AbstractA study has been made of the sedimentation behaviour, sedimentation volume and bulk density of the precipitates obtained by seeding sodium aluminate solutions with hydrargillite in presence of glucose, sugar and starch.With glucose and sugar, sedimentation is free and sedimentation volume small, but with starch, aggregated sedimentation occurs and sedimentation volume is large.To explain the results, it is postulated that glucose and sugar combine with Al3+or Al(OH)3molecules and that starch is chemisorbed on the particles of seed material.