  The specific heat, heat flux (DTA trace) and dielectric constant of KDP
ferroelectric crystal have been measured simultaneously for various electric
fields with a conduction calorimeter. The specific heat presents a strong
anomaly but these simultaneous measurements allow us to evaluate the latent
heat accurately. Latent heat decreases with field and the value of critical
electric field --that where latent heat disappears-- is estimated to be
(0.44\pm0.03) kV/cm. Incidentally, we have measured simultaneously the
dielectric permittivity which suggests that latent heat is developed as domains
are growing.
