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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
calculation (if not (Q)SAR)
Remarks:
estimated by calculation
Adequacy of study:
key study
Study period:
23 May - 3 Aug 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Principles of method if other than guideline:
Estimation procedure in accordance with the test method OECD Guideline 104 "OECD Guideline For The Testing Of Chemicals, adopted by the Council on 23 March 2006, Vapour Pressure" ANNEX Estimation Method newest version (R.S: Boethling, D. Mackay, Handbook of Property Estimation Methods for Chemicals, Lewis Publishers, 2000, Cap. 3 - Vapour Pressure, Grain-Watson Method, p.53-65) was used. This method is applied for vapour pressures between 1E+03 to 1E-07 mbar. This deviates from the older version published in OECD Guideline 104 and it was used due to the differentiation between solids and liquids, which results in a more precise estimate.
GLP compliance:
no
Type of method:
other: see "Principles of method" below. For the preliminary estimation, DSC method was used
Temp.:
20 °C
Vapour pressure:
<= 78 Pa
Remarks on result:
other: The calculation is based on the lowest possible boiling temperature

The Grain-Watson estimation was applied as outlined in the section "Any other information of materials and methods".

Description of key information

=< 78 Pa at 20 °C

Key value for chemical safety assessment

Vapour pressure:
78 Pa
at the temperature of:
20 °C

Additional information

The vapour pressure of the substance was determined with the use of Grain-Watson estimation as outlined in the OECD Guideline 104. The experimental result of the vapour pressure measurement using the DSC method was not in the appropriate validity range with respect to this method and it was discarded.

The Grain-Watson calculation is based on the lowest possible boiling temperature, which in fact is probably a decomposition temperature. In a peer reviewed SIDS Initial Assessment Profile for alkyl sulphates (structurally related to alcohols ethoxylated, sulphated; 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 sulphates) (...) Therefore, they decompose before reaching their theoretical boiling points". Thus, the obtained value should be considered an upper limit of the vapour pressure and accepted for the risk assessment calculations in the sense of a "worst-case scenario".