. Natl.Inst. Stand. Technol. 2008, 113, 29−67.(21) McLinden, M. O. Thermodynamic properties of propane. I. p-ρ-T behavior from 265 to 500 K with pressures to 36 MPa. J. Chem. Eng.Data 2009, 54, 3181−3191.(22) Lemmon, E. W.; Wagner, W.; McLinden, M. O. Thermody-namic properties of propane. III. Equation of state. J. Chem. Eng. Data2009, 54, 3141−3180.(23) Stempko, P.; Fayemi, D., Personal Communication, 3MCorporation, Novec-649 Thermodynamic and Transport Data, 2010.

(24) Lemmon, E. W.; Jacobsen, R. T. A new functional form andfitting techniques for equations of state with application topentafluoroethane (HFC-125). J. Phys. Chem. Ref. Data 2005, 34,69−108.(25) Mohr, P. J.; Taylor, B. N.; Newell, D. B. CODATArecommended values of the fundamental physical constants: 2010.Rev. Mod. Phys. 2012, 84, 1527−1605.(26) Lemmon, E. W.; Huber, M. L.; McLinden, M. O. NIST StandardReference Database 23; NIST Reference Fluid Thermodynamic andTransport PropertiesREFPROP, version 9.1; Standard ReferenceData Program; National Institute of Standards and Technology:Gaithersburg, MD, 2013.

Journal of Chemical & Engineering Data Article

DOI: 10.1021/acs.jced.5b00623J. Chem. Eng. Data 2015, 60, 3646−3659

3659