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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study is not an experimental one. Instead, calculation was used to extrapolate vapour pressure at 20 and 25°C. The data obtained appears consistent with the handbooks values measured at higher temperatures.
Qualifier:
no guideline available
Principles of method if other than guideline:
Vapour pressures at 20 and 25°C were estimated by calculation.
GLP compliance:
not specified
Temp.:
25 °C
Vapour pressure:
ca. 0.005 kPa

From the equation above mentionned, Vp = 0.003 kPa at 20°C (value adopted by HSDB), and  0.005 kPa at 25°C.

However, since Pyrocatechol has a melting point of 105°C (<118.5-245.5°C used for the generation of the equation), the extrapolated VP refers to a 

 "super-cooled" liquid, and not the solid. The "super-cooled" value can be further extrapolated to the solid-phase VP using various methods which  

will lower the super-cooled value by a factor of 6 to 11 (Bill Meylan,  personal communication).

Conclusions:
Catechol presents an extrapolated vapour pressure value of 0.005 hPa at 25°C.
Executive summary:

In this study, the authors developped a equation to extrapolate the vapour pressure at 25°C from values measured at temperatures ranging from 118.5 to 245.5°C. By doing so, they reported a vapour pressure of 0.005 kPa at 25°C for catechol.

Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data comes from peer-reviewed handbooks cited among "reference books containing peer-reviewed physico-chemical data" in the ECHA guidance document on information requirements and chemical safety assessment (R.7a).
Reason / purpose for cross-reference:
reference to same study
Qualifier:
no guideline available
Principles of method if other than guideline:
Measured data but no information on the method.
GLP compliance:
not specified
Temp.:
104 °C
Vapour pressure:
6.66 hPa
Temp.:
118.3 °C
Vapour pressure:
13.3 hPa
Temp.:
150.6 °C
Vapour pressure:
53.3 hPa
Temp.:
176 °C
Vapour pressure:
133 hPa
Temp.:
197.7 °C
Vapour pressure:
266 hPa
Temp.:
221.5 °C
Vapour pressure:
533 hPa
Conclusions:
Catechol presents a vapour pressure ranging from 6.66 to 533 hPa in the temperature range from 104 to 221.5°C.
Executive summary:

Several peer-reviewed handbooks report vapour pressure ranging from 6.66 to 533 hPa in the temperature range from 104 to 221.5°C for catechol.

Description of key information

Range of vapour pressure:
0.05 hPa at 25°C;
6.66 hPa at 104°C;
13.3 hPa at 118.3°C;
53.3 hPa at 150.6°C;
133 hPa at 176°C;
266 hPa at 197.7°C;
533 hPa at 221.5°C

Key value for chemical safety assessment

Vapour pressure:
0.05 hPa
at the temperature of:
25 °C

Additional information

Several peer-reviewed handbooks and a publication give consistent values in a range of temperatures between 25 and 221.5°C. No key study was chosen and a "weight of evidence" approach was applied.