Atomic Heat of Indium below 20°K

A calorimetric technique in which a carbon-composition resistor serves simultaneously as both heater and thermometer has been developed and is described briefly. Using this technique, the atomic heat of indium has been measured in the normal state from 1. 7^ to 21. 3^ and in the superconducting state from 1. 8^ to 3. 396^, the transition temperature in zero magnetic field. Tables of smoothed values are given. A method of deducing the separate lattice and electronic contributions to the heat capacities, based on several empirically and/or theoretically tenable assumptions, has been developed and is described in some detail. This method of analysis, when applied to the indium data, led to the conclusion that a cubic analytic form for the critical magnetic field equation would allow conclusions consistent with all the assumptions but that the more commonly used parabolic form would not. Numerical values are given for the constants involved. The temperature dependence of the Debye characteristic temperature of the indium lattice over the entire range of measurement is shown to follow the theoretically expected behavior.