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Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Appearance & Aggregate state at 20°C and 101.3 kPa: solid white powder without any odour

 

Particle size distribution / Granulometry:

Nanostructured particles which are agglomerates of various shapes (irregular shaped and loosely packed) and (dispersing energy depending*) sizes as follows: MMAD / D50 >= 2.5 µm <= 302.9 µm. The typical size of the constituent particles is 15 nm and the low end aggregates size is under worst case dispersion conditions always above 150 nm.

Comparison of dry dispersion versus wet dispersion:

In contrast to the dry dispersion, the granulometric state after wet dispersion is hardly affected by the chosen intensity levels. In general, the results based on aerosol analyses imply a good dispersibility of the material.

Nanostructured particles:

Even it might be considered Sodium Aluminium Magnesium Silicate (SMAS) falls into the scope as nanomaterial according to EU recommendation (see above) it has to be pointed that this substance forms due to the wet manufacturing process (precipitation) stable and large agglomerates which are not nanoparticles but nanostructured particles. Only under standard measure conditions and depending on the disperging intensities these agglomerates are broken into smaller aggregates leading to test results like MMAD = 11.7 µm.

-> The mass median aerodynamic diameter (MMAD = D50) of the test item Silic acid Aluminium Magnesium Sodium Salt under standard conditions is: 11.7 µm.

 

 

Melting point:>400°C.

pH-value: 11.08. at 25.0 +/- 0.3 °C, aqueous solution of 10g/L

Relative density:2.08 g/cm³ at 20°C

Bulk density:164.22 kg/cm³ (at RT)

Compacted apparent density: 456.47 kg/cm³ (at RT)

Surface activity: no

Water solubility: 91.06 mg/l at 20°C (Si-content) corresponding to 211.3 mg/l based on silicic acid, aluminium magnesium sodium salt

Partition coefficient: Log Kow= - 1.50 (Water/1-Octanol)

Flammability: non flammable

Oxidising properties: no

not decomposed by light.

thermal stable in the observed temperature range 0-520 °C

no exothermic events occured, the test item is not self-reactive.

not reactive towards container material like metal, plastic or paper

Dissociation constant: pKa = 9.8

Nanomaterial, Specific surface area: Measured BET surface area: 57.9 m²/g.

Zeta potential: = -93.8 mV

Nanomaterial, Dustiness: (total) dustiness = 177.62 mg/g.

Nanomaterial, porosity: porosity of 73.2% with 0.3 µm as most frequent pore diameter and a specific pore volume of 1.267 cm³/g.

Additional information

Important for the assessment of toxicity and ecotoxicity:

Due to a MMAD > 10 µm Silicic acid,aluminium magnesium sodium salt is not respirable. Further, in the aqueous the agglomerates of this substance are dissolved continuously into smaller particles of increasing water solubility. Finally it is dissolved completely and undergoes a transformation into soluble ions such as Magnesium, Silicium, Sodium and Aluminium. Thus no nanoparticles are left! This is shown also by the studies (Affolter 2013) about water solubility: No light scattering (Tyndall effect) was seen in the aqueous solutions indicating that no colloidal dispersed particles are present.