Densities, molecular weight and chemical formulas of some common gases can be found in the table below:
1) NTP - Normal Temperature and Pressure - is defined as 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)
2) STP - Standard Temperature and Pressure - is defined as 0oC (273.15 K, 32oF) and 1 atm (101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 30 in Hg, 760 torr)
- 1 lbm/ft3 = 16.018 kg/m3
- 1 kg/m3 = 0.0624 lbm/ft3
Note that even if pounds per cubic foot is often used as a measure of density in the U.S., pounds are really a measure of force, not mass. Slugs are the correct measure of mass. You can divide pounds per cubic foot by 32.2 for a rough value in slugs.
| Gas | Formula | Molecular weight | Density - ρ - | |
|---|---|---|---|---|
| (kg/m3) | (lb/ft3) | |||
| Acetylene (ethyne) | C2H2 | 26 | 1.0921)1.1702) | 0.06821) 0.07292) |
| Air | 29 | 1.2051) 1.2932) | 0.07521)0.08062) | |
| Ammonia | NH3 | 17.031 | 0.7171) 0.7692) | 0.04481) 0.04802) |
| Argon | Ar | 39.948 | 1.6611)1.78372) | 0.10371)0.1113532) |
| Benzene | C6H6 | 78.11 | 3.486 | 0.20643 |
| Blast furnace gas | 1.2502) | 0.07802) | ||
| Butane | C4H10 | 58.1 | 2.4891)2.52) | 0.15541) 0.1562) |
| Butylene (Butene) | C4H8 | 56.11 | 2.504 | 0.1482) |
| Carbon dioxide | CO2 | 44.01 | 1.8421)1.9772) | 0.11501)0.12342) |
| Carbon disulphide | 76.13 | |||
| Carbon monoxide | CO | 28.01 | 1.1651)1.2502) | 0.07271) 0.07802) |
| Carbureted Water Gas | 0.048 | |||
| Chlorine | Cl2 | 70.906 | 2.9941) | 0.18691) |
| Coal gas | 0.582) | |||
| Coke Oven Gas | 0.0342) | |||
| Combustion products | 1.112) | 0.0692) | ||
| Cyclohexane | 84.16 | |||
| Digester Gas (Sewage or Biogas) | 0.062 | |||
| Ethane | C2H6 | 30.07 | 1.2641) | 0.07891) |
| Ethyl Alcohol | 46.07 | |||
| Ethyl Chloride | 64.52 | |||
| Ethylene | C2H4 | 28.03 | 1.2602) | 0.07862) |
| Helium | He | 4.02 | 0.16641)0.17852) | 0.010391)0.0111432) |
| N-Heptane | 100.20 | |||
| Hexane | 86.17 | |||
| Hydrogen | H2 | 2.016 | 0.08992) | 0.00562) |
| Hydrochloric Acid | 36.47 | 1.632) | ||
| Hydrogen Chloride | HCl | 36.5 | 1.5281) | 0.09541) |
| Hydrogen Sulfide | H2S | 34.076 | 1.4341) | 0.08951) |
| Krypton | 3.742) | |||
| Methane | CH4 | 16.043 | 0.6681)0.7172) | 0.04171) 0.04472) |
| Methyl Alcohol | 32.04 | |||
| Methyl Butane | 72.15 | |||
| Methyl Chloride | 50.49 | |||
| Natural gas | 19.5 | 0.7 - 0.92) | 0.044 - 0.0562) | |
| Neon | Ne | 20.179 | 0.89992) | 0.0561792) |
| Nitric oxide | NO | 30.0 | 1.2491) | 0.07801) |
| Nitrogen | N2 | 28.02 | 1.1651)1.25062) | 0.07271) 0.0780722) |
| Nitrogen Dioxide | NO2 | 46.006 | ||
| N-Octane | 114.22 | |||
| Nitrous Oxide | N2O | 44.013 | 0.1141) | |
| Nitrous Trioxide | NO3 | 62.005 | ||
| Oxygen | O2 | 32 | 1.3311) 1.42902) | 0.08311) 0.0892102) |
| Ozone | O3 | 48.0 | 2.142) | 0.125 |
| N-Pentane | 72.15 | |||
| Iso-Pentane | 72.15 | |||
| Propane | C3H8 | 44.09 | 1.8821) | 0.11751) |
| Propene (propylene) | C3H6 | 42.1 | 1.7481) | 0.10911) |
| R-11 | 137.37 | |||
| R-12 | 120.92 | |||
| R-22 | 86.48 | |||
| R-114 | 170.93 | |||
| R-123 | 152.93 | |||
| R-134a | 102.03 | |||
| Sasol | 0.032 | |||
| Sulfur | S | 32.06 | 0.135 | |
| Sulfur Dioxide | SO2 | 64.06 | 2.2791) 2.9262) | 0.17031) 0.18282) |
| Sulfur Trioxide | SO3 | 80.062 | ||
| Sulfuric Oxide | SO | 48.063 | ||
| Toluene | C7H8 | 92.141 | 4.111 | 0.2435 |
| Water Vapor, steam | H2O | 18.016 | 0.804 | 0.048 |
| Water gas (bituminous) | 0.054 | |||
| Xenon | 5.862) | |||