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1、UnitOneBeforeReading1.Lookupthefollowingwordsandtermsinyourdictionary:extractivemetallurgy,pyrometallurgyhydrometallurgyelectrometallurgyelectromotiveseries2.MainideaExtractivemetallurgyisconcernedwiththeextractionofmetalsfromoresorconcentrates・Itembracestheoccurrenceofmetals,o
2、reconcentration,extractionandrefiningofmetals,andendswithfinalcastingofthemetalingotandby-products.Intheextractivemetallurgy,themethodoftreatmentmaybebroadlyclassifiedinpyrometallurgy,hydrometallurgyandelectrometallurgy.Themetalsobtainedbythefirsttreatmentoftheoresgenerallycont
3、ainimpurities.Inordertoattainahigherorderofpurity,furtherrefiningisnecessaryonthecrudemetal.TextExtractiveMetallurgy(1)Metalsarederivedfromoreminedfromdepositswhichareconfinedtocertainareasoftheearthcrust.Thegeologist'sdiscoveryoforeandtheraisingoforefromtheminegivethemetallur
4、gicalindustryitsrawmaterial,Thefunctionofextractivemetallurgyistoprocesstheseores,extractthemetalandrefineit.Betweentheminingoftheoreandcastingofthemetalingotfordeliverytothefabricatingindustries,alargenumberofspecializedoperationshavetobeperformed.Thefirststageinmetallurgicalp
5、racticewill,inmostcases,beaprocessoforeconcentrationdesignedtoseparate,bymechanicalmeans,asmuchaspossibleofthenon-metallicganguematerialfromthemineralmattersothataconcentrateofrichmaterialmaybeavailabletothesubsequentprocessesofextraction.(2)Themechanicaloperationsnecessarytose
6、paratethemineralfromthegangueareknownasmineraldressing.Theiruseandthevarietyofmethodadoptedhaveincreasedgreatlyinrecentyearsand,infact,themodernoutputofmetalswouldnotbepossiblewithouttheimprovedtechniquesdevisedtoaidinconcentratingbothhigh-andlow-graderawmaterials.Forexample,th
7、eintroductionoftheflotationprocesspermitsthebeneficiationofcopperorecontainingonly0.5percentcopper,andformerlylookedonaswaste.Mineraldressingitselfisonlyapreliminarystageintheisolationofthemetalfromtheganguematerial,andconstitutesonlyasmallpartofthetotaleffortexpendedintherecov
8、eryofmetal.Itconcentratesthevaluablemineral,andinnoway
