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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2003-04-11 to 2004-05-31
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Only 4 instead of >= 5 measured values (OECD 104); equilibrium points were not repeated at decreasing pressures as demanded by OECD 104
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
1995
Qualifier:
according to
Guideline:
other: ASTM E 1719-97
Deviations:
no
Principles of method if other than guideline:
The ASTM E 1719-97 (ASTM) ebulliometry method is similar to the dynamic method in OECD Guideline 104 (1995).
GLP compliance:
yes
Type of method:
dynamic method
Key result
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
41 Pa
Remarks on result:
other: calculated based on Antoine equation
Transition / decomposition:
no

Using the Antoine equation constants calculated from the ASTM E 1719-97 (ASTM) boiling point data for n-decane (Table 1), pressures were calculated for each observed n-decane boiling point

as listed under "Calculated Pressure" in Table 2. The differences (observed - calculated pressures [kPa]) were determined as listed under "Obs'd-Calc'd Pressure" in Table 2 and plotted

against the observed pressure (abscissa, [kPa]). A regression curve was fitted to the data, resulting in the following equation:

y = ax^2 + bx +c,

a= -0.0009,

b= 0.1557,

c= -2.9498

R^2 = 0.9989

Table 1: Reported (ASTM E 1719-97) n-decane BP results

Observed Pressure

 

 

Boiling point (BP)

kPa

Log (kPa)

°C

°K

1/°K

1.00

0.0000

51.9

325.0

3.0769E-03

10.00

1.0000

101.9

375.0

2.6667E-03

30.00

1.4771

131.9

405.0

2.4691E-03

70.00

1.8451

160.9

434.0

2.3041E-03

101.30

2.0056

174.9

448.0

2.2321E-03

Antoine equation parameters

 

 

A

7.4620E+00

 

 

B

2.6581E+03

 

 

C

3.9161E+01

 

 

Table 2: n-Decane BP results

Observed Pressure

 

BP

 

Calculated Pressure*

Obs'd‑
Calc'd
Pressure

mm Hg

kPa

Log

°C

°K

1/°K

Log (kPa)

kPa

kPa

 

 

(kPa)

 

 

 

 

 

 

82.3

10.97

1.0404

105.0

378.2

2.6445E-03

1.0923

12.37

-1.39

258.3

34.44

1.5371

135.0

408.1

2.4502E-03

1.5192

33.08

1.39

548.3

73.10

1.8639

160.8

434.0

2.3044E-03

1.8436

70.14

3.35

767.3

102.30

2.0099

174.0

447.2

2.2364E-03

1.9961

99.10

3.20

*) using Antoine equation constants from Table 2

Using the relationship of the regression function, the observed pressures for 1-chloro-2,3-dimethylbenzene in Table 3 were adjusted to give the Adjusted Pressures. Antoine equation parameters (Table 3) were calculated based on these adjusted pressures and the corresponding boiling points. The absolute differences between the Adjusted and Calculated Pressures ranged from 0.17 to 1.07 kPa (see 'Deviation' in Table 3), and the absolute relative differences ranged from 0 to 7 % (see 'RD' in Table 3). The 1-chloro-2,3-dimethylbenzene vapour pressure at 20°C was calculated using the Antoine equation (parameters in Table 3), resulting in 41 Pa at 20°C (293 °K).

Tabelle 3: Results for 1-chloro-2,3-dimethylbenzene

Observed Pressure

Adjusted pressure

Boiling point

Calculated pressure

Deviation

Relative deviation [%]

mm Hg

kPa

mm Hg

kPa

°C

°K

1/°K

log (kPa)

kPa

kPa

Deviation / adjusted pressure

82

10.97

12.32

1.0907

119.1

392.3

2.5494E-03

1.059777

11.47564

0.85

7%

258

34.44

33.09

1.5198

150.9

424.1

2.3581E-03

1.529518

33.84681

-0.75

-2%

548

73.1

69.48

1.8419

176.8

450

2.2225E-03

1.848515

70.55291

-1.07

-2%

767

102.3

98.74

1.9945

190

463.2

2.1591E-03

1.993753

98.57183

0.17

0%

Antoine parameters

A

5.8473E+00

B

1.4005E+03

C

-9.9722E+01

Conclusions:
Vapour pressure (OECD 104): 41 Pa at 20°C
Executive summary:

The vapour pressure of 1-chloro-2,3-dimethylbenzene was determined according to the dynamic method (ebulliometry according to ASTM E 1719-97; similar to OECD 104) compliant with GLP.

Pressure-boiling point data pairs for n-decane given in ASTM E 1719-97 were used to calculate Antoine constants. Boiling points (BPs) at four different pressures (10.97, 34.44, 73.10, and 102.30 kPa) were determined for reference substance n-decane, and concurrently pressures for theses boiling points were calculated using the afore calcualted Antoine constants. Experimental pressure values for n-decane (abscissa) were plottet versus (observed - calculated pressue based on Antoine equation; ordinate) and fitted via polynomial regression. Then, pressure-boiling point pairs were measured for 1-chloro-2,3-dimethylbenzene (at 10.97, 34.44, 73.1, and 102.3 kPa - BP temperature range: 119.1 to 190 °C) and using the regression equation obtained before from n-decane, adjusted pressure was calculated from observed pressues. Then, Antoine constants were calculated from adjusted pressures and based on the Antoine equation, vapour pressure at 20°C was calculated.

Result: Vapour pressure for 1-chloro-2,3-dimethylbenzene at 20°C: 41 Pa.

Description of key information

Vapour pressure (OECD 104): 64.9 Pa at 20°C

Key value for chemical safety assessment

Vapour pressure:
64.9 Pa
at the temperature of:
20 °C

Additional information

The vapour pressure curve of the submission substance was determined in a Dynamic method experiment with an ebulliometer (although not explicitely mentioned experiment followed the guideline OECD 104). The Antoine constants were determined. The vapour pressure at 20°C is calculated at 64.9 Pa (Siemens 2002).

In a further supporting study the vapour pressure of 1-chloro-2,3-dimethylbenzene was determined according to the dynamic method (ebulliometry according to ASTM E 1719-97; similar to OECD 104) compliant with GLP. Pressure-boiling point data pairs for n-decane given in ASTM E 1719-97 were used to calculate Antoine constants. Boiling points (BPs). The vapour pressure for 1-chloro-2,3-dimethylbenzene at 20°C was calculated at: 41 Pa.

The more conservative (higher) value for the vapour pressure is used for risk characterisation.