Specific Heats of Ammonium, Potassium, and Sodium Chloroiridates

The specific heats of ammonium, potassium, and sodium chloroiridate have been measured between 1.5°K and 20°K; anomalies of the $\lambda$-type were found at 2.15, 3.05, and 3.95°K for the ammonium, potassium, and sodium salts, respectively. These results confirm some conclusions drawn from magnetic susceptibility values. The difficulties involved in the correct analysis of this type of specific heat measurement are discussed.