This product is used to some extent medicinally, two spirituous solutions containing it being described in the British Pharmacopoeia. Chiefly, however, it is employed commercially for use in the preparation of various essences. For this purpose the pure nitrite itself is not prepared, but an alcoholic solution of it, which contains small quantities of acetaldehyde and ethyl acetate as well as the nitrite.

To obtain this industrial variety, 3 parts of 25 per cent. nitric acid are covered with 5 parts of alcohol, and set aside without shaking up for two days. Then 5 parts more of alcohol are added, and the mixture distilled from a steam-heated, acid-resisting retort until yellow vapours begin to appear. Calcined magnesia is then added to the distillate to neutralise the acidity, and the mixture set aside for twenty-four hours. It is then filtered, and 2 parts of alcohol added to the filtrate, which is then rectified, using gentle warming at first, until 8 parts of distillate have passed over.

Alternatively, a mixture of 3 parts of crude 40 per cent. nitric acid with 12 parts of alcohol (90 to 91 per cent.) is carefully distilled from a water-bath until red fumes appear. The distillate is then neutralised with calcined magnesia as before, and after twenty-four hours poured off clear. Three parts of alcohol are now added, and the liquid distilled until 10 parts have been collected; the whole of this is finally rectified again.

The product, as stated above, is an alcoholic solution of ethyl nitrite, but containing also aldehyde and acetic ether. It is liable to become acid on keeping, and may then be again neutralised with magnesia and redistilled.

To obtain practically pure ethyl nitrite, a process worked out by Dunstan and Dymond may be adopted.1 In this method, no distillation is required.

Dilute sulphuric acid is made to react with sodium nitrite and alcohol at a low temperature. The quantities of the reacting compounds are calculated from the two equations: -

A solution is made by dissolving (345) grams of sodium nitrite in water. The liquid is diluted to 120 c.c. and cooled below 0° by means of an ice- and salt-bath. Commercial sodium nitrite is of 95-98 per cent. purity, and hence a quantity corresponding with 34.5 grams of the pure salt must be taken. A slight excess does not interfere with the reaction.

13.5 C.c. of sulphuric acid are added to a cooled mixture of 32 c.c. of rectified spirit with an equal volume of water; the liquid is then diluted to 120 c.c. and cooled below 0°. This acid liquid is allowed gradually to pass through a thistle funnel, with constant stirring, to the bottom of the solution of sodium nitrite, contained in a long, narrow glass vessel surrounded by ice and salt. When the acid has been added, a pale yellow layer of ethyl nitrite is found, completely separated from the lower layer of solution of sodium sulphate. Melting ice alone may be used for the cooling, but the acid must then be added very slowly and carefully, to prevent rise of temperature and evolution of nitrous fumes.

1 Pharm. J., 1888, [iii], 18, 861.

The ethyl nitrite so formed contains only traces of alcohol and water. The alcohol is removed, almost completely, by shaking with cold water in a separator; the water by digestion with freshly ignited potassium carbonate.

From 30 to 35 grams of ethyl nitrite are obtained; the calculated yield is 375 grams. The product is almost pure, if not absolutely so.

A somewhat similar process has been described by Feldhaus,1 but in this case the ester is separated by volatilisation and condensed. One litre of 45 per cent. alcohol is mixed with 500 grams of potassium nitrite, and the solution cooled in an ice-bath. A mixture made with 500 grams each of water, alcohol, and sulphuric acid is dropped slowly into the first solution, the vessel containing which is attached to a condenser. The heat of the reaction suffices to volatilise the ethyl nitrite, which is condensed and collected in a cooled receiver.

Pure ethyl nitrite is a mobile liquid, of boiling point 17.5°, according to Dunstan and Dymond, and sp. gr. 0917 at 0°/0°. It is very prone to decomposition in the presence of water or traces of acid. The Pharmacopoeia "solution of ethyl nitrite " is a solution of 25 to 3 per cent. by weight of ethyl nitrite in a mixture of 95 volumes of absolute alcohol with 5 volumes of glycerin. The glycerin acts as a preservative, presumably by reason of its affinity for water.

"Spirit of nitrous ether" (Sweet Spirit of Nitre) is an alcoholic solution containing, according to the British official requirements, from 1.52 to 266 per cent. by weight of ethyl nitrite, together with aldehyde and other allied substances. The Pharmacopoeia directions for preparing it are to add gradually 100 c.c. of sulphuric acid to a litre of 90 per cent. alcohol, and then 125 c.c. of nitric acid, stirring constantly. The mixture is transferred to a retort or flask containing 100 grams of copper wire or turnings, and distilled gently at a temperature at first about 77°, and rising to 80°, but which does not exceed 82°. The receiver contains 1 litre of 90 per cent. alcohol, and is cooled with ice-water. When the volume of liquid in the receiver has been increased to 1,600 c.c, the retort is allowed to cool, 25 c.c. more nitric acid added, and distillation continued until the receiver contains 1,700 c.c. This is mixed with another litre of alcohol (90 per cent.), or with such a quantity as will make the product contain 2.66 per cent. by weight of ethyl nitrite.

1 Annalen. 1863, 126, 71.