
The Clapeyron Equation 225
the universal (meaning the same value for all materials) of 1.43. In actuality, the
value differs from material to material. This should not be of concern as the BCS
prediction involves some material dependent assumptions. The BCS value has been
shown to be in excellent agreement with the high precision experimental values ob-
tained by Phillips for Aluminium.
The general trend is of course seen in all materials. For Aluminium the graph de-
picting the variation of the specific heats with temperature was shown in chapter 10.
One sees that as the temperature is lowered from T
c
, a temperature is reached where
the two specific