Analysis of second order phase transition

(2.28)

or,

(2.29)

From the definition of isothermal compressibility,

(2.30)

Again, following the definition of volume expansivity,

(2.31)

For reversible isothermal isobaric process

s(i) = s(f) [at p, T]	(2.32)
⇒ s(i) + ds(i) = s(f) + ds(f) [at (p+dp, T+dt)]	(2.33)
⇒ Tds(i) = Tds(f)	(2.34)
	(2.35)

[2nd T-dS relation]

(2.36)

or,

(2.37)

As there is no change in volume

v(i) = v(f) [at (p, T)]

(2.38)

Further, at point [p+dp, T+dT],

v(i) + dv(i) = v(f) +dv(f)	(2.39)
⇒ dv(i) = dv(f)
	(2.40)