Imatges de pÓgina

measures are to be taken. The 100 measures are then made up by the addition of water, and is then realy for use, following the method before stated.

The alkalies are four in number, namely, ammonia (or volatile alkali), potass (or vegetable alkali), soda (or mineral alkali), and lithia ; which lasi is of so little importance that we shall not treat of it here.

The combinations of these alkalies with the various acids, whenever they form compounds of any im. portance, will be noticed.

Ammonia, or Spirits of Hartshorn, or Volatile Alkali, in its uncombined form, is an elastic gaseous body, having a very pungent and suffocating odour, destroys animal life, converts the yellow of turmerie paper to a brown, which, from the volatility of the alkali, is again restored by a gentle heat to its original colour. This gas is rapidly absorbed by water, which takes into solition about 780 times its Folume, forining the liquid ammonia, or what is commonly called hartshorn. Ammonia is liberated whenever any of the compounds of this alkali are acted upon by potass, soda, lime, and many other alkaline earths. Live, from its being the most economical, is generally employed ; the best proportion for its preparations are equal weights of sal ammoniac (muriate of ammonia), and fresh slaked lime. When these are introduced into a retort, and heat applied, ammonia is liberated in the gaseous form, and is conducted by a Wetter's safety tube into a vessel of water, by which the gas is instantly absorbed. Muriate of lime remains in the retort ; sometimes water is added to the mixture, and then distilled. As thus obtained, it has a specutic gravity of 930 or .940, water being equal to 1.000. The most concentrated solution of ammonia has the specific gravity •875.

Carbonate of Ammonia, or Volatile Salt, or Subcarbonate of Ammonia. – This salt, which is very much employed in various processes of the arts, was formerly obtained by the action of chalk (carbonate of lime) upon muriate of ammonia ; a double decomposition takes place. Carbonic acid and ammonia are sublimei in vapour, and muriate of line remains in the vessel. A much less expensive process is, however, now followed, namely, from the waste gas liquors obtained in the purification of coal gas; these are evaporatri. and the black impure sulphuric acid added. By this means a sulphate of ammonia is formed, and the carbonate procured from it by the action of powdered chalk, as in the former process.

Its uses are principally in forming other compounds of ammonia, as smelling salts ; and it is likewise employed rather extensively by pastry.cooks for making light pastry, which is caused by the volatile carbonate of ammonia escaping and raising up the pastry by the heat of the oven. It is entirely dissipated during the baking, so that no ill effect can arise from its use.

Both this compound and the preceding act as violent stimulants on the animal system.

Muriate of Ammonin, or Sal Ammoniac, was formerly brought to this country from Egypt, where it was procured by submitting the soot of canels' dung (there employed for fuel) to sublimation in closer vessels; it is, however, at present manufactured in very large quantities in this country in a variety of ways. "The most economical processes are either submitting sulphate of ammonia mixed intimatels with niuriate of soda (sea salt) to sublimation, or by substituting the bittern of sea water, which consists chiefly of muriate of magnesia, for the sea salt. In the first process a sulphate of soda is formed, and the muriate of ammonia, which, being volatile, rises in the vaporous form, and is condensed in the cool parts of the apparatus ; in the latter process a sulphate of magnesia (Epsom salts) results. It is generally from this salt (muriate of ammonia) that the liquid ammonia is manufactured ; it is also employed in tinning and soldering, to preserve the metals from oxidation. It is a semi-transparent, tough salt, having an acril and cool taste, and is usually met with in the form of hemispherical masses. Sal ammoniac is made at Calcutta, and is thence exported to Great Britain, the United States, and the Arabian and Persian gulis. In 1924-25 the exports amounted to 114 tons.

Sulphate of Ammonia. - The preparation of the sulphate has been alrcady given under the head of ammonia ; it is employed in the manntacture both of the carbonate and muriate.

Acetate of Ammonia. - The spirit of Mindererus is obtained by acting upon the carbonate of ammonia by acetic acic; the carbonic acid escapes with effervescence, and an acetate of ammonia is formed; it is employed in medicine as a febrifuge,

All ihese salts of ammonia have the following properties ; – they are volatile at a low red heat ; the fixed alkalies decompose them, combining with their acid, and the ammonia is liberated.

When combined with a fixed acid, such as the boracic or phosphoric, they are decomposed, the am. monia alone being volatilised, and the acid remaining pure. This process was described for obtaining pure phosphoric acid.

Potass, or Vegetable Alkali. - The original source of this alkali is in the vegetable kingdom, whence is derived its name of vegetable alkali. When wood is burnt, and the ashes lixiviated with water, boileil, strained, and evaporated to dryness, an intensely alkaline mass is obtained, which is known by the name of potash, from this process being conducted in iron pots. It is then removed to a reverberatory furnace, and submitted to heat, and a current of air. This burns out extractive matter and other impurities, and the salt assumes a pearly white colour, and is hence called pearlashes. Care should be taken, during this process, that the potashes do not enter into fusion, as this would destroy the full effect of the operation,

Pearlashes. - Pearlashes generally contain about from 60 to 83 or 84 per cent. of pure carbonate of potass. Its uses in manufactures are numerous and important. It is employed in making Aint-gliss, of which it constitutes about one sixth of the materials employed, in soap-making, especially for the soils kinds of soap; for this purpose, however, it is first rendered caustic by means of lime. 'In the rectifi. cation of spirits large quantities are employed to combine with the water previously in union with the spirit.

Subcarbonate of Polass,or Salt of Tartar, is used in preparing the subcarbonate of potass of the Pharmacopeia (carbonate of potass of the chemical nomenclature), and likewise in rendering hard spring waters soft, and in cleansing substances from grease: it is sometimes called salt of wormwood. When made by the detlagration of two parts of tartar of argol and one of nitre, it is called black flux, and is used extensively in metallurgic operations.

From the subcarbonate of potash the pure and uncombined potass is obtained, by adding an equal weight of fresh burnt lime, previously slaked, and boiling them with half their weight of water. By this process the lime combines with the carbonic acid, and the potass remains in solution in its caustic siate; by boiling the clear solution rapidly in iron vessels, and submitting it to fusion, we obtain the fused potass.

If it be required perfectly pure for chemical purposes, it is necessary to evaporate in silver vessels, and dissolve in strong alcohol

. This takes up the pure potass, and leaves any portion of the subcarbonate that may not have been acted upon by the lime; then the alcohol is to be distilled off, and the potass fused at a red heat, and poured out in its liquid state on a cold slab. Asthus procured, it is a white, brittle mass, highly deliquescent, absorbing moisture and carbonic acid rapidly from the atmosphere. When evapor. ate in iron vessels it has a dirty colour, and lets fall a quantity of oxide of iron, when dissolved in water from its having acted upon the iron boilers.

Potass acts with great rapidity upon animal substances, destroying their texture, and is on this account employed as a caustic, and was formerly called lapis infernalis.

Carbonale (or, in the chemical nomenclature, Bicarbonate) of Polass, is prepared by passing carbonie acid gas through a solution of the subcarbonate: and evaporating at a temperature below 21:20, and cryse tallising. It is used in making effervescing draughts. It loses one proportion of its carbonic acid when heated, and is converted into the subcarbonate.

Sulphate of Potuss, « Sal Poiychrest, or l'itriolated Tartar, is obtained by submitting the salt, which remains after the manufacture of nitric acid from nitre and sulphuric acid, to a red hcat, or by neutralising the excess of acid contained in that salt by subcarbonate of potass.

Bisulphate of Potass, or Sal Enirum. - This is the salt mentioned above, as the residue from the process for obtaining nitric acid. It is employed, in very large quantities, in the manufacture of alum; also in tinning iron for pickling, as it is termed; it is sometimes also used as a flux.

Nitrate of Potash, Nitre, or Saltpetre. -- This salt, which is of so much importance in every branch of the arts, is found native in many parts of the world, especially in the East Indies. It is obtained from soils composed of decomposing granite, the felspar of which gives rise, as is supposed to the potass. The nitric acid is not so easily accounted for, except it is by a union of the nitrogen and oxygen gases in the atmosphere taking place in those hot climates ; for, from authenticated accounts, no decaying animal or vegetable matter exists in the nitre districts of India. By lixiviation with water the nitre is dissolved from the soil, which is again throun out into the air, to be wished the following year; so that it is formed continually. These lixiviations are then evaporated; and when of a certain strength, a quantity of common salt separates, which is removed as it falls; and the nitre is then crystallised and imported to this country, always containing a certain quantity of impurities, which are deductes in the purchase of large quantities of the article, being te med its refraction. It is generally used for the manufacture of gunpowder and pure nitric acid, refined or re-crystallised.

Nitre may be also made artificially, in beds of decaying vegetable or animal substances, mixed with old mortar, or other refuse calcareous earth ; these are watered occasionally, too much moisture being hurtful; after a certain period, depending on the rapidity with which the process has gone on, the whole is submitted to lixiviation together with wood-ashes, which contain subcarbonate of potass, and which de composes any nitrale of liae formed, of which there is generally a considerable quantity: Aiter the lixiviation is complete, which takes some time, the solution is separated and boiled down; the sait separates as in the other process, and the nitre is then crystallised. It was from this source that the whole of the nitre, nearly, employed by the French during the long protracted war with the continental powers was obtained.

Nitre has a cold, penetrating, and nauseous taste; enters into igeous fusion at a gentle heat, and is the moulded into round cakes called sal prunella, 'It is employed in the manufacture of nitric acid ; of gunpowder, which is composed of 75 parts by weight of nitre, 18 of charcoal, and 9 of sulphur (the nitre for this purpose should be of great pirity); and in the manufacture of oil of vitriol: as a flux it is ove of the most powerful we possp58 ; it is also used for the preservation of animal food, and in making fri. gorific mixtures : 1 oz. of nitre dissolved in 5 oz. of water lowers its temperature i5 degrees of fahrenheit's thermometer. (See SALTPETRE.)

Oxalate and Binoralate of Potass. - The binoxalate of potass, or salt of lemon, or sorrel, by both which 12l names it is very commonly known, is procured from the juice of the common sorrel (Rumex Acetosa), or the wood sorrel (Oxalis Acetosella), by crystallisation, after the feculent ir atter has been separated hy standing a few days. Its chief uses are, in removing ink spots or iron moulds; and also as a refreshing beverage when mixed with surar and water.

The neutral oxalate is obtained from this salt hy combining the excess of acid which it contains with a solution of subcarbonate of potass. Is very niuch used in chemistry, as the best test of the presence of lime.

Tartrate and Bitartrate of Potass. -- Bitartrate of potass, or cream of tartar, is, when in its crude and impure state. called argol, and is deposited in the interior of wine casks during fermentation, and from this source the whole of the cream of tartar is obtained. It is generally of a very dark brown colour, but may be purified and rendered perfectly white by solution and crystallisation. It is employed very extensively in dyeing, hat-making, and in the preparation of tartaric acid, and many of the compounds of tartaric acid, as tartar emetic, soluble tartar (tartrate of potass): when heated to redness it is converted into carbonate of potass and charcoal ; mixed with half its weight of nitre and thrown into a red hot crucible it forms the black fux, and with its own weight of nitre the white flux, both of which are very much employed in metallurgic operations. The tartrate is made by the addition of subcarbonate of potass to a solution of the bitartrate until perfectly neutral: it is used in medicine as a mild purgative.

Forrocyancta or Prussiate of Potass. -- This salt is obtained by the action of subcarbonate of potass, at a low red heat, upon refuse animal matter, such as hoofs, horns, skin, &c., in the proportion of two of subcarbonate to four or five of the animal matter. But the process recommended by M. Gautier is preferable; he finds, that when animal matter is heated with nítre, it yields a much larger quantity of ire ferroprussiate than wben either potass or subcarbonate of potass are employed; the proportions he finds most economical are, 1 part by weight of nitre, 3 parts of dry blood, and iron scales or tilings equal to a hitieth of the blood employed.

The coagulum of blood is mixed intimately with the nitre and iron flings, and dried by exposure to the air ; they are then submitted to a very low red heat, in deep iron cylinders, as long as vapours continue to be liberated ; when cold, the contents are dissolved in 12 or 15 times their weight and strained. On evaporation till of the specific gravity 1•284, and allowing it to cool, a large quantity of bicarbonate of potası crystallises, and by further evaporation till of the specific gravity 1:306, the ferroprussiate of potasz crystallises on cooling. This is to be recrystallised. It is a beautiful yellow salt, very tough, having a tenacity similar to spermaceti, and is decomposed at a red heat. It is employed very extensively in dyeing blues, and in calico printing ; also in the minufacture of Prussian blue, which is a compound of the ferroprussic acid an ioxide of iron, prepared by adding ! part of the ferroprussiate of potass dissolved in water, to i part of copperas, and 4 parts of alum in solution.

Chromate of Potass. This salt is obtained from the native chromate of iron by the action of nitre at a full red heat in equal proportions. By solution, filtration, and evaporation, a beautiful lemon-yellow coloured salt results. It is very much employed in dyeing, calico printing, and calico making, from its producing bright yellow precipitates with solutions of lead.

Bichromate of Potass -- is prepared from the above-mentioned salt, by the addition of nitric acid to the yellow solution obtained from the heated mass by the action of water ; on evaporating this, a dark red coloured salt crystallises, which is the bichromate. This is also very largely employed by the calico printers, and when mixed in solution with nitric acid, possesses the property of destroying vegetable colours ; on this account it is of great importance, as it at the same time removes a vegetable colour, and forms a base for a yellow dye.

Chlorate or Hyperoxymuriate of Potass. — The preparation of this salt is attended with some little difficulty, and requires a great deal of nicety. It is obtained by passing a current of chlorine gas through a solution of caustic potass ; then boiling and evaporating ; the first salt that separates is the chlorate of potass; and hy further evaporation, muriate of potass is obtained. It is used in making matches for instantaneous light boxes, which are prepared by brst dipping the wood in melted sulphur, and then into a thin paste, fonned or 3 parts chlorate of potass, 2 paris starch, and a little vermilion ; with sulphur it forms a very explosive compound, generally employed for filling the percussion caps of fowling picces.

Soda, or Mineral Alkali. - The sources of this alkali in nature are various. It is obtained in combination with carbonic acid, when plants which grow by the sea-side are burnt. The ashes thus obtained are called barilla and kelp: and also in some countries it is found as an efflorescence upon the suriace of the earth, and is called nitrum or natron ; this occurs particularly in Egypt and South America. Trona is also another native carbonate of soda, and is exported from Tripoli. In combination with muriatic a id it is also found in immense abundance, forming the rock salt, and sea salt or muriate of soda. It is obtained from the carbonate exactly in the same way as potass is obtained from its carbonate, namely, by boiling it with fresh burnt lime previously slaked, decanting the clear solution, and evaporating and fusing. It is a wbite brittle substance, and bj exposure to the air becomes converted into a dry carbo

Its uses in the arts and manufactures are of considerable importance. In snap-making it is


employed in very large quantities, and for this purpose is generally procured from barilla of kelp, by mixing them with lime, and by the infusion of water procuring a caustic soda ley; this is mixed with oil and fatty matters in various proportions, and boiled ; the saponification of the fatty matter takes place, and the soap formed rises to the surface; the ley is then drawn from beneath, and fresh leys added, until the soap is completely free from oil; it is then allowed to dry. Soda is also employed in the manu. facture of plate, crown, and bottle glass, though for this purpose it is generally in the form of carbone or sulphate.

Subcarbonate of Soda. (In the chemical nomenclature it is called carbonate.) - This is generally pre. pared from barilla, which contains about from 16 to 24 per cent. Barilla is procured by incinerating the salsola soda, and other sea-side plants; it is made in large quantities on the coast of Spain. Kelp is another impure carbonate of soda, but does not contain more than 4 or 5 per cent.; it is the ashes obtained from sea weeds by incineration, and is made on the northern shores of Scotland. From these, the crystallised carbonate (or subcarbonate, as it is more frequently called) is made by the addition of a small quantity of water, boiling, straining, evaporating, and skimming off the common salt as it forms on the surface on cooling, the subcarbonate of soda crystallises. Another method is by heating the sulphate of soda with carbonate of lime and charcoal, and then dissolving out the soluble carbonate; also, by the action of carbonate of potass (pearlash) upon solutions of sea salt. — (See BARILLA and KELP.)

Bicarbonate of Soda -- is procured by driving a current of carbonic acid gas through solutions of the carbonate, and then evaporating at a temperature below 2120 Fahrenheit, it is chietiy employed in making soda water powders. This is the carbonate of soda of the Pharmacopæia. By the application of a red heat it loses carbonic acid, and is converted into the subcarbonate.

Sulphate of Soda, or Glauber Salts. – This salt, which has received the name of Glauber, from its dis. coverer, is the residue of a great many chemical processes; for instance, when muriate of soda is arted upon by oil of vitriol, muriatic acid and sulphate of soda result; in making chlorine gas for the manu. facture of the chloride of lime, or bleaching powder, sulphate of soda and sulphate of manganese result; the materials employed being sea salt, sulphuric acid (oil of vitriol), and black oxide of manganese: also, in the preparation of acetic acid from the acetate of soda, and in the preparation of muriate of ammonia from sea salt and sulphate of ammonia. Sulphate of soda is a colourless, transparent salt, e doresces readily when exposed to the air, and becomes converted into a dry powder; it has a cold, bitter taste. It is used for the preparation of carbonate of soda, and as a medicine. It is found native in soine countries, particularly in Persia and South America -- frequently as an efflorescence upon new walls.

Nitrate of Soda. - This salt is found native in some parts of the East Indies, and is called, from its square forin, cubic nitre; it is, however, very little used.

Muriate of Soda, or Sea Salt. -- This compound is found in immense quantities in the earth, and is called from this circumstance rock salt, or sal gem. The mines of Cheshire and Droitwich, in this country, and those in Poland, Hungary, and Spain, and many others, afford immense quantities of this compound. It is also obtained by the evaporation of sea water, both spontaneously in pits formed for the purpose, and in large iron boilers; the uncrystallisable fluid is called the bittern; basket salt is made by placing the salt after: evaporation in conical baskets, and passing through it a saturated solution of salt, which dissolves and carries off the muriate of magnesia or lime. Pure salt should not become moist by exposure to the air; it decrepitates when heated; it is employed for the preparation of muriatic acid, carbonate of soda, muriate of ammonia, and many other operations; also in glazing stone-ware, pottery, &c. ; and from its great antiseptic properties, is used largely for the preservation of animal fod; as a tlux also in metallurgy.

Borate of Soda, or Borar. This salt is found in 'Thibet and Persia, deposited from saline lakes; it is called tincal, and is imported into this country, where it is puritied by solution, the fatty matter with which the tincal is always coated being removed, and the solution evaporated and crystallised, its principal uses are as a flux, from its acting very powerfully upon earthy substances.

ALKANET, or ANCHUSA (Ger. Orkanet ; Du. Ossetong ; Fr. Orcanette; It. Ancusa ; Sp. Arcaneta), a species of bugloss ( Anchusa tinctoria Lin). It has been cul. tivated in England ; but is found of the finest quality in Siberia, Spain, and more particularly in the South of France, in the vicinity of Montpelier. The roots of the plant are the only parts that are made use of. When in perfection, they are about the thickness of the finger, having a thick bark of a deep purplish red colour. This, when separated from the wbitish woody pith, imparts a fine deep red to alcohol, oils, wax, and all unctuous substances, To water it gives only a dull brownish hue. It is principally employed to tint wax, pomatum, and unguents, oils employed in the dress. ing of mahogany, rose-wood, &c. The alkanet brought from Constantinople yields a more beautiful but less permanent dye than that of France. -(Lewis's Mat. Med.; Magniem, Dictionnaire des Productions. )

The duty, which was previously very oppressive, was reduced in 1832 to 25. a cwt. ; and by the tariff of last year (1842) to 1s. a cwt. The imports are inconsiderable. The price varies from 27s. to 325. a cut.

ALLOWANCES, TARES, &c. In selling goods, or in paying duties upon them, certain deductions are made from their weights, depending on the nature of the packages in which they are inclosed, and which are regulated in most instances by the custom of merchants, and the rules laid down by public offices. These allowances, as they are termed, are distinguished by the epithets Draft, Tare, Tret, and Cloff.

Draft is a deduction from the original or gross weight of goods, and is subtracted before the tare is taken off.

Tare is an allowance for the weight of the bag, box, cask, or other package, in which goods are weighed.
Rral or open tare is the actual weight of the package.
Cristomary tare is, as its name implies, an established allowance for the weight of the package.
Computed tare is an estimated allowance agreed upon at the time.

Average tare is when a few packages only among several are weighed, their mean or average taken, and the rest tared accordingly.

Super-tare is an additional allowance, or tare, where the commodity or package exceeds a certain weight,

When tare is allowed, the remainder is called the nett weight; but if trett be allowed, it is called the sutile weight.

Trett is a deduction of 4 lbs. from every 104 lbs. of suttle weight.

This allowance, which is said to be tor dust or sand, or for the waste or wear of the commodity, was formerly made on most foreign articles sold by the pound avoirdupois ; but it is now nearly discontinued bg merchants, or else allowed in the price. It is wholly abolished at the East India warehouses in London ; and neither trett nor draft is allowed at the Cusiom-house.

Cla, or Clough, is another allowance that is nearly obsolete. It is stated in arithmetical books to be a deduction of 2 ibs, from every 3 cwt. of the second suitle; that is, the remainder after trett is subtracie

but merchants, at present, know cloff only as a small deduction, like draft, from the original weight, and this only from two or three articles. - (See kelly's Cambist, art.“ London.")

For an arcount of the tares and allowances at London, see TARE; for the tares and allowances at the great foreign trading towns, see their names.

ALMONDS (Ger. Mandeln; Du. Amandelen ; Fr. Amandes ; It. Mandorli; Sp. Almendra; Port. Amendo; Rus. Mindal; Lat. Amygılalæ amaræ, dulces), a kind of medicinal fruit, contained in a hard shell, that is enclosed in a tough sort of cotton skin. The tree (Amygdalus communis) which produces this fruit nearly resembles the peach both in leaves and blossoms ; it grows spontaneously only in warm countries, as Spain, and particularly Barbary. It Rowers early in the Spring, and produces fruit in August. Almonds are of two sorts, sweet and bitter. They are not distinguishable from each other but by the taste of the kernel or fruit. “The Valentia almond is sweet, large, and flat-pointed at one extremity, and compressed in the middle. The Italian almonds are not so sweet, smaller, and less . depressed in the middle. The Jordan almonds come from Malaga, and are the best sweet almonds brought to Eng. land. They are longer, flatter, less pointed at one end and less round at the other, and have a paler cuticle than those we have described. The sweet almonds are imported in mats, casks, and boxes; the bitter, which come chiefly from Mogadore, arrive in boxes.” -( Thomson's Dispensatory.)

Previously to 1932, almonds were grossly overtaxed; but the duties were then considerably reduced, and they were also still farther reduced in 1812. At an average of the years 1840 and 1811, the entries for home consumption amounted to 8,019 cwt. They are mostly imported from Spain and Northern Africa. The (1843) duties are, almonds, not Jordan or bitter, 16s.acut.; Jordan, 25$. per ditto ; bitter, 28. per ditto. Almonds were quoted in bond in London, in January 1843, Jordan (new), 155s, a cut. ; Valencia (sweet, shipped from Alicant,) 785. per ditto ; African bitter, 638. per ditto; African sweet, 468. to 478. per ditto.

ALOES (Du. Aloe ; Fr. Aloés ; Ger. and Lat. Aloe; Rus. Sabir; Sp. Aloè; Arab. Mucibar), a bitter, gummy, resinous, inspissated juice, obtained from the leaves of the plant of the same name.

There are four sorts of aloes met with in commerce ; viz. Socotrine, Hepatic, Caballine, and Cape.

1. Surotrine - so called from the island of Socotra, in the Indian Ocean, not very distant from Capo Guardafui, where the plant ( Aloe spicala), of which this species is the produce, grows abundantly. It is in pieces of a reddish brown colour, glossy as if vamishel, and in soine degree pellucid. When reduced to powder, it is of a bright golden colour. Its taste is extremely bitter; and it has a peculiar aromatic odour, not unlike that of the russet apple decaying. It softens in the hand, and is adhesive; yet is sufficiently pulverulent. It imported by way of Smyroa and Alexandria, in chests and casks, but is very scarce in England.

2. Hepatic. - The real hepatic aloes, so called from its liver colour, is believed to be the produce of the Aloe perfoliata, which grows in Yemen in Arabia, from which it is exported to Bombay, whence it finds way to Europe. It is duller in the colour, bitterer, and has a less pleasant aroma than the Soco. trine aloes, for which, however, it is sometimes substituted. Barbadoes aloes, which is often passed off for the hepatic, is the produce of the Aloe vulgaris. It is brought home in calabashes, or large gourd shells, containing from 60 to 70 lbs. It is duskier in its hue than the Bombay, or real hepatic aloes, and the taste is inore nauseous, and intensely bitter. The colour of the powder is a dull olive yellow.

3. Caballine or Horse Aloes seems to be merely the coarsest species or refuse of the Barbadoes alocs. It is used only in veterinary medicine; and is easily distinguished by its rank fatid smell.

4. Cape Aloes is the produce of the Aloe spicata, which is found in great abundance in the interior of the Cape colony, and in Melinda. The latter furnishes the greater part of the extract sold in Europe under the name of Socotrine aloes. The odour of the Cape aloes is stronger and more disagreeable than that of the Sucotripe ; they have, also, a yellower hue on the outside ; are less glossy, softer, and more pliable; the colour of the powder is more like that of gamboge than that of the true Socotrine aloes. (Ainslie's Mat. Indica; Thomson's Dispensatory and Mat. Modica.)

The entries of aloes for home consumption amounted, at an average of the years 1841 and 1842, to 170,750 lbs. a year. Previously to 1842 the duties were 2d. per lb. on those from a British possession, and sd. on those from a foreign country ; but they were then reduced to Id. and 2d. per lb.

ALOES-WOOD (Ger. Aloeholz; Du. Aloëhout, Paradyshout; Fr. Bois d'Aloés ; It. Legno di Aloe ; Sp. A'oè chino; Lat. Lignum Aloes; Sans. Aguru ; Malay, Agila ; Siam. Kisna), the produce of a large forest tree, to be found in most of the countries between China and India, from the 24th degree of north latitude to the equator.

It seems to be the result of a diseased action confined to a small part of a few trees, of which the rest of the wood is wholly valueless. It appears to be more or less frequent according to soil and climate, and from the same causes to differ materially in quality. It is produced both in the greatest quantity and perfection in the countries and islands on the east coast of the Gulf of Siam. This article is, in high repute for fumigations, and as incense, in all Hindu, Mohammedan, and Catholic countries. It formerly brought a very high price, being at one time reckoned nearly as valuable as gold. It is now comparatively cheap, though the finest specimens are still very dear. The accounts of this article in most books, even of good authority, are singularly contradictory and inaccurate. This is more surprising, as La Loubère has distinctly stated, that it consisted only of " certains endroits corrumpus dans des arbres d'une certaine espèce.' Toute arbre de cette espèce n'en a pas ; et ceux qui en ont, ne les ont pas tous en même endroit." (Royaume de Siam, t. i. p. 15. 12mo. ed.) The difficulty of finding the trees which happen to be diseased, and of getting at the diseased portion, has given rise to the fables that have been current as to its origin. The late Dr. Roxburgh introduced the tree which yields this production into the Botanical Garden at Calcutta, from the hills to the eastward of Sylhet, and described it under the name of Aquillaria Agalocha.

ALUM (Ger. Alaun ; Du. Aluin ; Fr. Alun ; It. Allume ; Sp. Allumbre; Rus. Kwasszë; Lat. Alumen ; Arab, Sheb), a salt of great importance in the arts, consisting of a ternary compound of aluminum, or pure argillaceous earth, potass, and sulphurie acid. Alum is sometimes found native; but by far the greater part of that which is met with in commerce is artificially prepared. The best alum is the Roman, or that which is manufactured near Civita Vecchia, in the Papal territory. It is in irregular,

octahedral, crystalline masses, about the size of a walnut, and is opaque, being covered on the surface with a farinaceous eflorescence. The Levant, or Roch alum, is in fragments, about the size of the former, but in which the chrystalline form is more obscure; it is externally of a dirty rose-colour, and internally exhibits the same tinge, but clearer. It is usually shipped for Europe from Smyrna ; but it was anciently made at Roccha, or Edessa, in Syria; and hence its name Roch alum. English alum is in large, irregular, semi-transparent, colourless masses, having a glassy fracture; not efflorescent, and considerably harder than the others. It is very inferior to either the Roman or Roch alum. The principal use of alum is in the art of dyeing, as a mordant for fixing and giving permanency to colours which otherwise would not adhere at all, or but for a very short time; but it is also used for a great variety of other purposes.

Beckmann has shown (History of Inventions, vol. i. art.“ Alum”) that the ancients were unacquainted with alum, and that the substance which they designated as such was merely vitriolic earth. It was first discovered by the Orientals, who established alum works in Syria in the thirteenth or fourteenth century. The oldest alum works in Europe were erected about the middle of the futeenth century. Towards the conclusion of the rcign of Queen Elizabeth, Sir Thomas Chaloner established the first alum work in England, in the vicinity of Whitby, in Yorkshire, where the principal works of the sort in this country are still carried on; the shipments of alum from Whitby in 1811 amounted to 3,237 tons. There is, also, a large alum work at Hurlett, near Paisley, the produce of which may be estimated at about 1,200 tons a year. Alum is largely manufactured in China, and is thence exported to all the western Asiatic countries. In 1837, 35,642 piculs (2,120 tons) were exported from Cantou.

AMBER (Ger. Bernstein ; Du. Barnsteen ; Da. Bernsteen, Rav.; Fr. Ambre jaune; It. Ambra gialla; Sp. Ambar ; Rus. Jantar ; Pol. Bursztyn; Lat. Succinum, Electrum), a brittle, light, hard substance, usually nearly transparent, sometimes nearly colourless, but commonly yellow, or even deep brown. It has considerable lustre. Specitic gravity 1.065. It is found in nodules or rounded masses, varying from the size of coarse sand to that of a man's hand. It is tasteless, without smell, except when pounded or heated, when it emits a fragrant odour. It is highly electric. Most authors assert that amber is bituminous; but Dr. Thomson states, that “it is undoubt. edly of a vegetable origin; and though it differs from resins in some of its properties, yet it agrees with them in so many others, that it may without impropriety be referred to them." --( Chemistry, vol. iv. p. 147. 5th ed.)

Pieces of amber occasionally enclose parts of toads and insects in their substance, which are beautifully preserved. It is principally found on the shores of Pomerania and Polish Prussia ; l»ut it is sometimes dug out of the earth in Ducal Prussia. It is also met with on the banks of the river Giaretta, in Sicily. Sometimes it is found on the cast coast of Britain, and in gravel pits round London. The largest mass of amber ever found was got near the surface of the ground in Lithuania. It weighs 18 lbs., and is preserved in the royal cabinet at Berlin. Most of the amber imported into this country comes from the Baltic, but a small quantity comes from Sicily. Amber was in very high estimation ainong the ancients, but is now comparatively neglected.

AMBER-GRIS, or AMBER-GREASE (Ger. Amber ; Du. Amber ; Fr. Amber. gris; It. Ambra-grigia : Sp. Ambar-gris; Lat. Ambra, Ambra grisea,) a solid, opaque, generally ash-coloured, fatty, inflammable substance, variegated like marble, remarkably light, rugged and uneven in its surface, and has a fragrant odour when heated; it does not effervesce with acids, melts freely over the fire into a kind of yellow resin, and is hardly soluble in spirit of wine. It is found on the sea-coast, or floating on the sea, near the coasts of India, Africa, and Brazil, usually in small pieces, but sometimes in masses of 50 or 100lbs. weight.“ Various opinions have been entertained respecting its origin. Some affirmed that it was the concrete juice of a tree, others thought it a bitumen ; but it is now considered as pretty well established that it is a concretion formed in the stomach or intestines of the Physeter macrocephalus, or spermaceti whale." --( Thomson's Chemistry.) Ambergris ought to be chosen in large pieces, of an agreeable odour, entirely grey on the outside, and grey with little black spots within. The purchaser should be very cautious, as this article is easily counterfeited with gums and other drugs.

AMETHYST (Ger. Amethyst ; Fr. Amethyste ; It. Amatista ; Sp. Ametisto; Lat. Amethystus), a precious stone, of which there are two species differing widely in quality and value.

The Oriental amethyst is a gem of the most perfect violet colour, and of extraordinary brilliancy and beauty. It is said to be as hard as the sapphire or ruby, with which it also corresponds in its form and specific gravity--(see SarPuRE), differing in colour merely. It has been met with in India, Persia, Siam, and other countries ; but it is exceedingly scarce.. That found in India is said by Pliny to be the best. (Principatum amethysti Indicæ tenent. - Nat. Hist. lib. xxxvii. cap. 9.) Mr. Mawe says he had rarely seen an oriental amethyst oftered for sale, unless small and inferior in colour. Mr. Hlupe, the author of Anastasius, had in his cabinet the finest gem of this sort in Europe. This exquisite specimen exceeds an inch in its greatest diameter; in daylight it exhibits the most beautiful violet colour, while by candlelight it is a decidei blue.

The Occidental amethyst is merely coloured crystal or quartz._" When perfect, its colour resembles that of the violet, or purple grape; but it not unfrequently happens that the linge is confined to one part of the stone only'

, while the other is left almost colourless. When it possesses à richness, clearness, and uniformity of hue, it is considered a gem of exquisite beauty; and as it occurs of considerable size, it is suited to all ornamental purposes. In specific gravity and hardness it bears no comparison with the oriental amethyst; it is also inferior in beauty and lustre; though I have often seen the common amethyst offered for sale as oriental. Brazil

, Siberia, and Ceylon produce very fine amethysts: they are found in rolled pieces in the alluvial soil, and finely crystallised in fissures of rock. From the first of those localities, they bave lately been imported in such quantities as considerably to diminish their

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