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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Study period:
march 2000
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Version / remarks:
Annex I
Principles of method if other than guideline:
Calculation model. Software: MPBPWIN (Syracuse REsaerch Corporation, NY, USA, Version 1.31)
GLP compliance:
no
Type of method:
other: Calculation
Temp.:
20 °C
Vapour pressure:
< 0 hPa

In the first step, the vapour pressure of the free acids (2-Hydroxy-2-sulfinato acetic acid, 2-Hydroxy-2-sulfonato acetic acid, and sulphurous acid), in the second step the vapour pressure of the coresponding sodium salts have been determined.

 name

2-Hydroxy-2-sulfinato acetic acid, disodium salt

2-Hydroxy-2-sulfonato acetic acid, disodium salt

sulphourous acid, disodium salt

 formula  Na2[SOO-CHOH-COO]   Na2[SOOO-CHOH-COO]  Na2SO3
 vapour pressure; free acid (in Pa)  1.07 * 10 -5   4.9 * 10 -6  9.05 * 10 -16 

vapour pressure; sodium salt (in Pa)

 2.96 * 10 -11  1.48 * 10 -11    1.12 * 10 -17

The summarized calculations show, that already for the free acids of the constituents and impurities of the substance vapour pressures markedly below 10 -5 Pa are to be expected.

The vapour pressure of the substance can be deluced from the calculation basis:  < 1 * 10 -10 Pa respectively <1 * 10-12 hPa

Executive summary:

An expermintal study does not need to be conducted if the melting point is above 300 °C. If the melting point is between 200 °C and 300 °C, a limit value based on measurement or a recognised calculation method is sufficient. Since there is no defined melting point respectively decomposition occurs at temeperatures < 207 °C and due to the high concentration of water of crystallisation, the vapour pressure was determined by calculation.

The vapour pressure of the substance can be deluced from the calculation basis:  < 1 * 10-10Pa respectively <1 * 10-12hPa

Description of key information

The vapour pressure of the substance is <1 * 10-12 hPa at 25°C

Key value for chemical safety assessment

Vapour pressure:
0 hPa
at the temperature of:
20 °C

Additional information

The vapour pressure of the test item was determined to be 6.5 hPa at 25 °C. This value doesn't correlate with the data based on a calculation (< 10exp(-10) Pa). The result is adulterated due to the content of water (20 %) based on a substance specification that is not any longer valid since 2000. Therefore the study has to be disregarded.

If the melting point is between 200 °C and 300 °C, a limit value based on measurement or a recognised calculation method is sufficient. Since there is no defined melting point respectively decomposition occurs at temperatures < 207 °C, the calculated vapour pressure will be used as key value for further calculations: <1 * 10exp(-12) hPa at 25°C.