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1、UnitOneBeforeReading1.Lookupthefollowingwordsandtermsinyourdictionary:extractivemetallurgy,pyrometallurgyhydrometallurgyelectrometallurgyelectromotiveseries2.MainideaExtractivemetallurgyisconcernedwiththeextractionofmetalsfromoresorconcentrates・Itembracestheoccur
2、renceofmetals,oreconcentration,extractionandrefiningofmetals,andendswithfinalcastingofthemetalingotandby-products.Intheextractivemetallurgy,themethodoftreatmentmaybebroadlyclassifiedinpyrometallurgy,hydrometallurgyandelectrometallurgy.Themetalsobtainedbythefirstt
3、reatmentoftheoresgenerallycontainimpurities.Inordertoattainahigherorderofpurity,furtherrefiningisnecessaryonthecrudemetal.TextExtractiveMetallurgy(1)Metalsarederivedfromoreminedfromdepositswhichareconfinedtocertainareasoftheearthcrust.Thegeologist'sdiscoveryofor
4、eandtheraisingoforefromtheminegivethemetallurgicalindustryitsrawmaterial,Thefunctionofextractivemetallurgyistoprocesstheseores,extractthemetalandrefineit.Betweentheminingoftheoreandcastingofthemetalingotfordeliverytothefabricatingindustries,alargenumberofspeciali
5、zedoperationshavetobeperformed.Thefirststageinmetallurgicalpracticewill,inmostcases,beaprocessoforeconcentrationdesignedtoseparate,bymechanicalmeans,asmuchaspossibleofthenon-metallicganguematerialfromthemineralmattersothataconcentrateofrichmaterialmaybeavailablet
6、othesubsequentprocessesofextraction.(2)Themechanicaloperationsnecessarytoseparatethemineralfromthegangueareknownasmineraldressing.Theiruseandthevarietyofmethodadoptedhaveincreasedgreatlyinrecentyearsand,infact,themodernoutputofmetalswouldnotbepossiblewithouttheim
7、provedtechniquesdevisedtoaidinconcentratingbothhigh-andlow-graderawmaterials.Forexample,theintroductionoftheflotationprocesspermitsthebeneficiationofcopperorecontainingonly0.5percentcopper,andformerlylookedonaswaste.Mineraldressingitselfisonlyapreliminarystageint
8、heisolationofthemetalfromtheganguematerial,andconstitutesonlyasmallpartofthetotaleffortexpendedintherecoveryofmetal.Itconcentratesthevaluablemineral,andinnoway
