. "\"Mass fraction\" is used in the construction \"mass_fraction_of_X_in_Y\", where X is a material constituent of Y. It means the ratio of the mass of X to the mass of Y (including X). A chemical or biological 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 formaldehyde is CH2O."@en . "2" . "SDN:P07::CF12N365" . . "2019-03-04 17:29:46.0" . . . "false" . "" . "accepted"@en . . . . "SDN:P07::CF12N365" . "2" . . "2019-03-04 17:29:46.0" . "mass_fraction_of_formaldehyde_in_air"@en . "SDN:P07::CF12N365" .