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1. GPA Standard 2145-09
Adopted 1942
Revised 1957,1962, 1966, 1971, 1975, 1977, 1982, 1983, 1984, 1985, 1986, 1988,
1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 2000, 2003, 2005, 2007, 2009
Reprinted 1997, 1998
Gas Processors Association
6526 East 60th Street
Tulsa, Oklahoma 74145
Table of Physical Properties
for Hydrocarbons and Other
Compounds of Interest to the
Natural Gas Industry
Copyright Gas Processors Association
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2. FOREWORD
The Table of Physical Properties for Hydrocarbons and Other Components of Interest to the Natural
Gas Industry, GPA Publication Standard 2145, provides the gas processing industry with a convenient
compilation of authoritative numerical values for the paraffin hydrocarbons and other compounds
occurring in natural gas and natural gas liquids as well as for a few other compounds of interest to the
industry. The physical properties selected are those considered most valuable for engineering and
analytical computations in gas processing plants and laboratories. Most properties are based upon two
NIST Standard Reference Databases: the Web Thermo Tables, WTT, (NIST SRSD-3) and the
Reference Fluid Thermodynamic and Transport Properties Database, REFPROP, (NIST SRD-23). The
data in this publication were checked, evaluated, and recalculated when necessary by Robert Chirico
and Eric Lemmon of the Physical and Chemical Properties Division of the Chemical Science and
Technology Laboratory at NIST in Boulder, Colorado. The listed flammability limits and octane
numbers were not evaluated at NIST and sources for these properties are provided in the references.
Some of the listed values result from other values in the tables by simple calculation. Numbers obtained
from such related data may differ from the tabulated values in the last digit because of numerical round
off, but the differences are within the standard uncertainty of the data. The value of the gas constant
used in the tables is 8.314472 J/(K·mol). Numerous values were updated from the previous edition of
GPA-2145 to provide full thermodynamic consistency between properties. This was accomplished
through consistent use of properties derived with the equations of state underlying the NIST REFPROP
database. Properties derived with these equations of state are inherently consistent. This publication
represents the first time for which thermodynamic consistency is assured for all properties listed in GPA-
2145. Required enthalpies of combustion at 298.15 K were taken from the NIST Web Thermo Tables
(WTT). These enthalpies of combustion are reprinted in the notes of this document. All adjustments of
these values to the selected temperatures of GPA-2145 were completed using consistent thermophysical
property values from the NIST REFPROP program.
The values of the physical properties for the components in GPA 2145, as well as those for many more
compounds, appear in the GPSA Engineering Data Book. Property values for compounds listed here in
GPA 2145-09 supersede those listed in the GPSA Engineering Data Book. For components not listed in
GPA 2145, the property values in GPA TP-17 may be used.
DISCLAIMER
GPA publications necessarily address problems of a general nature and may be used by anyone desiring
to do so. Every effort has been made by GPA to assure accuracy and reliability of the information
contained in its publications. With respect to particular circumstances, local, state, and federal laws and
regulations should be reviewed. It is not the intent of GPA to assume the duties of employers,
manufacturers, or suppliers to warn and properly train employees or others exposed, concerning health
and safety risks or precautions.
GPA makes no representation, warranty, or guarantee in connection with this publication and hereby
expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the
violation of any federal, state, or municipal regulation with which this publication may conflict, or for
any infringement of letters of patent regarding apparatus, equipment, or method so covered.
GPA 2145 Page 2
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No part of this Report may be reproduced without written
consent of the Gas Processors Association."
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3. Molar Mass 16.0425 30.0690 44.0956 58.1222 58.1222 72.1488 72.1488
Boiling Temperature *
at 14.696 psia, °F -258.66 -127.44 -43.80 10.85 31.12 82.09 96.91
Triple Point Temperature
°F -296.42 -297.01 -305.72 -254.96 -216.85 -256.90 -201.42
Vapor Pressure *
at 100 °F, psia 5000 800 188.62 72.644 51.567 20.474 15.576
Density of Liquid *
at 60 °F, 14.696 psia
Relative density at 60 °F/60 °F 0.3 0.35628 0.50719 0.56283 0.58420 0.62514 0.63071
API Gravity 340 265.66 147.49 119.91 110.71 94.848 92.850
Absolute density, lbm/gal 2.5 2.9704 4.2285 4.6925 4.8706 5.2120 5.2584
Density of Ideal Gas
at 60 °F, 14.696 psia
Relative density, air = 1.0 0.5539 1.0382 1.5225 2.0068 2.0068 2.4911 2.4911
Density lbm/(1000 ft3
) 42.27 79.24 116.20 153.16 153.16 190.12 190.12
Summation Factor
at 60 °F, psia-1
0.0116 0.0238 0.0347 0.0441 0.0470 0.0576 0.0606
Volume *
at 60 °F, 14.696 psia
Liquid, gal/lbmol 6.417 10.123 10.428 12.386 11.933 13.843 13.721
Ft3
ideal gas/gal liquid 59.138 37.488 36.391 30.637 31.801 27.414 27.658
Ratio, ideal gas/liquid 442.38 280.43 272.22 229.18 237.89 205.07 206.89
Critical Conditions
Temperature, °F -116.66 89.91 206.13 274.39 305.56 368.96 385.79
Pressure, psia 667.1 706.7 616.6 526.3 550.6 489.9 488.8
Gross Heating Value *
at 60 °F, ideal reaction
Btu/lbm, fuel as liquid 22185 21491 21081 21137 20891 20923
Btu/gal, fuel as liquid 65897 90875 98924 102950 108880 110020
Btu/lbm, fuel as ideal gas 23892 22334 21654 21232 21300 21044 21085
Btu/ft3
, fuel as ideal gas 1010.0 1769.7 2516.1 3251.9 3262.3 4000.9 4008.7
Btu/gal, fuel as ideal gas 59729 66340 91563 99630 103740 109680 110870
Net Heating Value
at 60 °F, ideal reaction
Btu/ft3
, fuel as ideal gas 909.4 1619 2315 3000 3011 3699 3707
9.548 16.710 23.871 31.032 31.032 38.193 38.193
Heat of Vaporization *
at 14.696 psia, °F
Btu/lbm at the boiling point 219.6 210.4 183.0 157.0 165.8 147.6 153.7
Specific Heat *
at 60 °F, 14.696 psia
C P , Btu/(lbm °F), ideal gas 0.5266 0.4079 0.3873 0.3866 0.3949 0.3828 0.3879
C V , Btu/(lbm °F), ideal gas 0.4028 0.3418 0.3423 0.3525 0.3608 0.3553 0.3603
k = C P /C V , ideal gas 1.3073 1.1932 1.1316 1.0969 1.0947 1.0775 1.0764
C S , Btu/(lbm °F), sat. liq. 0.9664 0.6183 0.5641 0.5692 0.5311 0.5427
Flammability Limits
at 100 °F, 14.696 psia
Lower, volume % In air 5.0 2.9 2.0 1.8 1.5 1.3 1.4
Upper, volume % in air 15.0 13.0 9.5 8.5 9.0 8.0 8.3
Octane Number
Motor clear 0.05 97.1 97.6 89.6 90.3 62.6
Research clear 1.6 1.8 0.1 93.8 92.3 61.7
n-Pentane
Volume of Air to Burn One
Volume of Ideal Gas
* For some compounds, values within this property group are for conditions different from those given in the row heading. See the notes
on pages 6 through 8 for details. Values in boldface type are different from those in the previous version of GPA-2145.
PHYSICAL PROPERTIES OF SELECTED HYDROCARBONS
GPA STANDARD 2145-09 (FPS) becomes effective January 1, 2009
Component Methane Ethane Propane i-Butane n-Butane i-Pentane
GPA 2145 page 3
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4. Molar Mass 86.1754 100.2019 114.2285 128.2551 142.2817 28.0532 42.0797
Boiling Temperature *
at 14.696 psia, °F 155.68 209.08 258.12 303.37 345.42 -154.79 -53.72
Triple Point Temperature
°F -139.58 -131.08 -70.20 -64.21 -21.37 -272.49 -301.35
Vapor Pressure *
at 100 °F, psia 4.961 1.619 0.5349 0.1809 0.06148 227.3
Density of Liquid *
at 60 °F, 14.696 psia
Relative density at 60 °F/60 °F 0.66406 0.68823 0.70655 0.72224 0.73458 0.52260
API Gravity 81.582 74.101 68.768 64.418 61.127 139.260
Absolute density, lbm/gal 5.5364 5.7379 5.8907 6.0215 6.1244 4.3571
Density of Ideal Gas
at 60 °F, 14.696 psia
Relative density, air = 1.0 2.9754 3.4597 3.9440 4.4283 4.9126 0.9686 1.4529
Density lbm/(1000 ft3
) 227.09 264.05 301.01 337.97 374.93 73.92 110.89
Summation Factor
at 60 °F, psia-1
0.0776 0.0951 0.1128 0.1307 0.1556 0.0207 0.0327
Volume *
at 60 °F, 14.696 psia
Liquid, gal/lbmol 15.565 17.463 19.391 21.300 23.232 9.6578
Ft3
ideal gas/gal liquid 24.380 21.730 19.570 17.816 16.334 39.293
Ratio, ideal gas/liquid 182.38 162.56 146.39 133.28 122.19 293.93
Critical Conditions
Temperature, °F 453.8 512.56 564.22 610.52 652.19 48.56 195.91
Pressure, psia 436.9 396.8 360.7 330.8 305.0 731.3 660.6
Gross Heating Value *
at 60 °F, ideal reaction
Btu/lbm, fuel as liquid 20783 20680 20601 20543 20494 20875
Btu/gal, fuel as liquid 115060 118660 121350 123700 125510 90954
Btu/lbm, fuel as ideal gas 20943 20839 20760 20701 20651 21640 21040
Btu/ft3
, fuel as ideal gas 4755.9 5502.6 6249.0 6996.3 7742.9 1599.7 2333.0
Btu/gal, fuel as ideal gas 115950 119570 122290 124650 126480 91672
Net Heating Value
at 60 °F, ideal reaction
Btu/ft3
, fuel as ideal gas 4404 5100 5796 6493 7190 1499 2182
45.355 52.516 59.677 66.839 74.000 14.323 21.484
Heat of Vaporization *
at 14.696 psia, °F
Btu/lbm at the boiling point 144.0 136.2 129.9 124.1 118.8 207.4 188.7
Specific Heat *
at 60 °F, 14.696 psia
C P , Btu/(lbm °F), ideal gas 0.3857 0.3841 0.3829 0.3820 0.3813 0.3573 0.3567
C V , Btu/(lbm °F), ideal gas 0.3626 0.3643 0.3655 0.3665 0.3673 0.2865 0.3095
k = C P /C V , ideal gas 1.0635 1.0544 1.0476 1.0423 1.0380 1.2471 1.1525
C S , Btu/(lbm °F), sat. liq. 0.5285 0.5268 0.5240 0.5192 0.5155 0.6020
Flammability Limits
at 100 °F, 14.696 psia
Lower, volume % In air 1.1 1.0 0.8 0.7 0.7 2.9 2.1
Upper, volume % in air 7.7 7.0 6.5 5.6 5.4 32.0 11.1
Octane Number
Motor clear 26
Research clear 24.8
Volume of Air to Burn One
Volume of Ideal Gas
All values in this table are on the International Temperature Scale 1990 (ITS-90).
GPA STANDARD 2145-09 (FPS) becomes effective January 1, 2009
Ethylene Propylene
PHYSICAL PROPERTIES OF SELECTED HYDROCARBONS
Component n-Hexane n-Heptane n-Octane n-Nonane n-Decane
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5. Carbon Hydrogen
Dioxide Sulfide
Molar Mass 44.0095 34.0809 28.0134 31.9988 4.0026 28.9625 18.0153
Boiling Temperature *
at 14.696 psia, °F -109.24 -76.54 -320.43 -297.33 -452.06 -317.64 211.95
Triple Point Temperature
°F -69.81 -121.81 -346.00 -361.82 -455.75 -352.12 32.018
Vapor Pressure *
at 100 °F, psia 395.0 0.95050
Density of Liquid *
at 60 °F, 14.696 psia
Relative density at 60 °F/60 °F 0.81716 0.79886 0.80687 1.1423 0.12486 0.87586 1.00000
API Gravity 41.660 45.628 43.868 -7.630 1002 30.055 10.000
Absolute density, lbm/gal 6.8129 6.6602 6.7271 9.5238 1.041 7.3022 8.3372
Density of Ideal Gas
at 60 °F, 14.696 psia
Relative density, air = 1.0 1.5195 1.1767 0.9672 1.1048 0.1382 1.0000 0.62202
Density lbm/(1000 ft3
) 115.97 89.81 73.820 84.322 10.547 76.321 47.473
Summation Factor
at 60 °F, psia-1
0.0195 0.0239 0.00442 0.0072 0.00537 0.06510
Volume *
at 60 °F, 14.696 psia
Liquid, gal/lbmol 6.4598 5.1171 4.1643 3.3599 3.8451 3.9663 2.1608
Ft3
ideal gas/gal liquid 58.746 74.16 91.128 112.95 98.693 95.678 175.62
Ratio, ideal gas/liquid 439.45 554.76 681.69 844.89 738.27 715.72 1313.7
Critical Conditions
Temperature, °F 87.76 211.91 -232.53 -181.43 -450.32 -221.12 705.11
Pressure, psia 1070.0 1305.3 492.5 731.4 33.0 549.1 3200.1
Gross Heating Value *
at 60 °F, ideal reaction
Btu/lbm, fuel as liquid 6892.4
Btu/gal, fuel as liquid 45905
Btu/lbm, fuel as ideal gas 7094.0 1059.8
Btu/ft3
, fuel as ideal gas 637.10 50.310
Btu/gal, fuel as ideal gas 47248 8835.4
Net Heating Value
at 60 °F, ideal reaction
Btu/ft3
, fuel as ideal gas 586.79
7.1613
Heat of Vaporization *
at 14.696 psia, °F
Btu/lbm at the boiling point 246.5 234.9 85.63 91.60 8.922 88.07 970.12
Specific Heat *
at 60 °F, 14.696 psia
C P , Btu/(lbm °F), ideal gas 0.1992 0.2383 0.2483 0.2189 1.2404 0.2399 0.44478
C V , Btu/(lbm °F), ideal gas 0.1541 0.1800 0.1774 0.1569 0.7442 0.1714 0.33455
k = C P /C V , ideal gas 1.2929 1.3236 1.3996 1.3956 1.6667 1.4002 1.3295
C S , Btu/(lbm °F), sat. liq. 0.6857 0.5088 1.0003
Flammability Limits
at 100 °F, 14.696 psia
Lower, volume % In air 4.3
Upper, volume % in air 45.5
Octane Number
Motor clear
Research clear
* For some compounds, values within this property group are for conditions different from those given in the row heading. See the notes
on pages 6 through 8 for details. Values in boldface type are different from those in the previous version of GPA-2145.
Volume of Air to Burn One
Volume of Ideal Gas
Water
PHYSICAL PROPERTIES OF SELECTED HYDROCARBONS
GPA STANDARD 2145-09 (FPS) becomes effective January 1, 2009
Component Nitrogen Oxygen Helium Air
GPA 2145 Page 5
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6. Molar Mass 1
Boiling Temperature
at 14.696 psia, °F 2
Triple Point Temperature
°F 2
Vapor Pressure
at 100 °F, psia 2 b b
Density of Liquid
at 60 °F, 14.696 psia
Relative density at 60 °F/60 °F 2 b
API Gravity 2 b
Absolute density, lbm/gal 2 b d d d d
Density of Ideal Gas
at 60 °F, 14.696 psia
Relative density, air = 1.0
Density lbm/(1000 ft3
) f
Summation Factor
at 60 °F, psia-1 2
Volume
at 60 °F, 14.696 psia
Liquid, gal/lbmol g
Ft3
ideal gas/gal liquid g b d d d d
Ratio, ideal gas/liquid g b d d d d
Critical Conditions
Temperature, °F 2 2 2 2 2 2 2 3 2
Pressure, psia 2 2 2 2 2 2 2 3 2
Gross Heating Value
at 60 °F, ideal reaction
Btu/lbm, fuel as liquid i d d d d 3 3 3 3
Btu/gal, fuel as liquid g d d d d
Btu/lbm, fuel as ideal gas 3 3 3 3 3
Btu/ft3, fuel as ideal gas
Btu/gal, fuel as ideal gas
Net Heating Value
at 60 °F, ideal reaction
Btu/ft3, fuel as ideal gas
k
Heat of Vaporization
at 14.696 psia, °F
Btu/lbm at the boiling point 2
Specific Heat
at 60 °F, 14.696 psia
C P , Btu/(lbm °F), ideal gas 2
C V , Btu/(lbm °F), ideal gas
k = C P /C V , ideal gas
C S , Btu/(lbm °F), sat. liq. 2 c
Flammability Limits
at 100 °F, 14.696 psia
Lower, volume % In air 4
Upper, volume % in air 4
Octane Number
Motor clear 5 l m m
Research clear 5 l, m l, m l, m m m
TABLE FOR NOTES AND REFERENCES
GPA STANDARD
i-C5
C3 n-C5
C2 i-C4 n-C4 n-C6 n-C7
Volume to Burn One Volume of Ideal
Gas
Component All C1
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7. a
c c c c c c
c
c
c d d d d,e d,e d,e d,e
e e e e
d d h h h h
d d h h h h
3 2 2 2 2 2 2 2 2 2 2 2
3 2 2 2 2 2 2 2 2 2 2 2
3 3 3 c d d
c d d
3 3 3 j
j
j
n
c c c c c
n-C9 CO2
C2
=
C3
=
2145-09 (FPS)
H2O
He
N2
n-C10 O2 Air
H2S
n-C8
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8. NOTES FOR GPA STANDARD 2145-09 (FPS)
a
Component Mole Fraction (x i) Molar Mass (M ) x i·M
nitrogen 0.78102 28.0134 21.87903
oxygen 0.20946 31.9988 6.70247
argon 0.00916 39.948 0.365924
carbon dioxide 0.00033 44.0095 0.014523
neon 0.0000182 20.1797 0.000367
helium 0.0000052 4.0026 0.000021
methane 0.0000015 16.0425 0.000024
krypton 0.0000011 83.798 0.000092
hydrogen 0.0000005 2.01588 0.000001
nitrous oxide 0.0000003 44.0128 0.000013
carbon monoxide 0.0000002 28.0101 0.000006
xenon 0.0000001 131.293 0.000013
AIR 28.9625
b
c
d
e
f
g
h
i
j
k
l
m
n
o
Average value from octane numbers using more than one sample
Enthalpy of sublimation
The basis for gross heating value is dry gas at 60 °F and 14.696 psia based upon the ideal
reaction, see GPA 2172 for conversion to other bases. Conversion of enthalpies of combustion at
T = 298.15 K given in reference 3 were converted to the conditions specified here with the
property values from reference 2. Heating values for H2S are based on SO2(g) and H2O as
products.
Enthalpy of vaporization to the ideal-gas state
Values are based on an oxygen mole fraction of 0.20946 for air.
The + sign and number specify the number of cm
3
of TEL (tetraethyl lead) added per gallon to
achieve the ASTM octane number of 100, corresponding to that of 2,2,4-trimethylpentane.
For components not listed in GPA-2145, the property values listed in TP-17 may be used.
Molar Mass of Dry Atmospheric Air (g)
''The Molar Mass of Air is fixed by GPA to be 28.9625 in order to harmonize with ISO 6976-95
'Natural gas -- Calculation of calorific value, density, relative density and Wobbe index from
composition' and AGA 5-07 'Fuel Gas Energy Metering'. Individual components in Air may
change over time based on empirical data but the Molar Mass of Air, calculated from the table
shown below, will remain constant within this document for the purposes of, but not limited to,
the calculation of Gas Relative Density. The information in the table below should not be used
for individual component calculations. For information on individual components refer to the
appropriate Component Data Table.'' AGA 5-07 TABLE 7.17.1 follows.
Shaded values were estimated by GPA for the hypothetical liquid state and were not re-evaluated
The referenced temperature is above the critical temperature.
The property is that of the liquid component at saturation pressure rather than at 14.696 psia.
Densities of liquid at the normal boiling temperature
Gas constant R = 8.314472 J mol
-1
K
-1
. [10.7316 psia ft
3
/(lbmol
o
R)] and 1 Btu = 1055.056 J
Algebraically derived from the absolute density of the liquid
Gas at 60 °F and liquid at the normal boiling point
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9. Molar Mass 16.0425 30.0690 44.0956 58.1222 58.1222 72.1488 72.1488
Boiling Temperature *
at 101.325 kPa(abs), K 111.67 184.57 231.04 261.40 272.66 300.98 309.21
Triple Point Temperature
K 90.69 90.37 85.53 113.73 134.90 112.65 143.47
Vapor Pressure *
at 313.15 K, kPa(abs) 35000 5500 1369.4 531.21 378.49 151.51 115.67
Density of Liquid *
at 288.15 K, 101.325 kPa(abs)
Relative density at 15 °C/15 °C 0.3 0.35817 0.50796 0.56346 0.58478 0.62564 0.63119
Absolute density, kg m-3
300 357.85 507.50 562.95 584.25 625.08 630.62
Density of Ideal Gas
at 288.15 K, 101.325 kPa(abs)
Relative density, air = 1.0 0.5539 1.0382 1.5225 2.0068 2.0068 2.4911 2.4911
Density kg m-3
0.67848 1.2717 1.8649 2.4581 2.4581 3.0514 3.0514
Summation Factor
at 288.15 K, kPa-1
0.00442 0.00910 0.0132 0.0168 0.0179 0.0220 0.0232
Volume *
at 288.15 K, 101.325 kPa(abs)
Liquid, cm3
mol-1
53.475 84.027 86.888 103.25 99.482 115.42 114.41
Ratio, ideal gas/liquid 442.17 281.40 272.13 229.02 237.68 204.85 206.67
Critical Conditions
Temperature, K 190.56 305.32 369.89 407.81 425.13 460.35 469.70
Pressure, kPa(abs) 4599 4872.2 4251.2 3629 3796 3378 3370
Gross Heating Value *
at 288.15 K, ideal reaction
MJ kg-1
, fuel as liquid 51.604 49.990 49.038 49.166 48.593 48.668
MJ m-3
, fuel as liquid 18467 25370 27606 28725 30375 30691
MJ kg-1
, fuel as ideal gas 55.575 51.951 50.369 49.388 49.546 48.950 49.045
MJ m-3
, fuel as ideal gas 37.706 66.066 93.934 121.40 121.79 149.36 149.65
Net Heating Value
at 288.15 K, ideal reaction
MJ m-3
, fuel as ideal gas 33.95 60.43 86.42 112.0 112.4 138.1 138.4
9.548 16.710 23.871 31.032 31.032 38.193 38.193
Heat of Vaporization *
at 101.325 kPa(abs)
kJ kg-1
at the boiling point 510.8 489.4 425.6 365.1 385.7 343.3 357.6
Specific Heat *
at 288.15 K, 101.325 kPa(abs)
C P , kJ kg-1
K-1
, ideal gas 2.2036 1.7054 1.6191 1.6162 1.6511 1.6003 1.6216
C V , kJ kg-1
K-1
, ideal gas 1.6853 1.4289 1.4305 1.4731 1.5080 1.4851 1.5064
k = C P /C V , ideal gas 1.3075 1.1935 1.1318 1.0971 1.0949 1.0776 1.0765
C S , kJ kg-1
K-1
, sat. liq. 4.0050 2.5840 2.3586 2.3805 2.2208 2.2698
Flammability Limits
at 310.93 K, 101.325 kPa(abs)
Lower, volume % In air 5.0 2.9 2.0 1.8 1.5 1.3 1.4
Upper, volume % in air 15.0 13.0 9.5 8.5 9.0 8.0 8.3
Octane Number
Motor clear 0.05 97.1 97.6 89.6 90.3 62.6
Research clear 1.6 1.8 0.1 93.8 92.3 61.7
n-Pentane
* For some compounds, values within this property group are for conditions different from those given in the row heading. See the notes
on pages 12 through 14 for details. Values in boldface type are different from those in the previous version of GPA-2145.
Volume of Air to Burn One
Volume of Ideal Gas
PHYSICAL PROPERTIES OF SELECTED HYDROCARBONS
GPA STANDARD 2145-09 (SI) becomes effective January 1, 2009
Component Methane Ethane Propane i-Butane n-Butane i-Pentane
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10. Molar Mass 86.1754 100.2019 114.2285 128.2551 142.2817 28.0532 42.0797
Boiling Temperature *
at 101.325 kPa(abs), K 341.86 371.53 398.77 423.91 447.27 169.38 225.53
Triple Point Temperature
K 177.83 182.55 216.37 219.70 243.50 103.99 87.95
Vapor Pressure *
at 313.15 K, kPa(abs) 37.292 12.326 4.1263 1.414 0.4867 1648.5
Density of Liquid *
at 288.15 K, 101.325 kPa(abs)
Relative density at 15 °C/15 °C 0.66452 0.68864 0.70693 0.72262 0.73496 0.52346
Absolute density, kg m-3
663.92 688.02 706.30 721.97 734.30 522.99
Density of Ideal Gas
at 288.15 K, 101.325 kPa(abs)
Relative density, air = 1.0 2.9754 3.4597 3.9440 4.4283 4.9126 0.9686 1.4529
Density kg m-3
3.6446 4.2378 4.8310 5.4242 6.0174 1.1864 1.7797
Summation Factor
at 288.15 K, kPa-1
0.0296 0.0364 0.0431 0.0500 0.0595 0.0079 0.0125
Volume *
at 288.15 K, 101.325 kPa(abs)
Liquid, cm3
mol-1
129.80 145.64 161.73 177.65 193.77 80.46
Ratio, ideal gas/liquid 182.17 162.35 146.20 133.10 122.03 293.9
Critical Conditions
Temperature, K 507.50 540.13 568.83 594.6 617.7 282.35 364.21
Pressure, kPa(abs) 3012 2736 2487 2281 2103 5042 4555
Gross Heating Value *
at 288.15 K, ideal reaction
MJ kg-1
, fuel as liquid 48.342 48.103 47.919 47.784 47.671 48.557
MJ m-3
, fuel as liquid 32095 33096 33845 34498 35004 25395
MJ kg-1
, fuel as ideal gas 48.715 48.474 48.290 48.152 48.037 50.337 48.941
MJ m-3
, fuel as ideal gas 177.55 205.42 233.29 261.19 289.06 59.721 87.097
Net Heating Value
at 288.15 K, ideal reaction
MJ m-3
, fuel as ideal gas 164.39 190.39 216.38 242.40 268.39 55.96 81.46
45.355 52.516 59.677 66.839 74.000 14.323 21.484
Heat of Vaporization *
at 101.325 kPa(abs)
kJ kg-1
at the boiling point 334.9 316.9 302.2 288.6 276.4 482.4 439.0
Specific Heat *
at 288.15 K, 101.325 kPa(abs)
C P , kJ kg-1
K-1
, ideal gas 1.6125 1.6057 1.6008 1.5967 1.5938 1.4941 1.4916
C V , kJ kg-1
K-1
, ideal gas 1.5160 1.5227 1.5280 1.5319 1.5354 1.1977 1.2940
k = C P /C V , ideal gas 1.0636 1.0545 1.0476 1.0423 1.0381 1.2475 1.1527
C S , kJ kg-1
K-1
, sat. liq. 2.2104 2.2038 2.1918 2.1719 2.1562 2.5161
Flammability Limits
at 310.93 K, 101.325 kPa(abs)
Lower, volume % In air 1.1 1.0 0.8 0.7 0.7 2.9 2.1
Upper, volume % in air 7.7 7.0 6.5 5.6 5.4 32.0 11.1
Octane Number
Motor clear 26
Research clear 24.8
Propylene
Ethylene
PHYSICAL PROPERTIES OF SELECTED HYDROCARBONS
GPA STANDARD 2145-09 (SI) becomes effective January 1, 2009
All values in this table are on the International Temperature Scale 1990 (ITS-90).
Volume of Air to Burn One
Volume of Ideal Gas
n-Hexane n-Heptane n-Octane
Component n-Nonane n-Decane
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11. Carbon Hydrogen
Dioxide Sulfide
Molar Mass 44.0095 34.0809 28.0134 31.9988 4.0026 28.9625 18.0153
Boiling Temperature *
at 101.325 kPa(abs), K 194.69 212.85 77.355 90.188 4.230 78.90 373.12
Triple Point Temperature
K 216.59 187.70 63.151 54.361 2.177 59.75 273.16
Vapor Pressure *
at 313.15 K, kPa(abs) 2863 7.3849
Density of Liquid *
at 288.15 K, 101.325 kPa(abs)
Relative density at 15 °C/15 °C 0.82195 0.8001 0.80680 1.1422 0.1248 0.87579 1.0000
Absolute density, kg m-3
821.2 799.4 806.1 1141.2 124.7 875.0 999.102
Density of Ideal Gas
at 288.15 K, 101.325 kPa(abs)
Relative density, air = 1.0 1.5195 1.1767 0.9672 1.1048 0.1382 1.0000 0.62202
Density kg m-3
1.8613 1.4414 1.1848 1.3533 0.1693 1.2249 0.76191
Summation Factor
at 288.15 K, kPa-1
0.00745 0.00913 0.00170 0.00275 0.00206 0.02495
Volume *
at 288.15 K, 101.325 kPa(abs)
Liquid, cm3
mol-1
53.59 42.63 34.753 28.040 32.089 33.10 18.031
Ratio, ideal gas/liquid 441.2 554.6 680.4 843.3 736.9 714.3 1311.3
Critical Conditions
Temperature, K 304.1 373.1 126.19 154.58 5.195 132.53 647.10
Pressure, kPa(abs) 7377 9000 3396 5043 227.46 3786.0 22064
Gross Heating Value *
at 288.15 K, ideal reaction
MJ kg-1
, fuel as liquid 16.031
MJ m-3
, fuel as liquid 12815
MJ kg-1
, fuel as ideal gas 16.501 2.4662
MJ m-3
, fuel as ideal gas 23.784 1.8790
Net Heating Value
at 288.15 K, ideal reaction
MJ m-3
, fuel as ideal gas 21.905
7.161
Heat of Vaporization *
at 101.325 kPa(abs)
kJ kg-1
at the boiling point 573.3 546.4 199.2 213.1 20.75 204.9 2256.5
Specific Heat *
at 288.15 K, 101.325 kPa(abs)
C P , kJ kg-1
K-1
, ideal gas 0.8334 0.9976 1.0395 0.9166 5.1931 1.0045 1.8620
C V , kJ kg-1
K-1
, ideal gas 0.6445 0.7536 0.7427 0.6568 3.1158 0.7174 1.4005
k = C P /C V , ideal gas 1.2931 1.3237 1.3996 1.3956 1.6667 1.4002 1.3295
C S , kJ kg-1
K-1
, sat. liq. 2.8376 2.1277 4.1888
Flammability Limits
at 310.93 K, 101.325 kPa(abs)
Lower, volume % In air 4.3
Upper, volume % in air 45.5
Octane Number
Motor clear
Research clear
Water
Volume of Air to Burn One
Volume of Ideal Gas
* For some compounds, values within this property group are for conditions different from those given in the row heading. See the notes
on pages 12 through 14 for details. Values in boldface type are different from those in the previous version of GPA-2145.
PHYSICAL PROPERTIES OF SELECTED HYDROCARBONS
GPA STANDARD 2145-09 (SI) becomes effective January 1, 2009
Component Nitrogen Oxygen Helium Air
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12. Molar Mass 1
Boiling Temperature
at 101.325 kPa(abs), K 2
Triple Point Temperature
K 2
Vapor Pressure
at 313.15 K, kPa(abs) 2 b b
Density of Liquid
at 288.15 K, 101.325 kPa(abs)
Relative density at 15 °C/15 °C 2 b
Absolute density, kg m-3 2 b d d d d
Density of Ideal Gas
at 288.15 K, 101.325 kPa(abs)
Relative density, air = 1.0
Density kg m-3 f
Summation Factor
at 288.15 K, kPa-1 2
Volume
at 288.15 K, 101.325 kPa(abs)
Liquid, cm3
mol-1
g b d d d d
Ratio, ideal gas/liquid g b d d d d
Critical Conditions
Temperature, K 2 2 2 2 2 2 2 3 2
Pressure, kPa(abs) 2 2 2 2 2 2 2 3 2
Gross Heating Value
at 288.15 K, ideal reaction
MJ kg-1
, fuel as liquid i d d d d 3 3 3 3
MJ m-3
, fuel as liquid g d d d d
MJ kg-1
, fuel as ideal gas 3 3 3 3 3
MJ m-3
, fuel as ideal gas
Net Heating Value
at 288.15 K, ideal reaction
MJ m-3
, fuel as ideal gas
k
Heat of Vaporization
at 101.325 kPa(abs)
kJ kg-1
at the boiling point 2
Specific Heat
at 288.15 K, 101.325 kPa(abs)
C P , kJ kg-1
K-1
, ideal gas 2
C V , kJ kg-1
K-1
, ideal gas
k = C P /C V , ideal gas
C S , kJ kg-1
K-1
, sat. liq. 2 c
Flammability Limits
at 310.93 K, 101.325 kPa(abs)
Lower, volume % In air 4
Upper, volume % in air 4
Octane Number
Motor clear 5 l m m
Research clear 5 l, m l, m l, m m m
i-C5 n-C5
TABLE FOR NOTES AND REFERENCES
GPA STANDARD
C2 C3 i-C4 n-C4 n-C6 n-C7
Volume of Air to Burn One
Volume of Ideal Gas
Component All C1
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13. a
c c c c c c
c
c d d d d, e d, e d, e d, e
c d d h h h h
c d d h h h h
3 2 2 2 2 2 2 2 2 2 2 2
3 2 2 2 2 2 2 2 2 2 2 2
3 3 3 c d d
c d d
3 3 3 j
j
n
c c c c c
Air H2O
O2 He
2145-09 (SI)
n-C9 n-C10 N2
n-C8 CO2 H2S
C2
=
C3
=
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14. NOTES FOR GPA STANDARD 2145-08 (SI)
a
Component Mole Fraction (x i) Molar Mass (M ) x i·M
nitrogen 0.78102 28.0134 21.87903
oxygen 0.20946 31.9988 6.70247
argon 0.00916 39.948 0.365924
carbon dioxide 0.00033 44.0095 0.014523
neon 0.0000182 20.1797 0.000367
helium 0.0000052 4.0026 0.000021
methane 0.0000015 16.0425 0.000024
krypton 0.0000011 83.798 0.000092
hydrogen 0.0000005 2.01588 0.000001
nitrous oxide 0.0000003 44.0128 0.000013
carbon monoxide 0.0000002 28.0101 0.000006
xenon 0.0000001 131.293 0.000013
AIR 28.9625
b
c
d
e
f
g
h
i
j
k
l
m
n
o
Algebraically derived from the absolute density of the liquid
Gas at T = 288.15 K and liquid at the normal boiling point
The Molar Mass of Air is fixed by GPA to be 28.9625 in order to harmonize with ISO 6976-
95, 'Natural gas -- Calculation of calorific value, density, relative density and Wobbe index
from composition' and AGA 5-07, 'Fuel Gas Energy Metering'. Individual components in Air
may change over time based on empirical data but the Molar Mass of Air, calculated from
the table shown below, will remain constant within this document for the purposes of, but
not limited to, the calculation of Gas Relative Density. The information in the table below
should not be used for individual component calculations. For information on individual
components refer to the appropriate Component Data Table. AGA 5-07 TABLE 7.17.1
follows.
Shaded values were estimated by GPA for the hypothetical liquid state, and were not re-
evaluated in this revision of GPA-2145.
The referenced temperature is above the critical temperature.
The property is that of the liquid component at saturation pressure rather than at 101.325
k
Average value from octane numbers using more than one sample
Enthalpy of sublimation
For components not listed in GPA-2145, the property values listed in TP-17 may be used.
Molar Mass of Dry Atmospheric Air (g)
The basis for gross heating value is dry gas at T = 288.15 K and p = 101.325 kPa based
upon the ideal reaction. See GPA 2172 for conversion to other bases. Conversion of
enthalpies of combustion at T = 298.15 K from reference 3 were converted to the conditions
specified here with the property values from reference 2. Heating values for H2S are based on
SO2(g) and H2O as products.
Enthalpy of vaporization to the ideal-gas state
Values are based on an oxygen mole fraction of 0.20946 for air.
The + sign and number specify the number of cm
3
of TEL (tetraethyl lead) added per gallon
to achieve the ASTM octane number of 100, corresponding to that of 2,2,4-trimethylpentane.
Densities of liquid at the normal boiling temperature
Gas constant R = 8.314472 J mol-1
K
-1
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15. References
1 M.E. Wieser, Pure Appl. Chem., 78, 2051-2066, 2006. All molar masses are listed with 4
decimal places without consideration of their uncertainties past the third decimal point.
2 E.W. Lemmon, M.L. Huber, and M.O. McLinden, Reference Fluid and Thermodynamic
and Transport Properties (REFPROP), NIST Standard Reference Database 23 (Version 8,
2007). NIST Standard Reference Data Program, Gaithersburg, MD. This database includes
the "The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water
Substance for General and Scientific Use," J. Phys. Chem. Ref. Data , 31(2), 387-535,
2002.
3 A.F. Kazakov, C.D. Muzny, R.D. Chirico, V. Diky, R.A. Stevenson, and M. Frenkel,
NIST/TRC Web Thermo Tables (WTT) - Professional Edition, NIST Standard Reference
Subscription Database 3 (Version 1, 2007). NIST Standard Reference Data Program,
Gaithersburg, MD.
The critically evaluated enthalpies of combustion from WTT are all for T = 298.15 K with
liquid water as a product, in accord with how the values are determined experimentally.
Enthalpies of combustion for the hydrocarbon gases are based upon the following general
reaction:
Hydrocarbon(gas) + oxygen(gas) = carbon dioxide(gas) + water(liquid)
Values (in J/g of hydrocarbon) used to derive the quantities listed in GPA-2145 are:
methane (-55517), ethane (-51903), propane (-50325), i-butane (-49347),
n-butane (-49505), ethylene (-50303), and propylene (-48907).
Enthalpies of combustion for the hydrocarbon liquids are based upon the following general
reaction:
Hydrocarbon(liquid) + oxygen(gas) = carbon dioxide(gas) + water(liquid)
Values (in J/g of hydrocarbon) used to derive the quantities listed in GPA-2145 are:
i-pentane (-48560), n-pentane (-48635), n-hexane (-48310), n-heptane (-48071),
n-octane (-47888), n-nonane (-47753), and n-decane (-47640).
The enthalpy of combustion for hydrogen sulfide is based upon the following reaction:
Hydrogen sulfide(gas) + 1.5 oxygen(gas) = sulfur dioxide(gas) + water(liquid)
The value (in J/g of hydrogen sulfide) is -16490.5.
4 Engineering Sciences Data Unit, "Fire Hazard Properties: Flash Points, Flammability
Limits and Autoignition Temperatures," ESDU 82030, September 1983.
5 E.F. Obert, "Internal Combustion Engines and Air Pollution," Harper & Row: NewYork,
1973.
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