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it is left to stand for some time, the process is called | maceration. When a soluble body is separated from an insoluble one by washing, the process is called lixiviation. Suppose it were necessary to separate a salt from a quantity of ashes: a funnel of sufficient size should have the lower aperture stopped by a cork, and should be supported on a stand, so that it may steadily retain its proper position. A few pieces of the ash, of such size that they shall not pass through the neck of the funnel, should be introduced in the first place, to prevent the descent of the matter to be placed over it. Having added pieces rather smaller, until the surface exposed in the funnel is an inch in diameter, the rest should be crushed in a mortar to a coarse powder, or rather to small pieces or grains, and put into the funnel above that previously arranged. If the substance be such that it will not afford lumps of sufficient size or strength to remain in the neck of the funnel and support the rest, then its place should be supplied by some pieces of broken glass, which may be continued to the height before mentioned, and which, while they support the substance, afford abundant passages for the fluid when required. Being thus far arranged, hot or cold water is to be poured into the funnel, according to circumstances, its quantity being such that it will just cover the mass. The whole is to be left in that state for a time proportionate to the solubility of the substances present. The water which has penetrated the fragments will gradually dissolve the salts, and forming a heavy solution, will descend in the free spaces, changing situations with the water not yet saturated. In this way a solution will be produced, of much greater strength below than above, and the upper part of the mass will be washed almost perfectly at the first operation. When sufficient time has been allowed, according to the quantity and nature of the salt, and the manner in which it is enveloped, the cork beneath should be withdrawn, and one-half or two-thirds of the solution suffered to run out gradually, not hastily, lest greater disturbance of the solid matter in the funnel be occasioned than is necessary or advantageous. The cork is to be replaced, fresh water added above, so as not to disturb the arrangement; and being left as before for a time, the second solution should then be withdrawn, and this operation repeated till the water which passes is perfectly free from salts, or contains so little as to make further attention unnecessary." 1 DECOMPOSITION, the separation of a compound body into its component parts, either spontaneously or by chemical agency. Thus the decomposition of sulphate of iron furnishes sulphuric acid and oxide of iron as its proximate elements, and sulphur, oxygen, and iron as its ultimate elements. By decomposition substances are produced whose properties are essentially distinct from those of the compound. Such is not the case by mere mechanical action, for if a compound be reduced by grinding or other mechanical means to an impalpable powder, its chemical properties still remain unchanged. See ANALYSIS.

(1) Faraday: "Chemical Manipulation," Section VI.

DEFLAGRATION is the sparkling combustion of substances without violent explosion, as when charcoal or sulphur is thrown into melted nitre. Glassstoppled jars, used in the lecture-room, for showing the combustion of different bodies in certain gases, such as phosphorus, sulphur, charcoal, &c. in oxygen, protoxide of nitrogen, &c., are called deflagrating jars; the substance to be burnt is inserted by means of a small metal spoon called a deflagrating spoon.

DELF, or DELFT, a kind of coarse porcelain originally manufactured at Delft, in Holland. It has been superseded even in Holland itself by the superior manufactures of England and the improved taste introduced by Wedgwood in the making of pottery.

DELIQUESCENCE. Salts which gradually dissolve, or deliquesce, by attracting moisture from the air, are called deliquescent salts: such are carbonate of potash, acetate of potash, chloride of calcium, &c. Other salts, which give out moisture to the air, are called efflorescent salts: thus sulphate of soda, or Glauber's salts, by exposure, spontaneously parts with its water of crystallization, loses its transparency, and crumbles down into a white powder.

DENSITY. The proportion of the quantity of matter to the magnitude is called the density of a substance. Thus if of two substances one contain in a given space twice as much matter as the other, it is said to be twice as dense. The density of bodies is therefore proportionate to the closeness or proximity of their particles; and the greater the density, the less the porosity. See SPECIFIC GRAVITY.

DETONATION, an explosion accompanied by noise. A stout glass tube used in the analysis of gases by firing them with the electric spark is called a detonating tube, and the process of firing is called detonation. See EUDIOMETER.

DEXTRINE. See BEER-STARCH.
DIAMOND. See CARBON.

DIAPER, a sort of fine flowered linen, used chiefly for table-cloths, napkins, &c. See WEAVING. DIASTASE. See BEER.

DIE-SINKING. The operation of hardening is so intimately connected with the preparation of dies, and the multiplication of engravings thereby, that we propose to include our remarks on the subject under HARDENING and TEMPERING.

DIGESTER, a boiler, invented by Papin, closed by a tightly fitting cover, which is held down by a screw s, Fig. 710: this cover has two openings, one of which is closed by a stopcock c, and the other is furnished with a valve v, pressed down by a weighted lever, I w. The weight of course acts with greater or less power, according as it is further from or nearer to the fulcrum. This valve is forced open when the pent-up steam has acquired a certain amount of tension, and a portion of it escaping, the temperature and consequently the elasticity of the steam are diminished and the danger of explosion avoided. In Fig. 710, a portion of the side is represented as broken away, in order to show the arrangement of the valve, &c. A common form of digester is called an autoclave, Fig. 711, on account of the lid being

self-keyed, whereby it becomes steam-tight by turning | conducted only in a small way, and when the vapour
it round under clamps or ears at the sides. The use is easily condensible or when a moderate heat is
of the digester is to subject certain articles of food,
&c. to higher temperatures than can be attained

applied.

Fig. 712 shows a common laboratory arrangement for distillation with a glass retort and receiver. In order to produce a complete condensation, the neck of the retort is covered with linen or bibulous paper, kept constantly wet by cold water dripping upon it

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when the surface of the boiling liquid is exposed to atmospheric pressure. [See EBULLITION.] The increased temperature of water thus produced enables it to separate the gelatine from the phosphate of lime of bones; but the soup made from this gelatine has often an empyreumatic and ammoniacal taste. See BONE-GELATINE.

DIMITY, a stout cotton cloth ornamented either with raised stripes or figures, and employed white for

bed and bed-room furniture.

DISTILLATION, a process by which one body is separated from another by means of heat, in cases where one of the bodies assumes the elastic form at a lower temperature than the other: this first rises in the form of vapour, which is received and condensed in a separate vessel. When the vapour condenses in the solid form, such as sulphur, calomel, &c., the process is termed SUBLIMATION. [See ALEMBICCAMPHOR-SULPHUR.] In this case, the substance to be distilled is usually placed in the lower part of the vessel to which heat is applied, and the vapour rising to the upper and cooler part adheres to it; or an upper vessel being inverted over the lower one, the vapour is condensed within it in the form of a solid cake. When, however, the condensed vapour is obtained in the liquid form, the arrangements are different. The vapour must be preserved in its elastic form up to a certain height, at which the neck of the vessel turns by a sharp curve or an elbow, so that after the vapour has been condensed into the liquid form it descends as quickly as possible. The height of the elbow above the point where the heat is applied, must be only just sufficient to prevent the mass below from boiling over the neck. When the neck of the lower vessel is of great length, the escape of heat must be prevented either by giving it a polished surface, or by covering it with some nonconducting body. The vessel used for generating the vapour, if of large size, is called a still. Distillation as carried on by the chemist is usually by means of retorts, and the vessel that receives the distilled matter is called a receiver; this is perhaps the most simple method of distilling; but it can generally be

Fig. 712. FARADAY'S ARRANGEMENT.

from a funnel or filter: a few threads of twisted tow draw off this water into a basin. The contents of the retort are vaporized by means of the gas-flame; and the vapour passing along the neck may be wholly or partially condensed: any vapour which escapes condensation passes into the quilled receiver, where it is condensed; the bottle containing the distilled product being surrounded with water, or, if necessary, with a freezing mixture.

Liebig's condenser, shown in Fig. 713, consists of a slightly conical glass tube, 18 or 20 inches long,

Fig. 713. LIEBIG'S ARRANGEMENT.

and of a diameter of about 1 or 2 inches at one end and an inch or less at the other: this is enclosed water-tight in a wider and shorter metal tube, to the lower end of which is attached a funnel supplied with a small current of cold water from a cistern above. As the cold water enters the bottom of the tube, it gradually ascends, and becomes warmed by condensing the hot vapours; and having performed its useful office of keeping the tube cool, it drips or flows off, according to the supply from the cistern, by the hanging tube. The whole arrangement will be evident from an inspection of the figure.

The still is usually so arranged as to present a large surface to the fire. For this purpose it is commonly

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made in the form of a frustum of a cone, the base | the flue all round. This narrow aperture prevents being as large as it can conveniently be made, and the rapid escape of the heated vapour, and allows it the height small. The neck should be wide enough to be expended on the vessel. to convey away the vapour as fast as it is formed: the height of the neck must be regulated by the nature of the substance. If it be mucilaginous, such as the wash from which spirit is distilled, the neck should be longer, to prevent its boiling over. The end of the descending part of the neck is inserted into a spirally twisted pipe called the worm. The worm is continued in a worm-tub, about 6 or 8 times the capacity of the still. The worm enters on one side of the tub at the top; it then passes spirally in about 6 or 8 convolutions to the bottom, where it comes out of the side in order to discharge the liquid arising from the vapour condensed within it by means of the cold water with which the tub is filled. The water is kept cold in the tub by the warm water flowing away from the top whilst a supply of fresh cold water is admitted at the bottom. It is of importance to keep the worm as cool as possible, because the object is not merely to condense the vapour, but to cool the liquid resulting from it, in order that it may be less liable to evaporation after coming over. Fig. 714 shows a common form of still, in which s is

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the still, the head, w the worm, and R the wormtub or refrigerator.

The process of distillation is exceedingly important in a manufacturing point of view, the business of the distiller being to prepare the enormous quantities of ardent spirits which are consumed in this country and exported. The processes of the distiller preparatory to the act of distillation resemble in many respects those of the brewer. [See BEER.] He prepares a saccharine solution, or wort, and sets it fermenting by the aid of yeast; but instead of allowing the alcohol thus formed to remain in the liquor, as in the case of malt liquors, he separates it by distillation. In all the varieties of ardent spirits, alcohol, formed by the fermentation of sugar, is the intoxicating principle: the aroma or peculiar flavour which distinguishes one spirit from another seems to be due to the presence of an essential oil derived from the substance employed to furnish the saccharine solution. Thus the sugar-cane yields an oil which imparts the peculiar flavour to rum, and rum is obtained from the refuse of cane-sugar in the West Indies. The grape yields an oil which flavours brandy, and brandy is obtained by distilling wine: it is made in large quantities in France, Spain, and other wine countries. Gin, whiskey, &c., are obtained from malt or from the raw grain; the starch, which forms so large a portion of barley, being converted by the action of warm water into sugar, and this into alcohol. Milk contains a saccharine substance, known as sugar of milk, capable of forming alcohol by fermentation: the Tartars manufacture from mare's milk an ardent spirit named koumiss. Arrack is prepared from the juice of the coco-nut. [See Coco.]

The manufacture of ardent spirit, as conducted in this country, from grain, as in the preparation of whiskey, comprises four principal processes: viz. 1, mashing; 2, cooling; 3, fermenting, and 4, distilling. The grain used is barley, only a portion of which is malted, in consequence of the duty on malt.

1. Mashing. The barley is ground to a fine meal, and the malt is crushed between rollers. Dr. Thomson gives an example from the Scotch distillers, (who have long conducted this branch of manufacture with great skill and success,) in which the proportions are 40 bushels of barley and 20 of malt The mash-tun is of cast-iron, and the water, measuring 700 or 800 wine gallons, is let in at the temperature of 150°. The mashing is continued from 1 to 4 hours, either by manual labour or machinery; the longer time being required if the proportion of raw grain prevails. To keep up the heat, about 500 gallons of water are (1) The word whiskey is said to be derived from the Irish, usquebaugh, which is identical with eau de vie, or water of life. (2) Dr. George Wilson, Professor of Chemistry at Edinburgh, informs the Editor that at the Sunbury Distillery, situate about a mile to the north-west of Edinburgh, where grain-whiskey only is made, "the grain employed is in greater part barley, which is ground pretty finely in a mill. To this a certain portion of oats is always added. They are not ground to powder, but only crushed, or, as the distillers call it, rolled, and by their large grain they prevent the barley meal from clogging and caking into a mass. A small quantity of malt is added, su saccharify the starch of the barley and oats, and the

The arrangement of the fire for heating the still is of importance. The fire should be so placed upon a grate that a due supply of air be admitted to excite a vigorous combustion: no air should be supplied but through the grate; and the quantity of heat will be greatest when the air which enters is not more than sufficient for the combustion; an excess only serving to cool that which the fire had heated. The products of combustion should escape at a point not higher than the level of the grate, so that the heated matter before escaping may impart its heat to the vessel. In the common spirit-still the bottom is circular, and the exterior surface presented to the fire is concave. The fire is placed in the middle of the circle, as in the furnace of Fig. 720: the flame and heated vapour first rise up against the middle of the concave bottom, then move towards the periphery of the circle, and descend as low as the level of the grate, and enter the flue through a narrow neck, which extends through the whole periphery of the circle, and which opens into in the ordinary way."

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admitted at intervals, at temperatures varying from | 190° to 205°. The mashing being completed, the whole is left for about 2 hours for infusion, as the distillers term it. During this time the grains sink, leaving the liquid but muddy wort above. A considerable portion of starch remains unaltered; but the wort gradually increases in sweetness from the beginning to the close of the operation. The wort is drawn off, not as in making beer, at the bottom, because it will not pass through the sediment of barley meal it is drawn off from the top by a tube pierced full of holes, and rising at one corner of the mash-tun as high as the surface of that vessel. The quantity of wort does not exceed one-third of the water employed; the 1,200 gallons yielding only 400 gallons of wort. To prevent the loss of the remaining two-thirds of the wort, about 500 gallons of water at 190° are let in, and the whole, being well mixed, is left for an hour and a half to infuse, and it is then drawn off. The grains, having been deprived of the greater portion of their starch, now part more freely with the water; and in order to carry off everything soluble, about 800 gallons of boiling water are let in upon the grains: the whole is stirred up during 20 minutes, and left for infusion about 30 or 40 minutes. The weak wort which is drawn off is used for mixing with the meal and malt in the next brewing, or, being boiled down to the requisite strength, it is mixed with the first and second worts in the fermenting vessel. Some distillers even make a fourth mash with boiling water, and use the wort instead of pure water in the next day's brewing.

It is important that the distiller should be able to regulate the strength of his worts with precision, as the duty is regulated thereby. The quantity of spirit from 100 gallons of fermented wort is required by law to be 14 gallons: at any rate, the Scotch distillers pay that duty, whether they produce it or not. According to Dr. Thomson, 14 gallons of spirit of the specific gravity 0.90917 from 100 gallons of wort requires the original strength of the wort to be at least 70 lbs. per barrel. With the above quantities of grain, malt, and water, the first worts will be of the strength of about 73lbs. per barrel; the second worts 50lbs. per barrel, and the two, when mixed, 62lbs. per barrel.

The distiller has been for a long period so much fettered by excise regulations as to have had no opportunity of varying and improving his manufacture. The illicit distiller, unimpeded by the restraints of law, has been able to produce a better article, by using malt without any admixture of raw grain: it is also said that the superiority was partly due to the slow mode of distillation adopted by the smuggler. This superiority, perhaps further recommended by its greater cheapness, would be sure to be appreciated among a whiskey-drinking people: the illicit distiller would therefore be favoured and protected, and thus the morals of the people, the revenue, and the regular manufacturer, would all suffer in consequence of injudicious regulations on the part of the government. Of late years, however, the distillers have been al

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lowed to distil from malt at nearly the same rate as they formerly did from raw grain, and hence the high reputation of smuggled whiskey has declined, and with it the occupation of the smuggler. The restrictions under which the distillers were placed were said to be necessary in order to ensure the payment of the duty on the spirits actually distilled. But, as Dr. Thomson suggests, the duty might be levied with as much accuracy, though all restrictions on the strength of the wort were removed. 'From a number of experiments, conducted on a large scale, we conclude that the fermentation, however successful, is capable of decomposing only four-fifths of the whole saccharine matter contained in the wort. Further, we find that, for every pound of saccharine matter decomposed by the fermentation, there is formed half a pound of alcohol, of the sp. gr. 0.825. Now, every gallon of spirits of the sp. gr. 0.90917, or 1 to 10 over proof, contains 4.6lbs. of alcohol of the sp. gr. 0.825. To form a gallon of spirits, then, of the sp. gr. 0.90917, there is required the decomposition of 9.2lbs. of saccharine matter. But as only four-fifths of the saccharine matter present are decomposed, we must increase 9.2 by a fifth, which will raise it to 11lbs. The rule, therefore, for levying the duty on the distillers would be this:-Ascertain by the saccharometer the strength of the wort, or the number of pounds avoirdupois of saccharine matter which it contains, and for every 11 of these pounds charge the duty upon one gallon of spirits. This would be no hardship upon the distiller. He would find that the flavour, and consequently the value of his spirits, increases as he diminishes the strength of his wort, and that the produce of spirits from the same quantity of grain increases also as he diminishes the strength of his wort." 2

2. Cooling. As wort from raw grain tends to acidity sooner than wort from malt, the distiller cools his worts as quickly as possible. They are removed from the underback to the coolers, consisting of shallow wooden vessels, in the upper part of the building: the depth of the sheet of wort may be 1, 2, or 3 inches, according to circumstances. Another method of cooling is by passing the wort through pipes immersed in a stream of cold running water. There is no evaporation in this method, as there is in the former, and consequently the strength remains the same after cooling as before. This is of some disadvantage to the distiller, as the duty is levied on the bulk and not on the strength of his worts. During the cooling there is a considerable deposit of flocky matter, consisting chiefly of starch: this is swept into the fermenting tun, and is supposed to assist the fermentation. Winter is the usual season for the operations of the distiller, as it is difficult in warm weather to keep the fermenting room sufficiently cool. The worts are let down at about 70°, and the second worts at 60° or 65°.

3. The process of fermentation is the most important part of the manufacture, as on it the profit or the loss

(1) See BEER, ante, p. 117, Fig. 111.
(2) Encyclopædia Britannica; art. Distillation.

Dr. George Wilson informs the Editor that at the Sunbury Distillery the cost of yeast is 507. per week. He says that the Scotch whiskey distillers trust to the care bestowed by the ale and porter brewers, that the yeast is sufficiently often varied and otherwise in good condition; the brewers exchanging yeast with each other at intervals,—a practice which is necessary to prevent the yeast from deteriorating. The brewers mingle the yeasts of different breweries together until they produce a liquid of a certain thickness and strength, of which they judge by an empirical rule. They seem to be indifferent as to the source of the yeast, so far as beer, ale, or porter are concerned; but they aim at securing it of standard strength, by mixing the thin and the thick, the active and the sluggish.

A practical writer thus describes the phenomena of fermentation :-" Soon after the yeast or bub has been added to the worts, fermentation commences: its first effects are indicated round the sides of the back by the appearance of a scummy-looking matter on the surface of the worts, and the emission of small bubbles which contain carbonic acid gas. The tem

of the manufacturer chiefly depends. The yeast, | is not allowed to be more than five per cent. on the which is supplied by the porter and ale brewers, quantity of worts previously collected. This allowmust be of the best quality. For the quantity of wort ance is generally found to be more than sufficient. already indicated, about 27 gallons of good yeast are required, or 36 gallons if the yeast be of inferior quality. A portion only is first mixed with the wort, other portions being added on the second, third, fourth, and even on the sixth days. Some distillers add 9 gallons every day for 4 days. The fermentation may last 9, 10, 11, 12, or even 13 days. During the first 5 days the fermenting tuns are left open at the top, or are only partially covered; but on the sixth day they are shut up for the purpose of confining the carbonic acid gas, which in escaping carries off a portion of alcohol, and thus occasions loss. It generally happens, however, that the fermentation is nearly over before the tuns are shut, so that the loss of alcohol by the escape of carbonic acid has already occurred. The presence of the carbonic acid is also supposed to promote fermentation, and by preventing its ready escape the attenuation of the wort is supposed to be greater than it otherwise would be. This may be true, because it is known that carbonic acid may be substituted for yeast as a ferment. The distiller does not collect any yeast from his worts, but beats it all into the liquor; he supposes that by collecting it the ferment-perature increases as fermentation advances: its ation would be less complete, and the alcoholic product diminished. During the fermentation the temperature of the wort rises considerably; often as much as 20° or 25°, so that if let down at 57° its temperature may rise to 78° or 82° about the fourth or fifth day. The time when this maximum is attained is, however, uncertain, and depends to a great extent on the quality of the yeast employed; and it is the uncertain character of the yeast which makes the difficult business of the distiller still more difficult. As the fermentation proceeds, the specific gravity of the wort diminishes, owing to the decomposition of the sugar and its conversion into alcohol and carbonic acid. In all cases of fermentation, in a Scotch distillery at least, one-fifth of the whole of the saccharine matter escapes decomposition, in consequence of the anti-fermenting power of the alcohol evolved. Hence it is more profitable for the distiller to operate with weak worts than with strong ones, for the weaker the original wort, the less will be the quantity of the saccharine matter which escapes decomposition. When the heat is at its maximum nine-tenths of the whole attenuation has been completed. The object of the distiller is to render his wash, or fermented wort, as light as water, and he will be able to do so unless his yeast be of bad quality.

When yeast cannot be readily procured, a substitute called bub is employed. It is prepared by thoroughly mixing together a quantity of meal or flour with a little yeast in a quantity of warm worts and water: the whole being closely covered up, a violent fermentation almost immediately ensues, and in that state it is added to the worts. Should the fermentation be found to lag, some yeast is added; but for revenue purposes the whole quantity of bub and yeast

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progress is rather slow at first, but gradually increases, and after some time proceeds with prodigious rapidity. Large bubbles of carbonic acid gas escaping set the whole in motion, as if in a state of violent ebullition; a large quantity of froth collects on the surface of the liquor (which is now called wash), which often accumulates with such rapidity that several men are required to beat it down with oars, to prevent its spilling over the top; indeed, on some occasions, the beating on the top has been found ineffectual, and the distiller forced to pump a portion of the wash up to the coolers, to lower its temperature, and then return it, after which the process proceeded at a moderate rate; and in all cases, towards its close, the rate of fermentation gradually diminishes, and the temperature decreases, till at last the wash acquires the temperature of the tun-room, and remains quiescent." 1

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Dr. George Wilson, in a letter to the Editor, thus notices the fermenting-tuns of the Sunbury Distillery: I thought of Priestley as I stood at the small doorway of one of the immense vats, from which the mixed vapour of alcohol and carbonic acid was issuing, extinguishing candles held near it, and falling with a blinding anæsthetic weight on the breathing organs of all respiratory animals near it. Professor Simpson tells me that he thinks the intoxicating power of champagne is owing to the vaporization of alcohol along with carbonic acid. I always thought the theory a true one, but I realized its truth to-day. A single whiff of the vapour, gushing forth in sufficient volume to blow upon the face, was enough to make a friend and myself spring back with our hands on our faces. We did not try a second draught."

(1) Thomson's "Reco.ds of General Science," vol. i.

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