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2. Standard free energy –temperature diagrams : Application to metal extraction

ภาพที่ 4. ∆G0 – T diagram for sulphide formation.

For calculation of equilibrium p S2 and equilibrium p H2 / p H2S use points S and H respectively on the ∆G0 axis at o K

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ภาพที่ 5. ∆G0 – T diagram for sulphide formation.

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ภาพที่ 6. ∆G0 – T diagram for oxide formation.

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3. Slag forming temperature = ?

ภาพที่ 7. Phase diagram for the system SiO2 – 2Na2O.SiO2 . From F.C. Kracek, J. Phys. Chem., 34, 1588 (1930), and J. Am. Chem. Soc., 61, 2869 (1939).

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ภาพที่ 8. The liquidus plot for the SiO2- CaO – Na2O phase diagram.

(Donale R. Askeland, The Science and Engineering of Materials, third S.I Edition, CHAPMAN & HALL, P 468)

ภาพที่ 9. The Na2O-FeO-SiO2 system

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ภาพที่ 10. Liquidus surfaces and immiscibility region in the ternary system CaO – FeO – SiO2

( J.J. Moore, Chemical Metallurgy, Second edition, 1990, p. 164) Table 1 Suitable processes for various antimony ores or concentrates. Nature of the ore Antimony content, % Process Sulfide < 20 % volatilizing roasting Sulfide < 35 % smelting in shaft furnaces Sulfide > 60 % liquation and cyclone volatilizing Oxide < 30 % smelting in reverberatory furnaces and shaft furnaces Oxide < 50 % direct reduction Mixed sulfide and oxide - smelting in shaft furnaces Antimony is an element of main group V having atomic number 51 and atomic mass Mr = 121.75 Density Solid at 20 ºC Density Sb (s) = 6.688 g / cm3 : Liquid at 630.5 ºC Density Sb (l) = 6.55 g / cm3 Melting point of Sb (l) = 630.5 ºC Boiling point of Sb (v) 1587 ºC

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Alloy and Intermetallic Compounds Antimony Chlorides

Antimony trichloride , SbCl3 mp = 73 ºC , bp = 223 ºC , = 3.064 g / cm3 at 26 ºC is soft, Antimony pentachloride , SbCl5 mp = 4 ºC , bp = 140 ºC , = 2.34 g / cm3 at 20 ºC is a pale yellow fuming liquid of unpleasant odor. Antimony Sulfides Antimony trisulfide (stibnite) Sb2S3 , mp 550 °C , = 4.64 g / cm3 , has a black crystalline modification and an unstable red-orange modification . If both occur together, the mixture can be carmine or brownish red. Antimony trisulfide is soluble in alkalines and in concentrated, but not dilute, hydrochloric acid. It also goes into solution if it boiled in alkali carbonate solutions. However, it precipitates as a reddish-brown powder, of nondefinite oxygen content (kermesite), when the solution is cooled. Antimony Oxides

Antimony trioxide, Sb2O3 , has two modifications : senarmonite below 570 ºC , = 5.25 g / cm3 and valentinite (white antimony, antimony bloom) above 570 ºC , = 5.7 g / cm3 . The melting point is 656 ºC The commercial product is a white crystalline powder with a density of 5.2 – 5.8 g / cm3 . On heating, it becomes yellow but turns white again on cooling. Antimony trioxide dissolves in acids and alkalies. 3. เอกสารอ้างอิง

1. มนัส สถิรจินดา, โลหะนอกกลุ่มเหล็ก, ส านักพิมพ์แห่งจุฬาลงกรณ์มหาวิทยาลัย, พิมพ์ครั้งที่ 4. (2543) 2. Fathi Habashi, Handbook of extractive metallurgy, Volume II , 1997 3. Akira Yazawa and Narong Akkarapattanagoon, THERMODYNAMIC CONSIDERATION OF

ANTIMONY SMELTING