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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2012-11-30 - 2012-12-05
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
GLP guideline study on supporting substance. This result is read-across from 'Benzenesulfonic acid, mono-C20-24-alkyl derivs., magnesium salts' (CAS# 231297-75-9). Read-across is justified as the UVCB substance 'Benzenesulfonic acid, mono-C20-24-alkyl derivs., magnesium salts' is structurally similar to ‘Benzenesulfonic acid, di-C10-14-alkyl derivatives, calcium salts’ and has a similar molar weight. Therefore, the vapour pressure of the C20-24 mono-alkylated benzene sulfonate is expected to be similar to ‘Benzenesulfonic acid, di-C10-14-alkyl derivatives, calcium salts’ and acceptable for read-across.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE CATEGORY APPROACH
The read across follows Scenario 5 - Qualitatively and quantitatively similar effects are caused by a common compound, which is formed from all category members (as described in the 2017 Read-Across Assessment Framework document).
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
TARGET: Benzene sulfonic acid, di-C10-14-alkyl derivs., sodium salts
SOURCE: Benzenesulfonic acid, mono-C20-24-alkyl derivs., magnesium salts
3. CATEGORY APPROACH JUSTIFICATION

Linear and non-linear or branched alkylbenzene sulfonates are anionic surfactants with molecules characterized by a hydrophobic (apolar) and a hydrophilic (polar) group. As a group of chemicals, they are generally mixtures of closely related isomers and homologues. Each molecule contains an aromatic ring sulfonated at the para position and attached to either a linear or a branched alkyl chain at any position except the terminal carbons. The sulfonate group is a common functional group present in each of the category members, and is expected to exhibit similar biological activities with little influence from the length of carbon chain. The cation components of the chemicals (e.g. calcium, magnesium, sodium, or barium) are not expected to contribute significantly to the toxicity.
4. DATA MATRIX
See Read Across document attached to CSR
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
GLP compliance:
yes (incl. certificate)
Remarks:
The Department of Health of the Government of The United Kingdom
Type of method:
effusion method: vapour pressure balance
Key result
Temp.:
25 °C
Vapour pressure:
0.01 Pa
Key result
Temp.:
99 °C
Vapour pressure:
0.457 Pa

The test substance did not change in appearance under the conditions used in the determination.

Table 1. Vapour pressure data at 25 °C

Run

Log10[Vp (25 ºC)]

2

-2.07

3

-1.85

4

-1.86

5

-1.96

6

-1.89

7

-2.07

8

-2.01

9

-2.06

10

-2.10

Mean

-1.99

Vapor Pressure

1.03 x 10-2Pa

Table 2. Vapour pressure at 99 °C

Run

Log10[Vp(99 ºC)]

2

-0.154

3

-0.244

4

-0.287

5

-0.324

6

-0.365

7

-0.381

8

-0.419

9

-0.436

10

-0.454

Mean

-0.340

Vapor Pressure

0.457 Pa

Conclusions:
The study report describes a valid guideline study conducted under certificated GLP compliance. The vapour pressure was determined as 0.01 Pa at 25 °C and 0.457 Pa at 99 °C. Finally, the vapour pressure of this C20-24 mono-alkylated benzene sulfonate is expected to be similar to ‘Benzenesulfonic acid, di-C10-14-alkyl derivatives, calcium salts’ and acceptable for read-across.
Executive summary:

The vapour pressure of the magnesium sulfonate read-across substance (CAS 231297-75-9) was determined using the effusion method (vapour pressure balance) according to OECD Guideline 104 / EU Method A.4 (Tremain, 2012). The temperature was controlled electronically. Using the cross-section, a diagram ws drawn and the system was evacuated. Afterwards the shutter was opened above the sample oven, which directed the escaping vapour jet towards the scale pan. The difference in mass reading the orifice covered and uncovered is proportional to the vapor pressure at the given oven temperature. A preliminary run was undertaken over the temperature range 20 °C to 114 °C in order to provide information for a suitable temperature range for the main test. A final sequence of ten runs was started after a sample of test substance had been under vacuum for approximately 69 1/4 hours. Temperature and pressure readings were taken between 90 and 100 °C with a one hour dwell at 90 °C between runs. As result, the vapour pressure at 25 °C was determined as 0.01 Pa and at 99 °C the value is given as 0.457 Pa, respectively.

Finally, the vapour pressure of this C20-24 mono-alkylated benzene sulfonate is expected to be similar to ‘Benzenesulfonic acid, di-C10-14-alkyl derivatives, calcium salts’ and acceptable for read-across.

Description of key information

No vapor pressure studies are available for the target substance benzenesulfonic acid, di-C10 -14 -alkyl derivs., sodium salts. A study on the read across source substance benzenesulfonic acid, mono-C20-24-alkyl derivs., magnesium salts was used for reading across purposes. The vapor pressures of the read across source substance at 25 and 99°C are 0.01 and 0.457 Pa, respectively.

Key value for chemical safety assessment

Vapour pressure:
0.01 Pa
at the temperature of:
25 °C

Additional information