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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to other study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
equivalent or similar to
Guideline:
EU Method A.4 (Vapour Pressure)
Type of method:
static method
Key result
Temp.:
293.15 K
Vapour pressure:
7.09 kPa
Remarks on result:
other: (20°C)

The experimental vapor pressure data for TFE in the range 293.15 to 363.15 K are shown in the following table:

T (K) P (kPa)
293,15 7,09
303,15 12,74
313,15 21,70
323,15 35,60
333,15 56,50
343,15 86,54
353,15 128,51
363,15 186,02

To utilize the data in a wide temperature range, the existing vapor pressure data (Sauermann et al., 1993) in the range 348-443 K combined with the results in the table were fitted to a Wagner-type equation:

ln (P/Pc) = (Tc / T) x (-9.13279X + 3.07541X1.5 -8.42048X2.5 + 3.49555X5)

where Pc = 4.87 MPa and Tc = 499.29 K are the critical pressure (Sauermann et al., 1993) and temperature (Baehr et al., 1989), and X = 1 - (T/Tc).
The root mean squared deviation is 0.16%.

To compare the present experimental data with the literature, the deviation has been calculated. For the literature data examined in the publication, the maximum mean deviation was 2.7%.

Conclusions:
The substance 2,2,2-Trifluoroethanol (TFE) is considered as a volatile organic compound (V.O.C.) according to Directive 1999/13/EC criteria.
Executive summary:

Measurements of eight vapor pressures of 2,2,2-trifluoroethanol, for temperatures between 20 and 90°C, were conducted using the static method. This experiment provides a value of 7.09 kPa at 20°C. Results were fitted to a Wagner-type equation.

Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Reason / purpose:
reference to other study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
equivalent or similar to
Guideline:
EU Method A.4 (Vapour Pressure)
Type of method:
static method
Key result
Temp.:
20 °C
Vapour pressure:
7 023 Pa

The table below shows the vapor pressures as a function of temperature determined from two samples freshly distilled into the system.

Temperature (°C) Vapor pressure (mm)
-0,40 13,55
0,30 13,80
2,25 16,05
4,10 18,55
5,85 21,00
7,55 23,55
8,75 25,60
9,30 26,50
11,10 29,90
12,40 32,85
15,00 38,65
16,80 43,15
19,80 52,05
20,60 54,40
23,10 63,35
25,40 72,50

The best straight line through the points of a plot of log (pressure) versus reciprocal temperature was computed by the method of least squares, the data being fitted to the equation:

log P = 9.651 - 2325/T

where P = vapor pressure in mm, and T is absolute temperature.

The probable error of estimate of a calculated log P is 2.92 10-3.

Conclusions:
The substance 2,2,2-Trifluoroethanol (TFE) is considered as a volatile organic compound (V.O.C.) according to Directive 1999/13/EC criteria.
Executive summary:

Measurements of sixteen vapor pressures of 2,2,2-trifluoroethanol, for temperatures between -0.40 and 25.40°C, were conducted using an apparatus that can be related to the static method. Results were fitted to a linear regression equation, which provides an interpolated value of 7023 Pa at 20°C.

Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The measurements were conducted according to the static method, however, the results are out of the recommended range of the method, according to the guideline; moreover no result is provided at ambient temperature.
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
equivalent or similar to
Guideline:
EU Method A.4 (Vapour Pressure)
Type of method:
static method
Key result
Temp.:
20 °C
Vapour pressure:
7.1 kPa
Remarks on result:
other: extrapolated by Wagner-type equation
Temp.:
20 °C
Vapour pressure:
11.1 kPa
Remarks on result:
other: extrapolated by linear regression

Forty-three experimental values of the vapor pressure are given in the table below:

T (K) p (kPa) T (K) p (kPa) T (K) p (kPa) T (K) p (kPa)
353,15 128,96 413,15 833,19 463,15 2520,35 495,15 4521,7
353,15 128,98 413,15 833,34 463,15 2520,51 495,15 4520,9
363,15 186,09 423,15 1066,57 473,15 3047,8 495,15 4520,8
363,15 186,07 423,15 1066,60 473,15 3047,6 497,15 4681,4
373,15 261,82 433,15 1345,75 478,15 3341,6 497,15 4681,6
383,15 360,01 433,15 1345,77 478,15 3341,6 497,15 4681,2
383,15 360,16 443,15 1676,63 483,15 3657,6 498,15 4764,1
393,15 484,95 443,15 1676,84 483,15 3657,7 498,15 4764,5
393,15 485,02 453,15 2065,92 488,15 3998,0 499,15 4849,1
403,15 641,16 453,15 2066,09 488,15 3998,1 499,15 4849,1
403,15 641,26 493,15 4365,2
493,15 4365,4

In the publication, the data were fitted to a vapor pressure Wagner-type equation with four coefficients, taking into account the critical properties. The average and maximum of the relative deviations are 0.077x10-3and 0.240x10-3, respectively.

As recommended by the guidelines (OECD104/EC A4), the equation of log p = f (1/T) was recalculated from the above data, and found to be:

log p = -1878.7/T + 10.45 (R2= 0.999)

The values at 20°C (293.15 K) were extrapolated from these equations.

Conclusions:
The substance 2,2,2-Trifluoroethanol (TFE) is considered as a volatile organic compound (V.O.C.) according to Directive 1999/13/EC criteria.
Executive summary:

Forty-three vapor pressures were measured for temperatures from the boiling point (ca 80°C) to the critical point (226°C) of 2,2,2-trifluoroethanol. These data were obtained with a phase-equilibrium cell designed for precise static measurements at pressures up to 20 MPa. Results were fitted to a Wagner-type equation. This relashionship provides an extrapolated value of 7.1 kPa at 20°C. Considering a linear regression as recommended by the guidelines, a consistent result of 11.1 kPa at 20°C is obtained.

Endpoint:
vapour pressure
Type of information:
not specified
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
secondary literature
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Temp.:
20 °C
Vapour pressure:
72 mBar
Conclusions:
The substance 2,2,2-Trifluoroethanol (TFE) is considered as a volatile organic compound (V.O.C.) according to Directive 1999/13/EC criteria.
Executive summary:

The german GESTIS database provides information on hazardous substances, including some physico-chemical properties; a Vapour Pressure of 7200 Pa at 20°C is cited for the substance 2,2,2-Trifluoroethanol.

Description of key information

Experimental results: 7.09 kPa at 20°C (measured), 7023 Pa at 20°C (interpolated), 7.1 kPa at 20°C (extrapolated)
Literature data: 7200 Pa at 20°C (Gestis database)

Key value for chemical safety assessment

Vapour pressure:
7.1 kPa
at the temperature of:
20 °C

Additional information

Three publications describing experimental measurements with the static method, and covering temperatures between -0.40 and 226°C are presented.

Chaudhari 1995 is considered as the key study, as information is sufficient to ensure reliability, and the vapour pressure was determined at 20°C exactly (7.09 kPa).

Meeks 1967 is acceptable despite short description, and the reference temperature is within the measuring range.

Baehr 1989 conducted experimentation at elevated temperatures, above the boiling point, and vapour pressure results are out of the range for the method, based on the guideline recommendations. Nevertheless, when the data are fitted to a Wagner-type equation, the extrapolated value at 20°C is fully consistent with the two previous references (7.1 kPa). If calculated from the standard linear regression of log P = f(1/T), the extrapolation is in the same magnitude of order (11.1 kPa), but it will not be taken into account for the key value, as considered less precise (compared to other experimental results, and due to the change in physical state).

Supporting literature data from the german Gestis database is also consistent with the above experimental data: 7200 Pa at 20°C.

The retained key value will be the arimethic mean of the four results presented above.