Registration Dossier
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EC number: 234-373-8 | CAS number: 11129-15-0
Water solubility
Administrative data
Link to relevant study record(s)
Description of key information
Two studies on the water solubility of calcium zirconium oxide (Eidam, 2014, 2015) are included in a weight of evidence approach. These studies investigated Ca and/or Zr leachability from calcium zirconium oxide samples containing 10% or 4% CaO w/w. Based on the results for one of the 10% CaO samples (i.e., 14.5 mg Ca/L and 0.3 mg Zr/L measured in the eluate), the water solubility of the test substance was back-calculated to be between 0.36 and 39.7 mg/L, depending on whether the measured Ca or Zr concentrations were taken as a basis for back-calculation. Either way, calcium zirconium oxide should be considered as slightly soluble (0.1-100 mg/L) in pure water.
Key value for chemical safety assessment
Additional information
Two studies from Eidam (2014, 2015), performed with the substance calcium zirconium oxide (samples containing 10% CaO and 4% CaO w/w respectively) according to an internal company testing procedure, are included in a weight of evidence approach to cover the endpoint.
The study with the 4% CaO w/w samples (Eidam, 2015) measured 2 and 6 mg Ca/L in the eluate (depending on particle size distribution of the sample), representing 0.002 and 0.006% of the total amount of test substance (10 g) added. No Zr analysis was performed in this study. The study with the 10% CaO w/w samples (Eidam, 2014) measured 13 and 14.5 mg Ca/L in the eluate (depending on particle size distribution of the sample), representing 0.013 and 0.0145% of the total amount of test substance (10 g) added. For Zr, only 0.2 and 0.3 mg Zr/L were measured in the eluate (depending on particle size distribution of the sample), representing 0.0002 and 0.0003% of the total amount of test substance (10 g) added.
Clearly, Ca leaches relatively more from the test substance compared to Zr. Taking the value of 14.5 mg Ca/L (i.e. Ca release from a 10% CaO w/w sample) as a worst case value, the water solubility of calcium zirconium oxide can be calculated as follows. The molecular weight of a 10% CaO w/w sample (mole fraction of CaO is 0.2) is theoretically 109.78 g/mol ((0.2 x 56.08 g/mol) + (0.8 x 123.2 g/mol)). Ca represents 36.5% (40.078 g/mol / 109.78 g/mol) of the test item. Therefore the value of 14.5 mg Ca/L can be recalculated to a water solubility value of 39.7 mg/L. This is a worst case value, based on the extent to which Ca is dissolved, without taking account of the Zr, which clearly leaches much less from the substance. When taking the value of 0.3 mg Zr/L (i.e. Zr release from a 10% CaO w/w sample) as a basis for calculation of the water solubility of the test substance, the water solubility of calcium zirconium oxide would be 0.36 mg/L (83.1% Zr in test item). Either way, the substance should be considered as slightly soluble (0.1-100 mg/L).
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