Liquefied petroleum gas is the mixture of butane and propane in the liquid form. Mainly it consists small amount of propylene and butylene in it. Liquefied gas is used for heating purposes and fuel for cars. Also they use it in the producing of sprays and cooler gas for refrigerators and freezers.
LPG is the additional product in refineries which comes from refining crude oil and purification of natural gas. Its thermal value is 46.1 megajoule per kilogram which is more productive than gasoline and oil in the same weight. But its thermal value is less in the same volume because it is a gas and have less density. each liter of liquefied gas is 500-580 grams and each liter of gasoline weights 710-770 grams. This gas turns into liquid in 21 degrees Celsius under 8 kilograms per square centimeter pressure. In the production process it has no smell, color or even taste so because of safety reasons they add sulfuric compounds to it such as; mercaptan (including ethyl mercaptan and methyl mercaptan).
You should not mix LPG with LNG. LNG is actually the natural gas which is turned into liquid for easier and cheaper transportation. CNG is in fact the natural gas which is compressed for less volume.
LIQUEFIED PETROEUM GAS Analysis 03001