ELECTRICAL STUDY OF THE PHASE-TRANSITION IN SOME HYDROGEN OXALATES

The paper deals with accurate measurements of the electrical resistivi ty rho and the dielectric constant epsilon as functions of temperature 300 < T < 450 K for sodium hydrogen oxalate monohydrate NaHC2O4 . H2O (I) and potassium hydrogen oxalate KHC2O4 (II). The data obtained rev ealed the existence of possible structural phase transitions at 342 an d 325 K for I and II respectively. Thermogravimetric analyses (TGA) of the two compounds have been performed. The thermograms confirmed the absence of any actual loss in weight in the transition temperature reg ions. The data are interpreted on the basis of crystal transformation and the arrangement of the molecules in the unit cell including the hy drogen bonding system.