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The oxidation of alcohol may be effected by the agency of chlorine, and in that case an intermediate oily product is obtained, in which three of the hydrogen atoms of the aldehyde are replaced by three of chlorine. The compound resulting is chloral (CCl3CHO), and this readily combines with water and forms the familiar chloral hydrate crystals which were first prepared by Liebig in 1832, but only got into the "British Pharmacopœia" (Additions) in 1874. Chloral hydrate treated with caustic potash splits into chloroform and potassium formate. Chloroform was discovered in 1831 by Liebig and Soubeiran, and was admitted into the "London Pharmacopœia" of 1851, four years after Simpson had demonstrated its wonderful anæsthetic property.

Returning to acetic acid, it may be stated that by heating its calcium salt two substances, acetone, (CH3)2CO, and calcium carbonate are formed. Also that when alcohol is acted upon by phosphorus pentasulphide, mercaptan, C2H5SH, is obtained. By the reaction of acetone and mercaptan, mercaptol results, and this, when oxidised, becomes the well-known synthetic hypnotic, sulphonal. It is not necessary to give the full formulas of these reactions, as they may be found in the usual chemical manuals; but it may be stated that the full descriptive name of sulphonal is dimethyl-*diethylsulphone-methane. The group of sulphones furnishes an illustration of the reasoning on which new