05-11E

Influence of the longitudinal electric field on the static and dynamic dielectric, elastic, piezoelectric characteristics of Rochelle salt, as well as sound attenuation, is studied within the two-sublattice Mitsui model with taking into account the piezoelectric coupling. A satisfactory agreement with experimental data is obtained for the field effect on the static dielectric permittivity near the lower Curie temperature. At the upper Curie temperature an effective field should be used in calculations to describe the experiment. Possible role of space-charge build-up is discussed in screening of the external field at high temperatures.