Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Data are provided on m, p and o xylene and ethylbenzene which are the components of the streams and the data have been read across to the streams in the category. Ethylbenzene and the xylene isomers are structurally similar substances, consisting of a benzene ring with one and two methyl functional groups attached respectively; the different xylene isomers have the two methyl functional groups attached at different locations. The presence and position of the second methyl functional group on the benzene ring is not expected to change the physico-chemical properties of the substance significantly. The similarities in structure indicate that the physico-chemical properties of the components of the streams are likely to be similar. All of the components are relatively soluble in water, with limited potential to partition. The water solubility (Yalkowsky and He 2003) and the log partition coefficient (Hansch et al 1995) of ethylbenzene, m-, o- and p-xylene are 190.7 mg/L and 3.15, 146 mg/L and 3.2, 170.5 mg/L and 3.12 and 156 mg/L and 3.15, respectively.

Data on the physical properties of the xylene isomers and ethylbenzene were obtained from a number of secondary sources. The data in these secondary sources are based on a critical evaluation of peer-reviewed data and the selected values are considered to be reliable and representative of the property under investigation. Information on the review process was documented in the introduction of the source. The use of Klimisch codes (Klimisch et al. 1997) was extended to these secondary sources and a reliability code of (2) valid with restrictions was assigned when using the authoritative secondary source. For the purpose of the risk assessment (exposure assessment), the mean values of selected physico-chemical properties were used.

The flash point and boiling point of m-xylene are 27°C and 139°C, of p-xylene are 27°C and 138°C, of o-xylene are 32°C and 145°C and ethylbenzene are 18°C and 136°C respectively. The lowest flash point and boiling point used in the risk assessment are 18°C and 136°C respectively. Therefore, the streams in this category meet the criteria for flammable liquid category 2 under CLP (flash point < 23°C and boiling point >35°C).