The Residual Entropy of the Equimolal KCl-KBr Solid Solution in Relation to Wasast Jerna's Theory of Alkali Halide Solid Solutions

Using the DELTA C/sub p/'s for the temperature range 12 to 300 deg K, the residual entropy was computed to be 1.39 plus or minus 0.04 eu or 1.37 plus or minus 0.04 eu. The values, which are very close to the entropy of random mixing, strongly suggest that there is a negligible amount of local order in the anion sublattice. The results are at variance with Wasastjerna's theory which predicts a residual entropy of 1.29 plus or minus 0.01 eu and an appreciable degree of order. The results show that when KCl/sub 0.5/Br/sub 0.5/ is formed from the component salts, there is an increase in vibrational entropy of 0.11 eu. (P.C.H.)