ALUMINIUM

during the period ro11 to rg25 the annual production of aluminium showed a steady increase of from 45,000 to approximately 200,000 tons from all sources. the increase of 440% in the aluminium production is therefore a remarkable epitome of the wide uses which have been found for the metal. of the foregoing productions the united states and canada contribute about one half, whilst the remainder is made up by the european industry represented by independent inter- ests in great britain, france, switzerland and, latterly, ger- many. virtually all the producing interests are engaged on a policy of expansion. no significant changes have been made in the methods of production, bauxite ore still forms the basic material from which aluminium is reduced and it is commercially mined in the south of france, italy, yugoslavia and hungary, also in british and dutch guiana, while in the united states the ore is mined in arkansas, georgia and alabama. many other prospective deposits exist in other parts of the world, but have not yet been commercially exploited. experiments to reduce aluminium from alunite (aluminium-potassium silicate) and kaolin (aluminium silicate) have been technically but not commercially successful. the average purity of metal now shipped by the leading euro- pean producers is 99%, a somewhat lower commercial grade being employed for castings and higher purity for conversion into sheet, wire and special alloys. the only significant impuri- ties in high-grade aluminium consist of silicon and iron, uses of aluminium.—rthe principal use for aluminium ts in the form of castings, for which purpose the metal is usually alloyed with zinc or copper or both, the aluminium being from 85% to 95% of the content. such alloys form the basis of motor car crank-case castings, transmission housings and a great mul- titude of other parts produced in sand moulds according to reg- ular brass foundry practice. wheels for motor omnibuses, rear axles and brake drums are among the important examples of commercial aluminium castings in regular production. ‘these have been made possible by the development of high endurance alloys resistant to fatigue and shock. in the production of still larger and more difficult castings considerable use has been made of an alloy of 87% aluminium and 13% silicon. by melting this alloy under prescribed conditions it 1s possible to attain a tensile strength of 27,000 lb. per sq. in. and an elongation of 8% on two inches, together with a very dense structure, low shrinkage and absence of porosity. individual castings have been made in this alloy up to a weight of 2,500 pounds. many aluminium castings are now produced in hot tron moulds and afterwards heat treated to bring out the best properties of the metal. an important alloy for this work is generally known as“ y ”’ alloy and was developed at the national physical laboratory, teddington, middlesex. it contains 92 % aluminium, 4 °% copper and the remainder nickel and magnesium, and will give a tensile strength of 44,000 lb. with 53° elongation. unlike many other alloys it is exceedingly strong when hot and is therefore widely used for pistons and cylinders of internal combustion engines (see internal com- bustion engine; metallurgy), . the development of new alloys has also expanded the field for aluminium shect and forgings. although pure aluminium sheet is extensively used for motor car bodies and for cooking utensils, certain uses demand alloys of particularly high strength. this is so in the case of aircraft construction, in which the greater part of the machine is built of duralumin (see aeroplane). this altman—amanulla khan alloy has been progressively developed and used since its invention by wilm in germany in 1910. its average composition is 95 % aluminium, 33% copper and the remainder magnesium and man- ganese. the metal is hot rolled, forged and otherwise fabricated, heat treated and quenched with a resulting tensile strength of 60,000 lb. per sq. in. and an elongation of 20°, on two inches. not only is it comparable with steel on the basis of strength, but ‘t has the merit of light weight attaching to aluminium alloys in general and its tensile strength per ton is practically 2} times greater than 40 tons of stecl. a considerable tonnage of high-grade aluminium is hot rolfed, drawn into wire and stranded into a cable for electrical transmission (see electricity, transmission of). for a given conductivity aluminium is actually some 50°%% lighter than copper and generally more economical. at the present time (1926) it is estimated that there are not less than 200,000 m. of aluminium wire in use for over- head transmission lines, the bulk of which consists of a composite cable having a steel core around which the aluminium wires are stranded. as now commercially produced, the summarised properties of aluminium are as follows (british aluminium company, ltd.}:— atomic weight . = e791 melting point ° c. = 658-7 ae = i217-7 specific heat. ; , = o-214 therma! conductivity (cal. per 1°c. per cm. per sec.) . 0-504 expansion coefficient °c. 0-00002268 oe ae 0-00001 26 density. : 2-705 28,000 lb. per sq. in. 14,000 ib. per sq. in. 9,600,000 ib. per sq. in. tensile strength, wire, hard tensile strength, wire, soft modulus of elasticity —. ; resistivity of aluminium at 20° standard annealed aluminium qi ibid tag ohms per metre gramme = 00-0763 microhms per in, cube = i-1102 microhms per cm. cube . = 2:82 standard hard drawn aluminium ohms per metre gramme = 0:0774 microhms per in. cube = 1-1260 nlicrohms per cm. cube . = 2:86 bibliography.—the literature of aluminium is scattered through the preceedings of such bodies as the institute of metals, american i:lectrochemical society, etc. in addition, the following works are recent and worthy of study. g. mortimer, aluminium (1920); r, j. anderson, the metallurgy of aluminium (1925); f. winteler, die aluminium industrie, ist ed. (1903), 2nd. ed. rev. by a (vp. alvear, marcelo torcuato de (1868- ), argentine politician, was born at buenos aires oct. 4 1868, the son of torcuato de alvear, several times mayor of buenos aires, and grandson of general carlos de alvear, the first argentine minister to the united states. after graduating from the uni- versity of buenos aires he affiliated himself with the radical party, and in 1912, after some years of study and travel in europe, he was elected to the lower house of the argentine congress, first from the city, and then from the province, of buenos aires. as a congressman he promoted social-service legislation, notably for the improvement of housing and civil service conditions. he served as argentine minister to france from 1916 until his election as president of argentina in 1922, when he received a large majority over his opponent, dr. lisandro de la torre. on the whole he continued the policies of his predecessor, hipelito irigoyen, though his long residence in europe enabled him to take a somewhat broader view of foreign affairs. as his term as president continued, he gradually became more influential in the affairs of the radical party, in whose councils he assumed an outstanding position. alverstone, richard everard webster, ist baron (1842-1915), british lawyer (see 1.775), died at cranleigh, surrey, dec. 15 1915. : amanulla khan (1892- ), amir of afghanistan, was born june 1 1892, being the third son of habibulla khan by his principal wife, ulya hazrat. on feb. 20 1919 habibulla khan was assassinated, whereupon his brother, nasrulla khan, seized the reins of government. six days later, however, amanulla khan declared himself amir. in aug. 1919, following fighting between british troops and afghans, the new amir successfully negotiated a treaty of peace by the terms of which afghanistan was left officially free and independent. from this time onward amazon—ambassadors, conference of the amir consistently adopted a policy of westernisation. ie even went so far as to advocate the emancipation of women by female education, which roused the opposition of the mullas and was one of the causes of the rebellion which broke out in khost in 1924. (see afghanistan).