"mass_fraction_of_hcfc142b_in_air"@en . . "SDN:P07::CF12N375" . "\"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 HCFC142b is CH3CClF2. The IUPAC name for HCFC142b is 1-chloro-1,1-difluoroethane."@en . .