Accommodation of the K, NH₄ ions in RS-ARS mixed crystal system

Abstract

Crystallographic studies have been made on the mixed crystals of Rochelle salt and ammonium Rochelle salt (RS_1-X ARS _X ). The lattice constants a and b increase linearly with increasing x while c remains constant. The corresponding change of the crystal structure is also presented. The accommodation parameters α and β of the K and NH₄ ions on the two cation sites are determined as functions of x. The functions α and β have a crossing point around x=0.9 suggesting the difference between the phase transitions in RS and ARS.