To obtain this ester, 2 parts of butyric acid may be mixed with 2 parts of 95 per cent. alcohol, and the mixture warmed to 80° with 1 part of strong sulphuric acid. The product is then poured into water and allowed to stand: the ethyl butyrate separates out as an oil on the top of the liquid. It is drawn off, washed with sodium carbonate solution, and rectified by distillation.2 Or, alternatively, the separated ester may be treated with calcium carbonate to neutralise acidity, dehydrated with fused calcium chloride, and distilled; and then finally rectified by re-distillation over calcined magnesia.

A smaller proportion of alcohol and sulphuric acid is required by proceeding as follows. Ten parts of alcohol, 16 of butyric acid, and 1 of sulphuric acid are heated together to 80°, and allowed to stand for twelve hours. The product is separated, washed with water and with dilute sodium carbonate solution, and rectified.

Ethyl butyrate is a colourless, mobile liquid, of pleasant, fruity odour; it boils at 119.9°, and has the sp. gr. 08978 at 18°. The cruder commercial varieties have some application as solvents; the purer qualities are largely used for the preparation of artificial rum and fruit essences.

1 J. Stinde, Ding. Polyt. J., 1866, 181, 402.

2 Roscoe and Schorlemmer, "Treatise on Chemistry," 3, [i], 505.

Ethyl butyrate and ethyl propionate are now obtained on a considerable scale as by-products in the preparation of acetone and potassium salts from kelp. They are employed as solvents for resins, in place of amyl acetate.

Ethyl benzoate, C6H5COO C2H5, is used to some extent in making perfumes and fruit essences, and also in the production of synthetic chemicals. It is prepared by mixing benzoic acid, 1 part, with absolute alcohol, 2 parts, and passing a current of dried hydrochloric acid gas through the liquid. The gas is conveniently obtained by dropping strong sulphuric acid into a flask containing concentrated hydrochloric acid. The dissolution of the benzoic acid in the alcohol is effected in the course of passing the gas into the mixture, by means of the heat evolved in the reaction. Winn the vessel cools down again it is heated on a steam-bath, and the current of gas continued until fumes of the acid come off. On pouring the liquid into water, the ethyl benzoate separates out as an oily liquid which collects at the bottom of the vessel. It is drawn off, and treated with dilute solution of sodium carbonate in order to femove free benzoic acid; then shaken with water to remove sodium carbonate; separated, dehydrated over potassium carbonate, and distilled.

Ethyl benzoate is a colourless, oily liquid boiling at 2112°, and of sp. gr. 1.0502.

Methyl benzoate, C6H5COO.CH3, is prepared by distilling a mixture of benzoic acid (50 parts by weight), methyl alcohol (120parts by volume), and strong sulphuric acid (6 parts by volume). It is a colourless liquid of pleasant odour; boiling point 198.6, and sp. gr. 1.0942 at 15°/15°. The ester is used in perfumery, and is known as "Niobe oil."

Methyl salicylate, C6H4(OH)COO.CH3, is made artificially by distilling a mixture of 2 parts of salicylic acid, 2 of methyl alcohol, and 1 of strong sulphuric acid. It boils at 2222°, and has the sp. gr. 1189 at 15°/15°, or 1196 at 0°. It is used somewhat extensively in pharmacy, and also in perfumery. The naturally occurring ester is the chief constituent of oil of wintergreen (Gaultheria) and oil of Betula alba.