Part 27

_Uses._ The valuable properties of aluminum adapt it to numerous applications in the arts and everyday life. Hitherto these have been very limited, owing to its comparatively high price; which, notwithstanding it has fallen considerably, is still sufficient to prevent its general or even extensive application. The 'eagles' of the French army have been made of it, as well as certain articles of jewelry, plate, &c., as brooches, bracelets, chains, spoons, and other ornamental and useful objects. Owing to its low sp. gr., it has been used as a suitable material for the minute decimal weights of chemists, for military helmets, trumpets, &c. A few cornet-à-pistons, for which its lightness and sonorousness admirably adapt it, have actually been made of it. Its power of resisting oxygen, sulphuretted hydrogen, moisture, &c., would render it invaluable as a coating to metals, particularly iron and lead, to protect them from rust or corrosion, did not its price intervene. As an internal coating for water-pipes, cisterns, &c., no other substance, except gold and platinum, is so well adapted. In _chemistry_, capsules, tubes, &c., either made of or coated with it, may be often advantageously substituted for those of platinum.

In addition to what has been said above, it may be observed that, in preparing aluminum, the chief care should be to avoid accidents or failure by the employment of too high a temperature, and to avoid the product being contaminated with other metals or with carbon. To ensure the purity of the metal is a matter of the greatest difficulty, owing to the facility with which foreign matters are taken up, during the process, from the materials of which the apparatus is composed; and from the substances from which it is prepared being seldom absolutely pure. Indeed, it is not too much to assert that chemically pure aluminum has not yet been obtained; and that even a very close approximation to it is of very rare occurrence. Whenever a copper boat is used to hold the sodium, the product is always contaminated with copper. Chloride of aluminum always contains some of the chlorides of iron and silicon, both of which are volatile, and probably takes up a further portion from the porcelain or earthenware used to form the apparatus. Sodium also is seldom uncontaminated with carbon or some compound of it; in which case, and likewise when it is not carefully freed from the naphtha in which it has been preserved, the product always contains carbon. The crucible, whether of porcelain or iron, in which the final fusion is made, also contributes to contaminate the metal. Hence the inferior whiteness and brilliancy of commercial specimens of aluminum; a metal which, in its absolutely pure state, may be reasonably inferred to be as superior in the above respects to silver as silver is to tin. Commercial aluminum contains from 88 to 94 per cent. only of pure aluminum, and from 1 to 4 per cent. of iron, 1/2 to 3 per cent. of silicon, and from 1 to 6 per cent. of copper.

Aluminum salts are generally colourless, soluble, and crystallise with difficulty, and are distinguished as follows:--

_Tests._--1. Ammonia and the alkaline carbonates throw down a bulky white precipitate (hydrate of aluminum) from solutions of its salts, which is insoluble in excess of the precipitant.--2. Pure potassa and soda throw down white gelatinous precipitates, freely soluble in excess of the precipitant; from which the hydrate of aluminum is reprecipitated by chloride of ammonium, even in the cold:--3. Phosphate of ammonium gives a white precipitate--4. Iodide of potassium produces a white precipitate, passing into a permanent yellow:--5. Sulphuretted hydrogen gives no precipitate:--6. Sulphydrate of ammonium precipitates alumina from these solutions:--7. Bisulphate of potassium, added to concentrated solutions, gives a precipitate of octahedral crystals of alum:--8. At a red heat its salts part with some of their acid; at a white heat, most of it, if not all:--9. Aluminum compounds, ignited on charcoal before the blowpipe, and afterwards moistened with a solution of nitrate of cobalt and again strongly ignited, give an unfused mass, which, on cooling, appears blue by day, and violet by candlelight; a test, however, which is inapplicable to fusible compounds of aluminum, and such as are not free, or nearly free, from other oxides.

=Aluminum, Acetate of.= _Syn._ ACETATE OF ALUMINA. _Prep._ Pure hydrate of aluminum is digested, to saturation, in strong acetic acid, in the cold; and the resulting solution, after being filtered or decanted, is either evaporated by a very gentle heat to a gelatinous, semi-solid consistence (its usual form), or is preserved in the liquid state. By spontaneous evaporation it may be obtained in long, transparent crystals.

_Red liquor._ From alum, in powder, 4 parts; warm water, q. s. to dissolve; acetate of lead, in powder, 3 parts; the solution and mixture being effected by lengthened agitation in a tub or other wooden vessels, and the clear liquid, after repose for a sufficient time, decanted or drawn off from the sediment.

From alum, 2 parts; (dissolved in) warm water, q. s.; solution of pyrolignite of lime (20° Baumé), 3 parts; as before, but allowing a longer time for the subsidence of the precipitate, and taking more care in the decantation than when acetate of lead is employed.

By decomposing a solution of crude sulphate of alumina with neutral or monobasic acetate of lead.

_Prop._ Its characteristic property is the feeble affinity existing between its acid and base, which, when it is used as a mordant, is counterbalanced by that of the fibres of the cloth or yarn to which it is applied. In other respects it resembles the other simple salts of alumina.

_Uses, &c._ In _dyeing_ and _calico printing_, as a mordant. In _medicine_, properly diluted, in chronic diarrh[oe]a; and, mixed with syrup of poppies, in slight cases of hæmoptysis (spitting of blood). It has been employed by M. Gannal as an injection to preserve animal bodies, which it will do for years.--_Dose_, 1/2 to 1 dr. daily, in divided portions, taken in thin mucilage or syrup, or in barley-water; as an injection, 10 to 20 gr., to water, 4 to 6 fl. oz., in gonorrh[oe]a, leucorrh[oe]a, &c.

=Aluminum, Chloride of.= Al_{2}Cl_{6}. _Syn._ SESQUICHLO''RIDE OF ALUMINUM; ALUMIN'II CHLORI'DI, &c., L. _Prep._ A thick paste made of dry precipitated alumina, lampblack, and oil, is strongly heated in a covered crucible until all the organic matter is carbonised. The residuum is transferred to a porcelain tube fixed across a furnace, one end of which is connected with another tube containing dry chloride of calcium, and the other end with a small tubulated receiver. The porcelain tube is then heated to redness, whilst chlorine, dried by passing through the chloride-of-calcium tube, is transmitted through the apparatus. In one or two hours, or as soon as the tube is choked, the whole is allowed to cool, and the newly-formed SESQUICHLORIDE collected and preserved in mineral naphtha for use.

On the large scale:--Chlorine, dried as before, is passed over a mixture of pure clay, lamp-black, and coal-tar, contained in an iron retort, similar to that used in the manufacture of coal-gas (previously ignited by means of a suitable furnace), and connected with a cool chamber accurately lined with tiles of earthenware. The vapours of the SESQUICHLORIDE condense in this chamber, as a yellowish crystalline mass, which is collected and preserved as before.

_Prop., &c._ It is volatile at a dull red heat; excessively greedy of moisture; and very soluble, with decomposition, hydrochloric acid and alumina being formed. Once dissolved, it cannot be again recovered. Its chief use is in the preparation of aluminum.

_Obs._ Although alumina, like magnesia, is freely soluble in hydrochloric acid, the sesquichloride of aluminum contained in this solution cannot be obtained in the anhydrous state, or even the solid form, by its evaporation; the chloride suffering decomposition, with the formation of hydrochloric acid, which is volatilised, and alumina, which is left behind.

=Aluminum, Ni'trate of.= Al_{2}(NO_{3})_{6}. _Syn._ NITRATE OF ALUMINA; ALU'MINÆ NI'TRAS, L. _Prep._ Similar to that of the acetate and citrate. Its concentrated acid solution deposits rhombic crystals, containing 18 equiv. of water.

=Aluminum, Oxide of= (Al_{2}O_{3}), and =Hydrate of= (Al_{2}(HO)_{6}). _Syn._ ALUMINA.

_Prep._ Aluminum is precipitated as a hydrate from solutions of aluminum salts on the addition of an alkali or alkaline carbonate; and this precipitate, after being thoroughly washed and dried, on ignition loses its water and becomes anhydrous. The following are the best formulæ for the purpose:--

Alum is dissolved in about 20 times its weight of distilled water, and the solution is dropped slowly into pure solution of ammonia, until the latter is nearly but not entirely saturated, when the whole is set aside for some time. The clear supernatant liquid is then decanted, and the precipitate is carefully and thoroughly washed three or four times with tepid distilled water; after which it is collected on a filter, again well washed with water, and, lastly, pressed and dried between bibulous paper, either without heat, or at a temperature not higher than 120° Fahr. The product is pure hydrate of ammonium, and is converted into anhydrous alumina by exposure to a white heat in a covered crucible. The residuum, after ignition, is pure ANHY'DROUS ALUMINA, or SESQUIOX'IDE OF ALUMIN'UM.

A solution of alum is slowly added to a solution of carbonate of ammonia, avoiding excess; and the resulting precipitate, after being washed and pressed, is dried at a heat of from 120° to 180° Fahr.

_Prop., &c._ A soft white powder. The hydrate is freely soluble in the acids and in solution of caustic potassa and soda (from which it is precipitable by sal ammoniac); when anhydrous (as after ignition), it is scarcely acted on by acids, and when perfectly indurated, or crystallised, it is wholly insoluble; but on ignition with alkalies, alkaline ALU'MINATES are formed, and the alumina is then readily dissolved by acids, forming salts, which are mostly colourless, non-volatile, and soluble; they have a very astringent and somewhat sweetish taste, redden litmus paper, and lose their acids by ignition. Its most remarkable, or rather useful property, is its strong affinity for the fibres of organic bodies, as cotton, flax, silk, wool, &c., which are capable of taking it from its salts; and also for organic colouring matters. Hence its great use in dyeing, and in bleaching liquids and the preparation of lakes. Hydrate of aluminum agitated or digested with liquids containing vegetable colouring matter, combines with the latter, and either entirely, or to a great extent, removes it from the solution.

Moist precipitated alumina, dried at a heat between 70° and 80°, contains above 58% of water; dried at 212° Fahr., about 32% of water.

_Estim._ Aluminum is weighed as oxide, after ignition. The solubility of the moist or recently precipitated hydrate in solution of ammonia enable us to separate it from the ALKALINE EARTHS which, when present, are thrown down with it.

_Uses, &c._ The moist hydrate is used in several processes in the arts. It is the base of cobalt-blue, the lake-pigments, &c. In _medicine_, it is employed as an antacid and astringent, in acidity of the stomach, cholera, diarrh[oe]a, and dysentery; in which it is said to be superior to the other absorbent remedies. (Ficinus.) It has also been highly recommended in the vomiting and diarrh[oe]a of infancy. (Durr; Neumann; Weese; &c.)--_Dose._ Children 3 to 10 gr.; adults, 5 or 6 to 20 or even 30 gr., three to six times daily, suspended in water, by mucilage or simple syrup.

=Aluminum, Sil'icate of.= Al_{2}(SiO_{2})_{3}. _Syn._ SIL'ICATE OF ALUMINA. A substance which, in its hydrous form, is the chief and characteristic ingredient of common clay; and which also occurs, in combination, in several other important and abundant minerals.

=Aluminum, Sul'phate of.= Al_{2}(SO_{4})_{3}. _Syn._ SESQUISUL'PHATE OF ALUMINA, NEUTRAL S. OF A., ALU'MINÆ SUL'PHAS, A. SESQUISUL'PHAS, L. _Prep._ 1. Saturate dilute sulphuric acid with hydrate of aluminum, gently evaporate, and crystallise.

2. (Crude, commercial.) By mixing clay and oil of vitriol, in the way described under ALUM. The product is the 'CONCENTRATED ALUM' of the dyers.

_Prop._ Its crystals are needles and thin pearly plates; soluble in 2 parts of water; taste astringent, and somewhat sweetish; reaction acid; a full red heat expels its acid, leaving a residuum of pure alumina; with the sulphates of potassium, sodium, and ammonium, it forms alum.

_Uses, &c._ In the _arts_, chiefly as a substitute for alum; the sulphate of potassium in the latter, being found to be an unnecessary and costly ingredient, only useful to purify the salt from iron, by forming a compound of easy crystallisation; an object that may be effected with greater certainty by cheaper methods. In _medicine_, as a wash for foul and ill-conditioned ulcers; and as an astringent and antiseptic injection. M. Gannal has successfully employed a solution of this salt to preserve animal bodies, by throwing it into the arteries. Even an enema of 1 quart of it, or an injection of a like quantity into the [oe]sophagus, will suffice to preserve a body for several weeks. The mineral called AL'UNITE or ALU'MINITE, found near Newhaven (Sussex), is a native subsulphate or basic sulphate (DISUL'PHATE) of alumina.

=Aluminum, Sulphide of.= Al_{2}S_{3}. _Syn._ SUL'PHIDE OF ALUMINIUM, &c. A substance best obtained by passing the vapour of bisulphide of carbon over pure alumina, at a bright red heat. It is instantly decomposed by water, with the evolution of sulphuretted hydrogen. See ALUMINUM (_above_).

=Aluminum Tann'ate.= _Syn._ TANNATE OF ALUMINA, Eng.; ALU'MINÆ TANN'AS, L. _Prep._ Take of pure hydrate of aluminum (dried at 90° Fahr.), 1 part; tannic acid (dried at 212°), 2 parts; triturate them together for some time, adding just sufficient water to bring them to the consistence of a syrup, and carefully evaporate to dryness at a heat not higher than 120° Fahr.; lastly, reduce the residuum to powder.

_Uses, &c._ A combination of certain constitution, which is said to have been found very useful in obstinate vomiting and diarrh[oe]a, in dysentery, and particularly in hæmoptysis, hæmorrhage, &c.--_Dose_, 3 to 12 or 15 gr.

=Aluminium Bronze.= See BRONZE ALUMINIUM.

=AL'VINE= (-v[)i]n). _Syn._ ALVI'NUS, L.: ALVIN, Fr. Of or from the belly or intestines; relating to the intestinal secretions.

=AMABELE.= Consists of crushed millets. See MILLET.

=AM'ADOU= (-[)a]h-d[=o][=o]). _Syn._ GERMAN TINDER, TOUCH'WOOD, PYROTECH'NIC SPONGE, SPUNK[double-dagger]§, SURGEON'S AG'ARIC, A. OF THE OAK, &c.; AGAR'ICUS QUER'CÛS, A. QUER'NUS, A. CHIRURGO''RUM, FUN'GUS QUER'CÛS, &c., L.; AMADOU, AGARIC AMADOUVIER, Fr.; ZUNDERSCHWAMM. Ger. A soft, spongy, combustible substance, being the prepared flesh of _bole'tus fomenta''rius_ (Linn.), an indigenous species of fungus found on the oak, birch, and a few other trees (REAL AMADOU or OAK-AGARIC); for which _b. ignia''rius_ (Linn.), a like fungus, found on the willow, cherry, plum, and other trees, is frequently substituted.

_Collec., Prep., &c._ The outer bark of the fungus (collected in Aug. or Sept.) having been removed with a knife, the inner spongy substance is carefully separated from the woody portion lying below, and after being cut into slices, is well beaten with a mallet until sufficiently soft and pliable. Sometimes it is first boiled in water, in order to separate the epidermis and porous parts, and to free it from soluble matter; after which it is beaten as before. In this state it is used in _surgery_, &c. To complete its manufacture for TINDER, it is soaked once, or oftener, in a strong solution of saltpetre (RED AMADOU; BROWN A.); or in a thin paste made of gunpowder and water, which is thoroughly forced into the pores (BLACK A.); after which it is dried, and well rubbed to free it from loose matter. The first is the more cleanly; the last the more combustible.

_Uses, &c._ A light brown or reddish-brown substance. In _surgery_, _pharmacy_, &c., it is used to stop local bleeding, to spread plasters on, as a compress, and for other like purposes. When covered with resin-plaster it forms an excellent article for the protection of abraded surfaces. A small piece thus prepared, of a circular shape, having a round hole cut in the middle, the size of the apex of the corn, is one of the very best corn-plasters known; as from its great softness it at once protects the part from pressure, and removes the cause. As a material for shoe-socks it is superior to all other substances. The amadou for surgical purposes must not contain nitre.

=AMAL'GAM.= [Eng., Ger.] _Syn._ AMAL'GAMA, L.; AMALGAME, Fr. In _chemistry_ and _metallurgy_, an alloy containing quicksilver; more particularly one in which that metal plays a conspicuous part. Medallists improperly apply this term to all soft alloys.

Mercury unites with many of the metals by mere contact; and with some of them, as gold, silver, tin, and lead, in certain proportions, without losing its fluidity. In a few cases, as with potassium, this union is attended with considerable violence, and with the production of light and heat.

_Prep._ Most of these compounds may be formed by agitating or rubbing the mercury with the other metal, or metals, in the state of filings or small fragments, either with or without heat; or with the easily fusible metals, by adding it to them in the melted state; care been taken, in both cases, that the heat be not sufficient to volatilise the mercury.

_Prop., Uses, &c._ Some amalgams are solid, and not unfrequently crystalline; others are fluid. Of the latter several crystallise after a time, becoming solid; being, probably, merely solutions of the solid amalgams in excess of mercury. The amalgams of gold, silver, tin, zinc, &c., are extensively employed in gilding, silvering and dentistry, and in other useful arts and manufactures.

=Amalgam, Ammonium.= An unstable compound produced when a globule of mercury is placed in a small cavity formed in a piece of sal ammoniac, and the negative pole of a powerful galvanic battery is brought into contact with the metal, and the positive pole, with the ammoniacal salt. In a few seconds the new compound (ammonium amalgam) of the consistence of butter is formed. On withdrawing the influence of the battery, the whole returns to its former condition. By putting an amalgam of sodium into the moistened cavity of the sal ammoniac, similar results are obtained. The phenomena attending the formation of this new substance have been urged as evidence of the existence of the theoretical basic radicle AMMONIUM.

=Amalgam, Elec'trical.= _Prep._ 1. Take zinc and grain-tin, of each, 1 _oz._; melt them in an iron ladle, remove it from the fire, and add of mercury (hot), 3 _oz._; stir the whole well together with an iron rod, pour it into a well-chalked wooden box, and agitate it violently until cold; or, instead of this, it may be briskly stirred until cold, and then powdered. It should be preserved in a corked glass bottle.

2. (La Baumé.) Zinc, 2 _oz._; grain-tin, 1 _oz._; bees' wax, 1/2 _oz._; melt, add of mercury, 6 _oz._, and otherwise proceed as before. Preferred by some to all other mixtures.

3. Zinc, 2 _oz._; mercury, 5 _oz._

_Use._ To cover the cushions of electrical machines. A little of the powder is poured on a piece of paper, crushed smooth with a flat knife, and then spread thinly on the surface of the cushion or rubber, previously slightly smeared with tallow; or the powder may be rubbed down with a little tallow, prior to the application of it.

=Amalgam, Gild'ing.= _Syn._ AMALGAM OF GOLD.

_Prep._ Take of grain-gold, 1 part; mercury, 8 parts; put them into a small iron saucepan, or ladle, and apply a gentle heat, using a smooth piece of iron as a stirrer; when the solution or combination is complete, pour it out on a clean plate or smooth stone slab.

_Use._ To gild brass, copper, &c., in the common process of wash or fire-gilding. A less proportion of gold than the above is used when a thin and cheap gilding is required; as by increasing the quantity of the mercury the same weight of the precious metal may be extended over a much larger surface.

=Amalgam, Sil'vering.=--_a._ For METALS. _Syn._ AMALGAM OF SILVER. _Prep._, _Uses_, &c. As the last, but substituting silver for gold.

_b._ For GLASS. _Prep._ 1. Lead, tin, and bismuth, of each, 1 _oz._; bees' wax or resin 1/4 _oz._; melt, skim off the dross, cool to the lowest point at which the mixture will remain liquid, and add of quicksilver 10 _oz._; mix well with an iron rod.

2. Lead and tin, of each, 1 _oz._; bismuth, 2 _oz._; quicksilver, 4 _oz._; as the last.

_Uses, &c._ For silvering the insides of hollow glass vessels, globes, convex mirrors, &c. The glass being thoroughly cleaned and dried, is carefully warmed, and the amalgam, rendered fluid by a gentle heat, is poured in, and the vessel turned round and round, so as to bring the metal into contact with every part which it is desired to cover. At a certain temperature it will be found to readily adhere to the glass. The excess is then poured out, and the vessel set aside to cool.

=Amalgams, Tooth.= See DENTISTRY and TOOTH-CEMENTS.

=Amalgam, Var'nisher's.= _Prep._ Melt grain-tin, 4 _oz._, with bismuth, 1 _oz._; add quicksilver, 1 _oz._, and stir till cold; then grind it very fine with white-of-egg or with varnish, and apply the mixture to the figure or surface with a soft brush. It is used in several of the ornamental trades.

=Amalgamating Salts.= Boil a solution of pernitrate of mercury with excess of equal parts of powdered persulphate and perchloride of mercury, and decant the liquid portion of the result for use. Chiefly used for amalgamating the zinc plates of galvanic batteries, also as a substitute for mercury in gilding by the amalgam process.

=AMAL'GAMATED.= _Syn._ AMALGAMA'TUS, L.; AMALGAMÉ, Fr. Compounded or blended with quicksilver; formed into an amalgam.

=AMALGAMA'TION.= [Eng., Fr.] _Syn._ AMALGAMA'TIO, L.; VERQUICKEN, Ger. The act or process by which an amalgam is formed; hence loosely, the mixing or blending of different things. In the art of the refiner, the operation of separating gold and silver from their ores by means of mercury.

=AM'ANDINE= (-d[=e]ne). _Prep._ 1. (Transparent.)--_a._ Fine new white or pale honey, 4 _oz._; white soft-soap (prepared from lard and potassa), 2 _oz._; mix thoroughly in a marble mortar, adding 1 or 2 teaspoonfuls (if necessary) of solution of potassa, until a perfectly homogeneous paste or cream is produced; then rub in, by degrees, and very gradually, of oil of almonds, 7 _lbs._ (or q. s.), previously mixed with essential oil of almonds, 1 _oz._; essence (oil) of bergamot, 3/4 _oz._; oil of cloves, 1/2 _oz._; and balsam of Peru, 3 _dr._ The product, which should have a rich, transparent, jelly-like appearance and behaviour, is, lastly, put into pots for use or sale.

_b._ (G. W. S. Piesse.) Simple syrup, 4 oz.; white soft-soap (see _above_), 1 oz.; oil of almonds, 7 _lbs._ (previously scented with--); essential oil of almonds and bergamot, of each 1 _oz._; oil of cloves, 1/2 _oz._; the whole being mixed, &c., as before. Both the above are of very fine quality. Glycerin, in the proportion of about 1/2 _oz._ to each _lb._ of the products, added with the soap, improves their softening quality.