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SODIUM BENZOATE

Prepared at the 17th JECFA (1973), published in FNP 4 (1978) and in FNP 52 (1992)


SYNONYMS

INS No. 211

DEFINITION

Chemical names

Sodium benzoate, sodium salt of benzenecarboxylic acid, sodium salt of phenylcarboxylic acid

C.A.S. number

532-32-1

Chemical formula

C7H5NaO2

Structural formula

Formula weight

144.11

Assay

After drying at 105o for 4 h, contains not less than 99% of C7H5NaO2.

DESCRIPTION

White, almost odourless, crystalline powder or granules

FUNCTIONAL USES

Preservative

CHARACTERISTICS

IDENTIFICATION

Solubility

Freely soluble in water, sparingly soluble in ethanol

Melting range for benzoic acid

121.5 o - 123.5o

Acidify a 2% solution of the sample with dilute hydrochloric acid TS. Collect the precipitated benzoic acid on a filter paper, wash free of chloride with water and dry at 105° for 4 h. and then determine the melting range.

Test for benzoate

To a 10% solution of the sample add ferric chloride TS. A buff coloured precipitate is produced.

Test for sodium

Acidify a solution of the sample with dilute acetic acid TS. Filter if necessary, and add uranyl zinc acetate TS. A yellow crystalline precipitate is formed.

PURITY

Loss on drying

Not more than 1.5% (105o, 4 h)

Acidity or alkalinity

Dissolve 2 g of the sample, weighed to the nearest mg, in 20 ml of freshly boiled water. Not more than 0.5 ml of either 0.1N sodium hydroxide or 0.1N hydrochloric acid should be required for neutralization, using phenolphthalein TS as indicator.

Readily carbonizable substances

Dissolve 0.5 g of the sample, weighed to the nearest mg, in 5 ml of sulfuric acid TS. The colour produced should not be darker than a light pink ("Matching Fluid Q")

Chlorinated organic compounds

Not more than 0.07% (as chlorine)

Test 0.25 g of the sample using 0.5 ml of 0.01N hydrochloric acid in the control

Readily oxidizable substances

Add 1.5 ml of sulfuric acid to 100 ml of water, heat to boiling and add 0.1N potassium permanganate, dropwise, until the pink colour persists for 30 sec. Dissolve 1 g of the sample, weighed to the nearest mg, in the heated solution, and titrate with 0.1N potassium permanganate to a pink colour that persists for 15 sec. Not more than 0.5 ml should be required.

Arsenic

Not more than 3 mg/kg

A sample solution prepared as directed for organic compounds meets the requirements of the limit Test for Arsenic (Method II).

Heavy metals

Not more than 10 mg/kg

Weigh 4 g of the sample to the nearest mg and dissolve in 40 ml of water. Add dropwise, with vigorous stirring, 10 ml of dilute hydrochloric acid TS and filter. A 25-ml portion of the filtrate meets the requirements of the Limit Test (Method I).

METHOD OF ASSAY

Weigh, to the nearest mg, 3 g of the sample previously dried for 4 h at 105o and transfer to a 250-ml Erlenmeyer flask. Add 50 ml of water to dissolve the sample. Neutralize the solution, if necessary, with 0.1N hydrochloric acid, using phenolphthalein TS as indicator. Add 50 ml of ether and a few drops of bromophenol blue TS, and titrate with 0.5N hydrochloric acid, shaking the flask constantly, until the colour of the indicator begins to change. Transfer the lower aqueous layer to another flask. Wash the ethereal layer with 10 ml of water, and add the washing and an additional 20 ml of ether to the separated aqueous layer. Complete the titration with the 0.5N hydrochloric acid, shaking constantly the flask. Each ml of 0.5N hydrochloric acid is equivalent to 72.05 mg of C7H5NaO2.


Source: Joint FAO/WHO Expert Committee on Food Additives (JECFA)


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