Results of a systematic study of growth habit, dislocation densities, and microhardness of the NaCIO,-NaBrO, mixed crystals are presented. A drastic change in habit of NaBrO, for small additions of NaClO, was observed, The composition dependence of dislocation density for this system is found t o be highly non-linear. A non-linear composition dcpendence of microhardness, with positive deviations from linearity was also observed. This increase in hardness is correlatcd with the enhanced dislocation density in the mixed crystal.