Automatically Controlled Isothermal-Adiabatic Calorimeter

Abstract

A calorimeter has been constructed to measure specific heats, heats of solution, heats of reaction, and other thermal changes in liquid systems. For endothermic processes the calorimeter jacket is maintained at constant temperature while heat is supplied to the reaction chamber at a rate sufficient to keep the temperature of chamber and jacket equal. During exothermic processes, including specific heat determinations, the jacket temperature is raised at a rate sufficient to maintain temperature equality between chamber and jacket. The recording and controlling of temperature in the calorimeter are continuous and largely automatic. The heat input to the calorimeter is also automatically recorded by means of an integrating watt-second meter. Experimental specific heat data are presented to illustrate the performance of the calorimeter. The results of specific heat measurements on toluene and water agree with previously reported values within 1% over a temperature range from approximately 20–40°C. The temperature difference between jacket and reaction chamber during these experiments was automatically controlled within 0.05°C and no oscillation of the control was apparent.