Phase rule

1. LEAD –SILVER
SYSTEM
1. Lead-silver system is an example of two component
system.
2. Components are completely miscible with each other
and do not form any chemical compound.
3. Phase diagram of pb-Ag system show that composition
of Ag plotted on the x-axis corresponds to its
composition in the liquid melt.
Phase rule

2. --
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- - - -
.
Liquid melt B
Y
X
Z
961
Ag +melt
Solid Ag+eutectic
Solidpb
+
eutectic
C E
T
A
G
327
303
Pb +
melt
100%
0%
2.6%
Composition(wt%ag)
Temperature
C
o
F

3. Phase diagram of Pb-Ag system:
1.A&B show melting &freezing point of pure
Pb(327)&Ag(961) respectively
curves:
1.curveAE:Represent a freezing point of lead in
presence of liquid melt, ↔ solid pb
Liquid melt
2.curveBE:Represent the freezing point of Ag in
the presence of liquid melt ↔solidAg
Liquid melt
According to condenced phase rule:
F=C-P+1
F=2-2+1
F=1
Univariant

4. phases are co-exist ,the phases are solid pb,solid Ag,
liquid melt.
F=C-P+1=2-3+1=0 PointE is univariant
4.AREAS:
1.lineCED:area below CE consist of solid pb and
eutectic and area below ED consist of solid Ag and
eutectic
F=C-P+1 =2-2+1=1 so system is univariant
5.AREAS AEC &BED : In Area AEC pure
Pb is in equilibrium with liquid melt
In areaBED pureAg is in equilibrium with liquid melt
F=C-P+1=2-2+1=1 so sysytem is univariant