<s>
In	O
chemistry	O
,	O
the	O
lever	B-Application
rule	I-Application
is	O
a	O
formula	O
used	O
to	O
determine	O
the	O
mole	O
fraction	O
(	O
xi	O
)	O
or	O
the	O
mass	O
fraction	O
(	O
wi	O
)	O
of	O
each	O
phase	O
of	O
a	O
binary	O
equilibrium	O
phase	B-Application
diagram	I-Application
.	O
</s>
<s>
Suppose	O
an	O
alloy	B-Application
at	O
an	O
equilibrium	O
temperature	O
T	O
consists	O
of	O
mass	O
fraction	O
of	O
element	O
B	O
.	O
</s>
<s>
Suppose	O
also	O
that	O
at	O
temperature	O
T	O
the	O
alloy	B-Application
consists	O
of	O
two	O
phases	O
,	O
α	O
and	O
β	O
,	O
for	O
which	O
the	O
α	O
consists	O
of	O
,	O
and	O
β	O
consists	O
of	O
.	O
</s>
<s>
Let	O
the	O
mass	O
of	O
the	O
α	O
phase	O
in	O
the	O
alloy	B-Application
be	O
so	O
that	O
the	O
mass	O
of	O
the	O
β	O
phase	O
is	O
,	O
where	O
is	O
the	O
total	O
mass	O
of	O
the	O
alloy	B-Application
.	O
</s>
<s>
Together	O
these	O
two	O
quantities	O
sum	O
to	O
the	O
total	O
mass	O
of	O
element	O
B	O
in	O
the	O
alloy	B-Application
,	O
which	O
is	O
given	O
by	O
.	O
</s>
<s>
This	O
final	O
fraction	O
is	O
the	O
mass	O
fraction	O
of	O
the	O
α	O
phase	O
in	O
the	O
alloy	B-Application
.	O
</s>
<s>
Before	O
any	O
calculations	O
can	O
be	O
made	O
,	O
a	O
tie	O
line	O
is	O
drawn	O
on	O
the	O
phase	B-Application
diagram	I-Application
to	O
determine	O
the	O
mass	O
fraction	O
of	O
each	O
element	O
;	O
on	O
the	O
phase	B-Application
diagram	I-Application
to	O
the	O
right	O
it	O
is	O
line	O
segment	O
LS	O
.	O
</s>
<s>
The	O
mass	O
fraction	O
of	O
solid	O
and	O
liquid	O
can	O
then	O
be	O
calculated	O
using	O
the	O
following	O
lever	B-Application
rule	I-Application
equations	O
:	O
</s>
<s>
The	O
same	O
equations	O
can	O
be	O
used	O
to	O
find	O
the	O
mass	O
fraction	O
of	O
alloy	B-Application
in	O
each	O
of	O
the	O
phases	O
,	O
i.e.	O
</s>
