The sodium is melted under xylene and cast into cylindrical blocks for convenience of cutting. A cog-wheel mechanism brings the block against a horizontal cutter, which removes a slice of the metal at each movement.

The acetic ether must be quite free from water and alcohol, it should boil between 78° and 79°; and bright slices of metallic sodium immersed in it should remain unattacked for at least two hours.

For the reaction operation, a hemispherical copper vessel of fully 100 litres capacity is employed. It is heated by an oil-bath, and is provided with copper coils by means of which it can either be warmed with steam or cooled with water, as may be required. To allow rapid introduction of the sodium, the vessel has a wide manhole with a lid which can be easily removed. Great care is necessary in the charging, to avoid accidental access of water.

The reaction-vessel is connected through a copper condenser with a receiver, from which the condensed acetic ether which distils over in the early stages can be passed back to the reaction-vessel as desired. This serves not only to restore the supply of acetic ether, but also to moderate the action by reducing the temperature of the mixture. Care is taken that the reaction-vessel is perfectly dry before charging, and that no water can enter in the subsequent stages.

1 Chem. Zeit., 1914, 38, 665.

Forty kilograms of acetic ether are placed in the cold vessel followed by 5 kilograms of sodium shavings. By means of wooden spatulas the latter are quickly immersed and distributed. The apparatus is then closed, and the oil-bath slowly heated to 100°, but not above 105°. The temperature of the mixture in the vessel is recorded by a thermometer; it should only rise slowly. If there is a rapid rise, it indicates an irregular reaction, probably due to water or alcohol present in the ingredients, or admitted inadvertently.

When the temperature of the mixture reaches 45-50°, the heating is stopped. The reaction, however, proceeds, with increasing temperature until the boiling point of the acetic ether is attained (78-80°), when this ingredient begins to distil over. The oil-bath temperature is now kept at 55-60°. When sufficient distillate has collected in the receiver, it is run back into the reaction-vessel. The temperature in this vessel should not rise above 82-83°.

After about 30-45 minutes the distillation slackens. When this occurs, external heating is again applied, in such manner as to maintain a very slow distillation of acetic ether during the next 5-6 hours, by the end of which time the reaction is completed.

The contents of the reaction-vessel, consisting of sodium aceto acetic ester, sodium alcoholate, alcohol, and excess of acetic ether, are now forced out into another vessel, lead-lined, and provided with a stirring-apparatus. This vessel contains 35 litres of water for every 5 kilograms of sodium employed, together with the calculated quantity of acetic acid required for combining with the sodium. After half an hour's mixing, the liquid is passed into a separator, allowed to settle out during several hours, and the lower aqueous layer then run off. The upper layer, consisting of ethyl acetoacetate mixed with alcohol and acetic ether, is distilled until the boiling point rises to 110°, thus separating most of the acetic ether and alcohol. The residue of crude ethyl acetoacetate is then rectified by distillation under reduced pressure in a strong vessel of tinned copper, heated by an oil-bath. At 10-15 mm. pressure the ethyl acetoacetate distils over between 86° and 92°. Between the condenser and the receiver a sampling device is inserted, so that the specific gravity of the distillate passing over can be ascertained; the limits 1.030 and 1.040 indicate the fraction which is collected as the final product.

For use in preparing antipyrine, a very pure acetoacetic ester is required, since the success of the reactions depends largely upon the purity of the ester. The latter should yield not more than

4 per cent. of distillate below 180°, when distilled under 750 mm. pressure, and 95 per cent. should boil between 180° and 181° at the pressure mentioned. Also the ester should contain at most

05 per cent. by weight of acetic acid, phenolphthalein indicator being used in the test.1

The recovered acetic ether, as also the alcohol produced in the reactions, are purified and concentrated for subsequent use.

The lower, light-yellow layer in the decomposition vessel consists of a solution of sodium acetate, with some alcohol and acetic ether. After distilling off the alcohol and ether, the solution is evaporated and the sodium acetat3 recovered by crystallisation.

Ethyl acetoacetate is a colourless liquid, with a pleasant, fruity odour. It boils at 181-182°, or at 1806-1812 under 754 mm. pressure; or at 71°, under 125 mm. Sp. gr. 10282 at 20°/4°. With ferric chloride, it gives a violet coloration.

Ethyl formate (Formic ether), H.COOC2H5. - According to Senderens and Aboulenc,2 a convenient procedure for the industrial production of ethyl formate is to heat together a mixture of alcohol and formic acid in molecular proportions, in the presence of a small quantity of sulphuric acid - from 1 to 2 per cent. of the volume of the mixture. Anhydrous aluminium sulphate or potassium bisulphate can also be used as catalysts, but the best results are given with the sulphuric acid.

Kopp's method is as follows.3 A cooled mixture of 7 parts by weight of alcohol (88 per cent. strength) and 11 parts of strong sulphuric acid, is poured on to 8 parts of anhydrous sodium formate, and the whole carefully distilled from a water-bath. The yield of ester, however, is less than 80 per cent. of the theoretical quantity, and the product contains some formic acid. To remove this it is shaken with milk of lime, then dried with calcium chloride, and rectified.

By using sodium bisulphate instead of sulphuric acid, a better yield is obtained, and the ester produced is nearly free from acid.4 The bisulphate (240 parts) is well crushed, and mixed with 46 parts (weight) of alcohol and 68 parts of sodium formate. This mixture is warmed in a closed vessel, with frequent stirring, for about ten hours at a temperature of 80°; or, alternatively, it may be gently boiled in a vessel fitted with a reflux condenser. At the end of that time, the ethyl formate is distilled off.

1 Ullmann, "Enzyklop. der Techn. Chem.", 1, 99.

2 Compt. rend., 1911, 152, 1671. 3 Annalen, 1845, 55, 180. 4 Engelskirchen, D.R,-P. 255441.

The following process has long been used industrially for making the ethyl formate employed for fabricating "rum essence." Potato starch, 45 kilos., is well mixed with 14.5 kilos. of pyrolusite (containing 85 per cent. of MnO2) and 67 kilos. of water. Into this is poured a cooled mixture of 10 kilos. of alcohol (80 per cent.) and 14 kilos. of strong sulphuric acid. Crude acetic acid is sometimes included: see under "imitation rum," p. 437. The vessel is connected with a condenser, and heat applied to start the reaction, but no further heating is required until towards the end of the process. From 7 to 8 kilos. of formic ester are obtained. The reaction proceeds rapidly, so that six or seven charges can be worked off in a day, and about 50 kilos. of crude ethyl formate obtained.1

Ethyl formate is a volatile and inflammable liquid, boiling at 544°, and of sp. gr. 0948 at 0°/4°. It has some little application in medicine and in synthetic chemistry, but is chiefly used for the preparation of artificial rum.

Methyl formate, prepared in an analogous manner to that employed for the ethyl ester, is employed industrially as a solvent for acetyl-cellulose. It boils at 323°.