Liquefied Petroleum Gas or LPG's is a liquefied gas produced as a byproduct from refining petroleum. It is a generic term used to embrace several specific petroleum products known as light hydrocarbons or NGL mixes.

A hydrocarbon is a chemical compound comprised of hydrogen and carbon atoms. Like water (a single chemical that boils at a single temperature), each hydrocarbon has its own boiling temperature. This important characteristic is the most useful and used phenomenon in the petroleum industry.

Compound Boiling Temperature
ethane -127.5°F
propane -43.7°F
normal butane 10.9°F
isobutane 31.1°F






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Petroleum Hydrocarbon compounds are classified into 4 basic groups depending on their molecular structure: paraffins, olefins, napthalenes and aromatics. For our purposes, we are only interested in paraffinic hydrocarbons.

Paraffin - straight chain compounds with single bonds between the carbon atoms




- formula CnHcn+2
- also called "saturated" compounds
-methane, ethane, propane, normal butane, isobutane, pentanes...