Dipotassium oxalate

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 Sep - 04 Sep 2015

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Obtained vapour pressure results were not sufficiently high to extrapolate to 20, 25 and 50 °C. Therefore, these values were calculated using the Antoine equation.

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Version / remarks:

adopted in 2009

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Deviations:

no

GLP compliance:

yes

Type of method:

effusion method: Knudsen cell

Temp.:

20 °C

Vapour pressure:

< 0 hPa

Remarks on result:

other: Calculated using the Antoine equation.

Temp.:

25 °C

Vapour pressure:

< 0 hPa

Remarks on result:

other: Calculated using the Antoine equation.

Temp.:

50 °C

Vapour pressure:

< 0 hPa

Remarks on result:

other: Calculated using the Antoine equation.

Results
Vapour Pressure Balance

Table 1 – Measured vapour pressures and respective temperatures

Temperature [°C]	Vapour pressure [hPa]
30	2.8E-03
40	5.0E-03
50	5.6E-06
60	2.5E-05
70	2.8E-05
80	2.6E-05

 

Data points measured at 30 °C and 40 °C were excluded from the linear regression as they were assigned to evaporating humidity.

Calculation of vapour pressure
The vapour pressures obtained were not sufficiently high to extrapolate to 20, 25 and 50 °C, thus these values were estimated using the Antoine equation (Eq. 1). For constant C a value of 273.15 was assumed and for constant B a value of -5000 was assumed. The vapour pressure at the highest measurement point (80 °C) was used for the calculation since all others were below the detection limit. Constant A in the Antoine equation (Eq.1) was calculated: A = log (2.63E-05) – [-5000/(273.15 + 80)] = 9.58

The vapour pressure at 20, 25 and 50 °C can then be calculated: log p = 9.58 + [-5000/(273.15 + T)]

Table 2 – Calculated vapour pressures

T [°C]	p [hPa]	p [Pa]
20	< 3.3E-08	< 3.3E-06
25	< 6.4E-08	< 6.4E-06
50	< 1.3E-06	< 1.3E-04

 

This is a conservative estimation of vapour pressure of the test item for the listed temperatures. To ensure a conservative approach, the vapour pressures were rounded up to the next order of magnitude to obtain final upper limit values for the vapour pressure.

Table 3 – Final upper limit values for vapour pressure

T [°C]	p [hPa]	p [Pa]
20	< 1.0E-07	< 1.0E-05
25	< 1.0E-07	< 1.0E-05
50	< 1.0E-05	< 1.0E-03

Description of key information

< 1.0E-07 hPa at 20 °C
< 1.0E-07 hPa at 25 °C
< 1.0E-05 hPa at 50 °C

(OECD 104, vapour pressure curve)

Additional information

Obtained vapour pressure results were not sufficiently high to extrapolate to 20, 25 and 50 °C. Therefore, these values were calculated using the Antoine equation.