The most important of these industrially are the dimethyl sulphate and the salts of monoethyl sulphate. The former is much used as a methylating agent, especially for phenols and for amines of the aromatic series. The reaction in the latter case is expressed by the equation: - (CH3)2SO4 + 2RNH1 = RNH1CH3HSO4 + RNH(CH3).

The salts of ethyl hydrogen sulphate are employed for ethylating phenols - as, for example, p-nitrophenol in the preparation of phenacetin; and for the making of ethyl mercaptan, etc.

These alkyl sulphates serve as a cheap raw material for use in

1 Millon, Ann. Chim. Phys., 1843, [iii], 8, 233.

2 Lossen: Annalen, 18G8, Suppl. 0, 220.

A A such operations as the foregoing. The dimethyl compound especially has been of signal service in the synthetic dye industry.