Monographs: Pharmaceutical substances: Ethanol (Ethanolum)


Relative molecular mass. 46.07

Chemical name. Ethyl alcohol; ethanol; CAS Reg. No. 64-17-5.

Other name. Absolute alcohol, dehydrated alcohol.

Description. A colourless, clear and mobile liquid; odour, characteristic.

Miscibility. Miscible with water and ether R.

Category. Solvent; antiseptic.

Storage. Ethanol should be kept in a well-closed container, and stored whenever possible at a temperature between 8 and 15 °C.

Additional information. Ethanol is flammable, burning with a blue smokeless flame. Hygroscopic. Boiling point, about 79 °C.


Ethanol contains not less than 98.8% v/v and not more than the equivalent of 100.0% v/v of C2H6O, corresponding to not less than 98.1% m/m and not more than the equivalent of 100.0% m/mof C2H6O.

Identity tests

A. Place 0.25 mL in a small beaker, add 1 mL of potassium permanganate (10 g/l) TS and 0.5 mL of sulfuric acid (0.5 mol/l) VS, and cover the beaker immediately with a filter-paper moistened with a recently prepared solution of 0.1 g of sodium nitroprusside R and 0.5 g of piperazine hydrate R in 5 mL of water; a dark blue colour is produced on the filter-paper, that fades after a few minutes.

B. To a few drops add 1 mL of sulfuric acid (~1760 g/l) TS and a few drops of potassium dichromate (100 g/l) TS; a green colour is produced and an odour of acetaldehyde is perceptible.

Relative density. = 0.7904 - 0.7935

Non-volatile residue. Place 100 mL in a porcelain dish and heat on a water-bath until volatilized, dry the residue at 105 °C for 1 hour, and weigh; not more than 5 mg.

Water-insoluble substances. Dilute a volume of Ethanol with an equal volume of water; the mixture is clear and, after cooling to 10 °C, it remains clear for 30 minutes.

Acidity. Add 20 mL of carbon-dioxide-free water R and 3 drops of phenolphthalein/ethanol TS to 20 mL of Ethanol; the colour remains unchanged. Titrate with carbonate-free sodium hydroxide (0.02 mol/l) VS; not more than 0.5 mL is required to obtain the midpoint of the indicator (pink).

Aldehydes and other foreign organic substances. Thoroughly clean a glass-stoppered cylinder with hydrochloric acid (~250 g/l) TS, rinse with water and the Ethanol to be examined. Place 20 mL of Ethanol in the cylinder. Cool the contents to about 15 °C and, by means of a carefully cleaned pipette, add 0.1 mL of potassium permanganate (0.02 mol/l) VS, noting the time of the addition. Mix at once by inverting the stoppered cylinder, and allow to stand at 15 °C for exactly 5 minutes; the pink colour does not entirely disappear.

Fusel oil and allied impurities. Allow 25 mL to evaporate spontaneously from a porcelain dish, carefully protected from dust, until the surface of the dish is barely moist; no foreign odour is perceptible, and on the addition of a few drops of sulfuric acid (~1760 g/l) TS, no red or brown colour develops.

Methanol. To 1 drop add 1 drop of water, 1 drop of phosphoric acid (~105 g/l) TS, and 2 drops of potassium permanganate (25 g/l) TS. Mix, allow to stand for 1 minute, and add, drop by drop, sodium metabisulfite (50 g/l) TS until the permanganate colour is discharged. If a brown colour remains, add 1 drop of phosphoric acid (~105 g/l) TS. To the colourless solution add 5 mL of freshly prepared disodium chromotropate TS, and heat on a water-bath at 60 °C for 10 minutes; no violet colour appears.

Benzene. Record an absorption spectrum of the Ethanol in a 1-cm layer against water between 220 nm and 350 nm. The absorbance at about 220 nm is not more than 0.30, at about 230 nm not more than 0.18, at about 240 nm not more than 0.08, and at about 270 to 350 nm not more than 0.02. A curve drawn through these points is smooth.

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