EFFECT OF ADDITIVES ON CRYSTAL HABIT OF C ALCIUM HYPOCHLORITE DIHYDRATE

The crystal particles of calcium hypochlorite dihydrate (CHDH) are con ventionally formed in flat and square plate-like shape. This leads to such industrial problems as lower separability of particles from their mother liquor and their greater fragility. To reduce these unfavorabl e features of CHDH crystal particles, many kinds of compounds, both or ganic and inorganic chemicals, have been investigated in the light of favorable habit-modifying additives, where slurry mixtures of calcium hydroxide and sodium hydroxide were chlorinated in a batch system The marked effects on favorable habit modification of carboxylic acids and carbohydrates were observed. Among these compounds, polybasic carboxy lic acids and their salts were the most effective in regard to industr ial-scale processes. The role of these additives may be to supress cry stal growth in the direction of width (a- and b-axes) and to progress only in the direction of thickness (c-axis). A new type of CHDH crysta l particles, the shape of which is single and prismatic, could accordi ngly be obtained. These results may be explained by the fact that the additives were selectively adsorbed on the crystal. face growing in th e direction of the a, b-axes and increased the supersaturation by form ing chelate complexes with calcium ions.