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1、15Aluminium15<1IntroductionThisisprobablythemostabundantmetalontheearth,astheoxide,aluminaAI2O3,makesupthechiefpartallclaysandmanyotherrocks・ThemetalwasfirstisolatedasapowderbyWohler.Itwasnotuntilabout1854thatitwasobtainedonamanufacturingscale.Aluminumi
2、saverylightmetal.Weighingonlyabout2.7timesthatofwater;Anditisthereforeonlyaboutone-thirdtheweightofiron.Itisgoodconductorofelectricity,andalthoughinferiortocopperforthelongdistancetransmissionofelectricpowerowingtoitslightnessandlowercost.ltformsavaluab
3、lealloywithcopper,knownasaluminumbronze.Toobtainthebronzeamixtureofcorundum(alumina),charcoalandgranulatedcopperisheatedinanelectricfurnace・Thecarbontakesuptheoxygenofthealumina,whilethecopperuniteswiththealuminumtoformagolden-coloredalloywhichhasgreats
4、trengthandelasticity.Thedevelopmentofthemotorandaircraftindustriesledtotheintroductionofanumberofaluminumalloysofgreatvalueowingtotheirlightnessandstrength.Themostimportantoftheseare4magnaliumcontainingmagnesium,and'duraluminwhichisaluminumwithabout4p
5、ercentofcopperandalittermagnesium.Otheralloyswithcopper,nickelandzincareusedintheconstructionofmotor-carandaeroplaneparts.Alloysofaluminumandsilicon,withsmallamountsofothersubstances,areusedinshipbuilding,asafterheattreatmenttheyareverystrongandresistth
6、ecorrosiveactionofseawater;Aluminumhasbeenmadeformanyyearsbytheelectrolysisofalumina(preparedbauxite,A12O3>2H2O)dissolvedinfusedcryolite(sodiumaluminumfluoridethecathode.Thecurrentisbroughtinbythickcarbonrodsformingtheanodewhichwhilecarbonmonoxidegasesc
7、apes.Asthemetalisremovedthesupplyofaluminaiskeptupbyaddingmorebauxitetothemoltenmixture.Intheproductionofaluminum^asinsomanyotherprocesses,thesourceofpoweristheenergyoffallingwater.FactorieshavebeenbuiltnearmanyofthegreatwaterfallsoftheworldsuchasNiagar
8、a.TheFallsoftheRhineatSchaffhausenandinEnglandatKinlochleveninArgyllshire,andinNorthWales.ThebauxiteusedischieflyfromthesouthofFrance,butusefuldepositsoccurringinthesouthernpartoftheUnitedStates,andAntrim,NorthernIreland・Theremar
