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Colloidal Silicon Dioxide SiO2 60.08 Silica. Silica [7631-86-9]. » Colloidal Silicon Dioxide is a submicroscopic fumed silica prepared by the vapor-phase hydrolysis of a silicon compound. When ignited at 1000° for 2 hours, it contains not less than 99.0 percent and not more than 100.5 percent of SiO2. Packaging and storage— Preserve in well-closed containers. Identification— A: Transfer about 5 mg to a platinum crucible, and mix with about 200 mg of anhydrous potassium carbonate. Ignite at a red heat over a burner for about 10 minutes, and cool. Dissolve the melt in 2 mL of freshly distilled water, warming if necessary, and slowly add 2 mL of ammonium molybdate TS to the solution: a deep yellow color is produced. B: [ Caution — Avoid contact with o-tolidine when performing this test, and conduct the test in a well- ventilated hood. ] Place 1 drop of the yellow silicomolybdate solution obtained in Identification test A on a filter paper, and evaporate the solvent. Add 1 drop of a saturated solution of o-tolidine in glacial acetic acid to reduce the silicomolybdate to molybdenum blue, and place the paper over ammonium hydroxide: a greenish blue spot is produced. pH á 791 ñ : between 3.5 and 5.5, in a 1 in 25 dispersion. Loss on drying á 731 ñ — Dry it in a tared platinum crucible at 105° for 2 hours: it loses not more than 2.5% of its weight. Retain the dried specimen, in the crucible, for the test for Loss on ignition. Loss on ignition á 733 ñ — Ignite the portion of Colloidal Silicon Dioxide, retained from the test for Loss on drying, at 1000 ± 25° to constant weight: the previously dried Colloidal Silicon Dioxide loses not more than 2.0% of its weight. Arsenic, Method I á 211 ñ— Prepare the Test Preparation as follows. Transfer 2.5 g to a flask, add 50 mL of 3 N hydrochloric acid, and reflux for 30 minutes using a water condenser. Cool, filter with the aid of suction, and transfer the filtrate to a 100-mL volumetric flask. Wash the filter and flask with several portions of hot water, and add the washings to the flask. Cool, dilute with water to volume, and mix: a 15.0-mL portion of this solution, to which 3 mL of hydrochloric acid has been added, meets the requirements of the test, the addition of the 7 N sulfuric acid being omitted. The limit is 8 µg per g. Organic volatile impurities, Method IV á 467 ñ : meets the requirements. Assay— Transfer about 500 mg of Colloidal Silicon Dioxide to a tared platinum crucible, ignite at 1000 ± 25° for 2 hours, cool in a desiccator, and weigh. Add 3 drops of sulfuric acid, and add enough alcohol to just moisten the sample completely. Add 15 mL of hydrofluoric acid, and in a well-ventilated hood evaporate on a hot plate to dryness, using medium heat (95° to 105°) and taking care that the sample does not spatter as dryness is approached. Heat the crucible to a red color with the aid of a Bunsen burner. Ignite the residue at 1000 ± 25° for 30 minutes, cool in a desiccator, and weigh. If a residue remains, repeat the procedure, beginning with “add 15 mL of hydrofluoric acid. ” The weight lost by the assay specimen, previously ignited at 1000 ± 25°, represents the weight of SiO 2 in the portion taken. Auxiliary Information— Staff Liaison : Catherine Sheehan, Senior Scientific Associate Expert Committee : (EMC) Excipients: Monograph Content USP27–NF22 Page 2928 Phone Number : 1-301-816-8262 [ Last edited by 小小强 on 2006-8-28 at 21:54 ] |
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