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Physical & Chemical properties

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Appearance/physical state/colour: Calcium oxide is a beige (grey white) powder at room temperature (reliable data from a GLP guideline compliant study report). Based on available data, calcium carbonate is a white powder or colourless crystals, and it may be expected that grades of calcium oxide with up to 35% calcium carbonate will be of similar appearance to that described in the key study.

Melting point: > 450 °C (study result, EU A.1 method). Literature data for calcium carbonate also show the melting point to be greater than 450 °C and grades of calcium oxide with up to 35% calcium carbonate are not expected to be significantly different to that given by the key study.

Boiling point: According to Annex VII, section 7.3, column 2 of Regulation No. 1907/2006, a boiling point study is not required for solids that either melt above 300 °C or decompose before boiling. The melting point of calcium oxide is >450 °C and the melting point of grades of calcium oxide containing calcium carbonate up to 35% is also expected to be >450 °C . Hence a boiling point study is not required.

Relative density (compared to water at 4 °C) is D4R = 3.31 (22 °C) (study result, EU A.3 method). The deviation from the nominal temperature (20 °C) does not significantly affect the accuracy of the density value. The relative density of calcium carbonate, based on a weight of evidence using data from several peer reviewed handbooks, is 2.7. Thus it may be expected that grades of calcium oxide with up to 35% calcium carbonate will have a relative density similar to the key value.

Particle size distribution (Granulometry): Calcium oxide 0 - 2 mm: Total Dustiness (airborne fraction): 100.01 mg/g (experimental results, DMT Report). MMAD of airborne fraction: MMAD = 17.14 µm (distribution fitted to cascade impactor data). GSD of MMAD: GSD = 2.75 µm. Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD): Head (ET): 59.2 %; Tracheobronchial (TB): 0.8 %; Pulmonary (PU): 1.1 %. Calcium oxide > 10 mm: Total Dustiness (airborne fraction): 2.10 mg/g (experimental results, DMT Report). MMAD of airborne fraction: MMAD = 18.26 µm (distribution fitted to cascade impactor data). GSD of MMAD: GSD = 2.97 µm. Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD): Head (ET): 55.7 %; Tracheobronchial (TB): 0.8 %; Pulmonary (PU): 1.1 %

Vapour pressure: This study does not need to be conducted for solids with a melting point above 300°C (melting point of this substance: > 450 °C) (cf. section 7.5 Column 2 Annex VII of regulation (EC) 1907/2006).

Partition coefficient: This study generally does not need to be conducted for inorganic substances (cf. section 7.8 Column 2 Annex VII of regulation (EC) 1907/2006).

Water solubility of calcium oxide: 1337.6 mg/l at 20 ± 0.5 °C (study results, EU A.6 method, recalculated value from calcium). The water solubility of calcium carbonate, as determined in a study performed according to OECD TG 105, is 16.6 mg/L at 20 °C.

Surface tension: This study only needs to be conducted if based on the structure surface activity is expected or can be predicted, which is not the case for this substance: Calcium oxide is not known to exhibit such a structure (hydrophilic head group and hydrophobic tail) (cf. section 7.6 Column 2 Annex VII of Regulation (EC) 1907/2006).

 

Flash point: This study is only relevant for liquids or low melting point solids, which is not the case for this substance. Further, this study generally does not need to be conducted for inorganic substances (cf. section 7.9 Column 2 Annex VII of Regulation (EC) 1907/2006).

Auto-flammability: The test material showed no relative self-ignition temperature below 400 °C (study result, EU A.16 method). Calcium carbonate was also found to be not auto flammable in a study performed using Method N.4 of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, 4th revised edition, 2003. On this basis it may be concluded that grades of calcium oxide containing up to 35% calcium carbonate will not be auto flammable.

Flammability: Non-flammable (study result, EU A.10 method). Similarly, calcium carbonate is not flammable based on the results of a preliminary screening test performed according to Method N.1 of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, 4th revised edition, 2003. Therefore it may be concluded that grades of calcium oxide containing up to 35% calcium carbonate will also be not flammable.

Explosiveness: According to the provisions of EU A.14 method, expert judgement considered the test substance to be void of any chemical structures commonly associated with explosive properties. The structure of calcium carbonate was also assessed for chemical groups that would indicate explosive properties and was found to contain no such groups.

Oxidising properties: According to the provisions of EU A.17 method, expert judgement considered the test substance as a not oxidising substance. The structure of calcium carbonate was assessed for chemical groups that would indicate oxidising properties and was found to contain no such groups.

Stability in organic solvents and identity of relevant degradation products: This study does not need to be conducted for inorganic substances (cf. section 7.15 Column 2 Annex IX of Regulation (EC) 1907/2006).

Dissociation constant: In accordance with section 1, Annex XI of Regulation (EC) 1907/2006 (REACH), the study does not need to be conducted. This property is applicable only for ionisable organic substances. Calcium oxide is an inorganic salt, which reacts with water to give a solution of calcium dihydroxide. Calcium dihydroxide on the other hand will be completely dissociated into Ca2+ and OH- ions when dissolved in water. The concept of dissociable functional groups is therefore not applicable. Therefore, the determination of a dissociation constant is not considered to be required (ECHA Guidance on information requirements and chemical safety assessment Chapter R.7a: Endpoint specific guidance, section R.7.1.17).

Viscosity: Viscosity is a property of fluids. Since calcium oxide is a solid at ambient temperature (ca. 20°C) such a study does not need to be conducted for this substance (melting point: >450°C) (in accordance with section 1, Annex XI of regulation (EC) 1907/2006 (REACH)) .