1.
V R S E C
E N G I N E E R I N G C H E M I S T R Y
S A R V A N I
R O L L N O : 3 1

2.
T O P I C
• TO KNOW THE REASON FOR DEGREE OF FREEDOM TO
BE {F=1}ONE AT AREA UNDER THE CURVE OF A SILVER -
LEAD SYSTEM.
PURE SILVER PURE LEAD SILVER- LEAD
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3.
I N T R O D U C T I O N
Sample
Footer
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Pure silver melts at 327 C.
Addition of silver lowers it's melting point.
Pure silver melts at 961 C.
Addition of lead lowers it's melting point.
Along AO solid silver and molten solution of
lead and silver is present.
Along BO solid lead and molten solution
of lead and silver is present.
System is monvariant among AO&BO.
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4.
 B I S T H E E U T E C T I C P O I N T
W H E R E T H R E E P H A S E S
S O L I D L E A D , S O L I D
S I L V E R A N D B O T H T H E I R
L I Q U I D F O R M S I S
P R E S E N T .
 T H E T E M P E R A T U R E O F
E U T E C T I C P O I N T I S 3 0 3 C .
 C O M P O S I T I O N O F S I L V E R
P H A S E I S 2 . 6 % S I L V E R .
 T H E P H A S E D I A G R A M O F
L E A D - S I L V E R H A S
S P E C I A L S I G N I F I C A N C E I N
C O N N E C T I O N W I T H T H E
" D E R I V A T I O N O F L E A D ' .
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5.
 The argentiferous lead consisting of a very small
percentage of silver is first heated to a
temperature well above its melting point .
 So, system only consists of the liquid phase
represented by point a'' in the figure.
 It is then allowed to cool.
 As soon as the point a' is reached, lead will began
to crystallize and solution
will contain relatively increasing amount of Ag.
 Further will shift line a'a along a'B.
 Lead continues to separate out and is constantly
removed from the melted solution.
M O N D A Y , F E B R U A R Y 1 , 2 0 X X 5

6.
 The melted liquid will constantly become richer
and richer in silver until point a is reached, where
the % of Ag rises to 2.6%
 Thus, the original argentiferous lead which might
have contained 0.1% or less of silver can now
contain upto 2.6% of Ag.
 This process is known as "Pattinson's
Process".
 In area ABD solid lead and melt are in equilibrium.
Therefore, two phases exist in this area
which means system is monovariant in
this region.
 Which means as we decrease the temperature from
a' to a , the corresponding composition of silver
will increase , due to pattinson's process.
M O N D A Y , F E B R U A R Y 1 , 2 0 X X 6

7.
 Therefore, as we decrease the temperature from
a' to a the corresponding composition of silver
will increase , due to pattinson's process.
 Which means if (b) is the temperature at any
point a(b,b') in area ADB. The corresponding
composition (b') can be determined by drawing
a horizontal line from this point which is called a
Tie line and from the point of intersection of Tie
line and AB curve draw a vertical line ,this line
meets the composition axis and that
composition is the corresponding composition
to the temperature variable (b).
It means temperature Is the only variable that to
be find for given point which is at the area ADB
and the corresponding composition can be
determined by the above process. Since to
determine the system at given point we have to
find temperature only, therefore the degree of
freedom is 1 at area ADB.
M O N D A Y , F E B R U A R Y 1 , 2 0 X X 7

8.
S U M M A R Y
• Since , to determine the system at give
point which is at the area ADB we have to
find temperature only and the
corresponding composition can be
determine by above process. Therefore,
The degree of freedom is one.{F=1}.
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9.
T H A N K Y O U
• Sai Sarvani
• ECE-2
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