The ordinary forms of liquors (namely, whisky, rum, and gin), are prepared by the distillation of alcoholic infusions. The process of distillation is preceded either by the conversion of the amylaceous constituents of grain, first into sugar, then into alcohol, or by the fermentation of saccharine bodies into alcohol, or, as in the case of brandy, it may be directly applied to a solution containing alcohol.

Brandy.—When genuine, brandy is the product of the distillation of various sorts of rich, light-coloured wines. The most esteemed quality is prepared in the neighbourhood of Cognac, in the Deux Charentes district, and in Armagnac; but numerous inferior grades are manufactured in Rochelle and Bordeaux and in other parts of Southern France, as well as in Spain and Portugal. In the United States, a considerable quantity is produced by the distillation of California and Ohio wine. The fermented marc and lees of grapes are also extensively utilised in the manufacture of brandy. Most of the liquor known in commerce under this name, however, is made from the spirit obtained by the distillation of potatoes, corn, and other grains, which is subsequently rectified, deodorised, and then suitably flavoured. In France, the different grades of brandy are known as eau-de-vie supÉrieure (the best quality of Cognac); eau-de-vie ordinaire (common, sp. gr. 0·9476); eau-de-vie de marc (chiefly used for mixing purposes); eau-de-vie seconde (weak and inferior); eau-de-vie À preuve de Hollande (sp. gr. 0·941); eau-de-vie À preuve d’huile (sp. gr. 0·9185); eau-de-vie forte (sp. gr. 0·8390); and esprit-de-vin (sp. gr. 0·8610).

The characteristic taste and bouquet of the original wine are to a considerable extent communicated to the resulting brandy, and upon these qualities its value is greatly dependent. Many of the remarks made in regard to the ageing, flavouring and blending of wines equally apply to brandy, and need not be repeated in this place. When freshly distilled, it is colourless, its amber tint being either due to the casks in which it has been stored, or to added caramel. The normal constituents of genuine brandy are water, alcohol (including small amounts of butylic, propylic and amylic), various ethers (acetic, oenanthic, butyric, and valerianic), aldehyde, acetic and tannic acids, and traces of sugar and the oil of wine. The specific gravity usually approximates 0·9300 (equivalent to 52 per cent. of alcohol by volume), it may, however, range from 0·9134 to 0·9381 (from 60 to 48 per cent. of alcohol). Owing to the presence of acetic acid, genuine brandy usually shows a slightly acid reaction. According to Blyth, the constituents vary as follows:—total solids, from 1 to 1·5 per cent.; ash, from ·04 to ·2 per cent.; acids (estimated as tartaric), from ·01 to ·05 per cent.; sugar from 0 to ·4 per cent. A partial examination of brandy, by KÖnig,[111] furnished the following percentages:—specific gravity, 0·8987; alcohol (by weight), 61·70; extract, 0·645; ash, 0·009. The ingredients found in twenty-five samples of brandy tested for the New York State Board of Health varied as follows:—specific gravity, 0·9297 to 0·9615; alcohol (by weight) from 25·39 to 42·96; extract, from 0·025 to 1·795; ash, from 0·002 to 0·014.

The majority of these samples were certainly abnormal in composition. Ordonneau[112] has quite recently determined by careful fractional distillation the proportions of the more important constituents of cognac brandy twenty-five years old, with the following results, the quantities being stated in grammes per hectolitre:—aldehyde, 3; ethylic acetate, 35; acetal, traces; normal propylic alcohol, 40; normal butylic alcohol, 218·6; amylic alcohol, 83·8; hexylic alcohol, 0·6; heptylic alcohol, 1·5; propionic, butyric and caproic ethers, 3; oenanthic ether, 4; amines, traces. The large proportions of normal butylic and amylic alcohols obtained are very significant. It was found that commercial alcohol, prepared from corn, potatoes and beetroot, while containing isobutylic alcohol, was entirely free from normal butylic alcohol, and the difference in flavour between genuine brandy and brandy distilled from grains would appear to be mainly due to this fact. Normal butylic alcohol is obtained when fermentation takes place under the influence of elliptical or wine yeast, whereas the iso-alcohol is the product of fermentation induced by means of beer yeast; and it was shown that, by fermenting molasses, etc., with the aid of wine yeast, a spirit was obtained which much resembled brandy in colour and flavour.

Whisky.—Whisky is the spirituous liquor prepared by distilling fermented infusions of barley, wheat, corn, and other grains. Spirits that contain over 60 per cent. of alcohol are known as “high wines,” or common spirits; those containing 90 per cent. of alcohol are often termed “cologne spirits,” the name whisky being usually given to the product of a former distillation, containing about 50 per cent. by weight of alcohol. In Great Britain, the largest amount of whisky is made in Scotland and Ireland; in the United States, the principal supply comes from the States of Illinois, Ohio, Indiana, Kentucky (Bourbon Co.), and Pennsylvania (Monongahela Co.). The grains taken differ greatly in composition. In Scotland and Ireland, malted barley (pure, or mixed with other grain) is extensively employed; in the preparation of Bourbon, partially malted corn and rye are taken, while, for Monongahela whisky, only rye (with 10 per cent. of malt) is used. The essential features of whisky-making are, first, the conversion of the starch of the grain into dextrine and glucose, which takes place in the process of mashing; the change being due to the action of the nitrogenous principle, diastase (formed during the germination of the gain); then, the transformation of the sugar into alcohol and carbonic acid by fermentation, which is induced by the addition of yeast; and, finally, the concentration of the alcohol by distillation. The quality of whisky is much affected by the nature of the grain from which it is prepared, and by the care exercised in its manufacture, more particularly in the process of distillation. The most injurious ingredient in distilled spirits is commonly known as “fusel oil,” which term comprises several products of alcoholic fermentation, possessing a higher boiling point than ethylic alcohol, and consisting chiefly of amylic alcohol, accompanied by small proportions of butylic and propylic alcohols. Several varieties of fusel oil exhibiting distinctive properties are met with, but that obtained from potato-spirit is the most common. As a rule, the spirits prepared from malted grain contain the smallest proportion. In the manufacture of whisky, a danger of promoting the formation of fusel oil is incurred by carrying on the distillation to the furthest point, in order to obtain the greatest possible quantity of alcohol. In Great Britain, the fermented mash is removed from the remaining grain before its introduction into the still; but in this country the entire mash is occasionally taken, by which means a larger yield of alcohol is supposed to be effected. This practice is evidently open to the objection that the solid matters of the wort are liable to suffer destructive distillation, and engenders the formation of fusel oil. Another result, sometimes experienced, is the imparting of a smoky flavour to the product, which was originally intentionally communicated to the famous “poteen” whisky of Ireland, by using malt dried by means of burning turf. This quality is said to be still artificially obtained by the use of creosote. Genuine whisky, when recently made, is nearly colourless; but, if preserved in casks, it gradually acquires a brownish colour. It contains minute quantities of tannic acid, and ethylic and amylic acetates and valerianates. The specific gravity generally ranges between 0·9220 and 0·9040, corresponding to 48 and 56 per cent. of alcohol. The solid extract in whisky is usually below 1 per cent., and the total volatile acids under 0·1 per cent. In regard to the average composition of whisky, chemical literature furnishes but very meagre data. The examination of a large number of samples of ordinary American whisky in 1881, for the New York State Board of Health, gave the following results:—Specific gravity ranged from 0·9018 to 0·9645; alcohol (by weight) from 23·75 to 52·58; solid residue, from 0·100 to 0·752; ash, from 0·0020 to 0·0280. Several samples of rye whisky, examined by Mr. Green,[113] showed alcohol (by weight) from 32·50 to 51·20; tannic acid, 0·0003; acetic acid, 0·0012 to 0·002; sugar, 0·002 to 0·005; solid residue, 0·160 to 0·734.

Rum.—Rum is obtained by the distillation of the fermented juice of sugar-cane or of molasses; a very considerable proportion of the article bearing this name is, however, made from grain spirit. In France and Germany the mother-liquor remaining after the extraction of beet-sugar, is utilised in the manufacture of a spirituous liquor greatly resembling rum in properties. The characteristic odour and taste of the liquor are mainly due to the presence of ethylic butyrate, and are frequently factitiously communicated to its imitations by the direct addition of this ether or of butyric acid. Grain spirit is also sometimes treated with pineapples, which likewise impart the distinctive flavour. Rum is chiefly produced in the West Indies, and in North America. The specific gravity ranges from 0·874 to 0·926; alcohol, from 50 to 70 per cent.; solid residue, from 0·7 to 1·50 per cent; ash, under 0·10 per cent.[114]

The following are the results obtained by Berkhurts, from the analysis of various samples of genuine and artificial Jamaica rum:[115]—

The variations in the composition of commercial rum would seem to be so great that little information of value concerning its authenticity is to be derived from analyses of a general character.

Gin.—Genuine Holland gin is a spirit prepared by the distillation of fermented grain infusions (rye and malted barley), flavoured with juniper berries, or oil of turpentine. Formerly the flavouring was directly introduced into the still together with the mash, but the more recent practice is to add salt, water, and juniper berries to the distilled grain spirit, and then re-distil the mixture. Numerous other aromatic substances are likewise employed in the manufacture of gin, among which are coriander, cardamom, and caraway seeds, orris, angelica, and calamus roots, cassia, bitter-almonds, sweet fennel, etc. Cayenne pepper, sugar, and acetic acid, are said to be also frequently added to gin. Gin doubtless possesses more of an artificial character than any other spirit. It is safe to assert that the great bulk of the drink sold under the name is simply grain-spirits flavoured with some of the preceding aromatics. On the other hand, the flavouring agents employed are not, as a rule, harmful in their effects, so that the quality of the liquor is mainly dependent upon the extent to which the spirits used have been rectified. It is difficult to define “pure gin,” since, owing to its compound character, it varies in composition according to the method of manufacture followed by each individual distiller. The variations found from the examination of twenty-five samples of the commercial article, tested by the New York State Board of Health, were as follow:[116]—Specific gravity, from 0·9302 to 0·9694; alcohol (by weight), from 18·64 to 44·33; solid residue, from 0·018 to 0·772; ash, from 0·001 to 0·019.

Adulteration of liquors.—Although it is notorious that the more common varieties of spirituous liquors are sophisticated, the practices resorted to are unfortunately usually of a character that does not permit of positive detection, and, unless an actual adulteration, such as the addition of some substance foreign to the genuine liquor, has been made, a chemical examination alone is frequently inadequate to distinguish between the true and the factitious article. In fact, the ordinary physical qualities, such as odour and taste, are often of greater service in determining the genuineness of distilled spirits than more scientific tests. The most prevalent form of sophistication with brandy, rum, and gin, is their artificial imitations; the direct addition of substances deleterious to health being of comparatively unfrequent occurrence. It is usual to employ a certain proportion of the genuine liquor in the fabrication of its imitation. An apparent objection to this species of adulteration is that grain spirits are liable to be used as the basis of the fictitious product, which is therefore apt to be contaminated with fusel oil, a compound producing toxic effects in a proportion fifteen times greater than ordinary ethylic alcohol.

In the United States, whisky is probably less subjected to serious sophistication than other spirituous drinks. While the blending of this liquor (i. e. the mixing of new and old grades) is almost universally practised by the refiner, and while the retail dealer often reduces its alcoholic strength by the addition of water, there is very little ground for the belief that, in this country, whisky is subjected to noxious admixture to any great extent.

A very large number of recipes have been published for the manufacture of spurious liquors; the following are characteristic, and will indicate their general nature:—

The compound known as “Brandy essence” consists of oil of grapes, 5 parts; acetic ether, 4 parts; tincture of allspice, 1 part; tincture of galls, 3 parts; and alcohol, 100 parts. “Oil of cognac” is a mixture of amylic alcohol and oenanthic ether.

According to M. Duplais, the best imitation of Cognac is the following:—

New Cognac, Montpellier, Saintonge, and other brandies are aged and improved by adding to every 100 litres: old rum, 2 litres; old kirsch, 1-3/4 litres; infusion of green walnut hulls, 3/4 litre; syrup of raisins, 2 litres.

A compound sold as “London Brandy Improver” consists of sugar syrup, acetic ether and essence of cayenne, coloured with caramel.

The preparation met with in commerce under the name of “pelargonic ether” appears to be identical with oenanthic ether.

“Rum essence” is composed of butyric ether, 15 parts; acetic ether, 2 parts; vanilla tincture, 2 parts; essence of violets, 2 parts; and alcohol, 90 parts.

The chemical examination of distilled spirits is ordinarily limited to a determination of the alcohol, solid residue, ash, and volatile acids, coupled with special qualitative and quantitative tests for any particular adulterants, the presence of which may be suspected.

(a) Alcohol.—In properly distilled liquors, a fairly approximate estimation of their alcoholic strength is effected by the specific gravity determination, which is best made by means of the special gravity bottle. In the case of spirituous liquors which contain extractive matters, it is necessary to first separate the alcohol present by the process of distillation, and then determine the density of the distillate when made up to the volume originally taken. The following table gives the percentages of alcohol by weight and by volume, and of water by volume, for specific gravities at 15°.[117]

The percentages of alcohol in the table are calculated for the temperature of 15°. The necessary correction for differences of temperature at which the determination is made is obtained by multiplying the number of degrees above or below 15°, by 0·4, and adding the product to the percentage shown by the table, when the temperature is lower than 15°, and deducting it when it is above.

Percentage of alcohol, by weight and by volume, and of water by volume, for specific gravity at 15°; water at same temperature being the unit:—

(b) Solid residue.—This is determined by evaporating 100 c.c. of the liquor in a tared platinum dish, until constant weight is obtained.

(c) Ash.—The proportion of ash is found by the incineration of the solid residue. If the presence of poisonous metallic adulterants (such as copper or lead) is suspected, a further examination of the ash is necessary.

(d) Acids.—The acidity of distilled liquors is generally due to minute quantities of acetic acid, and can be estimated by means of 1/10th normal soda solution.

Any mineral acid (e.g., sulphuric acid) supposed to be present is to be sought for in the residue remaining, after the distillation process employed in the determination of alcohol.

The presence of fusel oil in liquors is sometimes quite readily detected, by first removing the ethylic alcohol by gentle evaporation, and then inspecting the odour and taste of the still warm residue. The suspected liquor may also be agitated with an equal volume of ether, water added, and the ethereal stratum removed by means of a pipette, and concentrated by evaporation; the residue is to be examined for amylic alcohol. When distilled with a mixture of sulphuric and acetic acids, amylic alcohol is converted into amylic acetate, which may be recognised by its characteristic pear-like odour; or, the amylic alcohol can be transformed into valerianic acid (which also possesses a distinctive odour) by oxidation with sulphuric acid and potassium dichromate. Another simple qualitative test for fusel oil consists in first decolorising a small quantity of the liquor under examination with animal charcoal, adding a few drops of hydrochloric acid, and then a little freshly distilled and colourless aniline oil, when, in presence of fusel oil, it will be observed that the aniline compound acquires a perceptible rose tint as it falls to the bottom of the liquid. The quantitative determination of fusel oil presents some difficulties. A very ingenious method has been suggested by Marquardt.[118] It consists essentially in first agitating the sample with chloroform, draining off the solution obtained, washing it by repeated shaking with water, and then treating it at 85° with a mixture of 5 parts potassium dichromate, 2 parts sulphuric acid, and 30 parts of water. The valerianic acid thus formed is now separated by distilling the mixture of water and chloroform. The distillate is digested with barium carbonate, next concentrated by evaporation, and then filtered, and divided into two equal portions. One portion is evaporated to dryness, the residue taken up with water containing a little nitric acid, and the amount of barium present determined by precipitation with sulphuric acid. In the other portion, the chlorine originating from a partial oxidation of the chloroform, is to be estimated. The amount of barium combined with the chlorine, is deducted from the total quantity obtained; the remainder represents the proportion in combination with the fatty acids formed by oxidation. Of these, valerianic acid largely predominates; and the amount of barium valerianate [Ba2 (C2H3O2)] found is calculated to its equivalent in amylic alcohol. Capsicum, creosote, etc., are isolated by treating the sample with ether or benzole, and testing the odour and taste of the evaporated solutions so prepared.

Creosote gives a blue colour with ferric chloride solution; and the exceedingly pungent vapours evolved upon heating a residue containing capsicum are equally characteristic. The presence of tannin in distilled spirits, which is mostly derived from their preservation in casks, is recognised by the formation of a bluish-black colour upon the addition of ferric solutions. The identification of the various ethylic and amylic ethers used in the preparation of factitious liquors is a matter of some difficulty. Their presence is most readily detected by means of their characteristic odour, which is developed upon adding a little sodium hydroxide to the sample, evaporating the mixture over the water-bath almost to dryness, and then adding a small quantity of sulphuric acid. Another means of ascertaining the nature of the organic ethers present in spirits is to first remove the ethylic alcohol contained by a partial distillation with an alkaline solution, and then acidulate the remaining liquid with sulphuric acid, and repeat the distillation, when the volatile fatty acids originally contained in the ethers will be found in the distillate; their identity is to be established by means of their characteristic properties. Nitrous ether (which compound is not contained in genuine liquors) may be detected by partially distilling the sample and adding a mixture of potassium iodide, starch paste, and acetic acid to the first portion of the distillate, the production of a blue colour indicating its presence. As previously remarked, the exercise of the ordinary senses is frequently of greater value in judging the quality of liquors than the results of chemical tests. Many of the organic ethers employed in the manufacture of artificial liquors are identical with those contained in the genuine article, and it is obvious that, in such instances, no distinction can be made between them.