Propane (C3H8)is a colourless, odourless, easily liquefied, gaseous hydrocarbon (compound of carbon and hydrogen),the third member of the paraffin series following methane and ethane. It is separated from light crude oil, natural gas, and is a by-product of petroleum refining. Propane is commercially available as liquefied propane or as a major constituent of liquefied petroleum gas (LPG).
Although a gas at atmospheric pressure, propane has a boiling point of -42.1 C (-43.8 F) and thus is liquefied under elevated pressures. It therefore is transported and handled as a liquid in cylinders and tanks. In this form, alone or mixed with liquid butane, it has great importance as a fuel for domestic and industrial/commercial uses and for internal-combustion engines.
The following properties and combustion data have been taken from various sources and the values shown are for an average commercial grade of propane. It should be kept in mind that the commercial grades can vary and, therefore, the values in the tables will also vary.
Extracted from CAN/CGA-B149.2-M95 Propane Installation Code.
| Chemical Formula | C3H8 |
| Molecular Weight | 44.06 |
| Freezing Point (F) | -310 |
| Freezing Point (C) | -190 |
| Boiling Point (F) | -44 |
| Boiling Point (C) | -42 |
| State at atmospheric pressure (60 f, 15 c) | Vapour |
| Relative Density (gas) | 1.52 |
| Relative Density (water) | 0.51 |
| Mass per gallon of liquid at 60 F | 5.1 lbs |
| Mass per litre of liquid at 15.5 C | 0.51 |
| BTU/cu.ft. Vapourized | 2520 |
| kJ/cubic meter Vapourized | 93,800 |
| BTU/lb. Vapourized | 21,622 |
| kJ/kg. Vapourized | 49,700 |
| Cubic ft. of vapour from 1 lb. of liquid at 60 F. | 8.5 |
| Cubic meters of vapour from 1 kg of liquid at 15 C | 0.53 |
| Cubic ft. of vapour from 1 gal. of liquid at 60 F. | 44 |
| Cubic meters of vapour from 1 litre of liquid at 15 C | 0.265 |
| Latent heat of vapourization at boiling point, BTU/gal. | 944 |
| Specific enthalpy, kJ/L | 219 |
| Cubic feet (meters) of air required to burn 1 cubic ft. (meter) of gas | 23.5 |
| Cubic feet (meters) of oxygen required to burn 1 cubic ft. (meter) of gas | 5 |
| Cubic feet of air required to burn 1 lb. of gas. | 200 |
| Cubic meters of air required to burn 1 kg. of gas. | 12.3 |
| Ignition temperature F. (C) | 920-1020 (493-549) |
| Maximum flame temperature F (C) | 3600 (1982) |
| Percentage of gas in air for maximum flame temperature | 4.4 |
| Lower and upper limits of flammability (percentage of gas in air) | 2.4 to 9.5 |
| Octane number (iso-octane 100) | 97 to 125 |
Products of complete combustion
| Carbon dioxide (cubic ft/meters) | 30 per c.ft/mtr of gas |
| Water (lb./kg) | 1.6 per lb/kg of gas |
| Water Vapour (cubic ft/meters) | 4.0 per c.ft/mtr of gas |
| Nitrogen (cubic ft/meters) | 18.5 per c.ft/mtr of gas |
| Nitrogen (lb/kg) | 12.0 per lb/kg of gas |
| Ultimate carbon dioxide percentage by volume | 13.9 |
