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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02.03.2018 - 09.05.2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
2006
Deviations:
no
GLP compliance:
no
Type of method:
effusion method: Knudsen cell
Key result
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
0.002 Pa
Key result
Test no.:
#2
Temp.:
25 °C
Vapour pressure:
0.004 Pa
Key result
Test no.:
#3
Temp.:
50 °C
Vapour pressure:
0.074 Pa

Thermal Stability

In the temperature range of 120 °C – 140 °C the test item showed an endothermic effect, which can be assigned to the melting of the test item. An exothermic effect was observed in the temperature of 340 °C – 410 °C with a decomposition energy of -110 J/g. No further thermal effects could be observed up to the maximum test temperature of 500 °C.

Table 1:    Results of the DSC-measurement

No.

Sample weight / mg

Start / °C

Energy / J/g

Remark

PN15087

9.57

120 (endothermic)
340 (exothermic)

+170
-110

Figure 2

Effusion method: Knudsen cell

The vapour pressure was measured in the temperature range of 30.4 °C to 50.7 °C. The measured vapour pressure values together with the measured temperatures are listed in Table 2:

Table 2:    Results of the Effusion method

No.

Temperature / °C

Vapour pressure / Pa

1

30.4

7.6 × 10-3

2

35.5

1.4 × 10-2

3

40.6

2.6 × 10-2

4

45.6

4.5 × 10-2

5

50.7

8.0 × 10-2

From the measured data points of the vapour pressure curve the constants A and B of the Antoine Equation were derived by regression of the data points to A = 14.2703, B = -4976.48, C = 273.15.

The vapour pressure of the test item Methylhydroquinone calculated by interpolation and extrapolation of the measured vapour pressure curve for the temperatures 20 °C, 25 °C and 50 °C, according to Regulation EC No. 440/2008 Method A.4.Vapour Pressure and OECD Test Guideline 104 (2006) is shown in Table 3:

Table 3:    Calculated vapour pressure values for 20 °C, 25 °C and 50 °C

Temperature / °C

Vapour pressure / Pa

20

2.0 × 10-3

25

3.8 × 10-3

50

7.4 × 10-2

Conclusions:
The vapor pressure of methylhydroquinone at 20°C, 25°C and 50°C is 0,002 Pa, 0,0038 Pa and 0,074 Pa, respectively.
Executive summary:

The vapour pressure of the test item Methylhydroquinone was calculated by interpolation and extrapolation of the measured vapour pressure curve for the temperatures 20 °C, 25 °C and 50 °C, according to Regulation EC No. 440/2008 Method A.4. Vapour Pressure and OECD Test Guideline 104 (2006).

Temperature / °C

Vapour pressure / Pa

20

2.0 × 10-3

25

3.8 × 10-3

50

7.4 × 10-2

Description of key information

The vapor pressure of methylhydroquinone at 20°C is 0,002 Pa, at 25°C 0,0038 Pa and at 50°C 0,074 Pa as determined by the effusion method (Knudsen cell).

Key value for chemical safety assessment

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

Additional information