FERROELECTRIC TEMPERATURE SENSORS FOR THERMOMETRIC TITRATIONS AND ENTHALPIMETRIC ANALYSIS

The capabilities of commercially available barium titanate ferroelectric ceramics with switching points of 25 and 0-degrees-C were tested for use in thermometric titrations. Temperature (T) versus resistance (R) data taken from 24 to 26-degrees-C for seven ferroelectrics and from -1 to +1-degrees-C for three others were fitted to an exponential equation of the form R = Aexp(CT), where A is a scaling factor and C is the temperature coefficient of resistance. A ferroelectric sensor (FES) was wired in a Wheatstone bridge in place of the thermistor customarily used in conventional instrumentation. Calculations substantiated that the bridge imbalance potential response approximated linearity within any 1-degrees-C interval, provided that the bridge was balanced in the middle of the span. The response of the FES bridge showed a fourfold enhancement for a given temperature change compared with the thermistor bridge and a concomitant reduction in baseline noise. Analytical capabilities are illustrated by thermometric redox titrations in the concentration range between 3 x 10(-5) and 2 x 10(-3) M.