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5.5 Phase diagrams of three-component systems ---ternary phase diagrams. ( ) T or ( ) P. ( ) T,P. Equilateral triangle coordinates. The Gibbs Triangle. O, content point. Mass fraction. a '. Content of A in the system. b '. Content of B in the system. c '.
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5.5 Phase diagrams of three-component systems ---ternary phase diagrams ( )T or ( )P ( )T,P
Equilateral triangle coordinates • The Gibbs Triangle
O, content point Mass fraction a' Content of A in the system b' Content of B in the system c' Content of A in the system
5.5.1 Composition characters for equilateral triangle coordinates d,e,f the mass fractions of A are equal Points on AD line, On line AD, D’ is closer to A than D, the mass fraction of A in D’ is more than that in D
D+E O Tie line The level rule for three-component systems O must be on the line DE
S b b S The mass fraction of A decrease, mA of A is separated from S (Φ=2, L+A) mA of A is added into the system
D + E + F H Centre-of-gravity rule of three-components system
5.5.2 Partly miscible three-components liquid system O: isothermal consolute point aob: binoal curve a1-a4, b1-b4, a1-b1, a2-b2,a3-b3….. conjugate solution
B: H2O:Butanol:CH3COOH=30%:30%:40%=A+C A: 43%:22%:35% C: 14%:63%:23% A:C = 23:18
T - x1,x2 Single phase Two phase There are one couple of partly miscible components
Single phase Two-phase Two couples of partly miscible components Vinyl cyanide(A) water(B) ethanol(C)
Single phase L1 Two-phase Single phase L2
Single phase Two-phase There are three couples of partly miscible components Vinyl cyanide(A) water(B) ether(C)
Two-phase Φ=3 D,E, F Φ=1
Φ=1 L Φ=2 B(s), L Φ=2 C(s), L Φ=3, B(s), C(s), F 5.5.3 Ternary water-salts systems Φ=3, the saturation solution of B and C
How to get pure B from mixtures of B and C Q-----R(L+B)
Effect of temperature on phase diagram T=298K T=373K
Purification of salt X(KNO3+NaNO3)…..D(298K)+KNO3…D(373K)…
5.5.4 Three-component system containing threebinary eutectic points
Φ=1, L Φ=2, L+Bi Φ=2, L+Pb Φ=2, L+Sn Pb-Sn-Bi trinary system Triple point Bi/Sn, Sn/Pb, Pb/Bi
Φ=3, L+Pb(S)+Sn(S) Φ=3, L+Bi(S)+Sn(S) Eutectic T decrease E4, L+Bi(S)+Sn(S)+Pb(S)
T decrease: A(Φ=1,L)… L+Bi(S) L+Bi(S)+Sn(S) L+Bi(S)+Sn(S)+Pb(S) Φ=4, f=0
Homework • Y: P188 39 • Review the whole chapter