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Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 December 2020 - 03 March 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study conducted according to OECD 104 and EU A.4 guidelines, under GLP without deviation and with certificate of analysis included.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

2018-11-15

Type of method:

effusion method: Knudsen cell

Key result

Temp.:

298.15 °C

Vapour pressure:

ca. 0.99 Pa

Remarks on result:

other: Mean from trials 2 and 3

Key result

Temp.:

293.15 K

Vapour pressure:

ca. 0.54 Pa

Remarks on result:

other: Mean from trials 2 and 3

Test no.:

#1

Temp.:

293.15 K

Vapour pressure:

ca. 0.97 Pa

Remarks on result:

other: Trial 1

Test no.:

#1

Temp.:

298.15 K

Vapour pressure:

ca. 1.57 Pa

Remarks on result:

other: Trial 1

Test no.:

#2

Temp.:

293.15 K

Vapour pressure:

ca. 0.59 Pa

Remarks on result:

other: Trial 2

Test no.:

#2

Temp.:

298.15 K

Vapour pressure:

ca. 1.05 Pa

Remarks on result:

other: Trial 2

Test no.:

#3

Temp.:

293.15 K

Vapour pressure:

ca. 0.48 Pa

Remarks on result:

other: Trial 3

Test no.:

#3

Temp.:

298.15 K

Vapour pressure:

ca. 0.92 Pa

Remarks on result:

other: Trial 3

Results:

First trial:

Experimental results:

 

Mass loss (mg)	Mass loss duration (s)	Vapour pressure (Pa)	Temperature (K)	1/T (K-1)	Log10 (p)
0.183	600	1.5569	296.05	3.378 x 10^-3	0.1923
0.189	600	1.6160	299.05	3.344 x 10^-3	0.2085
0.286	600	2.4723	305.65	3.272 x 10^-3	0.3931
0.617	600	5.3925	312.45	3.201 x 10^-3	0.7318
1.312	600	11.5945	319.45	3.130 x 10^-3	1.0643

 

A plot of Log10 (p) versus reciprocal temperature (1/T) (with p in Pa and T in K) gives the following statistical data using an unweighted least square treatment.
Slope -3617.7
Intercept 12.329
R² 0.9619

The results obtained indicate the following vapour pressure relationship:
Log10 (p (Pa)) = -3617.7/ T (K) + 12.329
The above equation yields a vapour pressure of 0.97 Pa at 293.15 K and 1.57 Pa at 298.15 K.

Second trial:

Experimental results:

 

Mass loss (mg)	Mass loss duration (s)	Vapour pressure (Pa)	Temperature (K)	1/T (K-1)	Log10 (p)
0.101	600	0.8594	296.15	3.377 x 10^-3	-0.0658
0.142	600	1.2144	299.15	3.343 x 10^-3	0.0843
0.261	600	2.2584	306.25	3.265 x 10^-3	0.3538
0.589	600	5.1527	313.05	3.194 x 10^-3	0.7120
1.266	600	11.2072	320.55	3.120 x 10^-3	1.0495

 

A plot of Log10 (p) versus reciprocal temperature (1/T) (with p in Pa and T in K) gives the following statistical data using an unweighted least square treatment.
Slope -4321.8
Intercept 14.515
R² 0.9962

The results obtained indicate the following vapour pressure relationship:
Log10 (p (Pa)) = -4321.8 / T (K) + 14.515
The above equation yields a vapour pressure of 0.59 Pa at 293.15 K and 1.05 Pa at 298.15 K.

Third trial:

Experimental results:

 

Mass loss (mg)	Mass loss duration (s)	Vapour pressure (Pa)	Temperature (K)	1/T (K-1)	Log10 (p)
0.081	600	0.6891	296.05	3.378 x 10^-3	-0.1617
0.121	600	1.0346	299.05	3.344 x 10^-3	0.0148
0.275	600	2.3776	305.75	3.271 x 10^-3	0.3761
0.598	600	5.2273	312.55	3.199 x 10^-3	0.7183
1.283	600	11.3418	319.65	3.128 x 10^-3	1.0547

 

A plot of Log10 (p) versus reciprocal temperature (1/T) (with p in Pa and T in K) gives the following statistical data using an unweighted least square treatment.
Slope -4869.6
Intercept 16.295
R² 0.9998

The results obtained indicate the following vapour pressure relationship:
Log10 (p (Pa)) = -4869.6 / T (K) + 16.295
The above equation yields a vapour pressure of 0.48 Pa at 293.15 K and 0.92 Pa at 298.15 K.

Summary of Results:

Trial	Vapour pressure at 293.15 K	Vapour pressure at 298.15 K
1	0.97 Pa	1.57 Pa
2	0.59 Pa	1.05 Pa
3	0.48 Pa	0.92 Pa
Mean from trials 2 and 3	0.54 Pa	0.99 Pa

 

The test item did not change in appearance under the conditions used in the determination.

 

Apparatus calibration and control:

Temperature:

Temperature calibration was performed between 23 October 2020 and 27 October 2020.
Temperature calibration curve is given in Appendix II.
A control of temperature was carried out with Gallium on 15 December 2020. The obtained temperature was 30.0°C and respects the checking chart limits (reference value of 29.76°C ± 0.5°C).

Mass:

Mass control was carried out with substance Calcium oxalate on 15 December 2020. The obtained values respect the checking chart limits (1st mass-loss of 12.45% for a reference value of 12.3% ± 0.4%; 2nd mass-loss of 18.90% for a reference value of 18.8% ± 0.4%; 3rd mass-loss of 29.89% for a reference value of 29.5% ± 1.1%).

Conclusions:

In conclusion, the mean vapour pressure of test item is 0.54 Pa at 20°C and 0.99 Pa at 25°C.

Executive summary:

A study was performed to determine the vapour pressure of the test item. The method followed was designed to be compliant with the OECD guideline for the Testing of Chemicals No. 104, "Vapour pressure" (2006), 23 March 2006 and Commission Regulation No 440/2008 on test methods, Method A.4 (last Adaptation to Technical Progress by Commission Regulation (EU) 2019/1390 of 31 July 2019, with no update to the A1 method since 2009). As the test item’s prediction for vapour pressure was 0.45 Pa at 25°C (EpiSUITE prediction), the Knudsen effusion method was conducted.

In this method, the mass of the test substance flowing out per unit of time of a Knudsen cell in the form of vapour, through a micro-orifice under ultra-vacuum conditions was determined at various specified temperatures (from 22.9°C to 47.4°C). The Hertz-Knudsen equation was used to calculate the vapour pressure corresponding to the mass loss rate.
The Log10 (Vapour Pressure (Pa)) was plotted against 1/T (K) and a linear function was obtained. With this equation, the vapour pressure has been calculated for temperatures of 20°C and 25°C.

 

Three trials were conducted and five points were recorded for each trial.
Log10 (Vapour Pressure (Pa)) was plotted against reciprocal temperature and values of vapour pressure were calculated at 20°C and 25°C with the linear function parameters (slope and intercept):

 

Trial	Vapour pressure at 293.15 K	Vapour pressure at 298.15 K
1	0.97 Pa	1.57 Pa
2	0.59 Pa	1.05 Pa
3	0.48 Pa	0.92 Pa
Mean from trials 2 and 3	0.54 Pa	0.99 Pa

Calculated values from trials 2 and 3 respect validity criteria (less than 20% of difference) and the linear functions obtained own a correlation coefficient R² over 0.95.
In conclusion, the mean vapour pressure of test item is 0.54 Pa at 20°C and 0.99 Pa at 25°C.

Description of key information

Vapour Pressure: 0.99Pa at 25ºC (mean n= 3), EU Method A.4 - thermogravimetric effusion method

Key value for chemical safety assessment

Vapour pressure:

0.99 Pa

at the temperature of:

25 °C

Additional information

A study was performed to determine the vapour pressure of the test item. The method followed was designed to be compliant with the OECD guideline for the Testing of Chemicals No. 104, "Vapour pressure" (2006), 23 March 2006 and Commission Regulation No 440/2008 on test methods, Method A.4 (last Adaptation to Technical Progress by Commission Regulation (EU) 2019/1390 of 31 July 2019, with no update to the A1 method since 2009).

The mean vapour pressure of test item is 0.54 Pa at 20°C and 0.99 Pa at 25°C.