"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 ethyne is HC2H. Ethyne is the IUPAC name for this species, which is also commonly known as acetylene."@en . . . . "accepted"@en . "2009-07-06 15:41:29.0" . "mass_concentration_of_ethyne_in_air"@en . . "SDN:P07::CF12N256" . "false" . . . "2009-07-06 15:41:29.0" . "SDN:P07::CF12N256" . "1" . "SDN:P07::CF12N256" . . . "1" . "" .