Cooley's Cyclopaedia of Practical Receipts Volume I Part 35

It is found that the aluminum of common alum may be replaced by any other metal having a like nature, without affecting the leading characteristics of the salt; and further, that in the newly formed compound, as in pota.s.sium-alum, the second sulphate may also be replaced under the like conditions. All the alums crystallise in octahedrons or cubes, and they all contain the same number of molecules of water. The alums of commerce (or alums proper) all contain aluminum sulphate and an alkaline sulphate.

_Prep._ All the alums may be made by mixing together solutions of the respective sulphates in equivalent proportions, when crystals may be obtained by evaporation in the usual manner. The presence of sulphuric acid, in slight excess, a.s.sists their crystallisation.

=AL'UMED= (al'umd). Mixed or impregnated with alum. In _dyeing_, mordanted with alum.

=ALU'MEN= (-l'oo-). [L.] Alum; the pharmacopial name of alum. (See _above_.)

=ALUMINIUM.= _Syn._ ALUMINUM (which _see_).

=ALUMINOUS.= In _mineralogy_, of, resembling, or containing aluminum. In _chemistry_, containing or obtained from alum.

=ALUMINUM.= [Eng., Fr., L.] _Syn._ ALUMINIUM, Eng., Fr., L.; ALUMIUM, Ger.

A metallic radical or element very abundantly distributed, united with silica. Discovered by M. Wohler, who succeeded in obtaining it as a grey metallic powder (A.D. 1827); and later (1845), under the form of globules exhibiting the leading characteristics of the metal. In 1854, M. Dumas announced to the 'Academy of Sciences,' that M. St. Clair Deville had procured pure aluminum from clay, and exhibited several specimens of considerable size and beauty. The result was a general impression that it might be easily obtained in any quant.i.ty, and ultimately at a reasonable price; expectations which have been only partly, though to a great extent fulfilled, owing to the expense and trouble of the process, notwithstanding recent improvements.

_Prep._ (M. Deville; A.D. 1854-59.)--A quant.i.ty of chloride of aluminum, varying from 200 to 300 grammes (say from 6 to 10 oz.), is introduced into a wide gla.s.s or porcelain tube, between two plugs of asbestos to retain it in position, and a current of hydrogen (thoroughly dried by pa.s.sing first through concentrated sulphuric acid, and then through a tube containing fused chloride of calcium) pa.s.sed over it; a gentle heat being at the same time applied to the part of the tube containing the chloride, to drive off any free hydrochloric acid which might have been formed by the action of the air upon it. A small porcelain boat, containing sodium, is now introduced at the other extremity of the gla.s.s tube, which is then again closed; and when the sodium is fused, the chloride is sufficiently heated to cause its vapour to come into free contact with it. A powerful reaction ensues, with the evolution of much heat, and this continues as long as any undecomposed sodium remains to act on the pa.s.sing vapour. The ma.s.s in the boat, which is now a mixture of the double chloride of aluminum and sodium, in which small globules of the newly reduced metal are suspended, is allowed to cool in the hydrogen; after which it is treated with water, to remove the soluble double chloride. The residuum, consisting of small globules of aluminum, is, lastly, reduced to a solid b.u.t.ton or ma.s.s, by fusion, at a strong heat, under a layer of the fused double chloride of aluminum and sodium.

On a large scale two cast-iron cylinders are employed, instead of the gla.s.s or porcelain tube just referred to; the anterior one of which contains the chloride of aluminum, and the posterior one a tray holding the sodium, of which 10 or 12 lbs. are commonly operated on at once. These cylinders are united by means of a smaller intermediate one, filled with clean sc.r.a.ps of iron, which serve to separate iron, free hydrochloric acid, and chloride of sulphur, from the vapour of the chloride of aluminum, as it pa.s.ses through them. During the pa.s.sage of the vapour of the chloride this smaller cylinder, or tube, is kept heated to from 400 to 600 Fahr.; but the two other cylinders are only very gently heated, since the chloride is volatilised at a comparatively low temperature, and the reaction between it and the fused sodium, when once commenced, usually generates sufficient heat for the completion of the process.

Occasionally a mixture of the double chloride of aluminum and sodium, 40 parts; chloride of sodium 20 parts; fluor spar, 20 parts; each separately dried, powdered, and then blended together; sodium, in small pieces, 7-1/2 to 8 parts, are used instead of the last.

It is likewise made from a mixture of cryolite and fused chloride of pota.s.sium, of each, in powder, 5 parts; sodium, 2 parts; a cast-iron crucible being employed; the resulting minute globules being collected and fused to a b.u.t.ton under a layer of the double chloride of aluminum and sodium.

_Prop., &c._ Aluminum, when quite pure, closely approaches silver in appearance, except in being rather less white and l.u.s.trous than that metal. Ordinary specimens, called pure, have a slight bluish tint or tin-white colour, with a perfect l.u.s.tre, but far inferior to that of pure silver. Sp. gr. 256, which by hammering may be raised to 267. It is both ductile and malleable; fuses at a temperature between the melting-points of zinc and silver; is not affected by either damp or dry air, or by oxygen at ordinary temperatures, or by water whether cold or boiling; even steam, at a red heat, is only slowly decomposed by it. It is not acted on by nitric acid, however concentrated, unless boiling, and then very slowly; nor by dilute sulphuric acid, sulphuretted hydrogen, and the sulphides, or even the fused hydrates of the alkalies. It is, however, readily dissolved by hydrochloric acid, with the evolution of hydrogen, even in the cold; and by a concentrated mixture of nitric and sulphuric acid. It is feebly magnetic, conducts electricity about eight times better than iron, and is more electro-negative than zinc. Commercial specimens, owing to the presence of iron and silicon, and often zinc, usually slowly tarnish in damp air, and possess the other properties described above in a somewhat diminished degree.

In a finely divided state, particularly in the state of powder or minute scales in which it was originally obtained, when heated to redness, it catches fire and burns with great rapidity in the air, and in oxygen gas with intense brilliancy, the product in each case being alumina.

Aluminum unites with the other metals, forming ALLOYS, of which some promise to be of great value in the arts. An alloy of 100 parts of aluminum with 5 parts of silver may be worked like the pure metal, but is harder and susceptible of a finer polish, whilst its property of not being affected by sulphuretted hydrogen and acids remains unimpaired; even 3% of silver is said to be sufficient to impart to it the full brilliance and colour of pure silver. An alloy containing 10% of gold is softer and scarcely so malleable as the pure metal. With 8% of iron, or 10% of copper, it still remains tough and malleable; but a larger proportion of either of these metals renders it brittle.

The presence of 2 or 3% of zinc destroys its ductility and malleability, and also impairs its colour and l.u.s.tre; whilst less than even 1/4% of bis.m.u.th renders it brittle in a high degree. Small quant.i.ties of aluminum added to other metals change their properties in a very remarkable manner.

Thus, copper alloyed with 10%; of aluminum has the colour and brilliancy of gold, is harder than bronze, very malleable, and may be worked at high temperatures easier than the best varieties of iron; and with 20% is quite white, and closely resembles silver. With more than 12% of aluminum the alloy is harder, but brittle. The alloy formed of 100 parts of silver with 5 parts of aluminum is as hard as the silver of our coinage, whilst the other properties of the latter metal remain unaltered.

_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-a-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 subst.i.tuted 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 a.s.sert 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 pota.s.sa 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 pota.s.sium produces a white precipitate, pa.s.sing into a permanent yellow:--5. Sulphuretted hydrogen gives no precipitate:--6. Sulphydrate of ammonium precipitates alumina from these solutions:--7. Bisulphate of pota.s.sium, 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 ma.s.s, 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 Baume), 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 mon.o.basic 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 diarrha; and, mixed with syrup of poppies, in slight cases of haemoptysis (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 gonorrha, leucorrha, &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 pa.s.sing 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 pa.s.sed 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 ma.s.s, 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'MINae 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 formulae 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 pota.s.sa 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, diarrha, 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 diarrha 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'MINae 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 pota.s.sium, sodium, and ammonium, it forms alum.

_Uses, &c._ In the _arts_, chiefly as a subst.i.tute for alum; the sulphate of pota.s.sium 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 quant.i.ty into the sophagus, will suffice to preserve a body for several weeks. The mineral called AL'UNITE or ALU'MINITE, found near Newhaven (Suss.e.x), 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 pa.s.sing 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'MINae 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.