Habit Changes of Sodium Bromate Crystals Grown from Gel Media

Agarose, gelatin, and silica gel media have been surveyed as appropriate matrixes for the crystal growth of sodium bromate (NaBrO 3 ). From pure aqueous solution, NaBrO 3 crystallizes with a characteristic tetrahedral habit. We have demonstrated that a greater variety of habits (e.g., cubic, tetrahedral, polyhedral, and dendritic) can be reliably obtained from the growth in these gel media by controlling the solute concentration and the gel density. Agarose and silica matrixes suppress the nucleation as the gel density increases, while increasing gelatin concentrations seem to enhance crystal nucleation rates. These observations support the general hypothesis that the gel media influences the relative growth rates by controlling the solute nucleation and diffusion; however, little can be concluded about the possible chemical interaction between the polymeric backbone and the solute.