Thermodynamic properties of RbH2AsO4

Calorimetric and dielectric measurements have been made on Rb${\mathrm{H}}_2$As${\mathrm{O}}_4$ in the vicinity of the temperature of the ferroelectric transition 109.75 K. The transition is found to be first order with latent heat 255 ± 5 J/mole. The total transition entropy is found to be $0.50R$. The Curie constant is found to be 223 K. These results differ considerably from the predictions of the conventional static hydrogen-bond-occupation model, a fact which can be interpreted as demonstrating that dynamic effects are more important in Rb${\mathrm{H}}_2$ ${\mathrm{As}}_4$ than in K${\mathrm{H}}_2$As${\mathrm{O}}_4$.