Aluminum, benzoate C16-18-fatty acids complexes

Endpoint summary

Additional information

Appearance/physical state/colour

Aluminum, benzoate C16-18-fatty acids complexes, is a pale yellow solid at ambient temperature. The data are taken from substance identification information in a GLP-compliant, guideline study available as an unpublished report (Harlan 2013).

Melting point/freezing point

Aluminum, benzoate C16-18-fatty acids complexes decomposed without melting from approximately 224 °C (497 K). The melting point was determined in a GLP-compliant thermal analysis test, using differential scanning calorimetry following OECD guideline 102 (Harlan 2013).

Boiling point

No experimental determination of the boiling temperature was possible for aluminum, benzoate C16-18-fatty acids complexes as detailed in Method A2 Boiling Temperature of Commission Regulation (EC) No 440/2008 of 30 May 2008, and Method 103 of the OECD Guidelines for Testing of Chemicals, 27 July 1995, because the test item had been demonstrated to decompose prior to melting.

Density

The density of aluminum, benzoate C16-18-fatty acids complexes has been determined to be 1080 kg/m3 at 20.0 ± 1.0 °C (relative density value 1.08). The density of the test item was determined in a GLP-compliant air comparison pycnometer (for solids) test following OECD guideline 109 (Harlan 2013).

Granulometry

The particle size distribution test has been waived because the substance is not manufactured or used in an isolated or granular form.

Vapour pressure

The vapour pressure of aluminum, benzoate C16-18-fatty acids complexes has been determined to be 0.000044 Pa at 25

°C. The vapour pressure of the test item was determined in a GLP-compliant study (Harlan 2013) following OECD guideline 104.

Water solubility

The water solubility of aluminum, benzoate C16-18-fatty acids complexes has been determined to be less than or equal to 0.00026 g/L at 20.0 ± 0.5 °C. The water solubility of the test item was determined in a GLP-compliant study (Harlan 2013) following OECD guideline 105.

Partition Coefficient

No determination of the partition coefficient was possible by the shake-flask method as detailed in Method A8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 107 of the OECD Guidelines for Testing of Chemicals, 27 July 1995. This was due to the insolubility of aluminum, benzoate C16-18-fatty acids complexes in both n-octanol and water. Further to this, determination of the partition coefficient by the HPLC estimation method as detailed in Method A8 Partition Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 117 of the OECD Guidelines for Testing of Chemicals, 13 April 2004, was also not possible. This was due to the insolubility of aluminum, benzoate C16-18-fatty acids complexes in suitable reverse phase HPLC solvents.

The partition coefficient was estimated by QSAR but the result is considered not to be relevant to the substance itself. As aluminum, benzoate C16-18-fatty acids complexes is an ionisable salt, the partition coefficient can vary greatly depending on pH and the pKa of the substance. In order to compare partition coefficient values of different, ionisable compounds on a relative basis, partition coefficient values are sometimes reported as "corrected for ionisation", indicating that the value represents the partition coefficient at a pH where a compound exists primarily in the non-ionized form. However, KOWWIN (KOWWIN v1.67 in EPISuite v4.00, US EPA 2009) considers aluminum, benzoate C16-18-fatty acids complexes to be “ion pairs” and as such only provides estimates for the ionised fatty acids and benzoic acid rather than the salt. The partition coefficient value for the salt itself therefore could not be determined.

Aluminum, benzoate C16-18-fatty acids complexes is typically not synthesized as the “pure” compound and seldom exists except in the presence of the oil matrix. High temperature stability indicates that the grease thickener structure is robust and resistant to diffusion out of the oil. Dissolution of the grease thickener from grease into water is very unlikely as the thickener is poorly water soluble and the thickener is embedded in the hydrophobic grease matrix and thus less likely to leach out. Thus the partition coefficient of the substance is not expected to be relevant.

Surface tension

The surface tension of duplicate 90% saturated aqueous solutions of aluminum, benzoate C16-18-fatty acids complexes has been determined to be 72.6 mN/m at 20.0 ± 0.5 °C. Since the substance showed a surface tension greater than 60 mN/m, it was considered not to be surface active. The surface tension of the test material was determined in a GLP-compliant ring balance test following OECD guideline 115 (Harlan 2013).

Auto-flammability

Aluminum, benzoate C16-18-fatty acids complexes was determined not to have a relative self-ignition temperature below its melting point. The relative self-ignition temperature of the test item was determined in a GLP-compliant study following EC 440/2008 A16 method (Harlan 2013).

Flammability

Aluminum, benzoate C16-18-fatty acids complexes was determined to be not highly flammable as it failed to propagate combustion along 200 mm within 4 minutes.The flammability of the test item was determined in a GLP-compliant test following the method EC440/2008 A10 (Harlan 2013).

Experience in manufacture and handling shows that aluminum, benzoate C16-18-fatty acids complexes does not ignite spontaneously on coming into contact with air at normal temperatures and is stable at room temperature for prolonged periods of time (days). Experience has also shown that the substance does not react with water. It therefore does not meet the criteria for classification as a pyrophoric substance or a substance which in contact with water emits flammable gases.

Dissociation constant

No data are available on the dissociation constants, for aluminum, benzoate C16-18-fatty acids complexes so the dissociation constants have been read across from sodium palmitate (Kanicky et al 2000), potassium stearate (Kanicky and Shah 2002) and benzoic acid (Lide 2008).

Kanicky et al. (2000) titrated sodium palmitate with sodium hydroxide and calculated the mean pKa from the pH at half the neutralisation volume for each of the five replicates. Kanicky and Shah (2002) titrated potassium stearate with hydrochloric acid and calculated the mean pKa from the pH at half the neutralisation volume for each of the five replicates. The studies are non-GLP, non-guideline experiments, available in peer-reviewed published journal articles. The experiments follow sound scientific principles and are considered adequate for assessment. The dissociation constant of benzoic acid was taken from a reliable peer reviewed handbook (Lide 2008) and so can be considered reliable and suitable for use as the key study for this endpoint.

At neutral pH, and within the limits of solubility, aluminum, benzoate C16-18-fatty acids complexes is expected to dissociate into aluminium species, mainly aluminium hydroxide, fatty acid anions and benzoate anions. The fatty acid and benzoate anions would then be expected to achieve equilibrium with respect to the H⁺ ions in the water (depending on the pKa of the fatty acid and benzoic acid) and at neutral pH there would be ionised acids, unionised acids, and aluminium hydroxide species. As the dissociation constant of aluminum, benzoate C16-18-fatty acids complexes is expected to be determined by the equilibrium of the fatty acids and benzoic acid with respect to the hydrogen ions in the water, read across between the same fatty acids and benzoic acid is considered to be justified.

The measured dissociation constant for sodium palmitate of 8.8 (Kanicky et al. 2000) and for potassium stearate of 10.15 (Kanicky and Shah 2002) are both relatively high and thus any dissociated fatty acid would be expected to be unionised (protonated) at environmental pH.The measured dissociated constant for benzoic acid is reported to be 4.204 (Lide 2008) which implies that at neutral pH the benzoic acid would be completely deprotonated and exist entirely as the free benzoate anion or as a complex with aluminium.

 

Other physico-chemical endpoints

As aluminum, benzoate C16-18-fatty acids complexes is a solid, the viscosity and flash point endpoints are not required. Based on the structure of the substance, the explosiveness and oxidising properties studies have not been conducted as there are no structural alerts that would indicate explosive or oxidising properties. The stability in organic solvents and identity of relevant degradation products study has not been conducted as it is not considered to be a critical endpoint. As the substance is manufactured and used in situ in a base oil and not marketed or used in isolated forms the particle size distribution test has been waived.

Classification and labelling

The substance is not classified for physico-chemical hazards. Based on the structure of the substance, it does not meet the criteria for oxidising or explosive properties and based on experimental data, the substance does not meet the criteria for flammable solids. Experience in manufacture and handling shows that the substance is not a self-heating solid.