Differential microcalorimeter for isothermal measurements of heat effects in two-phase systems and examples of its application

A differential heat-conducting double microcalorimeter intended for heat measurements at 300–700 K is described. Platinum resistance thermometers are applied as the heat-flux sensors. The calorimeter is a low-noise instrument with the baseline fluctuations ranging up to 0.02×10−6 V (5×10−6 W); it allows measurements of the heat effects with an error of 1%–1.5% at a recorded scale of about 1×10−2 J/cm2. The design features and the method of the heat-flux transformation to the electric signals, the calorimetric ampoules for measurements and for calibration and the calibrating device, the heat-balance equation and the equation for the temperature dependence of the calorimetric sensitivity, the results of the calibration and the verification of the calorimeter, and a number of illustrative examples of calorimetric measurements are presented. The calorimeters are applicable for studying solid–gas, solid–liquid, and liquid–gas interactions and thermophysical characteristics of solids and liquids.