A Low Temperature Particle Size Effect on the Heat Capacity of Sodium Chloride

An effect of particle size upon the heat capacity of sodium chloride has been found in the temperature range 9° to 21°K. The experiments were done with three NaCl samples of specific surfaces between 38 and 59 sq. meters per gm. The observed effect has the temperature dependence predicted by theory but its magnitude is three to four times larger than expected. It is unlikely that adsorbed gases have made any significant contribution in the experiments. The accuracy with which the specific heat and surface area differences have been determined is not high enough to show definitely whether or not the surface specific heat is an extensive property of the surface.