This is somewhat more difficult to prepare, and gives a lower yield, than the corresponding dimethyl compound, but may be obtained in a similar manner. Sulphuric anhydride (17.4 kilos.) is run into 10 kilos. of absolute ethyl alcohol at a temperature of - 10° to - 20°, and the mixture distilled in a vacuum. The yield is 7 to 8 kilos., or about one-half of the theoretical quantity.2

Alternatively, absolute alcohol is mixed with Nordhausen sulphuric acid, the ethyl salt extracted with chloroform, and the product distilled in vacuo.3

1 Merck, D.R.P., 77278. 2 Ibid., D.R.P., 133542.

3 Claesson and Lundvall, Ber., 1880, 13, 1699.

A yield of 83-90 per cent. is said to be obtained by distilling sodium ethyl sulphate in vacuo.1

Diethyl sulphate has not much technical application. It is an oily liquid, boiling at 208° (with decomposition), or at 96° under 15 mm. pressure, or 118° under 40 mm. Sp. gr. 11837 at 19°. The compound has toxic properties.

Irvine and Haworth1 describe a method of obtaining methyl and ethyl sulphates by the action of sulphuryl chloride upon the alcohols. Or, instead of preparing the sulphuryl chloride first, chlorine and sulphur dioxide may be passed into the alcohol in equimolecular quantities. On distillation of the final reaction-product under reduced pressure, the alkyl hydrogen sulphate, formed together with the dialkyl compound, undergoes decomposition into sulphuric acid and dialkyl sulphate, so that the latter is obtained in good yield.

A similar process is described by Boake and Durrans.3 Into 32 parts by weight of anhydrous methyl alcohol is passed about 35 parts by weight of chlorine, and the same weight of sulphur dioxide. This is an excess (3 parts) of the dioxide, which excess may be added at the start and maintained throughout the addition of the mixed gases. After expelling the excess of sulphur dioxide on a water-bath, the product, containing dimethyl sulphate, methyl hydrogen sulphate, methyl chloride, and some hydrochloric acid, can be used as a methylating agent; or the methyl chloride can be distilled off at the ordinary pressure and recovered, and dimethyl sulphate obtained by distilling the residue under reduced pressure (40 mm.) and re-distilling the product at 24 mm.