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Physical & Chemical properties

Water solubility

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Description of key information

Water solubility [tripotassium propylsilanetriolate in aqueous solution]: miscible at ambient temperature
Water solubility (Propylsilanetriol and its dimer and trimer): very soluble at 20°C (QSAR)

Key value for chemical safety assessment

Additional information

In accordance with section 1 of REACH Annex XI, the study does not need to be conducted because the composition of the substance (30 - 35% w/w solution of tripotassium propylsilanetriolate in water) indicates that tripotassium propylsilanetriolate is completely miscible with water. It should be noted that the substance is only stable under conditions of high pH; as the pH is lowered polymerisation occurs resulting in precipitation from the solution.

The water solubility of propylsilanetriol, and its dimer and trimer were predicted using a validated QSAR estimation.

In a review of the safety of organic silicon, monomethylsilanetriol (EFSA 2016); the maximum solubility at which condensation of methylsilanetriol can occur was reported as 21 mM (approximately 2000 mg/L based on molecular weight of 94.14 g/mol) at 21°C. This value is read-across to propylsilanetriol. Propylsilanetriol and methylsilanetriol are both alkylsilanetriols with a short-chain alkyl group and three -OH groups at a silicon centre. The difference is that the alkyl group is propyl for propylsilanetriol and methyl for methylsilanetriol. As both substances are silanetriols, the mechanisms of condensation should be equivalent. The molar concentration is read-across, leading to a concentration of 2600 mg/l propylsilanetriol based on a molecular weight of 122 g/mol.

Reference:

EFSA (2016). Safety of organic silicon (monomethylsilanetriol, mmst) as a novel food ingredient for use as a source of silicon in food supplements and bioavailability of orthosilicic acid from the source. EFSA Journal 2016;14(4):4436