Sodium gluconate was used as a model compound in the poisoning of gibbsite precipitation from caustic aluminate solutions. Experiments were performed to examine the relationship of seed surface area and sodium gluconate dose to the Induction period and precipitation rate, The results suggest that growth rate suppression is a surface process and that it results from a reduction in the available surface area and not from a change in surface activity. The mechanism of poisoning was inferred from SEM micrographs, and by using measurements of the growth rate and induction period for both poisoned and unpoisoned gibbsite precipitations.