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81 North-Western, Manchester, South Junction & Altrincham and Cheshire Lines railways. Pop. of urban district (1901) 16,831. Many residences in the locality are occupied by those whose business lies in Manchester, who are attracted by the healthy climate and the vicinity of Bowdon Downs and Dunham Massey Woods. Market gardening is carried on, large quantities of fruit and flowers being grown for sale in Manchester. Cabinet-making is also practised; and there are sawmills, iron foundries, and manufactures of cotton, yarn and worsted.

Altrincham (Aldringham) was originallyincluded in the barony of Dunham Massey, one of the eight baronies founded by Hugh, earl of Chester, after the Conquest. An undated charter from Hamo de Massey, lord of the barony, in the reign of Edward I., constituted Altrincham a free borough, with a gild merchant, the customs of Macclesfield, the right to elect reeves and bailiffs for the common council and other privileges. In 1290 the same Hamo obtained a grant of a Tuesday market and a three days’ fair at the feast of the Assumption of the Virgin; but in 1319, by a charter from Edward 11., the date of the fair was changed to the feast of St James the Apostle. A mayor of Altrincham is mentioned by name in 14 5 2, but the office probably existed long before this date; it has now for centuries been a purely nominal appointment, the chief duty consisting in the opening of the annual fairs. The trade in worsted and woollen yarns, which formerly furnished employment to a large section of the population, has now completely declined, partly owing to the introduction of Irish worsted.

See Victoria County History, Cheshire; Alfred lngham, History of Altrincham and Bowdon (Altrincham, 1879).

ALTRUISM (Fr. autrui, from Lat. alter, the other of two), a philosophical term used in ethics for that theory of conduct which regards the good of others as the end of moral actibn. It was invented by Auguste Comte and adopted by the English positivists as a convenient antithesis to egoism. According to Comte the onlypractical methodof social regenerationis gradually to inculcate the true social feeling which subordinates itself to the welfare of others. The application to sociological problems of the physical theory of organic evolution further developed the altruistic theory. According to Herbert Spencer, the life of the individual in the perfect society is identical with that of the state:

in other words, the first object of him who Would live well must'

be to take his part in promoting the Well-being of his feIIQWs individually and collectively. Pure egoism and pure altruism are alike impracticable. For on the one hand unless the egoist’s happiness is compatible to some extent with that of his fellows, their opposition will almost inevitably vitiate his perfect en joyment; on the other hand, the altruist whose primary object is the good of others, must derive his own highest happiness—Le. must realize himself most completely—~in the fulfilment of this object. In fact, the altruistic idea, in itself and apart from a further definition of the good, is rather a method than an end.

The self-love theory of Hobbes, with its subtle perversions of the motives of ordinary humanity, led to a reaction which culminated in the utilitarianism of Bentham and the two Mills; but their theory, though superior to the extravagant egoism of Hobbes, had this main defect, according to Herbert Spencer, that it conceived the world as an aggregate of units, and was so far individualistic. Sir Leslie Stephen in his Science of Ethics insisted that the unit is the social organism, and therefore that the aim of moralists is not the “ greatest happiness of the greatest number,” but rather the “ health of the organism.” The socialistic' tendencies of subsequent thinkers have emphasized the ethical importance of altruistic action, but it must be remembered always that it is ultimately only a form of action, that it may be commended in all types of ethical theory, and that it is a practical guide only when it is applied in accordance with a definite theory of “the good.” Finally, he who devotes himself on principle to furthering the good of others as his highest moral obligation is from the highest point of view realizing, not sacrificing, himself.

See works of Comte, Spencer, Stephen, and text-books of ethics (cf. bibliography at end of article E'rmcs).

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ALTWASSER, a town of Germany, in the Prussian province of Silesia, 43 m. by rail S.W. from Breslau, and 3 m. N. from Waldenburg. It has factories for glass, porcelain, machinery, cotton-spinning, iron-foundries and coal-mines. Pop. (1900) 12,144.

ALTYN-TAGH, or ASTYN-TAGH, one of the chief constituent ranges of theKuen-lun (q.v.) in Central Asia, separating Tibet from east Turkestan and the Desert of Gobi.

ALUM, in chemistry, a term given to the crystallized double sulphates of the typical formula M,SO,,-Ml“-(SO,);24H,O, where M is the sign of an alkali metal (potassium, sodium, rubidium, caesium), silver or ammonium, and M111 denotes one of the trivalent metals, aluminium, chromium or ferric iron. These salts are employed in dyeing and various other industrial processes: They are soluble in water, have an astringent, acid, and sweetish taste, react acid to litmus, and crystallize in regular octahedra. When heated they liqucfy; and if the heating be continued, the water of crystallization is driven off, the salt froths and swells, and at last an amorphous powder remains.

Potash alum is the common alum of commerce, although both soda alum and ammonium alum are manufactured. The presence of sulphuric acid in potash alum was knoWn to the alchemists. J. H. Pott and A. S. Marggraf demonstrated that alumina was another constituent. Pott in his Lithogeognasia showed that the precipitate obtained when antalkali is poured into a solution of alum is quite different from lime and chalk, with which it had been confounded by G. E. Stahl. Marggraf showed that alumina is one of the constituents of alum, but that this earth possesses peculiar properties, and is one of the ingredients in common clay (Experiences faites sur la terre del’alun, Marggraf’s Opuscii. 111). He also showed that crystals of alum cannot be obtained by dissolving alumina in sulphuric acid and evaporating the solutions, but when a solution of potash or ammonia is dropped into this liquid, it immediately deposits perfect crystals of alum (Sur la régénératirm de l'alun, Marggraf’s Opus-c. ii. 86).

T. O. Bergman also observed that the addition of potash or ammonia made the solution of alumina in sulphuric acid crystal~ lize, but that the same efiect was not produced by the addition of soda or of lime (De confedione aluminus, Bergman’s Opusc. i. 22 5), and that potassium sulphate is frequently found in alum.

After M. H. Klaproth had discovered the presence of potassium in lcucite and lepidolite, it occurred to L. N. Vauquelin that it was probably an ingredient likewise in many other minerals. Knowing that alum cannot be obtained in crystals without the addition of potash, he began to suspect that this alkali constituted an essential ingredient in the salt, and in 1797 he published a dissertation demonstrating that alum is a double salt, composed of sulphuric acid, alumina and potash (Annales de chimie, xxii. 258). Soon after, I. A. Chaptal published the analysis of four different kinds of alum, namely, Roman alum, Levant alum,. British alum and alum manufactured by himself. This analysis led to the same result as that of Vauquelin (Ann. de chim. xxii. 280).

The word alumen, which we translate alum, occurs in Pliny’s Natural History. In the 15th chapter of his 35th book he gives a detailed description of it. By comparing this with the account of awrrnpla given by Dioscorides in the 123rd chapter of his 5th book, it is obvious that the two are identical. Pliny informs us that alumen was found naturally in the earth. He calls it salsugoterrae. Difierent substances were distinguished by the name of “ alumen ”; but they were all characterized by a certain degree of astringency, and were all employed in dyeing and medicine, the light-coloured alumen being useful in brilliant dyes, the dark-coloured only in dyeing black or very dark colours. One species was a liquid, which was apt to be adulterated; but when pure it had the property of blackening when added to pomegranate juice. This property seems to characterize a solution of iron sulphate in water; a solution of ordinary (potash) alum would possess no such property. Pliny says that there is another kind of alum which the Greeks call schislos. It forms in white threads upon the surface of certain stones. From the name schistos, and the mode of formation, there can be little doubt that this species was the salt which forms spontaneously on certain slaty‘minerals, as alum slate and bituminous shale, and which consists chiefly of the sulphates of iron and aluminium. Possibly in certain places the iron sulphate may have been nearly wanting, and then the salt would be white, and would answer, as Pliny says it did, for dyeing bright colours. Several other species of alumen are described by Pliny, but we are unable to make out to what minerals he alludes.

The alumen of the ancients, then, was not the same with the alum of the moderns. It was most commonly an iron sulphate, sometimes probably an aluminium sulphate, and usually a mixture of the two. But the ancients were unacquainted with our alum. They were acguainted with a crystallized iron sulphate, and distinguished it by the names of misy, sory, chalcantkum (Pliny xxxiv. 12). As alum and green vitriol were applied to a variety of substanCes in common, and as both are distinguished by a sweetish and astringent taste, writers, even after the discovery of alum, do not seem to have discriminated the two salts accurately from each other. In the writings of the alchemists we find the words misy, sory, chalcanlhum applied to alum as well as to iron sulphate; and the name atramentum rulorium, which ought to belong, one would suppose, exclusively

octahedra and is very soluble in water. The solution reddens litmus and is an astringent. When heated to nearly a red heat it gives a porous friable mass which is known as “ burnt alum.” It fuses at 92° C. in its own water of crystallization. “ Neutral alum ” is obtained by the addition of as much sodium carbonate to a solution of alum as will begin to cause the separation of alumina; it is much used in mordanting. Alum finds application as a mordant, in the preparation of lakes for sizing hand-made paper and in the clarifying of turbid liquids.

jSodium alum, Na2504~Al,(804);-24H;O, occurs in nature as the mineral mendozite. It is very soluble in water, and is ' eirtremely difficult to purify. In the preparation of this salt, it is preferable to mix the component solutions in the cold, and to evaporate them at a temperature not exceeding 60° C. 100 parts of water dissolve no parts of sodium alum at 0° C. (W. A. Tilden, Jour. Chem. Soc., 1884, 45, p. 409), and 51 parts at 16° C. (E. Augé, Comples rendus, 1890, no, p. 1130).

7 Chrome alum, KZSOi-CrASO‘h-Zfli-lo, appears chiefly as a by-product in the manufacture of alizarin, and as a product of the reaction in bichromate batteries.

'The solubility of the various alums in water varies greatly, sodium alum being readily soluble in water, whilst caesium and rubidium alums are only sparingly soluble. The various solu

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to green vitriol, applied indiflerently to both. Various minerals are employed in the manufacture

bilities are shown in the following table :—

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of alilm’ the most important being Ammonium Alum. Caesium Alum. Potash Alum. Rubidium Alum.

alumte (q.v.) or alum-stone, alum

schist, bauxite and cryolite, tsc 100 rts water tsc ioo arts water toc 100 parts water toC looparts water In order to obtain-alum from ' issolve. ' issolve. ' dissolve. ' dissolve.

alunite, it is calcined andth'en O 262 o 049 0 $9 0 07,

exposed to the action of air for 10 4-5 10 . 0-29 10 9-52 10 r-09

a considerable time. During this 50 159 5° 1'235 5° 44'" 50 4'98

exposure it is kept continually 128 3(5):; 8° 5'29 123 134:4; 8° "'60

moistened with water, so that it 7 3 357 4

ultimately falls to a very fine Poggiale C. Setterberg

powder. powder is then A71”. Phyi. A11". 1882, 211, p. 104. Poggiale C. Setterberg

lixiviated with hot water, the [3] 8, P- 467

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' liquor decanted, and the alum

allowed to crystallize. The alum schists employed in the manufacture of alum are mixtures of iron pyrites, aluminium silicate and various bituminous substances, and are found in upper Bavaria, Bohemia, Belgium and Scotland. These are either roasted or exposed to the weathering action of the air. In the roasting process, sulphuric acid is formed and acts on the clay to form aluminium sulphate, a similar condition of affairs being produced during weathering. The mass is now systematically extractedwith water, and a solution of aluminium sulphate of specific gravity 116 is prepared. ‘ This solution is allowed to stand for some time (in order that any calcium sulphate and basic ferric sulphate may separate), and is then evaporated until ferrous sulphate crystallizes on cooling; it is then drawn off and evaporated until it attains a specific gravity of 1-40. It is now allowed to stand for some time, decanted from any sediment, and finally mixed with the calculated quantity of potassium sulphate (or if ammonium alum is required, with ammonium sulphate), well agitated, and the alum is thrown down as a finely-divided precipitate of alum meal. If much iron should be present in the shale then it is preferable to use potassium chloride in place of potassium sulphate.

In the preparation of alum from. clays or from bauxite, the material is gently calcined, then mixed with sulphuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulphate and allowed to crystallize: When cryolite is used for the preparation of alum, it is mixed with calcium carbonate and heated. By this means, sodium aluminate is formed; it is then extracted with water and precipitated either by sodium bicarbonate or by passing a current of carbon dioxide through the solution. The precipitate is then dissolved in sulphuric acid, the requisite amount of potassium sulphate added and the solution allowed to crystallize.

ALUMINIUM (symbol Al; atomic weight 27-0), a metallic chemical element. Although never met with in the free state, aluminium is very widely distributed in combination, principally as silicates. The word is derived from the Lat. alumen (see ALUM), and is probably akin to the Gr. ii): (the root of salt, halogen, &c.). In 1722 F. Hofimann announced the base of alum to be an individual substance; L.B. Guyton de Morveau suggested that this base should be called alumine, after Sal alumineux, . the French name for alum; and about 1820 the word was changed into alumina. _ In 1760 the French chemist, T. Baron de Henouville, unsuccessfully attempted “ to reduce the base of alum ” to a metal, and shortly afterwards various other investigators essayed the problem in vain. In 1808 Sir Humphry Davy, fresh from the electrolytic isolation of potassium and sodium, attempted to decompose alumina by heating it with potash in a platinum crucible and submitting the mixture to a current of electricity; in 1800, with a more powerful battery, he raised iron wire to a red heat in contact with alumina, and obtained distinct evidence of the production of an iron-aluminium alloy. Naming the new metal in anticipation of its actual birth, he called it alumium; but for the. sake of analogy he was soon persuaded to change the word to aluminum, in which form, alternately with aluminium, it occurs in chemical literature for some thirty years.

In the year 1824,endeavouring to prepare it by chemical means, H. C. Oersted heated its chloride with potassium amalgam, and failed in his object simply by reason of the mercury, so that when F. Wohler repeated the experiment at Gottingen in 1827, employing potassium alone as the reducing agent, he obtained it in the metallic state for the first time. Contaminated as it was with potassium and with platinum from the crucible, the metal formed a grey powder and was far from pure; but in 1845 he improved his process and succeeded

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in producing metallic globules wherewith he examined its chief properties, and prepared several compounds hitherto unknown. Early in 1854, H. St Claire Deville, accidentally and in ignorance of Wohler’s later results, imitated the 1845 experiment. At once observing the reduction of the chloride, he realized the importance of his discovery and immediately began to study the commercial production of the metal. His attention was at first divided betWeen two processes—the chemical method of reducing the chloride with potassium, and an electrolytic method of decomposing it with a carbon anode and a platinum cathode, which was simultaneously imagined by himself and R. Bunsen. Both schemes appeared practically impossible; potassium cost about £17 per lb, gave a very small yield and was dangerous to mani— pulate, while on the other hand, the only source of electric current then available was the primary battery, and zinc as a store of industrial energy was utterly out of the question. Deville accordingly returned to pure chemistry and invented a practicable method of preparing sodium which, having a lower atomic weight than potassium, reduced a larger proportion. He next devised a plan for manufacturing pure alumina from the natural ores, and finally elaborated a process and plant which held the field for almost thirty years. Only the discovery of dynamo-electric machines and their application to metallurgical processes rendered it possible for E. H. and A. H. Cowles to remove the industry from the hands of chemists, till the time when P. T. L. Héroult and C. M. Hall, by devising the electrolytic method now in use, inaugurated the present era of industrial electrolysis.

The chief natural compounds of aluminium are four in number: oxide, hydroxide (hydrated oxide), silicate and fluoride. Comm 0, dum, the only important native oxide (A1203), occurs

in large deposits in southern India and the United States. Although it contains a higher percentage of ,metal (52-9 %) than any other natural compound, it is not at present employed as an ore, not only because it is so hard as to be crushed with difliculty, but also because its very hardness makes it valuable as an abrasive. Cryolite (AlF3-5NaF) is a double fluoride of aluminium and sodium, which is scarcely known except on the west coast of Greenland. Formerly it was used for the preparation of the metal, but the inaccessibility of its source, and the fact- that it is not sufficiently pure to be employed without some preliminary treatment, caused it to be abandoned in favour of other salts. When required in the Héroult-Hall process as a solvent, it is sometimes made artificially. Aluminium silicate is the chemical body of which all clays are nominally composed. Kaolin or China clay is essentially a pure disilicate

(Alea-2Si02-2HZO), occurring in large beds almost throughout_

the world, and containing in its anhydrous state 24-4 % of the metal, which, however, in common clays is more or less replaced by calcium, magnesium, and the alkalis, the proportion of silica sometimes reaching 70%. Kaolin thus seems to be the best ore, and it would undoubtedly be used were it not for the fatal objection that no satisfactory process has yet been discovered for preparing pure alumina from any mineral silicate. If, according to the present method of winning the metal, a bath containing silica as well as alumina is submitted to electrolysis, both oxides are dissociated, and as silicon is a very undesirable impurity, an alumina contaminated with silica is not suited for reduction. Bauxite is a hydrated oxide of aluminium of the ideal composition, A1103‘2H20. It is a somewhat widely distributed mineral, being met with in Styria, Austria, Hesse, French Guiana, India and Italy; but the most important beds are in the south of France, the north of Ireland, and in Alabama, Georgia and Arkansas in North America. The chief Irish deposits are in the neighbourhood of Glenravel, Co. Antrim, and have the advantage of being near the coast, so that the alumina can be transported by water-carriage. After being dried at 100° C., Antrim bauxite contains from 33 to 60 % of alumina, from 2 to 30% of ferric oxide, and from 7' to 24% of silica, the balance being titanic acid and water of combination. The American bauxites contain from 38 to 67 % of alumina, from I to 23 % of ferric oxide, and from 1 to 32 % of silica. The French bauxites are of fairly constant composition, containing usually from 58 to 70 of alumina, 3 to 15 % of foreign matter, and 27 % made

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up of silica, iron oxide and water in proportions that vary with the colour and the situation of the beds. . *

Before the application of electricity, only two compounds were found suitable for reduction to the metallic state. Alumina itself is so refractory that it cannot be melted save by the oxyhydrogen blowpipe or the electric arc, and except in the molten state it is not susceptible of decomposition by any chemical reagent. Deville first selected the chloride as his raw material, but observing it to be volatile and extremely deliquescent, he soon substituted in its place a double chloride of aluminium and sodium. Early in 1855 John Percy suggested that cryolite should be more convenient, as it was a natural mineral and might net require purification, and at the end of March in that year, Faraday exhibited before the Royal Institution samples of the metal reduced from its fluoride by Dick and Smith. H. Rose also carried out experiments on the decompositionof cryolite, and expressed an opinion that it was the best of all compounds for reduction; but, finding the yield of metal to be low, receiving a report of the difficulties experienced in mining the ore, and fearing to cripple his new industry by basing it upon the employment of a mineral of such uncertain supply, Deville decided to keep to his chlorides. With the advent of the dynamo, the position of affairs was wholly changed. The first successful idea of using electricity depended on the enormous heating powers of the arc. The infusibility of alumina was no longer prohibitive, for the molten oxide is easily reduced by carbon. Nevertheless, it was found impracticable to smelt alumina electrically except in presence of copper, so that the Cowles furnace yielded, not the pure metal, but an alloy. 50 long as the metal was principally regarded as a necessary ingredient of aluminium-bronze, the Cowles process was popular, but when the advantages of aluminium itself became more apparent, there arose a fresh demand for some chief method of obtaining it unalloyed. It was soon discovered that the faculty of inducing dissociation possessed by the current might now be utilized .with some hope of pecuniary success, but as electrolytic currents are of lower voltage than those required in electric furnaces, molten alumina again became impossible. Many metals, of which copper, silver and nickel are types, can be readily won or purified by the electrolysis of aqueous solutions, and theoretically it may be feasible to treat aluminium in an identical manner. In practice, however, it cannot be thrown down electrolytically with a dissimilar anode so as to win the metal, and certain difficulties are still met with in the analogous operation of plating by means of a similar anode. Of the simple compounds, only the fluoride is amenable to electrolysis in the fused state, since the chloride begins to volatilize below its melting-point, and the latter is only 5° below its boiling-point. Cryolite is not a safe body to electrolyse, because the minimum voltage needed to break up the aluminium fluoride is 4-0, whereas the sodium fluoride requires only 4- 7 volts; if, therefore, the current rises in tension, the alkali is reduced, and the final product consists of an alloy with sodium. The corresponding double chloride is a far better material; first, because it melts at about 180° C., and does not volatilize below a red heat, and second, because the voltage of aluminium chloride is 2-3 and that of sodium chloride 4-3, so that there is a much wider margin of safety to cover irregularities in the electric pressure. It has been found, however,j that molten cryolite and the analogous double fluoride represented by the formula Ale5-2NaF are very efficient solvents 'of alumina, and that these solutions can be easily electrolysed at about 800° C. by means of a current that completely decomposes the oxide but leaves the haloid salts unaffected. Molten cryolite dissolves roughly 30 % of its weight of pure alumina, so that when ready for treatment the solution contains about the same proportion of what may be termed “ available ” aluminium as does the fused double chloride of aluminium and sodium. The advantages lie with the oxide because of its easier preparation. Alumina dissolves readily enough in aqueous hydrochloric acid to yield a solution of the chloride, but neither this solution, nor that containing sodium chloride, can be evaporated to dryness without decomposition. To obtain the anhydrous single or double chloride, alumina. must be ignited with carbon in a current of chlorine, and to exclude iron from the finished metal, either' the alumina must be pure or the chloride be submitted to purification. This preparation of a chlorine compound suited for electrolysis becomes more costly and more troublesome than that of the oxide, and in addition four times as much raw material must be handled.

At different times propositions have been made to win the metal from its sulphide. This compound possesses a heat of formation so much lower that electrically it needs but a voltage of o-g‘to decompose it, and it is easily soluble in the fused sulphides of the alkali metals. It can also be reducedmetallurgically by the action of molten iron. Various considerations, however, tend to show that there cannot be so much advantage in employing it as would appear at first sight. As it is easier to reduce than any other compound, so it is more difficult to produce. Therefore while less energy is absorbed in its final reduction, more is needed in its initial preparation, and it is questionable whether the economy possible in the second stage would not be neutralized by the greater cost of the first stage in the whole operation of winning the metal from bauxite with the sulphide as the intermediary. ‘ .i .

The Deville process as gradually elaborated between 18 5 5 and 1859 exhibited three distinct phasesz—Production. of metallic Chunk“, sodium, formation of the pure double chloride of sodium "dMam and aluminium,and preparation of the metal by the inter

action of the two former substances. To produce the alkali metal, a calcined mixture of sodium carbonate, coal and chalk was strongly ignited in flat retorts made of boiler~plate; the sodium distilled over into condensers and was preserved under heavy petroleum. ‘In order to prepare pure alumina, bauxite and sodium carbonate were heated in a furnace until the reaction was complete; the product was then extracted with water to. dissolve the sodium aluminate, the solution treated with carbon dioxide, and the precipitate removed and dried. This purified oxide, mixed with sodium chloride and coal tar, was carbonized at a red heat, and ignited in a current of dry chlorine as long as vapours of the double chloride were given 05, these being condensed in suitable chambers. For-the production of the final aluminium, 100 parts of the chloride and 45 parts of cryolite to serve as a flux were powdered together and mixed with 3 5 parts of sodium cut into small pieces. The whole was thrown in several portions on to the hearth of a furnace previously heated to low redness and was stirred at intervals for three hours. At length when the furnace was tapped a white slag was drawn off from the top, and the liquid metal beneath was received into a ladle and poured into cast-iron moulds. The process was worked out by Deville in his laboratory at the Ecole N ormale in Paris. Early in :8 5 5 he conducted large-smle experiments at Javel in a factory lent him for the purpose, where he produced sufficient to show at the French Exhibition of 1855. In the spring of 1856 a complete plant was erected at La Glaciére, a suburb of Paris, but becoming a nuisance to the neighbours, it was removed to Nanterre in the following year. Later it was again transferred to Salindres, where the manufacture was continued by Messrs. Péchiney till the advent of the present electrolytic process renderedit no longer profitable.

When Deville quitted the Javel works, two brothers C. and A. Tissier, formerly his assistants, who had devised an improved sodium furnace and had acquired a thorough knowledge of their leader’s experiments, also left, and erected a factory at Amfreville, near Rouen, to work the cryolite process. It consisted simply in reducing cryolite with metallic sodium exactly as in Deville’s chloride method, and it was claimed to possess various mythical advantages over its rival. Two grave. disadvantages were soon obvious—the limited supply of ore, and, what was even more serious, the large proportion of silicon in the reduced metal. The Amfreville works existed some eight or ten years, but achieved no permanent prosperity. In 1858 or 1859 a small factory, the first in England, was built by F. W. Gerhard at Battersea, who also employed cryolite, made his ownsodium, and Was able tosell the product atgs. 9d. per oz. This enterprise

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only lasted about four years. Between 1860 and 1874 Messrs Bell Brothers manufactured the metal at Washington, near Newcastle, under Deville’s supervision, producing nearly 2 cwt. per year. They took part in the International Exhibition of 1862, quoting a price of 40s. per lb troy.

In r88r J. Webster patented an improved process for making alumina, and the following year he organized the Aluminium Crown Metal Co. of Hollywood to exploit it in conjunction with Deville’s method of reduction. Potash-alum and pitch were calcined together, and the mass was treated with hydrochloric acid; charcoal and water to form a paste were next added, and the whole was dried and ignited in a current of air and steam. The residue, consisting of alumina and potassium sulphate, was leached with water to separate the insoluble matter which was dried as usual. All the by-products, potassium sulphate, sulphur and aluminate of iron, were capable of recovery, and were claimed to reduce the cost of the oxide materially. From this alumina the double chloride was prepared in essentially the same manner as practised at Salindres, but sundry economies accrued in the process, owing to the larger scale of working and to the adoption of W. Weldon’s method of regenerating the spent chlorine liquors. In 1886 H. Y. Castner’s sodium patents appeared, and The Aluminium Co. of Oldbury was promoted to combine the advantages of Webster’s alumina and Castner’s sodium. Castner had long been interested in aluminium, and was desirous of lowering its price. Seeing that sodium was the only possible reducing agent, he set himself. to cheapen its cost, and deliberately rejecting sodium carbonate for the more expensive sodium hydroxide (caustic soda), and replacing carbon by a mixture of iron and carbon—the so-called carbide of iron-— he invented the highly scientific method of winning the alkali metal which has remained in existence almost to the present day. In 1872 sodium prepared by Deville’s process cost about 45. per lb, the greater part of the expense being due to the constant failure of the retorts; in 1887 Castncr’s sodium cost less than rs. per lb, for his cast-iron pots survived 125 distillations.

In the same year L. Grabau patented a method of reducing the simple fluoride of aluminium with sodium, and his process was operated at Trotha in Germany. It was distinguished by the unusual purity of the metal obtained, some of his samples containing 99- 5 to 99-8 ~%. In 1888 the Alliance Aluminium Co., organized to work certain patents for winning the metal from cryolite by means of sodium, erected plant in London, Hebburn and Wallsend, and by r889 were selling the metal at us. to 155. per lb. The Aluminium Company’s price in 1888 was 20s. per lb and the output about 2 50 lb per day. In 1889 the price was r65., but by 1891 the electricians commenced to offer metal at 45. per lb, and aluminium reduced with sodium became a thing .of the past.

About 187o~dynamos began to be introduced into metallurgical practice, and frOm that date onwards numerous schemes for utilizing this cheaper source of energy were brought before the public. The first electrical method worthy of notice is that patented by E. H. and A. H. Cowlcs in 1885, which was worked both at Lockport, New York, U.S.A., and at Milton, Stafiordshire. The furnace consisted of a flat, rectangular, firebrick box, packed with a layer of finely-powdered charcoal 2 in. thick. Through stuffing-boxes at the ends passed the tWO electrodes, made after the fashion of arc-light carbons, and capable‘of being approached together according to the requirements of the operation. The central space of the furnace was filled with a mixture of corundum, coarsely-powdered charcoal and copper; and an iron lid lined with firebrick was luted in its place to exclude air. The charge was reduced by means of a 5o-volt current from a 3oo-kilowatt dynamo, which was passed through the furnace for 1% hours till decomposition was complete. About 100 lb of bronze, containing from 15 to 20 lb of aluminium, were obtained from each run, the yield of the alloy being reported at about 1 lb per :8 e.h.p.-hours. The composition of the alloys thus produced could not be pre— determined with exactitude; each batch was therefore analysed, a numberof them were bulked together or mixed with copper in

Electrical redwtlon. the necessary proportion, and melted in crucibles to give merchantable bronzes containing between 1} and to % of aluminium. Although the copper took no part in the reaction,-its employment was found indispensable, as otherwise the aluminium partly volatilizcd, and partly combined with the carbon to form a carbide. It was also necessary to give the fine charcoal a thin coating of calcium oxide by soaking it in lime-water, for the temperature was so high that unless it was thus protected it was gradually converted into graphite, losing its insulating power and diffusing the current through the lining and walls of the furnace. That this process did not depend upon electrolysis, but was simply an instance of electrical smelting or the decomposition of an oxide by means of carbon at the temperature of the electric arc, is shown by the fact that the Cowles furnace would work with an alternating current.

In r883 R. Crittzel patented a useless electrolytic process with fused cryolite or the double chloride as the .raw material, and in 1886 Dr E. Kleiner propounded a cryolite method which was worked for a time by the Aluminium Syndicate at Tyldesley near Manchester, but was abandoned in 1890. In 1887 A. Minet took out patents for electrolysing a mixture of sodium chloride with aluminium fluoride, or with natural or artificial cryolite. The operation was continuous, the metal being regularly run off from the bottom of the bath, while fresh alumina and flouride were added as required. The process exhibited several disadvantages, the electrolyte had to be kept constant in composition lest either fluorine vapours should be evolved or sodium thrown down, and the raw materials had accordingly to be prepared in a pure state. After prolonged experiments in a factory oWned by Messrs Bernard F réres at St Michel in Savoy, Minet’s process was given up, and at the close of the 19th century the Héroult-Hall method was alone being employed in the manufacture of aluminium throughout the world.

The original Deville process for obtaining pure alumina from bauxite was greatly simplified in 1889 by K. T. Bayer, whose improved process is exploited at Larne in Ireland and at Gardanne in France. New works on the same process have recently been erected near Marseilles. Crude bauxite is ground, lightly calcined to destroy organic matter, and agitated under a pressure of 70 or 80 lb per sq. in. with a solution of sodium hydroxide having the specific gravity 1-4 5. After two or three hours the liquid is diluted till its density falls to 1.23, when it is passed through filter-presses to remove the insoluble ferric oxide and silica. The solution of sodium aluminate, containing aluminium oxide and sodium oxide in the molecular proportion of 6 to 1, is next agitated for thirty-six hours with a small quantity of hydrated alumina previously obtained, which causes the liquor to decompose, and some 70 % of the aluminium hydroxide to be thrown down. The filtrate, now containing roughly two mole~ cules of alumina to one of soda, is concentrated to the original gravity of 1-45, and employed instead of fresh caustic for the attack of more bauxite; the precipitate is then collected, washed till free from soda,'dried and ignited at about rooo° C. to convert it into a crystalline oxide which is less hygroscopic than the former amorphous variety.

The process of manufacture which now remains to be described was patented during 1886 and 1887 in the name of C. M. Hall in America, in that of P. T. L. Héroult in England and France. It would be idle to discuss to whom the credit of first imagining the method rightfully belongs, for probably this is only one of the many occasions when new ideas have been born in several brains at the same time. By 1888 Hall was at work on a commercial scale at Pittsburg, reducing German alumina; in 1891 the plant was removed to New Kensington for economy in fuel, and was gradually enlarged to 1500 h.p.; in 1894 a factory driven by water was erected at Niagara Falls, and subsequently works were established at Shawenegan in Canada and at Massena in the United States. In 1890 also the Hall process operated by steam power was installed at Patricroft, Lancashire, where the plant had a capacity of 300 lb per day, but by r894 the turbines of the Swiss and French works mined the enterprise. About 1897 the Bernard factory at St Michel passed into the hands of

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Messrs Péchiney, the machinery soon being increased, and there, under the control of a firm that has been concerned in the industry almost from its inception, aluminium is being manu~ factured by the Hall process on a large scale. In July 1888 the Sociélé M étallurgique Suisse erected plant driven by a 500 h.p. turbine to carry out Héroult’s alloy process, and at the end of that year the Allgemeinc Elektricitdls Gesellschaf! united with the Swiss firm in organizing the Aluminium Industrie Adieu Case]!

1 schafl of Neuhasen, which has factories in Switzerland, Germany

and Austria. The Saciélé Electzométallurgique Francoise, started under the direction of Héroult in 1888 for the production of aluminium in France, began operations on a small scale at Froges in Isére; but soon after large works were erected in Savoy at La Praz, near Modane, and in 1905 another large factory was started in Savoy at St Michel. In 189 5 the British Aluminium Company was founded to mine bauxite and manufacture alumina in Ireland, to prepare the necessary electrodes at Greenock, to reduce the aluminium by the aid of water-power at the Falls of Foyers, and to refine and work up the metal into marketable shapes at the old Milton factory of the Cowles Syndicate, remodelled to suit modern requirements. In 1905 this company began works for the utilization of another water-power at Loch Leven. .

In 1907 a new company, The Aluminium Corporation, was started in England to carry out the production of the metal by the Héroult process, and new factories were constructed near Conway in North Wales and at Wallsend-on-Tyne, quite close to where, twenty years before, the Alliance Aluminium Co. ha their works. '

The Héroult cell consists of a square iron or steel box lined with carbon rammed and baked into a solid mass; at the bottom is a cast-iron plate connected with the negative pole of the dynamo, but the actual working cathode is undoubtedly the layer of already reduced and molten metal that lies in the bath. The anode is formed of a bundle of carbon rods suspended from overhead so as to be capable of vertical adjustment. The cell is filled up with cryolite, and the current is turned on till this is melted; then the pure powdered alumina is fed in continuously as long as the operation proceeds. The current is supplied at a tension of 3 to 5 volts per cell, passing through 10 or 12 in series; and it performs two distinct functions:——(1) it overcomes the chemical aflinity of the aluminium oxide, (2) it overcomes the resistance of the electrolyte, heating the liquid at the same time. As a part of the voltage is consumed in the latter duty, only the residue can be converted into chemical work, and as the theoretical voltage of the aluminium fluoride in the cryolite is 4-0, provided the bath is kept properly supplied with alumina, the fluorides are not attacked. It follows, therefore, except for mechanical losses, that one charge of cryolite lasts indefinitely, that the sodium and other impurities in it are not liable to contaminate the product, and that only the alumina itself need be carefully purified. The operation is essentially a dissociation of alumina into aluminium, which collects at the cathode, and into oxygen, which combines with_the anodes to form carbon monoxide, the latter escaping and being burnt to carbon dioxide outside. Theoretically 36 parts by weight of carbon are oxidized in the production of 54 parts of aluminium; practically the anodes waste at the same rate at which metal is deposited. The current density is about 700 ampéres per sq. ft. of cathode surface, and the number of rods in the anode is such that each delivers 6 or 7 ampéresper sq. in. of cross-sectional area. The working temperature lies between 750° and 850° C., and the actual yield is 1 lb of metal per 1 2 e.h.p. hours. The bath is heated internally with the current rather than by means of external fuel, because this arrangement permits the vessel itself to be kept comparatively cool; if it were fired from without, it would be hotter than the electrolyte, and no material suitable for the construction of the cell is competent to withstand the attack of nascent aluminium at high temperatures. Aluminium is so light that it is a matter requiring some ingenuity to select a convenient solvent through which it shall sink quickly, for if it does not sink, it short-circuits the electrolyte. The molten metal has a specific gravity of 2- 54, that of molten

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