Chemistry

Metallurgy – SESSION II

What is sterling silver? Session Opener What is sterling silver? Solid solution of Cu in Ag

Session Objectives

Session objectives Methods of purification of metals Metallurgy of Fe, Cu, Ag, Zn, Al

Refining of crude metal 1. Liquation process

Do you know? Infusible impurity left over during liquation is called as: Dross

Refining of crude metal 2. Distillation: Based on difference in the boiling point of the impurities and the metal. Volatile metals form the vapour first and separated by condensing in a receiver.

Refining of crude metal 3. Vacuum sublimation method compressed crude metal Metal under reduced pressure in electric furnace Molten metal (chilled to obtain pure metal) Volatile impurities

Refining of crude metal 4. Furnace refining or poling Oxides are removed from impure metal Melted the metal Reverbaratory furnace

Refining of crude metal (5) Zone refining

Refining of crude metal 6. Van Arkel method (or Vapour phase refining)

Refining of crude metal 7. Thermal decomposition method (Carbonyl method, Mond Process) It is used for refining of Ni and Fe. In this method impure Ni is heated with CO. Nickel carbonyl thus formed is then decomposed to get pure Ni and CO.

Refining of crude metal 8. Cupellation Used for purification of silver containing impurity of lead. Based on selective oxidation of lead over silver. The impure silver is smelted in cupel (dish made of bone ash) in blast of air in reverberatory furnace. Lead is oxidised to lead oxide (PbO) and blown away by blast of air. The remaining part melts and is absorbed by the bone ash cupel. At the end cupel is covered by silver.

Refining of crude metal 9. Electrolytic refining

Electrolytic refining 10. Chromatographic method: Based on the difference in the adsorbability of the metal and the impurities. Adsorbent–alumina (Al2O3). Eleuent Specifically useful for the separation of the elements available in very small amounts. In column chromatography a glass column is packed with an adsorbent like alumina (Al2O3). The mixture of metal and the impurity is poured over this adsorbent followed by an eluent. The component which is weakly adsorbed comes out first followed by the next strongly adsorbed component.

Ellingham diagram

Metallurgy of Iron (i) Ore – Haematite (Fe2O3) (ii) Concentration of ore – by magnetic separation (iii) Roasting – Moisture, sands are removed as oxide. Smelting – Done in blast furnace. Roasted ore, limestone and coke are added in blast furnace for smelting.

Metallurgy of Iron

Heat treatment of steel Quenching or hardening Process of heating steel to red hot followed by sudden cooling by plunging to oil or water. Makes steel hard and brittle due to formation of iron carbide (Fe3C). Annealing Process of heating steel to red hot then cooling slowly. Annealing makes steel soft and ductile.

Heat treatment of steel 3. Tempering Process of heating steel the quenched steel to temperature much below redness followed by slow cooling. Tempering retains the hardness but brittleness disappears. 4. Nitriding Process of producing hard coating or iron nitride on surface of steel.

Metallurgy of copper 1. Ore – Copper pyrite CuFeS2 2. Concentration — Froth floatation process. 3. Roasting —

Metallurgy of copper Smelting Since iron has more affinity for oxygen, therefore FeO is formed first. Slag is removed from upper layer. Molten mass containing Cu2S and Fe is called copper malte.

Metallurgy of copper Basemerisation Molten matter is mixed with sand (SiO2) and heated in Basemer converter. Blister copper. Refining of copper By poling of electrolytic refining.

What is matte? CuO + FeS CuS + FeO Cu2S + FeS None of the above

Metallurgy of Silver 1. Ore — Argentite AgS 2. Concentration — By froth flotation process. 3. Extraction — By Mac Arthur Forrest Process. 4. Refining — By electrolytic method.

Illustrative example Name the metals which are consumed in elemental form? Metals consumed in elemental form are Ag and Au.

Metallurgy of Zinc 1. Ore – Zinc blende (ZnS) 2. Concentration of ore — By froth flotation process. 3. Roasting— 4. Conversion of ZnO to Zn Vapours of Zn of are collected after distillation.

Illustrative example Spelter is 98% Zinc Pure Zinc 98% Al Impure Fe

Metallurgy of Aluminium 1. Ore — Bauxite Al2O3 2. Concentration of bauxite — The method of concentration of bauxite depends on nature of impurity present in it.

Baeyer’s process Used when impurity is of ferrous oxide.

Baeyer’s process

Serpeck’s process — Used when silica is the chief impurity in bauxite.

Serpeck’s process

Hall’s Process Used when no specific type of impurity is present.

Hopp’s process

Electrolysis of pure alumina (Al2O3)

Question

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