HEAT CAPACITY OF SILVER IODIDE .I. EXPERIMENTS ON ANNEALED SAMPLES

The heat capacity of silver iodide has been measured over the range 50°-400°C using an adiabatic calorimeter, the design of which is discussed. Below about 150°C the behavior of the βform is normal and it transforms to the a form at this temperature with latent heat 1.5 ±0.1 kcal/mole. If the sample is stoichiometric, the a form has an anomalously high specific heat C, ranging from 18 cal/mole-°C at 150°C to 26 cal/mole- °C at 400°C. If the sample deviates from stoichiometry by as little as 1 mole % in either direction, then its specific heat is normal at 12 cal/mole- °C from 150° to 400°C. An interpretation of these results in terms of lattice disorder is suggested.