Or compared to water as unity, fic gravity of oxygen to be M M. Biot and Arago found the speci1.10359 and that of nitrogen, . 0.96913 air being reckoned, 1.00000 Nitrogen is 0.001182338 0.001346379 = 0.00094587 transition of water through the roofs of caverns in a calcareous soil, do not differ in appearance from the alabaster, most of which is also formed in this manner. But the calcareous stalactites here spoken of consist of calcareous earth and carbonic acid; while the alabaster of the chemists is formed of the same earth and sulphuric acid, as has already been remarked. -0.00026927 * ALBIN. A mineral discovered at Mo0.00121514 naberg, near Aussig, in Bohemia; and being of an opaque white colour, has been 0.000934 called, by Werner, albin. Aggregated 0.000283 crystalline laminæ constitute massive albin. Pure alkalis dissolve it, even after coagulation. It is precipitated by muriate of mercury, nitro-muriate of tin, acetate of lead, nitrate of silver, muriate of gold, of dry albumen forms by heat a solid 0.001217 A number which approaches very nearly to the result of experiment. Many analogies, it must be confessed, favour Dr. Prout's proportions; but the greater number of experiments on the composition and density of the atmosphere agree with Biot's results. Nothing can decide these fundamental chemical proportions except a new, elaborate, and most minutely accurate series of experiments. We shall then know whether the atmosphere contains in volume 20 or 21 per cent of oxygen. See METEOROLOGY.* ALABASTER. Among the stones which are known by the name of marble, and have been distinguished by a considerable variety of denominations by statuaries, and others whose attention is more directed to their external character and appearance than their component parts, alabas ters are those which have a greater or less degree of imperfect transparency, a granular texture, are softer, take a duller polish than marble, and are usually of a whiter colour. Some stones, however, of a veined and coloured appearance, have been considered as alabasters, from their possessing the first mentioned criterion; and some transparent and yellow sparry stones have also received this appellation. Chemists are at present agreed in applying this name only to such opaque, consistent, and semi-transparent stones, as are composed of lime united with the sulphuric acid. But the term is much more frequent among masons and statuaries than chemists. Chemists in general confound the alabasters among the selenites, gypsums, or plaster of Paris, more especially when they allude only to the component parts, without having occasion to consider the external appearance, in which only these several compounds differ from each other. As the semi-opaque appearance and granular texture arise merely from a disturbed or successive crystallization, which would else have formed transparent spars, it is accordingly found, that the calcareous stalactites, or drop-stones, formed by the Small crystals of it in right prisms, whose summits consist of four quadrangular planes, are found sprinkled over mammelated masses in cavities.* See ZEOLITE. ALBUM GRECUM. Innumerable are the instances of fanciful speculation and absurd credulity in the invention and application of subjects in the more ancient materia medica. The white and solid excrement of dogs, which subsist chiefly on bones, has been received as a remedy in the medical art, under the name of Album Græcum. It consists, for the most part, of the earth of bones, or lime in combination with phosphoric acid. ALBUMEN. This substance, which derives its name from the Latin for the white of an egg, in which it exists abundantly, and in its purest natural state, is one of the chief constituent principles of all the animal solids. Beside the white of egg, it abounds in the serum of blood, the vitreous and crystalline humours of the eye, and the fluid of dropsy. Fourcroy claims to himself the honour of having discovered it in the green feculæ of plants in general, particularly in those of the cruciform order, in very young ones, and in the fresh shoots of trees, though Rouelle appears to have detected it there long before. Vauquelin says it exists also in the mineral water of Plombieres. Mr. Seguin has found it in remarkable quantity in such vegetables as ferment without yeast, and afford a vinous liquor; and from a series of experiments he infers that albumen is the true principle of fermentation, and that its action is more powerful in proportion to its solubility, three different degrees of which he found it to possess. The chief characteristic of albumen is its coagulability by the action of heat. If the white of an egg be exposed to a heat of about 134° F. white fibres begin to appear in it, and at 160° it coagulates into a solid mass. In a heat not exceeding 212o it dries, shrinks, and assumes the appearance of horn. It is soluble in cold water before it has been coagulated, but not after; and when diluted with a very large portion, it does not coagulate easily. dissolve as the caloric which separated the particles of acid and base escapes, or as the temperature falls. A solution containing infusion of galls, and tannin. The acids and metallic oxides coagulate albumen On the addition of concentrated sulphuric acid, it becomes black, and exhales a nauseous smell. Strong muriatic acid gives a violet tinge to the coagulum, and at length becomes saturated with ammonia. Nitric acid, at 70° F. disengages from it abundance of azotic gas; and if the heat be increased prussic acid is formed, after which carbonic acid and carburetted hy. drogen are evolved, and the residue consists of water containing a little oxalic acid, and covered with a lemon coloured fat oil. If dry potash or soda be triturated with albumen, either liquid or solid, ammoniacal gas is evolved, and the cal. cination of the residuum yields an alkaline prussiate. On exposure to the atmosphere in a moist state, albumen passes at once to the state of putrefaction. * Solid albumen may be obtained by agitating white of egg with ten or twelve times its weight of alcohol. This seizes the water which held the albumen in solution; and this substance is precipitated under the form of white flocks or filaments, which cohesive attraction renders insoluble, and which consequently may be freely washed with water. Albumen thus obtained is like fibrin, solid, white, insipid, inodorous, denser than water, and without action on vegetable colours. It dissolves in potash and soda more easily than fibrin; but in acetic acid and ammonia with more difficulty. When these two animal principles are separately dissolved in potash, muriatic acid added to the albuminous does not disturb the solution, but it produces a cloud in the other. Fourcroy and several other chemists have ascribed the characteristic coagulation of albumen by heat to its oxygenation. But cohesive attraction is the real cause of the phenomenon. In proportion as the temperature rises, the particles of water and albumen recede from each other, their affinity diminishes, and then the albumen precipitates. However, by uniting albumen with a large quantity of water, we diminish its coagulating property to such a degree, that heat renders the solution merely opalescent. A new-laid egg yields a soft coagulum by boiling; but when, by keeping, a portion of the water has transuded so as to leave a void space within the shell, the concentrated albumen affords a firm coagulum. An analogous phenomenon is exhibited by acetate of alumina, a solution of which, being heated, gives a precipitate in flakes, which re TO 1 coagulum; but when it contains only it gives a glairy liquid. One thousandth part, however, on applying heat, occasions opalescence. Putrid white of egg, and the pus of ulcers, have a similar smell. According to Dr. Bostock, a drop of a 1 saturated solution of corrosive sublimate let fall into water containing 보임이 of albumen, occasions a milkiness and curdy precipitate. On adding a slight excess of the mercurial solution to the albuminous liquid, and applying heat, the precipitate which falls, being dried, contains in every 7 parts, 5 of albumen. Hence that salt is the most delicate test of this animal product. The yellow pitchy precipitate occasioned by tannin, is brittle when dried, and not liable to putrefaction. But tannin, or infusion of galls, is a much nicer test of gelatin than of albumen. The cohesive attraction of coagulated albumen makes it resist putrefaction. In this state it may be kept for weeks under water without suffering change. By long digestion in weak nitric acid, albumen seems convertible into gelatin. By the analysis of Gay-Lussac and Thenard, 100 parts of albumen are formed of 52.883 carbon, 23.872 oxygen, 7.540 hydrogen, 15.705 nitrogen; or, in other terms, of 52.883 carbon, 27.127 oxygen and hydrogen, in the proportions for constituting water, 15.705 nitrogen, and 4.285 hydrogen in excess. The negative pole of a voltaic pile in high activity vity coa coagulates albumen; but if the pile be feeble, coagulation goes on only at the positive surface. Albumen, in such a state of concentration as it exists in serum of blood, can dissolve some metallic oxides, particularly the protoxide of iron. Orfila has found white of egg to be the best antidote to the poisoning effects of corrosive sublimate on the human stomach. As albumen occasions precipitates with the solutions of almost every metallic salt, probably it may act beneficially against other species of mineral poison.* From its coagulability albumen is of great use in clarifying liquids. See CLARIFICATION. It is likewise remarkable for the property of rendering leather supple, for which purpose a solution of whites of eggs in water is used by leather-dressers; and hence Dr. Lobb of Yeovil in Somersetshire was induced to employ this solution in cases of contraction and rigidity of the tendons, and derived from it apparent success. Whites of eggs beaten in a basin with a lump of alum, till they coagulate, form the alum curd of Riverius, or alum cataplasm of the London Pharmacopeia, used to remove inflammations of the eyes. * ALBURNUM. The interior white bark of trees.* * ALCARRAZAS. A species of porous pottery made in Spain, for the purpose of cooling water by its transudation and copious evaporation from the sides of the vessel. M. Darcet gives the following as the analysis of the clay which is employed for the purpose: 60 calcareous earth, mixed with alumina and a little peroxide of iron, and 36 of siliceous earth, mixed with a little alumina. In working up the earths with water, a quantity of salt is added, and dried in it. The pieces are only half baked.* * ALCHEMY. A title of dignity, given in the dark ages, by the adepts, to the mystical art by which they professed to find the philosopher's stone, that was to transmute base metals into gold, and prepare the elixir of life. Though avarice, fraud, and folly were their motives, yet their experimental researches were instrumental in promoting the progress of che mical discovery. Hence, in particular, metallic pharmacy derived its origin.* great deal of wine is made, particularly at the commencement of the vintage, that is too weak to be a saleable commodity, it is a common practice to subject this wine to distillation, in order to draw off the spirit; and as the essential oil that rises in this process is of a more pleasant flavour than that of malt or molasses, the French brandies are preferred to any other; though even in the flavour of these there is a difference, according to the wine from which they are produced. In the West Indies a spirit is obtained from the juice of the sugar-cane, which is highly impregnated with its essential oil, and well known by the name of rum. The distillers in this country use grain, or molasses, whence they distinguish the products by the name of malt spirits, and molasses spirits. It is said that a very good spirit may be extracted from the husks of gooseberries or currants, after wine has been made from them. As the process of malting developes the saccharine principle of grain, it would appear to render it fitter for the purpose; though it is the common practice to use about three parts of raw grain with one of malt. For this, two reasons may be assign ALCOHOL. This term is applied in stricted by using raw grain the expense of ness only to the pure spirit obtainable by distillation and subsequent rectification from all liquids that have undergone vinous fermentation, and from none but such as are susceptible of it. But it is commonly used to signify this spirit more or less imperfectly freed from water, in the state in which it is usually met with in the shops, and in which, as it was first obtained from the juice of the grape, it was long distinguished by the name of spirit of wine. At present it is extracted chiefly from grain or molasses in Europe, and from the juice of the sugar-cane in the West Indies; and in the diluted state in which it commonly occurs in trade, constitutes the basis of the several spirituous liquors called brandy, rum, gin, whiskey, and cordials, however variously denominated or disguised. As we are not able to compound alcohol immediately from its ultimate constituents, we have recourse to the process of fermentation, by which its principles are first extricated from the substances in which they were combined, and then united into a new compound; to distillation, by which this new compound, the alcohol is separated in a state of dilution with water, and contaminated with essential oil; and to rectification, by which it is ultimately freed from these. It appears to be essential to the fermentation of alcohol, that the fermenting fluid should contain saccharine matter, which is indispensable to that species of fermenation called vinous. In France, where a malting is saved, as well as the duty on malt; and the process of malting requires some nicety of attention, since, if it be carried too far, part of the saccharine matter is lost, and if it be stopped too soon, this matter will not be wholly developed. Besides, if the malt be dried too quickly, or by an unequal heat, the spirit it yields will be less in quantity, and more unpleasant in flavour. Another object of economical consideration is, what grain will afford the most spirit in proportion to its price, as well as the best in quality. Barley appears to produce less spirit than wheat; and if three parts of raw wheat be mixed with one of malted barley, the produce is said to be particularly fine. This is the practice of the distillers in Holland for producing a spirit of the finest quality; but in England they are expressly prohibited from using more than one part of wheat to two of other grain. Rye, however, affords still more spirit than wheat. * The practice with the distillers in Scotland is to use one part of malted with from four to nine parts of unmalted grain. This mixture yields an equal quantity of spirit, and at a much cheaper rate than when the former proportions are taken.* Whatever be the grain employed, it may be coarsely ground, and then mixed carefully with a little cold water, to prevent its running into lumps; water about 90o F. may then be added, till it is sufficiently diluted; and, lastly, a sufficient quantity of yeast. The whole is then to be allow ed to ferment in a covered vessel, to which, however, the air can have access. Attention must be paid to the temperature; for if it exceed 77° F. the fermentation will be too rapid; if it be below 60°, the fermentation will cease.† The mean between these will generally be found most favourable. In this country it is the more common practice to inash the grain as for brewing malt liquors, and boil the wort. But in whichever way it be prepared, or if the wash, so the liquor intended for distillation is called, be made from molasses and water, due attention must be paid to the fermentation, that it be continued till the liquor grows fine, and pungent to the taste, which will generally be about the third day, but not so long as to permit the acetous fermentation to commence. In this state the wash is to be committed to the still, of which, including the head, it should occupy at least threefourths; and distilled with a gentle heat as long as any spirit comes over, which will be till about half the wash is consumed. The more slowly the distillation is conducted, the less will the product be contaminated with essential oil, and the less danger will there be of empyreuma. A great saving of time and fuel, however, may be obtained by making the still very broad and shallow, and contriving a free exit for the steam. This has been carried to such a pitch in Scotland, that a still measuring 43 gallons, and containing 16 gallons of wash, has been charged and worked no less than four hundred and eighty times in the space of twenty-four hours. This would be incredible, were it not established by unquestionable evidence. See LABORATORY, article STILL. spirituous wines of France, those of Languedoc, Guienne, and Rousillon, yield, according to Chaptal, from 20 to 25 gallons of excellent brandy from 100; but those of Burgundy and Champagne much less. Brisk wines, containing much carbonic acid, from the fermentation having been stopped at an early period, yield the least spirit. The spirit thus obtained ought to be colourless, and free from any disagreeable flavour; and in this state it is fittest for pharmaceutical purposes, or the extraction of tinctures. But for ordinary sale something more is required. The brandy of France, which is most in esteem here, though perfectly colourless when first made, and often preserved so for use in that country, by being kept in glass or stone bottles, is put into new oak casks for exportation, whence it soon acquires an amber colour, a peculiar flavour, and something like an unctuosity of consistence. As it is not only prized for these qualities, but they are commonly deemed essential to it, the English distiller imitates by design these accidental qualities. The most obvious and natural method of doing this would be by impregnating a pure spirit with the extractive, resinous, and colouring matter of oak shavings; but other modes have been contrived. The dulcified spirit of nitre, as it is called, is commonly used to give the flavour; and catechu, or burnt sugar, to impart the desired colour. A French writer has recommended three ounces and a half of finely powered charcoal, and four ounces and a half of ground rice, to be digested for a fortnight in a quart of malt spirit. The finest gin is said to be made in Holland, from a spirit drawn from wheat mix * The above wonderful rapidity of dis-ed with a third or fourth part of malted tillation has now ceased, since the excise duties have been levied or the quantity of spirit produced, and not, as formerly, by the size of the still. Hence, too, the spirit is probably improved in flavour.* The first product, technically termed low wine, is again to be subjected to distillation, the latter portions of what comes over, called faints, being set apart to put into the wash still at some future operation. Thus a large portion of the watery part is left behind. This second product, termed raw spirit, being distilled again, is called rectified spirit. It is calculated, that a hundred gallons of malt or corn wash will not produce above twenty of spirit, containing 60 parts of alcohol to 50 of water; the same of cyder wash, 15 gallons; and of molasses wash, 22 gallons. The most † This is a mistake; fermentation will go on very slowly 10 degrees lower. barley, and twice rectified over juniper berries; but in general, rye meal is used instead of wheat. They pay so much regard to the water employed, that many send vessels to fetch it on purpose from the Meuse; but all use the softest and clearest river water they can get. In England it is the common practice to add oil of turpentine, in the proportion of two ounces to ten gallons of raw spirit, with three handfuls of bay salt, and draw off till the faints begin to rise. But corn or molasses spirit is flavoured likewise by a variety of aromatics, with or without sugar, to please different palates; all of which are included under the general technical term of compounds or cordials. Other articles have been employed, though not generally, for the fabrication of spirit, as carrots and potatoes; and we are lately informed by Professor Proust, that from the fruit of the carob tree he To obtain pure alcohol, different processes have been recommended; but the purest rectified spirit obtained as above described, being that which is least contaminated with foreign matter, should be employed. Rouelle recommends to draw off half the spirit in a water bath; to rectify this twice more, drawing off two-thirds each time; to add water to this alcohol, which will turn it milky by separating the essental oil remaining in it; to distil the spirit from this water; and finally rectify it by one more distillation. Baumé sets apart the first running, when about a fourth is come over, and continues the distillation till he has drawn off about as much more, or till the liquor runs off milky. The last running he puts into the still again, and mixes the first half of what comes over with the preceding first product. This process is again repeated, and all the first products being mixed together, are distilled afresh. When about half the liquor is come over, this is to be set apart as pure alcohol. Alcohol in this state, however, is not so pure as when, to use the language of the old chemists, it has been dephlegmated, or still further freed from water, by means of some alkaline salt. Boerhaave recommended, for this purpose, the muriate of soda, deprived of its water of crystallization by heat, and added hot to the spirit. But the subcarbonate of potash is preferable. About a third of the weight of the alcohol should be added to it in a glass vessel, well shaken, and then suffered to subside. The salt will be moistened by the water absorbed from the alcohol; which being decanted, more of the salt is to be added, and this is to be continued till the salt falls dry to the bottom of the vessel. The alcohol in this state will be reddened by a portion of the pure potash, which it will hold in solution, from which it must be freed by distillation in a water bath. Dry muriate of lime may be substituted advantageously for the alkali. As alcohol is much lighter than water, its specific gravity is adopted as the test of its purity. Fourcroy considers it as rectified to the highest point when its specific gravity is 829, that of water being 1000; and perhaps this is nearly as far as it can be carried by the process of Rouelle or Baumé simply. Mr. Bories found the first measure that came over from twenty of spirit at 836 to be 820, at the temperature of 71° F. Sir Charles Blagden, by the addition of alkali, brought it to 813, at 60° F. Chaussier professes to have reduced it to 798; but he he gives 998.35 as the specific gravity of water. Lowitz asserts, that he has obtained it at 791, by adding as much alkali as nearly to absorb the spirit; but the temperature is not indicated. In the shops it is about 835 or 840; according to the London College it should be 815. It is by no means an easy undertaking to determine the strength or relative value of spirits, even with sufficient accuracy for commercial purposes. The following requisites must be obtained before this can be well done: the specific gravity of a certain number of mixtures of alcohol and water must be taken so near each other, as that the intermediate specific gravities may not perceptibly differ from those deduced from the supposition of a mere mixture of the fluids; the expansions of variations of specific gravity in these mixtures must be determined at different temperatures; some easy method must be contrived of determining the presence and quantity of saccharine or oleaginous matter which the spirit may hold in solution, and the effect of such solution on the specific gravity; and lastly, the specific gravity of the fluid must be ascertained by a proper floating instrument with a graduated stem, or set of weights; or, which may be more convenient, with both. The strength of brandies in commerce is judged by the phial, or by burning. The phial proof consists in agitating the spirit in a bottle, and observing the form and magnitude of the bubbles that collect round the edge of the liquor, technically termed the bead, which are larger the stronger the spirit. These probably depend on the solution of resinous matter from the cask, which is taken up in greater quantities, the stronger the spirit. It is not difficult, however, to produce this appearance by various simple additions to weak spirit. The proof by burning is also fallacious; because the magnitude of the flame, and quantity of residue, in the same spirit, vary greatly with the form of the vessel it is burned in. If the vessel be kept cool, or suffered to become hot, if it be deeper or shallower, the results will not be the same in each case. not follow, however, but that manufacturers and others may in many instances receive considerable information from these signs, in circumstances exactly alike, and in the course of operations wherein it would be inconvenient to recur continually to experiments of specific gravity. It does The importance of this object, as well for the purposes of revenue as of commerce, induced the British government to employ Dr. Blagden, now Sir Charles, to institute a very minute and accurate series of experiments. These may be considered as fundamental results; for which reason, I shall give a summary of them in this |