A highly compressible, highly expansible mixture ot hydrocarbons having a low specific gravity and occurring naturally in a gaseous form. The principal component gases of natural gas, with typical percentages, are –
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<TD ALIGN=Left>methane</TD> <TD ALIGN=Right>80.0%</TD>
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<TD ALIGN=Left>ethane</TD> <TD ALIGN=Right>7.0%</TD>
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<TD ALIGN=Left>propane</TD> <TD ALIGN=Right>6.0%</TD>
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<TD ALIGN=Left>isobutane</TD> <TD ALIGN=Right>1.5%</TD>
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<TD ALIGN=Left>butane</TD> <TD ALIGN=Right>2.5%</TD>
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<TD ALIGN=Left>pentane plus</TD> <TD ALIGN=Right>3.0%</TD>
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In addition to these gases, natural gas may contain appreciable quantities of nitrogen, helium, carbon dioxide, and contaminants (as hydrogen sulfide and water vapor). Although gaseous at normal temperatures and pressures, certain of the gases comprising the mixture that is natural gas are variable in form and may be found either as gases or as liquids under suitable conditions of temperature and pressure.