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Physical & Chemical properties

Vapour pressure

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vapour pressure
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Description of key information

The volatility of substance Fatty acids, C18-24, zinc salts is considered to be negligible.

Key value for chemical safety assessment

Additional information

The vapour pressure of a substance is defined as the saturation pressure above a solid or liquid substance. In EU method A.4, seven different measuring methods are listed for the measurement of the vapour pressure of solids and liquids. However, the vapour pressure does not need to be measured due to technical reasons if calculations indicate that the value is significantly less than 10-5 Pa. The calculated vapour pressures for fatty stearic (C18) and tetracosanoic (C24) acid zinc salts are 3.61E-013 Pa and 3.37E-018 Pa, respectively. Substance Fatty acids, C18-24, zinc salts is a solid substance (salts of fatty acids and an inorganic cation) with a melting point at 119 °C. In view of this, the volatility of this substance can therefore be safely assumed to be negligible, i. e. below the level of relevance (10-5 Pa). For purposes of comparison, data on the fatty acid moiety is considered: the HSDB lists a vapour pressure of 5.7X10-6 Pa (4.28X10-8 mm Hg) at 25°C for stearic acid, in the OECD SIDS documents on docosanoic acids a measured value (OECD Guideline 104) of 6.5X10-5 Pa at 25 °C is specified and the calculated value (EPI Suite, Version 4.11, MPBVP v1.43) for tetracosanoic acid is 1.62X10-5 Pa at 25 °C. In consideration of the salt nature of substance Fatty acids, C18-24, zinc salts, it can be anticipated that its vapour pressure is well below the values for the fatty acids, and thus negligible. Therefore, in accordance with Annex XI, sections 1 and 2 of Regulation (EC) No 1907/2006, testing does not need to be conducted for technical as well as for scientific reasons.