Specific heat of sodium nitrate and silver nitrate by medium high temperature adiabatic calorimetry

Abstract

    A relatively simple adiabatic calorimeter for use in the temperature range 50-350° was constructed and used to measure the specific heat of sodium nitrate from 150 to 300° and silver nitrate from 70 to 250°. Each salt undergoes a solid-solid and a solid-liquid transformation in these temperature ranges. The Cp values for sodium nitrate agreed within the calculated experimental error of ±0.2% with those of Sokolov and Shmidt1 but the silver nitrate showed a large discrepancy with those of Janz and Kelly2 obtained by drop calorimetry for the 160-210° region, where thermal hysteresis may have occurred in the drop calorimetric technique. The heat of transformation for the solid-solid transition in silver nitrate at 159.4° was found to be 561±4 cal mole-1.