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EC number: 231-130-8
CAS number: 7440-21-3
Silicon is a grey, metallically lustrous, metalloid element with atomic
number 14 and atomic weight 28.086. Silicon is not naturally present in
its reduced elemental form as it undergoes spontaneous oxidation in air.
Therefore elemental Silicon is not found free in nature, but occurs as
oxide and as silicates. Silicon crystallises in the cubic diamond
structure. There is also an amorphous allotropic modification of Silicon
described in the literature. However, due to lack of data, this
allothrophic form of Silicon is not dealt with or covered by this
dossier, Crystalline Silicon is the element (substance) being covered by
this dossier. Silicon is commercially available in the form of lumps,
ingots, wafers, briquettes, flakes, granules and powders of different
size ranges. The purity of commercial silicon ranges from 95 to 100 wt%.
The main impurities include iron, calcium and aluminium. A thin layer of
amorphous silicon oxide is formed on the surface of silicon exposed to
air, even at ambient temperatures. The outermost surface is composed of
amorphous silicon dioxide, and the interface of silicon sub-oxides with
varying oxidation stages. Similar surface characteristics were detected
in the surface analysis of silicon particles and particles of amorphous
silicon dioxide. The solubility of silicon in water is very low and
strongly dependent on the pH of the solution. In addition to silicon,
trace amounts of metal ions present as impurities may be dissolved from
silicon. Dissolution of silicon in the form of monosilicic acid from
silicon particles in synthetic biological fluids is slighly lower than
from pyrogenic amorphous silica Aerosil Ox50. This can be at least
partly explained by different particle characteristics (e.g. lower
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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