Registration Dossier
Registration Dossier
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EC number: 215-684-8 | CAS number: 1344-00-9
Endpoint summary
Administrative data
Description of key information
Silicic acid, aluminum sodium salt (CAS 1344-00-9, NAS) is an odourless, white, solid powder with physico-chemical properties as follows:
Its melting point is greater than 550 °C.
The relative density ranges between 2.007 and 2.068 g/cm³ at 20 °C -> mean value: 2.05 g/cm³
The typical median particle size for Silicic acid, aluminum sodium salt (CAS 1344-00-9, NAS) ranged from 5.1 to 8.8 μm (aggregates/agglomerates, measured by laser diffraction in the liquid phase).
The water solubility (acc. to OECD 105) varies depending on the specific nanoform tested:
SiO2 concentration: 61.86 - 239.7 mg/l
Na+ concentration: 26.93 - 228.6 mg/l
Al2O3 concentration: < 0.019 - 0.0611 mg/l
Altogether the OECD 105 measurements show a low water solubility of this substance resp its forms for a nominal t=0 load of 50g/L, this is supported also by measurement according to OECD 29.
Measurement according to OECD 29 to determine the maximum concentration of total dissolved Si and Al (here compounds of the substance which undergo either dissolution or rapid transformation) results in the following concentrations of Si and Al on day 28 with 1 mg/L nominal load: 64.7 µg/L Si and 3.48 µg/L Al.
The pH differs by form from 5.5-7.5 to 9.6-10.6
The measured BET values ranged between 25 and 395 m²/g.
The zeta potential ranged from -34.1 to 17.0 mV in different pH ranges. The point of zero charge (pzc) varied between pH 1.9 and pH 3.0
In two studies the dustiness of two nanoforms of Silicic acid, aluminum sodium salt (CAS 1344-00-9, NAS) was determined by laser diffraction analysis according to the weak dry dispersion method GRADIS/L, following values were assessed:
With the high-BET nanoform the inhalable, thoracic and alveolar mean values until a 100 μm cut-off were 25390, 91 and 0 mg/kg, respectively. Those until a 37 μm cut-off were 3713, 87 and 0 mg/kg, respectively.
With the medium-BET nanoform the inhalable, thoracic and alveolar mean values until a 100 μm cut-off were 21531, 4 and 0 mg/kg, respectively.
In a study with the medium-BET nanoform the dustiness was determined by the modified Heubach procedure (DIN 55992-1:2006), following values were assessed:
Total dustiness, whole fraction: 62.4836 mg/g
Dustiness, inhalable fraction: 37.9720 mg/g (60.77 % of whole fraction, 3.80 % of used quantity)
Dustiness, thoracic fraction: 4.7853 mg/g (7.66 % of whole fraction, 0.48 % of used quantity)
Dustiness, alveolar fraction: 0.4757 mg/g (0.76 % of whole fraction, 0.05 % of used quantity)
A porosity of 78.8%, with 404 nm as the most frequent pore diameter, and a specific pore volume of 1.809 cm³/g was determined.
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