Cooley's Cyclopaedia of Practical Receipts Volume I Part 34

_d._ From Bauxite. This mineral, occurring in some parts of Southern France, in Calabria, near Belfast, and in other parts of Europe, consists essentially (viz. 60 per cent.) of hydrate of alumina, more or less pure.

In order to prepare alums and sulphate of alumina from it, the mineral is first disintegrated by being ignited with carbonate of soda, or with a mixture of sulphate of soda and charcoal; in each case the lixiviation of the ignited ma.s.s yields aluminate of soda, from which, by the processes already described under "Cryolite," alum, or sulphate of alumina, and soda are prepared.

_e._ From blast-furnace slag. Lurmann recommends the slag to be decomposed by means of hydrochloric (muriatic) acid. From the resulting solution of chloride of aluminum the alumina is precipitated by carbonate of lime, any dissolved silica being precipitated at the same time. The alumina is dissolved in sulphuric acid, leaving the silica.

[Ill.u.s.tration]

_Prop._ Alum crystallises in regular octahedrons, often with truncated edges and angles; (see _engr._); and sometimes in cubes, but only when there is a deficiency of acid in its composition, with the alkali in slight excess of the proper quant.i.ty. (Lowel.)[38] It is slightly efflorescent in dry air: soluble in 18 parts of cold water, and in rather less than its own weight of boiling water; tastes sweet, acidulous, and very astringent; is styptic; and reddens litmus. When heated it melts, loses its water of crystallisation, and becomes white and spongy (DRIED ALUM); a strong heat, short of whiteness, decomposes it, with the evolution of oxygen and a mixture of sulphuric and sulphurous anhydride; calcined with carbonaceous matter it suffers decomposition, and furnishes a pyrophoric residuum (HOMBERG'S PYRO'PHORUS). Ignited with alkaline chlorides, hydrochloric acid is liberated; which also occurs when their concentrated solutions are boiled together. Ammonia precipitates pure hydrate of aluminum from pota.s.sium alum; but only a subsulphate from the simple sulphate of alumina. Sp. gr. 1724; but, when containing ammonia, often so low as 1710.

[Footnote 38: The ordinary alum, of commerce, consisting of large crystalline ma.s.ses, which do not present any regular geometrical form; but by immersion in water for a few days, octahedral and rectangular forms are developed on its surface. (Daniell.)]

_Tests, &c._ It is easily recognised by its crystalline form, its taste, and by its complete solubility in water. Its aqueous solution gives a white gelatinous precipitate soluble in excess; a platinum wire moistened with the solution imparts a violet colour to the blowpipe flame; and chloride of barium gives a white precipitate insoluble in nitric acid.

_Pur._ When pure, its solution is not darkened by tincture of galls, sulphuretted hydrogen or ferrocyanide of pota.s.sium; neither does it give any precipitate with solution of nitrate of silver. Heated with caustic pota.s.sa, or quick-lime, it does not evolve fumes of ammonia.

_Adult., &c._ The princ.i.p.al impurity, and one which renders alum unfit for the use of the dyer, is iron. This may be readily detected by the blue precipitate it gives with ferrocyanide of pota.s.sium, or the black precipitate with sulphide of ammonium, which are very delicate tests.[39]

Lime, another very injurious contamination, may be detected by precipitating the alumina and iron (if any) with ammonia, and then adding oxalate of ammonia to the boiled and filtered liquid. The liquid filtered from the last precipitate (oxalate of lime) may still contain magnesia, which may be detected by the white precipitate caused on the addition of an alkaline phosphate. Common alum frequently contains ammonia, from urine, or the crude sulphate of the gas-works, having been employed in its manufacture. Powdered alum is frequently adulterated with common salt, in which case it gives a white curdy precipitate with nitrate of silver, turning black by exposure to the light.

[Footnote 39: Good English alum contains less than 01% of iron. The best Roman or Italian alums seldom contain more than 005% of iron-alum, notwithstanding their exterior colour.]

_Phys. eff. &c._ In small quant.i.ties alum acts as an astringent; in larger doses as an irritant. It acts chemically on the animal tissues and fluids, is absorbed, and has been discovered in the liver, spleen, and urine (Orfila), the last often becoming acid (Kraus). Externally, it is astringent. The almost general use of alum by the English bakers is one of the most fertile sources of dyspepsia and liver and bowel complaints in adults; and of debility and rickets in children. Bad teeth and their early decay is another consequence of the daily use of alum in our food. The bone matter (phosphate of lime) of bread, instead of being a.s.similated by the system, is either wholly, or in part, converted into a salt of alumina, which is useless and incapable of appropriation. When alum has been taken in poisonous doses an emetic should be given, followed by warm diluents and demulcents, containing a little carbonate of soda; and subsequently by a purgative.

_Uses, &c._ The applications of alum in the arts and manufactures are numerous and important. It is used to harden tallow and fats; to render wood and paper incombustible; to remove greasiness from printers' blocks and rollers; to prepare a paper for whitening silver and silvering bra.s.s in the cold; to help the separation of the b.u.t.ter from milk; to purify turbid water; to dress skins; to fix and brighten the colours in dyeing; to make lake and pyrophorus, &c., &c. It is also extensively used for clarifying liquors, and for many other purposes connected with the arts and everyday life. In _medicine_, alum is used as a tonic and astringent, in doses of 5 to 20 gr.; as a gargle (1 dr. to 1/2 pint of water); and as a collyrium and injection (10 to 15 gr. to 6 oz. of water). In lead colic, 1/2 to 1 dr. of alum (dissolved in gum-water), every 3 or 4 hours, is said to be infallible. Powdered alum is frequently applied with the tips of the fingers, in cases of sore throat and ulcerations of the mouth, &c. A teaspoonful of it is said to be one of the very best emetics in croup. (Dr Meigs.) Alkalies, alkaline carbonates, lime, magnesia, acetate of lead, astringent vegetables, &c., are incompatible with it.

_Gen. commentary._ In addition to the particulars of its manufacture given above, we may add, that the plan of getting rid of the ferric salts there referred to has to some considerable extent been successfully replaced by that of precipitating the alum, instead of the sulphate of iron, by adding alkaline matter to the lixivium. The crystalline precipitate is purified by draining, re-solution, and re-crystallisation; whilst the sulphate of iron and Epsom-salts contained in the mother liquor are obtained by subsequent evaporation and crystallisation; after which a fresh crop of alum may be got from it, by the use of an alkaline precipitant, as before.

In estimating the strength of his solution the alum-maker takes as a standard a measure or sp. gr. bottle capable of holding exactly 80 pennyweights of distilled water. The excess of the weight of liquor, in pennyweights, over 80, or that of water, is called so many 'pennyweights strong.' Thus one of 90 pennyweights (90 dwt.) is said to be '10 dwt.

strong,' or simply, 'one of 90 dwt.' These numbers correspond to 2-1/2 degrees of Twaddle's hydrometer, and may easily be found by dividing Twaddle's degrees by 25 or 2-1/2; or by multiplying them by 4, and pointing off the right-hand figure of the product for a decimal. The result is in alum-makers' pennyweights.

By a patent now expired (Weisman's, 1839) the ferric salts are precipitated by the addition of a solution of ferrocyanide of pota.s.sium (prussiate of potash); after which the supernatant clear liquor, which is now a solution of nearly pure sulphate of alumina, is decanted, and evaporated for future operations, until it either forms, on cooling, a concrete ma.s.s, which is moulded into bricks or lumps, for the convenience of 'packing,' or until it is sufficiently concentrated to be converted into ALUM by the addition of a salt of potash or of ammonia in the usual manner. The product, in each case, is perfectly free from iron. By a like addition of the ferrocyanide to a solution of ordinary sulphate of aluminia or alum, the dyer may himself easily render them free from iron, or iron-alum; when, as mordants for even the most delicate colours, they are equal to the very best Roman alum.

Another process has been patented (Barlow & Gore, 1851) for the manufacture of alum from the ash or residue of the combustion of Boghead-coal, which, though hitherto regarded as almost valueless, actually contains about 30% of alumina. It has not, however, been found a convenient material for the purpose.

By the latest and most approved processes the least possible quant.i.ty of boiling water or liquor is employed for making the solutions, so that they may crystallise without evaporation, and thus economise fuel; and the mother-liquors of previous operations are constantly employed for this purpose, when possible. Nor is anything which is convertible to use, from the drainage of the heaps, to the liquor and slime of the roaching casks, allowed to be wasted.

By whatever process, or from whatever materials alum is obtained, it is absolutely necessary for the successful and economical conduct of its manufacture, that the precise composition of the mineral or minerals employed should be exactly known. This can only be determined by actual a.n.a.lysis, which should be extended to several parts of the same bed, and particularly to the upper and lower strata, which frequently differ in composition from each other, and thus require different treatment, or may be most advantageously employed in combinations with each other. The necessity of this will be seen by reference to the composition of the following minerals, of which the top contains a larger proportion of iron-pyrites than the bottom, and the two require to be mixed, to equally diffuse the sulphuric acid generated by the calcination, &c., to which they are subjected.

The following is the per-centage composition of certain alum shales:--

+------------------+-------------------+ Whitby, Yorks.h.i.+re. (_Richardson._) +--------+----------+ Top Bottom rock. rock. +------------------+--------+----------+ Sulphide of iron 420 850 (_pyrites_) Silica 5225 1516 Protoxide of iron 849 611 Alumina 1875 1830 Lime 125 215 Magnesia 91 90 Oxide of manganese traces traces Sulphuric acid 137 250 (SO_{3}) Pota.s.sa 13 traces Soda 20 traces Chlorine traces traces Coal 497 829 Water 288 00 Loss 460 (?) +------------------+--------+----------+ 100 100 +------------------+--------+----------+

+---------------------+------------------------------+ Campsie, near Glasgow. (_Ronalds._) +---------------------+---------+----------+---------+ Top Top Bottom rock. rock. rock. ---------------------+---------+----------+---------+ Sulphide of iron 4052 3848 963(?) (_pyrites_) Silica 1540 1541 2047(?) Protoxide of iron ... ... 218 Alumina 1135 1164 1891(?) Lime 140 222 40 Magnesia 50 32 217 Oxide of manganese 15 ... 55 Sulphuric acid ... ... 05 Pota.s.sa 90 ... 126 Soda ... ... 21 Carbon or 2765(?) 2880 (?) bituminous matter Coal ... ... 851 Water ... ... 854 Loss 213(?) 313 159(?) +---------------------+---------+----------+---------+ 100 100 100 +---------------------+---------+----------+---------+

Alum-rock, or alum-stone, is a species of impure alunite, and is not of very common occurrence. That of Tolfa, near Civita Vecchia, according to Klaproth, consists of--

Silica 565 Alumina 19 Sulphuric acid (SO_{3}) 165 Pota.s.sa 4 Water 3 Loss 1 ------ 100

which exhibits an excess of about 3% of sulphuric acid, and about 14% of alumina, more than are requisite to form alum with the 4% of pota.s.sa; proportions which, therefore, require to be supplemented with a pota.s.sium salt during the process of manufacture. The alum-stone of Mont d'Or contains, according to Cordier, 14% of oxide of iron.

The presence of lime in alum-ore is most prejudicial, owing to its affinity for sulphuric acid being greater than that of either alumina or iron. Ores containing it in any quant.i.ty are, therefore, unfitted for the manufacture of alum. Magnesia is also prejudicial; but in this case the sulphate of magnesia left in the mother-liquors is not wholly valueless, as it may be crystallised and sold as 'Epsom-salt,'--a thing which is actually done in some English alum-works.

The potash-salt employed by the alum-makers is either the sulphate or the chloride--chiefly the latter; its sources being the waste liquor of soap-works, saltpetre refineries, and gla.s.s-houses. Wood-ashes, although rich in potash, do not answer well unless freed by lixiviation from the large amount of carbonate of lime which is always present in them.

The ammonia-salt used in making alum is generally the crude sulphate prepared from the ammoniacal liquor of gas-works, or that from the manufacture of sal-ammoniac by the destructive distillation of animal matter. Both these liquors may be used without previous conversion into sulphate of ammonia whenever there is an excess of sulphuric acid in the aluminous solution.

Soda-salts are seldom, if ever, used as precipitants in the manufacture of alum, on account of the easy solubility of the resulting SODA-ALUM--a property which unfits them for this purpose. See ALUMS, AMMONIA, DYEING, MORDANTS, POTASH, SULPHURIC ACID, &c. (also _below_).

=Alum, Ammonia.= (NH_{4})_{2}SO_{4} . Al_{2}(SO_{4})_{3} . 24 Aq. _Syn_.

(ALUMEN; ALUM; B. P.), ALU'MEN AMMONIA'TUM, L.; ALUN D'AMMONIAQUE, A.

AMMONIACAL, Fr. This is an alum in which the sulphate of pota.s.sium is replaced by an equivalent of sulphate of ammonium. It is prepared by adding crude sulphate of ammonium to solution of sulphate of aluminum; or gas-liquor, putrid urine, &c., to the acid-sulphate.

Much of the common alum, especially that prepared on the Continent, contains both pota.s.sium and ammonium; and recently enormous works for its manufacture have been established in England. As an astringent, and as a source of alumina in dyeing, it resembles potash-alum (_i. e._ ordinary alum). It may, however, be readily distinguished from the latter by the fumes of ammonia which are evolved when it is moistened and triturated, or heated, with caustic pota.s.sa or quick-lime; and by the residuum of its exposure to a white heat being pure alumina. See ALUM (_ante_).

=Alum, Basic.= A variety of alum found native at Tolfa. On calcination and subsequent lixiviation it yields ordinary alum. A like substance falls as a white powder, when newly precipitated alumina is boiled in a solution of alum.

=Alum, Baume's.= Alum-white. See WHITE PIGMENTS.

=Alum, Dried; Alum, Burnt.= _Syn_. ALU'MEN US'TUM, A. EXSICCA'TUM (B. P.); ALUN SEC, Fr.; GEBRANNTER ALAUN, Ger.; ALUME CALCINATO, Ital. Alum deprived of its water of crystallisation by heat.

_Prep._ Take of alum, 4 oz. Heat the alum in a porcelain dish or other suitable vessel, till it liquefies, then raise and continue the heat, not allowing it to exceed 400, till aqueous vapour ceases to be disengaged, and the salt has lost 47 per cent. of its weight. Reduce the residue to powder, and preserve it in a well-stopped bottle.

_Prop., &c._ Similar to those of common alum, but it is rather more astringent, and is less soluble. When moistened, or placed in contact with water, it resumes its water of crystallisation with evolution of heat.--_Dose_, 10 to 20 gr.; in colic (especially painters' colic), haemoptysis, &c. It is chiefly used as an escharotic, to destroy 'proud flesh,' &c. It must be kept in a stoppered bottle.

=Alum, Chrome.= See ALUMS (in Chemistry).

=Alum, I'ron= (-urn). _Syn_. ALU'MEN FER'RIc.u.m, SUL'PHAS FER'RI ET POTAS'Sae, FER'RI PEROX'IDI POTa.s.sIO-SUL'PHAS, &c., L.

_Comp._ K_{2}SO_{4} . Fe_{2}(SO_{4})_{3}.24Aq.

_Prep._ Take of peroxide of iron, 9 lbs.; sulphuric acid 14 lbs.; dissolve, dilute the mixture with water, q. s., and add of pota.s.sium sulphate, 10 lbs.; evaporate, and crystallise.

_Prop., &c._ Crystals, beautiful octahedrons of a pinkish or pale violet colour. It is strongly recommended, by Dr Tyler Smith, as a chalybeate tonic, and has been used by him, at St. Mary's Hospital with marked success. It has also been used as a mordant, in dyeing black.--_Dose_, 1/2 gr. to 5 gr.

=Alum, Ro'man.= _Syn_. RED ALUM*, ROACH A., ROCHE A., ROCK A.*; ALU'MEN ROMA'NUM, A. RU'BRUM, A. RU'PEUM, &c., L.; ALUN ROMAIN, A. DE ROCHE, Fr.; ALUME DI ROCCA, It. In small fragments, covered with a reddish powder (ALUMEN RUBRUM VE"RUM); originally imported from Civita Vecchia, where it occurs native. It is much esteemed by dyers from being nearly free from iron-alum. That now sold for it in England is ordinary alum coloured with Venetian red, Armenian bole, or rose-pink (ALUMEN RUBRUM SPU"RIUM). This is done by shaking the fragments in a sieve over a vessel of hot water, and then stirring them up with the colour, until the surface is uniformly tinged with it. In genuine roach-alum the colour not only covers the surface, but also partially pervades the substance of the crystals. The name was formerly also applied to a pure white variety of alum, prepared at Tolfa; but it is now, in English commerce, exclusively given to common alum artificially coloured.

=Alum, Saccharated.= Alum, 6 oz., white lead 6 drms., sulphate of zinc 3 drms., sugar 1-1/2 oz. Mix the ingredients reduced to powder into a paste, with vinegar and white of egg. Used in eye waters and cosmetic washes.

=Alum, So'da.= _Syn_. SULPHAS ALUMINae ET SODae, L. _Comp._ Na_{2}SO_{4} .

Al_{2}(SO_{4})_{3} . 24Aq. An alum in which the pota.s.sium sulphate of common alum is replaced by a like salt of sodium. It does not occur in commerce. (Vide _supra_ et _infra_.)

=ALUM-EARTH.= Alumina.

=ALUM MOR'DANTS.= In _dyeing_, mordants having for their basis either common alum or the acetate or sulphate of aluminum. See ALUMS and MORDANTS.

=AL'UM-ROOT.= _Syn._ AMER'ICAN SAN'ICLE; HEU'CHERA (Ph. U. S.), L. The root of _heuchera America'na_ (Linn.), a plant of North America. It is powerfully styptic and astringent; and is used chiefly as an external application in cancer.

=ALUM-WHITE.= See WHITE PIGMENTS.

=AL'UMS.= _Syn._ ALU'MINA (pl. of _alu'men_), L. In _chemistry_, a term applied to a series or group of salts having pota.s.sium alum for their type, which they resemble in crystalline form and const.i.tution.