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Vapour pressure

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Description of key information

< 35 Pa at 20 °C

Key value for chemical safety assessment

Additional information

In order to estimate the vapour pressure of the substance sulfuric acid, mono-C8-14 alkyl esters, ammonium salts, compds. with triethanolamine (CAS No. 96690-74-3), the results calculated for sulfuric acid, mono-C8-14 alkyl esters, ammonium salts (CAS No. 90583-10-1) and for sulfuric acid, mono-C8-14 alkyl esters, compound with triethanolamine (CAS No. 85665-45-8) are used in a weight of evidence approach. The two read-across substances can be seen as complementary to each other, providing both counter ions present in the target substance. The calculated maximum values are of similar order of magnitude (6 Pa for 90583-10-1 and 35 Pa for 85665-45-8) and it can be concluded that the vapour pressure of the target substance is lower than the higher of these values, i.e. 35 Pa. This value is accepted to be used for a chemical safety assessment.

The vapour pressures of read-across substances were determined with the use of Grain-Watson estimation as outlined in the OECD Guildeline 104. The experimental results of the DSC method were not in the appropriate validity range with respect to this method. The calculations are based on the lowest possible boiling temperatures, which in fact are probably decomposition temperatures. In a peer reviewed SIDS Initial Assessment Profile (SIAM 25, 17 -18 October, 2007) it is stated that: "As ionic substances, all members of this category have extremely low vapour pressures. Calculated values are in the ranges 1E-11 hPa to 1E-15 hPa (C8 -18 alkyl sulfates) (...) Therefore, they decompose before reaching their theoretical boiling points". Thus, the obtained values should be considered upper limits of the vapour pressure. The higher one of them is accepted for the risk assessment calculations in the sense of a "worst-case scenario".