Talc

• BPPurified Talc
• JPTalc
• Ph. Eur.Talc
• USP–NFTalc

Altalc; French chalk; hydrous magnesium silicate; Luzenac Pharma; magnesium hydrogen metasilicate; powdered talc; purified French chalk; steatite; talcum; E553b

Hydrated magnesium silicate · [14807-96-6]

UNII 7SEV7J4R1U · PubChem CID 165411828

Mg3Si4O10(OH)2 · 379.27

Glidant, Lubricant

Typical concentrations: 1–10% · Dosage forms: Solid

Used in oral solid dosage forms as a glidant and lubricant (about 1–10% w/w) and as a diluent (about 5–30% w/w), and as an anti-tacking agent in film and sugar coating. It is also used as a dusting powder (90–99%), in cosmetics and in foods.

A very fine, white to greyish-white, odourless, impalpable crystalline powder that is unctuous, adheres readily to the skin and is free from grittiness. It is a natural mineral, mainly hydrated magnesium silicate, that may contain small amounts of aluminium silicate and iron; pharmacopoeial talc must be free from asbestos.

Particle size

varies with grade; pharmaceutical grades are fine, micronised or milled powders, and particle size affects lubricant and glidant efficiency

Specific gravity

about 2.7–2.8

pH

about 7–10 (20% w/v aqueous dispersion)

Hardness

1 on the Mohs scale (the softest mineral); lamellar and greasy to the touch

Solubility

practically insoluble in water, dilute acids and alkalis, and organic solvents

Stable. It can be sterilised by dry heat (for example 160 °C for at least 1 hour), by ethylene oxide or by gamma irradiation. Store in a well-closed container in a cool, dry place.

Incompatible with quaternary ammonium compounds, which it can adsorb.

Mined from natural deposits, then crushed, milled and purified, for example by froth flotation, acid washing and drying, before being classified by particle size. Sources and processing are chosen and tested to exclude asbestos.

Not absorbed after oral use and regarded as essentially non-toxic by that route. Chronic inhalation causes talcosis and granulomatous lung disease, and intravenous misuse of crushed tablets has caused pulmonary granulomas. It should not be used on wounds, body cavities or surgical gloves, where it may cause granulomas; its long-term perineal use has been a subject of safety concern.

Observe normal precautions for the quantity handled. Talc is an occupational inhalation hazard; avoid generating dust and use a suitable respirator and eye protection, with local exhaust ventilation where needed.

Accepted as a food additive in Europe (E553b). Included in the FDA Inactive Ingredient Database (buccal tablets; oral capsules and tablets; rectal and topical preparations) and in non-parenteral medicines licensed in Europe.

Bentonite; kaolin; magnesium aluminium silicate; magnesium silicate; magnesium trisilicate.

Talc is hydrophobic and, at higher levels, can slow tablet disintegration and dissolution. Its lubricant efficiency is lower than that of magnesium stearate, so it is often combined with it. Pharmacopoeias now require specific tests for amphibole and serpentine asbestos.