Gases - Specific Gravities

Specific gravity of air, ammonia, butadiene, carbon dioxide, carbon monoxide and some other common gases

The specific gravity of some common gases can be found in the table below:

Gas Specific Gravity1)
- SG -
Acetylene (ethyne) - C2H2 0.90
Air1) 1.000
Alcohol vapor 1.601
Ammonia - NH3 0.59
Argon - Ar 1.38
Arsine 2.69
Benzene - C6H6 2.6961
Blast Furnace gas 1.02
Butadiene - C4H6 1.87
Butane - C4H10 2.0061
1-Butene (Butylene)- C4H8 1.94
Isobutene - C4H8 1.94
Carbon dioxide - CO2 1.5189
Carbon monoxide - CO 0.9667
Carbureted Water Gas 0.63
Chlorine - Cl2 2.486
Coke Oven Gas 0.44
Cyclobutane 1.938
Cyclopentane 2.422
Cyclopropane 1.451
Decane 4.915
Deutrium - D2 0.070
Digestive Gas (Sewage or Biogas) 0.8
Ethane - C2H6 1.0378
Ether vapor 2.586
Ethyl Chloride - C2H5Cl 2.23
Ethylene (Ethene) - C2H4 0.9683
Fluorine 1.31
Helium - He 0.138
Heptanes 3.459
Hexane 2.973
Hydrogen 0.0696
Hydrogen chloride - HCl 1.268
Hydrogen sulfide - H2S 1.1763
Hydrofluoric acid 2.370
Hydrochloric acid 1.261
Illuminating gas 0.4
Isobutane 2.01
Isopentane 2.48
Krypton 2.89
Marsh gas 0.555
Mercury vapor 6.940
Methane - CH4 0.5537
Methyl Chloride 1.74
Natural Gas (typical) 0.60 - 0.70
Neon 0.697
Nitric oxide - NO 1.037
Nitrogen - N2 (pure) 0.9669
Nitrogen - N2 (atmospheric) 0.9723
Nitrous oxide - N2O 1.530
Nonane 4.428
Octane 3.944
Oxygen - O2 1.1044
Ozone 1.660
Pentane 2.487
Phosgene 1.39
Propane - C3H8 1.5219
Propene (Propylene) - C3H6 1.4523
R-11 4.742
R-12 4.174
R-22 2.985
R-114 5.9
R-123 5.279
R-134a 3.522
Sasol 0.42
Silane 1.11
Sulfur Dioxide - SO2 2.264
Toluene-Methylbenzene 3.1082
Water gas (bituminous) 0.71
Water vapor 0.6218
Xenon 4.53

1) NTP - Normal Temperature and Pressure - is defined as air at 20oC (293.15 K, 68oF) and 1 atm ( 101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)

Since specific gravity is the ratio between the density (mass per unit volume) of the actual gas and the density of air, specific gravity has no dimension. The density of air at NTP is 1.205 kg/m3.

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