Tar bases, coal, lutidine fraction

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experimental start date: 27 January 2016, Experimental completion date: 28 January 2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Version / remarks:

2006 (isoteniscope procedure)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Version / remarks:

Commission Regulation (EC) No 440/2008, dated May 30, 2008

Deviations:

no

GLP compliance:

no

Remarks:

However, the study was performed in a test facility which has been certified to be in compliance with the principles of GLP.

Type of method:

isoteniscope

Temp.:

25 °C

Vapour pressure:

ca. 607 Pa

Remarks on result:

other: Arithmetic mean of 3 runs, extrapolated from the temperature range of 98 to 116 °C

Temp.:

20 °C

Vapour pressure:

ca. 453 Pa

Remarks on result:

other: Arithmetic mean of 3 runs, extrapolated from the temperature range of 98 to 116 °C

Temp.:

12 °C

Vapour pressure:

ca. 268 Pa

Remarks on result:

other: calculated using the approximate determination equation for the vapour pressure [Pa] in dependency of the absolute temperature [K]: Vp = 10^((-2216.2/T) + 10.2)

Transition / decomposition:

no

Remarks:

The test item did not change in appearance during testing.

Table 1: Summary of results

Run	Log Vapour Pressure		Vapour Pressure [Pa]
	at 25 °C [Pa]	at 20 °C [Pa]	at 25 °C [Pa]	at 20 °C [Pa]
1	2.778	2.650
2	2.759	2.631
3	2.813	2.688
Mean	2.783	2.656	607	453

The slope and intercept of the correlation for the relationship between Log Vp versus reciprocal temperature 1/T (Equation 1) were determined as indicated in the following Table 2.

Table 2: Regression line characteristics of the 3 determination runs

Run	Slope	SD of slope	Intercept	SD of Intercept	r²
1	-2237	±9.58	10.3	±0.0252	0.9997
2	-2231	±12.3	10.2	±0.0321	0.9994
3	-2188	±16.1	10.2	±0.0422	0.9990
Mean	-2217	n.a.	10.2	n.a.	n.a.

SD: Standard deviation

r²: Coefficient of determination

n.a.: Not applicable

This delivers the formula for the calculation of the vapour pressure on the basis of Equation 1 as follows:

Log (Vp) = (-2216.2/T) + 10.2 (Equation 2)

Where:

Vp = Vapour pressure [Pa]

T = temperature [K]

Log = decadic Logarithm; i.e. logarithm on the base of 10

By delogarithmation the Equation 2 can be transformed into an approximate determination equation for the vapour pressure in Pa in dependency of the absolute temperature in K:

Vp = 10^((-2216.2/T) + 10.2) (Equation 3)

Conclusions:

In a reliable and conclusive study according to OECD TG 104 (2006) and Method A.4 (EC) No 440/2008, the vapour pressure of the test item has been determined to be 607 Pa at 25 °C and 453 Pa at 20 °C.

Executive summary:

The vapour pressure of the test item at 20 and 25 °C was determined in a non-GLP study using the isoteniscope procedure according to the OECD TG 104 (2006) and EU A.4 (Commission Regulation (EC) No 440/2008) protocols. The experiment is considered relevant, adequate and conclusive.

Three runs were made between temperatures of 116 and 98, 116 and 100 as well as 115 and 99 °C in Run 1, 2 and 3, respectively. The vapour pressure was determined using an isoteniscope system in which the sample's vapour pressure was measured using a mercury in glass manometer. The temperature of the sample was regulated by use of a silicone oil bath. The sample was placed in the isoteniscope tube such that a portion was in each of the reservoir and the U-tube. After evacuating the vacuum arm of the manometer, the sample was boiled at a suitable temperature and pressure to allow the sample to degas, any volatile impurities being distilled into the cold-finger. After removal of impurities, the temperature and pressure of the sample were altered such that data pairs were found for which the menisci formed by the sample in the two arms of the U-tube were level. At these points, the pressure of the vapour above the sample reservoir was equal to the system pressure, measurable on the manometer. Correlation equations for the relationship between Log Vp versus reciprocal temperature 1/T were established for the three Runs.

The coefficient of determination of the regression lines were ≥ 0.999 indicating a satisfactory linearity in the measured temperature range of 98 to 116 °C.

Using an unrounded correlation equation for the relationship between Log Vp versus reciprocal temperature, the vapour pressure of the test item has been calculated to be 607 Pa at 25 °C and 453 Pa at 20 °C. According to a scheme (ECHA 2012) the test item should be placed in the “Low” volatility band for occupational exposure estimation (<500 Pa at 20 °C).

Description of key information

In a valid, reliable and conclusive study according to OECD TG 104 (2006) and Method A.4 (EC) No 440/2008, the vapour pressure of the test item has been determined to be 607 Pa at 25 °C and 453 Pa at 20 °C.

Key value for chemical safety assessment

Vapour pressure:

453 Pa

at the temperature of:

20 °C