THE BEHAVIOR OF COMPLEX HEAT-CAPACITY NEAR THE FIRST-ORDER PHASE-TRANSITION

We have measured complex heat capacity in potassium dihydrogen phospha te (KH2PO4, KDP), thiourea (SC(NH4)(2), TU), ammonium sulfate ((NH4)(2 )SO4, AS) and triglycine sulfate ((NH2CH2COOH)(3)H2SO4, TGS) using an ac calorimetry. The crystals, KDP, TU and AS, have been known to under go the first order phase transition. They showed the anomaly in the im aginary part of the complex heat capacity in narrow temperature region around the transition points. On the other hand, TGS which undergoes the second order phase transition showed no anomaly in the imaginary p art at the phase transition point. The imaginary part of the complex h eat capacity may reflect the dynamic behavior of the two-phase coexist ence legion.