The other ingredient-the "tar"-is a mixture of very heavy hydrocarbons known as bitumen.

Thermogenically-produced supplies of heavy hydrocarbons are common there.

The gas methane is the lightest hydrocarbon; heavier hydrocarbons are the main components of smog.

Purified gas consisted of hydrogen, methane, carbonic oxide, heavy hydrocarbon, and nitrogen.

The liquefaction process involves removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream.

This process may have limited applicability because it is said to incur the loss of butanes and heavier hydrocarbons.

A disadvantage for many applications is that methane absorbs relatively weakly compared to heavier hydrocarbons, leading to large inconsistencies of calibration.

Heavier crude oils contain a higher proportion of heavy hydrocarbons composed of longer carbon chains.

Because some of the heavy hydrocarbons are denser than water, they have seeped through 27 feet of soil down to bedrock.

The next heavier hydrocarbon, ethane, has the chemical formula CH and is a slightly denser gas.