Alcohol is not only used as a solvent in the manufacture of these articles: it frequently enters into their composition. An ethyl or a methyl group, as the case may be, is introduced into the molecule of the product.

The alcohol itself is not, in general, employed directly for this purpose. It is first converted into an intermediate compound which serves as the actual "ethylating " or "methylating" agent. Thus ethyl chloride, bromide, iodide, and sulphate are commonly employed to introduce the ethyl group into a compound. The corresponding methyl salts serve a similar purpose where a methyl group is required.

As illustrative examples the following may be mentioned.

The photographic developer known as "Metol" is obtained by methylating para-amidophenol, methyl sulphate being conveniently used for the purpose.

Vanillin, employed extensively as a flavouring and in perfumery, may be synthesised by methylating protocatechuic aldehyde. The latter is dissolved in a strong solution of sodium carbonate, dimethyl sulphate added, and the mixture heated to effect the required combination.

Phenacetin, of which large quantities are employed in medicine, is produced by ethylating para-nitrophenol, reducing the product, and acetylating it; or by alternative methods in which the ethyla-tion follows the acetylation, instead of preceding it. Ethyl chloride, bromide, or iodide, or sodium ethyl sulphate, is commonly employed as the ethylating agent.

Antipyrin, also largely used in medicine, is an example of somewhat different character. It is obtained by the combination of ethyl acetoacetate and phenylhydrazine. Alcohol furnishes the raw material for production of the ethyl acetoacetate.