The Vapor Pressure of Mercury

Marcia L. Huber

Arno Laesecke

Daniel G. Friend

NISTIR 6643

 

NISTIR 6643

The Vapor Pressure of Mercury

Marcia L. Huber

Arno Laesecke

Daniel G. Friend

Physical and Chemical Properties Division

Chemical Science and Technology Laboratory

National Institute of Standards and Technology

Boulder, CO 80305-3328

April 2006

U.S. DEPARTMENT OF COMMERCE

Carlos M. Gutierrez, Secretary

TECHNOLOGY ADMINISTRATION

Robert Cresanti, Under Secretary of Commerce for Technology

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

William Jeffrey, Director

 

Table of Contents 

1. Introduction......................................................................................................................1 

2. Experimental Vapor Pressure Data .................................................................................2 

3. Correlation Development.................................................................................................11 

4. Comparison with Experimental Data...............................................................................18 

5. Comparisons with Correlations from the Literature.........................................................23 

6. Detailed Comparisons for the Temperature Range 0 °C to 60 °C.....................................25 

7. Conclusions........................................................................................................................35 

8. References........................................................................................................................36 

Appendix A: Detailed Listing of Experimental Data for the Vapor Pressure of 

Mercury..................................................................................................................42 

Appendix B: Detailed Listing of Supplemental Experimental Data for the Heat 

Capacity of Mercury...............................................................................................56 

iii
The Vapor Pressure of Mercury 

Marcia L. Huber, Arno Laesecke, and Daniel G. Friend 

National Institute of Standards and Technology∗

Boulder, CO 80303-3328 

In this report, we review the available measurements of the vapor pressure 

of mercury and develop a new correlation that is valid from the triple point to the 

critical point. The equation is a Wagner-type form, where the terms of the 

equation are selected by use of a simulated annealing optimization algorithm. In 

order to improve the reliability of the equation at low temperatures, heat capacity 

data were used in addition to vapor pressure data. We present comparisons with 

available experimental data and existing correlations. In the region of interest for 

this project, over the temperature range 0 °C to 60 °C, the estimated uncertainty 

(estimated as a combined expanded uncertainty with coverage factor of 2, 2σ) of 

the correlation is 1 %. 

Keywords: correlation, mercury, vapor pressure. 

1. Introduction 

Recent concerns about mercury as an industrial pollutant have lead to increased 

interest in the detection and regulation of mercury in the environment [1]. The 

development of standardized equations for the thermophysical properties of mercury can 

aid this task. A critical evaluation of density, thermal expansion coefficients, and 

compressibilities as a function of temperature and pressure was conducted by Holman 

and ten Seldam [2]. Bettin and Fehlauer [3] recently reviewed the density of mercury for 

metrological applications. Vukalovich and Fokin’s book [4] and the Gmelin Handbook 

[5] are both thorough treatises on the thermophysical properties of mercury. Thermal 

properties such as thermal conductivity and heat capacity were reviewed by Sakonidou et 

al. [6], while Hensel and Warren [7] cover other properties including optical and 

magnetic characteristics. To assess risks of exposure, it is important to have an accurate 

 

∗ Physical and Chemical Properties Division, Chemical Science and Technology Laboratory. 

1
representation of the vapor pressure of mercury. Numerous compilations and correlations 

of the vapor pressure of mercury have been published [8-25], but there is no consensus 

on which is the best one to use for a given purpose. In this work, we review the existing 

experimental data and correlations, and provide a new representation of the vapor 

pressure of mercury that is valid from the triple point to the critical point. We also 

present comparisons with both experimental data and correlations, and estimate the 

uncertainty of the correlation. 

2. Experimental Vapor Pressure Data 

Experimental measurements of the vapor pressure of mercury have a long history. 

A single vapor pressure point of mercury, the boiling point, was first measured in 1801 

by Dalton [26], who obtained a value corresponding to 622 K; shortly thereafter, in 1803, 

Crichton [27] mentioned that the normal boiling point is above a temperature 

corresponding to 619 K. More recently, the normal boiling point of mercury was 

determined by Beattie et al. [28] as (356.58 ± 0.0016) °C, on the 1927 International 

Temperature Scale. This measurement was selected as a secondary fixed point on the 

ITS-48 Temperature scale [29]. Converted to the ITS-90 temperature scale [30], this 

value is (629.7653 ± 0.0016) K. The value recommended by Marsh [31] is 629.81 K 

(IPTS-68); on the International Practical Temperature Scale [32] of 1968, this was a 

secondary fixed point. Converted to ITS-90, this recommendation is 629.7683 K for the 

normal boiling point. 

Regnault [33] published observations of the vapor pressure of mercury over a 

range of temperatures in 1862. Several of the early publications are by researchers who 

became quite famous, including Avogadro [34], Dalton [26], Hertz [35], Ramsay [36], 

and Haber [37]. Indeed, much of the work on mercury was done in the early part of the 

20th century. Figure 1 shows the distribution of the experimental data. Table 1 gives a 

detailed compilation of sources of vapor-pressure data from 1862 to the present, along 

with the temperature range of the measurements, the experimental method used, and an 

estimate of the uncertainty of these measurements. In general, determinations of the 

purity of the mercury were not available; however, methods for the purification of 

mercury have been known for a long time, and samples of high purity were prepared 

2
before it was possible to quantify the purity [18]. The estimates of uncertainty were 

obtained by considering the experimental method and conditions, the original author’s 

estimates (when available), and agreement with preliminary correlations. These 

correspond to our estimate of a combined expanded uncertainty with a coverage factor of 

two. In Appendix A, we tabulate all experimental data for the vapor pressure of mercury 

collected in this study. 

The experimental techniques used to measure vapor pressure can be grouped into 

three main categories: the static, quasistatic, and kinetic techniques are discussed by 

Dykyj et al. [38] and Ditchburn and Gilmour [14]. One of the simplest methods to 

measure the vapor pressure is a static method that involves placing the sample in a closed 

container, then removing any air and impurities, keeping the vessel at constant 

temperature, and then measuring the temperature and pressure after equilibrium has been 

established. It is generally limited to pressures above 10 kPa. In principle, it is applicable 

to any pressure, but in practice the presence of nonvolatile impurities can cause large 

systematic errors. With very careful sample preparation, it may be possible to go to lower 

pressures with this technique. Another static instrument is the isoteniscope. This type of 

instrument was used by Smith and Menzies [39, 40] in their early work on the vapor 

pressure of mercury. In this type of apparatus, the sample is placed in a bulb that is 

connected to a U-tube that acts as a manometer (i.e., a pressure sensor). The device is 

placed in a thermostat, and the external pressure is adjusted until it equals that of the 

vapor above the sample. Isoteniscopes are limited by the sensitivity of the pressure 

sensor. A third type of static method involves the use of an inclined piston gauge. The 

sample is placed in a cylinder fitted with a movable piston so that the pressure of the 

sample balances the weight (gravitational force) of the piston. This method is generally 

applicable over the range 0.1 kPa to 1.5 kPa. 

Among the instruments classified as quasistatic are ebulliometers and 

transpiration methods. In both of them, a steady rate of boiling is established, and it is 

assumed that the pressure at steady state is equivalent to the equilibrium vapor pressure. 

In an ebulliometer, the sample is boiled at a pressure set by an external pressurizing gas 

(often helium) with the vapor passing through a reflux condenser before returning to the 

boiler. The temperature measured is that of the vapor just above the boiling liquid. An 

3
advantage to this method is that volatile impurities do not condense and are removed at 

the top of the apparatus. This method may also be set up in a comparative mode with two 

separate ebulliometers, one containing a reference fluid and the other containing the 

sample fluid connected with a common pressure line, so that direct measurement of the 

pressure is unnecessary. It is possible to make very accurate measurements with this type 

of device, at pressures greater than about 2 kPa. The very accurate measurements of the 

vapor pressure of mercury by Ambrose and Sprake [18] were made with an ebulliometric 

technique. The transpiration method (also called gas saturation) involves passing a steady 

stream of an inert gas over or through the sample, which is held at constant temperature. 

The pressure is not measured directly, but rather is calculated from converting the 

concentration of the mercury in the gas stream to a partial pressure that is the vapor 

pressure of the sample. This type of method has a larger uncertainty than some of the 

other methods, generally ranging from 0.5 to 5 % [38]. It is most useful over a pressure 

range of 0.1 to 5 kPa. For example, Burlingame [43] and Dauphinee [49,50] used the 

transpiration method in their measurements. 

4
1E-9

1E-61E-3

1E+61E+31E+0

100 300 500 700 900 1100 1300 1500 1700

Temperature, K

 kPa,e essur rP

Regnault 1862

Hertz 1882

Ramsay 1886

Callendar 1891

Young 1891

Cailletet 1897

Pfaundler 1897

Morley 1904

Gebhardt 1905

Smith, Menzies 1910, 1927

Knudsen 1909

Egerton 1917

Ruff 1919

Volmer 1921

Hill 1922

Scott 1924

Bernhardt 1925

Poindexter 1925

Rodebush 1925

Volmer1925

Jenkins 1926

Millar 1927

Neumann 1932

Pedder 1933

von Halban 1935

Beattie 1937

Schneider 1944

Dauphinee 1950

Douglas 1951

Busey 1953

Ernsberger 1955

Spedding 1955

Roeder 1956

Sugawara 1962

Carlson 1963

Schmahl 1965

Morgulescu 1966

Ambrose 1972

Schönherr 1981Triple pointNormal boiling pointCritical point

Figure 1. Experimental vapor pressure data for mercury.

5
Table 1. Summary of available data for the vapor pressure of mercury. References in boldface indicate primary data sets (see text).

First Author Year Method No. pts. T range, K Estimated uncertainty, % 

Ambrose [18] 1972 ebulliometer 113 417-771 less than 0.03, greatest at lowest TBeattie [28] 1937 boiling tube 42 623-636 0.03Bernhardt [41] 1925 3 static methods 27 694-1706 varies from 2 to >15 Bessel-Hagen [42] 1881 Töpler vacuum pump 2 273-293 >20 Burlingame [43] 1968 transpiration 38 344-409 4 Busey [44] 1953 derived from caloric properties 24 234-750 varies from 0.2 to 3.5 at lowest TCailletet [45] 1900 Bourdon manometer 11 673-1154 varies from 1 to 7 Callendar [46] 1891 Meyer tube 2 630 0.2 Cammenga [47] 1969 effusion graphical results 273-325 Carlson [48] 1963 effusion 9 299-549 varies from 3 to >20 Dauphinee [49, 50] 1950,1951 transpiration 18 305-455 5 Douglas [51] 1951 derived from caloric properties 30 234-773 varies from 0.03 (at normal boiling point) 

to 1.5 at lowest T

Durrans [52] 1920 gives table attributed to Smith 

and Menzies[39] 

46 273-723

Egerton [53] 1917 effusion 27 289-309 5 Ernsberger [54] 1955 piston manometer 18 285-327 1Galchenko [55] 1978 static method graphical results 523-723 3 Galchenko [56] 1984 atomic absorption correlating 

equation only 

723-873 3

Gebhardt [57] 1905 boiling tube 9 403-483 8 Haber [37] 1914 vibrating quartz filament 1 293 2 Hagen [58] 1882 differential pressure 5 273-473 >20 Hensel [59] 1966 electrical resistance graphical results 1073-critical not available Hertz [35] 1882 static absolute manometer 9 363-480 5 Heycock [60] 1913 not available 1 630 0.2 Hildenbrand [61] 1964 torsion-effusion 6 295-332 5 Hill [62] 1922 radiometer principle 19 272-308 30 Hubbard [63] 1982 static graphical results 742-1271 not available Jenkins [64] 1926 isoteniscope 21 479-671 0.1 to >20 Kahlbaum [65] 1894 ebulliometer 43 393-493 >10 Knudsen [66] 1909 effusion 10 273-324 varies from 5 to 10 Knudsen [67] 1910 radiometer principle 7 263-298 varies from 5 to 10 

6
Table 1. Continued. 

First Author Year Method No. pts. T range, K Estimated uncertainty, % 

Kordes [68] 1929 temperature scanning 

evaporation method 

2 630-632 4

Mayer [69] 1930 effusion 82 261-298 5, except greater at T<270 McLeod [70] 1883 transpiration 1 293 >20 Menzies [39, 40] 1910,1927 isoteniscope 46 395-708 0.5Millar [71] 1927 isoteniscope 6 468-614 2 Morley [72] 1904 transpiration 6 289-343 varies from 8 to >20 Murgulescu [73] 1966 quasi-static 9 301-549 3 Neumann [74] 1932 torsion balance 19 290-344 6 Pedder [75] 1933 transpiration 3 559-573 2Pfaundler [76] 1897 gas saturation 3 288-372 12 Poindexter [77] 1925 ionization gage 17* 235-293 5-20, greatest at lowest TRaabe [78] 2003 computer simulation 20 408-1575 varies from 0.5 to >20 Ramsay [36] 1886 isoteniscope 13 495-721 varies from 0.3 to 10 at highest TRegnault [33] 1862 isoteniscope 29 297-785 ~6 for T>400, much higher for lower TRodebush [79] 1925 quasi-static 7 444-476 1 Roeder [80] 1956 quartz spiral manometer 7 413-614 2 Ruff [81] 1919 temperature scanning 

evaporation method 

12 478-630 >20

Schmahl [82] 1965 static method 43 412-640 1.5 Schneider [83] 1944 gas saturation 23 484-575 10 Schönherr [84] 1981 electrical conductivity 13 1052-1735 3Scott [85] 1924 vibrating quartz filament 1 293 2 Shpil’rain [86] 1971 ebulliometer 50 554-883 0.6 to 0.8 Spedding [87] 1955 isoteniscope 13 534-630 0.03Stock [88]* 1929 transpiration 3 253-283 20 Sugawara [9] 1962 static method 14 602-930 2 van der Plaats [89] 1886 transpiration 26 273-358 Villiers [90] 1913 ebulliometer 12 333-373 6 Volmer [91] 1925 effusion 10 303-313 3 von Halban [92] 1935 resonance light absorption 1* 255 7 Young [93] 1891 static 11 457-718 2 

* Excludes points below the triple point. 

7
The Knudsen effusion method is a type of vapor pressure measurement classified as a 

dynamic method. In this type of experiment, a steady rate of evaporation through an orifice 

into a vacuum is established, and pressure is calculated from the flow rate through the orifice 

by use of kinetic theory. This method is applicable at very low pressures (below 0.1 kPa), but 

generally has high uncertainties. 

As indicated in Table 1, many measurements have been made on the vapor pressure 

of mercury. However, only a limited number of these are comprehensive and have 

uncertainty levels of one percent or less. These sets have been identified as primary data sets 

in our work and are indicated by boldface type in Table 1. In general, the most accurate 

measurements were those made with ebulliometric methods. Ambrose and Sprake [18] used 

an ebulliometric technique for their measurements from 380 K to 771 K. These data have an 

uncertainty of about 0.03 % or lower, with the largest uncertainty at the lowest temperatures. 

Beattie et al. [28] very accurately determined the boiling point of mercury over the 

temperature range 623 K to 636 K. Spedding and Dye [87] used an isoteniscope to measure 

the vapor pressure over the range 534 K to 630 K, with uncertainties on the order of 0.03 % 

except at the lowest temperatures where they are larger. Menzies [40, 94] used an 

isoteniscope at temperatures from 395 K to 708 K, but these data show more scatter and have 

larger uncertainties than the sets mentioned above; however, the uncertainties are still less 

than 0.5 %. Shpil’rain and Nikanorov [86] used an ebulliometric method extending from 554 

K to 883 K. Their data are more consistent with the measurements of Ambrose and Sprake 

[18] in their region of overlap than are other high temperature sets, such as those by 

Sugawara et al. [9] , Bernhardt [41] or Cailletet et al. [45], and thus were selected as the 

primary data for the high temperature region from about 700 K to 900 K. In addition, 

although the uncertainty is higher than 1 %, we have selected the data of Schönherr and 

Hensel [84] for the highest temperature region, 1052 K to 1735 K. This data set was obtained 

by observing changes in the electrical conductivity. At fixed pressures, the temperature was 

raised, and when a discontinuity was observed, this was taken as an indication of phase 

change. 

All of the sets mentioned so far are for temperatures greater than 380 K. At lower 

temperatures, the measurements are much more uncertain and display significant scatter. In 

the low temperature range, we considered the measurements of Ernsberger and Pitman [54] 

8
to be the most accurate. These measurements were made with an absolute manometer 

method, with uncertainties on the order of 1 %, and they cover the temperature range 285 K 

to 327 K. This data set has been adopted in the metrology community for use in precision 

manometry, and has been described as reliable and confirmed by heat capacity measurements 

[95]. The reliability and thermodynamic consistency of these data will be discussed in more 

detail in a later section of this document. 

The end points of the vapor pressure curve for stable vapor-liquid equilibrium are the 

triple point and the critical point. Metastable points may be obtained at points below the 

triple point. In principle, the three phase-boundary curves that meet at the gas-liquid-solid 

triple point of a pure substance continue beyond this intersection so that the phase equilibria 

become metastable relative to the third phase, which is absolutely stable. Vapor-liquid 

equilibrium along the vapor pressure curve continued below the triple point becomes 

metastable relative to the solid phase, and vapor-solid equilibrium along the sublimation 

pressure curve continued above the triple point becomes metastable relative to the liquid 

phase. Although the former has been realized in experiments [96], metastable phase 

equilibria are one of the least investigated phenomena of the behavior of matter. Their 

existence in principle is mentioned here because three datasets in the present collection 

report mercury vapor pressure data at temperatures below the triple point: Poindexter [77], 

Stock and Zimmermann [88], and von Halban [92]. The farthest reaching data below the 

triple point temperature are the results of Poindexter, covering a range from 194 K to 293 K. 

However, in this work we restrict our study to points above the triple point, although all 

points are tabulated in Appendix A. 

The triple point of mercury has been designated as a fixed point of the ITS-90 [30] 

temperature scale, with a value of 234.3156 K. The critical point has been measured by 

several investigators; these values are listed in Table 2, along with uncertainty estimates 

provided by the authors. One of the first measurements of the critical point was made by 

Koenigsberger [97] in 1912, who made visual observations in a quartz tube and reported the 

critical temperature of mercury to be near 1270 °C (1543 K). This measurement was later 

criticized by Menzies [94] who reported that the critical temperature was at least 1275 °C 

(1548 K). Another early determination was that of Bernhardt [41] who extrapolated his vapor 

pressure observations, and used Bender’s [98] value of 1650 °C (1923 K) for the critical 

9
temperature, while estimating the critical pressure to be in the range 294.2 to 343.2 MPa. 

Later, Birch [99] determined the critical point by observing the changes in electrical 

resistance as a function of temperature at constant pressure. The review paper of Mathews 

[100] adopted Birch’s values for the critical point. Ambrose [101] and also Vargaftik et al. 

[8] instead selected the value obtained by Franck and Hensel [102], also obtained from

studies of changes in electrical resistance. Kikoin and Senchenkov [103] used electrical 

conductivity experiments to locate the critical point, Neale and Cusack [104] observed 

changes in the Seebeck voltage, while Götzlaff [13] analyzed isochoric and isobaric PVT 

data extrapolated to the saturation boundary. Most recently Kozhevnikov et al. [105] 

observed changes in the speed of sound along isobars as a function of temperature to 

determine the critical point. The value by Bernhardt [41] is too high both in pressure and in 

temperature. The critical temperature of Franck and Hensel [102] agrees very well with that 

obtained by Kozhevnikov et al. [105], while the critical pressure of Götzlaff [13] agrees very 

well with that of Kozhevnikov et al. [105] In this work we adopted the critical point of 

Kozhevnikov et al. [105]. 

Table 2. The critical temperature and pressure of mercury.* 

First Author Year Tc (K) pc (MPa) 

Koenigsberger [97] 1912 ~1543 

Menzies [94] 1913 >1548 

Bender [98] 1915 1923 

Meyer [106] 1921 1747 

Bernhardt [41] 1925 1923 294.2 - 343.2 

Birch [99] 1932 1733 ± 20 161 ± 5 

Franck [59, 102] 1966 1763.15 ± 15 151 ± 3 

Kikoin [103] 1967 1753 ± 10 152 ± 1 

Neale [104] 1979 1768 ± 8 167.5 ± 2.5 

Hubbard [107] 1983 1750 172 

Götzlaff [13] 1988 1751 ± 1 167.3 ± 0.2 

Kozhevnikov [105] 1996 1764 ± 1 167 ± 3 

 *Uncertainties are expressed in kelvins and megapascals for the temperature and pressure, 

respectively. 

10
3. Correlation Development 

Numerous expressions have been used to represent the vapor pressure of a pure fluid; 

many are reviewed in Růžička and Majer [108]. Equations of the general form

/ 2 ( / ) ( / ) i

c c i

i

ln p p = T T ∑aτ , (1) 

where τ = 1-T/Tc, are attributed to Wagner [109-112] and have been used successfully to 

represent the vapor pressures of a wide variety of fluids. Lemmon and Goodwin [113] used 

the Wagner form with exponents (1, 1.5, 2.5, and 5) to represent the vapor pressures of 

normal alkanes up to C36. This form, which we will call Wagner 2.5-5, is one of the most 

widely used forms along with the equation with exponents (1, 1.5, 3, and 6) [109, 110], 

which we call Wagner 3-6. The 2.5-5 form has emerged as the generally preferred form

[114]. When the data set is extensive and of high quality, other forms with alternative sets of 

exponents with additional terms have been used. For example, a Wagner equation with 

exponents (1, 1.5, 2, 2.5, and 5.5) was used to represent the vapor pressure of acetonitrile 

[115], and another variant of the Wagner equation, with exponents (1, 1.89, 2, 3, and 3.6), 

was used to represent the vapor pressure of heavy water [116] from the triple point to the 

critical point to within the experimental scatter of the measurements. The International 

Association for the Properties of Water and Steam (IAPWS) formulation for the vapor 

pressure of water [117, 118] uses a six-term Wagner equation with exponents of (1, 1.5, 3, 

3.5, 4, and 7.5). 

Since there is a lack of high-quality experimental vapor-pressure data in the low 

temperature region (T < 285 K), liquid heat capacity measurements at low temperatures can 

be used to supplement the vapor-pressure data [108, 114, 119]. This permits the 

simultaneous regression of heat capacity and vapor-pressure data to determine the 

coefficients of a vapor pressure equation that is valid down to the triple point. An alternative 

method is to use an expression involving enthalpies of vaporization in addition to vaporpressure data [120]. Both of these approaches can be used to ensure that the vapor pressure is 

thermodynamically consistent with other thermodynamic data. 

King and Al-Najjar [119] related heat capacity and vapor pressure using 

11
0

2 ln L d d psat C C p p G

T

dT dT R

⎛ ⎞ − − = ⎜ ⎟ ⎝ ⎠ , (2) 

·K), psat is the vapor 

ressure, and G represents vapor phase nonidealities and is given by 

where Cp° and Cp

L

 are the heat capacities at constant pressure of the ideal gas and the 

saturated liquid, R is the molar gas constant [121] R=8.314 472 J/(mol

p

( )

2 2

2 2 2 sat L sat

sat L

d B dp dB dV d p G T p B V

dT dT dT dT dT

⎛ ⎞ ⎛ ⎞ = + ⎜ ⎟ − + − ⎜ ⎟ ⎝ ⎠ ⎝ ⎠ . (3) 

l

rence in

n of eq

of

above. The smoothed heat capacity data from these two sources are listed in 

In this expression, B is the second virial coefficient and VL is the molar volume of the liquid. 

We restrict the use of this equation to temperatures lower than 270 K, where vapor pressures

are on the order of 10-5 kPa. In this region, we treat the gas phase as ideal so that the G term

may be neglected. (For example, we applied equations in Douglas et al. [51] for the viria

coefficients, liquid volumes, heat capacities, vapor pressures and their derivatives, and 

estimated that the magnitude of the term G at 270 K relative to the heat capacity diffe

eq (2) is on the order 10-4 %.) Assuming that mercury can be considered as an ideal 

monatomic gas for these low pressures, the ideal gas heat capacity for mercury is Cp° = 5R/2 

[122]. With these assumptions, after the derivatives of the vapor pressure in eq (2) are taken

analytically incorporating the specific form of the vapor pressure correlation functio

(1), one obtains the simple expression (5R/2 − Cp

L

)/R = (T/Tc)Σai(i/2)(i/2 − 1)ti/2-1. 

Busey and Giauque [44] measured the heat capacity Cp of mercury from 15 to 330 K 

with estimated uncertainties of 0.1 %. Amitin et al. [123] also measured the heat capacity

mercury at temperatures from 5 K to 300 K, with an estimated uncertainty of 1 %. The 

smoothed data over the temperature range 234 K to 270 K from these two sources were 

identified as primary data for use in the regression, in addition to the primary vapor pressure

data discussed

Appendix B. 

For our analysis of both psat and Cp experimental data, all temperatures were first 

converted to the ITS-90 scale. Data taken prior to 1927 were converted to ITS-90 assuming 

12
that the older data were on the International Temperature Scale of 1927, although we realize 

this introduces additional uncertainties. Except for the data of Menzies [40], all primary data

were measured after 1927. The temperatures of the data of Menzies were first converted to

the 1948 temperature scale by use of the procedure given by Douglas et al. [51] and then

iple

t

e

t the

g the

tive

its were considered outliers and were not included in the statistics and final 

were converted to ITS-90. 

We regressed the primary data set to three different Wagner-type expressions: the 3-

6, the 2.5-5, and a variable exponent expression where the exponents were selected from a 

bank of terms by use of a simulated annealing procedure [124, 125]. Simulated annealing is 

an optimization technique that can be used in complex problems where there may be mult

local minima. It is a combinatorial method that does not require derivatives and does no

depend upon “traveling downhill”; it also is relatively easy to implement. An example 

program using the simulated annealing to solve the Traveling Salesman Problem is given in 

the book by Press et al. [125]. In this work, the search space contained a bank of terms where 

the bank contained exponents with powers of τ in increments of 0.5, with terms up to τ

12. W

followed the recommendation of Harvey and Lemmon [116] and required the equation to 

contain terms of order 1, 1.89, and 2, based on theoretical considerations on the behavior 

near the critical point. The simulated annealing algorithm was used to determine the optimal 

terms from the bank of terms. We implemented a Lundy and Mees [126] annealing schedule, 

similar to that of earlier work [127]. During the regression, one can treat the critical pressure 

as a variable to be determined in the regression, or it can be fixed. Due to concerns abou

quality and amount of experimental data in the temperature range 930 K to 1764 K, we 

adopted the critical point of Kozhevnikov et al. [105] rather than determining it by fitting 

experimental data. The minimization was done with orthogonal distance regression usin

NIST statistical package ODRPACK [128]. For the regression, the data were weighted 

according to their estimated uncertainty (u) with weights of 1/u

2

. In addition, the vapor 

pressure data were given a relative weight factor of one, and the heat capacity data a rela

weight factor of 0.02. Points that deviated by more than three standard deviations from

preliminary f

regression. 

The 2.5-5 form of the Wagner equation provided a better fit of the primary data set 

than the 3.0-6 form; further improvement resulted from the use of the simulated annealing 

13
algorithm. Upon closer inspection, we noted that although one could reasonably reproduce

the numerical value of the heat capacity, it was not possible to reproduce well the slope o

the saturated liquid heat capacity near the triple point without degrading the fit in other

regions. We note that the liquid heat capacity at saturation of mercury as a function of 

temperature displays an interesting behavior—a distinct minimum in the curve is observed

below the normal boiling point, as shown in Figure 2. Douglas et al. [51] noted that other 

liquid metals such as sodium and potassium also exhibit this behavior. Among nonmetals, we

observe that water displays this feature; however, it is not observed in simple hydrocarb

such as linear alkanes. In order to simultaneously fit the vapor pressure and liquid heat 

capacity data, and have the correct behavior of the slope of the heat capacity as a fun

temperature along the saturation boundary, we increased the number of terms in the 

regression

f

ons

ction of

from 5 to 6 and used the simulated annealing algorithm to obtain our final 

equation,

( ) 1.89 2 8 8.5 9

1 2 3 4 5 6 ( / ) ( / ) c c ln p p = + T T a τ a τ τ + a + a τ + a τ + a τ . (4) 

d

r

21] R 

= 8.314 472 J/(mol·K) and the relative atomic mass [129] of mercury, 200.59 g/mol. 

The regressed coefficients and their standard deviations are given in Table 3a, and fixe

parameters for eq (4) are given in Table 3b. Table 4 gives sample values of the vapo

pressure calculated from eq (4) over the temperature range 273.15 to 333.15 K. For 

validation of computer code, more digits than are statistically meaningful are given. For the

calibration community, we also have included in Table 4 the density of saturated mercury

vapor in moles per liter and nanograms per milliliter obtained assuming the ideal gas law 

applies, ρ = p/(R·T). We use the currently accepted values of the molar gas constant [1

14
27.0

27.2

27.4

27.6

27.8

28.0

28.2

28.4

28.6

28.8

200 300 400 500 600 700 800

Temperature, K

Cp, J/(mol·K)

Busey, Giauque 1953

Amitin et al. 1979

Triple point

Normal boiling point

Figure 2. Temperature dependence of the heat capacity of saturated liquid mercury. 

15
Table 3a. Fitted values of the parameters in eq (4) and their standard deviations. 

i ai Std. dev. 

1 - 4.576 183 68 0.0472 

2 -1.407 262 77 0.8448 

3 2.362 635 41 0.8204 

4 -31.088 998 5 1.3439 

5 58.018 395 9 2.4999 

6 -27.630 454 6 1.1798 

Table 3b. Fixed parameters in eq (4). 

Tc (K) pc (MPa) 

1764 167

16
Table 4. Vapor pressure of mercury calculated with eq (4) from 273 K to 333 K. 

T, K t, °C p, MPa 

Ideal gas 

density,† mol/L 

Ideal gas 

density,†

ng/mL T, K t, °C p, MPa 

Ideal gas 

density,† mol/L 

Ideal gas 

density,†

ng/mL

273.15 0 2.698829·10-8 1.188337·10-8 2.383684 304.15 31 4.259045·10-7 1.684185·10-7 33.78306274.15 1 2.979392·10-8 1.307088·10-8 2.621887 305.15 32 4.611495·10-7 1.817581·10-7 36.45885275.15 2 3.286720·10-8 1.436675·10-8 2.881826 306.15 33 4.990473·10-7 1.960527·10-7 39.32620276.15 3 3.623129·10-8 1.577990·10-8 3.165289 307.15 34 5.397770·10-7 2.113631·10-7 42.39732277.15 4 3.991118·10-8 1.731989·10-8 3.474196 308.15 35 5.835283·10-7 2.277535·10-7 45.68508278.15 5 4.393376·10-8 1.899698·10-8 3.810605 309.15 36 6.305024·10-7 2.452917·10-7 49.20305279.15 6 4.832795·10-8 2.082217·10-8 4.176720 310.15 37 6.809117·10-7 2.640489·10-7 52.96556280.15 7 5.312487·10-8 2.280723·10-8 4.574903 311.15 38 7.349813·10-7 2.841004·10-7 56.98770281.15 8 5.835798·10-8 2.496477·10-8 5.007682 312.15 39 7.929493·10-7 3.055255·10-7 61.28535282.15 9 6.406319·10-8 2.730825·10-8 5.477762 313.15 40 8.550671·10-7 3.284075·10-7 65.87527283.15 10 7.027907·10-8 2.985209·10-8 5.988031 314.15 41 9.216005·10-7 3.528344·10-7 70.77506284.15 11 7.704698·10-8 3.261169·10-8 6.541579 315.15 42 9.928302·10-7 3.788986·10-7 76.00327285.15 12 8.441128·10-8 3.560348·10-8 7.141702 316.15 43 1.069052·10-6 4.066972·10-7 81.57939286.15 13 9.241950·10-8 3.884501·10-8 7.791920 317.15 44 1.150580·10-6 4.363324·10-7 87.52391287.15 14 1.011225·10-7 4.235498·10-8 8.495986 318.15 45 1.237743·10-6 4.679116·10-7 93.85838288.15 15 1.105749·10-7 4.615334·10-8 9.257899 319.15 46 1.330888·10-6 5.015475·10-7 100.6054289.15 16 1.208348·10-7 5.026135·10-8 10.08192 320.15 47 1.430383·10-6 5.373585·10-7 107.7888290.15 17 1.319646·10-7 5.470161·10-8 10.97260 321.15 48 1.536613·10-6 5.754690·10-7 115.4333291.15 18 1.440308·10-7 5.949822·10-8 11.93475 322.15 49 1.649985·10-6 6.160093·10-7 123.5653292.15 19 1.571046·10-7 6.467678·10-8 12.97352 323.15 50 1.770928·10-6 6.591162·10-7 132.2121293.15 20 1.712619·10-7 7.026452·10-8 14.09436 324.15 51 1.899890·10-6 7.049329·10-7 141.4025294.15 21 1.865835·10-7 7.629036·10-8 15.30308 325.15 52 2.037347·10-6 7.536097·10-7 151.1666295.15 22 2.031558·10-7 8.278502·10-8 16.60585 326.15 53 2.183795·10-6 8.053040·10-7 161.5359296.15 23 2.210708·10-7 8.978112·10-8 18.00919 327.15 54 2.339760·10-6 8.601806·10-7 172.5436297.15 24 2.404265·10-7 9.731323·10-8 19.52006 328.15 55 2.505789·10-6 9.184118·10-7 184.2242298.15 25 2.613271·10-7 1.054180·10-7 21.14581 329.15 56 2.682462·10-6 9.801783·10-7 196.6140299.15 26 2.838837·10-7 1.141344·10-7 22.89423 330.15 57 2.870385·10-6 1.045669·10-6 209.7507300.15 27 3.082141·10-7 1.235036·10-7 24.77358 331.15 58 3.070193·10-6 1.115081·10-6 223.6740301.15 28 3.344440·10-7 1.335691·10-7 26.79262 332.15 59 3.282555·10-6 1.188620·10-6 238.4253302.15 29 3.627066·10-7 1.443770·10-7 28.96059 333.15 60 3.508170·10-6 1.266503·10-6 254.0478303.15 30 3.931433·10-7 1.559763·10-7 31.28729

† Assumes ideal gas law applies. 

17
4. Comparison with Experimental Data 

For the 294 vapor pressure points in the primary data set, the average absolute 

deviation is 0.14 %, the bias is −0.028 %, and the root mean square deviation is 0.35 % 

where we use the definitions AAD = (100/n)Σabs(pi

calc/ piexpt − 1), BIAS = (100/n) 

Σ(pi

calc/ piexpt − 1), and RMS2

 = (100/n)( Σ(pi

calc/ piexpt − 1)2 − ((100/n) Σ(picalc/ piexpt − 1))2

, 

 where n is the number of points. The AAD and RMS for the primary data are given in 

Table 5. The normal boiling point calculated by this equation is 629.7705 K. 

Figure 3 compares the primary data set with our correlation, eq (4). The data of 

Ernsberger and Pitman [54] display substantial scatter, but the results are within their 

estimated experimental uncertainty of 1 %. The data of Shpil’rain and Nikanorov [86] 

also display a fairly high scatter, but again it is within their uncertainty estimate (0.6 % 

to 0.8 %). The very accurate measurements of Beattie et al. [28] are in the vicinity of the 

normal boiling point, and the correlation, eq (4), indicates an uncertainty of 0.02 %, at a 

coverage factor of 2. The measurements of Spedding and Dye [87] and those of Ambrose 

and Sprake [18] also are represented well by our correlation, although the lowest 

temperature points display larger scatter than at higher temperatures. The measurements 

of Menzies [39, 40] are also represented to within their estimated uncertainty. The 

highest temperature data of Schönherr and Hensel [84] are represented with an AAD of 1 

% and a standard deviation of 1.4 %; several points are outside of the range of the plot 

and are not shown. The correlation is valid to the critical point at 1764 K, but does not 

account for a metal-nonmetal transition [63] in mercury at approximately 1360 K that 

results in a change of slope in the vapor pressure curve. 

 

18
Table 5. Summary of comparisons of the correlation with the primary data for the vapor 

pressure of mercury. 

First author No. 

pts. 

T range, 

K 

Estimated uncertainty, % AAD 

% 

RMS 

% 

Ambrose [18] 113* 417-771 less than 0.03, greatest at lowest T 0.02 0.06

Beattie [28] 42 623-636 0.03 0.01 0.01 

Ernsberger [54] 18 285-327 1 0.33 0.35 

Menzies [39, 40] 46** 395-708 0.5 0.14 0.20 

Schönherr [84] 13 1052-

1735 

3 1.06 1.42

Shpil’rain [86] 50 554-883 0.6-0.8 0.25 0.29 

Spedding [87] 13 534-630 0.03 0.05 0.06 

* Two outliers at 380 K and 400 K were not included in statistics. 

** One outlier at 395 K was not included in statistics. 

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

200 700 1200 1700

Temperature, K

100·[(

p -p eq(4))/p ]

Ambrose, Sprake 1972 Spedding, Dye 1955

Shpil'rain, Nikanorov 1971 Menzies 1910,1927

Beattie et al. 1937 Ernsberger, Pitman 1955

Schönherr, Hensel 1981

Figure 3. Deviations between the correlation given in eq (4) and the primary data set. 

19
Figure 4 compares selected data not used in the regression (secondary data) with 

the correlation eq (4), and Table 6 summarizes comparisons with all secondary data. It is 

interesting to note that the behavior of the correlation at low temperatures falls in 

between the values of Douglas et al. [51] and those of Busey and Giauque [44]. Both of 

these sets were not obtained from direct vapor pressure measurements, but rather were 

calculated based upon caloric measurements combined with vapor pressure data at higher 

temperatures. The data of Schmahl et al. [82] cover a range of temperature from 412 to 

640 K and are in good agreement with the correlation. The measurements of Burlingame

[43] and of Dauphinee [49,50] were made by use of a transpiration technique with 

uncertainties on the order of 4 to 5 %, and the correlation represents them within this 

range of deviations. Figure 4 also displays considerably more scatter at both the high and 

low temperature ends of the plot. 

-10

-8

-6

-4

-2

0

2

4

6

8

10

200 400 600 800 1000

Temperature, K

100·[(

p -p eq(4))/

p ]

Douglas et al. 1951 Burlingame 1968

Busey, Giauque 1953 Dauphinee 1951

Murgulescu, Topor 1966 Schmahl et al. 1965

Sugawara et al. 1962 Volmer, Kirchoff 1925

Roeder, Morawietz 1956 Hildenbrand et al. 1964

Cailletet et al. 1897 Rodebush, Dixon 1925

Egerton 1917 Poindexter 1925

Figure 4. Deviations between the correlation given in eq (4) and selected secondary data. 

20
Table 6. Summary of comparisons of the correlation given in eq (4) with secondary data 

for the vapor pressure of mercury. 

First author No. pts. T range, 

K 

Estimated uncertainty, 

% 

AAD % RMS % 

Bernhardt [41] 27 694-1706 varies from 2 to >15 14.13 17.26 

Bessel-Hagen [42] 2 273-293 >20 96.12 2.50 

Burlingame [43] 38 344-409 4 1.44 1.92 

Busey [44] 24 234-750 varies from 0.2 to 3.5 at lowest T 0.90 1.03

Cailletet [45] 11 673-1154 varies from 1 to7 3.97 2.26 

Callendar [46] 2 630 0.2 0.17 0.14 

Cammenga [47] graphical results 273-325 

Carlson [48] 9 299-549 varies from 3 to >20 19.74 16.83 

Dauphinee [49, 50] 18 305-455 5 2.14 2.94 

Douglas [51] 30 234-773 var. from 0.03 (at normal boiling 

point) to 1.5 at lowest T

0.45 0.54

Durrans [52] 19 290-344 4.63 3.06 

Egerton [53] 27* 289-309 5 6.99 2.34 

Galchenko [55] graphical results 523-723 3 na na 

Gebhardt [57] 9 403-483 8 3.34 4.03 

Haber [37] 1 293 2 1.84 na 

Hagen [58] 5 273-473 >20 51.02 57.44 

Hensel [59] graphical results 1073-critical na na na 

Hertz [35] 9 363-480 5 4.50 1.94 

Heycock [60] 1 630 0.2 0.21 Na 

Hildenbrand [61] 6 295-332 5 2.76 3.16 

Hill [62] 19 272-308 30 29.40 4.38 

Hubbard [63] graphical results 742-1271 na na na 

Jenkins [64] 21 479-671 varies from 0.1 to >20 5.08 5.67 

Kahlbaum [65] 43 393-493 >10 8.89 9.47 

Knudsen [66] 10 273-324 varies from 5 to 10 7.36 1.67 

Knudsen [67] 7 263-298 varies from 5 to 10 7.12 7.64 

Kordes [68] 2 630-632 4 2.59 1.84 

Mayer [69] 82 261-298 5, except greater at T<270 6.72 8.86

McLeod [70] 1 293 >20 77.65 na 

Millar [71] 6 468-614 2 1.27 1.84 

Morley [72] 6 289-343 varies from 8 to >20 17.58 11.82 

Murgulescu [73] 9 301-549 3 1.41 1.56 

Neumann [74] 19 290-344 6 4.63 3.06 

Pedder [75] 3 559-573 2 1.14 0.94

Pfaundler [76] 3 288-372 12 8.06 5.76 

Poindexter [77] 17 235-293 >5-20; greatest at lowest T 28.23 29.19

Ramsay [36] 13 495-721 varies from 0.3 to 10 at highest T 3.23 3.02

Regnault [33] 29 297-785 ~6 for T>400, much higher for 

lower T

24.74 34.03

Rodebush [79] 7 444-476 1 0.53 0.54 

21
Table 6. Continued. 

First author No. pts. T range, 

K 

Estimated uncertainty, 

% 

AAD % RMS % 

Roeder [80] 7 413-614 2 1.00 1.11 

Ruff [81] 12 478-630 >20 22.49 25.78 

Schmahl [82] 43 412-640 1.5 0.70 0.71 

Schneider [83] 23 484-575 10 4.04 5.02 

Scott [85] 1 293 2 1.11 na 

Stock [88] 3 253-283 20 15.05 16.80 

Sugawara [9] 14 602-930 2 1.15 0.95 

van der Plaats [89] 26 273-358 86.65 23.03

Villiers [90] 12 333-373 6 4.76 3.24 

Volmer [91] 10 303-313 3 1.57 1.13 

von Halban [92] 2 220-255 7 8.15 2.21 

Young [93] 11 457-718 2 1.40 1.30 

* One outlier at 288.6 K was not included in statistics. na: not applicable 

22
5. Comparisons with Correlations from the Literature 

Figures 5a and 5b compare correlations and tables for the vapor pressure of 

mercury in different temperature regions obtained in the literature. In these figures we 

define percent deviation as 100·(peq4-pcorr)/peq4, where pcorr is the vapor pressure from

correlations in the literature and peq4 is that obtained from eq (4). We also show the 

estimated uncertainty band of the new correlation, eq (4), by a heavy black line. The 

existing correlations in the literature agree well with each other and with the new 

correlation in the intermediate temperature region from about 400 K to the normal boiling 

point. In this region, there is a fair number of high quality experimental data. At low 

temperatures, the existing correlations differ from each other and some differ from the 

new correlation. As mentioned earlier, there is a paucity of high quality direct vaporpressure measurements in this region, and we feel that simultaneously using low 

temperature heat capacity data allows our new correlation to display the proper behavior 

in the low temperature region. We also had access to newer data that some of the earlier 

correlations did not include. For example, the Lange’s Handbook correlation [130] is 

based upon the International Critical Tables of 1928 [131], while the most recent CRC 

Handbook [132] values are based upon Vargaftik et al. [8], which itself is based upon the 

1972 book of Vukalovich and Fokin [4]. Some earlier editions of the CRC Handbook (for 

example the 57th Ed., 1976-1977, p. D-182) used the values from the International 

Critical Tables of 1928 [131]. Few correlations are applicable for higher temperatures. 

The maximum temperature limit of the Korea Thermophysical Properties Databank 

correlation, KDB [133], is given as 654.15 K. The maximum of the PTB equation [22] is 

930 K; these correlations should not be extrapolated outside of their given ranges. At the 

highest temperatures, there are considerable differences among the various correlations; 

however, there is also a lack of experimental measurements in this region. The de Kruif 

correlation [20, 21] does not specifically state the temperature limits of the correlation, 

but the very thorough literature survey in the thesis [20] indicates that the only high 

temperature data used in their work were those of Bernhardt [41] and Cailletet et al. [45], 

and they did not have access to the more recent measurements of Shpil’rain and 

Nikanorov [86], Sugawara et al. [9], or Schönherr and Hensel [84]. Lange’s Handbook 

[130] includes a note in their table identifying 900 °C as the critical point; this model 

23
deviates substantially from the other correlations at high temperatures. The DIPPR [134] 

and Yaws [135] correlations appear indistinguishable on the plot, and both have adopted 

a critical point of 1735 K and 160.8 MPa. Our correlation agrees very well with these 

correlations up to about 1500 K, where the differences are probably due to the critical 

point adopted in the correlations. Also, the correlation of Schmutzler (as presented in 

Götzlaff [13]) adopts a different critical point from the selection here; it uses Tc = 1751 K 

and pc = 167.3 MPa. We note that the tabulated values in the book by Hensel and Warren 

[7] appear to have been generated from the Schmutzler [13] correlation. 

-10

-8

-6

-4

-2

0

2

4

6

8

200 250 300 350 400 450 500 550 600

Temperature, K

100·[(

p -p eq(4))/p eq(4)]

de Kruif

KDB

CRC

DIPPR/Yaws

Lange's

Schmutzler

PTB

Triple point

Figure 5a. Comparison of the new correlation, eq (4), with previous compilations and 

correlations in the low temperature region up to 600 K. The uncertainty band for eq (4) is 

indicated by a heavy black solid line. 

24
4

(4

0 )] -10

-8

-6

-4

-2

600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

Temperature, K

100·[(

p -p eq(4)

2

)/p eq

de Kruif

KDB

CRC

DIPPR/Yaws

Lange's

Schmutzler

PTB

Normal boiling point

Critical point

Figure 5b. Comparison of the new correlation, eq (4), with previous compilations and 

correlations in the high temperature region from 600 K to the critical temperature. The

uncertainty band for eq (4) is indicated by a heavy black solid line. 

6. Detailed Comparisons for the Temperature Range 0 °C to 60 °C 

The temperature range from 0 °C to 60 °C is of particular interest for this pro

Unfortunately, in this region there are very few vapor pr

ject.

essure data of high accuracy. Our

e Figure

ta

approach, as detailed above, was to identify the data sets of highest quality and 

supplement the vapor pressure data with low-temperature heat capacity data to improve 

the behavior of the correlation at low temperatures and to ensure thermodynamic 

consistency. The data of Ernsberger and Pitman [54] are the only direct vapor pressure 

measurements of low uncertainty (1 %) available in this region, and were the only lowtemperature vapor pressure data used in the regression. Figure 6a shows the deviations of 

all data with estimated uncertainties of 3 % or less in this temperature range, whil

6b shows comparisons with all sets with estimated uncertainties of 6 % or less. The da

25
of both Busey and Giauque [44] and Douglas, Ball and Ginnings [51] were not direct 

measurements but rather were values obtained from their analysis of heat capacity dat

Our correlation does not agree with these sets to within their estimated uncertainties; 

neither do

a.

the sets agree with each other to within these uncertainties. The single data

point of Scott [85] at 293 K, determined with a quartz fiber manometer with an estimated 

timated 

uncertainty and are represented well by the correlation. 

Figure 7 compares correlations in the literature with eq (4) for the temperature 

range 273 K to 333 K (0 °C to 60 °C). There are four correlations that agree with eq (4) 

to within our estimated uncertainty of 1 %: those by de Kruif [20, 21], DIPPR [134], 

Yaws [135], and Mukhachev et al. [16]. Yaws [135] does not state the uncertainty of his 

equation; however the DIPPR [134] equation reports an estimated uncertainty of less than 

3 %, and the two correlations are almost indistinguishable from one another. The DIPPR 

correlation was developed by fitting vapor pressure data, with a primary data set 

consisting of 54 experimental points from Ambrose and Sprake [18] for temperatures 

from 426 K to 771 K, nine smoothed points from the correlation of Stull [11] for 399 K 

to 596 K, and 81 points from the tables in Vargaftik [136] for temperatures 273 K to 

1073 K [137]. The correlation of de Kruif [20, 21] was developed by use of the method 

uncertainty of 2 %, is represented by our correlation within this margin. The 

measurements of Volmer and Kirchoff [91] have a slightly higher (3 %) es

of Clark 

26
-6

-2

0

2

4

6

273 283 293 303 313 323 333

Temperature, K

10

0·[(

p -p eq(4))/ eq(4)] -4

p

Douglas 1951

Ernsberger 1955

Busey 1953

Volmer 1925

Scott 1924

Figure 6a. Comparison of the new correlation, eq (4), in the temperature range 273 K to 

333 K, with experimental data with estimated uncertainties of 3 % or less. 

-20

-15

-10

-5

0

273 283 293 303 313 323 333

Temperature, K

10

0·[(

p -p eq(4))/p

5

eq(4)

10

15

20

]

Douglas 1951

Ernsberger1955

Busey 1953

Hildenbrand 1964

Mayer 1930

Volmer 1925

Scott 1924

Neumann 1932

Knudsen 1909

Knudsen 1910

Poindexter 1925

Figure 6b. Comparison of the new correlation, eq (4), in the temperature range 273 K to 

333 K, with experimental data with estimated uncertainties of 6 % or less. 

27
-10

-8

-6

-4

-2

0

2

4

6

100·[(

p -p eq( ))/

p eq(4)]

273 283 293 303 313 323 333

Temperature, K

4

CRC, 2004 edition

de Kruif 1971

Yaws 1999

KDB 2005

Lange's/ ICT 1928

Götzlaff 1988

PTB 1995

DIPPR 2004

Mukhachev 1965

ASTM D6350

Figure 7. Comparison of the new correlation, eq (4), in the temperature range 273 K to 

333 K, with correlations from the literature. 

and Glew [138] that, in addition to vapor pressure data, used supplementary data such as 

heat capacities, Gibbs free energies of vaporization and enthalpies of vaporization to 

develop the correlation. The curve from the CRC Handbook, 85th Edition is based on 

that of Vargaftik et al. [8], which itself is based upon Vukalovich and Fokin [4]. The 

Vukalovich and Fokin [4] source lists the data used in the development of the equation, 

and apparently they were unaware of the data of Ernsberger and Pitman [54]. As 

mentioned earlier, Ernsberger and Pitman [54] give an estimated uncertainty of 1 % for 

s

al 

oiling point of mercury. The KDB correlation [133] is presented only as a set of 

their measurements, and they seem to be the most reliable vapor pressure measurement

in the 0 °C to 60 °C range. The Mukhachev et al. [16] correlation was developed from

caloric data such as heat of vaporization and heat capacities along with the norm

b

28
coefficients with a range of applicability, and we do not know the data used in its 

development; it is consistently lower than our correlation. The PTB curve [22], with a 

reported maximum uncertainty of 4 %, is very different in shape from all the others 

investigated. This analysis did not incorporate caloric data, and the experimental data in 

the 0 °C to 60 °C range that were used in the regression were those of Poindexter [77] 

and Neumann and Völker [74]. The equation recommended in the ASTM Standard 

D6350 [139] is presented in terms of a concentration in nanograms per milliliter. We

converted the expression to vapor pressure by applying the ideal gas law and using

relative molar mass [129] of 200.59 and gas constant [121] R = 8.314472 J/(mol·K). It

agrees well with the values from Lange’s Handbook [130]. The curve from Lange’s

Handbook [130] deviates the most from our correlation, approaching 10 % at 273 K, and

gives vapor pressures that are lower than all the other correlations. The curve in Lange’s 

Handbook [130] is based upon the 1928 International Critical Tables (ICT) [131] and w

developed with only the limited data and computational methods available at that time. 

Since it has been used extensively in handbooks and in industrial standards,

further discussion of the 1928 International Critical Tables is warranted. A total of 28 

references are given for the 1928 International Critical Tables, with the most recent date

1926. In addition, some of these references are not original data but rather analysis of 

literature data [17, 140-143], and only 8 of the references [53, 66, 67, 72, 76, 77, 85, 90] 

contain data in the range 273 K to 333 K. Details are not given concerning how the data 

were weighted or the uncertainties of the numbers presented, and it is difficult to know 

the exact procedure used to obtain the values in the table. However, it was not 

uncommon, prior to the widespread use of computers, to employ graphical methods. For 

example, Stull [11] in 1947 states, “the analytical meth

a

as

d

od...was based on semilogarithmic 

es

charts measuring 30 × 42 inches (where 1 mm. = 1° C) and colored map tacks 

representing the plotted points over which a taut thread was stretched.” Comparisons 

with the data cited in the International Critical Tables (Figure 8) indicate that the valu

of the 1928 International Critical Tables (ICT) [131] in the range 0 °C to 60 °C are in 

closest agreement with the 1909 data of Knudsen [66]. Figure 8 shows the percent 

deviations from eq (4) for all of the data cited in the 1928 ICT, the ICT values [131], and

the data of Ernsberger and Pitman [54]. The 1955 data of Ernsberger and Pitman [54] 

29
were not available to the authors of the ICT Table; however, it is the primary data

we used in the low temperature region. In addition, Ernsberger and Pitman [54] noted 

that although the ICT tables are given to four significant figures, the uncertainty

probably 5 to 10 % due to the uncertainties in the measurements upon which the ICT

table for mercury is based. Further discussion on the Knudsen [66] data follows

appears that the ICT tables agree most closely with this particular data set. 

source

is

since it

-20

-10

0

10

20

30

40

50

60

270 280 290 300 310 320 330

Temperature, K

10

0·[(

p -p eq(4))/ eq(4)] p

ICT 1928

Egerton 1917

Haber 1914

Hill 1922

Knudsen 1910

Knudsen 1909

Morley 1904

Pfaundler 1897

Poindexter 1925

Scott 1924

Villiers 1913

Ernsberger 1955

Figure 8. Comparison of the new correlation, eq (4), in the temperature range 273 K to 

333 K, with data cited in the references for the 1928 International Critical Tables (ICT) 

[131], the values in the 1928 ICT, and the data of Ernsberger and Pitman [54]. 

The vapor pressure data of Knudsen [66] were obtained in 1909 using an effusion 

method. In fact, it was the very first measurement of this type, and the method is now 

often called “the Knudsen effusion method” or “the Knudsen method.” Several variants 

of this method have been developed and have been in continuous use from 1909 until the 

present day. Cater [144] discussed the state of the art in of the effusion method in 1978; 

as recently as 2006, Zaitsau et al. [145] used the Knudsen method to measure the vapor 

30
pressure of ε-caprolactam. The basic method developed by Knudsen involves the flow 

e or tube. With a known orifice size 

and geometry, one can measure the flow rate and calculate the vapor pressure with 

equations based on kinetic theory. The measurements that Knudsen made in 1909 were 

done very carefully. One measurement at 0 °C took 13 days to complete—his method of 

detection was to condense the effusing mercury vapor and measure its volume at room

temperature in a capillary tube located below the condenser. However, even today, with 

state of the art equipment, estimated uncertainties for mass-loss Knudsen effusion 

methods are about 5 % [146, 147] for pressures on the order of 10-1 Pa to 1 Pa. EPA 

guidelines [148] give an estimated repeatability of 10 % to 30 % for mass-loss effusion 

methods for the pressure range 10-3 Pa to 1 Pa. Measurements at such low pressures are 

difficult; some factors that can contribute to the uncertainty are temperature measurement 

and control, determination of the weight-loss, and knowledge of the orifice geometry. For 

finite orifice lengths, the geometry must be well known in order to compute the Clausing 

re is a 1 % uncertainty associated with the direct 

manometric method of Ernsberger and Pittman [54]. 

One can also demonstrate that the ICT Tables, apparently based on the data of 

Knudsen [66], are thermodynamically inconsistent with low temperature heat capacity 

data. Figure 9a shows comparisons of the calculated and experimental values of heat 

capacity, and Figure 9b compares the experimental and calculated values for the vapor 

pressure using the present vapor pressure equation eq (4). Sakonidou et al. [6] reviewed 

the availability of heat capacity data for mercury and identified three major sets of heat 

capacity data for the low temperature (below 60 °C) region: Busey and Giauque [44] (0.1 

% uncertainty), Douglas et al. [51] (1 % uncertainty) and Amitin et al. [123](1 % 

uncertainty). These sets of heat capacity data are represented to within their experimental 

uncertainties, as are the vapor pressure data of Ernberger and Pitman [54] (1 % 

uncertainty). The Knudsen data [66] are represented to within 5 % to 10 %, a level 

consistent with the effusion technique, with the highest deviations at the lowest 

temperatures. Therefore, our equation represents all of these data sets to within their 

of vapor from a space where it is in equilibrium with a solid or a liquid at a known 

temperature into a high vacuum through a fine hol

factor, which corrects for the fact that some molecules may strike the orifice wall and be 

returned to the cell [144]. In contrast, the

31
uncertainties, and the heat capacity data are thermodynamically consistent with the vapor 

pressure data. However, if one refits the vapor pressure equation, but instead of using the 

n

o longer possible to represent the heat capacities to

within their experimental uncertainty, as shown in Figure 10a. This indicates that the 

Knudsen data, at a 2 % uncertainty level, are thermodynamically inconsistent with the 

heat capacity measurements. Therefore the 1928 ICT Tables, that represent the Knudsen 

data to better than 2 %, are thermodynamically inconsistent with the heat capacity 

measurements of Busey and Giauque [44], Douglas et al. [51], and Amitin et al. [123]. To 

summarize, the effusion data of Knudsen [66] can be assigned a temperature-dependent 

uncertainty of 5 % to 10 %; any attempt to ascribe a smaller uncertainty to this data set 

would be inconsistent with the more recent data of Ernsberger and Pitman [54], Busey 

and Giauque [44], Douglas et al. [51], and Amitin et al. [123]. 

data of Ernsberger and Pitman [54] as primary data, one instead uses the data of Knudse

[66], and adjusts the weights so that the resulting vapor pressure equation represents the 

Knudsen data to within 2 %, it is n

32
2.0

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

100(

Cp exp-C pcal)/

Cp exp

230 240 250 260 270 280 290 300 310

Temperature, K

Busey and Giauque (1953)

Amitin et al. (1979)

Douglas et al. (1951)

Figure 9a. Comparison of heat capacities calculated with the present correlation, eq (4) 

and eq (2), with experimental heat capacity data. 

-10

-8

-6

-4

-2

0

270 280 290 300 310 320 330

Temperature, K

100 (p exp-p cal)/p exp

2 Ernsberger and Pitman (1955)

Knudsen (1909)

Figure 9b. Comparison of vapor pressures calculated with the present correlation, eq (4), 

with experimental vapor pressure data. 

33
-4

-3

-2

-1

0

1

2

3

230

Busey and Giauque (1953)

Amitin et al (1979)

Douglas et al. (1951)

p p ca ex l)/Cp exp-Cp 100(

C

240 250 260 270 280 290 300 310

Temperature, K

Figure 10a. Comparison of heat capacities calculated with eq (1) and eq (2), subject to

the constraint that the vapor pressure data of Knudsen be represented to within 2 %, with 

experimental heat capacity data. 

-2

0

2

4

6

8

10

Knudsen (1909)

Ernsberger and Pitman (1955)

p exp )/ -p cal (p exp 100

270 280 290 300 310 320 330

Temperature, K

Figure 10b. Comparison of vapor pressures calculated with eq (1) and eq (2), subject to 

the constraint that the vapor pressure data of Knudsen be represented to within 2 %, with

experimental vapor pressure data. 

34
7. Conclusions 

We developed a new correlation for the vapor pressure of mercury that is valid 

 the triple point [30], 234.3156 K to the critical point [105], 1764 K using a 

of the uncertainties of these data as discussed above. The estimated uncertainty at a 

coverage factor of two varies from 3 % near the triple point to 1 % for temperatures from

273 K ture region from 400 K to the 

al boiling point at 629.77 K; for tem

int

sti

s

are 26-

de

this pro

REP

T

Guest R

Harvey

from

Wagner-type equation. We have determined the uncertainties to be associated with the

equation through our comparisons with the primary experimental data and consideration 

to 400 K; 0.15 % for the intermediate tempera

norm peratures above the normal boiling point but 

below about 900 K it is 0.5 %; and for temperatures between 900 K and the critical po

we e mate the uncertainty is about 5 %. The new correlation gives a normal boiling 

point (101.325 kPa) of 629.77 K. 

This project was supported in part by the Western Research Institute, and wa

prep d with the support of the U.S. Department of Energy, under Award No. DE-FC

98FT40323. However, any opinions, findings, conclusions, or recommendations 

expressed herein are those of NIST and do not necessarily reflect the views of the DOE. 

We thank the staff of the Department of Commerce Boulder Laboratories Library for 

their dication and cheerful assistance in obtaining the historic literature necessary for

ject, and Dr. Harro Bauer (Physikalisch-Technische Bundesanstalt,

Braunschweig, Germany) for providing us with a copy of ref. [22]. We thank NIST P

student Justin Chichester for assistance with the preparation of this manuscript and NIS

esearcher Ilmudtin Abdulagatov for assistance with Russian literature. We also 

acknowledge helpful discussions with our NIST colleagues Mark McLinden, Allan 

, and Gerald Mitchell, and with Dr. John Schabron of the Western Research 

Institute. 

35
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V icients n ercury

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Je

ex

A new ining the vapour-density of m ta rs, and

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] Product Properties Test Guidelines, OPPT a e rt ,

 Office of Prevention, Pesticides and Toxic S

41
Appendix A. Detailed Listing of Experimental Data for the Vapor Pressure of

ercur

Al eratures have been converted to ITS-90. Data are arranged alphabetically by first 

au

Da brose and Sprake [18] 

T, p, kP T, K p, kP

M y

l temp

thor.

ta from Am

T, K p, kPa K a a

379.934 0.046 681.168 237.992 635.136 111.503 

400.340 685.426 253.9 636.491 114.202 

 702.724 327.8 621.615 87.311 

 711.623 371.9 623.249 89.986 

 726.554 456.6 92.662 

 739.690 543.0 95.342 

 749.788 617.8 98.055 

 771.124 802.5 100.770 

451.381 1.101 481.650 3.023 630.924 103.440 

488.128 3.689 632.343 106.101 

4 494.925 4.522 633.750 108.792 

 500.619 5.339 635.136 111.504 

 506.657 6.342 636.492 114.202 

 513.690 7.708 621.622 87.323 

 520.258 9.205 623.266 90.010 

 526.171 10.753 624.853 92.671 

 533.782 13.074 626.418 95.353 

 541.589 15.879 627.958 98.060 

546.934 18.080 629.466 100.764 

555.219 21.998 630.924 103.441 

562.504 26.013 632.343 106.101 

572.032 32.173 633.750 108.794 

2 579.202 37.584 635.130 111.489 

3 587.994 45.215 636.492 114.202 

71 53.760 621.625 87.331 

623.267 90.014 

597.320 54.686 612.930 74.144 624.855 92.672

605.650 64.484 621.863 87.728 626.413 95.348

611.991 72.866 628.996 99.929 627.951 98.043 

6 7 629.758 101.311 629.465 100.764 

6 8 630.156 102.037 630.923 103.440 

628.883 99.711 621.619 87.316 632.342 106.098 

629.949 101.643 623.258 90.004 633.747 108.789 

624.850 92.667 635.135 111.501 

6 100.600 626.421 95.363 636.488 114.195 

121.141 627.960 98.061 

133.558 629.464 100.768 

654.707 155.987 630.923 103.440 

663.194 179.295 632.340 106.099 

671.779 205.659 633.748 108.792 

0.139 33

417.095 0.293 08

426.204 0.424 75

432.281 0.538 09 624.850 

439.292 0.706 39 626.410 

441.719 0.774 83 627.956 

447.681 0.964 26 629.467 

454.121 1.213 

56.320 1.309 

462.634 1.627

469.182 2.024

474.565 2.414

479.040 2.784

485.150 3.369

491.856 4.128

497.530 4.882

533.454 12.965

541.345 15.780

549.473 19.193

554.721 21.742

562.759

572.231

6.162

2.313

579.977 38.203 596.4

589.082 46.244 605.005 63.675 

21.14 86.564

27.80 97.795

638.367 118.032

29.365

639.863

645.494

42
Data from Beattie, Blaisdell, and Kaminsky [28]

T, K p, kPa T, K p, kPa T, K p, kPa 

629.7632 101.325 635.6476 112.492 631.1879 103.940 

629.7648 101.325 635.4589 112.121 632.6278 106.646 

634.1509 109.565 633.9426 109.160 

632.8014 106.976 634.9149 111.047 

631.4044 104.344 633.6486 108.587 

629.7663 101.325 629.9633 101.688 632.2578 105.943 

628.4226 98.8973 630.6593 102.963 

624.5575 92.1883 626.8527 96.1257 629.1704 100.244 

4 625.3936 93. 627.6159 97.4703 

623.2927 90. 626.0489 94.7299 

623.0797 89. 624.5171 92.1186 

624.9884 92. 622.9920 89.5730 

626.7624 95.9670 

628.2268 98.5483 

629.7562 101

Data from Bern

p kPa T, p, T, K p, kPa 

629.7666 101.325 

629.7676 101.325 

629.7632 101.325 

622.9608 89.5232

626.0545 94.739 6046

627.6855 97.5908 0733

629.0765 100.075 7188

630.5802 102.819 9141

632.0069 105.472

633.4298 108.168

634.7126 110.655 .312

T, K 

hardt [41]

, K kPa

693 343.2 1074 9807 1619 125500 

693 313.8 1114 12750 1663 146100 

1174 14910 1674 155900 

1199 16670 1685 164400 

1368 46090 1685 173600 

1488 88260 1685 181400 

1553 104000 1706 198100 

1608 105400 

1614 111800 

1619 118700 

Dat ess ]

743 568.8

753 519.8

794 980.7

794 1079

844 1618

854 1471 

944 3334

1004 6865

a from B el-Hagen [42

T, K p, kPa 

273 0.00197 

293 0.00268

43
Data from Burlingame [43] 

Dat usey que [44]

Data

a from B and Giau

Data from Cailletet , Colardeau, and Rivìere [45] 

from Callendar and Griffiths [46] 

T,K p, kPa

629.79 101.325 

629.95 101.325 

T, K p, kPa T, K p, kPa T, K p, kPa 

377.2 4.560·10-2 408.9 2.045·10 473.6 2.318 -1

377.1 4.613·10-2 473.6 2.321 

343.6 7.186·10-3

343.6 6.999·10-3

343.7 7.146·10-3

343.6 7.146·10-3

343.7 7.039·10-3

343.7 7.093·10-3

473.6 2.314 

473.6 2.353 -1 473.6 2.333 

473.6 2.337 

1 

2 

2 

T p, kPa 

443.2 8.126·10-1

377.1 4.546·10-2 443.2 8.069·10-1

377.0 4.613·10-2 443.2 8.083·10-1

377.0 4.560·10-2 443.2 8.162·10-1

377.1 4.506·10-2 443.2 8.194·10-1

377.2 4.426·10-2 473.5 2.297

377.1 4.613·10-2 473.5 2.306

408.9 2.074·10-1

408.9 2.070·10-1

408.8 2.122·10

408.8 2.134·10-1

4

408.8

08.9 .971·10-1 473.6 2.341 

2.038·10 473.6 -1 .316

408.9 2.042·10-1 473.6 .322

T, K p, kPa , K 

234.32 3.07·10-7 500.01 5.256 

2 2 525.02 1.044·101

 550.03 1.947·101

 575.03 3.429·101

-4 600.04 5.757·101

3 2 625.04 9.274·101

 629.92 1.013·102

 650.03 1.437·102

 675.03 2.156·102

 700.02 3.140·102

725.01 4.452·102

750.00 6.165·102

p T, K p, kPa 

50.02 .24·10-6

275.00

298.15 2.67

3.31·10

·10

-5

-4

299.98 3.11·10

24.98 .05·10-3

-2 349.97 1.03·10 -2 374.97 4.144·10

399.98 1.397·10-1

424.99 4.077·10-1

449.99 1.054 

475.00 2.458 

T, K p, kPa T, K , kPa 

673 2.13·102 924 3. 1154 1.64·104 45·103

723 4.31·102 974 5. 

7. 

1. 3 10 1.03 

874 2.26·103 1124 1.393·104 

07·103

774 8.11·102 1024 30·103

824 40·10 74 ·104

44
Data from Carlson, Gilles and Thorn [48] 

T, K p, kPa T, K p, kPa 

3 3. -4 4 2 -1 01.38 5064·10 06.28 .718·10

324.08 1.947·10-3 448.29 1.652

336.97 4.626·10-3 499.21 8.371

348.27 9.306·10-3 548.83 3.145·101

372.17 4.226·10-2

Data from Dauphinee [49, 50]

T, K p, kPa T, K p, kPa 

454.88 1.2407 345.08 7 -3 .44739·10

444.55 8 1 -2

6 361 31 2.00317·10-2

396.41 1.1984·10-1 405.29 1.7885·10-1

-1 483.27 3.2547 

4 2. -1 5

3.6 0-1 -3

5.8 0-1 -4

1.7 - -4

Dat ougl nd Ginnin s [51]

T, K p, kPa 

.6353·10-1 353.45 .26496·10

382.91 .0968·10-2 .

405.17 1.6799·10

13.90 5794·10 13.53 7.7820

421.97 650·1 332.82 3.4624·10

433.36 142·1 314.02 9.2179·10

323.72 8119·10 3 305.00 4.1703·10

a from D as, Ball, a g

T, K p, kPa T, K p, kPa 

234.30 2.921·10-7 413.13 2.4663·10-1 6.1319·102 7.4557·101

253.17 3 6.2977·102 1.0133·102

2 6.3318·102 1.0772·102

1 47 15 2.3029 6.5318·102 1.52074·102

298.14 2.580·10-4 493.16 4.2859 6.7318·102 2.10201·102

313.13 8.453·10-4 513.17 7.5902 6.9317·102 2.85011·102

 533.17 1.2863·101 7.1317·102 3.79714·102

3 1. -2 5 2. 1 7.331 4.97

3 3 7.53 6.43

1 5 7.73 8.19

Dat gerto

T p,

.114·10-6 433.14 5.5722·10-1

273.15 .661·10-5 453.15 1.1697

293.14 .691·10-4 3.

333.12 3.4728·10-3

53.12 2126·10 53.18 0963·10 6·102 80·102

373.12 .6944·10-2 573.18 .2986·101 15·102 00·102

393.13 .0028·10-1 593.19 .0299·101 15·102 32·102

a from E n [53]

T, K p, kPa T, K p, kPa , K kPa

306.83 5.320·10-4 298.04 2.426·10-4 308.53 5.573·10-4

306.93 5.026·10-4 295.86 2.0 -4 29 1.68

2.0 -4 30 5.06

5.5 -4 30 5.54

5.5 -4 30 5.54

5.5 -4 30 5.54

1.6 -4 30 5.54

2.0 -4 30 5.57

2.0 -4 

5. 

23·10 4.14 0·10-4

307.43 5.226·10-4 295.86 23·10 7.23 6·10-4

307.18 5.146·10-4 308.23 46·10 8.33 6·10-4

288.64 8.613·10-5 308.53 73·10 8.33 6·10-4

307.33 4.880·10-4 308.53 73·10 8.33 6·10-4

273.15 2.520·10-5 294.14 80·10 8.33 6·10-4

301.73 3.373·10-4 295.86 13·10 8.53 3·10-4

298.04 2.386·10-4 295.86 13·10

301.73 3.293·10-4 308.23 546·10-4

45
Data from Ernsberger and Pitman [54] 

T, K p, kPa T, K p, kPa 

285.22 8.453·10-5 315.15 9.949·10-4

288.15 1.113·10-4 318.17 1.242·10-3

291.10 1.448·10-4 321.15 1.539·10-3

294.11 1.852·10-4 324 12 1.90 10-3

297.22 2.412·10-4 326.63 2.260·10-3

-4 293.24 1.735·10-4

3 3 2 2

Dat ebh

T, K p, kPa T, K p, kPa 

. 0·

300.25 3.116·10

03.18 .934·10-4 96.22 .226·10-4

306.17 5.005·10-4 299.20 2.865·10-4

309.23 6.358·10-4

312.11 7.929·10-4

a from G ardt [57]

403.13 1.47·10-1 453.15 1.23 

4 2 463.15 1.73 

 473.15 2.36 

 483.16 3.20 

443.14 8.40·10-1 

Data from Haber and Kerschbaum [37] 

T, K p, kPa 

13.13 .40·10-1

423.13 3.73·10-1

433.14 5.73·10-1

293.142 1.680·10-4

Data from Hagen [58] 

T, K p, kPa 

273.15 2.00·10-3

323.13 5.60·10-3

373.12 2.80·10-2

423.13 2.56·10-1

473.15 2.126 

Data from Hertz [35] 

T, K p, kPa T, K p, kPa 

362.52 2.13·10-2 457.85 1.472 

390.13 9.47·10-2 463.55 1.719 

427.34 4.65·10-1 476.15 2.713 

438.94 7.36·10-1 480.06 3.010 

450.54 1.09 

Data from Heycock and Lamplough [60] 

T, K p, kPa 

628.89 101.325 

Data from Hildenbrand, Hall, Ju and Potter [61] 

T, K p, kPa T, K p, kPa 

295.4 2.08·10-4 295.0 2.10·10-4

296.8 2.26·10-4 299.8 3.05·10-4

297.0 2.33·10-4 331.6 3.01·10-3

46
Data ill [62]

p

from H

T, K , kPa T, K p, kPa 

272.45 4.40·10-5 297.14 3.49·10-4

278.85 7.

1.

1.

1.

1.

2.

3.

2.

3. 

Data nkins [

p

33·10-5 298.14 3.64·10-4

284.54 23·10-4 298.73 3.89·10-4

284.74 15·10-4 299.93 4.19·10-4

284.74 09·10-4 301.73 4.93·10-4

286.14 29·10-4 303.03 5.43·10-4

293.44 49·10-4 303.93 5.67·10-4

295.94 07·10-4 307.43 7.17·10-4

296.14 99·10-4 308.03 7.67·10-4

296.14 13·10-4

from Je 64]

T, K , kPa T, K p, kPa 

479.16 2.27 600.19 5.56·101

493.66 3.80 

1

1

1

2. 1

3 1

3 1

4

ata from Kahlbaum [65] 

T, K p, kPa T, K p, kPa 

604.19 6.07·101

511.17 6.47 615.19 7.76·101

520.67 8.27 623.19 8.85·101

526.17 .01·101 631.19 1.03·102

532.67 .21·101 637.71 1.16·102

549.68 .85·101 643.74 1.27·102

561.68 513·101 653.77 .508·102

576.68 .56·101 664.31 .789·102

581.68 .79·101 670.83 .987·102

589.69 .47·101

D

T, K p, kPa

3 1.1 427.34 4.64·10-1 92.53 6·10 459.05 1.527 -1

397.83 1. 432.24 5.64·10-1 464.25 1.797 

399.03 1.68·10 434.24 5.85·10-1 466.25 1.867 

404.23 2.81·10-1 435.74 6.17·10-1 469.85 2.212 

407.23 2.21·10-1 438.24 6.83·10-1 472.55 2.332 

408.13 2.43·10-1 441.84 8.03·10-1 474.95 2.549 

411.73 2.93·10-1 446.24 1.01 477.95 2.805 

413.33 3.53·10-1 448.34 1.04 479.06 2.864 

414.83 3.13·10-1 449.44 1.05 482.06 3.097 

417.43 2.67·10-1 449.94 1.09 483.76 3.357 

418.33 3.81·10-1 450.04 1.05 487.46 3.836 

420.23 3.69·10-1 452.75 1.17 489.76 4.117 

421.33 3.96·10-1 454.05 1.26 492.96 4.573 

422.13 4.25·10-1 454.75 1.25 

424.64 4.37·10-1 456.15 1.409 

83·10-1

-1

47
Data from Knudsen [67] 

T, K p, kPa T, K p, kPa 

263.16 1.10·10-5 288.84 1.14·10-4

273.15 2

5.5

8

Dat nudse

.90·10-5 293.74 1.67·10-4

280.05 0·10-5 297.54 2.26·10-4

284.24 .20·10-5

a from K n [66]

T, K p, kPa T, K p, kPa 

273.15 2.461·10-5 308.63 5.713·10-4

280.25 4

1

1

3

Dat ordes 8]

.902·10-5 312.93 7.954·10-4

292.74 .517·10-4 319.33 1.280·10-3

293.04 .553·10-4 312.83 7.778·10-4

303.33 .741·10-4 323.93 1.775·10-3

a from K and Raaz [6

T, K p, kPa 

630.19 101.325

632.19 101.325 

48
Data from Mayer [69] 

T, K p, kPa T, K p, kPa T, K p, kPa 

262.16 6.27·10-6 272.45 2.45·10-5 295.84 2.15·10-4

263.26 7.73·10-6 272.75 2.49·10-5 296.84 2.37·10-4

 298.14 2.59·10-4

 261.46 6.13·10-6

 262.16 6.80·10-6

 262.76 7.47·10-6

 263.16 8.13·10-6

 264.46 9.47·10-6

 264.86 1.01·10-5

279 5 5.2 10-5 265.46 1.11·10-5

271.40 2.09·10-5 280.94 5.88·10-5 265.66 1.12·10-5

 282.29 6.52·10-5 266.56 1.29·10-5

2 2 283.24 7.15·10-5 267.55 1.51·10-5

2 284.04 7.81·10-5 267.75 1.47·10-5

3 284.94 8.52·10-5 269.75 1.81·10-5

3 286.04 9.47·10-5 272.35 2.36·10-5

277.00 3.92·10 287.04 1.03·10-4 272.95 2.52·10-5

-5 288.14 1.13·10-4 273.15 2.55·10-5

2 4 289.24 1.25·10-4 273.15 2.56·10-5

 290.34 1.36·10-4 273.35 2.60·10-5

 291.34 1.48·10-4 273.85 2.72·10-5

 292.44 1.61·10-4 274.45 2.92·10-5

283.24 7.17·10 293.74 1.79·10-4 275.05 3.03·10-5

-5 294.54 1.91·10-4 275.75 3.44·10-5

2 1 2 276.75 3.76·10-5

 276.95 3.88·10-5

 277.95 4.29·10-5

Dat cLeod

264.66 9.20·10-6 273.45 2.67·10-5

265.66 1.04·10-5 273.85 2.76·10-5

266.65 1.15·10-5 274.65 2.99·10-5

267.65 1.29·10-5 275.75 3.48·10-5

268.55 1.48·10-5 276.70 3.91·10-5

268.95 1.53·10-5 277.65 4.25·10-5

269.60 1.65·10-5 278.75 4.87·10-5

270.45 1.85·10-5 .7 7·

272.25 2.32·10-5

73.10 .59·10-5

273.20 .59·10-5

274.65 .01·10-5

276.05 .51·10-5

-5

278.10 4.40·10

78.05 .40·10-5

279.30 4.49·10-5

280.84 5.76·10-5

280.79 5.76·10-5

-5

285.54 9.01·10

88.04 .13·10-4 95.74 2.08·10-4

289.94 1.32·10-4 292.54 1.61·10-4

272.00 2.31·10-5 293.89 1.80·10-4

a from M [70]

T, K p, kPa 

293.14 0.000765

49
Data from Menzies [40, 94] 

T, K p, kPa T, K p, kPa T, K p, kPa 

394.92 1.1052·10-1 602.72 6.0942·101 645.54 ·102 1.3366

4 3. -1 6 6 1 6 102

1 2

2

2

6 6.82 1.9012·102

6 7.05 2.2335·102

·101 625.06 9.3022·101 679.94 2.3255·102

1 9.7609 1 683.43 102

5 2. 1 6 9 1 3 102

1. 2 02

2

1.0 02 2

1 2 2

1 2

Dat illar [7

23.10 7357·10 07.01 .6396·10 651.4 1.4781·

464.58 .7359 611.05 7.1667·101 656.74 1.6140·10

526.92 1.0943·101 615.66 7.8228·101 659.45 1.6873·10

533.29 1.2911·101 619.97 8.4660·101 662.35 1.7680·10

537.10 1.4201·101 620.57 8.5622·101 6

540.92 1.5604·101 624.95 9.3023·101 7

544.75 1.7141

548.61 1.8805·10

2641·10

 627.66 ·10

.9700·10

2.4629·

56.53 28.79 689.9 2.7159·

565.97 2.8103·101 630.13 0205·10 692.87 2.8342·1

571.23 3.1592·101 630.54 1.0256·102 699.29 3.1121·10

577.63 3.6429·101 633.86 892·1 706.78 3.4653·10

583.62 4.1294·101 635.24 .1151·10 707.47 3.4988·10

587.20 4.4652·101 638.43 .1809·10

599.51 5.7186·101 641.34 1.2434·102

a from M 1]

T, K p, kPa T, K p, kPa 

468.30 1.960 575.33 3.449·101

518.02 8.319 613.04 7.475·101

 613.94 7.605·101

Dat orley [

p

571.93 3.264·101

a from M 72] 

T, K , kPa T, K p, kPa 

289.14 1. -4 33·10 323.13 1.51·10-3

303.13 3 333 2 2.85 -3

-4 5.39·10-3

Data urgules opor [73]

.60·10-4 .1 ·10

313.13 6.93·10 343.12 

from M cu and T

T, K p, kPa T, K p, kPa 

465.65 1.91 532.17 1.27·101

476.15 2.57 546.58 1.808·101

485.16 3.36 549.58 1.93 101

494.16 4.44 559.18 2.438·101

507.57 6.63 

3·

50
Data from Neumann and Völker [74]

T, K p, kPa T, K p, kPa 

343.82 6.8 -3 81·10 311.98 7.32·10-4

338.82 5.0 -3

3.9 -3

3

2

325.33 1.964·10-3 297.79 2.56·10-4

296.39 1.96·10-4

3 1 2 1

1.

8.8 -4

Dat dder and tt [75]

p

05·10 309.13 6.03·10-4

335.62 56·10 306.33 4.91·10-4

334.02 .557·10-3 305.63 4.57·10-4

329.38 .597·10-3 300.38 2.99·10-4

321.23 1.448·10-3

19.53 .31·10-3 94.04 .79·10-4

316.93 1.09·10-3 289.54 20·10-4

314.08 4·10

a from Pe Barra

T, K , kPa

556.68 22.49

557.18 22.61

573.18 33.13

Dat aundler [

p

a from Pf 76]

T, K , kPa

288.14 1.0 -4 80·10

329.43 2.4 -3

3.5 -2

ata from Poindexter [77] 

T, K p, kPa 

01·10

371.92 07·10

D

T, K p, kPa 

235.34 1.84·10 2 1 -7 67.44 .34·10-5

240.44 3.63·10-7 269.17 1 -5

4. -7 2 -5

7. -7 2 -5

1. -6

2. -6 7 -5

3. -6 9 -5

6. -6 1 -4

193.58* 4.00·10-10 216.31* 6.91·10-9

 223.30* 3.16·10-8

2 5 22 9

1.6 -9 1. -7

6. -9 1

* P triple p ot included in analys

.65·10

242.20 95·10 273.36 .52·10

245.03 60·10 274.91 .92·10

250.43 56·10 281.13 5.76·10-5

252.60 34·10 284.00 .71·10

255.94 28·10 286.18 .61·10

261.16 95·10 292.87 .61·10

262.35 7.86·10-6

203.25* 8.00·10-10

06.30* .33·10-9 9.75* .75·10-8

209.47* 9·10 230.38* 00·10

215.43* 47·10 231.39* .14·10-7

oint below oint, n is.

51
 

Data from Ramsay and Young [36] 

T, K p, kPa T, K p, kPa T, K p, kPa 

495.31 4.59 630.67 1.0244·102 631.87 1.0106·102

543.98 1.6579·101 630.67 1.0223·102 7

7

Dat egnaul

20.46 3.8622·102

553.38 2.0952·101 632.46 1.0240·102 21.46 3.8723·102

631.65 1.0260·102 632.46 1.0214·102

631.65 1.0269·102 631.87 1.0181·102

a from R t [33]

T, K p, kPa T, K p, kPa T, K p, kPa 

296.71 9.07·10-3 473.65 2.934 627.79 1.0109·102

311.14 1.31·10-2 631.66 1.022·102 6

7

7

7

7

 782.08 9.3193·10

373.72 7.47·10 604.79 6.4836·101 773.42 7.9543·102

 618.08 8.3313·101 627.79 1.0109·102

451.04 1.429 6 1. 2

Da debu n [79]

86.34 2.0393·102

373.72 7.40·10-2 524.25 9.88 01.77 3.5813·102

298.52 4.53·10-3 525.77 1.04·101 17.51 4.2405·102

322.28 1.16·10-2 528.62 1.13·101 49.24 6.1513·102

345.86 2.44·10-2 570.39 3.1781·101 85.22 9.7548·102

373.23 5.43·10-2 587.25 4.6103·101 2

-2

419.43 4.61·10-1

28.02 0157·10

ta from Ro sh and Dixo

T, K p, kPa T, K p, kPa 

443.54 8.39·10-1 462.75 1.644

451.24 1.11 470.35 2.104

453.25 1.17 475.95 2.520 

Dat oeder a ietz [80]

T, K p, kPa 

457.05 1.351 

a from R nd Moraw

T, K p, kPa 

413.13 2.433·10-1 523.17 9.930 

433.14 5.466·10-1 563.18 2.646·101

.19 7.363·101

483.16 3.160 

453.15 1.187 613

52
Data from Ruff and Bergdahl [81]

T, K p, kPa T, K p, kPa T, K p, kPa 

478.15 1.6 573.18 2.91·101 625.19 1.01·102

508.17 4.3 583.18 4.23·101 6

 

Dat hmahl, Barthel and Kaloff [82] 

T, K p, kPa 

30.19 1.01·102

513.17 4.7 597.19 5.04·101

533.17 1.2·101 615.19 6.87·101

543.18 1.3·101 628.19 1.00·102

a from Sc

T, K p, kPa T, K p, kPa 

446.64 9.3·10-1 519.17 8.92 617.69 8.121·101

449.64 1.0 529.17 1.15·101 621.19 8.765·101

478.15 2.72 531.67 1.25·101 628.19 9.806·101

479.66 2.84 540.68 1.540·101 629.69 1.010·102

482.16 3.04 549.68 1.919·101 637.18 1.148·102

487.66 3.60 551.68 2.034·101 639.68 1.211·102

492.66 4.23 562.68 2.604·101 412.43 2.37·10-1

493.66 4.36 572.68 3.260·101 415.33 2.69·10-1

498.66 4.99 574.18 3.350·101 420.43 3.32·10-1

498.66 5.07 579.18 3.746·101 425.64 4.15·10-1

499.16 5.13 582.68 4.041·101 430.64 5.03·10-1

504.16 5.84 596.19 5.313·101 435.54 6.03·10-1

507.17 6.36 606.19 6.467·101 438.64 6.81·10-1

509.67 6.97 609.19 6.819·101 

510.67 6.97 616.69 7.923·101 

Data from Schneider and Schupp [83] 

T, K p, kPa T, K p, kPa T, K p, kPa 

539.68 1.484·101 500.16 550.18 1.943·101 5.31

519.17 8.00 491.16 4.00 552.18 2.038·101

484.16 2.95 553.18 2.024·101

518.17 7.88 523.17 1.01·101 554.18 2.190·101

501.16 5.37 545.18 1.727·101

502.16 5.21 563.18 2.686·101

.16 5.07 550.18 1.933·101

575.18 3.468·101 551.18 1.993·101 

Data chönherr nsel [84]

p a

519.17 7.93

521.67 9.05

519.17 8.81

519.67 9.67 502

from S and He

T, K , kPa T, K p, kP T, K p, kPa 

1051.44 90 1581.99 991 1716.40 1490 

1186.24 200 1632.52 1155 1726.05 1535 

1322.14 382 1665.97 1275 1735.51 1575 

1424.66 571 1686.68 1345 

1510.37 782 1704.76 1430 

 

Data from Scott [85] 

T, K p, kPa 

293.14 1.73·10-4

53
Data from Shpil’rain and Nikanorov [86] 

T, K p, kPa T, K p, kPa T, K p, kPa 

554.11 2.152·101 635.61 1.123·102 786.77 9.6252·102

560.61 2.505·101 639.81 1.210·102 796.86 1.0798·103

567.11 2.893·101 642.11 1.257·102 814.46 1.3057·103

578.91 3.740·101 643.81 1.293·102 836.25 1.63551·103

600.61 5.854·101 664.30 1.8254·102 803.66 1.16117·103

604.11 6.261·101 707.29 3.4921·102 815.46 1.31973·103

621.11 8.635·101 742.78 5.6147·102 822.45 1.42302·103

622.21 8.811·101 755.98 6.6372·102 831.85 1.56996·103

623.71 9.038·101 774.67 8.3905·102 845.39 1.79551·103

626.81 9.547·101 648.01 1.3862·102 847.24 1.82505·103

629.41 1.002·102 677.30 2.2531·102 854.54 1.96728·103

635.21 1.117·102 681.50 2.3779·102 856.44 1.99968·103

643.31 1.279·102 694.70 2.9070·102 866.64 2.21186·103

619.71 8.419·101 724.09 4.4107·102 880.43 2.51478·103

628.11 9.815·101 732.39 4.9111·102 882.13 2.55352·103

628.31 9.889·101 752.68 6.3837·102 883.23 2.57295·103

630.91 1.034·102 774.57 8.3449·102 

Data from Spedding and Dye [87] 

T, K p, kPa T, K p, kPa T, K p, kPa 

533.825 1.306·101 573.610 3.3293·101 613.886 7.5568·101

549.811 1.9337·101 586.013 4.3390·101 620.254 8.5144·101

558.948 2.3954·101 594.741 5.1918·101 630.244 1.0222·102

564.721 2.7351·101 597.253 5.4588·101 

565.743 2.7964·101 604.288 6.2792·101 

Data from Stock and Zimmermann [88] 

T, K p, kPa 

283.14 7.33·10-5

273.15 2.39·10-5

253.17 4.40·10-6

213.19* 6.53·10-7

* Point below triple point, not included in analysis. 

Data from Sugawara, Sato, and Minamiyama [9] 

T, K p, kPa T, K p, kPa T, K p, kPa 

601.67 6.0389·101 735.22 5.2093·102 873.15 2.3650·103

630.83 1.0258·102 768.75 7.9022·102 892.71 2.8647·103

664.10 1.8162·102 795.55 1.0710·103 918.61 3.5883·103

683.99 2.4860·102 824.15 1.4651·103 929.62 3.8828·103

705.03 3.3804·102 853.24 1.9858·103 

54
55

Data from van der Plaats [89] 

T, K p, kPa T, K p, kPa T, K p, kPa 

273.15 6.27·10P

-4P 287.14 1.32·10P-3P 289.14 1.53·10P-3P

283.14 1.07·10P

-3P 280.15 9.47·10P-4P 286.14 1.33·10P-3P

287.14 1.33·10P

-3P 283.14 1.06·10P-3P 286.14 1.25·10P-3P

285.14 1.35·10P

-3P 283.14 1.12·10P-3P 287.14 1.35·10P-3P

291.14 1.77·10P

-3P 273.15 6.40·10P-4P 

273.15 5.60·10P

-4P 292.14 1.72·10P-3P 

277.15 7.73·10P

-4P 273.15 5.87·10P-4P 

282.14 9.73·10P

-4P 284.14 1.11·10P-3P 

283.14 1.03·10P

-3P 354.12 1.49·10P-2P 

273.15 6.87·10P

-4P 358.12 1.66·10P-2P 

293.14 1.77·10P

-3P 285.14 7.73·10P-4P 

Data from Villiers [90] 

T, K p, kPa T, K p, kPa T, K p, kPa 

333.12 3.47·10P

-3P 373.12 4.00·10P-2P 365.12 2.55·10P-2P

341.12 5.73·10P

-3P 333.12 3.67·10P-3P 373.12 4.01·10P-2P

349.12 1.01·10P

-2P 341.12 5.87·10P-3P 

357.12 1.64·10P

-2P 349.12 1.03·10P-2P 

365.12 2.57·10P

-2P 357.12 1.64·10P-2P 

Data from Volmer and Kirchhoff [91] 

T, K p, kPa T, K p, kPa 

312.93 8.293·10P

-4P 308.63 5.934·10P-4P

312.93 8.175·10P

-4P 308.63 5.990·10P-4P

303.33 4.048·10P

-4P 308.63 6.000·10P-4P

303.33 3.957·10P

-4P 312.93 8.257·10P-4P

303.33 3.960·10P

-4P 312.93 8.211·10P-4P

Data from von Halban [92] 

T, K p, kPa 

255.16 3.76·10P

-6P

219.79* 3.31·10P

-8P

* Point below triple point, not included in analysis. 

Data from Young [93] 

T, K p, kPa T, K p, kPa T, K p, kPa 

456.95 1.33 495.31 4.59 629.95 1.013·10P

2

P

456.85 1.31 510.12 6.91 716.60 3.862·10P

2

P

510.07 6.913 543.48 1.658·10P

1

P 717.60 3.872·10P

2

P

456.90 1.32 553.38 2.095·10P

1

P 
56

Appendix B. Detailed Listing of Supplemental Experimental Data for the Heat 

Capacity of Mercury 

All temperatures have been converted to ITS-90. Data are arranged alphabetically by first 

author. 

Smoothed data from Amitin, Lebedeva and Paukov [123] 

T, K CB

pB, J/(mol·K) T, K CB

pB, J/(mol·K) 

234.3375 28.543 289.9958 27.987 

240.0066 28.473 298.1437 27.911 

250.0049 28.359 299.9932 27.899 

260.0029 28.255 

270.0007 28.162 

273.1500 28.134 

279.9984 28.076 

Smoothed data from Busey and Giauque [44] 

T, K CB

pB, J/(mol·K) T, K CB

pB, J/(mol·K)

234.3206 28.476 349.9729* 27.606 

240.0264 28.430 399.9785 27.359 

250.0185 28.351 449.9942 27.204 

260.0103 28.275 500.0132 27.129 

270.0024 28.196 550.0289 27.117 

279.9953 28.121 600.0361 27.146 

289.9893 28.041 650.0326 27.217 

298.1452 27.983 700.0199 27.338 

299.9843 27.966 750.0049 27.514 

* Note: Maximum temperature of their measurements was 330 K; values at higher temperatures are based 

on measurements in the literature. 

Smoothed data from Douglas et al. [51] 

T, K CB

pB, J/(mol·K) T, K CBpB, J/(mol·K)

234.3006 28.275 513.1679 27.158 

253.166 28.147 533.1743 27.141 

273.15 28.019 553.1796 27.132 

293.1376 27.900 573.1835 27.130 

298.1352 27.872 593.1858 27.137 

313.1293 27.790 613.1863 27.150 

333.1245 27.688 629.7653 27.167 

353.1229 27.595 633.185 27.171 

373.1238 27.511 653.182 27.198 

393.127 27.435 673.1776 27.232 

413.1319 27.368 693.172 27.274 

433.1382 27.309 713.1658 27.321 

453.1454 27.259 733.1596 27.374 

473.153 27.217 753.1541 27.433 

493.1607 27.183 773.1501 27.499