Metallurgy is a part of chemistry which deals with the extraction of metals.

This is a simple pdfh to understand Metallurgy in a more convinient way.

1. General Principles of Metallurgy
•Afewelementslikecarbon,silver,goldandnoblegasesoccurinfreestate,
whileothersarepresentincombinedstateinearth’scrust.
•Mostofthemetalsoccurastheirminerals.
•Forobtainingaparticularmetal,firstwelookforminerals;theyarenaturally
occurringchemicalsubstancesintheearth’scrustobtainedbymining.
•Thebranchofsciencedealswithdifferentmethodsofextractingthemetal
fromitsnaturalsourcesandthenconvertingthemintousefulmaterialsto
themankindisknownasmetallurgy.
•Themineralswhicharesuitableforextractionofmetalbyapplyingsimple
methodsandgiveshighpercentageofmetalarecalledORES.

2. A. Occurrence:
•Metals occur mostly as their oxides, carbonates,sulphides, chlorides.
•The ores of aluminum, iron, copper and zinc have been given in the table
below.

3. B.PrincipleofExtraction:(Extractionofmetals)
•Themineralsavailableinnaturecontainvarioustypesofimpurities.
•Someimpuritiesarecombinedwiththemineralseitherphysicallyorchemically.
•Sodependingonthenatureoftheimpurities,differenttypesoftreatmentof
theoreareadopted.Someofthesetreatmentsaredescribedhere.
a)OreConcentration:
•Removingoftheunwantedmaterials(e.g.,sandclay,stonesetc.,)fromtheore
isknownasconcentration(or)dressing(or)benefaction.
•Theimpuritiesofcertaintypescanbeeliminatedfromtheoreinthemolten
stateonly.
•Mostoftheimpuritiesintheoresdonotmelteasilyatthetemperatureofthe
normalindustrialfurnaces.Therefore“anoutsidesubstance,addedtotheore
toloweritsmeltingpoint,isknowasflux.”
•“Fluxcombinewiththegangue(i.e.,impuritiesoftheore)chemicallyand
formseasilyfusibleproducts,calledslag”.
•“sincethisentireprocessiscostly,thegangueisremovedfirstbyothercheap
physicalmethods.Someofthecommonmethodsoforedressingare
describedhere.

4. CrushingofOre:Generallymetalsoccurintheformoflargerlumpstheselumps
arecrushedintosmallparticlesbyusingjawcrushersandgrinders.
i)Handpicking:
•Whenoreparticlesandgangueparticlesarehavingdifferentphysical
appearancesthenthismethodisused.Selectedpiecesoforesarepickedby
hand.
ii)Hydrolyticwashing:
•Thecrushedoreiswashedinastreamofwater.Thelighterimpunitiesare
sweptawaywhileheavierparticlessettledown.
•Thisisbasedonthedifferencesingravitiesoftheoreandthegangue
particles.Itisalsocalledgravityseparation.
•Ironoresandtinoresareconcentratedbythismethod.

5. iii)MagneticSeparation:
•Theprocessismeantfortheseparationofmagneticorefromimpurities.
•Inthismethodthepowderedoreisplacedoveraleatherbeltwhich
movesovertworollersoneofwhichismagnetic.
•Whenthecrushedoreispassedovermagneticroller,magneticore
particlesareattractedbyitandfallnearertoitwhileimpuritiesfallaway
fromthemagneticroller.
•Chromite[Fe(CrO
2)]fromsiliceousgangue,rutile(TiO
2)fromcholrapatite
andwolframite(FeWO
4)fromcasiteriteareseparatedbythismethod.

6. iv)FrothFloatationmethod:
•Thismethodhasbeeninuseforremovingganguefromsulphideores.
•Inthisprocess,asuspensionofthepowderedoreismadewithwater.To
it,collectorsandfrothstabilizersareadded.
•Collectors(ex:pineoil,fattyacids,xanthatesetc.,)enhancesnon-wet
abilityofthemineralparticles.
•Frothstabilizers(ex:cresols,aniline)stabilizethefroth.
•Themineralparticlesbecomewetbyoils
whilethegangueparticlesbywater.
•Arotatingpaddleagitatesthemixtureand
drawsairinit.Asaresult,frothisformed
whichcarriesthemineralparticles.
•Afterattachmentofalloreparticlestofoam,
thisisshiftedorcollectinginanothertank,
thenoreparticlessettleddownatthebottom
andfoamisevaporated.

7. 5.Liquefaction:
•Thismethodisusefulforsuchoreswhichcontainfusiblemineralparticles
andhighmeltinggangue.
•Thismethodisusedwithstibniteandantimonymineral.
•Itistakeninafireclaypotswithperforatedbottomandheatedtoaround
500-600
0
c.Onlythemineralpartoftheoremeltsandflowsoutleaving
theganguebehind.

8. b. Oxidation:
•The most commonly used oxidizing agent in the metallurgy is O
2.
C. Reduction:

9. e)MetalslikeAl,MgorCaarealsousedforthereduction.WhenAlisusedasareducingagent,
theprocessisreferredasGoldschmidth’sAluminoThermicprocess.
Thesereactionsrequirehigh
temperatureandherethemetalis
obtainedinmoltenstate.

10. d) Electrolytic method-refining:
•Zn,Cu,Ag,Auetc., impure metals are refined by this method.
•In this method, theimpure metal is anodeand the pure metal is cathode. An
acidified solution of the metal salt is electrolyte.
•On passing electricity pure metal is deposited on the cathode. The impurities
settle to the bottom at the anode. This is know as anode mud.

12. B. Extraction of copper from sulphideore:
•Copper pyrites is the main source of copper metal. From it copper metal is
obtained by the following process.
a)Concentration:
•The finely crushed ore is concentrated by Froth-Flotation process.
•The finely crushed ore is suspended in water containing a little amount of
pine oil.
•A blast of air is passed through the suspension. The particles get wetted by
the oil and float as a froth. The gangue sinks to the bottom.
•The froth is separated and about 95 % concentrated ore is obtained.

13. b)Roasting:
•Theconcentratedoreisthenroastedinafurnaceinpresenceofair.
•SulphurisoxidizedtoSO
2andimpuritiesofarsenicandantimonyare
removedasvolatileoxides.

14. C)Smelting:
•Theroastedoreismixedwithcokeandsilica(SiO
2)andisintroducedintoa
blastfurnace.ThehotairblastconvertsFeOintoferroussilicate(FeSiO
3).
•TheproductoftheblastfurnaceconsistsmostlyofCu
2Sandalittleofferrous
sulphide.Thisproductisknownas“Matte”.Itiscollectedfromtheoutletatthe
bottomofthefurnace.

15. d)Bessemerizationprocess:
•Coppermetalisextractedfrommoltenmattethroughbessemerization.
•ThematteisintroducedintoBessemerconverterthroughtuyers.
•Theairisblownthroughthemoltenmatte.
•BlastofairconvertsCu
2SpartlyintoCu
2Owhichreactswithremaining
Cu
2Stogivemoltencopper.
•Thecoppersoobtainediscalled“Blistercopper”(98%pure).

16. e)Refiningofcopper:
•Blistercopperisrefinedbyelectrolysis.
•Blocksofblistercopper(impurecopper)areusedasanodesandthin
sheetsofpurecopperactcathodes.
•Thecathodeplatesarecoatedwithgraphiteinordertoremovedeposited
copper.TheelectrolyteCuSO
4mixedwithalittleamountofH
2SO
4to
increasetheelectricalconductivity.
•Duringelectrolysis,purecopperisdepositedonthecathodeplatesand
impuritieswhicharesolubleandfalltothebottomofthecellasanode
mud.
Uses:Itisusedasthermalconductor,anelectricalconductor,abuilding
materialandaconstituteofvariousmetalalloys.
•This eclectically refined copper is 100 % pure.

17. Zinc
Occurrence:
•ZincisametallicchemicalelementwiththesymbolZnandatomicnumber
30.
•Znisthe24
th
mostabundantelementintheearthscrustandhasfive
stableisotopes.
•Zndeficiencyaffectsabout2billionpeopleinthedevelopingworldandis
associatedwithmanydiseases.
•Zincisnotfoundinthenativestate.Itsimportantmineralsaregiveninthe
tablebelow.

18. Extraction of zinc from sulphideore:
•The metal Zn can be extracted from its minerals in different ways depending
on the ore.
•Zinc pyrites is main source of zinc metal.
•Following steps are involved in extraction of zinc.
a)Concentration:
•The finely crushed ore is concentrated first by gravity separation process.
•The crushed ore is washed with a stream of water on a wilfleystable, The
table.
•Due to the motion the lighter gangue particles are washed by the steam,the
heavier particles settle to the bottom of the table.
•They partly concentrated ore is futherconcentrated by froth floataion
process. The ore particles go with the froth.
Ifironoxideispresentinthegangue,the
concentratedoreissubjectedfurtherto
electromagneticseparationironoxideis
magneticandsoformsaheapnearertothe
magneticpole.

19. b)Roasting:
•Theconcentratedoreisthenroastedinafurnaceinthepresenceofair.Sulphur
isoxidizedtoSO
2andimpuritiesofarsenicandantimonyareremovedas
volatileoxides.Thefollowingreactiontakesplace.
•Ifcalamineisthestartingmaterialforextractiontheoreisdirectlycalcinedto
getzincoxide.

20. c) Reduction:

21. d) Refining of Zinc:
•Electrolysis is performed in lead-lined concrete cells.
•Anodes are made of lead containing 0.5-1.0 % silver and cathodes are made
of aluminiumsheet.
•The electrolyte is Zinc sulphatesolution containing a little H
2SO
4.
•The Zinc deposited is deposited on cathode.
•The purification of the electrolyte ensures that normal product will reach
purity of 99.99 %

22. Occurrence and principles of
extraction of Fe
A) Occurrence:
•Iron is the second most abundant metal after Al and fourth most abundant
elementin the earth’s crust.
•It is mostly occurs in the combined state.

23. B) Principles of extraction of Fe:
The chemistry of iron can be studied under three sections depending upon the
type of iron required. The sections are
a)Manufacture of cast iron (Fe + 4% C)
b)Manufacture of wrought iron ( Fe + 0.2 % C)
c)Manufacture of steel( Fe + 0.5-1.5% C)
a) Manufacture of cast iron:
•Iron is extracted from its from its oxidesin a blast furnace. This is an almost
cylindrical furnace, lined inside with fire bricks.
•It is charged from the top with an iron ore(8 parts), desulphurisedcoke (4
parts) and lime stone (1 part) and is mixed in 8:4:1parts by weight.
•Air is blown from the bottom. The coke burnsproducing heatand CO.
•The temperature range in the furnace is 300
0
-1600
0
c.
•Various reaction take place in the blast furnace at different temperature and
different zones.

25. •The iron obtained is known as Pig iron.
•The solid iron obtained by cooling pig iron is called as cast iron. It contains
nearly 4% C.

26. b) Manufacture of wrought iron:
•Wroughtironisthepurestformofironcontainingabout0.2%C.
•Itispreparedbyheatingcastironinareverboratoryfurnace.
•Thefurnaceisgivenabasicliningofironoxide.
•Theimpuritiesandthecarbonpresentincastironcombinewiththelining.The
impuritiesformaslagandcarbonisoxidizedtoCOandescapes.
•Itburnswithablueflame.Theflamesareknownas“puddlerscnadles”.Hence
theprocessisknownasPuddlingprocess.
Carbonandvariousimpuritiespresent
combinewithliningandformslag.

27. C) Manufacture of steel:
•Steel contains ( Fe + 0.5-1.5% C).
•ItispreparedbyblowingairthroughmoltenpigirontakeninBessemer
converter.
Bessemer converter process:
•The Bessemer converter is a pear shaped furnace.
•It is constructed with steel.
•It is lined with silica orlime depending on the proportions of impurities present
in the iron (P, Si, Mnand C).
•Air is forced through the inlets at the bottom.

28. •Carbonand various other impurities present combine with oxygenand form
slag.

29. Process of molten electrolysis of Al &
Mg

30. Aluminium
a)Occurance:
•Inearthscrust,aluminiumisthemostabundant(8.3%byweight)
metallicelementandthirdmostabundantofallelements(afteroxygen
andsilicon).
•Itisneverfoundintheelementalstate.
•TheimportancemineralsofAlaregivenbelow.

31. b) Extraction:
•For the purpose of extraction of Al, bauxiteis by far the important source.
•From bauxite Al is obtained by electrolysis.
•For this purpose pure bauxite is necessary.
•The following steps are used in extraction of aluminium.
i.Purification of Bauxite
ii.Electrolytic reduction of alumina
iii.Refining of aluminium

32. i.PurificationofBauxite:
•Bauxitecontainingironoxideasimpurityisknownasredbauxite.Itispurified
eitherbyBaeyersprocessorbyHallsprocess.
•whereasbauxitecontainingsilicaasimpurityisknownaswhitebauxiteandis
purifiedbyserpeksprocess.

35. :

36. ii.ElectrolyticreductionofAlumina:
•Inthemetallurgyofaluminium,purifiedAl
2O
3obtainedfrombauxiteismixedwith
Na
3AlF
6
whichlowersthemeltingpointofthemixtureandmakesitconductivity.
•Electrolysisiscarriedoutinandironorsteeltank.Thetankislinedinsidewiththegraphitethat
actsascathode.Anodeconsistsofanumberofcarbonrods.Suspendedfromthetopofthe
electrolyticcell.
•Theanodesareimmersedpartiallyintotheelectrolyte.Theelectrolyteconsistsofafusedmixture
ofalumina,cryolite.Thesurfaceoftheelectrolyteiscoverswithpowderedcoke.Thispreventsthe
oxidationofthemetalformedinelectrolysis.
•Thefollowingreactiontakesplaceintheelectrolyticcell.

37. •Aluminiumionsmovetowardsthecathode(i.e.carbonlining)andtheyare
discharged.Aluminiummetalisformed.Fluorideionsaredischargedtogive
fluorineattheanode.
•Aluminiumproducedatthecathode,sinkstothebottomtothebottomofthe
cell.Itisremovedfromtimetotimethroughtappinghole.Fluorineformedatthe
anodereactswithalumina.Aluminaisaddedatintervals.Inthisprocess,99%
purealuminiumisobtained.

38. iii. Refining of Aluminium:
•Aluminiumobtained by the above process contains impurities like Si, Cu, etc. It
is further purified by Hoope’selectrolytic method.
•The electrolytic cell used for refining of aluminiumconsists of an iron tank lined
inside with carbon. It contains three layersof fused masses. These layers differ
in their specific gravities.
•The upper layer is of pure aluminium.
•A number of graphite rods acts as cathode. They are suspended from the top
into the upper layer.
•The middle layer consists of a fused mixture of fluorides of sodium, barium and
aluminium. This layer acts us an electrolyte.
•The bottom layer contains impure aluminium.

39. •On passing current Aluminiumions from the middle layer, are discharged at
the cathode layer (upper layer), pure Al is deposited in the upper layer.
•At the same time an equivalent amount of aluminiumpasses into the middle
layer from the bottom layer.
•99.89 % Al is the result of this process.

40. Magnesium
a)Occurrence:
•Magnesiumbeingquitereactivedoesnotoccurinthefreestatein
naturebutitwilloccurinthecombinedstate.
•Itispresentinseawaterashalides,inanimalblood,invegetable
kingdomaschlorophyll.

41. Electrolysisoffusedmagnesiumchloride:
•FusedMgCl
2isobtainedfromcarnalite(KCl.MgCl
2.6H
20)
•{MoltenmixtureofMgCl
2andNaCl}–Electrolyte.
NaCldecreasesthemeltingpointofthemixtureandincreasestheelectrical
conductivityofMgCl
2.
•ThemoltenmixtureofMgCl
2andNaCliselectrolyzedinanironcellthroughwhichan
inertgasorcoalgasflowstoavoidanyreactionbetweentheliberatedmetaland
oxygen/nitrogenoftheair.
•Thecellwallactsasthecathode.Whilethecarbonroddippingintothemetalactsas
anode.Magnesiumisobtainedatthecathodeandchlorineisevolvedatanode.The
reactiontakesplaceasfollows.
Theliberatedmetalbeinglighterthan
theelectrolytefloatsoverthesurface.
Chlorineevolvedatanodeasaby-
product.Metalof99.9%.PureMgis
obtainedbythismethod.

42. Electrolysisoffusedmagnesiumoxide:
•MagnesiummetalcanalsobeobtainedfromMagnesite(MgCO
3).
•Magnesiamixedwith(Mg,Ba&Na)flourides-Moltenmixture.(
electrolyte)
•Electrolysedthemoltenmixtureinsteeltanksat900-950
0
C.
•Ironrods–Cathods
Carbonrods–anodese
Electrolyte–Moltenmixture
•Electrolysis-