Talc

Prepared at the 49th JECFA (1997)
superseding specifications prepared at the 39th JECFA (1992),
published in FNP 52 Addendum 1 (1992)

SYNONYMS

Talcum; INS No.553(iii)

DEFINITION

Naturally occuring form of hydrous magnesium silicate containing varying proportions of such associated minerals as alpha-quartz, calcite, chlorite, dolomite, kaolin, magnesite, and phlogopite. Talc derived from deposits that are known to contain associated asbestos is not food grade.

C.A.S. number

14807-96-6

DESCRIPTION

Odourless, very fine, white or grayish white, crystalline powder. It is unctuous, adheres readily to the skin, and is free from grittiness.

FUNCTIONAL USES

Anticaking agent, filtering aid, coating agent, lubricating and release agent, surface-finishing agent, texturizing agent, filter aid, dusting powder.

CHARACTERISTICS

IDENTIFICATION

Solubility

Insoluble in water and ethanol

Positive test for magnesium

Passes test
See description under TESTS

Infrared adsorption

The infrared absorption spectrum of a potassium bromide dispersion of the sample exhibits major peaks at approximately 1015 cm^-1 and 450 cm^-1.

X-ray diffraction

The X-ray diffraction pattern of a random powder sample exhibits reflections at the following d values of 9.34 Å, 4.66 Å and 3.12 Å.

PURITY

Loss on ignition

Not more than 9%
See description under TESTS

Loss on drying

Not more than 0.5%

Water-soluble substances

Not more than 0.2%
See description under TESTS

Acid-soluble iron

Passes test
Slightly acidify with hydrochloric acid the remaining half of the filtrate obtained in the test for water-soluble substances (above) and add 1 ml of potassium ferrocyanide TS. The solution does not turn blue.

Acid-soluble substances

Not more than 1%
See description under TESTS

Arsenic

Not more than 3 mg/kg
See description under TESTS

Lead

Not more than 10 mg/kg
See description under TESTS

TESTS

IDENTIFICATION TESTS

Positive test for magnesium

Mix 0.5 g sample with 0.2 g of anhydrous sodium carbonate and 2 g of anhydrous potassium carbonate, and heat the mixture in a platinum crucible until fusion is complete. 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, an insoluble residue of gel remains. Dissolve in the filtrate about 2 g of ammonium chloride, and add 5 ml of ammonia TS. Filter if necessary, and add sodium phosphate TS to the filtrate. A white crystalline precipitate separates.

PURITY TESTS

Loss on ignition

Transfer a 1 g sample, accurately weighed, to a tared platinum crucible. Cover, apply heat gradually, and ignite for at least 3 h to a constant weight.

Water-soluble substances

Boil a 10 g sample with 50 ml of water and from time to time, add water to maintain approximately the original volume, and filter. The filtrate is neutral to litmus paper. Evaporate one-half of filtrate to dryness, and dry further at 105° for 1h. The weight of the residue does not exceed 10 mg.

Acid-soluble substances

Digest a 1 g sample with 20 ml of dilute hydrochloric acid at 50° for 15 min, add water to restore the original volume, mix and filter. To 10 ml of the filtrate add 1 ml of dilute sulfuric acid TS, evaporate to dryness, and ignite to constant weight. The weight of the residue does not exceed 10 mg.

Arsenic

To a 1 g sample, accurately weighed, add 5 ml of dilute hydrochloric acid TS and boil while stirring; cool, and filter. Wash the residue with 5 ml of dilute hydrochloric acid TS and subsequently with 25 ml of water. Combine the washings with the filtrate. This solution meets the requirement of the Arsenic Limit Test (Method II).

Lead

10 ml of solution prepared for the determination of arsenic meets the requirements of the Limit Test using 10 m g of lead ion (Pb) in the control.

SYNONYMS	Talcum; INS No.553(iii)
DEFINITION	Naturally occuring form of hydrous magnesium silicate containing varying proportions of such associated minerals as alpha-quartz, calcite, chlorite, dolomite, kaolin, magnesite, and phlogopite. Talc derived from deposits that are known to contain associated asbestos is not food grade.
C.A.S. number	14807-96-6
DESCRIPTION	Odourless, very fine, white or grayish white, crystalline powder. It is unctuous, adheres readily to the skin, and is free from grittiness.
FUNCTIONAL USES	Anticaking agent, filtering aid, coating agent, lubricating and release agent, surface-finishing agent, texturizing agent, filter aid, dusting powder.
CHARACTERISTICS
IDENTIFICATION
Solubility	Insoluble in water and ethanol
Positive test for magnesium
	Passes test See description under TESTS
Infrared adsorption	The infrared absorption spectrum of a potassium bromide dispersion of the sample exhibits major peaks at approximately 1015 cm^-1 and 450 cm^-1.
X-ray diffraction	The X-ray diffraction pattern of a random powder sample exhibits reflections at the following d values of 9.34 Å, 4.66 Å and 3.12 Å.
PURITY
Loss on ignition	Not more than 9% See description under TESTS
Loss on drying	Not more than 0.5%
Water-soluble substances
	Not more than 0.2% See description under TESTS
Acid-soluble iron	Passes test Slightly acidify with hydrochloric acid the remaining half of the filtrate obtained in the test for water-soluble substances (above) and add 1 ml of potassium ferrocyanide TS. The solution does not turn blue.
Acid-soluble substances	Not more than 1% See description under TESTS
Arsenic	Not more than 3 mg/kg See description under TESTS
Lead	Not more than 10 mg/kg See description under TESTS
TESTS
IDENTIFICATION TESTS
Positive test for magnesium
	Mix 0.5 g sample with 0.2 g of anhydrous sodium carbonate and 2 g of anhydrous potassium carbonate, and heat the mixture in a platinum crucible until fusion is complete. 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, an insoluble residue of gel remains. Dissolve in the filtrate about 2 g of ammonium chloride, and add 5 ml of ammonia TS. Filter if necessary, and add sodium phosphate TS to the filtrate. A white crystalline precipitate separates.
PURITY TESTS
Loss on ignition	Transfer a 1 g sample, accurately weighed, to a tared platinum crucible. Cover, apply heat gradually, and ignite for at least 3 h to a constant weight.
Water-soluble substances
	Boil a 10 g sample with 50 ml of water and from time to time, add water to maintain approximately the original volume, and filter. The filtrate is neutral to litmus paper. Evaporate one-half of filtrate to dryness, and dry further at 105° for 1h. The weight of the residue does not exceed 10 mg.
Acid-soluble substances	Digest a 1 g sample with 20 ml of dilute hydrochloric acid at 50° for 15 min, add water to restore the original volume, mix and filter. To 10 ml of the filtrate add 1 ml of dilute sulfuric acid TS, evaporate to dryness, and ignite to constant weight. The weight of the residue does not exceed 10 mg.
Arsenic	To a 1 g sample, accurately weighed, add 5 ml of dilute hydrochloric acid TS and boil while stirring; cool, and filter. Wash the residue with 5 ml of dilute hydrochloric acid TS and subsequently with 25 ml of water. Combine the washings with the filtrate. This solution meets the requirement of the Arsenic Limit Test (Method II).
Lead	10 ml of solution prepared for the determination of arsenic meets the requirements of the Limit Test using 10 m g of lead ion (Pb) in the control.