Phosphorodithioic acid, mixed O,O-bis(sec-Bu and 1,3-dimethylbutyl) esters, zinc salts

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

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

Reliability:

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

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

effusion method: vapour pressure balance

Temp.:

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

Temp.:

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

Temp.:

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
1	-3.406	-2.344255	-1.609362
2	-3.183	-2.210785	-1.534883
3	-3.277	-2.278625	-1.584956
4	-3.497	-2.425791	-1.691464
5	-3.498	-2.434100	-1.694826
Mean logPa	-3.3722	-2.338711	-1.623098
Mean Pa	0.0004244	0.0045845	0.0238178
Mean kPa	4.2442E-07	4.5845E-06	2.3818E-05

Conclusions:

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