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Vapour pressure

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vapour pressure
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
27 May 2010 - 3 June 2010
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was performed according to guideline. Klimisch code reduced to 2 based on read across from an analog substance.
Justification for type of information:
This substance is part of a chemical category - the justificaiton for the category is attached in section 13. The analog substance was chosen based on similarity. The low vapor pressure value is supported by QSAR as well as a consistently low vapor pressure measurement for other category members.
Reason / purpose for cross-reference:
read-across source
according to guideline
EU Method A.4 (Vapour Pressure)
GLP compliance:
yes (incl. QA statement)
Type of method:
effusion method: vapour pressure balance
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: extrapolated from plot of logPa vs. 1/K; quantity of vapour generated between 0 - 50 C was too low to measure
50 °C
Vapour pressure:
0.005 Pa
Remarks on result:
other: extrapolated from plot of logPa vs. 1/K; quantity of vapour generated between 0 - 50 C was too low to measure
70 °C
Vapour pressure:
0.024 Pa
Remarks on result:
other: 70 deg. C is the maximum use temperature of the substance

A total of 5 runs were recorded. A summary of the results is shown in Table 1 below. Raw data including temperature, mass, and pressure measurements for each of the runs are shown in attached Figures 1 - 5.

Table 1. Summary of Vapour Pressure Measurements

Run #

Vapour Pressure Values

25 C

50 C

70 C





















Mean logPa




Mean Pa




Mean kPa




The vapour pressure of the substance is 0.00042 Pa at 25 degrees C.
Executive summary:

The vapour pressure of the test substance was determined using the vapour pressure balance method following EU Method A.4 guidelines. Measurements were taken between temperatures of 105 - 115 degrees C.  This range of temperatures was selected because the quantity of vapor generated was too low to measure in the range of 0 - 50 degrees C.


A plot of logPa vs. 1/K was generated from the experimental measurements from which the vapour pressure at 25 and 50 degrees C was extrapolated.


The vapour pressure of the test substance (based on five replicate measurements) is:


0.00042 Pa at 25 deg. C

0.0046 Pa at 50 deg. C


The substance did not show a change in appearance under the conditions used in the determination.  


Description of key information

A study using ASTM method D5191 was attempted for EC 272-238-5; however, due to the physical properties (viscosity), the vapor pressure was not able to be measured via this approach (cf. supporting study: Birke 2010). Therefore, the vapor pressure for an analog substance that used a different method (EU Method A.4) is used. This is a reasonable read across because, as seen in the category justification attached in section 13, all category members have a similarly low and consistent vapor pressure (cf. ZDDP Chemical Category Justification: Appendix 3). In addition, QSAR modeling for the dissociated dithiophosphate alkyl ester, which is a conservative estimate due to the smaller molecular weight (by more than half), supports the low vapor pressure of the substance.

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
25 °C

Additional information