Usp Talco

© 2010 USPC Official 12/1/09 - 9/30/10 USP Monographs: Talc

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Talc

» Talc is a powdered, selected, natural, hydrated magnesium silicate. Pure talc has the formula Mg3Si4O10(OH)2. It may contain variable amounts of associated minerals among which chlorites (hydrated aluminum and magnesium silicates), magnesite (magnesium carbonate), calcite (calcium carbonate), and dolomite(calcium and magnesium carbonate) are predominant.
Packaging and storage— Preserve in well-closed containers. No storage requirements specified. Labeling— The label states, where applicable, that the substance is suitable for oral or topical administration. The certificate of analysis states the absence of asbestos. It also indicates which method specified under the test for Absence of asbestos wasused for analysis. Identification— A: The IR spectrum of a potassium bromide dispersion of it exhibits maxima at 3677 ± 2 cm 1 –1 –1 , at 1018 ± 2 cm , and at 669 ± 2 cm .
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B: Mix about 200 mg of anhydrous sodium carbonate with 2 g of anhydrous potassium carbonate, and melt in a platinum crucible. To the melt add 100 mg of the substance under test, and continue heating until fusion iscomplete. Cool, and transfer the fused mixture to a dish or beaker with the aid of about 50 mL of hot water. Add hydrochloric acid to the liquid until effervescence ceases, then add 10 mL more of the acid, and evaporate the mixture on a steam bath to dryness. Cool, add 20 mL of water, boil, and filter the mixture: [NOTE—Save the insoluble residue for use in Identification test C.] To 5 mL of thefiltrate add 1 mL of 6 N ammonium hydroxide and 1 mL of ammonium chloride TS. Filter, if necessary, and add 1 mL of dibasic sodium phosphate TS to the filtrate: a white crystalline precipitate of magnesium ammonium phosphate is formed. C: In a lead or platinum crucible and using a copper wire, mix about 100 mg of the insoluble residue as obtained in Identification test B with about 10 mg of sodiumfluoride and a few drops of sulfuric acid to give a thin slurry. Cover the crucible with a thin transparent plate of plastic under which a drop of water is suspended, and warm gently. Within a short time, a white ring is rapidly formed around the drop of water. Microbial enumeration tests 61 and Tests for specified microorganisms 62 — If intended for topical administration, the total aerobic microbialcount does not exceed 100 cfu per g, and the total combined molds and yeasts count does not exceed 50 cfu per g. If intended for oral administration, the total aerobic microbial count does not exceed 1000 cfu

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8/25/2010

© 2010 USPC Official 12/1/09 - 9/30/10 USP Monographs: Talc

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per g, and thetotal combined molds and yeasts count does not exceed 100 cfu per g. Acidity and alkalinity— Boil 2.5 g of Talc with 50 mL of carbon dioxide-free water under reflux. Filter under vacuum. To 10 mL of the filtrate, add 0.1 mL of bromothymol blue TS. Not more than 0.4 mL of 0.01 N hydrochloric acid is required to change the color of the indicator. To 10 mL of the filtrate, add 0.1 mL ofphenolphthalein TS: not more than 0.3 mL of 0.01 N sodium hydroxide is required to change the color of the indicator to pink. Loss on ignition 733 — Weigh accurately about 1 g, and ignite at 1075 ± 25 to constant weight: it loses not more than 7.0% of its weight. Water-soluble substances— To 10.0 g add 50 mL of carbon dioxide-free water, heat to boiling, and boil under a reflux condenser for 30 minutes. Allowto cool, filter, and dilute with carbon dioxide-free water to 50.0 mL: the filtrate is neutral to litmus paper. Evaporate 25.0 mL of the filtrate to dryness, and dry at 105 for 1 hour: the weight of the residue does not exceed 5 mg (0.1%). Limit of iron— Test stock solution— Weigh 10.0 g of Talc into a conical flask fitted with a reflux condenser, gradually add 50 mL of 0.5 N hydrochloric acid...