Alcohol is very largely employed as a solvent. This, in fact, is its function in most of the manufactures indicated by the table above referred to. Where it is so used, the products may be divided into two classes: (1), those in which the spirit remains as part of the finished article; and (2), those from which the alcohol, after having served its purpose, is expelled in the subsequent stages of the manufacture.

As examples of the first class may be mentioned " finish," polish, varnish, and stains; embrocations, liniments, and lotions; hair washes; cattle medicines; plant washes, insecticides, and sheep dips; dye solutions; and collodion. Here the alcohol serves to dissolve and keep in solution some ingredient of the article which is not soluble in water, such as resin, oil, colouring matter, or organic drug. Thus "finish" (used by polishers and others) is a solution of resin or gum-resin in alcohol; liniments may contain various organic drugs such as aconite, belladonna, or camphor; collodion is a solution of gun-cotton in alcohol and ether; and so on almost ad infinitum.

As instances of the second group may be cited celluloid, soap, solid medicinal extracts, photographic plates, silk, artificial flowers, and textile printing.

In the preparation of celluloid, for example, alcohol is used to dissolve the camphor which is one of the ingredients of the product, the spirit being eventually dried off.

In soap-making, alcohol is employed to clarify the "transparent" varieties. Dried soap is dissolved in the spirit, and most of the latter is distilled away. The residual mass is formed into bars or cakes and stored at the ordinary temperature, when the rest of the alcohol gradually evaporates and the soap slowly becomes translucent.

To obtain medicinal extracts economically, the crude drugs (roots, barks, and other parts of plants) are extracted with industrial methylated spirit, which is then distilled from the solution so produced, and much of it recovered for future use. The residual solid extract can then be dissolved in pure (duty-paid) alcohol to form the medicinal liquid extract, which in this country cannot legally (if capable of internal use) contain methylated spirit. This procedure obviates the use, and the consequent unavoidable loss, of the expensive duty-paid alcohol in the actual extraction of the crude drug.

In photography, alcohol is employed as a solvent for the collodion used in preparing collodion-emulsions. It is also used for the drying of plates and the making of photographic varnishes, and as a solvent for colours in colour-photography.

In making artificial silk, alcohol (2 volumes) is mixed with ether (3 volumes) as a solvent for the nitro-cellulose which forms the basis of the product. The solution is essentially a kind of collodion. It is forced through tubes, of diminishing calibre, until it finally emerges as very fine filaments, which dry as they reach the air and are spun together to form the working thread. In silk dyeing, as also in the colouring of artificial flowers and in calico printing, alcohol is a solvent for the dye-stuff employed.

Another important application of the solvent properties of alcohol is in the purification of fine chemicals by crystallisation. The impure substance is usually dissolved in warm or cold alcohol of suitable strength, filtered from solid impurities if necessary, and the solution allowed to crystallise.

Alcohol as raw material, - In the foregoing cases, the alcohol either remains as an ingredient of the finished product, or is removed at some stage; but in either event it still retains its identity as alcohol. In other instances, however, the ethyl (or methyl) group of the alcohol enters into the molecular composition of the product, and qua alcohol the original spirit is destroyed. Thus, for instance, alcohol may be transformed into ether or chloroform. In other words, it serves as the raw material for the manufacture of these compounds.

The chief products manufactured from alcohol in this sense may be grouped as follows: -

(1). Anesthetics and antiseptics: Ether; ethyl chloride and bromide; chloral, chloroform, and bromoform; iodoform.

(2). Esters of fatty acids: Ethyl formate, acetate, butyrate, propionate; ethyl acetoacetate, etc.

(3). Synthetic drugs: Phenacetin; antipyrin, etc.

(4). Dyestuff intermediates: Methyl and ethyl anilines, etc.

(5). Aldehyde and formaldehyde.

(6). Acetic acid and vinegar.

In the following pages the preparation of these and a few other compounds obtained from alcohol is described.