A novel experimental method to detect the phase transition using a properly designed galvanic cell with a single crystal as an electrolyte and measuring of the electromotive force (emf) is presented. In order to validate this technique the measurements for the two single crystal ferroelectrics, (CH3NH3)(5)B2Cl11 and (CH3NH3)(5)Bi2Br11,in the vicinity of their ferroelectric-paraelectric phase transition of second order, at 307 and 311 K, respectively, were performed. The explanation of the temperature dependence of emf is based on the Volmer-Erdey-Gruz model. (C) 2003 Elsevier B.V. All rights reserved.