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RECTIFICATION AND COMPOUNDING OF SPIRITS.
Plain spirit, as produced on the great scale by Coffey's still, or other form of distilling apparatus, although usually of a high strength and of comparative purity, is still contaminated with small portions of essential oil and ethers. The more effectual separation of these substances, together with the manufacture of the purified spirit into gin, brandy, compounds, &c., constitutes the special business of the rectifier or rectifying distiller.
Raw spirit may be greatly improved in quality by simply mixing it with a large volume of water and redistilling it at a low heat, but its purification is further assisted by the use of the crude alkali potash, known in the trade as « grey salts," with the occasional addition of a small quantity of pearl-ash (carbonate of potash), technically termed « white salts." These agerts have the property not only of cleansing the spirit, but also of strengthening it by their affinity for the water present. The quantity generally employed is about 1 lb. of grey salts to every 100 gallons of the spirit. The alkali should first be dissolved in as little water as will effect its solution, and the liquid then rendered clear by filtration. It is a common practice, however, to place the crude alkali, without any preparation, in the still.
As soon as the potash is added distillation is commenced, the first and last portions of the distillate being run, as in the original manufacture of the spirit, into a vessel called the “ feints back," and the purer product into separate vessels according to the strength at which it comes over. The same spirit is frequently subjected to a second and even a third rectification, with, in each case, about half the first quantity of alkali. The feints, or first and last runnings of each operation, are allowed to accumulate until a considerable quantity has been collected, when the whole is distilled, and as much pure spirit as possible separated from them by the usual processes. Having obtained a supply of purified spirit, the rectifier then proceeds to convert portions of it into gin, British brandy, and the various spirituous compounds and cordials common in the trade. In the manufacture of gin, spirit of the first or second rectification is run into a still in which have previously been placed various berries, seeds, roots, or other flavouring matters, and the whole submitted to distillation. By some rectifiers juniper berries are used alone, but, while this is always the preponderating ingredient, & number of other substances is, in most cases, employed as well. These consist chiefly of coriander seeds, carraway seeds, aniseeds, and cardamoms, the roots of calamus aromaticus, angelica, orris, and liquorice, together with orange peel, lemon peel, crushed almond cake, and cassia buds. There is seldom any difference in the nature of the flavouring materials, but the proportions vary at almost every rectifying house. A very slight reduction or increase in the quantity of any one of the substances used will sensibly affect the flavour of the gin. The first and last runnings of the flavoured spirit, being very impure, are conveyed into a feintsback, and the intermediate runnings, according to their strength, into separate vessels. Water is now added to the gin to reduce it to the usual selling strengths, and, if on dilution & turbidity occurs from the precipitation of some of the flavouring oils, the spirit is “ fined” by mixing with it solution of alum or isinglass. In some few cases, the rectifier does not employ a still, but prepares his gin by simply dissolving the essential oils of juniper, aniseed, &c., in the strong spirit procured by him from the distiller, and afterwards reducing the mixture to the customary strength with water. This process is properly speaking, a compounding. But the gin so prepared is of indifferent quality, and is bought only by those with whom a low price is a consideration. The raw spirit may be greatly improved when rectification is not resorted to, merely by passing it through layers of fresh charcoal.
British brandy of the ordinary kind is fabricated by adding to rectified spirit, French wine vinegar, alcoholic extract of prunes, burnt sugar, and a little foreign brandy. Sometimes the liquid procured by distilling spirit with the marc or refuse of the grape press, mixed with argol or crude wine stone, is added to pure spirit, and the colour brought up by the addition of fruit tincture and caramel. The process of compounding is all that is resorted to, as a general rule, in the manufacture of British brandy. Certain rectifiers possess the art of imitating the best French brandy much more successfully than others in the trade. The use of a little ænanstic ether obtained from wine greatly increuses the resemblance to the foreign spirit. In some cases « British brandy" consists of little else than diluted spirit of wine coloured with burnt sugar.
The term “compounds" is very vague, but the substances known by that name are generally understood to consist of spirit to which have been added the juice of fruit, sugar, and various flavouring materials. The appellations applied to the different spirituous mixtures are nearly as numerous and indefinite as the methods of preparing them. It would be useless to single out any particular compound or mixture, and describe the mode of its manufacture as almost every compounder has a process of his own; but it may be mentioned, that a clear thick syrup of white sugar, mixed with from 20 to 30 per cent. of proof spirit, forms the basis of all such liquors. Essential oils, vegetable acids, or sometimes a little fruit tincture, blended with this, will produce the cordials or liqueurs known as “ cloves," peppermint,” aniseed,” « lovage,” &c., &c. No portion of the spirit present is ever generated by fermentation of the saccharine ingredients, as in the case of genuine “ sweets,” or made wines.
By the Act 18 and 19 Vic. c. 37, spirits of wine may be used duty-free in the arts and manufactures, provided it be rendered non-potable by the addition of 10 per cent. of wood naphtha. The latter is a spirit obtained by the destructive distillation of beech, birch, and other hard woods, in the course of the manufacture of acetic or pyroligneous acid. The acid is fixed by adding chalk to the impure products, and the wood spirit is then distilled over by the heat of a water-bath, and again rectified from chalk or hydrate of lime.
Pure wood spirit is a limpid, colourless liquid, having an offensive odour, and disagreeable, burning taste. It has many properties in common with alcohol, and, like it, mixes with water in all proportions, condensation also taking place, and the temperature rising, as in the dilution of alcohol. It is a solvent for gases, oils, resins, gum resins, vegetable alkaloids and deliquescent salts, but in these respects is inferior to vinous alcohol. When used as a solvent for resins-as for instance in dis. solving shellac for the manufacture of hats-it generally leaves behind it some impurity as it evaporates, and its vapour is hurtful to the eyes. Though its boiling point is many degrees below that of alcohol, yet it cannot be separated from that substance by any number of re-distillations. The reason of this is as follows :—the specific gravity of the vapour of wood spirit compared with air, is 1.125, while that of alcohol is 1.6133; the small amount of the vapour of the latter, which distils over, is compensated by its greater weight, and thus the relative proportion between the two is not altered.
In order to procure wood spirit of the requisite quality and strength, it is purchased direct from the manufacturers by the Revenue, and issued under certain regulations to the mixers. In every case a sample of the spirit, as supplied by the manufacturer, is sent to the Revenue Laboratory, where it is tested as to its boiling point, specific gravity, freedom from the grosser oils and other impurities, and as to whether or not it is neutral to test paper, and properly miscible with water.
The alcohol, as well as the naphtha, used for mixing, must not have a less strength than 50 O. P. The wood spirit furnished by the Revenue has a specific gravity varying from .820 to .830, and boils at temperatures ranging from 160° to 1700 F.
Methylated spirit is suited for almost all the purposes to which pure alcohol was formerly applied, and since its introduction many new uses have been found for it. It is extensively employed in the manufacture of chloroform, ether, sweet spirits of nitre, varnishes, and fulminating mercury for percussion caps ; also for the dissolving of shellac, sandarac, and mastic for hatters, oils and fats for lubricating machinery, and the new dyes from coal tar, mauve, magenta, &c., and for the preparation of tinctures for cattle medicines. It is also used for singeing horses and burning in lamps.
Legally, it can be prepared and sold only by licensed persons, but any one except a publican may vend it when it contains an ounce of gum resin dissolved in every gallon, in which state it is denominated « Finish.”
To examine it for resins, it is only necessary to add to the so-called « finish" three or four times its bulk of water, when, if resin has been added, it will assume a milky colour from the precipitation of the gums. If but a faint milkiness ensues, it is evident the spirit does not contain the required amount of gum. This may be more correctly determined by measuring out a hundred grains of the spirit in a graduated vessel-easily procured from any druggist-transferring the quantity to a weighed watch-glass or crucible, and evaporating the spirit over & water-bath until the vessel ceases to lose weight. The residue left in the evaporating vessel is deemed gum or resin, and the amount in a gallon is found by a statement of proportion, a gallon of water weighing 70,000 grains, and an ounce avoirdupoise weighing 437.5 grains.
Of late, attempts have been made on the part of druggists and others to disguise the taste and smell of methylated spirit, by adding to it oil of peppermint, oil of cloves, oil of ginger, or other essential oils. This fraud may be detected by saturating the spirit with warm water, when the oils will rise to the surface, and may be poured off'; the presence of the naphtha will then be rendered evident, and the odour unmistakeably recognised, on rubbing a few drops of the liquid between the hands.
By law, a certain drawback of duty is payable in respect of beer exported from any part of the United Kingdom, either as merchandise or ships' stores. The amount of this drawback is proportional to the quantity of malt or sugar inferred to have been used in the brewing of the beer, and is computed according to the following scale :-For every barrel, or 36 gallons of beer, the specific gravity of which, before fermentation, shall not have been less than 1040°, a drawback of 4s. 3d., and for every additional 5 degrees of specific gravity, from 1040° to 1125° inclusive, a further sum of 6d. per barrel. These rates include an allow. ance of 3d. per barrel for the expense to which the brewer is put in payment of the additional licence duty now chargeable on him, as an equivalent for the abolished duty on hops.
It has been found that, on the average, lı bushels of malt are required to yield a barrel of wort having a density or specific gravity of 1040°, and proportionally, that the use of 10
3.ths of a bushel is necessary for the production of every additional 5 degrees of density per barrel. Now, the duty on 14 bushels of malt amounts to 4s., excluding fractions, which, with the allowance of 3d. for licence duty, gives a drawback of 4s. 3d., corresponding to 1040°, the lowest gravity of the scale. At each interval of 5 degrees, the sum of 6d. is added in repayment of the duty on ths of a bushel of malt. As the basis of a similar calculation, with respect to the sugar used in brewing, it is assumed that 210 lbs. of ordinary brown Muscovado sugar are equivalent to a quarter of malt. But at the present rate of duty on that description of sugar — 128. 8d. per cwt. - it will be seen that the various drawbacks are rather less in amount than the duty chargeable on the sugar supposed to have been consumed in the brewing of beer at the several degrees of gravity.
Before receiving payment of drawback, the brewer or exporter is required to make declaration as to the specific gravity of the worts prior to fermentation, and it is the chief object of the present article to describe how the original specific gravity may be deduced from certain experiments on the finished beer, in order to test the truth of the brewer's declaration.
A similar process is employed in the analysis of distillers' wash, with the object of discovering whether the true original gravity has been declared by the trader. This is occasionally an inquiry of considerable importance in a revenue point of view, as distillers are allowed to mix yeast with their worts and thus to induce fermentation before declaring the gravity, or giving officers an opportunity of testing a sample of the collected worts. It is evident, therefore, that unless some efficient check existed, the usefulness of the “attenuation charge" or estimated produce of the wash, might, to a great extent, be frustrated by untrue declarations of original gravity.
The following description embraces an account of the principles and practice of the one general method prescribed in substance by law, and now applied to both the foregoing purposes.
METHOD OF ASCERTAINING THE “ ORIGINAL GRAVITY
BEER AND DISTILLERS' WASH.*
By the term "original gravity of beer” is meant the density or specific gravity of the unfermented wort from which the beer was produced. This density, which always bears a certain definite relation to the proportions of malt and water used in brewing the wort, can only be directly observed before fermentation has commenced, and afterwards must of necessity be deduced from the results of a combination of experiments having reference to the changes induced in the wort by the action of yeast. Thus the brewer can easily determine the value of his beer by a simple observation of the gravity of the wort; but to arrive at this value by a backward process, that is by an analysis of the finished beer, has, from the complex effects of fermentation, been up to a recent period found very difficult. The great importance of the subject, not only to the Revenue and to the exporters of beer but to brewers generally, led to the suggestion, previous to the year 1847, of several methods for deriving the gravity of the wort from the matured beer. Of these, that of Professor Balling, of Prague, was perhaps the most valuable ; but all, when tested, were found to yield results too erroncous to be relied upon for fiscal purposes.
This want of accuracy in the methods alluded to, is no doubt partly the result of their being framed on a too limited number of experiments, and partly of their being derived from calculations by general formulæ based upon the erroneous assumption, that the data obtained from experiment were always in a constant ratio to the original gravities of the beers, thus overlooking certain apparent anomalies which are consequent upon fermentation, and taking it for granted that all the saccharine matter originally present in the wort, wbich did not produce alcohol, remained in the beer, unaltered either in character or in specific gravity.+
The Board of Excise, fearing that the Revenue might be greatly defrauded by exporters of beer making false declarations, and thus obtaining a higher rate of drawback than the strength of the beer entitled them to, had long been anxious to possess some means by which they could check such declarations, when, in 1842, Mr. Stevenson, mathematical instrument maker, of Edinburgh, submitted to them a method similar to that of Balling, for ascertaining original gravities, which was at once referred to the late Dr. Thomas Thomson, of Glasgow, who, after a careful and extended investigation, reported that it was inaccurate in its results and totally unfit for Revenue purposes. Upon this, the Board directed Messrs. Dobson and Phillips, two of their superior oflicers, to turn their attention to the subject. These gentlemen, who from their scientific and practical knowledge of brewing and fermentation were eminently qualified to undertake the inquiry, soon arrived at the conclusion that any process for ascertaining accurately the original gravities of beers must be founded entirely upon empirical data derived from a great nuraber of experiments made upon worts of various densities, brewed on a considerable scale, and under precisely the same conditions as those observed by practical brewers, the experiments to be made upon such worts at short intervals, during the whole
• The greater portion of this article so far as relates to the originai gravity of beer, is taken in substance from a paper on the subject contributed by Mr. Kay, of the Inland Revenue Laboratory, to the Engineer, and which appeared in the numbers of that Journal, for March 13 and March 20, 1857
| See " Manufacture of Spirit," (page 285.)