Stearic acid, cobalt salt

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

JUSTIFICATION FOR READING ACROSS INFORMATION FOR VAPOUR PRESSURE
The vapour pressure of a substance is defined as the saturation pressure above a solid or liquid substance. In EU method A.4, seven different measuring methods are listed for the measurement of the vapour pressure of solids and liquids. However, the vapour pressure does not need to be measured due to technical reasons if calculations indicate that the value is significantly less than 10^-5 Pa. Stearic acid, cobalt salt is a waxy solid substance (salts of an organic acid and an inorganic cation) with a melting range of 78-82 °C. In view of this, the volatility of this substance can therefore be safely assumed to be negligible, i.e. below the level of significance (10^-5 Pa). For purposes of comparison, an atom fragment contribution method (MPBPVP™, Mean VP of Antoine and Grain method; EPI Suite™) stated following experimental determined and estimated vapour pressures for the fatty acid at 25°C (please refer to the respective study records): C16: palmitic acid (CAS # 57-10-3) at 25 °C: exp. database: 3.80E-7 mm Hg (5.07-5 Pa); estimate: 5.52E-5 mm Hg (0.00736 Pa) C17: heptadecanoic acid (CAS # 506-12-7) at 25 °C: exp. database: 6.23E-8 mm Hg (8.31E-6 Pa); estimate: 0.2782.84E-5 mm Hg (0.00379 Pa) C18: stearic acid (CAS # 57-11-4) at 25 °C: exp. database: 7.22E-7 mm Hg (9.63E-5 Pa); estimate: 8.31E-6 mm Hg (0.00111Pa). Since the vapour pressure of a substance depends among others on the chemical structure and decreases with increasing inter- and intramolecular interactions. An ionic compound such as Stearic acid, cobalt salt shows a higher strength of attraction, because of the electrostatic interaction between its positive and negative ions. This ionic interaction leads to a higher lattice energy compared with the van-der-Waals interaction of the uncharged fatty acid and consequently to a much lower vapour pressure.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Based on the above, the vapour pressure of Stearic acid, cobalt salt is considered to be negligible based on the fact that
(i) the vapour pressure of the corresponding acid is already very low (see above) and
(ii) the vapour pressure of the corresponding ionic species is considered to be magnitudes lower since the ionic bond strength is higher compared to the Van-der-Waals interactions of the uncharged molecule. In consideration of the ionic nature of this compound, it can therefore be anticipated that the vapour pressure of Stearic acid, cobalt salt is well below the value for the organic acid, and thus negligible.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source: palmitic acid, heptadecanoic acid, stearic acid (see source study records; purity is not of relevance for this endpoint)
Target: stearic acid, cobalt salt (purity is not of relevance for this endpoint)

3. ANALOGUE APPROACH JUSTIFICATION
see justification given above

4. DATA MATRIX
not required

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across: supporting information

GLP compliance:

not specified

Type of method:

other: not specified

Remarks on result:

other: please refer to the field `Justification for type of information´

Conclusions:

The vapour pressure of a substance is defined as the saturation pressure above a solid or liquid substance. In EU method A.4, seven different measuring methods are listed for the measurement of the vapour pressure of solids and liquids. However, the vapour pressure does not need to be measured due to technical reasons if calculations indicate that the value is significantly less than 10^-5 Pa. Stearic acid, cobalt salt is a waxy solid substance (salts of an organic acid and an inorganic cation) with a melting range of 78-82 °C. In view of this, the volatility of this substance can therefore be safely assumed to be negligible, i.e. below the level of significance (10^-5 Pa). For purposes of comparison, an atom fragment contribution method (MPBPVP™, Mean VP of Antoine and Grain method; EPI Suite™) stated following experimental determined and estimated vapour pressures for the fatty acid at 25°C (please refer to the respective study records): C16: palmitic acid (CAS # 57-10-3) at 25 °C: exp. database: 3.80E-7 mm Hg (5.07-5 Pa); estimate: 5.52E-5 mm Hg (0.00736 Pa) C17: heptadecanoic acid (CAS # 506-12-7) at 25 °C: exp. database: 6.23E-8 mm Hg (8.31E-6 Pa); estimate: 0.2782.84E-5 mm Hg (0.00379 Pa) C18: stearic acid (CAS # 57-11-4) at 25 °C: exp. database: 7.22E-7 mm Hg (9.63E-5 Pa); estimate: 8.31E-6 mm Hg (0.00111Pa). Since the vapour pressure of a substance depends among others on the chemical structure and decreases with increasing inter- and intramolecular interactions. An ionic compound such as Stearic acid, cobalt salt shows a higher strength of attraction, because of the electrostatic interaction between its positive and negative ions. This ionic interaction leads to a higher lattice energy compared with the van-der-Waals interaction of the uncharged fatty acid and consequently to a much lower vapour pressure.

Based on the above, the vapour pressure of Stearic acid, cobalt salt is considered to be negligible based on the fact that
(i) the vapour pressure of the corresponding acid is already very low (see above) and
(ii) the vapour pressure of the corresponding ionic species is considered to be magnitudes lower since the ionic bond strength is higher compared to the Van-der-Waals interactions of the uncharged molecule. In consideration of the ionic nature of this compound, it can therefore be anticipated that the vapour pressure of Stearic acid, cobalt salt is well below the value for the organic acid, and thus negligible.

In conclusion, the conduct of further experimental verification is considered to be neither technically nor scientifically feasible, and for the reasons stated above derogation from testing is hereby applied for.

Key value for chemical safety assessment

Vapour pressure:

0 Pa

at the temperature of:

25 °C

Additional information

This `key value for chemical safty assessment´ stated above is only used for CHESAR calculations.

The vapour pressure of a substance is defined as the saturation pressure above a solid or liquid substance. In EU method A.4, seven different measuring methods are listed for the measurement of the vapour pressure of solids and liquids. However, the vapour pressure does not need to be measured due to technical reasons if calculations indicate that the value is significantly less than 10^-5 Pa. Stearic acid, cobalt salt is a waxy solid substance (salts of an organic acid and an inorganic cation) with a melting range of 78-82 °C. In view of this, the volatility of this substance can therefore be safely assumed to be negligible, i.e. below the level of significance (10^-5 Pa). For purposes of comparison, an atom fragment contribution method (MPBPVP™, Mean VP of Antoine and Grain method; EPI Suite™) stated following experimental determined and estimated vapour pressures for the fatty acid at 25°C (please refer to the respective study records): C16: palmitic acid (CAS # 57-10-3) at 25 °C: exp. database: 3.80E-7 mm Hg (5.07-5 Pa); estimate: 5.52E-5 mm Hg (0.00736 Pa) C17: heptadecanoic acid (CAS # 506-12-7) at 25 °C: exp. database: 6.23E-8 mm Hg (8.31E-6 Pa); estimate: 0.2782.84E-5 mm Hg (0.00379 Pa) C18: stearic acid (CAS # 57-11-4) at 25 °C: exp. database: 7.22E-7 mm Hg (9.63E-5 Pa); estimate: 8.31E-6 mm Hg (0.00111Pa). Since the vapour pressure of a substance depends among others on the chemical structure and decreases with increasing inter- and intramolecular interactions. An ionic compound such as Stearic acid, cobalt salt shows a higher strength of attraction, because of the electrostatic interaction between its positive and negative ions. This ionic interaction leads to a higher lattice energy compared with the van-der-Waals interaction of the uncharged fatty acid and consequently to a much lower vapour pressure.

Based on the above, the vapour pressure of Stearic acid, cobalt salt is considered to be negligible based on the fact that

(i) the vapour pressure of the corresponding acid is already very low (see above) and

(ii) the vapour pressure of the corresponding ionic species is considered to be magnitudes lower since the ionic bond strength is higher compared to the Van-der-Waals interactions of the uncharged molecule. In consideration of the ionic nature of this compound, it can therefore be anticipated that the vapour pressure of Stearic acid, cobalt salt is well below the value for the organic acid, and thus negligible.

In conclusion, the conduct of further experimental verification is considered to be neither technically nor scientifically feasible, and for the reasons stated above derogation from testing is hereby applied for.