"1" . . . "SDN:P07::CF12N284" . . "1" . . "false" . "Mass concentration means mass per unit volume and is used in the construction mass_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. The chemical formula for methane is CH4. Methane is a member of the group of hydrocarbons known as alkanes. There are standard names for the alkane group as well as for some of the individual species."@en . "SDN:P07::CF12N284" . "2009-07-06 15:41:29.0" . "accepted"@en . "" . . "2009-07-06 15:41:29.0" . "mass_concentration_of_methane_in_air"@en . . "SDN:P07::CF12N284" . . .