A general method for obtaining the ethyl esters such as formate, acetate, butyrate, etc., is to distil a mixture of alcohol, a salt of the acid in question, and sulphuric acid. Instead of the salt, the acid itself is often used. Ethyl acetate, in fact, is usually on the large scale made from alcohol, acetic acid, and sulphuric acid; sodium acetate is less frequently employed. The sulphuric acid may be omitted if a suitable catalyst is used. When both acids are employed, a satisfactory mixture is alcohol (95 per cent.) 6 vols., acetic acid 4 vols., sulphuric acid 5 vols.1

The mixture of alcohol and the two acids is distilled from a vessel fitted with a fractionating column, in which a certain amount of rectification takes place. The issuing vapours, consisting of the ester, free acetic acid, alcohol, and water, pass through a vessel containing a suitable basic substance to retain the free acid, or most of it, and then into a condenser. The distillate is collected in receivers fitted with stirrers, in which it is washed with water and dilute alkaline solutions to remove alcohol and any acid that may have escaped elimination in the first vessel. It is then dried over calcium chloride and rectified by redistillation.

On a small scale the. following procedure, described by Dr. Inglis Clark,2 may be adopted.

Place 283 c.c. of rectified spirit (sp. gr. 0 838) in a copper or glass flask, and into it pour the same volume of sulphuric acid, with stirring, and keeping the flask cool. Allow the mixture to stand, and when its temperature has fallen to about 155°, gradually add 351 grams of dried sodium acetate, with constant agitation to ensure thorough mixture, keeping the flask as cool as possible, and connecting it with an inverted condenser to avoid loss. When all has been added, reverse the condenser, and distil the contents of the flask by means of a naked flame or a sand-bath till 400 c.c. have passed over. Digest the distillate for three days with 57 grams of freshly-dried potassium carbonate. Filter, and distil the filtrate with the aid of a water-bath, stopping the distillation before the last 30 c.c. have passed over.

1 See, however, Senderens and Aboulenc's process, under Ethyl Formate, p. 348.

2 Pharm. J., 1883, [iii], 13, 777. See also Wade, Trans, Chem. Soc, 1905, 87, 1656.

Clark remarks that the excess of sulphuric acid employed secures the absence of alcohol from the distillate, whilst the action of this excess on the ethyl acetate formed is minimised by securing thorough mixture before applying heat. Alcohol being absent from the distillate, it is only necessary to neutralise and free the ester from water. For this purpose, potassium carbonate is recommended as being most convenient on a small scale, but sodium acetate is equally efficient.

Using the quantities stated above, there were distilled off 405 c.c, which contained 3387 grams of ethyl acetate. The sp. gr. of the distillate was 0912; after washing the ester with water and digesting with potassium carbonate, the sp. gr. was found slowly to diminish. After thirty hours, it was 09023, when it contained 99.36 of real acetic ether.

Pure ethyl acetate, CH3COO C2H5, boils at 77.2°, and has the sp. gr. 09072 at 15°/l5°. Commercial "acetic ether" often contains 25 per cent. or more of impurities, consisting mainly of water, alcohol, acetic acid, and ordinary ether. Acetic ether B.P., used in pharmacy, is required to contain not less than 90 per cent. of ethyl acetate, and to have a sp. gr. 0.900 to 0 907.

In this country pure acetic ether is required to be made from duty-paid alcohol; but a denatured product is allowed to be prepared from specially-denatured industrial alcohol. The de-naturants sanctioned vary according to the circumstances - e.g., according to whether the ethyl acetate is to be used, on the premises where it was made, as an intermediate product in the preparation of other compounds, or removed for sale as a solvent, etc.

Ethyl acetoacetate (Acetoacetic ether),

CH3COCH1.COO C2H5. - This product is used in making certain synthetic chemicals, of which the most important commercially is antipyrine, or methyl-phenylpyrazolone. The ethyl acetoacetate is prepared from acetic ether by the action of metallic sodium, followed by treatment with acetic acid. On a small scale, the procedure is as follows: -

One kilogram of acetic ether, carefully dehydrated with calcium chloride, is placed in a large flask (2 to 3 litres capacity) fitted with a reflux condenser. To it are added 100 grams of sodium cut into thin pieces, the flask being cooled meanwhile. An energetic reaction commences, causing the liquid to boil. After the reaction has moderated and no more heat is evolved, the mixture is heated on a water-bath, using the reflux condenser, for about two to two and a half hours, until the sodium is all dissolved. The condenser is now reversed, the excess of acetic ether distilled off, and to the warm residual liquid 550 grams of 50 per cent. acetic acid are added, the whole being well mixed. After cooling, 500 c.c. of water are poured in, and the mixture again well agitated. On standing, the aceto-acetic ester separates out as an upper layer. It is drawn off, washed with a small quantity of water, separated from this water, and fractionally distilled. Five fractions are collected, corresponding with the temperatures 100-130-165-175-185-200°; these fractions are then refractionated twice. The final product boiling between 175-185° is nearly pure ethyl acetoacetate: the yield of this should be about 175 grams.

The production of ethyl acetoacetate on a larger scale has been described in detail by A. Cobenzl.1

By means of a cutting device, immersed in xylene, the sodium is obtained in very thin slices or shavings. A large surface of the clean bright metal can thus be exposed to the action of the acetic ether. Sodium encrusted with oxidation-products should not be used, as the moisture liable to be present may give rise to irregularities in the reaction.