Chapter C: W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the (6)

_Hist., &c._ Although the art of distillation was probably known at a comparatively early age of the world, the preparation of pure rectified spirit is a discovery of modern times. It was not until the 13th century that Raymond Lully first showed the way to concentrate spirit by means of carbonate of potash; after which date pure concentrated spirit gradually rose into note as an article of trade and commerce in Europe. In the 16th century its distillation was in common practice in these countries. (Burns.) By means of chloride of calcium, Dr Black obtained alcohol of sp. gr. 0·800 (about A.D. 1760); and Richter afterwards procured it of a sp. gr. so low as 0·796 at 60° Fahr. (Crell's 'Annals,' 1796.) Lavoisier first demonstrated the composition of alcohol (about 1780). Its analysis was subsequently perfected by M. Saussure, jun., and confirmed by MM. Dumas and Boullay, and Gay-Lussac; and by many others since.

_Nat. Hist._ Alcohol is peculiar to the organic kingdom, being exclusively produced, in the natural way, by the process of fermentation.

_Sources, &c._ Dilute alcohol may be procured, by the ordinary process of distillation, from all fermented liquors. When drawn from wine (as in France), it constitutes BRANDY; when from the refuse juice of the sugar-cane, it is called RUM; when from malt, grain, or molasses (as in England), it is called MALT, RAW-GRAIN or MOLASSES SPIRIT; and when from rice or palm-wine, ARRACK. Brandy, rum, Hollands, and whisky, contain only about half their volume of alcohol; and gin much less. When distilled from any of these spirituous liquors, the alcohol contains, besides water, variable quantities of essential oils, ethers, and other flavouring matters, which, by one or more redistillations with charcoal or lime, it for the most part loses, and then becomes commercial spirit of wine. By a further rectification from chloride of calcium, lime, carbonate of potash, or any other substance having a strong affinity for water, the water is retained, and a strong spirit passes over containing not more than 10 per cent. of water. By repeating the process, and using the proper precautions, it may be obtained almost entirely free from water, and is then called absolute or anhydrous alcohol.

_Preparation I._ Of _Absolute Alcohol_:--

_a._ Alcohol (highly rectified spirit), of 85% (sp. gr. ·835 to ·822), is mixed, in a tubulated retort, with about half its weight of fresh-burnt quick-lime, in coarse powder; and the whole, after securely stopping the neck with a cork, and agitation, is allowed to repose for several days. The alcohol is then carefully distilled off, drop by drop, by the heat of a water bath, until the weight of the distillate nearly equals that of the 'anhydrous alcohol' in the spirit operated on. The sp. gr. of the product should be ·795 or ·796; but by carefully repeating the process with the distillate and a fresh quantity of lime, and prolonging the last digestion with the latter for several weeks, absolute alcohol of the sp. gr. ·79381 at 60° Fahr. may be easily obtained.

_b._ (Drinkwater; Fownes.) The strongest rectified spirit of wine is digested in a stoppered bottle for several days, with about half its weight of anhydrous carbonate of potash, in powder, frequent agitation being had recourse to; the alcohol, after repose, is then decanted, and treated with sufficient fresh-burnt quick-lime to absorb the whole of the spirit. After 48 hours' digestion, the spirit, when distilled, will have the sp. gr. ·793 at 60° Fahr.

_c._ (Liebig; Ure.) Alcohol of about 90% is saturated with fused chloride of calcium, in powder, and after repose for a few hours in a stoppered bottle, is submitted to distillation as before. The product should nearly equal the quantity of dry alcohol in the sample. Ure recommends equal weights of the spirit and chloride to be taken; and the process to be stopped as soon as about half the volume of the spirit employed has passed over, or the distillate acquires a higher sp. gr. than ·791 at 68°, or ·796 at 60° Fahr.

_d._ (B. P. 1867.) Take of rectified spirit, 1 pint; carbonate of potash, 1-1/2 ounce; slaked lime, 10 ounces. Put the carbonate of potash and spirit into a stoppered bottle and allow them to remain in contact for two days, frequently shaking the bottle. Expose the slaked lime to a red heat in a covered crucible for half an hour, then remove it from the fire, and, when it has cooled, immediately put the lime into a flask or retort, and add to it the spirit from which the denser aqueous solution of carbonate of potash, which will have formed a distinct stratum at the bottom of the bottle, has been carefully and completely separated. Attach a condenser to the apparatus, and allow it to remain without any external application of heat for twenty-four hours; then applying a gentle heat, let the spirit distil until that which has passed over shall measure 1-1/2 fluid ounce; reject this, and continue the distillation into a fresh receiver until nothing more passes at a temperature of 200° Fahr.

_e._ (Poggendorff.) Saturate alcohol with caustic potash, then add half its volume of water, and distil at a low temperature.

II. Of _Hydrated_ or _Commercial Alcohol_:--

_a._ (ALCOHOL, Ph. L. 1836.) Take of rectified spirit (sp. gr. 0·838), 1 gal.; chloride of calcium, 1 lb.; proceed as above, and distil 7 pints and 5 fl. oz. Sp. gr. of product 0·815. It contains about 7% of water, by weight, and 5% by volume.

_b._ (ALCOHOL, Ph. D. 1826.) Rectified spirit, 1 gal.; pearl-ashes (dried and still hot), 3-1/2 lbs.; mix, digest in a covered vessel, with frequent agitation, for seven days; then decant the clear portion, and add to it of chloride of calcium, 1 lb.; agitate to effect solution, and distil off the spirit until the mixture in the retort begins to thicken. Sp. gr. of product 0·810. It contains about 5% of water, by weight.

_c._ (Without distillation.) Rectified spirit is agitated, in a closed vessel, with anhydrous carbonate of potash (prepared by heating the salt to redness, and still slightly warm), until the powder sinks to the bottom undissolved; the carbonate is then added in considerable excess, and the agitation repeated at short intervals for some hours or even days; lastly, after sufficient repose, the clear upper portion is decanted.--_Obs._ If a clean spirit, and pure carbonate of potash (or at least one perfectly free from caustic potash or any other impurity soluble in strong spirit), be used, an alcohol sufficiently pure and free from water for many common purposes may be thus obtained; otherwise the product contains a little potassa, &c., which can only be removed by distillation. For some purposes, however, this would not be objectionable. Sp. gr. about ·812.

_A_, A bottle with two necks, the upper furnished with a
ground-glass stopper.
_B_, Loop of cord to hang the apparatus up by.
_C_, Bladder, containing spirit, filled by means of the bottle
_A_.
_D_, Neck of bladder accurately secured to the under neck of the
bottle _A_.]

III. (Soëmmering.--VARNISH-MAKER'S ALCOHOL.) The bladder of an ox or calf, thoroughly cleansed from fat, and washed and dried, is nearly filled with rectified spirit, and then securely fastened and suspended in any dry situation, at a temperature of about 122° Fahr. In from six to twelve hours, when the heat is properly maintained, the spirit is generally sufficiently concentrated, and in a little time longer is rendered nearly free from water (anhydrous), or of the strength of 96 to 98%.--_Obs._ The same bladder will serve for more than one hundred operations. If not kept very nearly full, a portion of the spirit escapes through the empty part. To prevent this accident, a bottle with a double neck, of the shape represented in the _engr._, may be employed; by which means the bladder may be kept constantly full during the process. After the first or second time of using, the bladder gives alcohol sufficiently pure for all ordinary purposes. Before hanging the apparatus up, it is better to enclose it in a coarse potato-netting, to prevent any accident arising from the strain on the neck of the bladder. Soëmmering recommends both the inside and outside of the dry bladder to be smeared over 2 or 3 times with a strong solution of isinglass; but this is not necessary to the success of the process.

IV. _Rectified Spirit._ (B. P. 1867.) _Spiritus Rectificatus._ Alcohol with 16 per cent. of water; obtained by the distilling of fermented saccharine fluids. Sp. gr. 0·838.

V. _Proof Spirit._ (B. P. 1867.) _Spiritus Tenuior._ Take of rectified spirit, 5 pints; distilled water, 3 pints. Mix. Sp. gr. of product 0·920.

_Prop. of Alcohol._ Light, transparent, colourless; highly volatile and inflammable, burning with a pale blue and smokeless flame; very mobile; odour, agreeable; taste, strong and pungent; miscible in all proportions with water, with the evolution of heat, and temporary expansion, but ultimate condensation of the mixture, some hours elapsing before the union is complete, and the normal temperature restored. The mixture has a higher sp. gr. than the mean of its constituents; and this is greatest when 54 vols. of alcohol are mixed with 49·77 vols. of water, the resulting compound measuring only 100 volumes. It absorbs water from moist air; dissolves resins, essential oils, camphor, bitumen, soaps, sugar, carbonic and boracic acid, iodine and the iodides, lime, ammonia, soda, potash, the alkaloids, wax and spermaceti (when boiling), all the deliquescent salts (except carbonate of potassa), and various other substances. It curdles milk, coagulates albumen, and (in quantity) separates both starch and gum from their mucilages. It boils, in the air, at 173° Fahr., when in the anhydrous state. When diluted with water its boiling point rises in proportion to the amount of water added. It boils, in vacuo, at 56° Fahr. Every volume of boiling alcohol yields 488·3 vols. of vapour at 212° Fahr. Its sp. gr. is 0·793811 at 60° Fahr., that of its vapour being 1·6133. It has never been frozen; when cooled to -166° Fahr., it acquired the consistence of castor oil, but did not solidify. It contracts by cold; between -15° and +99° Fahr., this occurs with great regularity, at the rate of ·00047 part of its volume for every degree of the thermometer. Its evaporation, like that of ether, produces intense cold. The products of its combustion are carbonic anhydride and water. It acts as a powerful antiseptic on organic substances immersed in it, and is in consequence extensively employed in the preservation of anatomical preparations. With the acids it forms ethers.

_Phys. eff._ Alcohol is a narcotico-acrid poison. In small doses it occasions excitement and intoxication; in larger ones, delirium, somnolency, coma, apoplexy, and death. It acts as a violent nervous stimulant, and, by abstracting water from the soft tissues of the stomach and primæ viæ, destroys their organisation. It is alike poisonous to all animals;--2 drs. will kill a dog. All strong spirits act in the same way, the effect being proportionate to the state of concentration and the quantity taken. On plants it acts as a rapid and fatal poison.

_Ant., &c._ Copious internal use of tepid water, with cold affusions to the head and spine, and injection of cold water into the ears. In the absence of vomiting, a strong emetic should be given, or the stomach-pump used. Ammonia may be used as a stimulant, and, added to water just in sufficient quantity to flavour it, is one of the best antidotes. The head should be kept elevated, and bleeding had recourse to, if cerebral congestion threatens.

_Tests in cases of death._ 1. The odour of the contents of the stomach and ejected matters, and their ready inflammability. 2. The spirit may be separated by digestion with water, filtration, the addition of carbonate of potash, and distillation.

_Comp., &c._ Its per-centage composition is--

Dumas and Brande and Ure. sp.
Boullay. Ure. gr. 0·812.
Carbon 52·37 52·18 47·85
Hydrogen 13·01 13·04 12·24
Oxygen 34·61 34·78 39·91
------- -------- --------
99·99 100·00 100·00

This nearly represents 2 equivalents of carbon, 3 eq. of hydrogen, and 1 of oxygen. The atom of alcohol is now regarded as a multiple of these numbers, and formed by the breaking up of one atom of grape sugar (C_{13}H_{28}O_{11}) into 4 eq. of alcohol, 8 eq. of carbonic acid, and 4 eq. of water. It was formerly regarded as a compound of 1 eq. of olefiant gas, and 1 eq. of water; but it is now generally viewed as HYDRATE OF THE OXIDE OF ETHYLE (C_{2}H_{5}.HO), or a compound of ethylene and water (C_{2}H_{4}.H_{2}O). Grape sugar alone yields alcohol; cane sugar, before it undergoes the vinous fermentation, being first converted into this substance by contact with the ferment.

_Purity._ The presence of water is shown by the specific gravity (see ALCOHOLOMETRY); the absence of other foreign matter by the following tests:--

1. Its colour and transparency is not affected by the addition of a little colourless oil of vitriol (Liebig), or by a solution of nitrate of silver, and subsequent exposure for some time to solar light (Vögel), unless either essential oil or organic matter be present, when it assumes a reddish tinge. 2. It should be neutral to test-papers, colourless, leave no residue on evaporation, and be miscible, in all proportions, with water and with ether. 3. Its boiling point should never be less than 170° Fahr.; a lower temperature suggests the presence of wood spirits, or acetone, or one of the ethers. To detect wood spirit (wood naphtha) see Nessler's Test. For the reverse of this adulteration--the evasion of the duty by the introduction of spirit, under the disguise of naphtha, turpentine, &c.--see those articles.

4. The presence of water in alcohol may be detected, not only by the sp. gr., but also by white anhydrous sulphate of copper burning blue when dropped into it. 5. Potassium placed on alcohol does not take fire, unless a considerable per-centage of water be present.

_Tests, &c._ 1. It may generally be recognised by its volatility, inflammability, odour, taste, miscibility with water, power of dissolving camphor and resins, and other qualities already described. 2. If a few fibres of asbestos be 'moistened' with a saturated solution of bichromate of potash in oil of vitriol, and exposed to the smallest possible portion of hot alcohol vapour, it is almost instantly turned green, owing to the formation of oxide of chromium. In practice, the asbestos may be inserted in the neck of a retort, or even of a bulbed glass-tube containing a few drops of the suspected solution, when the effect occurs as soon as distillation commences. Ether and pyroxylic spirit produce a nearly similar result; but the 'first' of these is distinguished from alcohol by its not being miscible with water in all proportions; and the 'other' by Nessler's Test; whilst both may be readily distinguished by their peculiar and characteristic odour. 3. Dissolve 3 pts. crystallised carbonate of soda in 10 pts. water. To this solution add 1 pt. of liquid to be tested, and heat to about 160° Fahr. Lastly, add iodine in small pieces, till it has entirely dissolved, and the liquid has become colourless. If alcohol be present, iodoform will make its appearance on cooling, and sink to the bottom in the form of a yellow powder. As a similar result is obtained with wood spirit, this must be proved to be absent before applying this test.

The only reliable method of proving that a sample is ethylic alcohol is the production of ether, by acting on the suspected liquid with sulphuric acid. See ETHER.

_Uses._ In the _arts_, alcohol is used by the varnish-maker to dissolve resins; by the perfumer, to extract the odour of plants, and dissolve essential oils, soaps, and other similar substances; by the pharmaceutist, to prepare tinctures and other valuable medicinals; by the instrument-maker, to fill the bulbs of thermometers required to measure extreme degrees of cold; by the photographer, in the preparation of collodion; by the chemist, in analysis, and in the manufacture of numerous preparations; by the anatomist and naturalist, as an antiseptic; and by the physician, for various purposes and applications as a remedy. It is also frequently burnt in lamps, and in parts of the world where it is inexpensive, it is employed in the manufacture of vinegar. Its uses, when dilute, as in the 'spirituous liquors' of commerce, are well known. In medicine, it is employed both concentrated ('alcohol,' 'rectified spirit') and dilute ('proof spirit,' 'brandy,' 'gin,' &c.), as a caustic, irritant, stimulant, tonic, &c. It has also been used in a multitude of other cases, and has been applied to an almost infinite variety of other purposes.

_Gen. commentary._ The selection of any one of the processes given above for the preparation of alcohol must greatly depend on the convenience or position of the operator. Chloride of calcium, and quick-lime, from their powerful affinity for water, and easy application, are the hygrometric substances most generally employed; but the processes involving the use of the other substances and methods already noticed, have all of them advantages under particular circumstances. Gay-Lussac has recommended the use of caustic baryta instead of lime; and others have employed dry alumina, as an absorbent of the water prior to distillation. Common proof spirit may be concentrated until its sp. gr. falls to about 0·825, by simple distillation in a water bath; at which sp. gr. it contains only about 11% of water, by weight, and is then nearly as volatile as pure alcohol.

A convenient apparatus for the preparation of alcohol, on the small scale, is that figured in the _engr._, and which will be self-explanatory to every one competent to use it. The tank (_i_) should be supplied with ice-cold water; and the receiver (_g_) should be covered with cloths kept continually wet with water of the same temperature. The capsule or basin (_c_) is a water bath heated by the little gas furnace (_d_). On the large scale, for commercial alcohol, a copper still, fitted with a glass refrigeratory and receiver, is commonly employed.

By surrounding the capital of a still, or other like apparatus, by a water bath kept at the proper temperature, the alcoholic richness or content of the product may be regulated to the greatest nicety, for any desired strength.

The different statements of chemical authors as to the boiling point, specific gravity, &c., of alcohol, already noticed, may be referred to their having either experimented with samples which have not been absolutely anhydrous, or to their not having made the proper corrections for temperature, and for the different materials of which their vessels and instruments were composed--some probably having been made of glass, and others of brass or some other metal. In some instances the differences are more apparent than real, as in the _Tables_ by Tralles and Lowitz; in the former of which water, at its lowest sp. gr., is taken as the standard. Until recently, the only known source of alcohol was the fermentation of saccharine solutions. Its production by synthesis, though often attempted, is, however, erroneously said to have always failed. It had long been employed as an occasional source of bicarburetted hydrogen (olefiant gas) at a high temperature; but M. Berthelot succeeded in reproducing it, from bicarburetted hydrogen, by agitating the latter, in a closed vessel, with sulphuric acid and metallic mercury ('Journ. de Chimie Med.,' 1855, p. 175); and Henry Flennel, nearly thirty years before M. Berthelot's discovery, found that pure olefiant gas is absorbed by agitation with concentrated sulphuric acid, with the formation of sulphovinic acid, and that by subsequent dilution with water, and distillation, alcohol passes over into the receiver.

=ALCOHOLATE.= _Syn._ ALCOHATE; ALCOHOLAS, L. A salt in which alcohol appears to replace the water of crystallisation, as is the case with certain chlorides, nitrates, &c. Some of them may be formed by simple solution and crystallisation of the salt in alcohol. (Graham.) They are all very unstable, being readily decomposed by water.

=ALCOHOLIC.= _Syn._ ALCOHOLICUS, L.; ALCOHOLIQUE, &c., Fr.; ALKOHOLISCH, Ger. Pertaining to, containing, of the nature of, or made with, alcohol.

=ALCOHOLICA.= [L.] _Syn._ ALCOÖLIQUES, Fr.; WEINGEIST-VERBINDUNGEN, Ger. In _pharmacy_, liquids containing, or preparations made with, alcohol, as a characteristic ingredient.

=ALCOHOLISATION.= [Eng., Fr.] _Syn._ ALCOHOLISATIO, L.; ALCOÖLISATION, &c., Fr.; ALKOHOLISERUNG, Ger. In _chem._ and _pharm._, the development of the characteristic properties of alcohol in a liquid, or the use of it either as an addition or a menstruum; also the act or process of obtaining alcohol from spirit by rectification.

=ALCOHOLOM'ETER= (-l[)o]m'-). _Syn._ ALCOHOL'METER (h[)o]l'-; -h[)o]m'-[double-dagger]); ALCOHOLOMÉTRUM, L.; ALCOÖLOMÈTRE, ALCOÖMÈTRE, ALCOHOLMÈTRE, &c., Fr. An instrument or apparatus used in alcoholometry. Alcoholometers are simply 'hydrometers' adapted to the densities of alcohol, either concentrated or dilute. Some of these, as BAUMÉ'S, CARTER'S, &c., merely indicate the number of degrees corresponding to the state of concentration of the liquid. Others, of a like construction, as those of RICHTER (_a_), TRALLES (_b_), and GAY-LUSSAC (_c_), have their stems so graduated as at once to indicate the proportion per cent. of alcohol present, either by weight, or by volume, at some standard temperature. (See _engr._) A third class, as those of the Abbé BROSSARD-VIDAL, FIELD, &c. are essentially thermometers, with scales which indicate the boiling points of spirits of different strengths, instead of the common thermometric degrees; whilst to a fourth class belong the alcoholometer of M. SILBERMANN, which is based upon the known rate of expansion of alcoholic liquors by heat, expressed in alcoholometric degrees; and that of M. GEISSLER, which depends on the measurement of the tension of the vapour of the liquid, as indicated by the height to which it raises a small column of mercury. In SYKE'S HYDROMETER, used by officers of the Revenue, the scale of the instrument is enormously extended by the use of movable weights, with each of which it becomes, in fact, a separate instrument, adapted to a certain range of specific gravities.

A very convenient alcoholometer for ordinary purposes (_d_) has been lately produced by some of the instrument makers. It is of the usual form, but its stem on one side exhibits the per-centage richness of the sample in alcohol by volume; and on the other, the per-centage by weight. Thus, both results may be obtained at one trial. This instrument is sometimes called RICHTER'S ALCOHOLOMETER, in England. A further improvement, still more recently introduced, is a similar 'double-scale' instrument, showing the degrees of Sykes on one side, and carrying a small spirit-thermometer in the bulb, to which a scale is fixed ranging from 35° to 82° Fahr.

=ALCOHOLOM'ETRY.= _Syn._ ALCOHOL'METRY (-h[)o]l'-; -h[)o]m'-[double-dagger]); SPIRIT TESTING[double-dagger]; ALCOHOLME'TRIA, L.; ALCOÖLOMÉTRIE, ALCOÖMÉTRIE, &c., Fr. In _chemistry_, the art or process of ascertaining the richness of spirits in alcohol. In _commerce_, the determination of the quantity of spirit of a certain strength, taken as a standard, present in any given sample of spirituous or fermented liquors. In England, this standard is called "proof spirit."

_Hist., &c._ The great importance of being able accurately to determine the strength of spirits in the United Kingdom, on account of the high duties levied on them, has induced the Government authorities, at various times, to investigate the subject. In 1790, the matter was referred to Sir C. Blagden, then Secretary to the Royal Society, who instituted an extensive series of experiments to determine the real specific gravities of different mixtures of alcohol and water. The results of his labours and researches were put forward, with 'Gilpin's Tables,' in 1794, but no practical measures appear to have been taken in consequence. In 1832 a committee of the Royal Society, at the request of the Lords of the Treasury, examined into the accuracy of the Tables, and the construction and application of the instrument (SYKE'S HYDROMETER) now used by the Revenue officers, on which they reported favorably, and declared that they were sufficiently perfect for all practical and scientific purposes. The errors introduced into calculations of the strength of spirits by these tables were found to be quite unimportant in practice, and did not, in any one instance, amount to unity in the fourth place of decimals. This method adapts the specific gravity as the test of the strength of spirits, and is founded on the fact that alcohol is considerably lighter than water, and that (with proper corrections for condensation and temperature) the sp. gr. regularly increases, or decreases, according to the relative proportions in which the two are mixed.

Several other methods of alcoholometry have been proposed, founded upon--the variations in temperature of the vapour of alcohol of different strengths--the heat involved by its admixture with water--its dilatation by heat--the tension of its vapour--the insolubility of carbonate of potash in alcohol--its volatility, boiling point, &c. &c., the more important and useful of which are noticed further on. The method adopted by the Boards of Inland Revenue and Customs is, however, the one which is almost exclusively employed in trade and commerce in Great Britain, not only on account of its simplicity and correctness, but for the purpose of the results exactly coinciding with the results obtained by the Revenue officers.

METHODS OF ALCOHOLOMETRY.

1. _Methods based_ on the _specific gravity_, or _per-centage strength_, by VOLUME:--

_a._ With SYKES' HYDROMETER. _Revenue system._ The _engraving_ below represents Sykes' hydrometer, as made by Mr Bate, under the directions of the Commissioners of Inland Revenue and Customs. It consists of a spherical ball or float, with an upper and lower stem, and is made of brass, which (in the more expensive instruments) is usually coated with gold, to prevent corrosion from damp, and the acidity so generally present in spirituous liquors. The upper stem (A) is about four inches long, and is divided into ten parts, each of which contains five subdivisions. There are nine movable weights of the form _b_, of different sizes, numbered respectively 10, 20, 30, &c., to 90, each of which represents so many of the principal divisions of the stem, as its number indicates. In use, one of these weights is slipped on to the lower stems; and thus, by means of them, the instrument acquires a range of above 500 divisions, or degrees, extending from the Revenue 'standard alcohol' (sp. gr. ·825) to water. It is so formed as to give the sp. gr. with almost perfect accuracy, at 62° Fahr. When loaded with the weight 60 it sinks in proof spirit to the line marked (P) on the narrow edge of the stem at 51° Fahr.; and, by further placing the square weight or cap (also supplied with the instr.) on the top of the upper stem, it floats exactly at the same point in distilled water. This weight or cap is found to weigh 43·66 grs., which is practically 1-12th of the total observed weight of the instrument, and its poise 60, and hence shows the difference between the gravity of proof spirit and water, as explained hereafter. The whole is fitted up in a neat mahogany case, accompanied with a thermometer, and a book of tables containing corrections for temperature, &c.--_Process._ A glass tube of the form of fig. _B_ is filled to about the mark (_a_) with the sample for examination; the thermometer is then placed in the liquor, and stirred about for two or three minutes (observing not to breathe upon the glass, nor hold it in the hand), and the temperature noted. The hydrometer is next immersed in a similar manner, and gently pressed down in the liquor to the 0 on the stem with the finger; it having been previously loaded with any one of the nine weights that will cause it to float with the surface of the spirit at some point on the graduated part of the scale. The indication at the point cut by the surface of the liquor, as seen from below, added to the number of the weight with which the float is loaded, gives a number which must be sought in the hook of Tables, which is always sold with the instrument. In this book, at the page headed "Temperature as observed by the Thermometer," and against the part of the column appropriated to the given indication (weight), will be found the strength per cent., expressed in degrees over or under proof, by VOLUME, in whole numbers or decimal parts. In reading off the indication, to ensure accuracy, it is necessary to allow for the convexity of the liquor at the part where it immediately rests against the stem.

_Obs._ In an instrument requiring so much care and skill in its manufacture the purchaser should be careful to procure a perfect one. A very slight blow, friction from continual wiping with a rough cloth, and other apparently trivial causes, tend to injure so delicate an instrument. The shape of the weights occasionally vary; some being intended to be attached to the hydrometer at the bottom of the spindle, and others to rest on its top. The first plan is, perhaps, the best, as it tends to make the instrument float with greater steadiness in the liquor; but, at the same time, it renders its adjustment by the maker a matter of greater difficulty.

In employing this instrument, the Revenue officers are instructed to take the nearest degree above the surface of the mercury, when it stands between any two degrees of the thermometer; and the division on the scale of the hydrometer next below the surface of the liquid, when it cuts the stem between any two lines; thus giving the difference in favour of the trader in both cases.

By means of the _Table_ at page 64 the hydrometer indication, or the degrees over or under proof, of the Revenue system, may be converted into 'real specific gravities,' by mere inspection; and the corresponding 'per-centage richness' in alcohol of any sample may be found, either by WEIGHT or VOLUME.

The specific gravities in this table are such as, on being referred to Gilpin's Tables, will give the expressions of proof strength answering to the whole indications of the Revenue hydrometer. Intermediate values at fifths of indications may be had by taking proportional differences between the nearest tabular numbers. Thus, to find the specific gravity that should stand opposite to Indication 70·6, we first obtain the difference between the densities standing in a line with Indications 70 and 71 respectively, and then say, as 1 : 0·6 :: ·00192. 00·115, and ·94135 + ·00115 = ·94250, the specific gravity required.

_b._ With GLASS ALCOHOLOMETERS. That of Tralles, and most others of a like description (as made in England), gave the per-centage strength, by VOLUME, with tolerable accuracy, at the standard temperature of 60° Fahr. Gay-Lussac's ALCOÖMETRE, which closely resembles that of Tralles, is adjusted for the temperature of 59° Fahr. (15° Cent.). All of these, to give at once accurate results, must, of course, be employed at the 'normal temperature' of the instrument. As, however, in practice, the experiment cannot be conveniently performed at any 'fixed' temperature but only at that of the atmosphere, it is obvious that certain corrections are constantly required in order to obtain results of any value. Perfect accuracy requires that table for every variation of the thermometer, founded on actual experiments, should accompany each instrument; as, without them, tedious and difficult calculations are necessary, which, in the hurry of the cellar and laboratory, or by persons inexpert at figures, are not easily performed. A series of such Tables were prepared by Gay-Lussac, and, with his instrument, are those which are almost exclusively used in France. For rough purposes, in the absence of Tables or nicer calculations, it may be useful to know that, for commercial spirits, at ordinary temperatures, a variation of--

By VOLUME,
5° Fahr. is equal } 1·00% of Alcohol; } 1·794% of Proof
to (about) } or (about) } spirit.
1° " " 0·20% " 0·359% "
5° Cent. " 1·80% " 3·229% "
1° " " 0·36% " 0·646% "

By WEIGHT,
5° Fahr. is equal } 0·80% of Alcohol; } 1·62% "
to (about) } or (about) }
1° " " ·16% " ·32% "
5° Cent. " 1·43% " 2·9% "
1° " " ·28% " ·58% "

TABLE I.--_Showing the Densities and Values of Spirits
at 60° Fahr., corresponding to every Indication of
Sykes' Hydrometer._

+-----------+---------+----------+--------------------+
| | | | Per Cents. of |
| Sykes' | | | Absolute Alcohol. |
|Hydrometer |Strength | Specific +----------+---------+
|Indication.|per cent.| Gravity. | By | By |
| | | | Measure. | Weight. |
+-----------+---------+----------+----------+---------+
| | O.P. | | | |
| 0 | 67·0 | ·81520 | 95·28 | 92·78 |
| 1 | 66·1 | ·81715 | 94·78 | 92·08 |
| 2 | 65·3 | ·81889 | 94·31 | 91·42 |
| 3 | 64·5 | ·82061 | 93·84 | 90·78 |
| 4 | 63·6 | ·82251 | 93·33 | 90·07 |
| 5 | 62·7 | ·82441 | 92·80 | 89·36 |
| 6 | 61·8 | ·82622 | 92·29 | 88·67 |
| 7 | 60·9 | ·82800 | 91·77 | 87·99 |
| 8 | 60·0 | ·82978 | 91·25 | 87·30 |
| 9 | 59·1 | ·83151 | 90·74 | 86·63 |
| 10 | 58·2 | ·83323 | 90·23 | 85·96 |
| 11 | 57·3 | ·83494 | 89·72 | 85·30 |
| 12 | 56·4 | ·83661 | 89·21 | 84·65 |
| 13 | 55·5 | ·83827 | 88·70 | 84·00 |
| 14 | 54·6 | ·83993 | 88·17 | 83·33 |
| 15 | 53·7 | ·84153 | 87·67 | 82·70 |
| 16 | 52·7 | ·84331 | 87·10 | 81·99 |
| 17 | 51·7 | ·84509 | 86·51 | 81·26 |
| 18 | 50·7 | ·84680 | 85·95 | 80·58 |
| 19 | 49·7 | ·84851 | 85·39 | 79·89 |
| 20 | 48·7 | ·85022 | 84·81 | 79·19 |
| 21 | 47·6 | ·85205 | 84·19 | 78·44 |
| 22 | 46·6 | ·85372 | 83·61 | 77·74 |
| 23 | 45·6 | ·85537 | 83·04 | 77·07 |
| 24 | 44·6 | ·85700 | 82·47 | 76·39 |
| 25 | 43·5 | ·85878 | 81·85 | 75·66 |
| 26 | 42·4 | ·86055 | 81·21 | 74·92 |
| 27 | 41·3 | ·86229 | 80·59 | 74·19 |
| 28 | 40·2 | ·86402 | 79·97 | 73·47 |
| 29 | 39·1 | ·86574 | 79·34 | 72·75 |
| 30 | 38·0 | ·86745 | 78·71 | 72·03 |
| 31 | 36·9 | ·86915 | 78·08 | 71·32 |
| 32 | 35·7 | ·87099 | 77·40 | 70·54 |
| 33 | 34·5 | ·87282 | 76·71 | 69·77 |
| 34 | 33·4 | ·87450 | 76·08 | 69·06 |
| 35 | 32·2 | ·87627 | 75·41 | 68·32 |
| 36 | 31·0 | ·87809 | 74·72 | 67·55 |
| 37 | 29·8 | ·87988 | 74·03 | 66·79 |
| 38 | 28·5 | ·88179 | 73·29 | 65·98 |
| 39 | 27·3 | ·88355 | 72·60 | 65·23 |
| 40 | 26·0 | ·88544 | 71·86 | 64·43 |
| 41 | 24·8 | ·88716 | 71·17 | 63·68 |
| 42 | 23·5 | ·88901 | 70·43 | 62·89 |
| 43 | 22·2 | ·89086 | 69·69 | 62·10 |
| 44 | 20·9 | ·89268 | 68·95 | 61·32 |
| 45 | 19·6 | ·89451 | 68·21 | 60·53 |
| 46 | 18·3 | ·89629 | 67·47 | 59·76 |
| 47 | 16·9 | ·89822 | 66·67 | 58·92 |
| 48 | 15·6 | ·89997 | 65·93 | 58·15 |
| 49 | 14·2 | ·90182 | 65·14 | 57·34 |
| 50 | 12·8 | ·90367 | 64·34 | 56·52 |
| 51 | 11·4 | ·90551 | 63·54 | 55·70 |
| 52 | 10·0 | ·90732 | 62·74 | 54·89 |
| 53 | 8·6 | ·90913 | 61·94 | 54·09 |
| 54 | 7·1 | ·91107 | 61·09 | 53·23 |
| 55 | 5·6 | ·91299 | 60·24 | 52·38 |
| 56 | 4·2 | ·91479 | 59·43 | 51·57 |
| 57 | 2·7 | ·91666 | 58·58 | 50·73 |
| 58 | 1·3 | ·91839 | 57·78 | 49·94 |
| | U.P. | | | |
| 59 | 0·3 | ·92037 | 56·86 | 49·04 |
| 60 | 1·9 | ·92228 | 55·96 | 48·17 |
| 61 | 3·4 | ·92408 | 55·10 | 47·33 |
| 62 | 5·0 | ·92597 | 54·19 | 46·46 |
| 63 | 6·7 | ·92798 | 53·22 | 45·53 |
| 64 | 8·3 | ·92984 | 52·30 | 44·65 |
| 65 | 10·0 | ·93176 | 51·36 | 43·76 |
| 66 | 11·7 | ·93367 | 50·39 | 42·84 |
| 67 | 13·5 | ·93586 | 49·34 | 41·86 |
| 68 | 15·3 | ·93758 | 48·31 | 40·90 |
| 69 | 17·1 | ·93949 | 47·29 | 39·96 |
| 70 | 18·9 | ·94135 | 46·29 | 39·04 |
| 71 | 20·8 | ·94327 | 45·20 | 38·04 |
| 72 | 22·7 | ·94518 | 44·09 | 37·03 |
| 73 | 24·7 | ·94709 | 42·96 | 36·01 |
| 74 | 26·7 | ·94899 | 41·82 | 34·98 |
| 75 | 28·8 | ·95092 | 40·63 | 33·92 |
| 76 | 31·0 | ·95288 | 39·40 | 32·82 |
| 77 | 33·2 | ·95484 | 38·10 | 31·68 |
| 78 | 35·6 | ·95677 | 36·76 | 30·50 |
| 79 | 38·1 | ·95877 | 35·32 | 29·24 |
| 80 | 40·6 | ·96068 | 33·90 | 28·01 |
| 81 | 43·3 | ·96259 | 32·41 | 26·73 |
| 82 | 46·1 | ·96457 | 30·77 | 25·32 |
| 83 | 49·1 | ·96651 | 29·08 | 23·88 |
| 84 | 52·2 | ·96846 | 27·31 | 22·38 |
| 85 | 55·5 | ·97049 | 25·39 | 20·77 |
| 86 | 59·0 | ·97254 | 23·41 | 19·11 |
| 87 | 62·5 | ·97458 | 21·39 | 17·42 |
| 88 | 66·0 | ·97660 | 19·41 | 15·78 |
| 89 | 69·4 | ·97857 | 17·46 | 14·16 |
| 90 | 72·8 | ·98057 | 15·51 | 12·56 |
| 91 | 76·1 | ·98261 | 13·58 | 10·97 |
| 92 | 79·2 | ·98452 | 11·85 | 9·56 |
| 93 | 82·3 | ·98657 | 10·04 | 8·08 |
| 94 | 85·2 | ·98866 | 8·28 | 6·65 |
| 95 | 88·0 | ·99047 | 6·83 | 5·48 |
| 96 | 90·7 | ·99251 | 5·25 | 4·20 |
| 97 | 93·3 | ·99448 | 3·80 | 3·03 |
| 98 | 95·9 | ·99658 | 2·31 | 1·84 |
| 99 | 98·2 | ·99851 | ·997 | ·793 |
| 100 | ... | 1·00000 | ... | ... |
+-----------+---------+----------+----------+---------+

This Table {above} has been copied, by permission, from Loftus's 'Inland Revenue Officer's Manual,' and its correctness verified by W. H. Johnston, Esq., Surveying General Examiner.

TABLE II.--_Table for finding the Specific Gravity of
any Spirit at 60° Fahr., when the Specific Gravity at
any other Temperature is given._

Water taken as 1000.
+-----------------+----------+-----------------+----------+
| |Correction| |Correction|
|Specific gravity.| for each |Specific gravity.| for each |
| | degree. | | degree. |
+-----------------+----------+-----------------+----------+
| 810 to 820 | ± ·475 | 910 to 920 | ± ·434 |
+-----------------+----------+-----------------+----------+
| 820 " 830 | ± ·473 | 920 " 930 | ± ·424 |
+-----------------+----------+-----------------+----------+
| 830 " 840 | ± ·472 | 930 " 940 | ± ·406 |
+-----------------+----------+-----------------+----------+
| 840 " 850 | ± ·471 | 940 " 950 | ± ·381 |
+-----------------+----------+-----------------+----------+
| 850 " 860 | ± ·471 | 950 " 960 | ± ·340 |
+-----------------+----------+-----------------+----------+
| 860 " 870 | ± ·466 | 960 " 970 | ± ·269 |
+-----------------+----------+-----------------+----------+
| 870 " 880 | ± ·460 | 970 " 980 | ± ·165 |
+-----------------+----------+-----------------+----------+
| 880 " 890 | ± ·456 | 980 " 990 | ± ·090 |
+-----------------+----------+-----------------+----------+
| 890 " 900 | ± ·450 | 990 " 1000 | ± ·084 |
+-----------------+----------+-----------------+----------+
| 900 " 910 | ± ·442 | | |
+-----------------+----------+-----------------+----------+

Thus, by making the proper ADDITION to the apparent strength per cent., when the observed temperature is BELOW the normal temperature of the instrument, or a corresponding SUBTRACTION, when it is ABOVE it, the strength of the sample may be determined sufficiently near for all practical purposes.

The following Table, taken from Loftus's 'Inland Revenue Officer's Manual,' will be found of great value in making these corrections, and has the merit of being easily applied.

An example will show how this Table is to be used.

_Example._--If a quantity of spirit is of the sp. gr. 894 at 73°, what will be its sp. gr. at 60°?

Here the sp. gr. being between 890 and 900, we must add ·450 for each degree of temperature between 73° and 60°. The sp. gr. at 60° would, therefore, be 894 + (·450 × 13) = 899·85. When the temperature is below 60°, the correction for each degree must be subtracted. When, however, very accurate results are desired, and the necessary Tables are not accessible, the sample for trial must be brought to the normal temperature of the instrument, in the manner explained under HYDROMETRY.

_c._ From the SPECIFIC GRAVITY. The temperature having been taken by a thermometer, and the specific gravity ascertained by any of the usual methods, but preferably by means of an accurate glass hydrometer, it merely becomes necessary to refer to Table I, where, against the number expressing the specific gravity, the alcoholic content per cent., by volume, of the sample examined, will be found for 60° Fahr., subject to the corrections just referred to, when the temperature is either above or below this point.

If the precise specific gravity sought cannot be found in the _Table_, the difference between it and the next greater specific gravity must be taken for the numerator of a fraction, having for its denominator the difference between the greater and the next less specific gravity in the table. This fraction, added to the per-centage of alcohol in the fourth column of the table, opposite the greater sp. gr., will give the true per-centage sought. Thus, the sp. gr. ·96051 is not in the table, and the next greater number is ·96068; the former must, therefore, be deducted from the latter, and the difference (17) put as the numerator of the fraction, having for its denominator 191, the difference between ·96068 and ·95877. The fraction (17/191) ·089, so found, added to the per-centage strength opposite ·96068 in the third column, gives 33·989 as the true per-centage of alcohol in the given sample.

The per-centage by volume may be converted into per-centage by weight, by multiplying the former by ·793811, the sp. gr. of absolute alcohol, and dividing the product by the sp. gr. of the sample. The quotient is the number of pounds of alcohol in 100 pounds of the given spirit. Thus:--Suppose 1000 grains by measure of alcohol to weigh 950·92 grains, and to contain (see Table I) 40·63 per cent. by volume of absolute alcohol, what per cent. by weight does the sample contain?

·793811 × 40·63 = 32·25254093, and this product divided by ·95092 = 33·917, the true per-centage by weight of absolute alcohol in the sample.

2. Method based on the specific gravity, or per-centage strength by WEIGHT:--

The specific gravity is ascertained and the Table used in precisely the same manner as in the "method by volume," already described.

The per-centage by weight may be converted into per-centage by volume, by multiplying the former by the sp. gr. of the sample, and dividing the product by the sp. gr. of absolute alcohol. This is merely the reverse of the operation described above.

_Obs._ The preceding methods of alcoholometry, as well as all others depending on the sp. gr. refer to UNSWEETENED SPIRITS only; and are inapplicable to those holding sugar in solution, or any other organic matter capable of altering the sp. gr. For sweetened spirits, fermented worts, wine, beer, &c., one or other of the following processes must be adopted:--

3. Other methods, adapted to either SWEETENED or UNSWEETENED SPIRITS, Tinctures, Fermented Liquors, &c.--

_a._ By DISTILLATION as originally proposed by M. Gay-Lussac. 300 parts of the liquor under examination (measured in a graduated glass tube) are placed in a retort or small still, and a quantity exactly equal to one third (_i.e._, 100 parts), carefully drawn over; a graduated glass tube[13] being used as a receiver, and the operation stopped as soon as the distillate reaches the hundredth degree. The 'alcoholic strength' of the distilled liquor is then ascertained by any of the usual methods, and the result divided by three, when the per-centage of alcohol in the original liquor is at once obtained. If, from want of attention, more than 100 parts should be distilled over, the number which expresses the relation of the volume of the distilled product to the original bulk of the liquor tested, must be employed as the divisor. Thus, if 106 parts of liquor have distilled over (instead of 100), containing 33% of alcohol, the 300 must be divided by 106, which gives 2·83, and the 33% by this 2·83, which gives 11·66%, the true proportion of alcohol in the original liquor. The strength at 'proof' may be calculated from this in the usual way.

[Footnote 13: Mulder, in his 'Chemistry of Wine' recommends this receiver to be shaped like a bottle, with its neck, or tubular part, bent at right angles above the line of its scale; and that it should be set in the centre of a glass jar kept filled with very cold water.]

To ensure accurate results, the acidity (if any) of the liquor must be neutralised with carbonate of sodium, prior to distillation. It is also advisable to add 8% or 10% of common salt to the liquor in the retort or still; this, by raising the boiling point, causes the whole of the spirit to pass over into the receiver before the distillate has reached the required measure. This applies more particularly to weak liquors. With those of greater strength (as the stronger wines), it is better to distil over 150 parts, and divide the result by 2 instead of 3. To liquors stronger than 25% by volume of alcohol, or above 52% to 54% under proof, add about an equal volume of water to the liquor in the still, and draw over a quantity equal to that of the sample tested; when the alcoholic strength of the distillate gives, without calculation, the true strength sought. To liquors stronger than 48% to 50% (14 to 12 u. p.), add thrice their bulk of water, and do not stop the process until the volume of the distillate is double that of the sample tested, when the per-centage obtained must also be doubled. In each case a proportionate quantity of salt is employed.

REVENUE METHOD. The following is the method adopted in the Inland Revenue and Customs Laboratories for the estimation of the per-centage of alcohol in wines, liqueurs, &c. A measure flask is filled up to a mark on its neck, with the wine, which is then carefully transferred to a distilling flask or retort, the traces of wine remaining in the former vessel being rinsed out with small quantities of distilled water, and the rinsings added to the wine in the latter vessel. About two thirds of the contents of the retort are then distilled over into the clean measure flask, and made up to the original bulk with distilled water, at the same temperature as the sample was previous to distillation. The strength is then taken by Sykes' hydrometer, and this (if u. p.) deducted from 100, gives the per-centage of proof spirit in the wine. Thus:--

Strength of distillate = 74·6 u. p. = 25·4 per cent. proof spirit.

_b._ From the TEMPERATURE of the VAPOUR, as originally proposed by Gröning. The bulb of a thermometer is thrust through a cork into the head of the still, or other vessel employed, and the temperature of the vapour in which it is immersed being noted, is sought in the following table:--

TABLE III.--_Showing the Alcoholic Content, by_
VOLUME_, of Boiling Spirits, and of their Vapour, from
the Temperature of the latter, as observed by a
Thermometer._ By GRÖNING.

+---------------+-------------------+-------------------+----------------+-------------------+------------------+
|Temperature of | Alcoholic content | Alcoholic content | Temperature of | Alcoholic content | Alcoholic content|
| the Vapour. | of the Distillate | of the Boiling | the Vapour. | of the Distillate | of the Boiling |
| Fahr. | per cent. | Liquid per cent. | Fahr. | per cent. | Liquid per cent.|
+---------------+-------------------+-------------------+----------------+-------------------+------------------+
| 170·0 | 93 | 92 | 189·8 | 71 | 20 |
| 171·8 | 92 | 90 | 192·0 | 68 | 18 |
| 172·0 | 91 | 85 | 194·0 | 66 | 15 |
| 172·8 | 90-1/2 | 80 | 196·4 | 61 | 12 |
| 174·0 | 90 | 75 | 198·6 | 55 | 10 |
| 174·6 | 89 | 70 | 201·0 | 50 | 7 |
| 176·0 | 87 | 65 | 203·0 | 42 | 5 |
| 178·3 | 85 | 50 | 205·4 | 36 | 3 |
| 180·8 | 82 | 40 | 207·7 | 28 | 2 |
| 183·0 | 80 | 35 | 210·0 | 13 | 1 |
| 185·0 | 78 | 30 | 212·0 | 0 | 0 |
| 187·4 | 76 | 25 | | | |
+---------------+-------------------+-------------------+----------------+-------------------+------------------+

This method is admirably adapted to the purposes of the distiller and rectifier, as it furnishes a ready means of approximately determining the strength of the spirit passing over, at every part of the process of distillation, as well as that of the wash left in the still.

_c._ From the BOILING POINT, as originally proposed by M. l'Abbé Brossard-Vidal. This method is founded on the fact, that the boiling points of mixtures of alcohol and water, unlike water alone, are scarcely disturbed by the addition of saline, saccharine, or extractive matter within certain limits. It hence offers a ready means of determining the proportion of alcohol present in spirits, wines, fermented liquors, &c., with sufficient accuracy for all ordinary purposes. In applying it, a thermometer, with a large bulb and a narrow bore, and a movable scale graduated from 180° to 212° Fahr., is usually employed. Before using it as an alcoholometer, it is set, with its bulb immersed, in a small metallic boiler (brass or copper) containing distilled water, which is then raised to the boiling-point, and the 212° of the scale accurately adjusted on a level with the surface of the mercury, should it vary from that point. This is necessary on account of variations of atmospheric pressure causing corresponding variations of the boiling-points of liquids. It is then ready for several hours' operations, and, generally, for an entire business day, without further adjustment. The little boiler is next filled with the liquor to be examined, and the lamp again lighted. The temperature as shown by the scale of the instrument at the commencement of full ebullition being ascertained, may be sought in one of the following _Tables_, against which the alcoholic content of the liquor will be found (nearly).

TABLE IV.--_Exhibiting the_ BOILING POINTS _of Mixtures
of Alcohol and Water of the given strengths._ By
GRÖNING.

---------------+------------+----------------+------------
| Alcohol | | Alcohol
Boiling point. | per cent. | Boiling point. | per cent.
Fahr. | by volume. | Fahr. | by volume.
---------------+------------+----------------+------------
205·34 | 5 | 179·96 | 55
199·22 | 10 | 179·42 | 60
195·8 | 15 | 178·7 | 65
192·38 | 20 | 177·62 | 70
189·50 | 25 | 176·54 | 75
187·16 | 30 | 175·46 | 80
185· | 35 | 174·92 | 85
183·38 | 40 | 174·2 | 90
182·12 | 45 | 173·14 | 95
181·58 | 50 | 172· | 100
---------------+------------+----------------+------------

TABLE V.--_Showing the_ BOILING POINTS _of 'under
proof' spirit._ By Dr URE.

----------------+-------------+---------------
Boiling points. | Per-centage | Corresponding
Fahr. | strength. | Sp. Gr.
----------------+-------------+---------------
178·5 | Proof. | ·9200
179·75 | 10· U.P. | ·9321
180·4 | 20· " | ·9420
182·1 | 30· " | ·9516
183·4 | 40· " | ·9600
185·6 | 50· " | ·9665
189· | 60· " | ·9729
191·8 | 70· " | ·9786
196·4 | 80· " | ·9850
202· | 90· " | ·9920
----------------+-------------+---------------