A mixture of alcohol

(93 per cent.) and concentrated hydrochloric acid, in the proportion of 40 kilos, of the former to 100 kilos, of the latter, is carefully heated in a lead-lined autoclave. When the main reaction is over, the temperature is raised to 130° for about five hours, after which the vessel is allowed to cool down to 50-60° and the liquid distilled into a cooled metal receiver. The product, which contains a little hydrochloric acid, alcohol, etc., may be rectified from slightly alkaline water to remove these impurities. Alternatively, before the ethyl chloride vapour is condensed, it may be passed first through a washing vessel containing water to remove acid and alcohol, and then through a column packed with fragments of earthenware, in which higher-boiling by-products are condensed. Finally it is led through a refrigerator to a fractionating vessel. From this it is distilled by means of a water-bath, the vapour being passed through strong sulphuric acid contained in a leaden vessel, and again condensed. The finished product is filled into sealed tubes or flasks for transport and use.

In another method the use of an autoclave is dispensed with, but calcium chloride or zinc chloride is used as a catalyst. If calcium chloride (or other catalyst) is not employed, a larger proportion of hydrochloric acid must be used.

Besides being used as an anaesthetic, ethyl chloride is frequently employed as an alkylating agent, especially for amines and phenols, in the synthesis of dyestuffs and other chemical products. It is gaseous at the ordinary temperature, the boiling-point being 12.5°. Its sp. gr. at 0° is 0921.

Methyl chloride may be prepared in a manner similar to that described for ethyl chloride, using methyl alcohol, sodium chloride, and sulphuric acid. Or Groves's process can be used. Melted zinc chloride, 1 part, is dissolved in 2 parts of methyl alcohol. Then gaseous hydrochloric acid is passed into the mixture, and the resulting methyl chloride distilled off and purified.1

On the large scale, however, it is obtained by the dry distillation of vinasses, a residue left in the manufacture of sugar from beetroot. Methylamine is evolved; this is converted into the hydrochloride, and heated to a temperature of 260-300°. Methyl chloride, mixed with methylamine and trimethylamine, is given off; the two latter can be removed by means of hydrochloric acid, and the residual methyl chloride, after being dried over calcium chloride, is condensed by pressure into steel cylinders.

A general method of obtaining the halide compounds of methyl and ethyl alcohols is described in a German patent.2

The alcohol is heated with an aqueous solution of the halogen acid and the corresponding calcium halide in an open vessel at a temperature not above 100°. Thus a good yield of ethyl chloride is said to be obtained by warming ethyl alcohol and aqueous hydrochloric acid (19° Be.= sp. gr. 1.152) in the presence of anhydrous calcium chloride. Alternatively, a mixture of acid and methyl or ethyl alcohol is allowed to flow continuously into a vessel containing heated calcium chloride.