Inflection Point Engineering Reference Tables

Chemical Properties Database

Molecular weight, critical properties, Antoine vapor-pressure coefficients, and ideal-gas Cp correlations for common hydrocarbons and process fluids.

Properties DB

Name Formula CAS Number MW (lb/lb-mol) Tc (K) Pc (psia) Vc (ft³/lb-mol) Acentric factor ω Normal BP (°F) Liquid density (lb/ft³) — at 60°F for liquids; at NBP for cryogens (H2,N2,CO,CH4,C2H6,C2H4) Source
Hydrogen H2 1333-74-0 2.016 33.19 190.8 0.546 -0.216 -423.17 4.42
Nitrogen N2 7727-37-9 28.014 126.21 492.3 1.418 0.04 -320.44 50.7
Carbon monoxide CO 630-08-0 28.01 134.39 506.5 1.495 0.066 -311.51 50.8
Carbon dioxide CO2 124-38-9 44.01 304.26 1069.8 2.143 0.224 -109.27 62.9
Methane CH4 74-82-8 16.043 191.05 666.4 1.586 0.0115 -259.13 26.5
Ethane C2H6 74-84-0 30.07 305.32 707.8 2.37 0.099 -127.03 22
Propane C3H8 74-98-6 44.096 369.83 617.6 3.772 0.152 -42.11 31.3
n-Butane C4H10 106-97-8 58.123 425.12 550.7 4.08 0.201 31.09 37.5
i-Butane iC4H10 75-28-5 58.123 407.81 565.4 4.255 0.176 10.94 35.9
n-Pentane C5H12 109-66-0 72.15 469.7 489.5 5.118 0.251 96.92 39.1
n-Hexane C6H14 110-54-3 86.177 507.6 436.9 5.889 0.301 155.73 41.8
n-Heptane C7H16 142-82-5 100.204 540.13 395.6 6.86 0.349 209.16 43.6
n-Octane C8H18 111-65-9 114.231 568.7 360 7.721 0.398 258.12 44.9
Benzene C6H6 71-43-2 78.114 561.75 710.3 4.204 0.212 176.35 54.8
Toluene C7H8 108-88-3 92.141 591.75 609.4 4.961 0.263 231.04 54.9
Ethylene C2H4 74-85-1 28.054 282.34 731 1.915 0.083 -155.21 22.5
Water H2O 7732-18-5 18.015 647.1 3206.2 1.04 0.344 212 62.3
Hydrogen sulfide H2S 7783-06-4 34.081 373.2 1306.8 1.989 0.1 -76.44 47
Ammonia NH3 7664-41-7 17.031 405.4 1636 1.453 0.253 -28.03 42.1
Methanol CH3OH 67-56-1 32.042 512.64 1194.6 1.888 0.566 148.35 49.1
Source: Perry's Chemical Engineers' Handbook 9th Edition; NIST WebBook; API Technical Data Book
REVISION NOTES (v2, 2026-04-11): 1. Tc column corrected from °R to K (values were already in Kelvin; label was wrong). H2 Tc corrected from 59.33 (°R) to 33.19 K (NIST WebBook). 2. Methane acentric factor corrected from -0.216 (erroneous copy of H2) to 0.0115 (Perry's 9th ed.). 3. Liquid density column header updated: cryogenic compounds (H2, N2, CO, CH4, C2H6, C2H4) are gases at 60°F; their density values are at the normal boiling point, not at 60°F. See Antoine_Eqn and Cp_Correlations sheets for additional accuracy warnings.

Antoine Eqn

Compound Formula A B C (°C) Valid Range (°C) Notes
Hydrogen H2 -2.216 50.17 -3.295 See source Perry's 9th ed
Nitrogen N2 3.43 266.4 -6.6 See source Perry's 9th ed
Carbon monoxide CO 3.592 275.5 -7.163 See source Perry's 9th ed
Carbon dioxide CO2 6.812 1301 -3.494 See source Perry's 9th ed
Methane CH4 3.822 480.4 -4.227 See source Perry's 9th ed
Ethane C2H6 3.974 663.7 -16.04 See source Perry's 9th ed
Propane C3H8 4.539 1149.4 -24.79 See source Perry's 9th ed
n-Butane C4H10 4.604 1432 -17.16 See source Perry's 9th ed
i-Butane iC4H10 4.371 1210.6 -28.06 See source Perry's 9th ed
n-Pentane C5H12 4.881 1838.7 -8.196 See source Perry's 9th ed
n-Hexane C6H14 5.054 2119.3 -33.15 See source Perry's 9th ed
n-Heptane C7H16 5.209 2477.9 -39.94 See source Perry's 9th ed
n-Octane C8H18 5.365 2862.1 -63.63 See source Perry's 9th ed
Benzene C6H6 6.905 1994.4 -41.46 See source Perry's 9th ed
Toluene C7H8 6.953 2307.7 -53.67 See source Perry's 9th ed
Ethylene C2H4 3.908 546.8 -12.87 See source Perry's 9th ed
Water H2O 8.071 1730.6 233.4 See source Perry's 9th ed
Hydrogen sulfide H2S 4.52 1162 -22.97 See source Perry's 9th ed
Ammonia NH3 7.196 1437 -35.33 See source Perry's 9th ed
Methanol CH3OH 8.161 1592.9 -34.16 See source Perry's 9th ed
Formula: log₁₀(P*) = A - B/(C+T), where P* is in mmHg and T is in °C
Source: Perry's Chemical Engineers' Handbook 9th Edition
DATA QUALITY WARNING (v2, 2026-04-11): These Antoine equation coefficients could NOT be independently verified against Perry's 9th ed. Spot-check at known NBP shows water is correct but propane, methane, and benzene give invalid results at their NBPs, suggesting wrong T range, wrong source edition, or AI-generated errors. DO NOT use Antoine coefficients from this sheet without cross-referencing Perry's 9th Table 2-8 or NIST WebBook (https://webbook.nist.gov) for the specific fluid and T range. Water coefficients verified correct (Antoine, P in mmHg, T in degC, valid 1-100 degC).

Cp Correlations

Compound Formula a b c d Valid T Range (K) Source
Hydrogen H2 6.952 0.00614 -8e-10 0 298-1500 Perry's 9th ed
Nitrogen N2 6.903 0.00149 0 0 298-1500 Perry's 9th ed
Carbon monoxide CO 6.865 0.00196 0 0 298-1500 Perry's 9th ed
Carbon dioxide CO2 8.964 0.00547 -3.32e-07 8e-11 298-1500 Perry's 9th ed
Methane CH4 4.75 0.01154 -3.23e-07 3.75e-11 298-1500 Perry's 9th ed
Ethane C2H6 3.806 0.02153 -6.87e-07 7.25e-11 298-1500 Perry's 9th ed
Propane C3H8 1.213 0.04012 -1.481e-06 1.7e-10 298-1500 Perry's 9th ed
n-Butane C4H10 -3.96 0.04271 -1.78e-06 3e-10 298-1500 Perry's 9th ed
i-Butane iC4H10 -9.157 0.05081 -2.073e-06 3.3e-10 298-1500 Perry's 9th ed
n-Pentane C5H12 -37.97 0.09963 -5.485e-06 1.147e-09 298-1500 Perry's 9th ed
n-Hexane C6H14 -98.18 0.1564 -9.84e-06 2.648e-09 298-1500 Perry's 9th ed
n-Heptane C7H16 -165.5 0.2197 -1.554e-05 4.84e-09 298-1500 Perry's 9th ed
n-Octane C8H18 -249 0.2889 -2.26e-05 7.74e-09 298-1500 Perry's 9th ed
Benzene C6H6 -33.6 0.07596 -3.838e-06 7.764e-10 298-1500 Perry's 9th ed
Toluene C7H8 -93.11 0.1145 -6.447e-06 1.465e-09 298-1500 Perry's 9th ed
Ethylene C2H4 3.806 0.01566 -3.83e-07 2.91e-11 298-1500 Perry's 9th ed
Water H2O 7.701 0.00745 2.78e-07 -3.6e-11 298-1500 Perry's 9th ed
Hydrogen sulfide H2S 6.947 0.00387 0 0 298-1500 Perry's 9th ed
Ammonia NH3 7.666 0.01058 -2.38e-07 0 298-1500 Perry's 9th ed
Methanol CH3OH 4.55 0.02676 -1.009e-06 1.568e-10 298-1500 Perry's 9th ed
Formula: Cp = a + b*T + c*T² + d*T³, where Cp is in BTU/lb-mol·°R and T is in K (Kelvin)
Source: Perry's Chemical Engineers' Handbook 9th Edition
DATA QUALITY WARNING (v2, 2026-04-11): These Cp polynomial coefficients were NOT verified against primary source (Perry's 9th ed.). Independent spot-check against NIST ideal gas Cp data shows errors ranging from ~4% (CH4 at 298K) to ~25-59% (H2O at 298K-1000K). These errors are too large for precision engineering calculations. RECOMMENDED: Cross-reference Perry's 9th Table 2-196 or use CoolProp (see 05_Scripts) for accurate Cp. The Cp/Cv ratio and heat capacity ratio (k/gamma) are especially sensitive to Cp accuracy.

Source: chem_properties_db_v4.xlsx

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