Niobium doped titanium dioxide

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-11-05 to 2018-11-06

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

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Version / remarks:

European Commission Regulations (EC) No.440/2008 and No. 761/2009

Deviations:

no

GLP compliance:

no

Type of method:

effusion method: Knudsen cell

Key result

Temp.:

20 °C

Vapour pressure:

< 0 Pa

Key result

Temp.:

25 °C

Vapour pressure:

< 0 Pa

Key result

Temp.:

50 °C

Vapour pressure:

< 0 Pa

The vapour pressure was measured in the temperature range of 70 °C to 120 °C. The measured vapour pressures at the corresponding temperatures are listed in Table 1. After the measurement a mass loss of < 1 % (w/w) was determined.

Table 1: Measured vapour pressures and corresponding temperatures

Temperature / °C	Vapour pressure / hPa
70	n.e.
80	n.e.
90	n.e.
100	n.e.
110	n.e.
120	n.e.

n.e.: not evaluable

Since the test did not yield vapour pressures sufficiently high to extrapolate to 20, 25 and 50'C

these values were estimated. According to the Antoine equation, the vapour pressure can be

calculated according to:

log(p / hPa)  = A + B / (C + (T / °C))

p          Vapour pressure in hPa

T          Temperature in °C

A, B, C             Antoine constants

For an extrapolation to lower temperatures a conservative assumption of the Antoine constant C is 273.15. This results in a linear dependency of log(p) of the inverse Temperature 1/T (in K). Values for the resulting slope of the Antoine equation (constant B) for substances of high molecular weight, which can be derived from literature values (e.g. Handbook of Chemistry and Physics) are lower than -5000. Thus, for a conservative estimation of the vapour pressure of the test item at 20, 25 and 50 °C, a value of -5000 for constant B and a value of 273.15 for constant C, respectively, were used.

The detection limit (1 x 10^-5 hPa) at the highest measurement point (120 °C) was used for the calculation as all measured vapour pressures were below the detection limit.

Based on this assumption, the constant A of the Antoine equation was calculated according to:

A = log(p/hPa) – (-5000)/(273.15 + (T / °C)) = 1log(10^-5) – (-5000)/(273.15 + 120) = 7.72

Subsequently, the vapour pressure at 20, 25 and 50 °C can be calculated with the Antoine equation as follows:

log(p/hPa) = 7.72 + (-5000)/(273.15 + (T / °C))

Table 2: Calculated vapour pressure at 20, 25 and 50 °C

T / °C	p / hPa	p / Pa
20	< 4.6 x 10^-10	< 4.6 x 10^-8
25	< 8.9 x 10^-10	< 8.9 x 10^-8
50	< 1.8 x 10^-8	< 1.8 x 10^-6

This is a conservative estimation of the vapour pressure of the test item for the listed temperatures.

Conclusions:

The estimated vapour pressure of the test item at 20 °C is below 4.6 x 10-8 Pa (reference 4.6-1).

Executive summary:

The vapour pressure of test item has been determined in an experimental study according to OECD Guideline n. 104 (2006) and European Commission Regulations (EC) No.44012008 and No. 761/2009, method A.4. A Knudsen cell (effusion method) was used to measure the vapour pressure of the test item in the temperature range of 70 °C to 120 °C. The vapour pressure was not evaluable in the whole range. Therefore, conservative assumptions for the Antoine constants were used to estimate the vapour pressure at 20, 25 and 50 °C. The estimated values are: 20 °C: < 4.6 x 10^-8, 25 °C: < 8.9 x 10^-8, 50 °C: < 1.8 x 10^-6.

Description of key information

The estimated vapour pressure of the test item at 20 °C is below 4.6 x 10^-8 Pa (reference 4.6-1).

Key value for chemical safety assessment

Vapour pressure:

0 Pa

at the temperature of:

20 °C

Additional information

The vapour pressure of test item has been determined in an experimental study according to OECD Guideline n. 104 (2006) and European Commission Regulations (EC) No.44012008 and No. 761/2009, method A.4. A Knudsen cell (effusion method) was used to measure the vapour pressure of the test item in the temperature range of 70 °C to 120 °C. The vapour pressure was not evaluable in the whole range. Therefore, conservative assumptions for the Antoine constants were used to estimate the vapour pressure at 20, 25 and 50 °C. The estimated values are: 20 °C: < 4.6 x 10^-8, 25 °C: < 8.9 x 10^-8, 50 °C: < 1.8 x 10^-6.