A semiquantitative analysis can now be applied relating
the growth velocity to these compositional effects. Since
the advance velocity of the font is dependent on the rate
of solute partitioning in the liquid, and hence to the lateral
flux of solute (= D
¶C/¶y),
we can write

where B_{1} is a
constant and D_{L} is taken as the
interdiffusion coefficient for both solutes. 
Using the relationship between DC and l given on the
previous page, and noting that DC_{0}
is proportional to DT_{0}
(see phase diagram) this leads to 

where B_{2} is
another constant, which is found in practice to have a typical value of about 0.1 K^{1}.
Since l_{min} is known (Click
here to see), this allows V to be evaluated
for given DT_{0}
and l. The animation, on the next page, shows how V changes as l is increased
from l_{min}