Transitions and Thermal Anomalies in Silver Oxide

In 1937 Pitzer and Smith! measured the heat capacity of silver oxide (Ag 20 ) over the range 13-300 oK and found anomalously high values in the range 20-40 Hysteresis effects were noted with respect to the excess heat capacity. The entropy associated with the anomaly was approximately 0·5 cal °C-l molerl. Kobayashimeasured the heat capacity of silver oxide at higher temperatures and observed a heat evolution of approximately 315 cal/mole in the range 100-200°C the first time that a given sample was heated through this region. Repeat heating gave no further heat evolution. In each case the sample was precipitated from aqueous solution and was dried at temperatures not exceeding 115°C. The present investigation was designed to yield further information about these peculiar effects.